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Zostera capensis is an African seagrass that is endangered throughout its range. In South Africa, it is solely confined to low wave energy estuarine habitats and characterised by two evolutionary lineages that diverge across a biogeographic transition. In this study, we sampled seagrass plants from five populations that span the region of lineage divergence and investigated the extent of lineage overlap. Using 2681 SNP loci, including 32 putative outlier loci, we calculated population structure, genomic diversity and levels of admixture. All populations were significantly different to each other, including those < 10 km apart and low levels of admixture indicate limited dispersal of Z. capensis. Every population was characterised by a high inbreeding coefficient (FIS), suggesting a limited number of breeding individuals in each population. Given increasing anthropogenic stressors that are linked to declines in seagrass meadow cover in South Africa, our study provides strong support that populations of this endangered seagrass require targeted management and conservation actions of each individual population to avoid further loss of the unique evolutionary dynamics and to safeguard the ecosystem services seagrasses provide. Further, our evidence of significant population structure across geographically close populations highlights that conservation efforts relying on seagrass restoration would risk mixing unique evolutionary signatures of Z. capensis in the region when transplanting between estuaries. This represents a critical challenge to using transplants as a potential mechanism of restoring declining populations and highlights the crucial importance of preventing population extinction. [ABSTRACT FROM AUTHOR]

Between 1973 and 2023, a total of 63 species had been protected in Turkish marine areas according to national legislation 1380 (Official Notice for Regulating Commercial Fisheries of Water Resources, No. 5/1). Notably, sturgeon species were at the forefront of these conservation efforts, with initiatives beginning in 1976 and continuing to the present day. Among marine flora, only two species (Posidonia oceanica and Zostera noltii) were granted protected status, while the other species were not accorded such protection. The protected fauna included 13 marine mammal species and 22 species of sharks and rays, the latter representing the most extensively protected category. In addition, three species of sea turtles, seven species of corals, six species of mollusks, one species of crustaceans, and three species of fish are also under protection. Comprehensive details regarding the years when these species were protected, the rationale behind their protection, their IUCN Red List statuses, and the institutions advocating for their protection are summarized. Turkish Marine Research Foundation (TUDAV) has been the main driver for the protection of sharks and rays, corals, and mollusks, successfully placing 18 species under protection in recet years. The first coralligenous species to be protected was the black coral Savalia savaglia, while the first size limitation was established for Huso huso, and the first protected species was the Mediterranean monk seal (Monachus monachus). [ABSTRACT FROM AUTHOR]

Dwarf eelgrass, Zostera noltii, is an important ecosystem engineer that creates dense meadows along the coasts of Europe and Northwest Africa. During the last century, this seagrass species suffered severe population declines, and to counteract these losses, restoration has emerged as an important management tool. Thus far, restoration efforts with Z. noltii have only been performed with shoot‐ and core‐based methods, which are challenging to upscale sustainably.Here, we explored if Z. noltii can be restored with seeds, thus potentially offering an upscalable solution for future restoration efforts. With the newly developed dispenser injection seeding (DIS) method, we tried seed‐based Z. noltii restoration in the intertidal Wadden Sea. With a field experiment, we investigated how seeding depth (1.5 and 3 cm) and seed amount (5, 10 and 20 seeds/injection) affected Z. noltii recruitment success and efficiency.Most importantly, our results show that Z. noltii can be restored with seeds, as 3 months after seeding, 184 individual patches had emerged from our 7000 seeds (2.6% recruitment). Recruitment success (number of restored patches/plot) was enhanced by higher seed amounts (20 > 5 seeds/injection), while the opposite was true for recruitment efficiency (number of restored patches/seed), which was reduced by higher seed amounts (20 < 5 seeds/injection). Restored Z. noltii survived the first winter in all experimental plots, but seagrass cover (square metre/plot) reduced in two‐thirds of the plots compared to the first growing season.In conclusion, our findings show the potential of seed‐based Z. noltii restoration and provide insights on how upscaling of restoration efforts for this species can be performed more efficiently and sustainably in the future. [ABSTRACT FROM AUTHOR]

Marine foundation species underpin some of the world's most diverse ecosystems but they are increasingly threatened by intensification of marine heatwaves (MHWs). Where MHWs exceed critical thermal maxima (CTmax), increased mortality and population declines can occur. CTmax is increasingly used to assess MHW population vulnerability but studies estimating CTmax across species, range edges and thermal histories in a comparable manner remain lacking. We determined the impact of MHWs on subsequent CTmax estimates of matched cool/warm affinity pairs of marine foundation species (kelp, seagrass and bivalves) in the Western English Channel. Following a 4‐week MHW simulation, individuals were subjected to a CTmax trial, where temperatures were raised by 2°C day−1 until physiological end points were reached. We found no positive effect of MHWs on CTmax but clear negative impacts were observed for some groups of foundation species. Increased MHW intensity had a stepwise negative impact on the physiology of both warm (Laminaria ochroleuca) and cool water (L. digitata) kelp species that manifested in significant reductions in CTmax. Surprisingly, this was most marked in the warm water species, which runs opposite to the assumed safety of leading‐edge populations. The physiology of warm (Zostera noltii) and cool (Z. marina) seagrasses was negatively impacted by increasing MHW intensity but no significant decrease in CTmax was observed. Both bivalve species (Mytilus edulis and Magallana gigas) showed marked resistance to exposure to MHWs, which was unexpected given the observed vulnerability of these species to stressful summertime conditions. Our results show pre‐exposure to realistic MHWs can influence CTmax values but generalities are difficult to make across groups or based on assumed thermal safety margins. We show CTmax is a labile trait and exposure to MHWs, can erode the resilience of an individual or population to subsequent thermal challenges. This leaves uncertainty within frameworks built to understand where and when MHWs will be most impactful. Further experimentation across a wider range of species and thermal challenges is needed to better understand the dynamic nature of CTmax and field validation is needed to determine the responses of individuals and populations within complex natural systems. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Worldwide seagrass habitats are under severe anthropogenic threat. In the United Kingdom (UK), the health of habitats of the widely distributed Zostera species is particularly threatened by eutrophication that can lead to detrimental macroalgae overgrowth. To manage and conserve seagrass habitats, effective monitoring tools are required.We use an off‐the‐shelf consumer‐grade multispectral (RGB, red edge, and near‐infrared) camera mounted on an unoccupied aerial vehicle (UAV) to map an intertidal multispecies seagrass environment in Lindisfarne National Nature Reserve, Northumberland, UK.Field surveys were undertaken of three seagrass areas, including those dominated by Zostera noltii, Zostera marina and macroalgae. Using the Maximum Likelihood Classifier (MLC), results indicated an overall accuracy (OA) between 84% and 91% across classified habitat maps. As expected, the red edge and near‐infrared bands offered an advantage beyond RGB imagery to discriminate between the vegetation types for accurate habitat mapping.Our research provides a foundation for accurately mapping a complex intertidal seagrass environment through the utilisation of an off‐the‐shelf multispectral UAV. The study may aid the implementation and development of effective monitoring programmes for the management of Zostera spp. decline and macroalgae proliferation to prevent seagrass degradation and conserve these valuable yet fragile ecosystems. [ABSTRACT FROM AUTHOR]

