Spring-to-summer changes and regional variability of benthic processes in the western Canadian Arctic

Abstract

Seasonal dynamics in the activity of Arctic shelf benthos have been the subject of few local studies, and the pronounced among-site variability characterizing their results makes it difficult to upscale and generalize their conclusions. In a regional study encompassing five sites at 100-595 m water depth in the southeastern Beaufort Sea, we found that total pigment concentrations in surficial sediments, used as proxies of general food supply to the benthos, rose significantly after the transition from ice-covered conditions in spring (March-June 2008) to open-water conditions in summer (June-August 2008), whereas sediment Chl a concentrations, typical markers of fresh food input, did not. Macrobenthic biomass (including agglutinated foraminifera [500 lm) varied significantly among sites (1.2-6.4 g C m -2 in spring, 1.1-12.6 g C m -2 in summer), whereas a general spring-to-summer increase was not detected. Benthic carbon remineralisation also ranged significantly among sites (11.9-33.2 mg C m -2 day -1 in spring, 11.6-44.4 mg C m -2 day -1 in summer) and did in addition exhibit a general significant increase from spring-to-summer. Multiple regression analysis suggests that in both spring and summer, sediment Chl a concentration is the prime determinant of benthic carbon remineralisation, but other factors have a significant secondary influence, such as foraminiferan biomass (negative in both seasons), water depth (in spring) and infaunal biomass (in summer). Our findings indicate the importance of the combined and dynamic effects of food supply and benthic community patterns on the carbon remineralisation of the polar shelf benthos in seasonally ice-covered seas.

Multivariate benthic ecosystem functioning in the Arctic – benthic fluxes explained by environmental parameters in the southeastern Beaufort Sea

“…In the literature, benthic activity is most often derived from sediment oxygen demand (Graf, 1992;Link et al, 2011;Wenzhöfer and Glud, 2002) and assumed to decrease with increasing depth and distance from the continental source of particles and carbon. However, the heterogeneous pattern of oxygen and nutrient fluxes at the sediment-water interface in the Beaufort Sea emphasizes that benthic remineralisation function is more complex than oxygen fluxes.…”

“…Chl a and phaeopigment concentrations were determined fluorometrically following a modified protocol proposed by Riaux-Gobin and Klein (1993) as described in Link et al (2011): two grams of wet substrate were extracted with 10 mL 90 % acetone (v/v) for 24 h at 4 • C, and the supernatant was measured in a Turner Designs 20 fluorometer before and after acidification. Quantities are expressed as microgram pigment per gram of dry sediment (µg g −1 ).…”

“…As short-term scale we define seasonal to annual timescales and include the parameters sediment surface Chl a concentration and vertical POC export. Results reported from different seasons and years in the Beaufort Sea have shown that sediment Chl a concentration and vertical POC export vary both over seasons and years (Forest et al, 2007;Juul-Pedersen et al, 2010;Link et al, 2011;Morata et al, 2008;Renaud et al, 2007a;Sallon et al, 2011), respectively. This is due to the seasonal and spatial dynamics of primary production and carbon fluxes in the region (Forest et al, 2010;OrtegaRetuerta et al, 2012;Tremblay et al, 2011).…”

“…Their relative importance varies temporally and spatially due to changes in environmental conditions. Thus, organic carbon content of sediments seems less predictive of benthic remineralisation (Rysgaard et al, 1998) than the quantity of fresh organic matter deposited on the seafloor (Chang and Devol, 2009;Link et al, 2011). Also, historical input of organic matter, ambient water oxygen concentration and porosity modifies the oxygen penetration of sediments and therefore its reactivity (Gobeil et al, 2001).…”

Introduction to the special issue on the biology of the circumpolar flaw lead (CFL) in the Amundsen Gulf of the Beaufort Sea (Arctic Ocean)

“…• Despite-or perhaps because of-the strong attenuation of particulate organic Xuxes to the seaXoor in this region, algal blooms related to early sea-ice retreat were critical to the benthos, with the initial size of the benthic community at that time being an additional determinant of the fate of carbon at the seaXoor (Link et al (2011, this special issue) on "Spring-to-summer changes and regional variability of benthic processes in the western Canadian Arctic").…”