Influence of lateral advection on phytoplankton size-structure and composition in a Mediterranean coastal area

摘要

Phytoplankton size is a significant functional trait affecting many ecological processes and influencing the carbon fate and the trophic regimes of the ecosystems. In this study, we examined the effect of the lateral advection of nutrient-rich Messina Mixed Waters on the phytoplankton size structure and community composition in the euphotic layer of the Gulf of Augusta (Western Ionian Sea) in early autumn. The chlorophyll a concentration ranged from 0.08 to 0.8 mg m(-3) and the phytoplankton abundances ranged from 21 x 10(3) to 245 x 10(3) cells L-1. The size structure of phytoplankton biomass, obtained by sequential filtration of water samples, suggested the dominance of micro-planktonic diatoms in an active Deep Chlorophyll Maximum (DCM) whereas smaller forms were mainly represented by phytoflagellates. A short-term tidal-induced variability of the assemblage structure was observed at a "sentinel" station located at the Gulf shelf-break where lateral advection due to meso-scale dynamics sustained most of the phytoplankton biomass.