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Subject: Coastal Awareness/A Resource Guide for Teachers
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COASTAL AWARENESS
A resource guide for teachers
by Gareth Penn, Librarian
Southwest Fisheries Science Center
Tiburon Laboratory
National Marine Fisheries Service
National Oceanic and Atmospheric Administration (NOAA)
Department of Commerce
C O N T E N T S
l) The Coasts (teacher introduction):
2) Suggested activities
for elementary school children
for middle school students
for high school students
3) Teachers' guides
THE COASTS
The shore lines of the United States--where the land meets the
sea--measure more than 140,000 km (88,000 mi). If straightened
they would stretch more than three times around the equator of
the earth. Our nation's coasts include the sea shores of the
continental United States, Alaska, Hawaii, four Atlantic island
groups, and nine Pacific island groups. The Great Lakes and all
the sounds, bays, creeks, and rivers washed by tidal waters are
also included.
What are the special characteristics that define a coast, that
make coasts valuable and vulnerable to human activities? Why and
how should we protect this vital area of our nation?
The coast is a place of untold natural resources. It is a place
to which one can escape, a place to play, to be serene, to be
inspired. In near-shore ocean waters fish can be caught for
sport or for food, and the coast itself can be a significant
agricultural area. Each coast has a different history, different
pressures, and different problems. Yet, in a physical sense,
many of their problems may be similar.
Pollution is one such common problem. The Great Lakes are the
largest fresh water resource in the world. Pollution of these
lakes, which began in the 1800's, has continued steadily: forests
were cleared, disrupting the natural balance, and increases in
population, industry, commerce, and recreation continue to
encroach.
The development that has plagued the Great Lakes for a century is
only just beginning in Alaska. But changes come quickly where
the margin for life is narrow, and in the frigid waters of the
Bering Sea there is little room for error. The Bering Sea is
literally the "fish basket" of the northern hemisphere. It
supports a surprising variety of life, including one of the
largest marine mammal populations of the world, what may well be
the world's largest clam population, one of the world's largest
salmon runs, some of the largest bird populations per unit area,
the world's largest eel grass beds,and unusually high numbers of
bottom-dwelling fish.
Any coast consists of two primary elements: the water and the
land. The area where these meet--the coast--has unique
characteristics due to periodic inundation and continual changes
in salinity. The biological composition of the coasts is often
in delicate balance.
The science student concerned with the coastal zone will want to
investigate both the water and the land as well as their
interaction. Coastal waters are generally rich in nutrients that
have been carried from the land by the rivers and streams. Near-
shore coastal waters are particularly productive. These waters
are a basic resource; they are affected by a variety of factors--
the forces that cause tides, the winds that augment the waves,
and the activities of human beings, including exploration and
exploitation.
THE SHORE
There can be other definitions, but for our study, we define the
shore as the narrow strip between the high-water and low-water
marks of spring tides. Thus, there are regular, yet extremely
variable local environments. First,the sea covers and uncovers
the coastal area twice daily. Temperature ranges may be great
within a single day. The salt concentration may vary greatly.
The extent to which this intertidal zone is uncovered at low tide
depends on the sharpness of its slope which in turn depends on a
variety of factors including the nature of the land, its
configuration, and the action of the tides, currents, and rivers.
The three basic types of shore are rock, sand, and mud. They are
often mixed together. The waves have the greatest influence on
molding the shore as they break against the land, washing away
loose materials, eating into hard rocky coasts, and sometimes
forming an abrasion platform at the base of high cliffs.
Powerful crosscurrents deposit banks of sand that have been
formed by the disintegrating rocks. Mud flats occur at the
mouths of rivers or in sheltered creeks and inlets where the
sediment brought from the land is deposited. Ice, weather, and
the elements all work to help form the shore.
Plants and animals are other factors in coast building. Plants
may act to bind sand and mud together into dry land. Encrusting
animals may serve to protect rocks or to destroy them. Light
plays a significant role in this environment, affecting growth of
vegetation which, in turn, affects animal growth and survival.
Estuaries, too, affect the shore environment. Dilution by fresh
water will occur at the mouths of rivers, while increased
concentrations of salt will occur as a result of evaporation
during the summer.
OCEAN IN MOTION: WIND, WAVES, CURRENTS AND TIDES
Wind generates waves. The wind, blowing irregularly, causes
significant pressure differences that deform the water's surface,
creating wave crests of many heights. The wind then pushes
against these crests, supplying energy to the waves as they grow
and become more regular in weight and length. Wave growth
depends on four factors: wind velocity, distance of open water
over which the wind has blown (called the "fetch"), duration of
the wind, and the state of the sea (waves that were present when
the wind started blowing).
The wind also plays a part in coast formation. In addition to
their indirect effect through action on the water, powerful winds
can cut into rock, tearing away gravel that slides to the water's
edge. They may also pick up grains of sand and pile them into
dunes.
WAVES
Waves are the sculptors of the coasts. Forceful or gentle, loud
or
lulling, they combine two distinct types of motion. One is the
circular motion of the water molecules within the wave, the up
and down motion of the droplets. The other is the advancing
movement. The actual water molecules have no horizontal motion as
the wave advances through the ocean.
Waves are described by their height, length, velocity, and
period. Period is the number of seconds it takes for two
successive crests to pass a stationary point. Height is the
vertical distance from the crest (high point) to the trough (low
point) and length is the distance from one crest to the next.
Period, length and wind velocity are interrelated. Wave height,
however, is not related to these factors. The height of a wave
in meters is usually about one-tenth the wind's speed in
kilometers per hour.
As they move away from the winds that started them, waves tend to
expand laterally and to become lower, more rounded, and more
symmetrical. They then move in groups of similar size, called
"wave trains;" the individual waves are called "swells." Once a
wave train has formed, it will continue to travel over the sea
until it either breaks on a shore or is flattened by opposing
winds or wave systems. (In these materials, we will be concerned
in particular with the breakers because of their effect on the
coastal area.) As a swell approaches the beach, the topography
of the ocean bottom takes effect. Depending on wave length and
bottom contour, waves may break at depths from one-half to three
times their height.
The bottom slope is the key determinant not only of the depth at
which a wave breaks but also of the manner in which it breaks. A
steep bottom results in a wave that retains all its energy until
the last possible moment, when the crest peaks up suddenly and
plunges violently forward into the trough. As the crest folds
over it becomes concave, creating a "tube" or tunnel of air on
the shoreward face. These are known as "plunging waves." Hollow
plunging waves are the most challenging for surfers because their
steepness makes for a very fast ride and it is often possible to
crouch under the falling crest--to be "locked in the tube." The
plunging waves that curl over the dangerously shallow coral reefs
of Hawaii's "Banzai Pipeline" are a famous example of this
kind of wave .
A gradually shoaling bottom results in a wave that releases its
energy more slowly. When a crest finally becomes unstable, it
rolls down or spills into the trough and the wave face remains
gently sloped. It is these "spilling waves" that display white
water at the crest.
Irregularities in the ocean bottom tend to make waves still
rather than plunge. Even long-period waves break as spillers on
a flat sloped beach, but any suddenly shallow spots will cause
most waves to "suck out" and plunge, regardless of their periods.
Most surf zones are in a state of constant change.
Wind is not the only generator of waves. Earthquakes on the land
or under the sea may cause a drastically low tide that is
followed by destructive giant waves (sometimes called tsunamis)
hurling relentlessly against the shore.
TIDES
The tides are important in determining the character or the
coast. Tides result from the effect on the waters of the
gravitational attraction among the sun, moon, and earth.
The masses of the earth and the moon exert a gravitational pull
on each other that affects every particle on earth, including
water. The force is greatest on those particles nearest the moon,
but it is much smaller than the earth's force. Although the
force required to pull water vertically off the earth would be
great, a much weaker force can pull the water horizontally, in
effect sliding it across the face of the earth. Water is drawn
toward the point directly "below" the moon, and high tides occur
when water piles up in this way. Identical forces cause
comparable effects on the side of the earth farthest from the
moon. In both cases, the water moving into the high tide is
being drawn away from another region of the earth. Thus, there
are high tides on opposite sides of the earth on a line directly
extended between the moon and the earth, and there are low tides
midway between the two high tides, in the area from which water
for the high tides was drawn.
Due to the changing position of the moon, a tidal pulse sweeps
around the surface of the earth, causing secondary waves that
move across the oceans. In mid-ocean the secondary waves may be
only as high as 1 meter, but where the water is shallow these sea
waves become much higher. The increased height is the result of
a tremendous friction force which slows the wave down. When such
tidal pulses move through narrow channels, the water is "bottled
up." The highest tides occur in these narrow channels; a well
known example of such tides is the Bay of Fundy between Nova
Scotia and New Brunswick in Canada.
