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Global climate change affects the oceanographic features and distribution of marine fishes as they are poikilothermic animals. Study of oceanographic variables in a localized region is more relevant in the context of ecological responses rather than global or continental variations. In this study, time series analysis of chlorophyll-a concentration (Chl-a) in sea water and sea surface temperature (SST) was performed separately for southern, middle and northern stratum along south-west coast of India using various statistical tools. The SST showed an increasing trend along the entire south-west coast of India after the year 1995. The northern and southern stratum of south-west coast were highly influenced by rising SST, whereas middle stratum in present scenario showed stable conditions in terms of Chl-a concentration. The study provides a baseline information about changing patterns of oceanographic features along the south-west coast of India giving a better understanding of changing global climatic conditions in coastal ecosystems. [ABSTRACT FROM AUTHOR]

The landing of Indian oil sardines, Sardinella longiceps Valenciennes, 1847, along the southwest coast of India is highly variable. A few physical parameters and processes correlated with sardine landing could not establish a flawless connection and explain the phenomena of interannual variability. Earlier research has indicated that the probable appearance and disappearance of sardines is an active movement in search of food and favourable conditions. But no specific study has been carried out to explain the variability of sardine catch based on chlorophyll availability on a synoptic scale. An attempt is made in this study to correlate variability in chlorophyll a with sardine landings along the waters of the southwest coast of India. We have estimated monthly averaged surface phytoplankton biomass along the waters of the southwest coast of India from the shoreline up to the 200-m isobath for 10 years from SeaWiFS ocean-colour data. This estimation is compared with the biological calendar of Indian oil sardines. The average chlorophyll a for the bloom initiation month (1998-2006) matches very well with oil sardine landings. The results imply that the concentration of chlorophyll during the bloom initiation month can be used to assess the quantity of fish that recruit into the population. Finer scale spatial variations in the chlorophyll along the coastal waters help in deciphering the migratory pattern of sardines during their active breeding phase. This study shows that 39% of interannual variability in fish landings is related to availability of chlorophyll a during the bloom initiation month. [ABSTRACT FROM AUTHOR]

Vibrio cholerae, the bacterium responsible for the disease cholera, is a naturally-occurring bacterium, commonly found in many natural tropical water bodies. In the context of the U.N. Sustainable Development Goals (SDG) targets on health (Goal 3), water quality (Goal 6), life under water (Goal 14), and clean water and sanitation (Goal 6), which aim to "ensure availability and sustainable management of water and sanitation for all", we investigated the environmental reservoirs of V. cholerae in Vembanad Lake, the largest lake in Kerala (India), where cholera is endemic. The response of environmental reservoirs of V. cholerae to variability in essential climate variables may play a pivotal role in determining the quality of natural water resources, and whether they might be safe for human consumption or not. The hydrodynamics of Vembanad Lake, and the man-made barrier that divides the lake, resulted in spatial and temporal variability in salinity (1–32 psu) and temperature (23 to 36 °C). The higher ends of this salinity and temperature ranges fall outside the preferred growth conditions for V. cholerae reported in the literature. The bacteria were associated with filtered water as well as with phyto- and zooplankton in the lake. Their association with benthic organisms and sediments was poor to nil. The prevalence of high laminarinase and chitinase enzyme expression (more than 50 µgmL−1 min−1) among V. cholerae could underlie their high association with phyto- and zooplankton. Furthermore, the diversity in the phytoplankton community in the lake, with dominance of genera such as Skeletonema sp., Microcystis sp., Aulacoseira sp., and Anabaena sp., which changed with location and season, and associated changes in the zooplankton community, could also have affected the dynamics of the bacteria in the lake. The probability of presence or absence of V. cholerae could be expressed as a function of chlorophyll concentration in the water, which suggests that risk maps for the entire lake can be generated using satellite-derived chlorophyll data. In situ observations and satellite-based extrapolations suggest that the risks from environmental V. cholerae in the lake can be quite high (with probability in the range of 0.5 to 1) everywhere in the lake, but higher values are encountered more frequently in the southern part of the lake. Remote sensing has an important role to play in meeting SDG goals related to health, water quality and life under water, as demonstrated in this example related to cholera. [ABSTRACT FROM AUTHOR]