Sustainable management of our deep oceans
The mesopelagic zone of oceans begins at depths where only 1 % of light can reach and ends where there is no light at all. This covers depths of between 200 and 1 000 metres, depending on the region, and accounts for about 20 % of our ocean’s volume. While this oceanic zone is estimated to contain nearly 90 % of pelagic fish biomass, much of this region remains underexplored. Massive potential in terms of fishmeal production and the discovery of new molecules for nutraceuticals and pharmaceuticals is therefore underexploited. “This is one of the least explored ecosystems on Earth,” notes SUMMER project coordinator Raúl Prellezo from AZTI in Spain. “We wanted to identify the best methods for estimating biomass and biodiversity in this zone, and support ecosystem-based management.”
Estimating biomass within the mesopelagic zone
To achieve this, the project conducted surveys of fish populations at sea and combined these with existing data. Lab-based work such as gut content analysis was also carried out. “Using the information gathered, we were able to estimate biomass within this zone,” explains Prellezo. “We were also able to estimate the composition of this ecosystem, its role in the carbon cycle, and the relationship with other species and sea layers.” Interesting findings were made. For example, the SUMMER project demonstrated how daily vertical excursions of mesopelagic fish significantly enhance carbon sequestration (i.e. the capture and storage of carbon) and shed light on feeding interactions between mesopelagic species. The project’s findings were combined to create a decision assessment tool. This is designed to enable fisheries and ecosystem management services to consider all factors when looking at opportunities for sustainable commercial exploitation. This is timely, given growing industry focus on the commercial potential of the mesopelagic zone.
Mesopelagic microbial communities and new pharmaceuticals
The results of the SUMMER project suggest that exploiting fish for human consumption from this region, and transforming catches into fishmeal and fish oil, would be hard to make financially viable. “In fact, we obtained data suggesting significant risks of overfishing,” says Prellezo. “This underlines the need to protect this zone.” On the other hand, the project team identified several unique biochemical traits from mesopelagic microbial communities that could be promising sources for new pharmaceuticals. “Our research found that the mesopelagic zone is rich in microbial diversity, and capable of producing unique bioactive compounds,” adds Prellezo. “This could constitute a sustainable avenue for exploiting this zone.”
Protecting important marine ecosystems
The SUMMER project has contributed to our understanding of this mysterious zone in our oceans and underlined the importance of caution when looking to exploit fish populations. Combined analysis suggests that obtaining fishmeal and fish oil from mesopelagic populations would be challenging. Further research is therefore needed to investigate commercial viability here. “A clear message from this project is that under current economic and technical conditions, it is not worth exploiting this zone,” notes Prellezo. “On the other hand, we have learned more about how nutrients and organic carbon are transported from the surface to deep-sea layers, and how this could be crucial for climate regulation. Our recommendation would be to protect this sea layer and explore microbial communities that could be sustainably exploited.”
Keywords
SUMMER, mesopelagic, oceanic, microbial, pharmaceuticals, marine, ecosystems