Coastal vegetated ecosystems including mangroves, seagrasses, and salt marshes are often shaped by positive plant–environment feedbacks. Plants improve their own living conditions with increasing patch size and density by attenuating hydrodynamics and stabilizing sediments. As these habitat modifications are critical for survival and growth, the positive density‐dependent nature of these feedbacks can lead to establishment thresholds for young plants in absence of mature conspecifics. Although feedback strength is known to depend on hydrodynamic exposure and plant traits (e.g. stiff versus flexible stems), it remains unclear how 1) opposing morphological plant traits affect establishment in contrasting environments, and 2) whether trait plasticity influences establishment success. Here, we investigate this by transplanting two tidal species with opposing growing strategies – Spartina anglica forms tussocks of stiff stems while Zostera noltii forms patches of stress‐avoiding flexible shoots – from two different donor sites in eight experimental locations. Results show that the survival and growth of both species was most successful at field locations with diverging environmental characteristics, while overall survival was highest for Z. noltii. Mainly, S. anglica survival was highest at locations with high organic matter and silt content and higher elevation relative to the tidal amplitude. In contrast, Z. noltii survival was highest at locations with larger grainsize and lower relative elevations. Furthermore, despite initial differences in plant traits between the two donor sites of Z. noltii, we found no effects of donor origin. Contrastingly, we found a significant effect of donor origin on S. anglica growth, even though transplants from the two donor sites showed no initial trait differences. Collectively, these results suggest that the stress‐tolerance strategy of S. anglica hampers establishment in exposed conditions, whereas the stress‐avoiding Z. noltii appears to be more susceptible to stress from desiccation and silty sediments. [ABSTRACT FROM AUTHOR]

Ecological restoration has become an important management-tool to counteract the widespread losses of seagrass meadows and their associated biodiversity. In the Dutch Wadden Sea, long-term restoration efforts have recently led to the successful restoration of annual eelgrass (Zostera marina) at high densities on a local scale. However, it is yet unknown if restored seagrass plants also lead to improved local biodiversity and ecosystem functioning in the intertidal zone. We therefore compared the macrozoobenthos communities of a small-scale restored meadow to 22 naturally occurring intertidal seagrass meadows. Using a taxonomic and traitbased approach we aimed to study 1) how intertidal seagrasses (Zostera marina and Zostera noltii) affect benthic communities and their functional trait distribution and 2) if a restoredmeadowfacilitates benthic communities similar to natural meadows. We found that both natural and restored seagrasses increased abundances of benthic animals and the richness (both taxonomic and functional) of associated benthic communities compared to nearby unvegetated areas. Additionally, the presence of intertidal seagrass shifted benthic community composition both taxonomically and functionally, thus broadening the niche space for species inhabiting tidal flats. Seagrasses especially facilitated epifaunal species and traits associated with these animals. Surprisingly, our results indicate that the mere presence of seagrass aboveground structure is enough to facilitate benthic communities, as neither higher seagrass cover nor biomass increased benthic biodiversity in the intertidal zone. By studying the effect of seagrass restoration on benthic diversity, we found that the restoredmeadow functioned similarly to the natural meadows after only two years and that the success of our restoration efforts indeed led to local biodiversity enhancements. Our findings contribute to the understanding of the ecological functioning of intertidal seagrasses and can be used to define/refine conservation and restoration goals of these valuable ecosystems. [ABSTRACT FROM AUTHOR]

Together with increasing environmental and anthropogenic pressures, pathogenic diseases are one of the important factors contributing to the ongoing decline of seagrass meadows worldwide; yet the diversity and ecology of the microorganisms acknowledged as seagrass parasites remain critically understudied. Here, we investigate phytomyxid parasites (Rhizaria: Endomyxa: Phytomyxea) of three different eelgrass (Zostera spp.) species found in the Northern hemisphere. We present molecular evidence that Plasmodiophora bicaudata, a long‐recognized parasite of dwarf eelgrass taxa, is closely related to the novel phytomyxid recently discovered in root hairs of Zostera marina, and together they form a distinct clade within the order Phagomyxida, proposed here as Feldmanniella gen. nov. A full life cycle is systematically described in a phagomyxid representative for the first time, proving its conformity with the generalized phytomyxid life history, despite previous uncertainties. The presence of primary infection stages in nearly all collected eelgrass specimens, and subsequent analysis of amplicon sequences from a global Z. marina dataset, reveal phytomyxids to be ubiquitous and one of the predominant microeukaryotes associated with eelgrass roots on a global scale. Our discoveries challenge the current view of Phytomyxea as rare entities in seagrass meadows and suggest their generally low pathogenicity in natural ecosystems. [ABSTRACT FROM AUTHOR]

Coastal ecosystem functioning often hinges on habitat‐forming foundation species that engage in positive interactions (e.g. facilitation and mutualism) to reduce environmental stress. Seagrasses are important foundation species in coastal zones but are rapidly declining with losses typically linked to intensifying global change‐related environmental stress. There is growing evidence that loss or disruption of positive interactions can amplify coastal ecosystem degradation as it compromises its stress mitigating capacity. Multiple recent studies highlight that seagrass can engage in a facultative mutualistic relationship with lucinid bivalves that alleviate sulphide toxicity. So far, however, the generality of this mutualism, and how its strength and relative importance depend on environmental conditions, remains to be investigated. Here we study the importance of the seagrass‐lucinid mutualistic interaction on a continental‐scale using a field survey across Europe. We found that the lucinid bivalve Loripes orbiculatus is associated with the seagrasses Zostera noltii and Zostera marina across a large latitudinal range. At locations where the average minimum temperature was above 1 °C, L. orbiculatus was present in 79% of the Zostera meadows; whereas, it was absent below this temperature. At locations above this minimum temperature threshold, mud content was the second most important determinant explaining the presence or absence of L. orbiculatus. Further analyses suggest that the presence of the lucinids have a positive effect on seagrass biomass by mitigating sulphide stress. Finally, results of a structural equation model (SEM) support the existence of a mutualistic feedback between L. orbiculatus and Z. noltii. We argue that this seagrass‐lucinid mutualism should be more solidly integrated into management practices to improve seagrass ecosystem resilience to global change as well as the success of restoration efforts. [ABSTRACT FROM AUTHOR]

Seagrasses are marine flowering plants that play crucial roles in blue carbon capture and coastal protection, as well as providing a critical feeding and nursery habitat for several species. However, the extent of seagrass meadows has drastically decreased around the UK coastline since the 1930s. As such, restoration of Zostera spp. seagrasses is a growing field for academics and practitioners, yet for Zostera noltei (dwarf eelgrass) in particular, restoration is hampered by knowledge of current distributions and where to restore. Habitat suitability modelling is a valuable tool for mapping and can be applied by practitioners at a site-specific scale to identify potential areas for restoration. Here we have created a Maximum Entropy (maxent) habitat suitability model to predict Z. noltei suitability in the Greater Thames Estuary based on seven environmental variables at a 10-m resolution within an intertidal boundary. Using areas of higher suitability to identify restoration potential, our results indicate 602.9 Ha of "good" suitable habitat for potential restoration around existing Z. noltei beds in the Thames, Medway and Swale Estuaries. Despite reasonable predictive accuracy, our model was limited by the availability, resolution and extent of important environmental variables such as sediment type. Nonetheless, we believe this is a valuable tool for practitioners in the initial stage of site selection at a local scale for Z. noltei restoration projects in the UK. • A maxent habitat suitability model for Zostera noltei was created for a UK estuary. • Seven variables were used in model construction at a 10 m resolution. • Distance to shore and 50 m resolution slope contributed most to the model. • 603 Ha of "good" intertidal seagrass habitat identified for potential restoration. • Model predicts a picture of connectivity for intertidal seagrass in the Thames. [ABSTRACT FROM AUTHOR]

