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Tropical and South Atlantic climate-based marine ecosystem predictions for sustainable management

Periodic Reporting for period 3 - TRIATLAS (Tropical and South Atlantic climate-based marine ecosystem predictions for sustainable management)

Reporting period: 2022-06-01 to 2023-11-30

Countries bordering the South and tropical Atlantic depend heavily on marine ecosystems for food, genetic resources, and recreation. TRIATLAS’ aim is to enable sustainable management of human activities in the Atlantic Ocean as a whole, by closing knowledge gaps on the status of the South and Tropical Atlantic marine ecosystems and developing a framework for predicting their changes months to decades ahead—timescales of interest to society and stakeholders. We focus on six representative regions with three in-depth case studies (Fig. 1). TRIATLAS is a basin-wide cooperation that combines ecosystem observations, climate-based ecosystem prediction and information on future socio-economic and ecosystem service changes, with stakeholder interactions and clustering with key projects and programs.
TRIATLAS has been a very successfully project, with 42 deliverables, and many outstanding scientific achievements, disseminated through an exceptional number of over 260 publications. There was also extensive communication activities and involvement in more than 5 stakeholder and science-policy events.

Researchers have compiled comprehensive data sets for the South and Tropical Atlantic of physical, biogeochemical, and biological parameters. These combine existing observations and many new measurements, including from the 2019 Transatlantic Equatorial Cruise, a satellite-derived atlas of mesoscale eddies, and underwater vision profiler data. These have enhanced our understanding of ecosystem dynamics, from physics to plankton and fishes.

Studies of coastal and equatorial upwelling systems in the Atlantic have highlighted the influence of mean and seasonal currents interacting with topographic features. This has led to recommendations for improved marine spatial planning. Additionally, satellite and in situ observations have revealed a complex circulation system involving eddies and their impact on plankton distribution. The SAMOC mooring array is providing improved observations of the Atlantic ocean overturning circulation.

Analysis of plankton dynamics has shown the influence of climate conditions and lower trophic levels on the ecosystem. Here data from the Canary Islands, the Canary Current Upwelling system, and the Brazilian shelf were used, including from underwater video profilers. The analysis of zooplankton’s daily vertical migration has shed light on the biological carbon pump in the open ocean and in upwelling systems, and how it is influenced by ocean conditions.

Interannual to decadal fluctuations in physical, biogeochemical, and biological systems in the South and Tropical Atlantic were analyzed using diverse observations and numerical model simulations. Anthropogenic influences on marine ecosystems were examined using landing and socio-economic data, and numerical and statistical modelling. These have enhanced our understanding of the anticipated impacts of future climate change, and how it in combination with fisheries pressures will affect marine ecosystems.

The first ever Earth System – Marine Ecosystem Model Predictions were realized through close collaboration between climate and marine ecosystem researchers. In this way marine ecosystem can be predicted for the next month to ten years, under different fishing scenarios and considering climate variability. This new technique can become a powerful tool for managing human activities in the global oceans.

To deliver societal and policy relevant information, we have analysed the complex interrelationships with human social drivers, considering large-scale and artisanal fisheries and the vulnerability of fishing communities. We have also identified hotspots in marine biodiversity, intense human activities affecting the marine ecosystem, and anchoveta as a new consumption fishery. Furthermore, together with stakeholders, we have created future scenarios of coastal fisheries to feed into impact models.
Novel new data sets have given unprecedented insights into physical ocean processes and their impact on marine ecosystems. For example, observed tracer distributions were used to quantify ventilation and water mass exchange between western and eastern boundaries. Analyses of isotope patterns and of biomass size spectra over multiple trophic levels has provided insight into basin-scale ecosystem properties and processes. Baseline isotope data were useful for investigating the ecology of marine mammals.

The wealth of observations in the TRITATLAS study regions has allowed to disentangle effects of nutrient supply along gradients from oligotrophic to upwelling areas, effects of low oxygen levels found in the upwelling systems, and changes along temperature gradients indicative of climate change effects. The Ocean’s vertical dimension was better understood, through using depth resolved fish larval abundance data in hydroacoustical models of diel vertical migration.

A major outcome was a synthesis report of fisheries potential and future trends for the South Atlantic ecosystem assessments. It focused on estimating size spectra across several trophic levels, achieved by compiling trophic indicators and data standardization across the key TRIATLAS regions.

Another key outcome was a comprehensive review on the dominant influence of the El Niño Southern Oscillation on marine ecosystems in the South and Tropical Atlantic. Other phenomena, like Benguela Niño and Atlantic multi-decadal variability are important at regional or longer-time scales. These phenomena drive variations in dissolved oxygen, primary productivity, tuna, northeast Brazil shrimp and southeastern Atlantic sardinella and horse mackerel.

Long-term climate change will lead to the intensification of marine heatwaves in the southwest Atlantic and a weakening of the Atlantic Niño. The impact of marine heatwaves was shown to be compounded when accompanied by extreme ocean acidity and reduced primary productivity.

Our simulations have contributed to international model-intercomparison and (CMIP6, Fish-MIP II) and assessment reports (IPCC AR6 working groups I and II). This has produced new knowledge on potential future changes in marine ecosystems in the case study regions. The simulations have shown that global consumer biomass may decline by 12.5% by the end of the century.

TRIATLAS has boosted marine science capacity in Atlantic-bordering countries. This collaborative project, rooted in the Belém Statement, engaged scientific institutions and experts. It facilitated joint scientific cruises, data analysis, and ecosystem modelling. Notably, a low-cost framework enabled sophisticated models to run on regular hardware, independent of funding and IT expertise. Another important development, the Shiny4SelfReport app aids fishermen in reporting fishery landings. It’s free, open-source, adaptable, and user-friendly. Already utilized by fisherfolk and managers in Brazil and Cabo Verde, this tool can inform decision makers.

Established by TRIATLAS, the Cross-Atlantic Network of Excellence in Marine Science (CANEMS) strengthens capacity by promoting knowledge exchange, regional programs, and nurturing young scientists. Notably, it supported 19 PhD and MSc studies, organized interdisciplinary summer schools, and trained over 200 students on research cruises. CANEMS aims to establish lasting science cooperation across the Atlantic, akin to initiatives in the North Atlantic (ICES) and Pacific (PICES).