Because the earth and the moon move orbitally (the earth around
the sun and the moon around the earth), both the timing of the
tides and their range vary in response to these gravitational
forces. The greatest difference between high-water and low-water
is found at the "spring" tide, when sun and moon exert their
force in the same direction during the new or full moon. The
highest tide is during the new moon when the moon is in line with
the sun, with the earth between them, and the gravitational pull
is all in the same direction. The smallest, or "neap" tide
occurs when the high-water mark is at its lowest, and the low-
water mark is at its highest.
CURRENTS
The forces that keep the great mass of ocean water in motion are
many and varied; important among them are the heat of the sun and
the rotation of the earth.
As the sun warms the surface water at the equator, the water
expands and raises the surface just enough to cause a gentle
slope. Water at the equator therefore runs downhill to the poles.
The heavier polar cold water sinks and spreads slowly along the
bottom of the ocean toward the equator. This interchange of warm
equatorial waters with cold polar waters is complicated by a
variety of additional forces. For example, the earth's motion
toward the east affects the water on the surface of the earth
both directly,by causing waves to pile up, and indirectly, by
creating winds. The spin of the earth also results in the
Coriolis effect-- the tendency of water (or any moving object) to
turn slightly to the right in the northern hemisphere and
slightly to the left in the southern. Consider the Atlantic
Ocean waters in the region just north of the equator, where the
Gulf Stream originates. Heated by the tropical sun, the salt
concentration of the water steadily increases as a result of
constant evaporation. Meanwhile, the trade winds (a consequence
of the earth's spin) continually blow over the warm, salty
waters, pushing the surface waters in a westerly direction toward
the north coast or the South American continent. The waters then
move toward the Caribbean Sea and on, northwesterly, into the
Gulf of Mexico where they pile up, raising the surface level.
Following its natural tendency to seek equilibrium, the water
drops into the Florida Straits, the only possible egress. From
there the Gulf Stream runs northward along the coast.
As the Gulf Stream moves north it trends increasingly toward the
right (to the east) because of the Coriolis effect. By the time
it reaches 40 degrees North latitude, it is flowing due east
across the Atlantic, has lost considerable speed, and has
widened; it has also cooled down. Currents similar to the Gulf
Stream move the waters of the Pacific, Indian, and other oceans.
Other factors affecting water currents include ice floes moving
from polar seas on the cold currents. As the ice moves southward
it cools the water. Since cool water is heavier than warm water,
it sinks and is then replaced by warm water near the surface.
The most economically important currents are upwellings of cold
bottom water. This vertical motion brings to the surface an
unusually heavy concentration of nutrients. When offshore winds
drive surface waters out to sea, they are replaced by the
upwelling nutrient-rich deep water. Mineral-rich waters from the
land add to the nutrient supply. This upwelling supports a rich
growth of phytoplankton, the start of a complex food chain, and
makes possible intensive commercial fisheries such as those off
the coast of Peru and the Grand Bank off the coast of
Newfoundland, Canada.
THE SANDY BEACH
Of all the coastal elements, sandy beaches probably have the
highest recreational value. These beaches vary considerably from
one part of our country to another. They have different sand,
different waves and winds, and different dunes and other inland
formations. They are composed of grains as diverse as the black
lava sands of Hawaii, the golden sands of Lake Michigan, the
white coral sands of Florida, and the seemingly endless sandy
expanse from San Diego to Los Angeles. Florida's popularity as a
vacation land almost certainly is in large part due to the fact
that so much of its coastline is sandy ocean beach.
Although sandy beaches differ in many ways, they also share
certain characteristics. Waves moving on shore break on the
longshore bar and roll up onto the beach. Each wave moves sand
from the longshore bar and slowly, almost imperceptibly, a longer
more sloping beach is created. Then, as the season changes,
blustering winter winds and heavy seas begin to attack the
sloping summer beach. The winter waves are higher, steeper, and
closer together than those of summer. Sometimes sand is carried
away from the berm and even from the dunes or other land areas
behind the berm. This pounding winter wave action generally
deposits some sand on the berm, but it carries away far more sand
and deposits it in longshore bars, setting the scene for another
yearly cycle.
The texture of the sand plays a role in the kind of beach that
will be built, because the slope of the beach relates directly to
the particle size of the deposited material. The coarser the
particles, the more the waves sink into the beach, depositing
their load of sand. Since coarse sand does not pack down and is
easily moved around, steep beaches result. When the particles
are finer the sand packs down more tightly; the waves do not sink
in, and their action leaves a harder, smoother, and gentler
slope.
Waves and wind thus work endlessly building, shaping, and
reshaping beaches. Large particles grind against each other,
creating progressively smaller fragments. The largest of these
are dropped on the beach and smaller less dense particles are
carried out to be deposited in quieter, deeper regions of the
ocean.
Regardless of the season, the markings on sandy beaches are
intriguing. The graceful swash marks left by an ebbing morning
tide are composed mostly of detritus -- fragments of once living
things -- that are not only a source of food for many beach
inhabitants but are also a treasure trove for human beach
explorers. Parallel ridges and troughs, called ripple marks, are
often seen on sandy beaches: if the ripple marks are in dry sand
they were caused by wind, but if they are lower down on the beach
they were caused by moving water. Whether caused by wind or
water, the process of ripple formation is essentially the same.
When wind or water moving over the sandy surface meets an
obstacle in the surface it turns downward, excavating a trough.
The sand thus thrown up creates another obstacle and the wind or
water then creates another trough.
Ocean beaches are moving, active places that gain and lose sand
continuously. Beach sand is transported by waves, wind, and wave
currents in three kinds of movements: offshore, on-shore, and
longshore. When put into suspension by wave action, sand can move
laterally along the shore in long-shore currents at the same time
that it is being moved offshore and returned onshore. Sand
movement along the shore occurs within relatively distinct
sections of the coast, sometimes called "littoral cells." The
boundaries of a cell extend from the place where sand is
introduced onto the shoreline (generally by a stream) to the
place where it is swept out to the sea. Where beach indentations
in the coast are isolated from the general sand movement of the
"cell" within these areas, shore erosion and onshore currents can
supply and to smaller "pocket" beaches.
Human activity often has had disastrous effects on the natural
supply of sand to beaches. Reducing high water runoff from
rivers seriously reduces the sand supply available since it
reduces the erosion along river banks. Improper construction of
groins, jetties, and breakwaters can change the distribution of
sand by longshore currents, causing excessive sand build-up in
some places and sand loss in others. The biological production
of shorelines is also affected when normal water circulation
patterns are changed. Careful study is needed before any major
beach front modifications are undertaken.
The long stretches of sun-baked sand and the breaking waves that
delight vacationers are also what make sand beaches among the
most barren of coastal environments. Because of its shifting
nature, the sand offers a poor substrate for anchoring plants.
Thus, beaches essentially lack the producers in the food chain
and the few animal residents of the sand must depend on small
wave-borne particles for food. Usually such residents are tiny
crustaceans or mollusks which live in the moist upper surface of
the beach close to the water line and filter the food from the
retreating waves. Other crustaceans and sand hoppers inhabit the
upper beach, feeding at night along the tide line. Each sunrise
they dig new burrows often peppering the sand with their holes.
Sand beaches are superb places for bird watching. Some
birds are full-fledged swimmers and obtain their food from the
ocean and the near-shore ocean bottom. Others parade incessantly
up and down the beach at the water's edge in search of food. The
specific kinds of bird inhabitants vary from one part of the
country to another, but certain general kinds can be recognized.
Medium-sized birds that are flying across the surface of the
water or riding on it are likely to be gulls, terns, or
cormorants. The cormorant is a dark bird that dives and
disappears for a considerable time
while swimming in search of food. Gulls and terns do not swim
under water. Terns can be seen flying over the water and diving
into it to catch small fish, but gulls are less likely to dive
for their food. Gulls, either singly or in groups, can also be
seen on the beach itself in search of food. A group of large
birds flying gracefully in formation just above the surface of
the water is probably a flock of pelicans.
Sand pipers and plovers are the smaller birds that run up and
down the beaches, carefully avoiding the breaking waves. They
are
generally long-legged, small to medium in size, and inconspicuous
in color. Their food consists of animal and plant fragments that
have been cast onto the sand by waves and the tiny animals that
live in the upper surfaces of the sand.
