Biological activity in the wake of an island close to a coastal upwelling

TL;DR

This study models how hydrodynamic features like wakes and vortices near islands influence plankton activity and primary production, revealing conditions that either block or enhance nutrient transport and promote plankton blooms.

Contribution

It introduces a coupled hydrodynamic-biological model to analyze the impact of island wakes on plankton dynamics near upwelling regions, highlighting mechanisms for nutrient transport and bloom formation.

Findings

Wakes can block nutrient and plankton transport across islands.

High vorticity enhances nutrient transport and primary production.

Plankton blooms can form inside mesoscale vortices acting as biological incubators.

Abstract

Hydrodynamic forcing plays an important role in shaping the dynamics of marine organisms, in particular of plankton. In this work we study the planktonic biological activity in the wake of an island which is close to an upwelling region. Our research is based on numerical analysis of a kinematic flow mimicking the hydrodynamics in the wake, coupled to a three-component plankton model. Depending on model parameters different phenomena are described: a) The lack of transport of nutrients and plankton across the wake, so that the influence of upwelling on primary production on the other side of the wake is blocked. b) For sufficiently high vorticity, the role of the wake in facilitating this transport and leading to an enhancement of primary production. Finally c) we show that under certain conditions the interplay between wake structures and biological growth leads to plankton blooms inside mesoscale hydrodynamic vortices that act as incubators of primary production.