Driving forces of Antarctic krill abundance

Summary

The study developed a comprehensive modeling approach using 27 years of Palmer Long-Term Ecological Research data to identify key environmental drivers of Antarctic krill population dynamics. The research revealed that krill recruitment is controlled by complex interactions between chlorophyll concentrations, sea surface temperature, ice coverage, climate indices (SAM, ENSO), and critically, intraspecific competition between different age classes. The study found evidence of niche separation between larval and juvenile krill, where environmental conditions favoring one life stage may negatively impact another. The research supports that intercohort competition for shared resources drives krill population cycles and emphasizes the importance of including this competition in longer-term forecasting models.

Key Findings

Larval recruitment driven by both competition among age classes and chlorophyll levels

Milder ice and temperature conditions in spring/summer favor reproduction and early larval survival

Heavier ice and colder temperatures in winter benefit both larvae and juveniles

Evidence of niche partitioning between larvae and juveniles - factors favoring one stage may harm the other

Intraspecific competition essential for longer-term forecasts but not necessary for single-year models using field data

Climate indices (SAM, ENSO) have opposing correlations with larval vs. juvenile survival

Top-down control of phytoplankton resources by krill populations confirmed

Abstract

Antarctic krill, crucial to the Southern Ocean ecosystem and a vital fisheries resource, is endangered by climate change. Identifying drivers of krill biomass is therefore essential for determining catch limits and designating protection zones. We present a modeling approach to pinpointing effects of sea surface temperature, ice cover, chlorophyll levels, climate indices, and intraspecific competition. Our study reveals that larval recruitment is driven by both competition among age classes and chlorophyll levels. In addition, while milder ice and temperature in spring and summer favor reproduction and early larval survival, both larvae and juveniles strongly benefit from heavier ice and colder temperatures in winter. We conclude that omitting top-down control of resources by krill is only acceptable for retrospective or single-year prognostic models that use field chlorophyll data but that incorporating intraspecific competition is essential for longer-term forecasts. Our findings can guide future krill modeling strategies, reinforcing the sustainability of this keystone species.

Published in

Science Advances

2023

Authors

Alexey Ryabov, Uta Berger, Bernd Blasius, Bettina Meyer

Institutions

Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research Dresden University of Technology Carl Von Ossietzky University Oldenburg Helmholtz Institute for Functional Marine Biodiversity (HIFMB)

Methods

Biological sampling DataField

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