Supporting ecosystem services of habitat and biodiversity in temperate seaweed (Saccharina spp.) farms.

Habitat provisioning, and the biodiversity within, is considered a type of "supporting" ecosystem service. Ecosystem services are the benefits humans receive from healthy ecosystems. We assess whether kelp (Saccharina spp.) farms provide seasonal habitat for wild organisms. Contrary to other studies conducted in tropic seaweed farms, we did not observe habitat provisioning or increased biodiversity at seasonal temperate seaweed farm sites compared to neighboring non-farm sites, which is encouraging news for the aquaculture industry given that most farm gear is removed from the water after the spring harvest. We quantified fish and crustaceans interacting with kelp farms using GoPro cameras. We also assessed small (<5 mm) invertebrates using mesh settling devices suspended at the same depth as kelp lines (2m). Visual surveys were paired with eDNA. There was coherence in the conclusions drawn from observational and eDNA methods, despite weak coherence in the specific species identified between the methods. Both farm and non-farm sites exhibited higher species richness and biodiversity in the summer non-growing season compared to the winter growing season, attributed to expected seasonal species movements.

Effects of climate change on coastal ecosystem food webs: Implications for aquaculture.

Coastal ecosystems provide important ecosystem services for millions of people. Climate change is modifying coastal ecosystem food web structure and function and threatens these essential ecosystem services. We used a combination of two new and one existing ecosystem food web models and altered scenarios that are possible with climate change to quantify the impacts of climate change on ecosystem stability in three coastal bays in Maine, United States. We also examined the impact of climate change on bivalve fisheries and aquaculture. Our modeled scenarios explicitly considered the predicted effects of future climatic change and human intervention and included: 1) the influence of increased terrestrial dissolved organic carbon loading on phytoplankton biomass; 2) benthic community change driven by synergisms between climate change, historical overfishing, and increased species invasion; and 3) altered trophic level energy transfer driven by ocean warming and acidification. The effects of climate change strongly negatively influenced ecosystem energy flow and ecosystem stability and negatively affected modeled bivalve carrying capacity in each of our models along the Maine coast of the eastern United States. Our results suggest that the interconnected nature of ecosystem food webs make them extremely vulnerable to synergistic effects of climate change. To better inform fisheries and aquaculture management, the effects of climate change must be explicitly incorporated.

Stable isotopes reveal contrasting trophic dynamics between host-parasite relationships: A case study of Atlantic salmon (Salmo salar) and parasitic lice (Lepeophtheirus salmonis and Argulus foliaceus).

Across existing fish host-parasite literature, endoparasites were depleted in δ15 N compared to their hosts, while ectoparasitic values demonstrated enrichment, depletion and equivalence relative to their hosts. δ13 C enrichment varied extensively for both endo- and ectoparasites across taxa and host tissues. In our case study, sea lice (Lepeophtheirus salmonis) were enriched in δ15 N relative to their farmed Atlantic salmon (Salmo salar) hosts, although the value contradicted the average that is currently assumed across the animal kingdom. Common fish lice (Argulus foliaceus) did not show a consistent trend in δ15 N compared to their wild S. salar hosts. Both parasitic species had a range of δ13 C enrichment patterns relative to their hosts. Farmed and wild S. salar had contrasting δ13 C and δ15 N, and signals varied across muscle, fin and skin within both groups. L. salmonis and A. foliaceus subsequently had unique δ13 C and δ15 N, and L. salmonis from opposite US coasts differed in δ15 N. Given the range of enrichment patterns that were exhibited across the literature and in our study system, trophic dynamics from host to parasite do not conform to traditional prey to predator standards. Furthermore, there does not appear to be a universal enrichment pathway for δ13 C nor δ15 N in parasitic relationships, which emphasizes the need to investigate host-parasite linkages across species.

Food webs and species biodiversity of the fouling community associated with bivalve aquaculture farms compared to analogous non-farm structures.

Bivalve aquaculture farms are an integral part of the surrounding coastal marine ecosystem and associated food webs. What is not well understood is how these anthropogenically manipulated, dense, single-species cultures influence species trophodynamics in the coastal ocean. Fouling macrofauna biodiversity, macroalgae biomass, sediment, and food web structure were studied at two blue mussel (Mytilus edulis) floating raft rope-culture aquaculture farm structures and two analogous floating dock structures without mussels in Casco Bay, Maine, USA during the summers of 2016 and 2017. Shannon Wiener diversity index of macrofauna was variable across structures compared depending on month. Macroalgae biomass was significantly higher on farm structures exclusively due to green macroalgae. There was no shift in food web structure determined by stable isotope analysis (δ13C and δ15N) and Layman metrics. This study is an initial step critical to assessing interactions of bivalve farms with coastal food webs.