Ecological responses of autotrophic microplankton to the eutrophication of the coastal upwelling along the Southwest coa
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RESEARCH ARTICLE
Ecological responses of autotrophic microplankton to the eutrophication of the coastal upwelling along the Southwest coast of India Jyothibabu Retnamma 1 & Karnan Chinnadurai 1 & Jagadeesan Loganathan 1,2 & Arunpandi Nagarathinam 1 & Parthasarathi Singaram 1 & Albin Konnakkamannil Jose 1 Received: 14 June 2020 / Accepted: 20 October 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The primary ecological effects of the eutrophication of upwelling in the nearshore waters are the triggering and sustenance of phytoplankton (diatom) blooms. Here, we present the changes in the morphological characteristics and body size of microautotrophs associated with the nutrient enrichment of coastal upwelling along the southwest coast of India. The FlowCAM data of microautotrophs representing two time series locations in the coastal environment along the southwest coast of India at 18 weekly/biweekly frequencies showed the following features. The most significant response of the microautotrophs to the eutrophication associated with coastal upwelling during the Southwest Monsoon (June–September) was an increase in their mean bio-volume, either by increasing the individual cell size or by forming large colonies. During the Southwest Monsoon, large colonies of Thalassiosira (~ 8 cells/colony), Thalassionema (> 16 cells/colony), and Asterionellopsis (> 8 cells/colony) become very abundant. Streptotheca formed large mat-like colonies (av. 192350 ± 348 μm3/individual), and Fragilariopsis grew as very long ribbons (av. 272997 ± 5071 μm3/individual). Large-sized Chaetoceros (av. 45715 ± 1273 μm3/individual) with longer setae were also plentiful during the Southwest Monsoon. All these changes in the morphology and life forms of microautotrophs would help them to rapidly assimilate nitrate under turbulent conditions during the Southwest Monsoon. Keywords Plankton . Phytoplankton . Upwelling . Southeastern Arabian Sea
Introduction The Southeastern Arabian Sea (SEAS) is bounded on its east by the southwest coastline of India, which is known for its higher pelagic fishery resources compared with the rest of the Indian coast (Madhupratap et al. 1994, 2001; Jyothibabu et al. 2008, 2010). The coastal upwelling is considered the primary reason behind a rich stock of fish, especially small pelagic fishes, along the southwest coast of India during the Southwest Monsoon (Banse 1959; Jyothibabu et al. 2008; Responsible Editor: Vedula VSS Sarma * Jyothibabu Retnamma [email protected] 1
CSIR-National Institute of Oceanography, Regional Centre, Kochi, India
2
CSIR-National Institute of Oceanography, Regional Centre, Visakhapatnam, India
Gupta et al. 2016; Karnan et al. 2017a). Upwelling along the southwest coast of India enriches the coastal waters with a high concentration of essential nutrients facilitating an increase in phytoplankton biomass (Bhattathiri et al. 1996; Qasim 1982; Madhupratap et al. 1990; Jyothibabu et al. 2008; Karnan et al. 2017a; Karnan et al. 2020). This enhancement in autotrophs b
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