Measuring spatial and temporal benthic community change in Frobisher Bay, southern Baffin Island

Abstract

Benthic communities may be significantly impacted by long-term change as a result of anthropogenic or natural stressors. Arctic coastal regions are particularly at risk as seasonal sea ice retreats and previously ice covered regions open. Characterizing marine faunal biodiversity in Arctic regions through predictive habitat mapping is a crucial step towards protecting sensitive Arctic marine ecosystems. Benthic habitat maps provide a snapshot of the existing biological and physical environment while also providing a baseline of knowledge for long-term monitoring. Resampling of historical sites in Frobisher Bay, a large macro-tidal bay in southern Baffin Island, offers a unique opportunity to study temporal and spatial change in benthic communities. Benthic infaunal samples were initially collected at twelve long-term ecology (LTE) stations using a grab sampler in inner Frobisher Bay from 1967-1976, providing seasonal and inter-annual benthic infaunal sample data for this region. In 2015 and 2016, the same LTE stations plus an additional eighteen stations were sampled nearby to a maximum water depth of 100 metres using a grab sampler, box core, and underwater towed video camera system. Benthic faunal samples and sediment samples collected for grain size analysis will be used to ground-truth multibeam bathymetry and backscatter data acquired between 2012 and 2016. Habitat maps produced from infaunal sample data will offer a visual depiction of current spatial community assemblages and allow for an assessment of spatial change based on historical infaunal community composition. This analysis will provide context for assessing temporal change in benthic communities in Frobisher Bay. Polychaetous annelids were the dominant taxa observed at all stations sampled from 1967-1976. Other dominant taxa observed at stations near Iqaluit included oligochaetes, bivalves, and gastropods. Amphipods, ostracods and priapulids were observed at only a few of these stations in high densities. Ostracods were the second most dominant taxa at stations located to the south-east of Iqaluit. Amphipods, bivalves, cumaceans, pycnogonids, and tanaids varied among stations as the third most dominant taxon. Polychaetous annelids were dominant in the sorted 2016 benthic samples with amphipods, bivalves, gastropods, and ophiuroid echinoderms also present at all stations. Some stations near Iqaluit indicated the presence of isopods and ostracods while samples collected to the southeast of Iqaluit indicate the presence of ostracods, pycnogonids, shrimp, and bryozoan fragments. Towed video transects have been analyzed at four LTE stations. Two stations were dominated by tubiculous suspension-feeding polychaetes and ophiuroid echinoderms, however, different ophiuroid species were observed at each of these stations. One station was dominated by a red leafy macroalgae and ophiuroids and another station was dominated by a brown mat over the sediment along with the macroalgae Agarum sp. and Laminaria sp. Community structure analysis performed on the historical and new sample data will evaluate the extent of temporal change of benthic communities in inner Frobisher Bay.