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Interactions such as mutualism and facilitation are common in ecosystems established by foundation species; however, their outcomes vary and show conditionality. In a Mexican Caribbean Bay, a seagrass-coralline algae (rhodoliths) mutualism protects the seagrass Thalassia testudinum from green turtle overgrazing. We postulate that the state of the seagrass meadow in this bay depends on the strengths of the interactions among seagrasses, green turtles, and coralline algae. Spatio-temporal changes through satellite imagery showed rhodolith bed developed rapidly from 2009 (undetected) to 2016 (bed of 6934 m2). Typically, such rapid expansion of the rhodoliths does not occur in seagrass meadows. An in situ growth experiment of coralline algae showed that a combination of reduction in light and wave movement (usual in dense seagrass meadows) significantly reduced their growth rates. In the rhodolith beds, the growth rates of the coralline algae Neogoniolithon sp. and Amphiroa sp. were high at 9.5 mm and 15.5 mm per growth tip y−1, respectively. In a second experiment, we found lower mortality in coralline algae within a rhodolith bed compared to algae placed outside the bed, likely explained by the reduced resuspension that we found in a third experiment, and this positive feedback may explain the high population increase in the rhodoliths, once established when the turtles grazed down the seagrass canopy. Therefore, the grazing-protection mutualism between seagrasses and coralline algae is thus conditional and came into existence under a co-occurrence of intensive grazing pressure and rapid population growth of coralline algae facilitated by positive feedback from increased growth and reduced sediment resuspension by the dense rhodolith bed. [ABSTRACT FROM AUTHOR]

Thalassia testudinum has undergone die-offs in the past century due to seagrass wasting disease caused by Labyrinthula sp. Little is known about how seagrasses resist Labyrinthula infections, but metabolites that inhibit Labyrinthula were previously extracted from seagrass leaves. Furthermore, leaf fungal endophytes from seagrasses possess antipathogenic potential, but their activity against Labyrinthula is unknown. Here, we aimed to identify whether fungal endophytes of T. testudinum can aid in disease defense against Labyrinthula. Through Illumina amplicon sequencing of the leaves' mycobiome, we identified fungi that are known to produce antimicrobials. We also isolated and extracted organic compounds from endophytes to test their anti-Labyrinthula potential using disk diffusion assays. There were 22 isolates that inhibited Labyrinthula, from which two isolates, Trichoderma sp. P1a and Diaporthe sp. M14, displayed strong inhibition. LC-HRMS/MS analysis determined the likely bioactive compounds of Trichoderma as peptaibols and of Diaporthe as cytosporone B. Cytosporone B was confirmed bioactive against Labyrinthula via disk diffusion assays. While these organisms are low in abundance in the mycobiome, this study demonstrates that seagrass endophytes have the potential to play an important role in defense against Labyrinthula. [ABSTRACT FROM AUTHOR]

Plant microbiomes are known to serve several important functions for their host, and it is therefore important to understand their composition as well as the factors that may influence these microbial communities. The microbiome of Thalassia testudinum has only recently been explored, and studies to-date have primarily focused on characterizing the microbiome of plants in a single region. Here, we present the first characterization of the composition of the microbial communities of T. testudinum across a wide geographical range spanning three distinct regions with varying physicochemical conditions. We collected samples of leaves, roots, sediment, and water from six sites throughout the Atlantic Ocean, Caribbean Sea, and the Gulf of Mexico. We then analyzed these samples using 16S rRNA amplicon sequencing. We found that site and region can influence the microbial communities of T. testudinum, while maintaining a plant-associated core microbiome. A comprehensive comparison of available microbial community data from T. testudinum studies determined a core microbiome composed of 14 ASVs that consisted mostly of the family Rhodobacteraceae. The most abundant genera in the microbial communities included organisms with possible plant-beneficial functions, like plant-growth promoting taxa, disease suppressing taxa, and nitrogen fixers. [ABSTRACT FROM AUTHOR]

Thalassia testudinum has undergone die-offs in the past century due to seagrass wasting disease caused by Labyrinthula sp. Little is known about how seagrasses resist Labyrinthula infections, but metabolites that inhibit Labyrinthula were previously extracted from seagrass leaves. Furthermore, leaf fungal endophytes from seagrasses possess antipathogenic potential, but their activity against Labyrinthula is unknown. Here, we aimed to identify whether fungal endophytes of T. testudinum can aid in disease defense against Labyrinthula. Through Illumina amplicon sequencing of the leaves’ mycobiome, we identified fungi that are known to produce antimicrobials. We also isolated and extracted organic compounds from endophytes to test their anti-Labyrinthula potential using disk diffusion assays. There were 22 isolates that inhibited Labyrinthula, from which two isolates, Trichoderma sp. P1a and Diaporthe sp. M14, displayed strong inhibition. LC-HRMS/MS analysis determined the likely bioactive compounds of Trichoderma as peptaibols and of Diaporthe as cytosporone B. Cytosporone B was confirmed bioactive against Labyrinthula via disk diffusion assays. While these organisms are low in abundance in the mycobiome, this study demonstrates that seagrass endophytes have the potential to play an important role in defense against Labyrinthula.

