Mechanistic model identifies increasing light availability due to sea ice reductions as cause for increasing macroalgae cover in the Arctic

A1 Journal article (refereed)

Internal Authors/Editors

Publication Details

List of Authors: Scherrer K. J. N., Kortsch S., Varpe Ø., Weyhenmeyer G. A., Gulliksen B., Primicerio R.
Publication year: 2019
Journal: Limnology and Oceanography
Volume number: 64
Issue number: 1
Start page: 330
End page: 341


In the Arctic, rising seawater temperatures and increasing underwater light caused by reductions in sea ice
cover are expected to change the structure of arctic marine communities. Substantial, sometimes sudden,
increases in macroalgal productivity and biomass have already been observed in arctic rocky bottom communities. These macroalgal responses have been attributed to increasing temperature and light, but the relative
importance of the suggested drivers of change has not yet been assessed. In this study, we used a mechanistic
competition model to unravel the effects of temperature and light on benthic community structure and algae
dominance, focusing on key algae species: red calcareous algae and macroalgal fronds. We find that light is the
primary driver of increases in macroalgal coverage, whereas increased seawater temperature plays a secondary
role. Shifts leading to macroalgae dominated communities may be mediated by competitive interactions, and
are likely due to three light-related processes: earlier sea ice break-out at high latitudes can result in an exponential increase in the cumulative amount of light that enters the water column during a year; threshold effect in
light requirements for algal growth; and light requirements of calcareous algae being substantially lower than
those of macroalgae. With continued warming, our modeling results suggest that reduced sea ice coverage and
increased light availability will favor dominance of macroalgae, which due to their key ecological role are
expected to alter the structure and functioning of arctic rocky bottom ecosystems.

Last updated on 2020-03-08 at 05:16