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- Ocean literacy to mainstream ecosystem services concept in formal and informal education: the example of coastal ecosystems of Southern PortugalPublication . Barracosa, Helena; de los Santos, Carmen B.; Martins, Márcio; Freitas, Cátia; Santos, RuiThe concept of ecosystem services (ES) emerges as strategic to explain the influences that the ocean, and in particular coastal ecosystems, have on us and how we influence them back. Despite being a term coined several decades ago and being already widespread in the scientific community and among policy-makers, the ES concept still lacks recognition among citizens and educators. There is therefore a need to mainstream this concept in formal education and through Ocean Literacy resources. Although important developments in OL were done in the United States, particularly through the National Marine Educators Association (NMEA), this concept was only recently introduced in Europe. In Portugal, several informal OL education programs were developed in the last years, yet formal education on OL and, in particular, on ES is still very deficient. To address this limitation, the "Environmental Education Network for Ecosystem Services" (REASE), founded in 2017 in the Algarve region by a consortium of educational, environmental and scientific institutions, aims to increase OL through the dissemination of the perspective of how ES provided by coastal vegetation may contribute to the human well-being. The projects and activities implemented by REASE focus mostly on formal-education of school children and include: (1) capacity building for K-12 teachers, (2) educational programs to support and develop ES projects in schools, including a citizen science project to evaluate blue carbon stocks in the Algarve, (3) the publication of a children's book about the ES provided by the local Ria Formosa coastal lagoon, with a community-based participatory design (illustrations made by schoolchildren) and (4) a diverse array of informal education activities to raise awareness on the importance of coastal ecosystems on human well-being. REASE challenges are being successfully addressed by identifying threats to local coastal ecosystems that people worry about, and highlighting solutions to improve and maintain their health.
- Sedimentary organic carbon and nitrogen sequestration across a vertical gradient on a temperate wetland seascape Including salt marshes, seagrass meadows and rhizophytic macroalgae bedsPublication . Barrena de los Santos, Carmen; Egea, Luis G.; Martins, Márcio; Santos, Rui; Masqué, Pere; Peralta, Gloria; Brun, Fernando G.; Jiménez-Ramos, RocíoCoastal wetlands are key in regulating coastal carbon and nitrogen dynamics and contribute significantly to climate change mitigation and anthropogenic nutrient reduction. We investigated organic carbon (OC) and total nitrogen (TN) stocks and burial rates at four adjacent vegetated coastal habitats across the seascape elevation gradient of Cádiz Bay (South Spain), including one species of salt marsh, two of seagrasses, and a macroalgae. OC and TN stocks in the upper 1 m sediment layer were higher at the subtidal seagrass Cymodocea nodosa (72.3 Mg OC ha−1, 8.6 Mg TN ha−1) followed by the upper intertidal salt marsh Sporobolus maritimus (66.5 Mg OC ha−1, 5.9 Mg TN ha−1), the subtidal rhizophytic macroalgae Caulerpa prolifera (62.2 Mg OC ha−1, 7.2 Mg TN ha−1), and the lower intertidal seagrass Zostera noltei (52.8 Mg OC ha−1, 5.2 Mg TN ha−1). The sedimentation rates increased from lower to higher elevation, from the intertidal salt marsh (0.24 g cm−2 y−1) to the subtidal macroalgae (0.12 g cm−2 y−1). The organic carbon burial rate was highest at the intertidal salt marsh (91 ± 31 g OC m−2 y−1), followed by the intertidal seagrass, (44 ± 15 g OC m−2 y−1), the subtidal seagrass (39 ± 6 g OC m−2 y−1), and the subtidal macroalgae (28 ± 4 g OC m−2 y−1). Total nitrogen burial rates were similar among the three lower vegetation types, ranging from 5 ± 2 to 3 ± 1 g TN m−2 y−1, and peaked at S. maritimus salt marsh with 7 ± 1 g TN m−2 y−1. The contribution of allochthonous sources to the sedimentary organic matter decreased with elevation, from 72% in C. prolifera to 33% at S. maritimus. Our results highlight the need of using habitat-specific OC and TN stocks and burial rates to improve our ability to predict OC and TN sequestration capacity of vegetated coastal habitats at the seascape level. We also demonstrated that the stocks and burial rates in C. prolifera habitats were within the range of well-accepted blue carbon ecosystems such as seagrass meadows and salt marshes.
