SUMMER

Context

The mesopelagic layer is one of the least understood ecosystems on Earth. Recent research suggests that the fish biomass in the mesopelagic ecosystem might be 10 times higher than previously thought, and therefore represent 90 % of the fish biomass of the planet. However, this estimate is subject to a high degree of uncertainty in the fraction of the community that is fish. The potential high biomass has raised interest in its exploitation, mainly as a fish meal, but other potential exploitation pathways for high value compounds, such as nutraceuticals and pharmaceuticals, are possible. Nevertheless, if the biomass is as high as estimated, mesopelagic fish may play a key role in ecosystem services, such as sustaining other commercially relevant species and carbon sequestration.

SUMMER will establish a protocol to accurately estimate mesopelagic fish biomass, quantify the ecosystem services provided by the mesopelagic community (food, climate regulation and potential for bioactive compounds) and develop a decision support tool to measure the trade-offs between the different services.

Objectives

The overall objective of SUMMER is to evaluate whether and how mesopelagic resources can be exploited without compromising the essential ecosystem services they provide.  The specific objectives are:

• Determine the best combination of methods (including submersible broad-band acoustics, environmental DNA (eDNA) and scientific trawls) to obtain unbiased biomass and biodiversity estimates of the mesopelagic community.
• Estimate global abundance of mesopelagic fish based on a combination of the developed methods and models.
• To quantify the bycatch and impact on biodiversity of fishing
• To measure the role of mesopelagic organisms in the vertically integrated food web, its “service” as food for commercially fished species, deep-sea species and emblematic species and to model the effects of different fishing scenarios on trophic network stability
• To estimate the carbon sequestration due to active migration relative to the gravitational flux and to model the effects of different fishing scenarios
• To explore the potential of mesopelagic organisms for pharmaceutical and nutraceutical products, processed human food and animal feed, and to evaluate the intangible value of the ecosystem for production of high-value products
• To provide a holistic assessment of the services provided by the mesopelagic ecosystem and to establish trade-offs and tipping points between different services under different fishing harvest rates scenarios
• To engage managers, stakeholders and society on defining strategies and associated risks to use mesopelagic resources, proposing strategies for its sustainability

Key Results

• Biomass:
  A global biomass estimate of 1.3 billion tonnes was obtained, representing 87% of total pelagic biomass.
• Food-web structure and resilience:
  Simulations reveal strong regional variability in the capacity of food webs to withstand fishing pressure and indicate that these networks are particularly sensitive to the harvesting of mesopelagic fish.
• Carbon storage and climate regulation:
  Globally, of the nearly 1.3 billion tonnes of mesopelagic organisms, 39% perform daily nocturnal vertical migrations. Based on this behaviour, the active carbon flux associated with vertical migrations of mesopelagic fish below 150 m was estimated at 1.39 PgC per year worldwide. In relation to this active flux, SUMMER developed a decision-support tool to inform management decisions on the exploitation of mesopelagic organisms, allowing stakeholders to interactively explore the impacts of diel vertical migration (DVM) on the biological carbon pump (BCP). The tool is available at: https://summer-mesopelagic.shinyapps.io/summer/
• High-value products:
  SUMMER established a library of approximately 700 microbial extracts. The results highlight the pharmaceutical potential of mesopelagic microorganisms, indicating that the mesopelagic zone is a largely untapped resource, rich in microbial diversity with the capacity to produce unique bioactive compounds.
• Ecosystem services and management assessment:
  SUMMER simulated a potential commercial fishery and assessed trade-offs between the Sustainable Development Goals (SDGs). On average, the benefits derived from the production of fishmeal and fish oil from mesopelagic fishing were found to be outweighed by the costs associated with climate regulation and the loss of other species, both commercial and non-commercial. At the regional level, SUMMER estimated an average social cost of €19 per tonne of mesopelagic fish caught, while acknowledging substantial uncertainty around this estimate. To assess and account for this uncertainty, an interactive tool was developed: https://aztidata.es/BayesNetVis/
• Policy implications:
  The results of the SUMMER research will be key for environmental impact assessments (EIAs) of new fisheries, for the Scientific and Technical Committee to be established under the COP once the treaty enters into force, and for Regional Fisheries Management Organizations (RFMOs) more broadly.

Mesopelagic Zone Creatures

Website

https://summerh2020.eu/

Participants

AZTI (coordination) and 22 research centres and companies worldwide.

Funding