Hydrological regulation of Vibrio dynamics in a tropical monsoonal estuary: a classification and regression tree approac
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RESEARCH ARTICLE
Hydrological regulation of Vibrio dynamics in a tropical monsoonal estuary: a classification and regression tree approach Kiran Krishna 1
&
Vipindas Puthiya Veettil 1,2 & Abdulaziz Anas 1 & Shanta Nair 3
Received: 25 March 2020 / Accepted: 10 August 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Dynamics of Vibrio populations in aquatic environments are of concern, as they encompass members pathogenic to humans as well as marine flora and fauna. Spatiotemporal distribution of its culturable abundance for a range of physicochemical and biological parameters in the Cochin estuary (CE), one of the largest tropical monsoonal estuary along the southwest coast of India, witnessed a proliferation of this bacterial group (707 ± 196 CFU ml−1) in downstream stations during a relative dry period. The study for the first time employed classification and regression tree (CART) along with multiple linear regression (MLR) based approaches to explore the nonlinear and linear interactions, respectively, among environmental variables regulating Vibrio abundance in CE. Both the techniques were on consensus to ascertain salinity as the primary determinant of Vibrio dynamics, during the entire sampling period regardless of the seasons, viz., dry and wet. Nevertheless, CART outperformed MLR in performance index, suggesting that in a dynamic system like estuaries, usage of the latter is limited by complex nonlinear relationships among environmental variables. According to CART, Vibrio proliferation observed in downstream stations of the estuary (salinity ≥ 13.4 psu) during a relative dry period was driven by eutrophication (dissolved inorganic phosphate ≥ 1.48 μM L−1) associated with reduced flushing resulting in an oxygen-limited environment (dissolved oxygen < 4.56 ml L−1), wherein phytoplankton production diverts to support microbes. Our results imply that anthropogenic activities and sea level rise in future may prompt Vibrio proliferation, to be a concern for public health and impinge on fisheries yield from tropical estuaries. Keywords Classification and regression tree . Estuary . Tropics . Vibrio . Environmental variables . Dynamics
Introduction Estuaries play a major role in the evolution of human civilization. The resources it facilitates like port, fisheries and land and water for agriculture continue to attract a major share of Responsible Editor: Diane Purchase Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11356-020-10486-9) contains supplementary material, which is available to authorized users. * Kiran Krishna [email protected] 1
Regional Centre, CSIR - National Institute of Oceanography, Kochi, Kerala 682018, India
2
National Centre for Polar and Ocean Research, Headland Sada, Vasco-da-Gama, Goa 403804, India
3
CSIR - National Institute of Oceanography, Dona Paula, Goa 403004, India
world population along its coast. As a consequence of this large human settlement and industrial growth around the estuaries, there h
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