Keywords: Eastern Mediterranean Sea; Posidonia oceanica; satellite; seagrass; sidescan sonar; wide-scale mapping EN Eastern Mediterranean Sea Posidonia oceanica satellite seagrass sidescan sonar wide-scale mapping 289 299 11 08/09/22 20220801 NES 220801 1 Introduction Seagrasses constitute a group of submerged flowering plants that can be found in shallow marine and brackish waters in many parts of the world, from the tropics to the Arctic Circle ([17]; [43]). In this plot, a more homogeneous coverage pattern emerges, with a mean of 0.25 ± 0.13 km SP 2 sp of seagrass meadow per km of coastline in all mapped meadows of the N. Aegean Sea. An effort to map Greek meadows using only satellite data by [41] led to an estimate of 2613.88 km SP 2 sp of seagrass meadows. 3 Results and discussion 3.1 Spatial distribution and surface area of seagrass meadows The presence of seagrass meadows was recorded along approximately 70% of the Greek coastline, with their total areal extent estimated at 2749.07 km SP 2 sp . [Extracted from the article]

For example, rainfall was shown to enhance seagrass biomass in an Australian seagrass meadow on Mabuiag Island (where the seagrass community includes species from the genera I Cymodocea, Halodule, Thalassia, Halophila, Enhalus, i and I Syringodium i ) throughout a 30-day trial ([92]). Organic carbon in seagrass sediments is influenced by seagrass canopy complexity, turbidity, wave height, and water depth. Keywords: chlorophyll a fluorescence; factorial experiment; growth rate; North Aegean Sea; seagrass EN chlorophyll a fluorescence factorial experiment growth rate North Aegean Sea seagrass 301 313 13 08/09/22 20220801 NES 220801 1 Introduction Seagrasses are flowering, rooted plants that form extensive meadows in shallow sandy to muddy coastal waters worldwide ([39]), receiving about 10-20% of the incident irradiance at the water surface ([31]; [32]). I Cymodocea nodosa i (Ucria) Ascherson is a common seagrass species in the Mediterranean Sea and in the Canary Isles ([32]) that grows relatively fast compared to other seagrass genera ([94]). High-salinity brine discharges from seawater desalination plants can also negatively impact seagrass meadows [103]. [Extracted from the article]

Simple Summary: Expected climate change scenarios will have inevitable and important impacts on key foundation marine species such as seagrasses. This study was aimed to understand how the dwarf eelgrass Zostera noltii leaf lipid landscapes are altered under predicted ocean warming (+4 °C) and acidification (ΔpH 0.4) conditions. A severe reduction in the leaf total fatty acid (FA) content was observed in seagrasses individually exposed to hypercapnic or warming conditions, and this depletion was ameliorated under combined exposure to ocean warming and acidification conditions. The tested treatments also impacted the FA composition of all lipid classes, with warming exposure leading to decreases in polyunsaturated fatty acids (PUFAs). Galactolipid remodeling seems to have key roles in the physiological changes observed in seagrasses under these tested conditions, highlighting the higher impact of warming and that the proposed stress alleviation effect induced by increased water-dissolved CO2 availability. Neutral lipids were substantially increased under warming conditions, mainly with increases in C18 FA, impairing their use as substrates to maintain the osmotic balance of the cells. Nonetheless, the pace at which ocean warming is occurring can overcome the ameliorative capacity induced by higher CO2 availability, leaving seagrasses under severe heat stress beyond their lipid-remodeling capacity. Coastal seagrass meadows provide a variety of essential ecological and economic services, including nursery grounds, sediment stabilization, nutrient cycling, coastal protection, and blue carbon sequestration. However, these ecosystems are highly threatened by ongoing climatic change. This study was aimed to understand how the dwarf eelgrass Zostera noltii leaf lipid landscapes are altered under predicted ocean warming (+4 °C) and hypercapnic (ΔpH 0.4) conditions. Warming and hypercapnic conditions were found to induce a severe reduction in the leaf total fatty acid, though the combined treatment substantially alleviated this depletion. The lipid discrimination revealed a significant increase in the relative monogalactosyldiacylglycerol (MGDG) content in both hypercapnic and warming conditions, allied to plastidial membrane stabilization mechanisms. Hypercapnia also promoted enhanced phosphatidylglycerol (PG) leaf contents, a mechanism often associated with thylakoid reinvigoration. In addition to changing the proportion of storage, galacto- and phospholipids, the tested treatments also impacted the FA composition of all lipid classes, with warming exposure leading to decreases in polyunsaturated fatty acids (PUFAs); however, the combination of both stress conditions alleviated this effect. The observed galactolipid and phospholipid PUFA decreases are compatible with a homeoviscous adaptation, allowing for the maintenance of membrane stability by counteracting excessive membrane fluidity. Neutral lipid contents were substantially increased under warming conditions, especially in C18 fatty acids (C18), impairing their use as substrates for fatty acylated derivatives essential for maintaining the osmotic balance of cells. An analysis of the phospholipid and galactolipid fatty acid profiles as a whole revealed a higher degree of discrimination, highlighting the higher impact of warming and the proposed stress alleviation effect induced by increased water-dissolved CO2 availability. Still, it is essential to remember that the pace at which the ocean is warming can overcome the ameliorative capacity induced by higher CO2 availability, leaving seagrasses under severe heat stress beyond their lipid remodeling capacity. [ABSTRACT FROM AUTHOR]

Seagrass meadows are among the most important coastal ecosystems in terms of both spatial extent and ecosystem services, but they are also declining worldwide. Understanding the drivers of seagrass meadow dynamics is essential for designing sound management, conservation and restoration strategies. However, poor knowledge of the effect of clonality on the population genetics of natural populations severely limits our understanding of the dynamics and connectivity of meadows. Recent modelling approaches have described the expected distributions of genotypic and genetic descriptors under increasing clonal rates, which may help us better understand and interpret population genetics data obtained for partial asexuals. Here, in the light of these recent theoretical developments, we revisited population genetics data for 165 meadows of four seagrass species. Contrasting shoot lifespan and rhizome turnover led to the prediction that the influence of asexual reproduction would increase along a gradient from Zostera noltii to Zostera marina, Cymodocea nodosa and Posidonia oceanica, with increasing departure from Hardy–Weinberg equilibrium (Fis), mostly towards heterozygote excess, and decreasing genotypic richness (R). This meta‐analysis provides a nested validation of this hypothesis at both the species and meadow scales through a significant relationship between Fis and R within each species. By empirically demonstrating the theoretical expectations derived from recent modelling approaches, this work calls for the use of Hardy–Weinberg equilibrium (Fis) rather than only the strongly sampling‐sensitive R to assess the importance of clonal reproduction (c), at least when the impact of selfing on Fis can be neglected. The results also emphasize the need to revise our appraisal of the extent of clonality and its influence on the dynamics, connectivity and evolutionary trajectory of partial asexuals in general, including in seagrass meadows, to develop the most accurate management strategies. [ABSTRACT FROM AUTHOR]