SAND DUNES
Sand dunes form when large amounts of sand are blown inland from
a
constant source of supply such as a beach. Where the wind is
slowed by a log or clump of grass, it drops its load of sand, and
a mound slowly builds up. As the mound grows, more sand is
deposited behind it; growing larger and higher, the mound becomes
a small hill, a ridge, and finally a dune. Wind-blown sand
blowing up the face and falling down the crest gives the dune its
characteristic shape -- a long sloping windward side and a
steeper slope on the lee side. If nothing interferes with the
wind or anchors the sand, the dune creeps inland as the wind
moves sand from the windward to the lee side. The rate at which
a dune advances can vary from a few centimeters to many meters
per year. A fast¨moving dune can bury everything in its path.
The movement of sand dunes may be slowed by the invasion of
pioneer plants that can root and grow in the shifting sands;
often it is grasses, such as Marran grass -- or Poverty grass --
which begin the stabilization process. After the clumps of grass
have become established, shrubby plants can take root on the lee
face of the dune. Protected from the wind and with their roots
close to the water table, these shrubs often form dense thickets,
providing shelter and food for small mammals and birds.
Dune life tends to progress from that of bare sand to dense
woodland, but this progression can be halted and hundreds of
years of growth destroyed in a very short time. Hurricanes,
fires, or construction (the building of homes, cottages, or
roads) can disrupt the stability that took so long to establish.
When a break in the vegetation mat occurs, the wind can quickly
charge through it, tearing at the roots of nearby plants. As
successive clumps of plants are exposed, more and more sand is
released, and the dune begins to move again.
ROCKY SHORES
Rocky shores are the coastal areas where the confrontation of
land (continent or island) with the ocean is most evident. Here
the rocky under-pinnings are ceaselessly attacked by moving
water, sometimes on a spectacular scale. For example, on our
Pacific shores, where wind¨driven waves can build up over almost
10,000 km (6,000 mi) of open ocean, the surf is as violent as
anywhere in the world. Even normal winter storms generate 6 m
(20 ft) waves that break against the shore with a shock
equivalent to an automobile striking a wall at about 145 km/h (90
mph).
Even though the glass beacon on Tillamook Rock light house on the
coast of Oregon is some 42 m (140 ft) high, a grating had to be
installed over the glass to protect it from rocks tossed up by
the pounding seas. Of course, not all rocky coasts are as
exposed as Tillamook Rock. Offshore islands, reefs, and
headlands provide protection from the pounding surf when they are
in the direction of the prevailing winds.
The composition of the rocky shores of the United States varies
significantly from one place to another. In the northeastern
United States, shorelines are made up largely of metamorphic and
intrusive igneous rocks, but those on the southern Atlantic coast
might be sandstone, coarse shell gravel, or coral. Continental
Pacific coasts are largely sedimentary rock, and the Hawaiian
coasts are igneous rock. The shores of the Great Lakes have
rocky coasts, some of which are formed by older sedimentary rock
and others by ancient metamorphic rock. Since the nature of the
rocky substrate, the rate at which it erodes, the forms produced
by erosion, and the mineral content released are so variable, it
is not possible to deal with these factors in a publication of
this nature. Teachers who want to explore the rocky coast should
research their coastal zones in one of the publications cited in
the bibliography.
The kind of biological communities that will live on any
particular rocky coast is determined largely by the degree of
exposure to open surf, and by the extent of tidal exposure. Life
forms can vary significantly from one side of an island or a
headland to the other because conditions which regulate life are
so different. Regardless of their exposure to violent surf,
rocky shores are much more active biologically than sandy ones,
for they offer a solid, unmoving (albeit hazardous) place where
both plants and animals can attach and survive. Thus, rocky
shores are better than sandy ones for providing opportunities to
observe a wide assemblage of marine organisms.
Significant differences in the appearance of the marine shoreline
are evident at high and low tides. A careful observer can see
the orderly progression of plants and animals. These species lie
in horizontal "belts" across the shore, one strip above another.
In many places, these strips (or zones) are brightly colored by
the resident organisms and therefore sharply delineated; a view
of them from the shore is often startling. On other coasts such
zones may be less obvious and more difficult to distinguish, but
they are rarely absent.
Local zonation may vary considerably. Zones of a rocky face
directed seaward will differ from zones facing the land or from
those at right angles to the shore. Zones on a smooth, sloping
rock surface may be immediately apparent whereas a shore of
broken rock lying at random angles may seem not to have a pattern
of zones at all. Similarly, the zones found on sunlit slopes are
noticeably different from those in areas shaded by overhanging
rock.
Turbulence governs the life of organisms living between tide
marks on rocky coasts. Even when the ocean surface appears to be
calm, there is usually a swell which explodes when it strikes the
coast. Animals that live there seem to prefer this turbulence,
and the highly aerated water it produces is crucial to their
existence.
Organisms living near the upper tide mark must be able to resist
desiccation during low tides. Many intertidal organisms have
developed anchoring methods that keep them in place even during
storms which batter them for hours on end. By and large, it is
the adaptation of such organisms to life under very special
conditions that governs intertidal zonation.
The extreme variations found in coastal areas in the United
States make it difficult to recognize the zones between tide
marks. The following definitions of the intertidal subdivisions
may therefore be helpful.
SPLASH ZONE
The splash zone is the area of transition between water and land.
Although it is affected by spray, it is covered by water only at
the highest tides or during storms. Animals that might inhabit
this area are the periwinkle snail and the pill bug.
HIGH TIDE ZONE
Where the high tide zone is most fully developed, barnacles form
a dense, almost continuous sheet on the rocks. Often this sheet
has a sharp upper limit which is a very conspicuous part of the
shore line. On some shores limpets are present with the
barnacles. Rock weed can be found in the lower edges of this
zone.
MID-TIDE ZONE
Each day the mid-tide zone is usually uncovered twice (at low
tide) and covered twice (at high tide). Animals found here are
seldom found in the deeper waters that are not as affected by
tidal fluctuation. Sea anemones, star fish, mussels, and hermit
crabs are frequently found in this zone.
LOW TIDE ZONE
Only during the very lowest tides, once or twice a month, is the
low tide zone exposed to view, and then only briefly. Animals
found in this zone can also be found in deeper water. The animal
and plant populations of this zone are large and varied. In cold
temperate regions, these populations consist of forests of the
brown algae with animals and an undergrowth of small plants on
their holdfasts. Coral reefs commonly include or encompass the
upper edge of the rich growth that extends down the reef face
below low¨water level. In warm temperate regions the low tide
zone may support dense colonies of tunicates and other ascidians,
as well as dense growths of red algae.
Before visiting your coast consult a local publication which
describes in some detail the organisms present and their
distribution. Living organisms should be observed where they are
found, not collected. Disturbing the shore line in any
significant way is to be avoided at all costs.
Remember that rocky coasts can be dangerous places to observe,
especially at low tide when the tendency is to walk out as far as
possible. Even on relatively calm days unpredictable large
swells may develop, so careful watch should be maintained.
ESTUARIES
An estuary is a partially enclosed body of water connected to the
open sea; thus, the seawater is diluted by fresh water draining
from the land. An estuary is the site of forceful interaction
between sea, land, and air.
Along the coasts of the United States there are almost 900
estuaries of many different types. Along the Atlantic coast
there are drowned valley estuaries, exemplified by Chesapeake and
Delaware Bays. Estuaries that developed behind barrier beaches
are found at Ocean City, Maryland, and at Biscayne Bay, Florida.
In contrast, the estuaries along our northˇwest Pacific coastline
are majestic glacier-gouged fjords, where the rivers are
contained by steep rocky slopes. Earthquakes, land shifts, and
other violent actions have created estuaries such as San
Francisco Bay.
The food chains in estuaries include two distinct populations of
primary producers -- phytoplankton and rooted aquatic plants at
the edges of the estuary. The abundant zooplankton present
include larvae of most of the organisms that live in the estuary.
The behavioral patterns of many species of zooplankton keep them
within the circulation pattern of the estuary and prevent them
from being washed out to sea.
Benthos (bottom-dwelling species) are usually more abundant in
estuaries than in either fresh or salt water environments. These
species are quite diverse, ranging from annelid worms through a
variety of crustaceans and mollusks. Many feed by various
filtering processes, an effective way of trapping the nutrients
flowing through the estuary. Oysters and clams are the most
commercially valuable of these filter feeders harvested by man.
The benthic populations range from fresh to marine
environments,but the most dense beds are often near the center of
the estuarine system. The distribution of the oyster, for
example, seems to be controlled primarily by three factors: the
upstream limit is set by the maximum flow of fresh water from the
river; the downstream limit is set by predators and parasites
which are found only in high salinities; and the lateral limit
depends on the presence of a relatively firm channel shoulder.
