This paper deals with the evolution monitoring of biomass colonization and mechanical properties of 3D printed eco-materials/mortars immersed in the sea. Measurements of tensile strength, compressive strength, and Young’s modulus were determined on samples deployed along the Atlantic coast of Europe, in France, United Kingdom, Spain, and Portugal. The samples were manufactured using 3D printing, where six mix designs with a low environmental impact binder were used. These mortars were based on geopolymer and cementitious binders (Cement CEM III), in which sand is replaced by three types of recycled sand, including glass, seashell, and limestone by 30%, 50%, and 100% respectively. The colonization of concrete samples by micro/macro-organisms and their durability were also evaluated after 1, 3, 6, 12, and 24 months of immersion. The results showed that both biomass colonization and mechanical properties were better with CEM III compared to geopolymer-based compositions. Therefore, the mixed design optimized according to mechanical properties show that the use of CEM III should be preferred over these geopolymer binders in 3D printed concrete for artificial reef applications.

Accurately quantifying primary productivity in highly dynamic subtidal rocky habitats, particularly those with high canopy-forming macroalgae, is inherently challenging, leading to a scarcity of information. Kelp primary productivity has primarily been assessed through (1) quantification of carbon standing stock and biomass, which provides limited information on rates of primary productivity; (2) ex-situ incubations in the laboratory, in which the obtained values may not represent the actual productivity of a community; and (3) in-situ incubations in detached plants or including only the fronds. To address this issue, we describe a versatile methodology—the Benthic Incubation Chamber (BIC); and tested it along the morphologically diverse Portuguese continental coast. BIC is designed to assess in-situ primary productivity in a variety of benthic communities (high and low canopy), fulfilling the existing need to measure productivity in highly dynamic, shallow subtidal habitats. The method involves incubation chambers where total oxygen flux, temperature, and photosynthetically active radiation (PAR) are simultaneously recorded. From those measurements, Net Community Productivity (NCP) and community respiration (CR) for a given biomass and water volume were derived for each chamber. Incubations performed in the Portuguese continental coast demonstrated the feasibility of this technique to obtain reliable in-situ net primary productivity values in a range of subtidal habitats. This method contributes to a comprehensive approach to sustaining and protecting vital marine ecosystems, supporting biodiversity and addressing environmental issues.

Despite substantial research on kelp holdfast biodiversity, the drivers of macrofaunal diversity, abundance, and biomass across holdfast types and different climatic regions remain unresolved. This uncertainty extends to ecosystem functioning, where empirical estimates of secondary production are rare. We quantified the relative influence of regional environmental context and holdfast morphology on macrofaunal assemblages inhabiting holdfasts of Laminaria ochroleuca and Saccorhiza polyschides in two contrasting regions along the western Iberian coast climatic gradient: the northern A Coruña, Spain (COR; cooler, lower wave exposure) and the southern Peniche, Portugal (PEN; warmer, higher wave exposure). We also investigated ecological functioning by estimating secondary production. Macrofauna diversity, abundance, biomass (ash-free dry mass; AFDM), and secondary production were assessed at the holdfast level in samples collected from both regions in summer 2021. Holdfast structural complexity was quantified as surface-to-volume ratio (SA/V). Underwater Visual Census (UVC) surveys were conducted to provide reef-scale context for regional differences. Secondary production (consumer incorporation of organic matter per time) was estimated with Edgar's empirical model to infer energy-transfer dynamics. The cooler region, COR, exhibited significantly higher overall diversity and production than PEN. While S. polyschides supported lower taxonomic diversity than L. ochroleuca, it exhibited higher secondary production. These findings highlight the importance of regional climatic context in shaping kelp holdfast biodiversity and functioning. Differences between cooler and warmer regions suggest that variation in thermal regimes can be associated with changes in holdfast community structure and secondary production.

Kelp forests are foundation habitats that create structurally complex and biodiverse marine ecosystems, yet their extent and ecological integrity are increasingly threatened by rising ocean temperatures and the resulting tropicalisation of temperate coasts. Quantitative assessments of these changes remain very limited, and understanding them is particularly critical in climate transition zones, where ecological shifts can be rapid and pronounced. We conducted a 5‐year (2020–2024) survey for kelp–fish communities at four representative regions along ~600 km of the Iberian coast ( n = 450 transects), spanning a gradient of current and projected tropicalisation. The analysis focused on how kelp species identity and abundance, local sea surface temperature (SST) and reef‐fish assemblage characteristics influence fish population metrics and the community temperature index (CTI). In total, 53 fish species and 4 species of kelps were found. Perennial kelp composition closely followed the SST gradient, with the boreal kelp Laminaria hyperborea dominating in cooler sites (Coruña and Viana), whereas the Lusitanian kelp Laminaria ochroleuca prevailed in warmer sites (Vigo and Peniche). Coruña displayed the highest kelp diversity and abundance, while the southernmost Peniche exhibited the highest fish diversity. Kelp‐abundant regions exhibited lower fish CTIs than expected from local SST, suggesting a potential canopy buffering effect against tropicalisation. In contrast, Peniche, with lower kelp abundance, showed minimal CTI‐SST offset, higher proportions of warm‐affinity taxa and the greatest fish diversity, indicating a more advanced tropicalisation stage. Synthesis . Our spatially resolved benchmark indicates that abundant kelp cover can delay tropicalisation by lowering the realised thermal affinity of reef‐fish communities, while increases in fish biodiversity may signal the early stages of this process. These results underscore the dual role of kelp forests as biodiversity reservoirs and climate buffers, and provide a transferable framework for understanding how foundation species mediate community responses to ocean warming across ecosystems. Safeguarding and restoring kelp forests should therefore be a priority for sustaining temperate‐reef resilience under climate change.

Understanding climate change impacts on benthic habitats is crucial to acknowledge their actual ecosystem functioning value. One pertinent way to achieve this is by measuring primary productivity. Accurately quantifying primary productivity in turbulent subtidal, rocky habitats, particularly those with high canopy forming seaweeds, such as kelp, is inherently challenging, leading to a scarcity of information. Kelp primary productivity has primarily been assessed through 1) quantification of carbon standing stock and biomass, which provides limited values of net primary production; 2) ex-situ incubations in the laboratory, in which the obtained values do not accurately represent the real production of a community; and 3) in-situ incubations on individual kelp fronds, neglecting community effects on the production. To address this issue, we describe a novel methodology – the Benthic Incubation Chamber (BIC) - designed to assess in-situ primary productivity of different benthic communities (high and low canopy). The method involves incubation chambers where total oxygen flux, temperature, and photo-synthetically active radiation (PAR) are simultaneously recorded. From those measurements, net community production (NCP) and community respiration (CR) for a given biomass and water volume were derived for the sampled area of each chamber. Results from Portuguese continental coast showed differences in NCP rates among different benthic communities and demonstrated the feasibility of this technique to obtain reliable in-situ net primary productivity values in a variety of subtidal habitats. This method contributes to a comprehensive approach to sustain and protect vital marine ecosystems, supporting biodiversity and addressing environmental issues like climate change.