Holothuria arguinensis aquaculture started to be developed in 2014, being the first sea cucumber species from Europe. However, some aspects of its aquaculture biotechnology, such diets, need to be assessed. This work aimed to evaluate seagrass debris of Zostera noltii and Cymodocea nodosa as food source for broodstock maintenance in tanks, during breeding periods. The given feed rations per tank were calculated as the 30% of the total sea cucumber biomass in each tank and reviewed each week. Then, feed rations of seagrass and sediment were calculated from this value, according to the following percentages: 40% sediment, 15% Z. noltii, 40% Z. noltii, 15% C. nodosa and 40% C. nodosa. H. arguinensis growth, feeding rate and nutritional value were assessed under these diets. H. arguinensis fed with 40% of Z. noltii showed the highest growth (specific growth rate = 0.09 ± 0.06%/day, absolute growth rate = 0.11 ± 0.07 g/day) increasing their final weight in 5.86 ± 3.57% in 57 days. However, the individuals fed with C. nodosa showed a negative growth. H. arguinensis showed a reduction in its feeding rate as the organic matter content in the diets increased. H. arguinensis did not show any important change on proximate composition, protein, lipid, mineral contents and fatty acids profile among the feeding groups, or in comparison with the individuals collected from wild habitat. Therefore, H. arguinensis could be fed with Z. noltii debris during tanks maintenance along breeding period, ensuring its growth and maintaining its nutritional profile. [ABSTRACT FROM AUTHOR]

Eutrophication causes tremendous losses to seagrass around the globe. The effects of nutrient loading vary along environmental gradients, and wave forces especially are expected to affect meadow stability, nutrient status, and responses to nutrient supply. Here, we surveyed the pristine subtropical intertidal seagrass system of Banc d'Arguin, Mauritania, to characterise Zostera noltii in terms of morphology (biomass allocation, leaf length and area, rhizome internode length), nutrient content (carbon: C, nitrogen: N, phosphorus: P, iron: Fe, aluminium: Al), and patterns in δ13C and δ15N across a wide gradient of hydrodynamic conditions. We subsequently assessed temporal variability in seagrass stability and nutrient fluxes, as well as responses to experimental fertilisation (pulses of + N, + P, + N + P) on three meadows representing different degrees of wave-force (exposed, intermediate and sheltered). The large-scale survey revealed a marked increase in N and P limitation with increasing wave energy. The overall low leaf %N (1.74 ± 0.04; mean ± se) and N:P ratio (8.67 ± 0.14) suggests that the area is N-limited. Seasonal variation in seagrass cover and biomass showed the exposed site to be the most stable and the sheltered site the least. Variation in δ15N signatures indicates seasonal shifts in N sources at the exposed site only. Fertilisation with + N and + N + P induced seagrass mortality at the exposed site, while at the sheltered site it was + P that degraded seagrass. Collectively, our results indicate that with increasing wave forces, the degree of stability of seagrass beds increases, but nutrient limitation and vulnerability to eutrophication increase as well. [ABSTRACT FROM AUTHOR]

Understanding sequestration of carbon by coastal ecosystems is central to addressing the role they play in climate change mitigation. To quantify this process, accurate measurements of CO 2 fluctuation, coupled with variations in residence time of coastal water-bodies are required. Nearshore ecosystems, including coastal lagoons, may provide an effective sink for atmospheric carbon dioxide, particularly those containing productive biota such as seagrass. However, the rate and pattern of carbon sequestration in seagrass meadows across a range of environmental settings is still poorly constrained. In this study, we utilize a robust physical tidal model, along with biogeochemical dissolved inorganic carbon (DIC) assessment, to estimate water residence time and net sequestration of atmospheric CO 2 in an intertidal lagoon containing a seagrass (Zostera noltii) meadow. Total alkalinity and pH measurements taken from advected water mass exchanged with the open ocean at inlet boundaries are used to calculate DIC and p CO 2. A predictive model of hydrodynamics provides good approximation of mean water residence time to within 6 h (±3 s.d). Results indicate that during the daytime study period the lagoon is a sink for carbon, having a mean net ecosystem productivity (NEP) of 3.0 ± 0.4 mmol C m−2 hr−1. An equivalent diel NEP range of between 15.23 and −9.24 mmol C m−2 d−1 is calculated based on reported shallow water pelagic respiration rates. Moreover, approximately 4% of DIC availability occurs from atmospheric CO 2 transfer to lagoon water. However, a negative diel rate of −82 ± 81 mmol C m−2 d−1 is found, assuming overnight respiration ascertained from converted Zostera noltii O 2 utilization. We hypothesize that analogous regional nearshore ecosystems provide baseline study sites suitable to elucidate the carbon capture potential of planned, nearby tidal range energy schemes. • Tidal range energy schemes require additional benefits to boost feasibility. • Carbon offsetting could provide an additional income source. • Man-made nearshore lagoons containing seagrass may enhance carbon sequestration. • Results show existing regional lagoons may help elucidate this potential. • High-resolution, multi-disciplinary studies are required to constrain uncertainty. [ABSTRACT FROM AUTHOR]

Seagrass meadows provide several ecological functions that improve the overall ecological health of coastal systems and therefore, it is urgent to promote the restoration of such habitats. In Ria de Aveiro, a coastal lagoon in the Atlantic Coast of Portugal, a restoration initiative was responsible for transplanting the dwarf eelgrass Zostera noltei into a highly degraded area. This eelgrass was used as a nature-based solution (NbS) to mitigate some of the impacts of historical mercury contamination. Comparisons of key-species features (density and biomass), and some community-derived indicators (total density and biomass, species richness and Shannon-Wiener index) between the transplanted seagrass patch, their bare vicinities, and their counterpart habitats on the source area, provided signs of the effectiveness of the restoration action on the benthic communities' recovery. Indicators were higher within the restored meadow, and biomass derived indicators of the restored meadow were similar to the source meadow. • Zostera noltei was used as a nature-based solution to mitigate Hg contamination. • The impact was assessed on key-species, and in community-derived indicators. • Indicators improved in the restored meadow, when compared with the adjacent habitat. • Biomass on the restored meadow was on a par with the source meadow. • Indicators after one year of the transplant are already promising. [ABSTRACT FROM AUTHOR]

The limiting effects of stressors like desiccation, light and salinity on seagrass growth and distribution are well-studied. However, little is known about their interactive effects, and whether such effects might differ among populations that are adapted to different local conditions. In two laboratory experiments we tested (a) if growth and development of intertidal, temperate Zostera noltii is affected by emergence time (experiment 1 and 2), and (b) how this is affected by an additional, second stressor, namely shading (experiment 1) or high salinity (25, 30 and 35, experiment 2). In addition, we tested (c) whether the effects of emergence time and salinity varied between three different European seagrass populations (Saint-Jacut/France, Oosterschelde/The Netherlands, and Sylt/Germany), which are likely adapted to different salinity levels (experiment 2). In both experiments, emergence of 8 h per tidal cycle (of 12 h) had a negative effect on seagrass relative growth rate (RGR), and aboveground biomass. Emergence furthermore reduced either rhizome length (experiment 1) or belowground biomass (experiment 2). Shading (experiment 1) resulted in lower RGR and a two-fold higher aboveground/belowground ratio. We found no interactive effects of emergence and shading stress. Salinity (experiment 2) did not affect seagrass growth or morphology of any of the three populations. The three tested populations differed greatly in morphology but showed no differential response to emergence or salinity level (experiment 2). Our results indicate that emergence time and shading show an additive negative effect (no synergistic or antagonistic effect), making the plants still vulnerable to such combination, a combination that may occur as a consequence of self-shading during emergence or resulting from algal cover. Emergence time likely determines the upper limit of Z. noltii and such shading will likely lower the upper limit. Shading resulted in higher aboveground/belowground ratios as is a general response in seagrass. Z. noltii of different populations originating from salinity 30 and 35 seem tolerant to variations in salinity within the tested range. Our results indicate that the three tested populations show morphotypic rather than ecotypic variation, at least regarding the salinity and emergence, as there were no interactive effects with origin. For restoration, this implies that the salinity regime of the donor and receptor site of Z. noltii is of no concern within the salinity range 25–35.

