Importance of ice algae and phytoplankton detritus as food sources for three contrasting macrofaunal communities of the Canadian Arctic

BRAVO GONZALO; GEORGEOS KAZANIDIS; PHILIPPE ARCHAMBAULT; JAVIER CIANCIO; SOLVEIG BOURGEOIS; CHRISTIAN NOZAIS; URSULA WITTE; A MAKELA

Quebec

Conferencia; Artic Change; 2017

Phytodetritus are considered as one of the most mainfood supplies for deep-sea fauna. In Arctic ecosystems, sea ice algae andphytoplankton are known as the main primary producers that reaches theseafloor. So far, little is known about the responses of benthic macrofaunafacing future changes regarding quantity and quality of food reaching theseafloor inflicted by sea ice reduction. We conducted on board pulse-chaseexperiments on sediment cores collected from the Baffin Bay, the Amundsen Gulf,and the Beaufort Sea, Canada to investigate the macrofauna response to asimulated food pulse of primary producers. Dual-labelled (13C and 15N)diatoms Thalassiosira nordenskioeldii(Phytoplankton treatment) and Synedrahyperborea (ice algae treatment) were added separately to intact sedimentcores and incubated for four days to compare results from different foodsupplies. Benthic community structure varied between regions and the totaluptake of both sources was greater in Baffin Bay where the highest biomass wasregistered and where more than 70% of the biomass was represented by facultative filter feeder-surface/depositfeeders. In all the regions, phytoplanktonwas slightly more consumed, however no significant differences in the biomass-specificuptake of ice algae and phytoplankton were observed, suggesting that both foodsources are consumed in  similar proportions.