Among our coastal fishes the most commercially valuable species
are either partly or entirely dependent on estuarine
environments. Fish use estuaries in many different ways. Some
populations of striped bass spawn near the interface of fresh and
low-salinity water, others move farther into the rivers, and some
populations are even adapted to fresh water. In an estuary, eggs
and larvae drift downstream. The developing fish feed throughout
the system until they are adults and the cycle begins again.
Anadromous fish, such as the shad or salmon, spend their adult
lives in the open ocean but return to fresh water to breed. Shad
also use the estuary as a nursery for the first summer before the
young fish move to the ocean. In contrast, the croaker, which
also depends on the waters of estuaries for reproduction, spawns
at the entrance to the estuary and the young are transported
upstream to the plankton-rich, less saline part of the estuary,
where they develop before returning to the ocean.
Open ocean fish, such as the bluefish, whose early life histories
are totally marine, migrate into estuaries as adults to feed on
the abundant food available there.
These varied patterns of estuarine use are concurrent as each
species follows its own seasonal and reproductive sequence. Thus
an estuary may include the regular or occasional presence of
several hundred species of fish. The low-salinity portion of the
estuary is of exceptional importance since it receives the eggs,
larvae, and young of fish with different kinds of spawning
patterns. Although this aspect of the estuary is highly valuable,
its value is not obvious because these stages in the life cycle
of fish are not immediately recognizable. Since many large cities
are located near estuaries close to the head of navigable waters,
this potential impact merits special attention.
MARSHES
Marshes are broad wet areas where grasses grow in abundance.
When they are located along the margins of ponds, streams, or
rivers, they are freshwater marshes. When they are found on
ocean coasts or along the banks or margins of estuaries, they are
salt water marshes. Salt water marshes are the nurseries of the
sea. They are the most productive land on earth, producing three
times more than the best wheat lands.
Biologically, marshes are transitional between wet and dry areas,
and they are usually very productive in terms of the biomass they
can support. If undisturbed by nature or man, most marshes
gradually fill with detritus and are eventually invaded by dry
land plants.
In freshwater ecosystems, marshes contain such water-tolerant
species as cattails, bulrushes, horsetails, arrowgrass, flowering
rushes, buttercups, crowfoot, and many types of grasses. These
marshes are also homes for many aquatic insects, amphibia,
crayfish, isopods, birds, and aquatic mammals; when they are
associated with permanent bodies of water, they may serve as
nurseries for young fish. Lake St. Clair (a very wide area in the
isthmus connecting Lake Huron with Lake Erie), which has
extensive marshy areas built on the silt deposited from Lake
Huron, is one of the most productive freshwater fisheries in the
world.
Salt water marshes can best be classified by their relation to
the land or the ocean. Of all salt marshes, the most maritime
(bearing the closest relation to the ocean) are those that
develop on relatively open coasts. They are bathed in sea water
at almost full strength since the freshwater drainage from land
is usually minimal. These marshes are usually rich in algae,
including free-living species and tiny forms of the brown algae
derived from normal forms that are attached to rocky shores near
the marshes.
Marshes at the mouths of estuaries, usually found in the lee of
coastal spits, are the next most maritime of the salt marshes.
The coarse-grained soils of these marshes are subject to stronger
saline influence than those of marshes further up the estuary.
As their distance from the ocean increases toward the middle and
upper reaches of the estuaries, the marshes tend to become
progressively more terrestrial since the water becomes
progressively fresher.
Despite the wide range of conditions in the United States under
which salt marshes exist, some general statements about their
formation and the distribution of organisms within them can be
made. Salt-marsh formation usually starts in an area that is
subject to twice-daily salt water (tidal) inundation. Salt-
marshes are replaced by freshwater marshes at the upper level of
tidal influence, where tidal inundations occur only a few times a
year. Between these two extremes, plants and animals thrive
according to the range of conditions they can tolerate -
conditions that are dominated by the tides at the lower levels--
and almost independent of them at the upper levels.
Some factors of crucial importance to the survival, growth, and
reproduction of organisms in the intertidal zone are the
intensity and frequency of mechanical disturbance due to tidal
movement; the vertical range over which the tide operates, which
determines flooding depths and the vertical extent of the marsh;
the form of the tidal cycle, which determines both the frequency
and the length of submergence and emergence and the water
quality, which determines, among other things, the amount of
light reaching submerged growths and the salinity to which they
are subjected.
Grasses are the most prominent plants in salt marshes. Cord
grass in a long and a short form, is the grass most likely to
live in marsh areas covered by water at high tides. Other salt-
tolerant plants and plants tolerant to salt spray make up the
upper edges of the marsh and vary with the locality.
Animals are widely distributed in salt marshes and the adjacent
mud flats, although their distribution patterns are not as
obvious as those of the plants. Mud flats are occupied by
burrowing creatures such as marine worms and clams, which are fed
on in turn by other organisms.
Fish come in with the tide to feed on the abundant small forms of
life that occupy the marshes. Birds are prevalent in marshy
areas. Some, such as the marsh wrens, swallows, ducks, geese,
herons, and rails nest in or around marshes and get most of their
food from them. Mammals such as raccoons, mice, rats and, less
often, otters and mink inhabit marshes and feed on other
organisms that live there. Marshes are also crucial stopping and
feeding stations for flocks of migratory birds.
Marshes are rich in numbers of species as well as numbers of
individuals. Species with aquatic larvae, such as mosquitos,
gnats, and dragonflies are well represented. Other species, such
as grasshopper and cricket, enter the marshes to feed.
In a terrestrial grassland, energy conversion relies on direct
consumption of green plants. In contrast, energy conversion in
salt marshes relies on decay as the chief link between primary
and secondary productivity. Only a small proportion of marsh
grass is grazed while it is still alive. Not only is the role of
phytoplankton in energy production in marshes less than it is in
open water, but also cloudy water or turbidity may diminish algae
productivity by reducing the amount of light available for photo-
synthesis.
FOOD CHAIN
The food chain of nature is complex. Each step up the chain
involves a decrease in the number of organisms and an
accompanying increase in the amount of food they consume. At the
bottom of the food chain, 1000 pounds of phytoplankton will
result in 100 pounds of insects and small animals. In turn 100
pounds of insects result in 10 pounds of fish, ducks and birds.
People are at the top of the steadily narrowing food chain. As
in the other steps, it takes 10 pounds of ducks or fish to
produce a one pound gain in human beings.
Coastal Zone Awareness Activities for Elementary School Students
The activities included were chosen because they will provide
students first-hand experiences with natural phenomena. Such
experiences are the basis for learning -- they are thought-
provoking and provide ideas to share through speech and writing.
Students may even wish to seek out books or other secondary
sources of information that will add to their own findings. The
purpose of these suggestions is not to have l\children learn all
about coasts but rather to provide an experiential background
that will be the basis for a lifelong interest in coastal
processes.
When visiting a beach or shore students should be encouraged in
positive way to leave the area in the same shape they found it.
When any microhabitat, such as a rock or log, is moved, it should
be replaced as it was found. If organisms are living under it
they may depend on that object for survival. Children should be
helped to understand why they should not collect living things
but only observe them.
What FLOATS?
Have children collect natural objects along the shore, put them
in water, and observe whether they float or sink. They should
try as many different kinds of substances as they wish but should
also experiment with different shapes of the same substance. The
more such experiments each child attempts, the better the
experience will be. In a group discussion after the experiments
see if the children can develop some generalizations about
floating and sinking. Avoid summarizing their experiences for
them since this would probably not significantly add to their
long-term learning.
Have students who cannot visit the coast collect and bring
objects to the classroom and substitute containers of water for
the coastline.
FRESH WATER OR SALT?
In the classroom students can discover some of the differences
between the properties of fresh and salt water. Some or all of
the following manipulations can be included. Compare the level
at which different objects float in fresh and salt water and the
time it takes them to sink. Place a drop of colored fresh water
in a container of fresh water and a drop of colored fresh water
in a container of sea water. Observe and discuss the difference
in the results.
AT THE BEACH
At the coast there are many things for children to do.
They should close their eyes and listen to the sounds waves make
as they break on the beach. Do they make the same sounds on
sandy beaches and rocky beaches? Do the waves sound near or far
away.
Have the children describe what sea air smells like. How far
away from the beach can they smell it?
They can look for bird footprints in the sand. Are there more
tracks near the water's edge or farther up on the beach? Can
they guess the size of the bird that made each kind of print?
Let the children make a drawing of a bird footprint or help them
make plaster casts of bird footprints to take home.
In a class discussion period make a list of the different kinds
of birds the children saw at the beach. Se if they can remember
and mimic the kinds of sounds each one made.