ABSTRACT Zarranz Elso, M.; Manent, P., and Robaina, R.R., 2018. Zostera noltii in the Canary Islands: A genetic description for conservation purposes. The extremely delicate situation affecting the seagrass Zostera noltii in the Canary Islands (listed as ‘threatened with extinction') requires urgent measures to ensure its preservation. The genetic or genotypic description of populations and knowledge about their connectivity are important genetic issues that should be taken into account to accomplish appropriate conservation and restoration programmes, particularly for threatened habitats or species. Therefore, a genetic characterisation of the single remaining meadow located on the coast of Lanzarote was conducted using nine microsatellite loci, and its genetic relationship with the geographically closest Moroccan populations was studied for restoration purposes. Results showed that the Lanzarote population has recently suffered a significant reduction in effective population size and presents low levels of allelic or genotypic diversity in relation to other Z. noltii populations throughout its distribution range. Moreover, this population remains in an extremely isolated situation in which it lacks long-term gene flow with other Moroccan populations. These genetic factors, together with the lack of sexual reproduction (only vegetative growth via rhizomes has been reported) and high anthropogenic pressures, make the risk of extinction of this species in the Canarian archipelago more likely. Some considerations for future restoration plans for this valuable species are suggested. [ABSTRACT FROM AUTHOR]

Abstract Dwarf eelgrasses (Zostera noltei) populations have decreased since 2005 in Arcachon Bay (southwest France). Various stressors have been pointed out, however the role of xenobiotics like pesticides or copper (Cu) and of parameters like water temperature warming have not yet been explored. To determine their impact, Z. noltei individuals were collected in a pollution-free site and transferred to the laboratory in seawater microcosms. This dwarf eelgrass was exposed to a pesticide cocktail and copper, alone or simultaneously, at temperatures (10 °C, 20 °C, 28 °C) representative of different seasons. After a two-week contamination, leaf growth, leaf bioaccumulation of Cu, and differential expression of target genes were studied. Eelgrasses bioaccumulated Cu regardless of the temperature, with reduced efficiency in the presence of the Cu and pesticide cocktail at the two higher temperatures. High temperature also exacerbated the effect of contaminants, leading to growth inhibition and differential gene expression. Mitochondrial activity was strongly impacted and higher mortality rates occurred. Experimental results have been confirmed during field survey. This is the first report on the impacts on Z. noltei of pesticides and Cu associate to temperature. Highlights • Zostera noltei decline in the Arcachon Bay (southwest France) • Molecular effects of Copper and Pesticides cocktail used alone or mixed • Cu and Pesticides decreased the mitochondrial metabolism and photosynthesis [ABSTRACT FROM AUTHOR]

Abstract There exists limited understanding of the long-term dynamics of the seagrass Zostera noltii and how this is influenced by anthropogenic pressures. Milford Haven is a heavily industrialised estuary and also one of the important sites for Zostera sp. in the UK. In this study we examine all available long-term spatial variability and abundance data of Zostera noltii within Milford Haven using historic datasets. Results show that Z. noltii in all sites have shown meadow expansion when compared to the first obtainable records. Little change in abundance over the past 10–15 years for the two sites confirms certain seagrass populations to be robust and thriving. We hypothesise that these populations are showing a level of resilience to the high nutrient levels, disturbance and high turbidity present within the water column of the Haven. [ABSTRACT FROM AUTHOR]

The limiting effects of stressors like desiccation, light and salinity on seagrass growth and distribution are well-studied. However, little is known about their interactive effects, and whether such effects might differ among populations that are adapted to different local conditions. In two laboratory experiments we tested (a) if growth and development of intertidal, temperate Zostera noltii is affected by emergence time (experiment 1 and 2), and (b) how this is affected by an additional, second stressor, namely shading (experiment 1) or high salinity (25, 30 and 35, experiment 2). In addition, we tested (c) whether the effects of emergence time and salinity varied between three different European seagrass populations (Saint-Jacut/France, Oosterschelde/The Netherlands, and Sylt/Germany), which are likely adapted to different salinity levels (experiment 2). In both experiments, emergence of 8 h per tidal cycle (of 12 h) had a negative effect on seagrass relative growth rate (RGR), and aboveground biomass. Emergence furthermore reduced either rhizome length (experiment 1) or belowground biomass (experiment 2). Shading (experiment 1) resulted in lower RGR and a two-fold higher aboveground/belowground ratio. We found no interactive effects of emergence and shading stress. Salinity (experiment 2) did not affect seagrass growth or morphology of any of the three populations. The three tested populations differed greatly in morphology but showed no differential response to emergence or salinity level (experiment 2). Our results indicate that emergence time and shading show an additive negative effect (no synergistic or antagonistic effect), making the plants still vulnerable to such combination, a combination that may occur as a consequence of self-shading during emergence or resulting from algal cover. Emergence time likely determines the upper limit of Z. noltii and such shading will likely lower the upper limit. Shading resulted in higher aboveground/belowground ratios as is a general response in seagrass. Z. noltii of different populations originating fromsalinity 30 and 35 seem tolerant to variations in salinity within the tested range. Our results indicate that the three tested populations show morphotypic rather than ecotypic variation, at least regarding the salinity and emergence, as there were no interactive effects with origin. For restoration, this implies that the salinity regime of the donor and receptor site of Z. noltii is of no concern within the salinity range 25-35. [ABSTRACT FROM AUTHOR]

Wastewater pulses from rice agriculture are persistently discharged into the northern shore of the Alfacs Bay (Ebro Delta, NW Mediterranean) from April to November. The bay also receives water from coastal lagoons which are subjected to freshwater inputs from the Ebro River mixed to an unknown extent with agricultural wastewater during the same period. This paper compares epiphyte assemblages growing on leaves of Cymodocea nodosa in sites exposed to agricultural drainage channels, lagoon connection channels, and control sites in the Ebro Delta Natural Park (southern shore of the bay). Leaf epiphytic assemblages of Zostera noltii patches in the northern shore of the bay were also compared with those of adjacent beds of C. nodosa . Drainage channel sites had consistently distinctive assemblages (higher species richness, biomass load, and taxa composition) than control sites. Assemblages from lagoon channel sites were more variable, with three sites showing particularly high covers of epiphytic algae and two sites more similar to controls. Epiphyte patterns clearly matched in situ measures of nutrient availability, and were consistent with decreased shoot densities in discharge sites. In contrast, differences in epiphyte assemblages between seagrass species were minor, and mostly a result of higher epiphytic loads on C. nodosa than on Z. noltii , which features thinner leaves. Further research is needed to investigate the consequences of these plant and epiphyte alterations in important ecosystem processes such as decomposition and export rates, as well as overall effects of nutrients and salinity in secondary producers such as associated macroinvertebrate assemblages supporting locally important marine fisheries. [ABSTRACT FROM AUTHOR]

