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Seagrass meadows are well-known for their capacity to capture and store blue carbon in sediments. However carbon stocks vary significantly between meadows, spanning more than three orders of magnitude on both local and global scales. Understanding the drivers of seagrass carbon stocks could help improve strategies for incorporating blue carbon into management plans. Here, we measured sediment carbon stocks in eelgrass (Zostera marina) meadows and unvegetated areas along the Norwegian coast, spanning wide gradients in temperature, wave exposure, water depth, salinity, and eelgrass biomass. Carbon stocks were generally higher in eelgrass meadows than in adjacent unvegetated areas, yet they displayed considerable variation (400 − 30 000 g C m−2 at 50 cm sediment depth) even among nearby sites. Overall, the highest carbon stocks were found in deeper, muddier, sheltered meadows near river mouths. These sites likely have the highest input and retention of carbon from different sources. Consequently, they should be prioritized as conservation targets for preserving coastal blue carbon stocks. Despite ever-increasing efforts to quantify seagrass blue carbon globally, high uncertainties still persist, partly due to differing methodologies, processes, and environmental context. Blue carbon stock estimates could be improved through the coordination of standardised mapping and sampling methods. [ABSTRACT FROM AUTHOR]

Enhalus acoroides (L.f.) Royle is a large and important foundation seagrass species in the tropical Indo-Pacific. The northern marginal populations in China have been declining over the last decades. The reproductive phenology and fruit set of this dioecious seagrass were investigated from June 2017 to February 2018 in two areas in Li'an lagoon, Hainan Island, China. We found that E. acoroides flowered year-round. However, the flowering intensity varied among seasons and was highest in the summer and lowest in the winter. The shoot sex ratio was male-biased, and the pollen-ovule ratio was approximately 104: 1, based on the sex ratio and the number of male florets per inflorescence. Female and male plants flowered at the same time in this population. Despite the high reproductive investment in terms of flower formation observed throughout the year, the abundance of the mature fruits was low, possibly due to physical disturbance and cover by epiphyte and algae. This study provides insight into the reproductive ecology of E. acoroides, which will be useful for the future conservation of this threatened seagrass. [ABSTRACT FROM AUTHOR]

Microplastics are fast-emerging as another potential threat to already globally declining seagrass ecosystems, but there is a paucity of in situ surveys showing their accumulations. Here, we surveyed multiple Zostera marina L. meadows in 2020 and 2021 across Massachusetts, USA, for microplastic contamination, as well as identified factors related to patterns of accumulation. We found that microplastics were ubiquitous throughout all sites regardless of proximity to human development, with fibers being the most common microplastic type. In addition, we showed that accumulation of microplastics within seagrass meadows was related to epiphytic cover on leaves, plant morphology, and bulk-density in sediments. The results of this study provide the first in situ baseline microplastic concentrations on Z. marina plants and sediments for the temperate western North Atlantic. Additionally, we identify specific biotic and abiotic factors related to patterns of microplastic accumulation in these ecosystems. [ABSTRACT FROM AUTHOR]

Seagrass meadows play pivotal roles in coastal biochemical cycles, with nitrogen fixation being a well-established process associated with living seagrass. Here, we tested the hypothesis that nitrogen fixation is also associated with seagrass debris in Danish coastal waters. We conducted a 52-day in situ experiment to investigate nitrogen fixation (proxied by acetylene reduction) and dynamics of the microbial community (16S rRNA gene amplicon sequencing) and the nitrogen fixing community (nifH DNA/RNA amplicon sequencing) associated with decomposing Zostera marina leaves. The leaves harboured distinct microbial communities, including distinct nitrogen fixers, relative to the surrounding seawater and sediment throughout the experiment. Nitrogen fixation rates were measurable on most days, but highest on days 3 (dark, 334.8 nmol N g−1 dw h−1) and 15 (light, 194.6 nmol N g−1 dw h−1). Nitrogen fixation rates were not correlated with the concentration of inorganic nutrients in the surrounding seawater or with carbon:nitrogen ratios in the leaves. The composition of nitrogen fixers shifted from cyanobacterial Sphaerospermopsis to heterotrophic genera like Desulfopila over the decomposition period. On the days with highest fixation, nifH RNA gene transcripts were mainly accounted for by cyanobacteria, in particular by Sphaerospermopsis and an unknown taxon (order Nostocales), alongside Proteobacteria. Our study shows that seagrass debris in temperate coastal waters harbours substantial nitrogen fixation carried out by cyanobacteria and heterotrophic bacteria that are distinct relative to the surrounding seawater and sediments. This suggests that seagrass debris constitutes a selective environment where degradation is affected by the import of nitrogen via nitrogen fixation. [ABSTRACT FROM AUTHOR]

The fish species diversity, fish density, and distribution in the nearshore beds of Zostera marina and Ulva fenestrata have been assessed by SCUBA visual counts in May–September and November 2021. In total, 23 fish species have been registered. The fish species richness increases from 8–13 species in May to a maximum of 17–19 species at the end of June. Then it slightly decreases in July–September and reaches its lowest values in November (2–5 species). The same changes have been noted for the fish density. Fish diversity in the Zostera beds is higher than in the Ulva ones. The similarity of the fish species composition between Zostera and Ulva is low (the Sørensen-Czekanowski index varied from 0.32 to 0.44). In general, fish density is low (from 2.4 to 112.4 ind./50 m2 in Ulva (in November) and Zostera (in July) beds, respectively), although with an exception for Opisthocentrus spp. and Gymnogobius heptacanthus juveniles. An abnormal high bottom water temperature (above 26°C) in late July–early August has led to temporal avoidance of shallow water with plant beds by fishes (except for Gymnogobius heptacanthus) and their shift to a depth of 3.5–4.5 m, where the temperature was lower by 4.0–5.7°С. [ABSTRACT FROM AUTHOR]

Background: Melon fruit fly, Zeugodacus cucurbitae Coquillett (Diptera: Tephritidae), is a devastating polyphagous pest attacking large number of fruits and vegetables causing huge economic yield losses across the world. Management of this notorious pest is very challenging as the larvae feed inside the fruit. Hence, the present research study aimed to screen the indigenous Bacillus thuringiensis Berliner (Bacillales: Bacillaceae) strains causing toxicity to larvae and to identify the insecticidal toxicity-related genes present in respective strains. In the present study, 50 indigenous B. thuringiensis (Bt) strains along with one reference strain were screened against second-instar larvae Z. cucurbitae. All the strains were analyzed for presence of 21 dipteran active cry genes. Results: Mortality in Z. cucurbitae larvae due to Bt strains ranged from 16 to 92%. PCR results revealed that each strain tested positive for a minimum of three cry genes to maximum of nine cry genes. Among the cry genes, cry1A, cry2A, cry1C, cry19, cry11 and cry70 were detected in high frequency of 100, 88, 84, 74, 58 and 54%, respectively. Bioassay studies revealed that ten out of fifty strains displayed more than 50% mortality. Hence, these ten strains, along with the reference strain, were further tested for mortality for the calculation of the median lethal concentration (LC50). The LC50 values ranged between 38.48 and 105.18 μg/ml. The lowest LC50 found for the strain NBAIR Bt107 was 38.48 μg/ml and was on par with the reference strain (Bti 4Q1) (31.3 μg/ml). Conclusion: Indigenous Bt strains displayed a toxicity against the larvae of Z. cucurbitae. The probable dipteran active cry genes responsible for toxicity were interpreted. Thus, the Cry toxins from Bt can play a very important role in the management of Z. cucurbitae. [ABSTRACT FROM AUTHOR]