Help the children make a plant collection of the different kinds
of water plants they found washed up on the open beach. What is
the biggest one they found? The smallest? Where do they think
they came from?
Using Tide Tables
Please who live near oceans can plan exploratory trips to the sea
shore more effectively if they know what the tidal level will be
when they get there. If you want to go to see the animals that
live at the lowest level of the intertidal zone then you should
visit the shore when the tides are at their lowest ebb. You can
find this information by getting a tide table for your local
area. Reading a tide table seems difficult at first so practice
on the sample below which was taken from a table constructed for
Breakwater Harbor, Delaware. Tide tables give you six kinds of
information.
OCTOBER 1970
Month Time Year
Date 16 0236 -0.5 Height of tide
Day of Week TH 0906 5.6 (2 high tides and
1524 -0.4 2 low tides)
2136 4.4
The time is based on the 24 hour where 0000 is 12 o'clock
midnight and 1200 is 12 o'clock noon. So 0236 would be 2:36 AM
and 1524 would be 3:24 PM. The height of the tide is related to
the mean low water level. A number preceded by a minus sign
means that the water level will be below mean low water. No
minus sign indicates the height of the water above mean low
water.
17 0318 -0.3
SA 0954 5.4
1612 -0.2
4.0
18 0406 0.0
SU 1042 5.2
1706 0.1
2312 3.7
19 0454 0.3
MO 1136 4.9
1800 0.4
20 0006 3.4
TU 0548 0.6
1230 4.5
1900 0.7
Using the information above, answer the following questions:
1. What day of the week will have the highest tide?
2. On which date will the high tide be the lowest?
3. Which day would be best for looking for organisms farthest
down the beach?
4. Using the 12 hour clock what is the best time to visit the
beach on Sunday during high tide?
Plant Cells and Salt Concentration
Collect a living piece of marine algae such as sea lettuce (Ulva)
and a freshwater plant, such as Anacharis. While observing their
cells through a microscope, flood each one alternately with fresh
water, then salt water. Note and compare the responses of the
cells to each condition. What explanation can you give for these
different responses?
Oceans As Places for Waste Disposal
Who controls the manner of disposal and amounts of wastes that
are emptied into your coastal waters? Does your local Board of
Health have this authority? Are there state and federal laws
that are applicable also? Write a brief report about how waste
discharge in your area is monitored and controlled.
Animals Living on Plants
Many small marine animals live on aquatic plants but they are
often difficult to see. Collect some plants from shallow water.
Be sure to get hold fasts and not too much mud. Drop the samples
into a bucket of sea water to which you have added a 10% solution
of formalin. The organisms will leave the plants and fall to the
bottom of the bucket. Quickly remove the plants and collect the
organisms from the bottom of the bucket using a glass tube.
Examine and record what you see under a binocular microscope.
What animal phyla are represented?
Crustacean Growth Curves
Keep a commonly available crustacean (freshwater or marine) in an
aquarium; the length of time it should be held varies according
to the growth rate of the organism. Collect the molted
exoskeletons as they are shed, being sure to note the date of
each molt. Make a display that shows the growth of one or more
aspects of the exoskeleton, such as the width of the carapace or
the length of a front claw.
Beach Hopper Population Count
Count the number of beach hoppers in a square meter at several
(four or more) locations on a beach. Calculate the average
number of hoppers per square meter. Calculate the area of the
beach within one kilometer of your sample, and the number of
hoppers on that section of beach.
Fresh Water from a Marine Beach?
Dig a hole about one meter in diameter and about 30 to 40 cm deep
in a sandy beach. Choose a sunny spot, where the tide will not
wash in for several hours. Place a collection container at the
center of the bottom of the hole. Cover the hole with a piece of
heavy clear plastic that extends well beyond the edges of the
hole in all directions. Anchor the plastic with heavy rocks in
such a way that it sags into the hole but does not touch the
bottom or sides of the hole. Seal the edges with sand. Place a
rock in the center of the plastic, over the container. After
several hours, or longer if you have time, look for moisture on
the underside of the plastic and in the container. Taste the
water. Could you drink it? What is its source? Explain.
(This activity can also be carried out on a freshwater beach.)
Seasonal Changes in Sandy Beach Structure
What effect do changes in seasons and the accompanying changes in
storm patterns have on the shape and profile of the beaches in
your coastal zone? Locate a beach to study. During a low tide,
photograph the beach profile and note the position of objects
above the normal high tide line. Repeat this process several
times during the year. Make a display of your findings.
Coastal Productivity
Why do people congregate to fish at some places along the coast
but not at others? Are these places more productive
biologically? Survey the people that are fishing. Ask them why
that place (or those places) are superior to others. Talk to as
many people as you can, preferably on more than one occasion.
What factors can you identify that make the fish more plentiful
in some areas than in others?
Feeding Habits of Marine Fish
Make arrangements with a cannery, sport fishing boat, or
fisherman you know to save the digestive tracts of specific kinds
of fish. Examine the contents of the digestive tract for the
remains of food organisms. Keep a careful record of food
preferences of fish by species.
Survey of a Tidal Pool
Carefully divide the area of a tidal pool into one-meter squares.
Draw a diagram with squares, like the pool. Count the organisms.
Note the kinds of organisms in each square and locate these in
the proper square of your drawing of the pool. Measure and
record water depth, temperature, salinity, and oxygen
concentration at the location where each organism is most
prevalent. What conditions do you think each of these organisms
prefers?
Coastal Model
Get a topographical map of part of the coast in your area. Maps
can be obtained from the Geological Survey, U.S. Department of
Interior. Using the data on the map, make a plaster of paris
model of some segment of your coastline. Include segments of the
continental slope, the fore coast and the back coast. Local
hydrological charts would also be of value in constructing that
area below the water line. Mark in some special color the areas
that are used extensively by people.
Soil Profiles in Coastal Areas
A soil profile is a kind of historical record of the ecological
events that occur in a particular area. The profile is an
accurate drawing of a carefully excavated hole. The side that
you draw should be vertical and smooth. Sketch in each layer you
can identify. Keep careful notes as to the width of each layer,
particle sizes, color, and composition, the presence of organic
matter or shells, and other interesting elements of each layer.
Make profiles of sparse dune grassland, dense dune grassland, and
open beach, and compare the profiles.
What features are different? The same? What can you infer about
the history of the area? Carefully fill your holes when you are
done.
Handmade Hydrometer
For the body of the hydrometer, use a test tube or a slender
wooden cylinder. Weight one end so that the tube floats
vertically and is stable. Calibrate your hydrometer with known
concentrations of salt water, ranging from 35 parts of salt per
thousand of water down to fresh water. Make your markings so
they are relatively permanent. Now compare your readings with a
commercial hydrometer available from a tropical fish store. How
can you tell which one is correct if they differ?
Salinity in an Estuary
Using the hydrometer you made or a commercial one, sample the
specific gravity of an estuary at several places from the mouth
up into the river. Knowing what you do about the relative
density of sea water and freshwater, at what depths should you
take your samples? Take a water sample from each place you make
a measurement and take it back to the school laboratory.
Evaporate 100 ml amounts from each sample and determine the
percentage of salt. Find a way to compare this measure of
salinity with your hydrometer readings.
Measuring Suspended and Dissolved Solids in Water
The turbidity (amount of suspended and dissolved solids in a body
of water) has an effect on the amount of light that water will
transmit. In this way, suspended and dissolved solids affect the
rate of photosynthesis in bottom-dwelling plants.
The amount of suspended solids in a sample of water can easily be
measured. First, weigh a round sheet of filter paper. Filter
one liter of a water sample. Allow the filter paper to dry
completely, in an oven if possible. Use a temperature low enough
so the filter paper will not burn. Re-weigh the filter paper.
The difference in weight is the weight of the suspended solids
that were in your sample. These values are usually given in
parts per million or milligrams per liter. (Dissolved solids are
measured the same way as salt, by evaporation.)
Take a series of water samples in an estuary, stopping at several
places from the mouth up into the river. Measure the amounts of
suspended and dissolved solids in each. What do your results
tell you about the sources of dissolved solids in the estuary?
This same process can be carried out where a river or stream
enters a lake.
Temperature and Specific Gravity
Gradually reduce the temperature of a sample of sea water from
room temperature to about 5 degrees C. At every 5 degree change
of temperature, use your hydrometer to measure the specific
gravity. Plot your results on a graph, using the horizontal axis
for temperature. Describe your results in terms of the effects
of temperature on specific gravity.
Measuring Wave Length
This activity should be conducted when wave size offers no danger
to students. Wave length is the distance from the crest of one
wave to the crest of the next. To find out wave length in a lake
or ocean at a particular time, you need to measure two aspects of
the wave motion: the velocity (or speed) at which the wave is
moving through the water (meters per second) and the time in
seconds it takes for two successive wave crests to pass a fixed
point (period).
