Natural biotic communities from Kalbadevi Bay were monitored in microcosms (1-l glass flasks) to test the hypothesis that iron released from ilmenite through microbial action contributes to proliferation of phytoplankton. Microcosms containing ilmenite had significantly higher phytoplankton growth compared with controls containing no ilmenite or those containing only ferrous sulfate. Phytoplankton cell numbers in the ilmenite-supplemented treatment were 20= higher than in controls. The later stages were marked by the dominance of bottom dwelling Nitzschia spp. and Navicula spp. Iron-preferring Eunotia spp. and Pinnularia spp. were also encountered. Hence, increased phytoplankton biomass may be attributable to the steady release of bioavailable iron. We therefore infer that ilmenite mineral might sustain the phytoplankton community in ilmenite-dominated systems. Increases in density and diversity of phytoplankton over time and significant interrelationship between various parameters in the microcosm containing ilmenite indicate that stimulatory effect of iron released from this mineral could be beneficial to the biota in the system.
In the present investigation leaf anatomy of fifteen epiphytic orchids belonging to nine genera viz., Acampe, Aerides, Bulbophyllum, Cottonia, Dendrobium, Pholidota, Porpax, Rhynchostylis, and Smithsonia from Western Ghats, Goa were studied. The study revealed differences with respect to leaf orientation, leaf texture, leaf surface and stomata. The stomatal types reported were anomocytic, tetracytic, pentacytic and paracytic. Maximum stomatal index was reported in Porpax filiformis while it was found to be minimum in Rhynchostylis retusa. Stomatal frequency ranged between 25 mm2 to 76.25 mm2 .
The coastal waters of Goa and Ratnagiri lying on the West coast of India are influenced by terrestrial influx. However, Goa is influenced anthropogenically by iron-ore mining, while Ratnagiri is influenced by deposition of heavy minerals containing iron brought from the hinterlands. We hypothesize that there could be a shift in biological response along with changes in network of interactions between environmental and biological variables in these mining and non-mining impacted regions, lying 160 nmi apart. Biological and environmental parameters were analyzed during pre-monsoon season. Except silicates, the measured parameters were higher at Goa and related significantly, suggesting bacteria centric, detritus-driven region. At Ratnagiri, phytoplankton biomass related positively with silicate suggesting a region dominated by primary producers. This dominance perhaps got reflected as a higher tertiary yield. Thus, even though the regions are geographically proximate, the different biological response could be attributed to the differences in the web of interactions between the measured variables.
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