Benthic response to water column productivity patterns: Evidence for benthic‐pelagic coupling in the Northeast Water Polynya

Abstract

Polynyas, recurring ice‐free areas amid pack or drift ice, are model systems for predicting the potential productivity of pelagic and benthic communities in polar regions. The Northeast Water Polynya on the northeast Greenland continental shelf and surrounding ice‐covered areas were investigated to address the influence of water column processes on the benthos. We measured infaunal density, polychaete biomass, sediment carbon concentration, and benthic pigment concentration from replicate box cores at 16 stations. Benthic pigment concentration is the most important predictor of infaunal density and polychaete biomass, explaining nearly half of the variance in these variables. Benthic pigment concentrations are strongly related to the concentrations of water column pigments, suggesting that the signal of water column productivity is received on the bottom and transmitted to the fauna. The highest densities and biomass are found near the mouth of the Northern Trough and are probably fueled by biogenic material produced by the developing phytoplankton community as it is advected down the trough. Density and biomass are also generally higher under the ice‐free water of the Northern Trough than under the ice‐covered Southern Trough. This pattern may be explained by greater primary productivity in the Northern than Southern Trough and/or by a decoupling of water column and benthic process by Zooplankton grazing in the south. Sediment organic carbon concentration is between 0.5% and 1.5%, indicating that the sediment is probably not an unusually large carbon sink relative to shelf and deep‐sea systems in temperate and polar regions. These results reinforce an emerging pattern of efficient transfer of carbon from water column to benthos in high latitudes. Owing to the abundance of small‐scale and mesoscale areas of enhanced phytoplankton production in the Arctic (e.g., leads, marginal ice zones), benthic biomass in the Arctic Ocean and surrounding seas may be higher than previously anticipated.