Phragmites australis is a common helophyte, covering much of the sheltered and shallow soft bottoms along the coasts of the Baltic Sea. Despite the expansion of P. australis over the past decades, there is little information on aquatic macroinvertebrates within P. australis beds. In this study, we examined the effect of large-scale (wave exposure, nutrients) and small-scale (distance from the seaward edge, live and dead stalk density, epiphyte and rhizome biomass) drivers on the density, taxa richness, diversity, and community structure of epifauna and infauna in monospecific P. australis beds around the Åland Islands and the Archipelago Sea. We found that higher wave exposure and nutrient levels generally supported higher epi- and infauna abundance and taxa richness. The effects on Shannon–Wiener diversity were less evident apart from an increase of the infauna diversity in the Archipelago Sea with increasing nutrient levels. On a local scale, the distance from the seaward edge, live and dead stalk density, and epiphyte biomass had varying effects on both epi- and infauna communities in the different regions. Rhizome biomass had no effect on either the epi- or infauna abundance, taxa richness, or diversity. Furthermore, according to existing studies, other habitats, e.g., Zostera marina meadows, Fucus vesiculosus belts, and vegetated soft-bottomed shallow bays, are generally characterized by more abundant fauna, except for the infauna, which had a higher density in P. australis beds than in vegetated soft-bottomed shallow bays. P. australis are a widespread, expanding, and understudied habitat with an important role in supporting coastal biodiversity. [ABSTRACT FROM AUTHOR]

Seagrass meadows are known as hot spots for carbon accumulation, but there is limited field data on the variability of sediment accumulation across time and space. We developed a method to assess spatial and temporal heterogeneity in net sediment accumulation in seagrass meadows using small, inexpensive samplers, allowing for over 200 unique measurements across multiple transects within our study site. Using this method, we assessed sediment accumulation across seagrass meadow edges, and in varying weather conditions. We found the greatest accumulation of sediment 5 m outside of seagrass meadow edges, with sediment accumulation rates averaging just under 100 g m−2 day−1, though rates were highly variable. Carbon accumulation from settled sediment was generally greater outside of seagrass meadow edges than within the bed, especially at sites undergoing recent expansion. Measurements made during tropical storms showed both scouring of sediment away from sites, and increased accumulation, depending on site properties as well as individual tropical storm characteristics. In the storm that had a measurable storm surge, scouring of sediment was a more dominant mechanism, whereas deposition dominated in the storm that had high winds but no associated storm surge. Our data demonstrate the necessity of including measurements that characterize both spatial and meteorological variability to develop a more holistic understanding of the movement of sediment and particulate organic carbon associated with seagrass meadows, especially as meadow area becomes increasingly fragmented with human activity and global change. [ABSTRACT FROM AUTHOR]

Concentrations of heavy metals in live and dead leaves, stems, rhizomes and roots of the seagrass Zostera marina Linnaeus, 1753 are analyzed in the study. On the basis of the concentration, the metals are arranged in the following order: Fe > Mn > Zn > Cu > Pb > Ni >Cd. Differences in Fe, Pb, Ni, and Cd for live and dead leaves are revealed. The factor of sediment enrichment in heavy metals from dead leaves is calculated. The enrichment factor for the studied metals changed in the order Cu > Pb > Zn > Ni > Mn, and the value of solubility product [–log(SP)] for sulfides of the above-listed metals changed in the same order. [ABSTRACT FROM AUTHOR]

Eelgrass (Zostera marina) meadows and boat mooring fields co-occur in nearshore, relatively sheltered embayments. Traditional chain moorings create denuded scars in eelgrass meadows due to repeated and chronic scour of the seafloor by the chain, impacting meadow contiguity and quality. This study assessed the recovery of eelgrass into mooring scars following the conversion of traditional chain moorings to floating rode conservation mooring systems (CMS) in three Massachusetts harbors. The magnitude of eelgrass recovery following the conversion of 21 moorings to floating rode CMS was contingent on the location and positively correlated with the size of the scar associated with the mooring. While most scars started to revegetate following mooring conversion, few experienced complete recoveries and had a persistent denuded halo averaging 2 m in radius around the mooring anchors 5 years post-conversion. We observed CMS gear dragging on the bottom and impacting eelgrass when it was oversized for the depth of the site, and when it was not maintained or cleaned of fouling organisms. Overall, we show that floating rode CMS can be an important tool for eelgrass conservation; however, eelgrass recoveries following mooring conversion to floating rode CMS are variable and incomplete, and challenges pertaining to proper installation and long-term maintenance must be addressed to fully realize this potential. [ABSTRACT FROM AUTHOR]

Geobotanical descriptions of Zostera communities are carried out in the eastern part of the Russian shelf of the Black and Azov seas. Based on the descriptions, the syntaxonomy of the class Zosteretea Pignatti 1953 is considered, taking into account the diversity of macrophytic algae. In total, six communities dominated by Zostera and Nanozostera are identified in the study area; all of them are described for the first time. The results obtained indicate that taking the occurrence of macrophytic algae into account in the floristic classification of communities dominated by Zostera and Nanozostera makes it possible to reliably identify several communities with specific composition, ecology, and location. It has been shown that the oligosaprobic marine sublittoral vegetation of sandy and silty–sandy sediments of the northeastern part of the Black and Azov seas is represented by widespread flowering plants of boreal origin and associated short-cycle species of cosmopolitan and subcosmopolitan macrophytic algae. [ABSTRACT FROM AUTHOR]

Eelgrass beds provide a habitat for many high-value fishery resources, and provisioning services, one of the ecosystem services, need to be quantified. However, few examples have been evaluated spatially. We determined the distribution of eelgrass beds in Lake Notoro, a marine lagoon in Hokkaido, Japan, and quantified the provisioning services by the eelgrass beds in relation to Pandalus latirostris, a fishery resource. Acoustic measurement surveys of the eelgrass beds and catch surveys of the shrimp were conducted in July and August 2015. The relationship between catch per unit effort (CPUE) of shrimp and the distribution of eelgrass beds was shown. The estimated distribution area of eelgrass beds was 7.07 km2. Shrimp was frequently caught at water depths of 3–5 m, approximately 200 m from the edge of the eelgrass beds. The expected catch of shrimp in the fishing area of Lake Notoro in 2015 was 25.37 tons and US$ 463.6 thousand. Eelgrass beds were found to affect the fisheries production not only on the inside but also at the edge and outside. The entire coastal space should be evaluated, while considering the effect of the distribution of eelgrass beds, to quantify the provisioning services. [ABSTRACT FROM AUTHOR]

Marine plastic pollution is a well-recognised and debated issue affecting most marine ecosystems. Despite this, the threat of plastic pollution on seagrasses has not received significant scientific attention compared to other marine species and habitats. The present review aims to summarise the scientific data published in the last decade (January 2012–2023), concerning the evaluation of plastic pollution, of all sizes and types, including bio-based polymers, on several seagrass species worldwide. To achieve this goal, a comprehensive and critical review of 26 scientific papers has been carried out, taking into consideration the investigated areas, the seagrass species and the plant parts considered, the experimental design and the type of polymers analysed, both in field monitoring and in laboratory-controlled experiments. The outcomes of the present review clearly showed that the dynamics and effects of plastic pollution in seagrass are still under-explored. Most data emerged from Europe, with little or no data on plastic pollution in North and South America, Australia, Africa and Antarctica. Most of the studies were devoted to microplastics, with limited studies dedicated to macroplastics and only one to nanoplastics. The methodological approach (in terms of experimental design and polymer physico-chemical characterisation) should be carefully standardised, beside the use of a model species, such as Zostera marina, and further laboratory experiments. All these knowledge gaps must be urgently fulfilled, since valuable and reliable scientific knowledge is necessary to improve seagrass habitat protection measures against the current plastic pollution crisis. [ABSTRACT FROM AUTHOR]

