March 1, 2024

New tool expertly predicts changes in marine habitat

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Study domain and the eleven Large Marine Ecosystems (LMEs) of North America, with significantly greater forecast skills of the decadal forecast system versus reconstruction persistence in predicting habitat viability in the upper 600 m ocean. Credit: Nature Communications (2024). DOI: 10.1038/s41467-024-45016-5

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Study domain and the eleven Large Marine Ecosystems (LMEs) of North America, with significantly greater forecast skills of the decadal forecast system versus reconstruction persistence in predicting habitat viability in the upper 600 m ocean. Credit: Nature Communications (2024). DOI: 10.1038/s41467-024-45016-5

As global temperatures rise, so do ocean temperatures. The ocean absorbs around 90% of the world’s excess heat, which causes changes in the marine environment that go beyond temperature, making some areas uninhabitable for some marine species.

Researchers are working to understand and anticipate how these environmental changes will impact changes in marine habitats. A team of scientists, including UConn Department of Marine Sciences researchers Zhuomin (Jasmine) Chen and Samantha Siedlecki, is working together to improve predictions of habitat changes for different marine species. Their findings were published in Nature Communications.

Habitats change or shrink as marine species seek suitable environments for their survival and for the fulfillment of other essential ecological activities, such as growth, feeding and reproduction. The ability to anticipate these changes has great value for policymaking, research and helping the fishing industry cope with the changing environment.

Chen explains that the multidisciplinary team predicted interannual to decadal habitat changes for several marine species in the upper 600 meters of 11 Large Marine Ecosystems (LMEs) in North America, based on a key metabolic index combined with a suite of decadal forecast systems. .

The index was previously developed by another research group and indicates habitat viability; and the decadal forecast system is called Community Earth System Model-Decadal Prediction Large Ensemble (CESM-DPLE) developed by the National Center for Atmospheric Research.

“At this time, marine species habitat predictions generally have a relatively narrow focus on the environmental variables that shape species distribution, typically using temperature as the main or only determinant of ecological niche predictions. However, our work breaks with this tradition by highlighting the potential that oxygen may play a role in driving changes in marine habitat,” says Chen.

Greater predictability of viability for marine life

Hypoxic conditions occur when oxygen levels are low. The researchers focused on species with two key metabolic traits: temperature sensitivity, hypoxia vulnerability, and hypoxia tolerance, both defined in the Metabolic Index framework and determined for a diversity of species using previously published laboratory and field data. They focused on species that fell into three different groups, called ecotypes, depending on their temperature sensitivities and metabolic needs, designated low, medium and high.

“Metabolic Index was originally defined as a ratio of environmental oxygen supply to an organism’s resting metabolic demand, which considers both oxygen availability and the effects of temperature. For marine habitats to be metabolically viable, the ratio should be greater than a critical value of one for resting metabolism or greater than a critical value greater than one for active metabolism. Therefore, in this study, we focus on a metabolic index normalized to a consistent critical value of active metabolism and on rest,” says Chen.

By selecting representative ecotypes with characteristics of sensitivity to low, medium and high temperatures and the same characteristic of hypoxic tolerance, researchers found that these characteristics correspond to different distributions of viable habitats in space, as well as their interannual changes in the horizontal and vertical, integrating both spatial differences and interannual variability of environmental variables such as oxygen and temperature.

Chen says the results show that interannual shifts in viable habitat for species sensitive to medium and high temperatures are generally meridional, suggesting that species would have a northward contraction of viable habitat, with southern limits retreating northward. in response to heating or deoxygenation. Although the viable habitats of species sensitive to low temperatures have not only meridional contractions in the high northern latitudes, but also longitudinal changes along the southwest coast of North America.

The researchers found that the CESM-DPLE system combined with the ecophysiological framework provides significantly greater predictability of habitat viability for diverse marine species across the 11 Large Marine Ecosystems of North America than simple predictions of persistence almost everywhere and in every initial years, with better predictability especially underground.

As habitats change, the need for accurate predictions increases

Chen says different regions may have different environmental variables that predominantly contribute to predictability. The researchers used a method called Taylor linear decomposition to take a closer look at the variables and identify the predictability factor in each Large Marine Ecosystem. In most cases, oxygen was the dominant driver of predictability, especially for the Northeast Pacific regions, but not always.

“We identified some regions—for example, the inner shelf of the eastern Bering Sea—with limited contribution to the predictability of the oxygen component, but the temperature component is relatively dominant to the predictability in these regions,” says Chen.

For the northeast coast, Chen explains that the temperature component is an important factor or even determinant of predictability, likely due to the relaxation of oxygen constraints on habitat viability due to strong ventilation processes in these high-latitude regions.

By using the decadal forecast system combined with the ecophysiological mechanistic framework, Chen explains that habitat forecast products can be fully employed for managing living marine resources and making decisions in response to changing ocean conditions,

“We are primarily focusing on the interannual to decadal time scale, which is a very important time horizon for decision-making and management of marine resources to reduce impacts, promote resilience and maximize the value of living marine resources in the face of changing environmental conditions. oceans.”

Predicting spatial distributions of viable habitats will become increasingly important for things like habitat shifts. For example, Chen says habitat contractions to the north could make fishing in certain ports unviable, while habitat expansion to the south opens up ports that would need to be prepared to process landings, which will likely impact the fishing industry. There are also substantial ecological impacts to consider, says Chen.

“Spatial and vertical habitat shifts of uneven species due to their different metabolic characteristics, e.g. different temperature sensitivity characteristics, can lead to substantial changes in prey-predator dynamics and ecosystem structure, e.g. habitat overlap viable southern and northern silverfish with juveniles as prey and adults as predators, which may affect resource availability for fisheries and require adaptation by stakeholders,” says Chen.

More information:
Zhuomin Chen et al, Skillful multiyear prediction of marine habitat changes jointly limited by ocean temperature and dissolved oxygen, Nature Communications (2024). DOI: 10.1038/s41467-024-45016-5

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