To calculate velocity, attach a 3-meter rope to two tall stakes
and place the stakes in the water so that one stake is three
meters closer to the beach than the other. The rope should be
taut but not stretched, and at about water level. Measure the
time it takes for a wave crest to travel from the first stake to
the next. Do this at least five times; then compute an average
velocity in centimeters per second. Now record the time between
crests (from the time that one crest hits a stake until another
hits that same stake). Do this for at least five successive
waves. Calculate the average wave period in seconds. Find the
wave length in centimeters by using the following equation:
Wave length = velocity x period
cm = cm/s x s
Measuring Turbidity
Make a photometer to measure turbidity of coastal waters. You
can make a reasonably accurate photometer from readily available
components for less than $10.00. You will need an inexpensive
volt-ohm meter (VOM), a cadmium sulfide photo cell, and a block
of soft wood (pine) about 15 cm long and 10 cm square. You will
also need some test tubes to carry out your experiments. At one
end of the block drill a hole that is centered and goes almost
through the length of the wood. The diameter of the hole should
be slightly larger than 2.6 cm so it will accommodate a large
test tube. Next drill a hole at right angles to the first hole,
and passing through it, so that the paths cross. The second hole
should go through the wood from side to side. The diameter of
this hole should allow the photocell to fit tightly. Push the
photo cell into one of the side holes a short distance and secure
it with an epoxy cement. Attach the leads of the VOM to the
leads of the photo cell and you are ready to test your
turbidometer. Shine a light through the wood onto the surface of
the photo cell. Set the selector of the VOM on R x 1, Q, or R.
The needle of the meter should deflect. An ideal bulb size for a
light source is 75 or 100 watts. Determine the most effective
distance of the light source from the meter by trial and error.
Now you are ready to introduce test tubes of turbid water into
the turbidometer. The more turbid the water is, the less is the
light that will reach your photo cell, and the less the needle
will deflect.
Compare samples from different places along your coast. Graph
your data. If you use the Q or R scale, use semi-log pacer.
Bird Prints and Behavior
Walk along a sandy beach looking for the footprints of birds.
On an ocean beach this is most productive on a receding tide.
Make sketches or plaster of paris casts of the footprints. Take
your sketches to the classroom and see if you can find out what
kinds of birds made the prints.
COASTAL ZONE AWARENESS ACTIVITIES FOR HIGH SCHOOL STUDENTS
This collection of suggestions for activities is designed for
high school students. Some of these activities can be carried
out in the classroom and others in any aquatic environment; some
require access to a marine environment. The activities suggested
range in difficulty from the relatively simple to the fairly
complicated. Some require a high order of cognitive processes
for understanding; thus there should be a fit with student skills
at a variety of grade levels.
Teachers will note that the suggestions are written mostly as
directions for students rather than for teachers. This is
largely a space saving device, but it does allow for more rapid
skimming of ideas to see what is available and suitable to your
environment.
Anemone Behavior
If you live in an area where anemones are plentiful and the state
authorities allow it, taking an anemone temporarily for
experimentation and returning it to the water can be a rewarding
experience. A single anemone can be kept in a plastic shoe box
aquarium with an air stone for as long as a week. The
temperature of the water in the shoe box should be maintained at
the temperature of the water where the anemone was collected.
There are many things you can do to learn about anemones. Place
a piece of raw shrimp or fish (about pea size) in a nylon mesh
bag made from a stocking. Put the nylon bag on a piece of thread
and let the anemone eat it. Look at it the next day. Feed your
anemone a small piece of food that was cooked in food dye.
Record what happens.
If you give your anemone a choice of sand, small rocks, or big
ones, where will it anchor? Try placing a checkerboard pattern
on the bottom (or, if the bottom is clear plastic, place the
pattern under the box) of your shoe box aquarium. The squares
should be at least as large as the anemone. Where will the
anemone anchor, on a light or a dark square?
Can your anemone tell food from non-food? Attach pieces of real
food and inert (non-poisonous) materials to threads and carefully
lower them into the water, near the anemone. What happens?
Return your anemone to the ocean carefully, to the place where it
was collected.
Tidal Marsh and Flats
What proportion of a tidal marsh is exposed as mud or sand flats
during low tide? Take photographs of such an area at high and
low tides. Compare these and, by locating landmarks on a map,
compute the area exposed by a low tide. How large is the exposed
area compared to the area where the bottom isn't exposed?
Piling Organisms in an Estuary
Visit several areas in an estuary, from the mouth up into the
river. During low tide observe and record the kinds of organisms
that live on the pilings in each area. Take specific gravity
readings at each location. Does the decreasing salinity affect
the kind of organisms that can grow there? How is this indicated
by your survey?
Using Tide Tables
People who live near oceans can plan exploratory trips to the
seashore more effectively if they know what the tidal level will
be when they get there. If you want to go to see the animals
that live at the lower level of the intertidal zone then you
should visit the shore when the tides are at their lowest ebb.
You can find this information by getting a tide table for your
local area. Reading a tide table seems difficult at first so
practice on the sample below which was taken from a table
constructed for Breakwater Harbor, Delaware. Tide tables give
you six kinds of information:
OCTOBER 1970
Month
Time Year
Date 16 0236 -0.5 Height of tide
0906 5.6 (2 high tides and
Day of Week TH 1524 -0.4 2 low tides)
2136 4.4
The time is based on the 24 hour where 0000 is 12 o'clock
midnight and 1200 is 12 o'clock noon. So 0236 would be 2:36 AM
and 1524 would be 3:24 PM. The height of the tide is related to
the mean low water level. A number preceded by a minus sign
means that the water level will be below mean low water. No
minus sign indicates the height of the water above mean low
water.
17 0318 -0.3
SA 0954 5.4
1612 -0.2
4.0
18 0406 0.0
SU 1042 5.2
1706 0.1
2312 3.7
19 0454 0.3
MO 1136 4.9
1800 0.4
20 0006 3.4
TU 0548 0.6
1230 4.5
1900 0.7
Using the information above answer the following questions.
1. What day of the week will have the highest tide?
2. On which date will the high tide be the lowest?
3. Which day would be best for looking for organisms farthest
down the beach?
4. Using the 12 hour clock what is the best time to visit the
beach on Sunday during high tide?
At high tide make a map of a small section of coastline. Put in
rocks, curves in the beach, and the location of logs and other
things that are lying on the beach. Make another map of the same
place at low tide. Compare your maps.
Put a rock in the sand just below where the waves are washing up
on the beach. Do this only if the waves are small and not
dangerous. After each wave goes out look at the sand around your
rock and describe what is happening.
Beach Currents
Is there a beach current? You can often determine the direction
of beach currents by observing the direction taken by floating
objects thrown into the surf. Brightly colored objects--balls or
balloons partially filled with water--make good objects to
observe.
Do the currents along your beach run parallel to the coast? Are
they influenced by curving coast lines or headlands? Can you
measure the rate at which the current is moving?
Mark off in the sand 50 or 100 steps and time how long it takes
your object to move that distance.
Sand in Motion (Erosion)
Which way is the sand moving? Plant a stake in the sand midway
between the highest wave mark and the low point of wave
recession. Does sand accumulate on one side of the stake? Is it
washed out from another side? Can you decide in which direction
sand is being moved?
Measuring Tidal Change
Mark a stake in centimeter intervals, and when you arrive at the
beach drive it into the sand so that the water covers the lower
part of the stake after the waves have receded. Watch the water
level on the stake. Is the tide coming in or going out? Can you
measure the vertical distance (up the stake) traveled by the
water during your stay at the beach?
Oil Spills
How would a small oil spill affect your coast? You can use non-
polluting material to represent drops of oil. Pick a dock or
some prominence that extends out into the water as the place to
have your "oil spill." Throw your simulated oil drops (leaves,
shavings, or sawdust) into the water and watch what happens.
What factors determine where your spill reaches the coast? How
big an area is affected? Which animals and plants collect the
most "oil"? How would your oil spill affect recreation in your
area?
Measuring Wind Erosion
Coat the top 10 cm of the sides of a short, square post (a four
by four will work) with petroleum jelly. Sink the post into a
section of sandy beach. Observe the post after 24 hours. On
which side is the sand the highest? In which direction was the
sand moving? What was happening to the beach--was it being built
up or eroded? Does this pattern change from high tide to low
tide, from day to day? What is the most sand that will collect
by the post in one day?
