Marine forests, dominated by canopy-forming brown seaweeds such as kelps and fucoids, are among the largest and most productive vegetated habitats on Earth, covering ~ 25% of the world’s coastlines. These structurally complex habitats provide a wide range of invaluable ecosystem services, including supporting coastal biodiversity, sequestering carbon, and creating climate refugia. Consequently, their conservation and restoration are increasingly recognised as cost-effective Nature-Based Solutions (NBS) to address biodiversity loss and climate change (CC). Yet, paradoxically, the very habitats with this mitigation potential are themselves under severe threat. Global marine forest populations have declined by approximately 60% over the past fifty years, with current annual losses estimated at around 2%, driven primarily by rising ocean temperatures, intensified anthropogenic pressures, and the cascading ecological consequences of these stressors.
The Portuguese coast contains a biogeographical transition zone, supporting remarkable diversity in both intertidal and subtidal marine forest communities. The temperate northern region serves as a climate refugium for cold-water affinity species, maintained by persistent upwelling events in summer, while progressively warmer southern conditions support warm-affinity and thermally resilient taxa. Recent research has shown that these communities are shifting rapidly, with structurally complex kelp species being replaced by thermally tolerant or structurally simpler organisms, such as turf-forming algae. This process, termed tropicalisation, has profound ecological consequences: destabilisation of habitat structure, facilitation of non-native species proliferation, disruption of biotic interactions including increased grazing pressure, and progressive functional homogenisation of seaweed communities. While the structural dimension of these shifts is increasingly documented, their functional consequences and the repercussions for the ecosystem services that marine forests sustain remain critically underexplored.
The FUNSEA project is designed to fill this fundamental knowledge gap. Its overarching objective is to understand the functional impacts of seaweed loss and community change in a warming ocean, providing innovative trait-based and decision-support frameworks to assess these impacts and guide best practices for coastal ecosystem conservation and CC mitigation. The project is structured around six interconnected work packages, advancing from baseline trait measurements through functional diversity quantification to scenario modelling and the co-development of management tools.
Central to FUNSEA’s approach is the use of functional diversity frameworks, which have emerged as integrative indicators of ecosystem functioning. By characterising the functional traits of key seaweed species across depth, thermal and latitudinal gradients along the Portuguese coast, the project will identify which species and trait combinations contribute most to ecosystem functioning and which are most vulnerable or resilient to thermal stress. This will enable FUNSEA to determine functional thresholds to warming through innovative experimental protocols, assess whether thermally resistant communities retain equivalent functional capacity to those they replace, and identify functionally unique species whose loss may disproportionately compromise ecosystem functioning.
FUNSEA also addresses critical hypotheses regarding directional changes in community strategy under warming, specifically a predicted shift from conservative to acquisitive ecological strategies from north to south, and the implications of this shift for carbon sink potential, habitat complexity as nursery groung for fisheries, biodiversity support, and other key ecosystem services.
The project will deliver several concrete outcomes: 1) a comprehensive empirical dataset linking seaweed traits to ecological processes and services; 2) functional indicators of ecosystem vulnerability and resilience applicable across thermal gradients, supporting EU directives; 3) and a decision-support tool integrating functional diversity data with climate change scenarios to guide informed management decisions for the conservation of marine forests as NBS to CC.
The FUNSEA project is conducted by a multidisciplinary team based at CIIMAR and MARE-IPL, with a strong track record in monitoring Portuguese marine forests and studying seaweed diversity, functional ecology, and climate change impacts. Aligned with SDG 13 and SDG 14, and committed to stakeholder engagement and science communication, FUNSEA will generate the knowledge and tools needed to ensure that marine forests fulfil their potential as resilient, climate-smart natural capital for present and future generations.