The species composition and the structure of the macrophytobenthos, macrozoobenthos, and bottom sediments of Taman Bay are studied. This inlet is inhabited by seagrass Zosteramarina L. which forms vast underwater meadows here. Samples were collected in 2008–2009, before the ongoing rise of salinity in the Sea of Azov. Three main biotopes with different bottom sediment composition (sands, sands with shells, and silts) were identified. They were inhabited by four main macrobenthic biocenoses (unvegetated near-shore biocenosis, mosaic macrophyte vegetation outside the surf zone, pure eelgrass's meadows belt, and the communities, dominated by the mobile macrozoobenthos species with low abundance of macrophytes occupying the central part of the bay). The main environmental factor associated with this distribution of the vegetation was the silt content (grain size <0.001 mm). The spatial structure of the macrozoobenthos correlated with the projective cover of Z. marina. Possible reasons for the revealed pattern in the distribution of communities are discussed. [ABSTRACT FROM AUTHOR]

As part of a long-term study on the effects of nitrogen (N) loading in a shallow temperate lagoon, we measured rates of N2 fixation associated with seagrass (Zostera marina) epiphytes during the summer from 2005 to 2019, at two sites along a gradient from where high N groundwater enters the system (denoted SH) to a more well-flushed outer harbor (OH). The data presented here are the first such long-term N2 fixation estimates for any seagrass system and one of the very few reported for the phyllosphere in a temperate system. Mean daily N2 fixation was estimated from light and dark measurements using the acetylene reduction assay intercalibrated using both incorporation of 15N2 into biomass and a novel application of the N2:Ar method. Surprisingly, despite a large inorganic N input from a N-contaminated groundwater plume, epiphytic N2 fixation rates were moderately to very high for a seagrass system (OH site 14-year mean of 0.94 mmol N m−2 d−1), with the highest rates (2.6 mmol N m−2 d−1) measured at the more N-loaded eutrophic site (SH) where dissolved inorganic N was higher and soluble reactive phosphorus was lower than in the better-flushed OH. Over 95% of the total N2 fixation measured was in the light, suggesting the importance of cyanobacteria in the epiphyte assemblages. We observed large inter-annual variation both within and across the two study sites (range from 0.1 to 2.6 mmol N fixed m−2 d−1), which we suggest is in part related to climatic variation. We estimate that input from phyllosphere N2 fixation over the study period contributes on average an additional 20% to the total daily N load per area within the seagrass meadow. [ABSTRACT FROM AUTHOR]

Global climate change increases the overall risks for coastal flooding and erosion. Meanwhile, nature-based solutions (NbS) are increasingly becoming a focus of coastal protection measures to improve the climate adaptability. In this study, the present and potential future role of seagrass in coastal risk reduction strategies were explored for the highly energetic Wadden Sea area of the German Bight. The methodology in this study combined seagrass coverage data (Zostera marina and Zostera noltei) obtained by field surveys and what-if scenario simulations using the SCHISM unstructured grid model framework, coupling hydrodynamics, waves, sediments, and a seagrass module. The results suggest that the introduction of seagrass meadows locally can reduce both current velocities and significant wave heights in the order of up to 30 % in the deeper areas and above 90 % in the shallow areas. Reduction in bottom shear stress of a similar relative magnitude significantly reduced sediment mobilisation on the order of 2 g/L in the 95th quantile of bottom layer sediment concentrations. Effectively altering hydromorphodynamic conditions favouring sediment accumulation, seagrass expansion could help tidal flats height growths to keep up with SLR, thus further maintaining the bathymetry-induced tidal dampening and lowering flooding and erosion risks as well the amount of energy at dike infrastructure. The accumulated effect of seagrass under calm weather conditions is considered more important than the increased attenuation in absolute values it provides during extreme conditions. The overall conclusion is that seagrass expansion could be a useful addition to engineered coastal protection measures. [ABSTRACT FROM AUTHOR]

The accumulations of iron in the halophytic species Triglochin maritima L., Plantago maritima L., Aster tripolium L., and Zostera marina L. were studied. Littoral soils are not contaminated with iron (6–16 g/kg). Seawater, on the contrary, contains high concentrations of iron (0.04–0.32 mg/l). Halophytes accumulate iron to very high values (6.49–71.63 g/kg), and 93% of this metal is found in rhizomes. The reasons for this phenomenon are discussed. Halophytes of the littoral zone of the White Sea are involved in the biogeochemical iron cycle as the main fixation sites of iron in the "coast–sea" system. They have phytoremediation potential on coastal territories. [ABSTRACT FROM AUTHOR]

Background: Understanding the mechanisms behind resilience has become more relevant in the last decades, due to the increasing and intensifying disturbances from natural and anthropogenic sources that threaten biodiversity. Evidence from terrestrial populations suggests that resilience increases with genetic diversity. Few studies, however, have evaluated the relationship between genetics and resilience in benthic marine populations. Methods and results: For this review, we gathered studies where genetic diversity was the predictor variable, and resilience was the response variable. Twenty-five publications between 2001 and 2018 were included. Thirteen benthic marine species were identified, mainly sea-grass species, among which Zostera marina was the most frequently studied. The relationship between genetic diversity and resilience was variable-dependent. Considering all the analyses (N = 150) in the studies reviewed, 44% reported positive relationships between genetic diversity and resilience capacity. Negative relationships were found in 6%, and no relationship was found in 50%. Positive relationships indicated that genetic diversity increased resistance and recovery capacity after different types of disturbances. Dominance and complementarity were suggested as the underlying mechanism explaining these findings in the few studies that conducted this type of evaluation. Conclusions: The results of this review suggest that the relationship between genetic diversity and resilience is mainly positive. However, this relationship relies on how genetic diversity and resiliency were measured, as well as on the biological characteristics of the species under study. This reinforces the importance of acknowledging and maintaining genetic diversity for the conservation of benthic populations in marine ecosystems. [ABSTRACT FROM AUTHOR]

A noticeable feature of labile heavy metals is that they are highly prone to be to bioaccumulated and bioassimilated in natural environments. When in high concentrations, these metals are toxic to living organisms, as is particularly evident in the coastal shallow marine zones, which are most strongly affected by anthropogenic processes. This paper presents data on the contents of heavy metals, concentrations of organic carbon, and the granulometric composition of bottom-sediment cores in three shallow bights of the Peter the Great Bay, in two of which (Voevoda and Novgorodskaya bights), large bottom areas are overgrown with seagrass Zostera marina L. (sea zostera, ZM). Data on the vertical distribution of heavy metals and organic carbon in the cores showed that the highest concentrations of Zn and Cu (up to 204 and 91 mg/kg, respectively) occur in samples from Voevoda bight, and the highest concentrations of Mn and Pb (up to 344 and 45 mg/kg, respectively) were found in Novgorodskaya bight, where meadows of the seagrass grow. The highest Cr, Ni, and Co contents (up to 69, 31, and 13 mg/kg, respectively) were identified in Uglovoy bight, where sea grass is practically absent. [ABSTRACT FROM AUTHOR]

Dissolved carbon dioxide (CO2) in seawater lowers water pH and can disrupt microbial nutrient cycles. It is unclear how acidification impacts hot spots of nutrient cycling in marine ecosystems such as eelgrass (Zostera marina) beds. We measured nutrient and gas fluxes in sediment cores from Z. marina beds and unvegetated-sediment habitats in Shinnecock Bay, New York, USA in a continuous-flow system with acidified and ambient pH treatments. Under ambient conditions, uptake of N2 by nitrogen (N) fixation was greater than production of N2 by denitrification. Denitrification, however, was dominant under acidified conditions. We then enriched flowing seawater with 15NO3− to test the impact of a nutrient pulse with ambient pH or acidified conditions in the eelgrass and unvegetated cores. Sediment N2 efflux was higher in eelgrass than unvegetated sediments under acidified pH with N-enriched treatments. Results suggest that eelgrass beds may serve as sinks rather than sources of N under the combined stressors of acidification and N-loading. Documenting changes to N pathways under acidification can inform efforts to manage marine ecosystems and conserve benthic habitats. [ABSTRACT FROM AUTHOR]

