ENVIS Technical Report: 25

The term ‘bioindicator species’ was coined by Kolkwitz and Marsson in 1908 and 1909 regarding the impact of organic pollution (i.e. sewage) on aquatic organisms (Rosenburg & Resh 1996). Bioindicator literature has since developed to include the concepts of population and biodiversity indicators. Indices of Biotic Integrity and other similar multi metric concepts have developed since the 1970’s as methods to quantitatively assess environmental condition through habitat indicators. Biological indicators are currently used and promoted by numerous conservation agencies as a means to monitoring and assessing human impacts on environments, including the World Conservation Union (IUCN), World conservation Monitoring Center (UNEP), U.S.Environmental Protection Agency (US EPA), as well as the Nature Conservancy, World Wide Fund for Nature (WWF), Friends of the Earth (FOE), and Greenpeace (IUCN 1989 ⁷⁰, US EPA 2002a ⁷¹, UNEP 2002 ⁷²).

It has been established that environmental disturbances induce changes in the structure and function of biological systems. The benthic flora and fauna of freshwaters has been the subject of intensive ecological research because they play an important role as indicators of aquatic pollution (Wilhm ⁷³, 1975; Tudorancea ⁷⁴ et al., 1979; James ⁷⁵, 1979; Mason ⁷⁶, 1981 and Olivieri ⁷⁷, 1982). The benthic community structure represents an integral measure of autotrophic and heterotrophic process in lakes, and reflects disturbances in these processes. A better understanding of the effects of pollution is obtained when biological data are correlated with the physical and chemical parameters. However, biological indicators provide direct evidence of the effects of pollution, whereas physical and chemical data provide only indirect evidence. No single species by itself will indicate the full scope of potential hazards coincident with the various uses of water or provide all the information for an adequate evaluation.

Viner A. B ⁷⁸ gives an account of some biological features associated with the hydrological and morphological characteristics of Lake Volta, which have already been described (Viner, 1969). It discusses some biological effects of water mixing and morphometry of lake Voltas. Both the zooplankton and the phytoplankton showed relationships to the physico-chemical regime of Lake Volta. Very little plankton was found below the thermoclines and oxygen discontinuities whenever they existed, even though the temperature drop at the thermal discontinuity was always very small (approx. 0.5°C). The preliminary survey of the phytoplankton in Lake Volta has shown that there was some relationship between the morphometry and degree of stratification.

Tariq A. Khan ⁷⁹ (2003) recorded bi-monthly, November 1999–September 2001, major biological parameters of four permanent (Lake Colac, Modewarre, Bolac and Tooliorook), shallow and slightly saline lakes in the volcanic plains of western Victoria, Australia. Chlorophyll a concentration ranged from 3–29 μg l−1 with peaks in autumn. Phytoplankton taxa recorded were diverse, with Chlorophyta and Bacillariophyta being common. Cyanobacterial blooms were recorded mostly in summer. Zooplankton abundance in the lakes ranged from 12–368 individuals per litre. Rotifera dominated Lake Bolac, Copepoda dominated Lake Modewarre and they co-dominated Lake Colac and Tooliorook. A decline in the abundance of zooplankton in summer in Lake Modewarre was attributed to predation by high number of exotic larval carp at that time of the year. A total of 25 benthic macroinvertebrate taxa were recorded from Lake Colac, 30 from Modewarre, 22 from Bolac and 35 from Tooliorook. Twenty-one of the 45 taxa identified occurred in at least three lakes. Nine of the 12 taxa that occurred in only one lake were from Lake Tooliorook. Physico-chemical parameters revealed that the lakes were homogenous with few differences between sites within lakes. Of the four lakes, Lake Modewarre had the highest salinity of 8 ppt with weak seasonal fluctuations in salinity in all the lakes. All the lakes were turbid (turbidity range 30–659 NTU), with low light penetration (suspended solids range 23–465 mg l−1) and low Secchi depth (Secchi depth range 7.7–89 cm). pH of the lakes varied between 8.2 and 9.3 with low seasonal variations, indicating well buffered waters. Based on nutrient status, lakes were classified as eutrophic to highly eutrophic with higher nutrient concentrations. Nitrogen was limiting in one lake (Lake Colac) and phosphorus in the other three lakes. The study suggested that meteorological events probably influenced the physico-chemical parameters of these lakes strongly.