Interactions between the palatability and abundance of different food sources may influence herbivory patterns in seagrass-dominated communities. In addition, intra-specific differences in nutrient and structural quality of leaves may also alter seagrass palatability and generate different rates of consumption within these communities. We offered two temperate seagrasses species, ( Cymodocea nodosa and Zostera noltei ) from two different locations to look at intraspecific differences, and two other macrophytes, both of which occur at the same location as seagrasses but represent the extremes of palatability, to a generalist herbivore Paracentrotus lividus (purple sea urchin). Using feeding assays, we compared the consumption rates in individual (single plant species) and combined diets at different food availabilities. Intra-specific differences between seagrass species growing at different locations (inner and outer bay) were indeed found to significantly modify the consumption rate for one species. Structural traits such as carbon content were linked to the low consumption found in Cymodocea nodosa from the inner bay location. In addition, we found that the co-occurrence of different macrophyte species can result in preferential consumption of the more palatable macrophyte with high nutritional content and low structural defence over seagrasses, especially when P. lividus has an abundant food supply. Overall, our findings suggest that intra- and inter-specific differences in seagrass traits and the relative abundance of other macrophytes may explain the variability in patterns of herbivory found within seagrass communities. [ABSTRACT FROM AUTHOR]

The paper concerns the numerical simulation of the wind influence on bottom shear stress and salinity fields in a semi-enclosed coastal lagoon (Etang de Berre) which is connected to the Mediterranean through a long and narrow channel (called Caronte). Two different scenarios are considered. The first scenario (scen.#1), starting with a homogeneous salinity of S = 20 PSU and without wind forcing, studies a stratification process under the influence of a periodic seawater inflow and a strong freshwater inflow from a hydropower plant (250 m 3 /s). Then, in the second scenario (scen.#2), we study how a strong wind of 80 km/h can destroy the haline stratification obtained at the end of scen.#1. The MARS3D numerical model is used to analyze the 3D current and salinity distribution induced by these three meteorological, oceanic and anthropogenic forcings in this lagoon and in the Caronte channel. The main goal is to determine the bottom shear stress (BSS) in the nearshore areas of Zostera noltei replanting, and to compare it with the threshold for erosion of the bottom sediments for different bottom roughness parameters. The most interesting results concern the four nearshore replanting areas; two are situated on the eastern side of EB and two on the western side. The results of scen.#2 show that all these areas are subject to a downwind coastal jet. The destratification process is very beneficial; salinity always remains greater than 12 PSU for a N-NW wind of 80 km/h and a hydropower runoff of 250 m 3 /s. Concerning BSS, it presents a maximum near the shoreline and decreases along transects perpendicular to the shoreline. There exists a zone, parallel to the shoreline, where BSS presents a minimum (where BSS = 0). When comparing the BSS value at the four control points with the critical value, BSS cr , at which the sediment mobility would occur, we see that for the smaller bottom roughness values (ranging from z 0 = 3.5 × 10 −4 mm, to 3.5 × 10 −2 mm) BSS largely surpasses this critical value. For a N-NW wind speed of 40 km/h (which is blowing for around 100 days per year), BSS still largely surpasses BSS cr - at least for the silt sediments (ranging from z 0 = 3.5 × 10 −4 mm, to 3.5 × 10 −3 mm). This confirms the possibility that the coastal jet could be a stressor for SAV replanting. [ABSTRACT FROM AUTHOR]

The objective of this work was to ascertain the nature of the components responsible for the reducing and stabilizing properties of Zostera noltii extracts that lead to gold nanoparticle formation using chemical techniques of analysis. In order to achieve this aim, we try the synthesis of AuNPs with three different extracts from plants collected in the Bay of Cádiz (Spain). The n -butanol extract produced the best results. Taking this into account, four fractions were isolated by Sephadex LH-20 column chromatography from this extract and we studied their activity. The chemical study of these fractions led to the isolation of several flavone sulfates and these were identified as the species' responsible for the formation and stabilization of the AuNPs. Flavone sulfates were purified by high performance liquid chromatography and the structures were established by means of spectroscopic methods nuclear magnetic resonance and mass spectroscopy. AuNPs have an average lifetime of about 16 weeks. Additionally, the morphology and crystalline phase of the gold nanoparticles were characterized by transmission electron microscopy. The composition of the nanoparticles was evaluated by electron diffraction and energy dispersive X-ray spectroscopy. An 88% of the gold nanoparticles has a diameter in the range 20–35 nm, with an average size of 26 ± 2 nm. [ABSTRACT FROM AUTHOR]

Seagrass meadows form highly productive and valuable ecosystems in the marine environment. Throughout the year, seagrass meadows are exposed to abiotic and biotic variations linked to (i) seasonal fluctuations, (ii) short-term stress events such as, e.g., local nutrient enrichment, and (iii) small-scale disturbances such as, e.g., biomass removal by grazing. We hypothesized that short-term stress events and smallscale disturbances may affect seagrass chance for survival in temperate latitudes. To test this hypothesis we focused on seagrass carbon reserves in the form of starch stored seasonally in rhizomes, as these have been defined as a good indicator for winter survival. Twelve Zostera noltei meadows were monitored along a latitudinal gradient in Western Europe to firstly assess the seasonal change of their rhizomal starch content. Secondly, we tested the effects of nutrient enrichment and/or biomass removal on the corresponding starch content by using a short-term manipulative field experiment at a single latitude in the Netherlands. At the end of the growing season, we observed a weak but significant linear increase of starch content along the latitudinal gradient from south to north. This agrees with the contention that such reserves are essential for regrowth after winter, which is more severe in the north. In addition, we also observed a weak but significant positive relationship between starch content at the beginning of the growing season and past winter temperatures. This implies a lower regrowth potential after severe winters, due to diminished starch content at the beginning of the growing season. Short-term stress and disturbances may intensify these patterns, because our manipulative experiments show that when nutrient enrichment and biomass loss co-occurred at the end of the growing season, Z. noltei starch content declined. In temperate zones, the capacity of seagrasses to accumulate carbon reserves is expected to determine carbon-based regrowth after winter. Therefore, processes affecting those reserves might affect seagrass resilience. With increasing human pressure on coastal systems, short- and small-scale stress events are expected to become more frequent, threatening the resilience of seagrass ecosystems, particularly at higher latitudes, where populations tend to have an annual cycle highly dependent on their storage capacity. [ABSTRACT FROM AUTHOR]

In coastal locations seagrass beds are exposed to various hydrodynamic forces that can include waves and/or unidirectional currents. Differences in these forces may be expected to alter nutrient (such as phosphorus and nitrogen compounds e.g., ammonium) uptake rates by seagrass leaves. We investigated in a laboratory flume how high and low velocities with the absence or presence of waves control ammonium absorption. Our results showed that low currents with waves had the highest nutrient uptake compared to all other treatments. This result was ascribed to a combination of mechanisms. The waves may have influenced turbulence and thereby the water movement around the leaf surface, whilst the low current enabled the canopy to remain upright with an open structure, thereby allowing leaves to be exposed to a greater exchange of ammonium rich water. Although, higher currents with waves might have increased turbulence, bending under the high current squeezed the canopy into a compact closed structure. This study indicates that there are broader implications of the observed mechanisms of nutrient uptake, for instance how they depend on the plant morphology such as the leaf area, length and flexibility.