Hypoxic conditions can affect marine resource populations through lethal and non-lethal damage to marine life. The seagrass Zostera marina beds provide high ecosystem services, such as carbon fixation through photosynthesis and fish nursery functions. However, the respiration of seagrass at night is expected to increase in proportion to its biomass per unit area. The hypothesis that decreases in dissolved oxygen (DO) concentration affect fish community was tested in a temperate seagrass bed. The number of species, abundance, and biomass of fish in summer were lower at the site with a higher seagrass shoot density (85 shoots m−2) than that with a lower density (23 shoots m−2). The higher density site showed DO concentrations < 4 mg L−1 every day in summer. Model analysis revealed that tidal level, tidal range, day/night, and the time of day were important factors influencing the variation in the DO concentration and that the degree of influence varied by season and seagrass density. A laboratory experiment demonstrated that the survival of the most dominant fish species in the seagrass bed in summer, the juvenile black rockfish Sebastes cheni, for 10–60 min was reduced as the oxygen concentration decreased from 4 to 2 mg L−1. High seagrass shoot density was suggested to have negative effects on fish communities through a decrease in DO concentration in summer. These results provide evidence that the nursery role, one of the important components of the ecological functions of seagrass beds, does not always increase in proportion to vegetation coverage. [ABSTRACT FROM AUTHOR]

Coastal nutrient pollution, or eutrophication, is commonly linked to anthropogenic influences in terrestrial watersheds, where land-use changes often degrade water quality over time. Due to gradual changes, the management and monitoring of estuarine systems often lag environmental degradation. One example can be found at the Waquoit Bay National Estuarine Research Reserve, where we developed an analysis framework to standardize and analyze long-term trends in water quality and submerged vegetation data from monitoring programs that began in the 1990s. These programs started after the nearly complete loss of historically extensive Zostera marina (eelgrass) meadows throughout the estuary. Recently, eelgrass only persisted in small, undeveloped sub-embayments of the estuary, with conservative declines of over 97% in areal coverage. Over the past 2 decades, the average deoxygenation, acidification, and warming were −24.7 µmol O2 kg−1 (−11%), 0.006 µmol H+ kg−1 (+ 34%), and 1.0 °C (+ 4%), respectively. Along with the loss of eelgrass, there was also a decline in macroalgal biomass over 3 decades, resulting in a system dominated by pelagic metabolism, indicated by a 71% increase in water column chlorophyll a concentrations since 2009. This recent increase in phytoplankton biomass, which is highly mobile and transported throughout the estuary by tides, has resulted in recent degradation of isolated embayments despite their lower nutrient loads. This shift toward pelagic dominance in Waquoit Bay may indicate that other eutrophic and warming estuaries may also shift toward pelagic dominance in the future, as the Northeastern US is one of the fastest warming regions across the world. [ABSTRACT FROM AUTHOR]

Sandy beach invertebrates depend largely upon allochthonous inputs of macrophytes and the oceanographic processes that deliver them as wrack. While part of this wrack is returned to the sea by the tides, a large portion remains, ages, and decomposes on the supralittoral, becoming colonized and used by macrofaunal organisms. This study quantified faunal colonization in relation to change in wrack nutritional quality, measured here as protein content. We prepared, deployed, and followed for 29 days a series of experimental wrack patches of two of the most common species in the wrack of Atlantic Canada sandy beaches: the rockweed Fucus serratus and the eelgrass Zostera marina. On a weekly basis, we measured the density of the macrofauna with a focus on the most abundant species, the talitroid amphipod Americorchestia longicornis, in both types of wrack and in bare sediments, while simultaneously measuring macrophyte protein contents. Our results show that rockweed patches concentrated higher densities of amphipods compared to eelgrass and bare sediments, a result that was matched by protein differences (higher concentrations in rockweed than eelgrass). However, while protein contents gradually declined over time in both macrophytes, the abundance of amphipods increased. Hence, while nutritional quality may explain between-wrack and wrack-bare sediment differences in faunal colonization, it cannot explain the counterintuitive temporal pattern recorded here. The latter result points to the often-ignored role played by the physical characteristics of the wrack and the conditions they create while decomposing over sandy beaches. [ABSTRACT FROM AUTHOR]

Plant microbiomes depend on environmental conditions, stochasticity, host species, and genotype identity. Eelgrass (Zostera marina) is a unique system for plant–microbe interactions as a marine angiosperm growing in a physiologically-challenging environment with anoxic sediment, periodic exposure to air at low tide, and fluctuations in water clarity and flow. We tested the influence of host origin versus environment on eelgrass microbiome composition by transplanting 768 plants among four sites within Bodega Harbor, CA. Over three months following transplantation, we sampled microbial communities monthly on leaves and roots and sequenced the V4–V5 region of the 16S rRNA gene to assess community composition. The main driver of leaf and root microbiome composition was destination site; more modest effects of host origin site did not last longer than one month. Community phylogenetic analyses suggested that environmental filtering structures these communities, but the strength and nature of this filtering varies among sites and over time and roots and leaves show opposing gradients in clustering along a temperature gradient. We demonstrate that local environmental differences create rapid shifts in associated microbial community composition with potential functional implications for rapid host acclimation under shifting environmental conditions. [ABSTRACT FROM AUTHOR]

Temperate lagoonal estuaries contain a mosaic of subtidal habitats including salt marsh creeks, sand, and seagrass. Studies comparing fish use of estuarine habitats have focused disproportionately on sand and seagrass habitats, and along the U.S. east coast, previous studies that have made the direct comparison between subtidal salt marsh creeks, sand, and seagrass habitats were spatially narrow in scope. Here, we performed a comprehensive comparison of fish species composition, abundance, diversity, richness, and fish lengths across subtidal salt marsh creek (upper creek and creek mouth sites), sand, and seagrass habitats within a temperate lagoonal estuary. Daytime otter trawl sampling occurred at 45 sites within Barnegat Bay (New Jersey) in April, June, August, and October during 2012–2014. Seventy species representing estuarine transients, residents, southern strays, and shelf strays were observed, and juvenile and small adult fishes dominated the collections. There were some differences in species composition between habitats, with the assemblages in upper creek and seagrass habitats being the most dissimilar. Fish abundance, diversity, and richness were often higher in creek mouth and seagrass habitats than in sand habitat. Similar to seagrass habitats, creek mouths were shallow, more saline, and contained complex physical structure (macroalgae, marsh banks). Many fishes used all habitats (e.g., bay anchovy Anchoa mitchilli), but others were partial to certain habitats (e.g., fourspine stickleback Apeltes quadracus in seagrass). This study reaffirmed that many interacting factors shape fish assemblages and demonstrated the significance of marsh creeks to the subtidal habitat mosaic of this temperate lagoonal estuary. [ABSTRACT FROM AUTHOR]

Biodiversity is important for communities to be resilient to a changing world, but patterns of diversity fluctuate naturally over time. Understanding these shifts — and the species driving community dynamics — is crucial for informing future ecological research and conservation management plans. We investigated the impacts of seasonality, small-scale changes in seagrass cover, and small-scale spatial location on the epifaunal communities occupying a temperate seagrass bed in the South Island of New Zealand. By sampling epifaunal communities using a fine-mesh push net two to three times per season for 1 year, and using a combination of multivariate and hierarchical diversity analyses, we discovered that season, seagrass cover, and the location within the bay, and their interactions, explained 88.5% of the variation in community composition. Community composition and abundances, but not numbers, of species changed over seasons. The most common taxa were commercially important Caridean shrimp and juvenile flounder (Rhombosolea spp.), and both decreased in abundance in summer (shrimp: 1.40/m2 in winter to 0.80/m2 in summer; flounder: 0.15/m2 in winter to 0.01/m2 in summer). Other commercially important species were captured as juveniles, including blue cod (Parapercis colias), kahawai (Arripis trutta), and whitebait (Galaxias spp.). The only adult fish captured in the study were two pipefish species (Stigmatopora nigra and Leptonotus elevatus), which had distinctly seasonal breeding patterns, with reproductively active adults most likely to be found in the spring and fall. Our study highlights the importance of estimating biodiversity parameters based on sampling throughout the year, as some species will be overlooked. We demonstrate that the temperate estuarine seagrass-affiliated animal communities differ in response to season and fine-scale local environments, causing fluctuations in biodiversity throughout the year. [ABSTRACT FROM AUTHOR]

