Biochemical Composition of Seston Reflecting the Physiological Status and Community Composition of Phytoplankton in a Temperate Coastal Embayment of Korea

Riaz Bibi,Goutam K Kundu,Changseong Kim,Chang-Keun Kang,Dongyoung Kim,Jaebin Jang,Hee Yoon Kang

doi:10.3390/w13223221

Riaz Bibi, Goutam K Kundu + Show 5 more

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https://doi.org/10.3390/w13223221

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Abstract

The biochemical composition of seston along a salinity gradient were examined in the low-turbidity, temperate, estuarine embayment, Gwangyang Bay in Korea. Seasonal variations in sestonic protein (PRT), carbohydrate (CHO), and lipid (LIP) concentrations were analyzed to assess the effects of physiological status and taxonomic composition of phytoplankton. The concentrations of biochemical compounds displayed a close relationship with chlorophyll a (Chla). PRT:CHO ratios were high (>1.0) in the estuarine channel in warmer months and in whole bay in February, indicating a N-replete condition for phytoplankton growth. High CHO:LIP ratios (>2.5) in the saline deep-bay area during the warmer months (>2.0) emphasized the importance of temperature and photoperiod over nutritional conditions. The low POC:Chla (<200), molar C:N (~7) ratios, and biopolymeric carbon concentrations coupled with high primary productivity indicated a low detrital contribution to the particulate organic matter pool. Diatom dominance throughout the year contributed to consistently high carbohydrate concentrations. Furthermore, generalized additive models highlighted that phytoplankton community (i.e., size) structure may serve as an important descriptor of sestonic biochemical composition. Collectively, our results suggest that physiological and taxonomic features of phytoplankton play prominent roles in determining the biochemical composition of seston, supporting the fact that the ecosystem processes in Gwangyang Bay are largely based on phytoplankton dynamics.

Highlights

IntroductionEstuaries form transition zones between riverine and marine biomes [1]
Introduction published maps and institutional affilEstuaries form transition zones between riverine and marine biomes [1]
To characterize the relationship between the biochemical composition of seston and phytoplankton groups, in particular to determine whether the taxonomic composition of phytoplankton plays a role in the observed trends in biochemical composition, we examined the changes in sestonic carbohydrate, protein, and lipid concentrations and their ratios according to phytoplankton size composition using generalized additive models (GAMs; [58])

Summary

Introduction

Estuaries form transition zones between riverine and marine biomes [1]. Because of the mixing of freshwater and seawater, estuaries are characterized by pronounced gradients of physical, biogeochemical, and biological processes [2]. Spatiotemporal variabilities in these processes strongly influence the biological community characteristics of the estuarine–marine continuum [3,4,5]. Seston is composed of suspended living and dead material, and plays a vital role in the biogeochemical cycling of materials in estuarine and marine ecosystems [6]. Despite the large variety of processes (e.g., tidal resuspension, riverine loads, and turbidity maximum zone) that control the quantity and iations

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