1 research outputs found
Response of coastal phytoplankton to upwelling induced hydrological changes in the Alappuzha mud bank region, Southwest coast of India
The response of phytoplankton community to the co-existing events of coastal upwelling and mud banks in the nearshore waters of Alappuzha (15 m depth), located in the
southwest coast of India from April to November 2016, is described based on size-fractionated
phytoplankton biomass (chlorophyll a), primary production and community composition. The
study region exhibited well-distinct spatio-temporal hydrological changes because of the influence of wind-driven coastal upwelling, prevalent during the southwest monsoon (SWM) period.
However, the formation of mud banks, in addition to coastal upwelling, was observed at station
M2, which facilitated the substantial increase of water column turbidity and inorganic nutrients (ammonium, phosphate, and silicate) during and after the peak SWM period compared to
the non-mud bank reference stations (M1 and M3). The prevailing hydrological changes were
complemented the corresponding phytoplankton productivity patterns, in which profound domination of nanophytoplankton (2—20 μm) chlorophyll a and primary production was observed
throughout the study region, irrespective of seasons. The SIMPER analysis, based on phytoplankton (mostly >20 μm) species composition data (microscopy), revealed the formation of
certain characterizing species, mainly comprised of diatoms and dinoflagellates. The consistent predominance of the nanophytoplankton, established under variable hydrological scenarios, showed that the inorganic nutrient (specifically ammonium) availability was instrumental in
defining the widespread growth of nanophytoplankton community compared to the prevailing
light levels. The present study thus revealed that even the small-sized phytoplankton community could survive in the nutrient-enriched coastal waters, characterised by the co-existing
upwelling and mud banks