Present-day and future net carbon source-sink dynamics of rhodolith beds: Implications for climate change mitigation

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Rhodolith physiology across the atlantic: towards a better mechanistic understanding of Intra- and interspecific differences

Publication . Schubert, Nadine; Peña, Viviana; Salazar, Vinícius W.; Horta, Paulo A.; Neves, Pedro; Ribeiro, Cláudia; Otero-Ferrer, Francisco; Tuya, Fernando; Espino, Fernando; Schoenrock, Kathryn; Hofmann, Laurie C.; Le Gall, Line; Santos, Rui; Silva, João

Coralline algae are important components in a large variety of ecosystems. Among them, rhodoliths are a group of free-living coralline red algae that cover extensive coastal areas, from tropical to polar regions. In contrast to other ecosystem engineers, limited research efforts preclude our understanding of their physiology, underlying mechanisms, drivers and potential differences related to species under varying environments. In this study, we investigated the photosynthetic and calcification mechanisms of six Atlantic rhodolith species from different latitudes, as well as intra-specific differences in one species from four locations. Laboratory incubations under varying light levels provided simultaneous photosynthesis- and calcification-irradiance curves, allowing the assessment of inter- and intra-specific differences on the coupling between these two processes. Stable isotope analysis and specific inhibitor experiments were performed to characterize and compare carbon-concentrating mechanisms (CCMs), as well as the involvement of specific ion-transporters for calcification. Our findings showed significant differences in rhodolith physiological mechanisms that were partially driven by local environmental conditions (light, temperature). High variability was found in the coupling between photosynthesis and calcification, in CCM-strategies, and in the importance of specific ion transporters and enzymes involved in calcification. While calcification was strongly correlated with photosynthesis in all species, the strength of this link was species-specific. Calcification was also found to be reliant on hotosynthesis- and light-independent processes. The latter showed a high plasticity in their expression among species, also influenced by the local environment. Overall, our findings demonstrate that (1) rhodolith calcification is a biologically-controlled process and (2) the mechanisms associated with photosynthesis and calcification display a large variability among species, suggesting potential differences not only in their individual, but also community responses to environmental changes, such as climate change.

2022Journal article

Open access

Levelling-up rhodolith-bed science to address global-scale conservation challenges

Publication . Tuya, Fernando; Schubert, Nadine; Aguirre, Julio; Basso, Daniela; Bastos, Eduardo O.; Berchez, Flávio; Bernardino, Angelo F.; Bosch, Néstor E.; Burdett, Heidi L.; Espino, Fernando; Fernández-Gárcia, Cindy; Francini-Filho, Ronaldo B.; Gagnon, Patrick; Hall-Spencer, Jason M.; Haroun, Ricardo; Hofmann, Laurie C.; Horta, Paulo A.; Kamenos, Nicholas A.; Le Gall, Line; Magris, Rafael A.; Martin, Sophie; Nelson, Wendy A.; Neves, Pedro; Olivé, Irene; Otero-Ferrer, Francisco; Peña, Viviana; Pereira-Filho, Guilherme H.; Ragazzola, Federica; Rebelo, Ana Cristina; Ribeiro, Cláudia; Rinde, Eli; Schoenrock, Kathryn; Silva, João; Sissini, Marina N.; Tâmega, Frederico T. S.

Global marine conservation remains fractured by an imbalance in research efforts and policy actions, limiting progression towards sustainability. Rhodolith beds represent a prime example, as they have ecological importance on a global scale, provide a wealth of ecosystem functions and services, including biodiversity provision and potential climate change mit-igation, but remain disproportionately understudied, compared to other coastal ecosystems (tropical coral reefs, kelp for-ests, mangroves, seagrasses). Although rhodolith beds have gained some recognition, as important and sensitive habitats at national/regional levels during the last decade, there is still a notable lack of information and, consequently, specific conservation efforts. We argue that the lack of information about these habitats, and the significant ecosystem services they provide, is hindering the development of effective conservation measures and limiting wider marine conservation success. This is becoming a pressing issue, considering the multiple severe pressures and threats these habitats are exposed to (e.g., pollution, fishing activities, climate change), which may lead to an erosion of their ecological function and eco-system services. By synthesizing the current knowledge, we provide arguments to highlight the importance and urgency of levelling-up research efforts focused on rhodolith beds, combating rhodolith bed degradation and avoiding the loss of associated biodiversity, thus ensuring the sustainability of future conservation programs.