The ratio of stable carbon and nitrogen isotopes in the suspended particulate matter has been widely used to study processes occurring in the marine ecosystem. At the same time, the signals provided by isotope ratios in coastal ecosystems can be difficult to interpret, due to several, often contradictory processes taking place simultaneously. In this study, we hypothesized that the carbon and nitrogen isotopic variation is predominantly affected by seasonally occurring phytoplankton species succession in the Gulf of Riga, Baltic Sea. Cyclical seasonal patterns were observed for carbon and nitrogen isotopic compositions of both SPM and phytoplankton data. Enrichment of heavy isotopes in the Gulf of Riga took place during spring phytoplankton bloom (from on average between + 7.1 and + 8.8 ‰, and between − 23.7 and − 21.9 ‰ for δ15N and δ13C, respectively) and pooled at significantly lower values (from + 3.1 to + 5.1 ‰ and from − 28.7 to − 25.1 ‰ for δ15N and δ13C, respectively) for the rest of the year. At the same time, the spatial gradient of isotope ratios was sporadic and inconclusive. The results showed that terrestrial and anthropogenic input to particulate matter is negligible from spring to autumn. Multivariate analysis revealed that the observed seasonal variability was indeed driven by variation in phytoplankton species composition. The diatoms, dinoflagellates, and the ciliate Mesodinium rubrum facilitated enrichment of 15N and 13C in spring. In contrast, atmospheric nitrogen fixation by cyanobacteria and the assimilation of their released nutrients by other organisms resulted in lower δ15N values during summer. This variability requires careful considerations for conducting food web studies in temperate coastal and estuarine environments during high phytoplankton biomass periods. [ABSTRACT FROM AUTHOR]

Seagrasses have some of the highest rates of carbon burial on the planet and have therefore been highlighted as ecosystems for nature-based climate change mitigation. However, information is still needed on the net radiative forcing benefit of seagrasses inclusive of their associated greenhouse gas (GHG) emissions. Here, we report simultaneous estimates of seagrass-associated carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) air–water emissions. Applying in situ sampling within a south-east Australian seagrass ecosystem, this study finds atmospheric GHG emissions from waters above seagrasses to range from − 480 ± 15.96 to − 16.2 ± 8.32 mg CO2-equivalents m2 d−1 (net uptake), with large temporal and spatial variability. Using a combination of gas specific mass balance equations, dissolved stable carbon isotope values (δ13C) and in situ time-series data, CO2-e flux is estimated at − 21.74 mg m2 d−1. We find that the net release of CH4 (0.44 µmol m2 h−1) and net uptake of N2O (− 0.06 µmol m2 h−1) effectively negated each other at 16.12 and − 16.13 mg CO2-e m2 d−1, respectively. The results of this study indicate that temperate Australian seagrasses may function as net sinks of atmospheric CO2-e. These results contribute towards filling key emission accounting gaps both in the Australian region, and through the simultaneous measurement of the three key greenhouse gas species. [ABSTRACT FROM AUTHOR]

Sea level rise (SLR) is changing coastal habitats that support valuable ecological and economic resources. A rise in global mean sea level (GMSL) will lead to changes in water depth in coastal bays and estuaries, affecting the distribution of seagrasses, which provide numerous ecosystem services, but are declining globally. In estuaries along the west coast of the USA, seagrasses often co-occur with shellfish aquaculture and some aquaculture practices negatively influence seagrass. Understanding this interaction and future shifts in seagrass distribution has therefore become a concern for both natural resource managers and aquaculturists. In this study, a model is developed to establish relationships between seagrass presence and seven predictor variables (bathymetric elevation, salinity, distance to estuary mouth, distance to nearest channel, cumulative wave stress, sediment composition and burrowing shrimp density) and then used to predict the distribution of eelgrass (Zostera marina) in aquaculture habitats of Willapa Bay, Washington, for the years 2030, 2050 and 2100 under conservative and high rates of SLR. The model predicts Z. marina will increase throughout the intertidal for all SLR scenarios and years, resulting in as much as 34% more eelgrass in Willapa Bay by 2100 and a 40% increase within aquaculture beds. By 2100, Z. marina could increase in as many as 333 of the 458 aquaculture beds examined and the majority of aquaculture beds could experience over 50% Z. marina coverage. Such increases in Z. marina will likely result in future management challenges for aquaculture operations. [ABSTRACT FROM AUTHOR]

At the start of the 21st century, a coastal residential-estate marina was developed on a previously degraded and polluted brownfield island site within Knysna estuarine bay, Garden Route National Park, South Africa, including the creation of 25 ha of new flow-through tidal canals. Canals near the larger entrance to this system now support permanently submerged beds of seagrass, which in turn support abundant macrobenthic invertebrates. In comparison with equivalent seagrass-associated assemblages present in natural channels around the island, those in the artificial marina canals were similarly structured and dominated by the same species, but the marina assemblages were significantly more species-rich (1.4 x on average) and were more abundant. Indeed, this area of marina supports the richest seagrass-associated macrofaunal biodiversity yet recorded from South Africa. The canals created de novo therefore now form a valuable addition to the bay's marine habitat, in marked contrast to the generality that marinas developed on greenfield sites represent a net reduction in intertidal and shallow marine area and associated seagrass-associated benthos. If located and constructed appropriately, brownfield marina development and conservation of coastal marine biodiversity clearly need not be antithetical, and brownfield sites may provide opportunity for the location and management of 'artificial marine micro-reserves' or for the action of 'other effective area-based conservation measures' for soft-sediment faunas. [ABSTRACT FROM AUTHOR]

Content of accumulated carbon (Cdep, which is referred to as blue carbon, BC) was calculated for the uppermost 1-m thicknesses of sediments in bights of the Peter the Great Bay of the Sea of Japan in 2014–2020. In the absence of Zostera Marina (ZM) meadows in Voevoda, Novgorodskaya and Uglovoy bights, BC contents were 140, 99, and 55 tC/ha, respectively. The presence of sea grass significantly increases these values, which were 180 and 126 tC/ha for Voevoda and Novgorodskaya bights, respectively. Using the measured radioactivity of the 137Cs isotope, the rate of BC accumulation in the bights without meadows ZM was estimated at 17, 69, and 98 gC/(m2 year) in Uglovoj, Novgorodskaya, and Voevoda bights, respectively, and at 101 and 144 gC/(m2 year) at sites covered by ZM meadows in Novgorodskaya and Voevoda bights, respectively. Using data of chlorophyll a measurements in sediments of the basins in 2018 through 2020, the bioturbation coefficients (62.7–5.3 cm2/day) and the constants of apparent organic carbon degradation in sediments (0.003–0.068 day–1) were estimated. The maximum BC degradation rates were found in the upper horizons: 550, 39, 6, and 4 gC/(m2 year) at sites with ZM in Voevoda, and without ZM in Voevoda, Novgorodskaya, and Uglovoy bights, respectively. It was found out that ZM meadows cause the maximum concentration of refractory organic carbon ( in sediments of Voevoda bight). [ABSTRACT FROM AUTHOR]

