Oceanic frontal divergence alters phytoplankton competition and distribution

TL;DR

This study investigates how submesoscale oceanic flow divergence influences phytoplankton competition and distribution, revealing that flow patterns can cause significant regional variability in community composition.

Contribution

It combines observations, simulations, and theory to demonstrate that oceanic divergence at submesoscales affects phytoplankton ecology and community structure.

Findings

Flow divergence can alter phytoplankton competition within hours to days.

Regions of positive divergence favor local phytoplankton populations.

Community composition can vary by up to 20% due to flow divergence.

Abstract

Ecological interactions among phytoplankton occur in a moving fluid environment. Oceanic flows can modulate the competition and coexistence between phytoplankton populations, which in turn can affect ecosystem function and biogeochemical cycling. We explore the impact of submesoscale velocity gradients on phytoplankton ecology using observations, simulations, and theory. Observations reveal that the relative abundance of Synechoccocus oligotypes varies on 1--10 km scales at an ocean front with submesoscale velocity gradients at the same scale. Simulations in realistic flow fields demonstrate that regions of divergence in the horizontal flow field can substantially modify ecological competition and dispersal on timescales of hours to days. Regions of positive (negative) divergence provide an advantage (disadvantage) to local populations, resulting in up to ~20% variation in community composition in our model. We propose that submesoscale divergence is a plausible contributor to observed taxonomic variability at oceanic fronts, and can lead to regional variability in community composition.