Investigating nearshore benthic ecosystem structure in the Kachemak Bay, Alaska NERR

Benthic communities are important components of nearshore ecosystems, where they process organic matter, mediate nutrient and oxygen fluxes in the benthos, and provide food for higher trophic level organisms. Furthermore, they are largely composed of non-motile organisms that feed on organic matter sinking from above, and thus tend to reflect average conditions, integrating over short-term sources of variation such as tidal signals, pulses of primary production, and changes in freshwater runoff, making studying them an important tool in understanding nearshore ecosystems. In partnership with the Kachemak Bay National Estuarine Research Reserve, this project seeks to characterize benthic community composition and organic matter processing across multiple adjacent bays along southern Kachemak Bay, with a focus on communities below active mariculture operations. Sediment cores were manually collected via SCUBA from eight sites spanning four bays. Cores were analyzed for community composition, microbial biomass, sediment grain size, sediment total organic carbon. Sediment grain size varied by location, most with high percentages of gravel and sand. Polychaetes were partitioned into feeding guilds in which subsurface deposit and suspension feeders were most dominant. Infaunal carbon biomass and microbial biomass at each location were comparable and ranged between 0-30 g C/m. Sediment total organic carbon varied between 250-2000 g C/m among locations. Benthic community composition was similar across adjacent bays but exhibited variability in correspondence to their sediment type.

Primary Presenter: Jonah Jossart, University of Alaska Fairbanks (jrjossart@alaska.edu)

Authors:

Jonah Jossart, University of Alaska, Fairbanks  (jrjossartr@alaska.edu)

Sarah Mincks, University of Alaska Fairbanks  (slmincks@alaska.edu)

Amanda Kelley, University of Alaska Fairbanks  (alkelley@alaska.edu)