Wild lobster (Homarus americanus) abundance was monitored before, during, and after salmon (Salmo salar) aquaculture production in a bay on Grand Manan Island, New Brunswick, Canada, in an 8-year survey, 2008 to 2015. Diver transects and free-area spot-dives were used to measure the carapace length and determine sex (including berried state) of each lobster encountered both inside (farm) and outside (reference) the lease boundaries. In pairwise comparisons of each sampling date, there was no significant difference between the number of lobsters inside the salmon farming area versus a nearby reference site and no significant difference in the number of berried females inside or out of the farm lease area. Combining data from all lobster surveys (farm and reference sites) indicated an increase over 8 years, similar in slope to the increase of the trap fishery in Lobster Fishing Area (LFA) 38. These results indicate that the fish farm had no obvious impact on lobster density at any point in the salmon production cycle and that inshore lobster abundance followed trends similar to those of the general fishery of LFA 38.

No abstract

Nitrogen that has been recycled in the benthos supports high rates of primary and secondary production in estuaries. However, little is known about the effect of future climate on benthic nitrogen recycling and assimilation. An ex situ core incubation was used to assess the impact of combinations of warming (8°C range) and ocean acidification (OA) (i.e. increased pCO2 and decreased pH) on ammonium (NH4+) and nitrate/nitrite (NOx) fluxes and 15N-nitrate assimilation in shallow unvegetated estuarine sediments. Dissolved inorganic nitrogen (DIN = NH4+ + NOx) fluxes were significantly affected by the interaction of warming and OA, highlighting the importance of considering combined stressor treatments when investigating ecosystem responses to future climates. Warming alone increased DIN efflux from the sediments. At current mean ambient temperatures (23°C) and below (Δ-3°C), OA significantly increased DIN effluxes, but there was little to no effect of OA on DIN fluxes at warmer temperatures (Δ+3°C and Δ+5°C). OA reduced the 15N assimilation/retention of the sediments across all temperatures, suggesting that nitrogen retention in bacterial biomass was reduced, despite OA also increasing primary productivity. As such, under the projected future climate of ~3°C warming and doubling of pCO2 (~1000 µatm), unvegetated estuarine sediments are likely to have a more rapid turnover of DIN driven by greater microphytobenthos production and recycling.