Azores Deep-sea Research — Cruise MISTIC SEAS III

Developing a coordinated approach for assessing Descriptor 4 via its linkages with D1 and other relevant descriptors in the Macaronesian sub-region

The potential for Blue Growth is seen as an important driver of coastal European economies. However, Blue Growth opportunities need to be balanced with the preservation of marine ecosystems. A key policy driver for effectively protecting the marine environment across Europe is the Marine Strategy Framework Directive (MFSD) which aims to promote Good Environmental Status (GES) of EU marine waters. Progress towards achieving GES requires an assessment of changes in the ecosystem over time. For accurate assessment, these changes must be measured against a standard or reference of eleven descriptors laid out in the MSFD. Here, we use ecosystem models to evaluate food-web indicators to address the MSFD Descriptor 4 (D4), namely concerning the status of deep-sea ecosystems and their alterations by pressures from human activities and environmental variability. The ultimate loss of resilience of marine ecosystems seems to be associated with critical points that demark the transition between regimes of ecosystem status. Critical transitions towards alternative stages involve a reorganization of the system. These could be potentially identified through thresholds of indicators that synthesize ecosystem functioning and structure. Indicators linked to cumulative trophic theory, (i.e., cumulative biomass-trophic level) are illustrative examples of indicators with such characteristics. The overarching goal of the study was to advance knowledge regarding the application of model-derived food-web indicators, informing the assessment of Descriptor 4 towards the achievement of GES in the Macaronesia sub-region.

The main objective of MISTIC SEAS III project was to address the assessment of the environmental status of the marine environment, based on Descriptor 4 (D4, food webs) of the Marine Strategy Framework Directive (MSFD) in Macaronesia sub-region (Azores, Madeira and Canary Islands), following the criteria set by the European Commission. Through coordinated action and a common approach, the assessment of the environmental status of the marine environment in the Macaronesia sub-region was carried out, defining and testing methodologies that enable to identify trophic guilds.

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Collaborators

Mónica Silva

Luís Outeiro

Lorena Couce Montero

José Nuno Gomes-Pereira

Gilberto Carreira

TEAM's ROLE in MISTIC SEAS III

We lead the iMAR Eurofleet+ project and the respective cruises on board the RV Pelagia in 2021 and 2022

General information

Project reference

110661/2018/794676/SUB/ENV.C2 (MISTICSEAS III)

Funding agency

Subcontract with the Azores Government. European Maritime Fisheries Fund

Time period

02/09/2019 to 31/08/2021

External website https://misticseas3.com/en

Main results

The overarching goal of our participation in the MSIII project was to advance the application of model-derived food-web indicators, to support the assessment of Descriptor 4 towards the achievement of GES in the Macaronesia sub-region. We concluded that the parameters describing the cumulative biomass curve of marine ecosystems are robust model-derived indicators of the food-web state. Furthermore, we estimated threshold values in these parameters that inform a critical condition of the system and suggest a weak ability of the system to return to a baseline state. Crossing these thresholds represents a significant change in the structure and functioning of the ecosystem.

Ecosystem models can be a powerful tool to obtain surveillance indicators, which are not operational but that could give information on changes in the ecosystem's biological structure. These indicators are relevant when it is difficult to link anthropogenic pressures to ecosystem changes, setting desirable and undesirable limits which can act as a proxy measure of the GES.
The parameters describing the cumulative biomass curve of marine ecosystems were revealed to be robust model-derived indicators of the food-web state. We confirmed that perturbations impacting high and low trophic levels drive changes in the structure and functioning of the ecosystem that can be signalled in modifications in the shape of the cumulative biomass curve.
We identified threshold values in these parameters that inform a critical condition of the system and suggest a weak ability of the system to return to a baseline state of the food web. We estimated lower and upper thresholds of biomass at the inflexion point, the trophic level of inflexion point and steepness.
Fishing impacts combined with environmental conditions that limit the transfer of energy up the food-web were predicted to promote outstanding ecosystem-wide effects. Unbalances in the biomass of dominant groups (zooplankton, in the case of the Azores) were predicted to cause the greatest impacts on the system. Based on these results, we suggest that the structuring role of low trophic level groups, for example zooplankton, should be better understood to ultimately investigate if they can be used as indicator-species of food-web status.

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