Biswas ⁸⁰ (1992) discusses relationship between the temperature and the density of phytoplankton in Ogelube a tropical African oligotrophic lake. Desmids dominated the phytoplankton during the warmest period between harmattan and rainy seasons. They declined with a high death rate as the increasing rains cooled the lake, shifting dominance successively to various algae other than desmids, regardless of any hydrological changes. Cooling continued as harmattan advanced and the resultant lowest temperature caused phytoplankton minimum probably by inhibiting vegetative increase rather than by killing. Desmids dominated phytoplankton rapidly arose to peak as water warmed up, suggesting the importance of temperature. Presence of desmids in all depths throughout the period bore no evidence of stratification.

Roasas ⁸¹ et al. (1985) evaluated the impact of the urban development and the discharges of liquid and solid wastes on water quality by biological methods using bacteria and macroinvertebrates as indicators, as well as physicochemical parameters in Lake Patzcuaro, which is one of the most important lakes in Mexico. The bacteriological determinations showed critical areas near the two main villages, Patzcuaro and Janitzio. The bacterial investigations indicated significant amounts of animal excreta throughout the lake. In areas of less urban influence, abundance of immersed vegetation with the benthic macroinvertebrate community presented high biotic diversity (> 2), and equitability indices (> 0.6). At the most polluted station (8), Oligochaetes, which are tolerant to organic matter, comprised 94% of the organisms. Physico-chemical characteristics are similar in the lake, except at station 8 where the lowest DO levels, highest ammonia and phosphorus concentrations were registered. This area, adjacent to a fish processing plant, is affected by domestic and industrial wastewater discharges. The authors concluded based on the results that the lake has been moderately polluted.

Rosas I ⁸². et al. (1993) carried out an evaluation of water quality and phytoplankton composition position in order to determine the trophic conditions of Lake Patzcuaro (2035 m above sea level), a high altitude tropical lake in Mexico. Temperatures ranged from 15 to 23°C. Total phosphorus and inorganic nitrogen showed a seasonal variation; highest values coincided with the rainy season (0·48 and 2·1 mg litre−1, respectively). Dissolved oxygen ranged from 2 to 7·9 mg/L at the surface and from 0·6 to 7·3 mg/L on the bottom, the lowest values being found in shallow zones. Average transparency varied from 0·62 to 1·4 m of Secchi depth. Rainfall was a primary factor in seasonal variability as it influenced both physical and biological conditions by contributing to the transport and deposition of silt, which mixed with sinking algal cells. The composition of the surface phytoplankton comprised a total of 49 species. General seasonal patterns of dominance alternated in a sequence beginning with Bacillariophyta, through Chlorophyta to Cyanophyta. Diatoms, the dominant group from February to early June, included Melosira granulata, Stephanodiscus sp., Synedra sp. and Fragilaria sp. During the rainy season (late June to September), Microcystis aeruginosa, Oscillatoria sp., Anabaena sp., Merismopedia sp., Crucigenia cuadrata, Oocystis lacustris, Selenastrum gracile, Mallomonas sp. and Tetraediella sp. were important. Melosira granulata was present throughout the period of study. Spatial and temporal variability in both physical and biological conditions made it difficult to assign a specific trophic state to Lake Patzcuaro. Nevertheless, the analysis of the algal community indicated a generally mesotrophic condition.

Liliana Favari ⁸³ et al. studied the limnology, plankton, and biomagnification of pesticides at Ignacio Ramírez (IR) reservoir (Mexico). The reservoir is located in central Mexico, in an agricultural zone with high soil erosion. The dominant group of phytoplankton was Bacillariophyta (20–85%) in May, Cyanophyta (22–65%) in September, and Cyanophycean (10–65%), Chlorophycean (10–60%), and Bacyllariophycean (5–80%) species in March. The zooplankton were dominated by cladoceran species (40–70%). Organochlorine and organophosphate insecticides were bioconcentrated (2- to 10-fold) from water to algae, 10- to 25-fold in zooplankton, and 8- to 140-fold in fish. The authors’ suggested that the bioaccumulation of these contaminants in fish and the potential for biomagnification in humans are perceived as threats.