Prints of Aquatic Plants
Buy some ozalid paper from a store that handles drafting
supplies. It comes in a roll and you will have to cut it to the
size you want in a dark room. Using glass, a piece of cardboard
the same size as the glass, and masking tape to hold them
together on one side, make a frame for exposing the paper. Then
cut pieces of Ozalid paper to fit in the frame. Place a plant
(or feather, or other material you collected from the beach)
between the glass and the sensitive side of a piece of the paper.
Press the cardboard against the paper, and hold the glass toward
the sun. Red paper will take about 15-25 seconds of exposure,
blue paper about 20-35 seconds, and black about 40-50 seconds.
You may have to experiment to get the proper timing.
Remove the Ozalid paper from the frame in a shaded place. Roll
into a cylinder, put it in a large jar containing a small open
jar of concentrated ammonia, and cover the top of the large jar.
The fumes from the ammonia will develop the print in 3 or 4
minutes. If prints are too pale, they were not exposed to fumes
long enough; dark, heavy prints indicate excessive exposure. Use
a fresh supply of ammonia each time you print; concentrated
ammonia usually is available at drug stores. Household ammonia
is not concentrated enough. Do not inhale the fumes from the
jar.
Observing Barnacles
Take a plastic shoe box or similar container with you to a rocky
seashore. Find a rock that has barnacles on it that will fit in
your container. Cover the barnacles with sea water, sit back,
and watch what happens.
What is the function of the four plates on the front of the
barnacle? When the barnacle opens, what comes out? Make a
shadow across the top of an open barnacle. What happens? What
happens when you put a few drops of fluid from a crushed clam or
piece of fish near an open barnacle? When you have finished,
carefully put your barnacle rock back where you found it.
Watching Aquatic Organisms With a Look Box
A "look box" will allow you to look into the water, on the
bottom, and to see things not easily seen from above the water.
To make your look box, remove both ends from a large (#10) can,
and tape clear plastic wrap across the openings, or use your
imagination to design your own kind of look box. Bring extra
plastic wrap and tape with you to the coast in case your box is
damaged. The secret to seeing with such a box is to move slowly
and carefully, and to be patient.
How many kinds of moving animals can you see? How many are
attached? Are the fish in the open or hidden? What kinds of
plants do you see, and are they just in some places or
everywhere? Make a sketch of the things in the small area you
are observing.
Hermit Crab Houses
Do hermit crabs on the coast near you prefer to live in
particular kinds of shells? Take several containers with you to
a section of the coast where hermit crabs live. Pick a single
tidal pool and carefully pick up all the hermit crabs you can
find. Sort them into containers by the kind of shell they have.
You don't need to know the kinds of shell--only how they look.
Count the number of crabs in each container and then release
them.
Is one kind of shell preferred? Survey another pool to see if
the choices are the same. Make a chart showing the shape of the
shells and the numbers of crabs in each. Can you identify the
kinds of shells used most often?
Populations on Pilings
Is there a pattern to the way animals and plants grow on pilings
in salt-water estuaries? Find a place where you can examine the
underwater portion of several pilings during low tide; the lowest
tide is the best time. Carefully observe and record the kinds of
organisms present on one piling and the vertical space they
occupy--that is, which organisms are highest on the piling, which
the next highest, and so on. Then examine one or two other
pilings. What are the common characteristics with respect to
distribution of living things on the pilings? What are the
differences? What do you think affects the distribution of these
living things?
Bird Behavior
Find a comfortable place to sit along the coast in an area where
you can see more than one kind of bird.
Watch the groups of small birds that are pecking in the sand just
above the wave line. How do they keep from getting wet? Does
the group have a leader? What are they pecking at? Can you find
out? Watch one member of a particular species of bird for ten
minutes or so. Look for and record the following kinds of things
about that bird: the kind of bird; how it holds its body when it
walks (horizontal, upright, in between); its gait (hop, run, or
waddle); grooming (does it groom its feathers? How?). Also note
whether it raises its tail when it lands; whether it flies in a
straight line, undulates (up and down), glides, soars, or flaps;
and whether its wing beats are fast or slow. Does it get its
feet wet, land on water, or land on bushes or trees?
Observe several kinds of birds in this way and make a chart of
your records to show the differences and similarities among the
birds you watched.
Visit two or more types of coastal areas, such as a marsh and a
rocky beach. What kinds of birds are found in each? Where are
there more perching birds, wading birds, or swimmers? Identify
as many of these birds as you can. Visit these places during
more than one season. Do the kinds of birds present in each
change with changing seasons?
Poke Pole Fish Survey
What kinds of fish live in rocky intertidal areas? You can find
out what some of them are by going fishing with a poke pole.
Make your poke pole from a 2-3 m (6-10 ft) pole of bamboo or some
other material. Tape about 30 cm (12 in.) of heavy wire with a
size 2 or 4 fishhook on the end of the pole; 15 cm (about 6 in.)
of wire is attached to the pole and 15 cm hangs out, with the
hook on the end. File the barb from the hook so that you can
easily release fish without damaging them. This kind of fishing
should be done at low tide, but if there are large waves you
should stay away from the edge of the water. Bait the hook with
mussel, shrimp, or pieces of other marine animals. Fish by
putting the pole into deep pools or crevices in the rock. Try
many pools, keep a record of the kinds of fish you catch and
where you caught them. You should be able to release most of
your catch unharmed--unless of course you are very hungry.
What Kind of Organism Was It?
Walk along the beach soon after high tide. Make a collection of
the fragments of what were once living things. Examine each
fragment very carefully. Try to answer some of the following
questions about each one: Was it a plant or animal? What did it
look like when it was living? How big was it? Where did it
live? How did it get to where you found it on your beach? Can
you trace the path it took?
Life on a Rocky Beach
Visit the beach at low tide, and take with you pictures or
descriptions of plants and animals that are commonly found in
that area. What kinds of organisms are most common high up on
the shore, but within the tidal zone--plants or animals? What
kinds of organisms are most common in the lowest level exposed by
the receding tide? How would you name these areas if you used
the prevalent organisms to identify each zone? Which organisms
are best adapted to live for the longest period of time in the
air? Are there more water plants in the higher or the lower
zone?
Aquatic Coastal Inhabitants
Several students should cooperate in this project. Any coastal
area that is occupied by visible inhabitants is suitable. Select
a length of coast that can be easily examined in the time
available. Use graph paper to help you sketch the coast before
you begin the survey. Each time you find an organism, observe
and examine it. Record its description (in words and/or
pictures) along with the depth of the water where you found it or
its location on the beach.
Beach Hoppers
If you were a beach hopper how far could you hop? To find the
answer to this question measure your length (height), the length
of a beach hopper, and the distance a beach hopper hops.
Substitute these data in this equation:
your height divided by x will equal the length of hopper divided
by the distance that the hopper hops
Clams
If you live near a sand or mud flat in an estuary, you can dig
clams. You will need a shovel or trowel and a bucket without a
bottom. Go to the flats and find the likely places to look for
clams in your area, using clam siphon holes as indicators of good
places to dig. First jump or bang on the surface of the flat so
the clams will draw in their siphons; this way you will be less
likely to injure any of them. Dig around a siphon hole but not
too close to it to avoid breaking the clam's shell. When your
hole starts to cave in, put your bucket in it so that the siphon
hole is near the center and the bucket is buried almost to the
rim. Dig with your hands now. When you locate a clam, loosen it
carefully before you attempt to lift it out. (You may wish to
wear gloves to protect your hands from broken shells and glass.)
Remember to rebury each clam in the hole from which you took it.
Now that you know and have followed the procedure for locating
clams, see if you can answer the following questions:
How far up the beach do clams live?
Can you predict the size or kind of clam from the size of its
siphon hole?
Do little clams live closer to the surface than large ones?
How many kinds of clams live in this tidal area?
Do clams live alone or in groups?
Remember to put each clam back in the hole where you found it.
Be careful to leave an air hole.
"Rubbing It In"
Many weathered objects on beaches have attractive and complicated
patterns. Use plain paper and crayons or charcoal pencil to make
rubbings from weathered boards or ends of pilings.
Coastal Classroom Ideas
In the classroom, put some brine shrimp eggs in fresh water and
some in salt water and watch the containers for a few days.
Where do you think brine shrimp might live? Watch under the
microscope as your brine shrimp swim.
Make a trip to a nearby market. How many kinds of coastal
organisms are for sale? How many people handled them before they
reached the store?
In the classroom, put some sand and some soil in a glass
container with water and stir the mixture. Let the sand and soil
settle, then describe which layer is on top and which is on the
bottom.
Collect mud and sand from a marsh, beach, or river. Put sand and
mudin a glass container with water, mix it,and let it settle.