- Sedimentary organic carbon and nitrogen stocks of intertidal seagrass meadows in a dynamic and impacted wetland: Effects of coastal infrastructure constructions and meadow establishment timePublication . Casal-Porras, Isabel; de los Santos, Carmen B.; Martins, Márcio; Santos, Rui; Pérez-Lloréns, J. Lucas; Brun, Fernando G.Seagrass meadows, through their large capacity to sequester and store organic carbon in their sediments, contribute to mitigate climatic change. However, these ecosystems have experienced large losses and degrada-tion worldwide due to anthropogenic and natural impacts and they are among the most threatened ecosystems on Earth. When a meadow is impacted, the vegetation is partial-or completely lost, and the sediment is exposed to the atmosphere or water column, resulting in the erosion and remineralisation of the carbon stored. This paper addresses the effects of the construction of coastal infrastructures on sediment properties, organic carbon, and total nitrogen stocks of intertidal seagrass meadows, as well as the size of such stocks in relation to meadow establishing time (recently and old established meadows). Three intertidal seagrass meadows impacted by coastal constructions (with 0% seagrass cover at present) and three adjacent non-impacted old-established meadows (with 100% seagrass cover at present) were studied along with an area of bare sediment and two recent-established seagrass meadows. We observed that the non-impacted areas presented 3-fold higher per-centage of mud and 1.5 times higher sedimentary organic carbon stock than impacted areas. Although the impacted area was relatively small (0.05-0.07 ha), coastal infrastructures caused a significant reduction of the sedimentary carbon stock, between 1.1 and 2.2 Mg OC, and a total loss of the carbon sequestration capacity of the impacted meadow. We also found that the organic carbon stock and total nitrogen stock of the recent -established meadow were 30% lower than those of the old-established ones, indicating that OC and TN accu-mulation within the meadows is a continuous process, which has important consequences for conservation and restoration actions. These results contribute to understanding the spatial variability of blue carbon and nitrogen stocks in coastal systems highly impacted by urban development.
- Seagrass meadows improve inflowing water quality in aquaculture pondsPublication . de los Santos, Carmen B.; Olivé, Irene; Moreira, Márcio; Silva, André; Freitas, Cátia; Araújo Luna, Ravi; Quental-Ferreira, Hugo; Martins, Márcio; Costa, Monya; Silva, João; Cunha, Maria Emilia; Soares, Florbela; Pousão-Ferreira, Pedro; Santos, RuiWater quality is critical for fish health in aquaculture production. In flow-through systems, the inflowing water normally requires quality controls and treatments for being supplied from coastal water bodies that can be polluted by nutrients, suspended solids, and microorganisms. Here we assess how seagrass meadows benefit aquaculture systems through the provision of ecosystem services (water filtration, biological control, and regulation of dissolved gasses) in the water reservoir that supplies earthen ponds in an aquaculture system in southern Portugal. In the 1.45-ha reservoir, seagrasses retained daily an estimate of 0.8–1.8 kg d−1 of nitrogen, 0.04–0.07 kg d−1 of phosphorus in their biomass, and 0.7–1.1 kg dw d−1 of suspended total particulate matter, bringing benefits in terms of nutrient and particle removal from the water column. Diel and spatial variation in faecal coliforms levels (Escherichia coli) in the reservoir suggested that seagrasses, in combination with light exposure, may reduce the levels of this pathogen. Furthermore, the seagrass-dominated system oxygenated the water through photosynthesis at a faster rate than the respiratory oxygen consumption, maintaining the system above the aquaculture minimum oxygen. This study demonstrates that seagrasses can be used as a nature-based solution to overcome water quality challenges in flow-through aquaculture ponds.
- Superficial sedimentary stocks and sources of carbon and nitrogen in coastal vegetated assemblages along a flow gradientPublication . Santos, Rui; Duque-Núñez, Natalia; de los Santos, Carmen B.; Martins, Márcio; Carrasco, A. Rita; Veiga-Pires, CristinaCoastal vegetated ecosystems are major organic carbon (OC) and total nitrogen (TN) sinks, but the mechanisms that regulate their spatial variability need to be better understood. Here we assessed how superficial sedimentary OC and TN within intertidal vegetated assemblages (saltmarsh and seagrass) vary along a flow gradient, which is a major driver of sediment grain size, and thus of organic matter (OM) content. A significant relationship between flow current velocity and OC and TN stocks in the seagrass was found, but not in the saltmarsh. OC and TN stocks of the saltmarsh were larger than the seagrass, even though that habitat experiences shorter hydroperiods. Mixing models revealed that OM sources also varied along the flow gradient within the seagrass, but not in the saltmarsh, showing increasing contributions of microphytobenthos (17-32%) and decreasing contributions of POM (45-35%). As well, OM sources varied vertically as microphytobenthos contribution was highest at the higher intertidal saltmarsh (48%), but not POM (39%). Macroalgae, seagrass and saltmarsh showed low contributions. Local trade-offs between flow current velocities, hydroperiod and structural complexity of vegetation must be considered, at both horizontal and vertical (elevation) spatial dimensions, for better estimates of blue carbon and nitrogen in coastal ecosystems.
