Remote sensing of zooplankton swarms

Sünnje L Basedow,David Mckee,Emilia Trudnowska,Einar Skarstad Egeland,Malin Daase,Astthor Gislason,Stig Falk-Petersen,Ina Lefering,Marvin Choquet

doi:10.1038/s41598-018-37129-x

Abstract

Zooplankton provide the key link between primary production and higher levels of the marine food web and they play an important role in mediating carbon sequestration in the ocean. All commercially harvested fish species depend on zooplankton populations. However, spatio-temporal distributions of zooplankton are notoriously difficult to quantify from ships. We know that zooplankton can form large aggregations that visibly change the color of the sea, but the scale and mechanisms producing these features are poorly known. Here we show that large surface patches (>1000 km2) of the red colored copepod Calanus finmarchicus can be identified from satellite observations of ocean color. Such observations provide the most comprehensive view of the distribution of a zooplankton species to date, and alter our understanding of the behavior of this key zooplankton species. Moreover, our findings suggest that high concentrations of astaxanthin-rich zooplankton can degrade the performance of standard blue-green reflectance ratio algorithms in operational use for retrieving chlorophyll concentrations from ocean color remote sensing.

Highlights

Remote sensing of ocean color has led to major advances in understanding ocean-wide phytoplankton dynamics by providing much greater temporal and spatial coverage than is possible by ship-based sampling
By pairing satellite images with high-resolution in situ zooplankton data, and with detailed measurements of optical properties of seawater and of Calanus spp. at oceanographic stations, we aim to establish the potential for remote sensing of this copepod
Genetic analyses confirmed that C. finmarchicus was the dominant Calanus species in the patch, with a few individuals of the closely related C. glacialis identified at stations 6 (2 ind.) and 7 (1 ind.)

Summary

Introduction

Remote sensing of ocean color has led to major advances in understanding ocean-wide phytoplankton dynamics by providing much greater temporal and spatial coverage than is possible by ship-based sampling. Due to its large biomass and high lipid content this species is the principal prey for some of the world’s largest fish stocks, such as larvae of Northeast Arctic cod (Gadus morhua) and adult Norwegian spring spawning herring (Clupea harengus)[8]. It is important for the transfer of energy to most marine animals at higher trophic levels throughout the ecosystem[9]. By pairing satellite images with high-resolution in situ zooplankton data, and with detailed measurements of optical properties of seawater and of Calanus spp. at oceanographic stations, we aim to establish the potential for remote sensing of this copepod

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Conclusion