The flavonoid content in leaves of Zostera marina and the endangered Zostera noltii, including mono- and disulphated flavonoids, from different sample localities were characterized. Seasonal variation of both individual and total flavonoid, as well as rosmarinic acid concentration were revealed. Minor amounts of luteolin 7-(6″-malonyl)glucoside ( 6 ) and apigenin7-(6″-malonyl)glucoside ( 11 ) were identified in Z. noltii for the first time. The total flavonoid content was found to be higher in Z. noltii than in Z. marina at most of the examined localities, and the qualitative flavonoid content was somewhat different in the two species. The quantitative variation of flavonoids and rosmarinic acid was found to be relatively consistent from year to year in Z. marina during a period of three years. The two species appeared though to have a different flavonoid production in the various seasons at the West coast. While Z. marina had the highest content in young leaves in May or June, with a markedly decrease from June to September and the lowest measured content in February, Z. noltii had the lowest measured flavonoid content in May/June followed by an increase from June to September and the highest measured content during wintertime in February. The observed seasonal differences may be related to the fact that Z. noltii is considered a perennial, thermophilous species, and the increasing flavonoid production during the colder seasons from September to March/April in Norway may serve as a protective function. [ABSTRACT FROM AUTHOR]

Long-term studies are necessary to establish trends and to understand seagrasses' spatial and temporal dynamic. Nevertheless, this type of research is scarce, as the required databases are often unavailable. The objectives of this study are to create a method for mapping the seagrass Zostera noltei using remote sensing techniques, and to apply it to the characterization of the meadows' extension trend and the potential drivers of change. A time series was created using a novel method based on remote sensing techniques that proved to be adequate for mapping the seagrass in the emerged intertidal. The meadows seem to have a decreasing trend between 1984 and the early 2000s, followed by an increasing tendency that represents a recovery in the extension area of the species. This 30-year analysis demonstrated the Z. noltei' s recovery in the study site, similar to that in other estuaries nearby and contrary to the worldwide decreasing behavior of seagrasses. [ABSTRACT FROM AUTHOR]

The paper concerns the wind influence on bottom shear stress and salinity levels in a Mediterranean semi-enclosed coastal lagoon (Etang de Berre), with respect to a replanting program of Zostera noltii . The MARS3D numerical model is used to analyze the 3D current, salinity and temperature distribution induced by three meteorological, oceanic and anthropogenic forcings in this lagoon. The numerical model has been carefully validated by comparison with daily observations of the vertical salinity and temperature profiles at three mooring stations, for one year. Then, two modelling scenarios are considered. The first scenario (scen.#1), starting with a homogeneous salinity of S = 20 PSU and without wind forcing, studies a stratification process under the influence of a periodic seawater inflow and a strong freshwater inflow from a hydropower plant (250 m 3 /s). Then, in the second scenario (scen.#2), we study how a strong wind of 80 km/h can mix the haline stratification obtained at the end of scen.#1. The most interesting results concern four nearshore replanting areas; two are situated on the eastern side of EB and two on the western side. The results of scen.#2 show that all these areas are subject to a downwind coastal jet. Concerning bottom salinity, the destratification process is very beneficial; it always remains greater than 12 PSU for a N-NW wind of 80 km/h and an hydropower runoff of 250 m 3 /s. Special attention is devoted to the bottom shear stress (BSS) for different values of the bottom roughness parameter (for gravels, sands and silts), and to the bottom salinity. Concerning BSS, it presents a maximum near the shoreline and decreases along transects perpendicular to the shoreline. There exists a zone, parallel to the shoreline, where BSS presents a minimum (close to zero). When comparing the BSS value at the four replanting areas with the critical value, BSS cr , at which the sediment mobility would occur, we see that for the smaller roughness values (ranging from z 0 = 3.5 × 10 −4 mm, to 3.5 × 10 −2 mm) BSS largely surpasses this critical value. For a N-NW wind speed of 40 km/h (which is blowing for around 100 days per year), BSS still largely surpasses BSS cr - at least for the silt sediments (ranging from z 0 = 3.5 × 10 −4 mm, to 3.5 × 10 −3 mm). This confirms the possibility that the coastal jet could generate sediment mobility which could have a negative impact for SAV replanting. [ABSTRACT FROM AUTHOR]

The variability of the flavonoid content of two populations of Z. noltii from different geographical zones, i.e., the Bay of Arcachon and the Bay of Cadiz, was evaluated. Samples were collected in spring and autumn at the two sites, and extracts were prepared by maceration in water. The phenolic content was fully characterized using Nuclear Magnetic Resonance (NMR), UV and Liquid Chromatography-Mass Spectrometry (LC-MS), and the concentration of the individual phenolic was determined by quantitative High-Performance Liquid Chromatography with Diode-Array Detection (HPLC-DAD). The two populations show a strong geographical differentiation in their flavonoid content. The samples from Cadiz were dominated by apigenin 7-sulfate, which represents 71% (autumn collection) and 83% (spring collection) of the total flavonoids, whereas the samples from Arcachon were characterized by diosmetin 7-sulfate (85 and 93% of the total flavonoids). Structural elucidation of the individual phenolics was assigned using the complementary information from their spectral evidence. In addition, the results were confirmed by acid hydrolysis of the flavonoid sulfates, and comparison to synthetic standards obtained by sulfation of apigenin, diosmetin and luteolin. The results represent the first experimental evidence of the existence of chemotypes within the species Z. noltii.

[Display omitted] • Macrozoobenthos data can be used to improve seagrass habitat suitability models. • In the Wadden Sea, seagrass presence was reliably predicted with only four variables. • Seagrass presence was negatively affected by higher Chl-a and ragworm biomass. • Higher bivalve and mudsnail biomass increased the odds for seagrass presence. Seagrass meadows form the foundation of many coastal ecosystems, but are rapidly declining on a global scale. To conserve and restore these key-ecosystems, improved understanding of drivers behind seagrass presence and recovery is needed. Many animals are known to both facilitate and inhibit seagrasses, but biotic factors are still rarely used as indicators of seagrass presence. Hence, we investigate if macrozoobenthos could be used as an indicator for intertidal seagrass (Zostera marina and Zostera noltii) habitat suitability in the international Wadden Sea. Additionally, we explore if macrozoobenthos can explain the differing seagrass recovery rates that have been observed between the Northern (Denmark and Schleswig Holstein) and Southern (Lower Saxony and Netherlands) regions of the Wadden Sea. To achieve this, we performed a Wadden Sea-wide survey at 36 intertidal locations, across three countries, and investigated the importance of 21 abiotic and biotic variables in explaining the presence and absence of intertidal seagrasses. Seagrass presence or absence could be reliably predicted (prediction error: 16.7%) with a multivariate logistic regression with only four variables; chlorophyll a , bivalve, ragworm and mudsnail biomass. We also found higher chlorophyll concentrations and ragworm biomass in the South compared to the Northern Wadden Sea, suggesting that eutrophication and associated community shifts might still inhibit seagrass recovery in the South. Our findings highlight the potential of using macrozoobenthos as indicators for seagrass habitat suitability. In areas, like the Dutch Wadden Sea, where macrozoobenthic surveys are common and where benthic data is readily available, our findings can be used to improve the understanding of seagrass recovery dynamics and the selection of suitable seagrass restoration sites. [ABSTRACT FROM AUTHOR]

