Ocean health is declining due to a combination of climate warming and human activities, and is often accompanied by a reduction in ecosystem services. This decline is particularly evident in coastal regions where inputs from municipal, agricultural, aquaculture, and industrial sources lead to blooms of algae and gelatinous plankton. In Norway, one of the main threats to the health of coastal ecosystems is an increase in the deposition of organic matter to the sea floor. Excess feed and fish-waste from fish farms are major sources of organic matter, and the sinking of dead jellyfish, an increasing problem in some fjords, is another. This organic matter can alter the nutrient cycling on the sea floor and, in some cases, result in severe depletion of dissolved oxygen in the water. This can have impacts throughout the ecosystem, as well as upon the economic services that the ecosystems provide for society.
We have conducted field and laboratory research, as well as geochemical modeling and ecosystem services studies, over the past 3 years in Norwegian fjords. We have completed 3 9-10 month deployments of sediment traps in 6 fjord stations (Lurefjorden, 2 in Hardangerfjorden, Masfjorden, and 2 in Kaldfjorden) to document background delivery of organic material (OM) to the seafloor, as well as potential contributions of gelatinous zooplankton. The Kaldfjorden deployments also included ADCP current meters to aid in hydrographic modeling to feed into the BROM biogeochemical model. We found that the Periphylla-dominated fjord (Lurefjorden) had higher OM deposition than Masfjorden, which is free from Periphylla. One BS student has written her undergraduate thesis based on these data. In addition we have documented seasonal cycles in flux in both Hardanger fjord stations, although the trap near a fish farm showed a dampening of the seasonality, as well as higher total flux, compared with a station only 500 m away. The two stations in Kaldfjorden showed very similar patterns despite one being in quite different flow and presumed organic-input regimes.
To assess the fate and impact of jellyfalls on the seafloor we have performed scavenging studies to determine how quickly scavenging fauna consume jelly detritus. Here we were surprised to see that there was no depth gradient in scavenging rates, as has been found in many other studies with various baits. In addition, we see that the Norwegian lobster, Nephrops norvegicus is a frequent visitor to jellyfalls, and may derive a considerable fraction of their nutrition from jelly detritus. These two papers were published in late 2017 and early 2018 in high profile journals (Limnology and Oceanography, Scientific reports). The Nephrops results received considerable interest in the media, reaching well over 2 million readers through 51 print and on-line media in the UK and Norway. Scavenging studies in Kaldfjorden and Svalbard fjords indicate multiple and complex roles of Atlantic cod on scavenging dynamics in these Arctic fjords.
Impacts of jellyfish carcasses on the near-bottom hydrodynamics, which could have a significant effect on oxygen concentrations, were evaluated in flume studies. A new technique was also designed to test the impacts on sediment oxygen levels. Results indicate density-dependent effects of jellyfish carcasses on near-bottom current flow. At low carcass densities (6 per square meter), circulation in bottom waters is enhanced, but flow is reduced when densities reach 12 carcasses per square meter.
Experimental studies of sediment processes, where isotope-labelled OM was added in the presence and absence of jellyfish detritus, were conducted in 2016 in Hardangerfjorden, and in 2017 in Kaldfjorden (Troms). Initial results indicate that fish farms affect organic carbon content, nematode and foraminiferal abundance, and macrofaunal community structure in Hardangerfjorden. Carbon uptake into nematodes was also affected, but no synergistic effects of jellyfish additions were recorded for nematode respiration.
Results of the above studies are helping parameterize a geochemical model (BROM). A manuscript (in revision) using this model and field data from Hardangerfjord integrates project results to achieve a broad understanding of sources, fates, and impacts of jellyfallls on sediment community structure and function. The model is also now being implemented for Kaldfjorden to further integrate our findings and provide a contrast with the southern Norwegian fjord. These results are being combined with both interview-based valuation studies and bioeconomic modeling to evaluate the socioeconomic/ecosystem-services impacts of jellyfish-fish farm interactions.
In this large, collaborative project we have built and strengthened partnerships among both the national and international partners in the project, as well as several institutions that came into the project as collaborators but not full partners. We have also combined experimental work and modeling, with outputs applied to socio-economic analyses related to environmental status around fish farms. Scientific outcomes have been published for the academic community, in popular science publications, and in our blog. More synthetic work still to be published (bioeconomic assessment) will be of significant management value. Longer-term impacts include participation of 13 young scientists in this project where they were exposed to international collaboration and multidisciplinary applied research of relevance to management and society. Synthetic work will provide knowledge-based advice related to the aquaculture industry and will have long-term benefits for the industry and its regulators.
Ocean health is declining due to a combination of climate warming and human activities, and is accompanied by a concomitant reduction in ecosystem services. This decline is particularly evident in coastal regions where inputs from municipal, agricultural, aquaculture, and industrial sources lead to blooms of algae and gelatinous plankton. Whereas these stressors have been studied individually in Norway, combined effects of the most prevalent sources of organic loading have not been addressed. This project uses an inter- and multi- disciplinary approach to investigate the effect of organic loading from jellyfish detritus and aquaculture waste on seafloor ecosystems along the coast. We investigate the cumulative effects of anthropogenic climate change and pollution on populations of marine species, the ecosystem as a whole, and society at large, including processes and interactions within and between these levels using field, laboratory, and modeling activities. Our results will feed into a socio-economic study exploring the effect of interactions between anthropogenic and natural changes in climate and the environment on ecosystem functions and services in Norway's coastal environments. These are the primary themes within the ØKOSYSTEM joint ecosystem-effects call. Finally it will provide an assessment of the impact and probability of wide-ranging changes in the composition, function and dynamics of ecosystems. This is critical for sustainably managing marine ecosystems in Norway, quantifying ecosystem resilience in the face of combined stressors, and providing projections of society?s ability to adapt to such changes. Two postdoctoral positions and key roles for four early-career scientists make this project a valuable training vehicle for Norwegian marine science.