Fluxes of nutrients (ammonium, total nitrogen, dissolved inorganic phosphorus, total phosphorus, silica, and dissolved organic carbon) across the interface between bottom water and sediments were studied in three shallow bights (Voevoda, Novgorodskaya, and Uglovoj) of the Peter the Great Bay in the course of survey in September–October, 2019. At two stations in each of the bights, nutrient concentrations were measured in seawater sampled at 10 cm above the seafloor and in the pore waters of the sediment cores; and organic carbon, fulvic acids, humic acids, and chlorophyll a were analyzed in the solid phase of the sediments. Bioturbation coefficients were estimated from variations in chlorophyll a concentration with depth in the sediment cores. The fluxes of nutrients (ammonium, total nitrogen, phosphorus, total phosphorus, and silicon) and dissolved organic carbon (DOC) were evaluated by model calculations. The estimated nutrients fluxes were, with regard to the bioturbation, about one order of magnitude higher than those estimated by the Fick law. The highest concentrations of organic carbon, 6.5 and 5.5% per dry weight of sediments, were found in the top layer of sediments retrieved at sites covered by Zostera marina L. in the Voevoda and Novgorodskaya bights, respectively. However, the highest fluxes across the water–sediment interface were obtained for a site devoid of seagrass in the Novgorodskaya bight, where the top sediment layer contained 2.8% organic carbon. The annual specific fluxes of nutrients estimated for the water–sediment interface were comparable to or even higher than the annual specific fluxes of nutrients brought per surface area unit of the Amur bay by the Razdolnaya River and domestic waste waters from the city of Vladivostok. [ABSTRACT FROM AUTHOR]

Mosaic, chlorosis, brown spots, or roughness were found on Vigna marina and V. riukiuensis, which are salt-resistant wild relatives of cowpea (V. unguiculata) and adzuki bean (V. angularis), respectively, on Miyako Island, Japan. RNA-sequencing was performed to identify both cucumber mosaic virus (CMV) and bean common mosaic virus (BCMV) in the leaves of both Vigna species. CMV from leaves of V. marina and BCMV from V. riukiuensis systemically infected Vigna plants and caused symptoms on leaves. Thus, these viruses are responsible for the symptoms. This is the first report of CMV and BCMV infecting wild species of Vigna in Japan. [ABSTRACT FROM AUTHOR]

Blue crabs (Callinectes sapidus) are highly mobile, ecologically-important mesopredators that support multimillion-dollar fisheries along the western Atlantic Ocean. Understanding how blue crabs respond to coastal landscape change is integral to conservation and management, but such insights have been limited to a narrow range of habitats and spatial scales. We examined how local-scale to landscape-scale habitat characteristics and bathymetric features (channels and oceanic inlets) affect the relative abundance (catch per unit effort, CPUE) of adult blue crabs across a > 33 km2 seagrass landscape in coastal Virginia, USA. We found that crab CPUE was 1.7 × higher in sparse (versus dense) seagrass, 2.4 × higher at sites farther from (versus nearer to) salt marshes, and unaffected by proximity to oyster reefs. The probability that a trapped crab was female was 5.1 × higher in sparse seagrass and 8 × higher near deep channels. The probability of a female crab being gravid was 2.8 × higher near seagrass meadow edges and 3.3 × higher near deep channels. Moreover, the likelihood of a gravid female having mature eggs was 16 × greater in sparse seagrass and 32 × greater near oceanic inlets. Overall, we discovered that adult blue crab CPUE is influenced by seagrass, salt marsh, and bathymetric features on scales from meters to kilometers, and that habitat associations depend on sex and reproductive stage. Hence, accelerating changes to coastal geomorphology and vegetation will likely alter the abundance and distribution of adult blue crabs, challenging marine spatial planning and ecosystem-based fisheries management. [ABSTRACT FROM AUTHOR]

The Journal of Academic Ethics expresses gratitude to its editorial board members and researchers for their support as reviewers in 2023. The list of reviewers includes a diverse range of individuals from various backgrounds and expertise. Springer Nature, the publisher, maintains a neutral stance on jurisdictional claims and institutional affiliations. [Extracted from the article]

A review of available research into the blue carbon potential of seagrass was undertaken. This was then used to inform an analysis of the potential current, historic, and future value of carbon sequestered and stored in the Essex Estuaries Special Area of Conservation (SAC). The assessed status of Zostera in the SAC highlights the extent of historic loss and continued degradation of this designated sub-feature, and current water quality is incompatible with recovery or restoration. Seagrass blue carbon currently stored within the SAC equates to ∼18,350 t C at a sequestration rate of 117.15 t C yr−1, with a lost/potential of 534,700 t C storage capacity. The calculated financial value of current stocks (£4.6 m) is dwarfed by the lost/potential monetary value of carbon storage, £135 m, and the forfeited sequestration of £860,000-worth of carbon annually from degraded habitat. The use of carbon offset credits could help fund the huge potential for restoration that exists within the SAC. [ABSTRACT FROM AUTHOR]

Biological invasions can pose a severe threat to coastal ecosystems, but are difficult to track due to inaccurate species identifications and cryptic diversity. Here, we clarified the cryptic diversity and introduction history of the marine amphipod Ampithoe valida by sequencing a mtDNA locus from 683 individuals and genotyping 10,295 single-nucleotide polymorphisms (SNPs) for 349 individuals from Japan, North America and Argentina. The species complex consists of three cryptic lineages: two native Pacific and one native Atlantic mitochondrial lineage. It is likely that the complex originated in the North Pacific and dispersed to the north Atlantic via a trans-arctic exchange approximately 3 MYA. Non-native A. valida in Argentina have both Atlantic mitochondrial and nuclear genotypes, strongly indicating an introduction from eastern North America. In two eastern Pacific estuaries, San Francisco Bay and Humboldt Bay, California, genetic data indicate human-mediated hybridization of Atlantic and Pacific sources, and possible adaptive introgression of mitochondrial loci, nuclear loci, or both. The San Francisco Bay hybrid population periodically undergoes population outbreaks and profoundly damages eelgrass Zostera marina thalli via direct consumption, and these ecological impacts have not been documented elsewhere. We speculate that novel combinations of Atlantic and Pacific lineages could play a role in A. valida's unique ecology in San Francisco Bay. Our results reinforce the notion that we can over-estimate the number of non-native invasions when there is cryptic native structure. Moreover, inference of demographic and evolutionary history from mitochondrial loci may be misleading without simultaneous survey of the nuclear genome. [ABSTRACT FROM AUTHOR]

Measured decreases in the spatial extent of seagrasses in Massachusetts are attributed to declining water quality, disease, or direct and indirect impact from dredging or construction. Routine aerial monitoring of seagrasses along the 2400-km coastline is costly and therefore limited both temporally and spatially. Diver surveys are used at two sites for in situ assessments of seagrass meadow structure. In order to examine spatial and temporal trends in seagrass extent and structure, a survey methodology that is less expensive and better at capturing structural characteristics than aerial photography and more efficient than divers is needed. Hydroacoustic methods are relatively inexpensive and rapidly deployed and can measure characteristics including canopy height and percent cover of eelgrass meadows. We tested the capabilities and limitations of a BioSonics DT-X echosounder using the EcoSAV algorithm to measure presence/absence, canopy height, and percent cover of eelgrass. Measurements were found to be reproducible on duplicate transects but had low precision: 36 cm for canopy height and 34% for percent cover. To assess accuracy, we compared EcoSAV estimates of canopy height and percent cover with diver measurements. The EcoSAV estimates of canopy height and percent cover were significantly higher than diver measurements by 60 cm and 46%. We conclude that the BioSonics with EcoSAV processing is an efficient tool to map eelgrass meadows and assess relative change over time, but because of differences in the way the echosounder measurements are made compared with diver measurements, echosounder data should not be used to directly compare with diver data or for surveys that require high accuracy and precision. [ABSTRACT FROM AUTHOR]