Zarranz Elso, M.; Manent, P.; Luque, A.; Ramdani, M., and Robaina, R.R., 2017. Genetic description and remote sensing techniques as management tools for Zostera noltii seagrass populations along the Atlantic Moroccan coast. Seagrass meadows provide an essential ecological service in coastal ecosystems worldwide, although they are sensitive to many human factors, as a serious global regression has been documented. During sampling along the Atlantic Moroccan coast, five coastal lagoons were found characterized by the presence of intertidal monospecific seagrass Zostera noltii meadows (from south to north, Nayla, Oualidia, Sidi Moussa, Moulay Bousselham, and Larache). Two descriptive methods used to characterize Z. noltii populations could be used as management tools for future monitoring implementations: (1) the estimation of surface area covered by Z. noltii meadows using remote sensing techniques and in situ field surveys, and (2) the genetic characterisation of Z. noltii populations using simple sequence repeats (microsatellites) as molecular markers. Results revealed that the Nayla lagoon showed the largest area covered by Z. noltii (269,868 m2) and the highest coverage rate (5.19%), while presenting the lowest genetic/genotypic diversity values ( T = 36, Â = 3.58, G = 50; R = 0.544; He = 0.43). On the other hand, northern populations displayed lower rates of seagrass coverage (∼1%) and higher values of genetic/genotypic diversity. Further genetic characterization also revealed that Z. noltii populations seem to be highly isolated in three geographically independent regions: northern Morocco (R1, Larache and Moulay Bousselham), central Morocco (R2, Oualidia and Sidi Moussa), and southern Morocco (R3, Nayla), which should be considered independent management units. Both seagrass coverage rate and the genetic description of seagrass populations along the Atlantic Moroccan coast seem to be useful management tools that could be used to evaluate changes in seagrass meadows over time to further establish appropriate conservation strategies. [ABSTRACT FROM AUTHOR]

After the dramatic eutrophication-induced decline of intertidal seagrasses in the 1970s, the Wadden Sea has shown diverging developments. In the northern Wadden Sea, seagrass beds have expanded and become denser, while in the southern Wadden Sea, only small beds with low shoot densities are found. A lack of documentation of historical distributions hampers conservation management. Yet, the recovery in the northern Wadden Sea provides opportunity to construct robust habitat suitability models to support management., We tuned habitat distribution models based on 17 years of seagrass surveys in the northern Wadden Sea and high-resolution hydrodynamics and geomorphology for the entire Wadden Sea using five machine learning approaches. To obtain geographically transferable models, hyperparameters were tuned on the basis of prediction accuracy assessed by non-random, spatial cross-validation. The spatial cross-validation methodology was combined with a consensus modelling approach., The predicted suitability scores correlated amongst each other and with the hold-out observations in the training area indicating that the models converged and were transferable across space. Prediction accuracy was improved by averaging the predictions of the best models., We graphically examined the relationship between the consensus suitability score and independent presence-only data from outside the training area using the area-adjusted seagrass frequency per suitability class (continuous Boyce index). The Boyce index was positively correlated with the suitability score indicating the adequacy of the prediction methodology., We used the plot of the continuous Boyce index against habitat suitability score to demarcate three habitat classes - unsuitable, marginal and suitable - for the entire international Wadden Sea. This information is valuable for habitat conservation and restoration management., Divergence between predicted suitability and actual distributions from the recent past indicates that unaccounted factors limit seagrass development in the southern Wadden Sea., Synthesis and applications. Our methodology and data enabled us to produce a robust and validated consensus habitat suitability model. We identified highly suitable areas where intertidal seagrass meadows may establish and persist. Our work provides scientific underpinning for effective conservation planning in a dynamic landscape and sets monitoring priorities. [ABSTRACT FROM AUTHOR]

We conducted a study that shows that light and dark conditions do not affect the uptake rates of ammonium and nitrate by the seagrass Zostera noltei. This is an important advantage over some seaweed species in which these rates are severely reduced at night. In the light, the ammonium uptake rates were initially higher (15 and 20 μmol·g−1·h−1) and stabilized at a rate of 5 μmol·g−1·h−1 after 1 h, whereas in the dark the rates remained constant at a rate of 10 μmol·g−1·h−1 over the first 180 min of incubation. The rates of nitrate uptake in the light were high within the first 120 min of incubation (7.2-11.1 μmol·g−1·h−1) and decreased afterwards to lower values (0.8-3.9 μmol·g−1·h−1), whereas in the dark the rates fluctuated around 0.0-11.1 μmol·g−1·h−1 throughout the whole incubation time (7 h). The soluble sugar content of Z. noltei leaves increased significantly with both ammonium and nitrate incubations in the light, indicating the metabolic outcome of photosynthesis. In the dark, there was no significant variation in either the soluble sugar or in the starch content of leaves, rhizomes or roots in either the ammonium or nitrate incubations. However, the total starch content of plants decreased at night whereas the total soluble sugars increased, suggesting a process of starch catabolism to generate energy with the consequent production of smaller monosaccharide products. The starch content of rhizomes decreased significantly during the light incubations with nitrate but not with ammonium. These results suggest that carbohydrate mobilization is necessary for Z. noltei to account for extra energetic costs needed for the uptake and assimilation of nitrate. Furthermore, our results suggest that nitrate uptake, at least during the day, requires the mobilization of starch whereas the uptake of ammonium does not. [ABSTRACT FROM AUTHOR]

The present study investigates the influence of seagrass root systems on benthic hard-shelled meiofauna (foraminifera). In February and July 2011, sediment cores were collected at low tide at two sites in Arcachon lagoon, a vegetated site with Zostera noltei and a second site with bare sediments. We used the highly discriminative CellTracker™ Green fluorogenic probe technique to recognize living foraminifera and to describe foraminiferal density and diversity. Three dominant species of foraminifera were observed: Ammonia tepida , Haynesina germanica and Eggerella scabra . The two calcareous species, A. tepida and H. germanica, were preferentially found in the upper half to 1 cm of the sediment. At the vegetated site, these two species had a slightly deeper microhabitat. In the literature, both species have been described alive in much deeper sediment layers, possibly due to false positives from the Rose Bengal staining method. These two species also showed 1) higher densities at the site with Z. noltei , 2) a higher density in February when conditions were supposed optimal due to a microphytobenthos bloom, and 3) dissolved calcitic shells in July, probably resulting from a lower pH. The agglutinated species E. scabra was present alive down to at least 7 cm depth. E. scabra showed high densities in the anoxic part of the sediment at both the vegetated and bare sites, with a substantially higher density in summer at the site with bare sediments. Its presence at depth may be related to its trophic requirements; this species could be less dependent on labile organic matter than A. tepida and H. germanica . On this intertidal mudflat, the foraminiferal contribution to aerobic carbon remineralization, based on respiration rate measurements, can account for up to 7% of the diffusive oxygen uptake, almost five times more than the maximum contribution recorded in open marine environments (300 m depth) in the Bay of Biscay. [ABSTRACT FROM AUTHOR]