How many layers can you see? How are they different? What do you
think causes this layering?
Carefully pour or siphon off the water. Examine a sample of each
layer under the microscope. Describe and compare the particles.
Are they dark or light, rough or smooth, sharp, thick or thin?
How do mud particles differ from sand particles? Where do you
think each might have originated? How do you think they got to
where you collected them?
Make a Hydrometer
Take a stick (or pencil) and tie a weight such as a metal washer
to one end, or screw a sharpened pencil into a metal nut. Place
this "hydrometer" in a large container of fresh water. Mark the
water line on the stick. Now repeat this experiment in a
container of salt water. Is the water line on the stick
different in salty and fresh water? What do you think causes the
difference in the water line on the stick? Have a friend make a
measured salt water solution. Now, try to guess the salinity of
this solution.
How could you mark (calibrate) your hydrometer for a solution
that is one-third as salty as sea water? A solution one-half as
salty?
Density of Water
Which is more dense, salt or fresh water? Completely fill two
containers (such as baby food jars of the same size) with water.
Do not place lids on the jars. To one jar, add a drop of food
coloring and one half teaspoonful of salt. Mix well. Cover the
top of the salt water container with a piece of cardboard.
Invert the jar and place it directly over the top of the fresh
water container so that the openings are aligned and separated
only by the cardboard. Now, carefully slide out the cardboard.
Observe and record the movements of the colored water. Repeat
the experiment, this time putting the food coloring in the fresh
water and placing the fresh water container on top of the salt
water container. Try it sideways too.
What do you think happens when fresh river water flows into a
salty ocean?
Salt in Rivers
To learn how to measure salinity in the classroom, carefully
measure exactly 100 ml of sea water into a pyrex container.
Weigh the container and the water. Evaporate the water. Now
weigh the contents and the container again. Subtract your second
measurement from the first. Multiply the difference in weight by
ten (to adjust the volume from 100 ml to 1,000 ml). This will
give the salinity of your sample in parts of salt per thousand
parts of water (%).
Teachers with a marine aquarium can allow students to use the
aquarium water as "seawater" if they cannot get to the ocean.
Alternatively, several samples of salt water of various
concentrations can be set up by the teachers, and the students
can determine which one is closest in salinity to sea water.
Next, visit a salty river. How far up the river is the water
salty? In the classroom, using a hydrometer (available at
tropical fish stores), establish baseline readings for fresh
water and for salt water (30% salt in water). Then, take a trip
to a tidal river. Make a series of readings up the river from
the ocean to see if you can find out how far up the river the
water is salty. Consider the following questions:
Does high or low tide make a difference in your readings?
Can you tell when the water is one-half as salty as sea water?
Does the depth at which you take the reading make a difference?
How much of seawater is salt?
Coastal Awareness Activities for Middle and Junior High School
Students
Two elements are common to all activities suggested in this
collection: each requires a concrete experience as a basis for
learning, and each requires an action on the part of the learner.
A range of activities is offered: some must be pursued at the
seashore, others in fresh water environments, and still others in
the classroom. Teachers are encouraged to offer the widest
possible selection of activities to their students.
Since some of these activities involve children working at or
near the water's edge, students must be instructed in how to
behave in these potentially dangerous coastal areas. They must
be instructed not only for their own safety but for the
protection of the environment.
Teachers will note that suggestions are generally written as
directions to students rather than to teachers. This is largely
a space-saving device that allows for more rapid skimming of
ideas to see what is available and suitable to your environment.
Beach Art
Make a sculpture or another art form from litter you collect at
the beach. Take a picture of it to display in the classroom or
at home. How should you dispose of your art work?
Measuring Sand Dunes
Make a clinometer (an instrument used to determine inclination or
slope) by gluing a soda straw along the straight edge of a
protractor and attaching a weighted string to the zero mark in
the middle on the straight edge of the protractor. You also will
need a stick that comes up to your eye level from the ground.
Plant the stick at the top of a dune. From the bottom of the
dune, sight through the straw to the top of your stick (the curve
of the protractor will be on the underside of the straw). Note
the angle of the string hanging down over the curved side of the
protractor. Subtract this number from 90 degrees (vertical) to
find the angle of the dune. Measure the front and back angles of
the dune. Which is the steeper? Which would slide more easily?
Can you pile sand from that dune at a steeper angle than the back
slope?
Ideas for Coastal Observations
Visit a rocky beach at low tide. Take along pieces of fresh
shrimp or fish and feed small crabs or anemones; describe how
they respond. How many other kinds of living things can you see
in the tidal pool?
At low tide, put some mud from a tidal flat on a piece of window
screen and wash it gently with water. Describe what you see.
Look at some dock pilings while the tide is still out. How is
the part that is covered at high tide different from the
continuously exposed part? Describe any living things you see on
the piling.
Put a stick in the sand where you think the high tide will just
reach it but not wash it away. Watch to see what happens.
Using Tide Tables
People who live near oceans can plan exploratory trips to the sea
shore more effectively if they know what the tidal level will be
when they get there. If you want to go to see the animals that
live at the lower level of the intertidal zone then you should
visit the shore when the tides are at their lowest ebb. You can
find this information by getting a tide table for your local
area. Reading a tide table seems difficult at first so practice
on the sample below which was taken from a table constructed for
Breakwater Harbor, Delaware. Tide tables give you six kinds of
information:
OCTOBER 1970
Month
Time Year
Date 16 0236 -0.5 Height of tide
0906 5.6 (2 high tides and
Day of Week TH 1524 -0.4 2 low tides)
2136 4.4
The time is based on the 24 hour where 0000 is 12 o'clock
midnight and 1200 is 12 o'clock noon. So 0236 would be 2:36 AM
and 1524 would be 3:24 PM. The height of the tide is related to
the mean low water level. A number preceded by a minus sign
means that the water level will be below mean low water. No
minus sign indicates the height of the water above mean low
water.
17 0318 -0.3
SA 0954 5.4
1612 -0.2
4.0
18 0406 0.0
SU 1042 5.2
1706 0.1
2312 3.7
19 0454 0.3
MO 1136 4.9
1800 0.4
20 0006 3.4
TU 0548 0.6
1230 4.5
1900 0.7
Using the information above answer the following questions.
1. What day of the week will have the highest tide?
2. On which date will the high tide be the lowest?
3. Which day would be best for looking for organisms farthest
down the beach?
4. Using the 12 hour clock what is the best time to visit the
beach on Sunday during high tide?
Have the children try to make a sand castle that the waves cannot
wash away, using materials from the beach to make it as strong as
possible. Ask them to describe what a wave does to the hole they
dug in the sand.
Make a "Treasure Chest" of things the students found on the
beach. See if they can guess where each kind of treasure came
from -- and how? Make a classroom display of the treasures
collected at the beach. Invite other classes to view the
collection.
Take the class to visit a rocky beach at low tide. Have pieces
of shrimp or fish to feed pieces of food to small crabs or
anemones and ask the children to describe how they responded.
How many other kinds of living things did they see in the tidal
pool?
In the classroom have the students put some sand and some soil in
a container of water and stir it. Let the sand and soil settle
and then ask them to describe which is on top and s\which is on
the bottom. Have them do it again and compare the results. Ask
them why they think layering occurs.
Take the class on a walk along the edge of a marsh. In the
classroom discuss and list the kinds of birds they saw and heard.
How does this list compare with the list they made after their
visit to the beach?
At low tide, have the children put some mud from a tidal flat on
a piece of window screen and wash it gently with water. Have
them describe what remains on the screen. Have them look at dock
pilings while the tide is still out. How is the part that is
covered at high tide different from the part exposed at low tide?
Have them describe any living things they see on the pilings.
At low tide make a map of a small section of coastline. Include
rocks, curves in the beach, and the location of logs and other
things that are lying on the beach. Make another map of the same
place at high tide. Compare the maps.
Have the students put a stick in the sand where they think the
high tide will just reach it but not wash it away. Watch to see
what happens. Can they make a more accurate guess the next time?
In the classroom, put some brine shrimp eggs in fresh water and
some in salt water and have the children observe the containers
for a few days. Ask them where they think brine shrimp live.
Let them use a microscope to observe the brine shrimp when they
start to swim.
Take the class on a trip to a local market. How many kinds of
coastal organisms are for sale? How many people handled them
before they reached the store?
Have the children put a rock in the sand just below where the
waves are washing up on the beach. (Do this only if the waves
are small and not dangerous.) After each wave goes out have them
look at the sand around the rock and describe what is happening.
Have the class observe the groups of small birds that peck the
sand just above the wave line. Have them discuss whether the
group has a leader, what the birds are pecking and how they avoid
getting wet.