CHEMTAX-assisted insights into ecological responses of non-dominant phytoplankton to climate and eutrophication in a temperate estuarine bay

Le résumé fourni par la source

Phytoplankton community dynamics are fundamental to the functioning of coastal ecosystems. In temperate coastal waters, however, research has largely concentrated on dominant taxa such as diatoms and dinoflagellates, often underrepresenting smaller groups like cyanobacteria and cryptophytes in assessments of community structure. To address this gap, we investigated seasonal variations in the biomass composition of major phytoplankton groups in Laizhou Bay, a temperate estuarine ecosystem increasingly threatened by nutrient pollution and harmful algal blooms (HABs). Results show that while diatoms and dinoflagellates remained the primary contributors to total chlorophyll a (Chl-a), accounting for 32 – 56 % and 6 – 23 % respectively, non-dominant groups also played substantial roles (21 – 67 %). Cyanobacteria contributed up to 29 % of Chl-a in summer and 17 % in autumn, with peak Chl-a concentrations reaching 2.6 μg L −1 in autumn 2020. Cryptophytes accounted for up to 25 % of Chl-a in spring. Notably, non-dominant taxa comprised over 70 % of Chl-a in the southern and eastern bay during summer. These groups exhibited distinct spatiotemporal patterns, shaped by interactions among nutrient availability, temperature gradients, and salinity fluctuations. Our findings suggest that anthropogenic nutrient loading and climate-driven warming jointly influence phytoplankton community structure, with smaller taxa benefiting under nutrient-stressed and warmer conditions. This study underscores the importance of CHEMTAX in understanding the dynamics of non-dominant phytoplankton groups, with implications for ecological risk assessment and HAB warning systems.

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