Algal Analysis

Analysis of macrophytes samples with the help of standard morphological keys indicate the presence of 24 algal species (Table 3.3) belonging to four taxonomic divisions, Cyanobacteria (1), Bacillariophyta (6), Chlorophyta (14), and Euglenophyta (3). Sampling location wise, algal species are:

• Site 1 recorded the highest diversity (>16 species) and majority were green algae (10). In all the three sites the chlorophycean members dominated over the members of other classes. These include Cosmarium spp., Kirchneriella spp., and  Staurastrum spp.
• Site 2 has higher diversity of the euglenophycean members and the bacillariophycean members, attributable to the presence of higher organic matters that correlates with the higher COD and TDS values. Abundance of eugleophytes is an indication of the nutrient enrichment with the input of higher organic matter. These include  chrolophycean members the Staurastrum spp.  
• Site 3 with higher DO values has more than 12 algal sp. and were dominated by Xanthidium sp. (which are absent in the other sampling sites).

Apart from these macro algal species were also identified and analysed (figure 3.5-3.7). Figure 3.8 elucidates the composition - green algae (~58 %) diatoms (25 %) > euglenophytes (13 %) > blue green algae (4 %) during the study. Figure 3.9 provides select algal microscopic illustrations.

Filamentous macro algae in the peripheries of the pond were Oscillatoria sp. This species were mostly found along with organic debris and sludge masses floating on the top trapping air bubbles and are the most common bloom forming algae in the nutrient enriched waters. Most interestingly these species were also observed entangling the aquatic hydrophytes like Vallisneria spiralis, due to which the long leafs of the plant were bundled together, obstructing sunlight that inhibit photosynthesis. Further more the submerged aquatic plants also uptake nutrients through leafs, and the presence of dominant cyanophycean members such as Oscillatoria hampers the growth and productivity. Pseudoanaebaena species were also observed associated with some of the Oscillatoria clumps near the shore lines.

The surface of the pond in the deeper regions were mostly occupied by a composite of green algae Spirogyra sp. (known as pond silk), water lily with intermittent Limnophylla sp. This forms a network like structure floating on the top of the pond over which small Utricularia sp. flowers were observed. This mesh restricts the penetration of sunlight and might also limit air diffusion creating problem to the fish and aquatic biota (Figure 3.7).

Figure 3.6:  Filamentous algae in the temple pond

High percentage composition of Cyanophyceae is indicative of eutrophic water (Lund 1965). Percentage contribution of Cyanophyceae in Kotiteertha pond shows that the nutrient levels are low and this could be an oligotrophic state. Dominance of algal genera like Euglena, Navicula, Nitzschia, Microcystis, Oscillatoria and Scenedesmus are indicative of organically pollution in waters, supported (Palmer, 1969). However the present study recorded abundant Oscillatoria members indicative of organic pollution. The epiphytic and epilithic algae may form excellent indicators of water pollution (Vyas and Kumar, 1968). In the present study the occurrence of spirogyra (mostly epilithic) and Oscillatoria (mostly epiphytic) were observed. Ramachandra et al., 2015 reported that Microcystis aeruginosa can be used as the best single indicator of pollution. However in the present study Microcystis sp. were not observed.

Figure 3.8: Algal composition a) Overall, b) Site 1, c) Site 2 and d) Site 3

Figure 3.9: Microscopic images of some selected algae found in various sites of the temple pond

Table 3.3: Algal species of Gokarna temple pond, Kotiteertha