- Carbon and nitrogen stocks and burial rates in intertidal vegetated habitats of a Mesotidal coastal lagoonPublication . Martins, Márcio; de los Santos, Carmen B.; Masqué, Pere; Carrasco, A. Rita; C. Veiga-Pires, C.; Santos, RuiCoastal vegetated ecosystems such as saltmarshes and seagrasses are important sinks of organic carbon (OC) and total nitrogen (TN), with large global and local variability, driven by the confluence of many physical and ecological factors. Here we show that sedimentary OC and TN stocks of intertidal saltmarsh (Sporobolus maritimus) and seagrass (Zostera noltei) habitats increased between two- and fourfold along a decreasing flow velocity gradient in Ria Formosa lagoon (south Portugal). A similar twofold increase was also observed for OC and TN burial rates of S. maritimus and of almost one order of magnitude for Z. noltei. Stable isotope mixing models identify allochthonous particulate organic matter as the main source to the sedimentary pools in both habitats (39–68%). This is the second estimate of OC stocks and the first of OC burial rates in Z. noltei, a small, fast-growing species that is widely distributed in Europe (41,000 ha) and which area is presently expanding (8600 ha in 2000s). Its wide range of OC stocks (29–99 Mg ha-1 ) and burial rates (15–122 g m2 y-1 ) observed in Ria Formosa highlight the importance of investigating the drivers of such variability to develop global blue carbon models. The TN stocks (7–11 Mg ha-1 ) and burial rates (2–4 g m-2 y-1 ) of Z. noltei were generally higher than seagrasses elsewhere. The OC and TN stocks (29–101 and 3–11 Mg ha-1 , respectively) and burial rates (19–39 and 3–5 g m-2 y-1 ) in S. maritimus saltmarshes are generally lower than those located in estuaries subjected to larger accumulation of terrestrial organic matter.
- Vertical intertidal variation of organic matter stocks and patterns of sediment deposition in a mesotidal coastal wetlandPublication . de los Santos, Carmen B.; Lahuna, François; Silva, André; Freitas, Cátia; Martins, Márcio; Carrasco, A. Rita; Santos, RuiTidal coastal wetlands, common home to seagrass and salt marshes, are relevant carbon sinks due to their high capacity to accumulate and store organic carbon in their sediments. Recent studies demonstrated that the spatial variability of this organic carbon within the same wetland system can be significant. Some of the environmental drivers of this spatial variability remain understudied and the selection of the most relevant ones can be context dependent. Here we investigated the role of bed elevation, hydrodynamics, and habitat type (salt marsh and seagrass) on the organic matter (OM) net deposition-resuspension rate and superficial sedimentary stocks (top 5 cm) at the tidal wetlands of the Ria Formosa, a mesotidal coastal lagoon in South Portugal. Results showed that two vectors of spatial variation need to be considered to describe the intertidal sedimentary OM stocks: the bed elevation that imposes a decrease of the hydroperiod and thus the change of habitat from the lower seagrass Z. noltei to the upper saltmarsh S. maritimus, and the horizontal spatial variation along the secondary channels of the lagoon that imposes a decrease in the current flow velocity magnitude. The multiple linear regression analyses, using data from 40 sampling points, explained 59% of the variation of the superficial sedimentary stocks of OM in salt marshes and seagrasses of the Ria Formosa lagoon and revealed that stocks generally decrease with elevation, yet with variation among sites and habitats. It was also found that the decrease of the OM net deposition-resuspension rate with bed elevation was exponential. Our study emphasizes the importance of considering multiple environmental drivers and spatial variation for regional estimations of organic matter (and organic carbon) sedimentary stocks in coastal wetlands.
- Seagrasses in coastal wetlands of the Algarve region (southern Portugal): past and present distribution and extentPublication . Ito, Paula; Martins, Márcio; von Sachsen-Coburg und Gotha, Simon; Santos, Rui; Barrena de los Santos, CarmenThe global biodiversity crisis urges to update the distribution maps of natural habitats, especially those that are in rapid decline and play a key role in ecosystem functioning, such as seagrasses. In Portugal, seagrass meadows have declined substantially since the 1980s and are considered one of the most endangered marine habitats. Here we aimed to 1) compile records on the distribution and area extent of seagrass meadows in the four wetlands of the Algarve region (southern Portugal) with historical occurrence of seagrasses, based on a systematic review, and 2) update the distribution maps and area extent of seagrass meadows in this region using a combination of manual and machine learning mapping techniques. The systematic review showed a general lack of data on the distribution of seagrass meadows in the Algarve, with patchy information at different times and using incomparable mapping techniques. Based on the updated mapping from 2019 to 2023, well-developed seagrass meadows were only found in the Ria Formosa lagoon and the Guadiana estuary. In the Ria de Alvor, some sparce scattered patches of seagrass were observed in the intertidal zone, while no seagrass was found in the Arade estuary. The total extent of seagrass in the Algarve region was estimated at 1231 ha, with nearly all (99 %) occurring in the Ria Formosa, where 85 % was intertidal. Although assessing temporal trends remains challenging due to methodological differences and data limitations, the estimated 20 % decline and ongoing pressures on seagrass meadows in Algarve wetlands underscore the urgent need for continuous, standardized monitoring of their distribution, extent, and condition.
- Mapping saltmarsh vertical distribution communities in southern Portugal using high spatiotemporal resolution satellite imageryPublication . Martins, Márcio; Parreira, Filipe; Ito, Paula; Santos, Rui; Gotha, Simon von sachsen-Coburg Und; Barrena de los Santos, CarmenSaltmarshes, 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.