Analysis of data on processing samples of macrophytobenthos was used to determine the species richness and composition of Zostera marina and Z. noltei communities in the Taman Bay of the Sea of Azov. The study has shown a weak statistically significant relationship between the degree of dominance of these species and the species richness of communities on an area of 0.25 m2; this relationship can be explained by the "species-energy" theory. If the total biomass of associated species in homogeneous areas was approximately the same, the number of associated species growing in large areas in communities with a high degree of Z. marina and Z. noltei dominance was no less than in small areas with a low degree of Zostera dominance. The similarity (difference) of the species composition of communities with a high and a low degree of Z. marina and Z. noltei dominance was approximately the same. The occurrence of most macroalgal species almost did not depend on the density of Zostera thickets, and an increase in the degree of Zostera dominance could represent a danger only for a few species, such as charophytes Lamprothamnium papulosum and Chara baltica, endemic green algae Ulva maeotica, and the yellow–green algae Vaucheria dichotoma. [ABSTRACT FROM AUTHOR]

The chloroplast NADH dehydrogenase-like (NDH) complex, homologous to respiratory complex I, participates in photosystem I cyclic electron flow (PSI-CEF) and chlororespiration in photosynthesis. Phylogenetic analyses indicated that Zostera marina, a widely distributed seagrass, has a complete NDH complex, which is rarely observed in marine macrophytes. We identified all 31 ndh genes necessary for the functional NDH complex, of which ndhB and pnsb3 occurred as duplication events. Secondary structural analyses of antiporter-like subunits showed that the long amphipathic helix of NdhF was lost in Z. marina, which could exhibit an alternative mode in the generation of trans-thylakoid proton gradient. The splicing pattern of ndh exhibited tissue-specific patterns and responded to light stress. RNA editing in Z. marina presented the ancestral pattern with many of the primitive editing sites and types. The partial editing in ndhF reflected the link between light stress and RNA editing. Moreover, the predominant expression in leaves of most ndh genes suggested that their major function is in photosynthesis. The quantitative real time-PCR results show that the expression of ndh was significantly upregulated in response to light stress. Nevertheless, there were two diverse responsive mechanisms of the NDH complex in PSI-CEF and chlororespiration. Overall, the presence of a complete structure, upregulated gene expression level, and multiple post-transcriptional regulations could provide a molecular basis for the powerful NDH complex and enable Z. marina to maintain effective photosynthetic performance. [ABSTRACT FROM AUTHOR]

Abstract—Features of the species and spatial structure of sublittoral macrobenthic communities in a lagoon ecosystem of Green Cape (White Sea) have been studied. Thirty-one invertebrate species and three species of sea grasses and algae (Zostera marina, Cladophora sericea, and Fucus vesiculosus) were found in the sublittoral zone of the surveyed lagoon. The data on the species composition, diversity, and spatial structure of macrobenthos communities indicate the predominance of littoral brackish water and marine euryhaline macrobenthos species (Hydrobia ulvae, Tubificoides benedii, Chironomus salinarius, and Macoma balthica) in the coastal region of the lagoon, marine littoral and sublittoral euryhaline species (mainly polychaetes Heteromastus filiformis, Polydora ciliata, and Capitella capitata) in the central deeper region, and marine sublittoral less euryhaline species (Pontoporeia femorata, Anonyx nugans, Nereimyra punctata, Terebellides stroemi, Astarte montagui, Micronephthys minuta, and Atylus carinatus) at the outlet of the lagoon. The ecosystem of the Green Cape lagoon belongs to lagoons heavily separated from the sea with depleted specific fauna (many littoral species) and largely influenced by the carbon load and salinity. The reduced connectivity of the lagoon with the sea due to the continued rise of the White Sea coast (4 mm per year in this area) will contribute to a decrease in the species diversity and the dominance of a few small eurytopic invertebrate species resistant to organic load, oxygen deficiency, and desalination. [ABSTRACT FROM AUTHOR]

Globally, habitat loss in coastal marine systems is a major driver of species decline, and estuaries are particularly susceptible to loss. Along the United States Pacific coast, monospecific eelgrass (Zostera marina) beds form the major estuarine vegetated habitat. In Morro Bay, California, eelgrass experienced an unprecedented decline of > 95%, from 139 ha in 2007 to < 6 ha by 2017. Fish populations were compared before and after the eelgrass decline using trawl surveys. Beach seines surveys were also conducted during the post-decline period to characterize species within and outside of remnant eelgrass beds. While the estuary-wide loss of eelgrass did not result in fewer fish or less biomass, it led to changes in species composition. The post-eelgrass decline period was characterized by increases in flatfish (mainly Citharichthys stigmaeus) and staghorn sculpin (Leptocottus armatus), and decreases in habitat specialists including bay pipefish (Syngnathus leptorhynchus) and shiner perch (Cymatogaster aggregata). There were similar trends inside and outside of remnant eelgrass patches. These findings support evidence across multiple ecosystems suggesting that the predominance of habitat-specialists predicts whether or not habitat loss leads to an overall decline in fish abundance. In addition, loss of critical habitats across seascapes can restrict population connectivity and lead to range contraction. For bay pipefish, the loss of eelgrass in Morro Bay is likely to create a population biogeographic divide. Currently, Morro Bay is dominated by flatfish and sculpins, and the longevity of this new ecosystem state will depend on future eelgrass recovery dynamics supported by ecosystem-based management approaches. [ABSTRACT FROM AUTHOR]

Thus, rhizomes characteristically had higher contents of salt-soluble proteins than the other parts of I Z. marina i ; stems, base-soluble; leaves and seeds, water-soluble. Proteins from leaves and seeds had higher RBA than those from rhizomes and stems. Nonessential AAs in anatomical parts of I Z. marina i were represented most by glutamic and aspartic acids (total from 19.2% in stems to 23.7% in seeds). [Extracted from the article]

The temporal changes in the fish community structure before and after a tsunami in 2011 were investigated in Funakoshi and Otsuchi bays, Iwate prefecture, on the Pacific coast of northern Japan. Fish species richness, abundance, biomass, and species composition were analyzed in relation to temporal variability of biotic and abiotic environmental conditions in two sub-intertidal seagrass Zostera marina beds. Mean seagrass shoot density decreased to < 5.8% of its original density after the tsunami, and gradually increased during the following survey periods in both bays. A total of 5206 fishes (74 taxa, 36 families) were collected by quantitative sampling for 10 years from 2009 to 2018. The Embiotocidae fishes dominated in terms of biomass in both bays. Mean seagrass shoot density had the most significant positive effect on total fish biomass in Funakoshi Bay. Fish species richness decreased immediately after the tsunami in both bays, corresponding to the drastic decrease in seagrass shoot density. Thereafter, the species richness gradually increased during the post-disturbance period of 7 years. In summer 2017, after approximately 6 years since the tsunami occurred, the seagrass habitat had recovered, and the fish community became similar to that before the tsunami disturbance in both bays. [ABSTRACT FROM AUTHOR]

Seagrasses, a polyphyletic group of about 60 marine angiosperm species, are the foundation of diverse and functionally important marine habitats along sheltered sedimentary coasts. As a novel ecological function with high societal relevance, a role of the seagrass leaf canopy for reducing potentially harmful bacteria has recently been hypothesized in tropical regions, but data for temperate regions are lacking. Here, we tested whether or not the abundance of general bacteria and more specifically, those belonging to the genus Vibrio were reduced within temperate Zostera marina (eelgrass) meadows compared to adjacent sand flats and sampled 5 sites in the south-western Baltic Sea using SCUBA. Compared to non-vegetated area, we found an average reduction of 39% for all Vibrio and 63% for the potentially harmful V. vulnificus/cholerae subtype based on robust plate counting data on Vibrio selective agar. The underlying mechanism of the reduction in bacterial load is currently elusive and clearly merits further study. Our results underline the critical importance of seagrasses in maintaining shallow water ecosystem functioning including water quality and provide further motivation for their protection and restoration. [ABSTRACT FROM AUTHOR]