2023-09Journal article

Restricted access

Editorial: Coralline algae: Past, present, and future perspectives

Publication . Hofmann, Laurie C.; Schoenrock, Kathryn M.; Kamenos, Nicholas A.; Aguirre, Julio; Silva, João; Schubert, Nadine

Following the success of the Frontiers in Marine Science Research Topic on “Coralline Algae: Globally Distributed Ecosystem Engineers,” the Research Topic on “Coralline Algae: Past, Present and Future Perspectives” was launched to extend the opportunity for publishing further knowledge about these diverse ecosystem engineers across a broader time scale. In this Research Topic, an additional nine original research articles have been published, strengthening our understanding of coralline algae past, present, and future, including their biology, physiology and ecology. From reconstructing coralline algal assemblages during the Paleocene/Eocene thermal maximum, to understanding current trophodynamics and benthic-pelagic coupling in rhodolith beds, to assessing the adaptability of coralline algae to future warming, the original research articles in this Research Topic cover a time frame of 55.6 million years and span across an Atlantic biogeographical range from Brazil to the high Arctic.

2022Journal article

Open access

Mapping saltmarsh vertical distribution communities in southern Portugal using high spatiotemporal resolution satellite imagery

Publication . Martins, Márcio; Parreira, Filipe; Ito, Paula; Santos, Rui; Gotha, Simon von sachsen-Coburg Und; Barrena de los Santos, Carmen

Saltmarshes, transitional coastal habitats between terrestrial and marine ecosystems, offer crucial ecological benefits, including coastal protection, biodiversity enhancement, water purification and carbon sequestration. However, saltmarsh areas are shrinking, primarily due to human activities. Traditional monitoring approaches for saltmarsh coverage are often costly and restricted in spatial scope, prompting a shift towards remote sensing techniques. While remote sensing has proven effective for studies that cover large spatial areas, its application for smaller areas remains challenging. In this study, we trained classification models to identify saltmarsh vegetation communities in southern Portugal. We utilized high-resolution (3-metre) and high-frequency (near-daily) imagery to optimize image selection according to tidal conditions at the time of capture and developed an elevation proxy for the intertidal zone. Our model achieved an overall accuracy of 67%, estimating a total of 4,572 ha of saltmarsh in southern Portugal, 85% located in the Ria Formosa lagoon. The middle saltmarsh zone, dominated by Atriplex portulacoides, Salicornia perennis and Salicornia fruticosa, covered the largest area. The approach presented here holds promise for further refinement, enabling automated, high-resolution monitoring of saltmarsh communities, which is essential for conservation and management initiatives.

2025-07-17Journal article

Open access

Rhodolith beds in the eastern tropical pacific: habitat structure and associated biodiversity

Publication . Diaz-Licona, Celeste A.; Schubert, Nadine; González-Gamboa, Vladimir; Tuya, Fernando; Azofeifa-Solano, Juan Carlos; Fernández-García, Cindy

Rhodolith beds (RBs) are globally distributed marine benthic habitats and recognized biodiversity hotspots of conservation interest. However, considerable regions of the world's oceans remain unknown in terms of the presence, distribution, structure, and associated biodiversity of such habitats. In the Eastern Tropical Pacific (ETP), even basic information about these habitats is still extremely scarce. To fill this gap, we characterized the habitat structure and associated biodiversity of four shallow-water RBs at Cocos Island, Costa Rica. Specifically, information regarding rhodolith structural attributes (size, morphology, and CaCO3 content), as well as habitat characteristics (rhodolith nodule density, biomass and CaCO3 standing stocks) were collected. Moreover, the diversity and abundance of associated organisms, including macroalgae, invertebrates and fishes, were determined. Our study shows that Cocos Island harbors dense RBs (1100 to >4500 nodules m(-2)) with substantial carbonate stocks (14-22 kg m(-2)), which provide habitats for a wide array of species (158 recorded species). This study adds 58 new records of RB-associated species to previously published records for the island, which increases the total number of species to 316, including 51 species endemic to the ETP and four species categorized as vulnerable by the IUCN. Our results also indicate that community composition and abundance of organisms vary among RBs, likely due to differences in rhodolith morphologies and sizes and/or local environmental conditions. Further research efforts are warranted to identify the drivers for these differences, as well as expanding studies towards other RBs at Cocos Island and in the ETP in general.

2025-11Journal article

Restricted access