Purpose: Seagrasses accelerate sedimentation, release oxygen and organic matter through their roots, and compete with ammonia oxidizers for ammonia/ammonium in surface sediments and overlying water, all of which can influence benthic aerobic nitrification. To understand the effects of seagrass vegetation on benthic nitrification, the heterogeneity of nitrification activities and functional microbial communities between seagrass-vegetated and adjacent bare sediments was investigated. Materials and methods: Surface (0–5 cm) sediments were sampled from a Zostera marina-colonized coastal lagoon in northern China. The potential nitrification rates (PNR) and relative contributions of ammonia-oxidizing bacteria (PNRaob) and ammonia-oxidizing archaea (PNRaoa) were determined based on the sediment slurry incubation with kanamycin inhibition method. The abundances and community compositions of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) were determined using qPCR, clone library, and high-throughput sequencing. Results and discussion: The total PNR (PNRtotal) in the seagrass-colonized sediments were significant higher than those in the bare sediments (P < 0.05), to which PNRaob contributed 59.7% and 55.8% in vegetated and unvegetated sediments, respectively. The concentrations of chlorophyll a and dissolved inorganic nitrogen were key factors determining benthic PNR. AOB outnumbered AOA by one order of magnitude by targeting amoA gene abundance, and no significant difference (P > 0.05) in amoA gene abundance and diversity was observed between the two habitats. Most AOB genotypes were affiliated to Nitrosomonas, of which NL7 was selectively enriched in the vegetated region, while N. cryotolerans prevailed in the bare. Two distinct AOA groups Crenarchaeota 1.1b and Crenarchaeota 1.1a dominated in vegetated and unvegetated sediments, respectively. Dissolved oxygen of overlying water and TOC:TN of sediment significantly influenced AOB community, while AOA community was strongly driven by nitrate and metal iron in sediments. Conclusions: Seagrass vegetation substantially enhances nitrification potential and selects specific ammonia oxidizers in coastal sediments. [ABSTRACT FROM AUTHOR]

The potential productivity of oysters and mussels was estimated for Voevoda Bay (Russky Island, Primorskii krai) using the FARM model. The main sources of primary production in the study area are seagrass (Zostera marina) and phytoplankton (diatoms). The area of Zostera growth was delineated based on the bottom survey of the bay. The parameters of organic matter production of Zostera and phytoplankton for each computational grid cell were modeled using the ECO BLOOM II Algae module, which is part of the DELWAQ model of the Delft3D software package. Spatial redistribution of organic matter, chlorophyll a and phytoplankton were simulated using the results of hydrodynamic modelling of the DELFT3D Flow. The values of biological (primary production) and hydrochemical (temperature, salinity, oxygen content) parameters, obtained for each computational grid cell were used as input to the FARM. The empirical exceedance probability curves of modelled productivity for pasture and cage cultivation of the giant oyster (Crassostrea gigas) and the Pacific mussel (Mytilus trossulus) were calculated for each cell. The spatial distribution for the potential productivity values of the representative exceedance probability (50, 75, and 95%) for both types of cultivation was mapped. [ABSTRACT FROM AUTHOR]

For the first time, intraspecific relationships between the macroecological metrics patchiness (P) and both abundance (A) and occupancy (O) were investigated in a faunal assemblage. As a companion study to recent work on interspecific P, A and O patterns at the same localities, intraspecific patterns were documented within each of the more dominant invertebrates forming the seagrass macrobenthos of warm–temperate Knysna estuarine bay (South Africa) and of sub-tropical Moreton Bay (Australia). As displayed interspecifically, individual species showed strong A–O patterns (mean scaling coefficient − 0.76 and mean R2 > 0.8). All P–O relations were negative and most (67%) were statistically significant, although weaker (mean R2 0.5) than A–O ones; most P–A ones were also negative but fewer (43%) achieved significance, and were even weaker (mean R2 0.4); 33% of species showed no significant interrelations of either O or A with P. No species showed only a significant P–A relationship. Compared with interspecific P–A–O data from the same assemblages, power–law scaling exponents were equivalent, but R2 values were larger. Larviparous species comprised 70% of the total studied, but 94% of those displaying significant patchiness interrelationships; 5 of the 9 showing no P–A or P–O relationships, however, were also larviparous. At Knysna, though not in Moreton Bay, larviparous species also showed higher levels of occupancy than non-larviparous ones, whilst non-larviparous species showed higher levels of patchiness. Dominant Moreton Bay species, but not those at Knysna, exhibited homogeneously sloped P–O relationships. [ABSTRACT FROM AUTHOR]

Quantifying the strength of non-trophic interactions exerted by foundation species is critical to understanding how natural communities respond to environmental stress. In the case of ocean acidification (OA), submerged marine macrophytes, such as seagrasses, may create local areas of elevated pH due to their capacity to sequester dissolved inorganic carbon through photosynthesis. However, although seagrasses may increase seawater pH during the day, they can also decrease pH at night due to respiration. Therefore, it remains unclear how consequences of such diel fluctuations may unfold for organisms vulnerable to OA. We established mesocosms containing different levels of seagrass biomass (Zostera marina) to create a gradient of carbonate chemistry conditions and explored consequences for growth of juvenile and adult oysters (Crassostrea gigas), a non-native species widely used in aquaculture that can co-occur, and is often grown, in proximity to seagrass beds. In particular, we investigated whether increased diel fluctuations in pH due to seagrass metabolism affected oyster growth. Seagrasses increased daytime pH up to 0.4 units but had little effect on nighttime pH (reductions less than 0.02 units). Thus, both the average pH and the amplitude of diel pH fluctuations increased with greater seagrass biomass. The highest seagrass biomass increased oyster shell growth rate (mm day−1) up to 40%. Oyster somatic tissue weight and oyster condition index exhibited a different pattern, peaking at intermediate levels of seagrass biomass. This work demonstrates the ability of seagrasses to facilitate oyster calcification and illustrates how non-trophic metabolic interactions can modulate effects of environmental change. [ABSTRACT FROM AUTHOR]

Non-photochemical quenching (NPQ) of photosystem II (PSII) fluorescence is one of the most important protective mechanisms enabling the survival of phototropic organisms under high-light conditions. A low-efficiency NPQ, characterized by weak NPQ induction capacity and a low level of protective NPQ, was observed in the marine angiosperm Zostera marina, which inhabits the shallow water regions. Furthermore, chlorophyll fluorescence and Western blot analysis verified that the fast-inducted component of NPQ, i.e., the energy-dependent quenching (qE), was not present in this species. In contrast with the lack of PSII antenna quenching sites for qE induction in brown algae and the lack of functional XC in Ulvophyceae belonging to green algae, all the antenna proteins and the functional XC are present in Z. marina. A novel underlying mechanism was observed that the limited construction of the trans-thylakoid proton gradient (ΔpH) caused by photoinactivation of the oxygen evolving complex (OEC) did not induce protonation of PsbS, thus explaining the inability to form quenching sites for qE induction. Although the ΔpH established under light exposure activated violaxanthin (V) de-epoxidase enzyme to catalyze conversion of V via antheraxanthin (A) and then to zeaxanthin (Z), the quenching capacity of de-epoxidized pigment was weak in Z. marina. We suggest that the low-efficiency NPQ was conducive to efficiently utilize the limited electrons to perform photosynthesis, resisting the adverse effect of OEC photoinactivation on the photosynthetic rate. [ABSTRACT FROM AUTHOR]