Plant microbiomes are known to serve several important functions for their host, and it is therefore important to understand their composition as well as the factors that may influence these microbial communities. The microbiome of Thalassia testudinum has only recently been explored, and studies to-date have primarily focused on characterizing the microbiome of plants in a single region. Here, we present the first characterization of the composition of the microbial communities of T. testudinum across a wide geographical range spanning three distinct regions with varying physicochemical conditions. We collected samples of leaves, roots, sediment, and water from six sites throughout the Atlantic Ocean, Caribbean Sea, and the Gulf of Mexico. We then analyzed these samples using 16S rRNA amplicon sequencing. We found that site and region can influence the microbial communities of T. testudinum, while maintaining a plant-associated core microbiome. A comprehensive comparison of available microbial community data from T. testudinum studies determined a core microbiome composed of 14 ASVs that consisted mostly of the family Rhodobacteraceae. The most abundant genera in the microbial communities included organisms with possible plant-beneficial functions, like plant-growth promoting taxa, disease suppressing taxa, and nitrogen fixers.

Recreational boating in turtle-grass (Thalassia testudinum) dominated bays has resulted in high density areas of propeller scarring, potentially compromising marine habitat and ecosystem services. Given turtle-grass growth habits, recruitment into substantial propeller scars may take up to 10 years to reach normal density. Assessment by aerial photointerpretation coupled with installation of biodegradable sediment tubes can facilitate restoration of impacted turtle-grass beds. We teamed with the Florida Department of Environmental Protection Central Panhandle Aquatic Preserve staff to complete a multi-phase restoration project to assess, map. quantify sediment loss, and develop/implement a restoration strategy to address propeller scar impacts in St. Joseph Bay Aquatic Preserve (AP) in the Florida panhandle. Propeller scar assessment was based on high resolution aerial imagery of seagrass beds within the AP acquired by small unmanned aerial vehicles. Resultant imagery was analyzed with photointerpretation to create propeller scar maps that were verified by extensive fieldbased signature development, ground control, and spatial and thematic assessment. Hot spot analysis, quantification, and classification results were utilized to identify areas of the highest scarring density for potential restoration. Analyses identified 789 potential candidate scars totaling 1 hectare within 11 targeted areas located in the AP. Restoration implementation included placement of biodegradable sediment tubes within propeller scars that met specific length and depth thresholds. Biofouling was evident within days of installation and partial to full sediment tube degradation was observed within 6 months. The AP restoration concluded with deployment of 43,954 sediment tubes in 379 propeller scars, equating to nearly 40 kilometers or 0.8 hectare of restored propeller scars. Initial postrestoration monitoring results one year after implementation demonstrate successful re-establishment of sediments, natural grade, and seagrass spread in treated propeller scars. [ABSTRACT FROM AUTHOR]

The seagrass ecosystem is considered one of the most effective coastal ecosystems in storing carbon. Carbon stock estimation for a certain ecosystem is highly affected by factors such as species diversity and habitat type. This study aims to investigate the relationship between plant community structure and carbon stocks in the seagrass ecosystem using a case study of six coastal sites in Karimunjawa Marine National Park, Indonesia. In this region, eight seagrass species were recorded, i.e., Enhalus acoroides, Thalassia hemprichii, Cymodocea rotundata, Halodule pinifolia, Halophila ovalis, Halophila minor, Syringodium isoetifolium, and Oceana serrulata. From the six study sites, the highest estimated carbon stock was 426.2 Mg C ha−1 (Site 5; Telaga, dominated by E. acoroides). Meanwhile, the lowest estimated carbon stock was 127.4 Mg C ha−1 (Site 4; Koin, dominated by T. hemprichii). The density of E. acoroides was positively correlated with the total seagrass biomass carbon stocks (r = 0.97; p < 0.01), while its dominance was positively correlated with sediment carbon stocks (r = 0.92; p < 0.05) and total seagrass ecosystem carbon stocks (r = 0.92; p < 0.05). Seagrass ecosystems with different community structures showed different carbon storage capacities. Seagrass ecosystems dominated by large-sized species such as E. acoroides showed higher estimated carbon stocks thus suggesting the importance of considering the variability of community structure in managing seagrass ecosystems for carbon sequestration and storage. [ABSTRACT FROM AUTHOR]

Seagrass ecosystems are storehouses of both autochthonous and allochthonous organic matter due to their presence at the land and sea interface. This organic matter acts as a food source and plays an important role in biodiversity assemblages within seagrass ecosystems. The present study assessed the density of the bivalve (Cardita calyculata) along a gradient of sediment Organic Matter (OM %) in the mono-specific seagrass meadows of Thalassia hemprichii to those in adjacent bare sediments in the Andaman and Nicobar Islands (ANI) of India. The present study also assessed the correlation between sediment OM with Cardita's density and seagrass morphometric traits. C. calyculata density was 2-fold higher in T. hemprichii meadows (647.7±27.0 ind. m-2) than in the bare sediment (306±14.3 ind. m-2). Bivalve abundance correlated positively with OM in the seagrass meadows but showed no correlation in the unvegetated areas. The root branching of seagrass was higher, leading to increased C. calyculata density, suggesting a strong correlation of seagrass meadows with bivalves in nutrient-rich environments. The correlations between C. calyculata density and various plant traits were positive. Our study suggests that in the oligotrophic coastal ecosystems of the ANI, the positive influence of sediment OM of seagrass meadows on C. calyculata density is significant. Further studies looking at various interactions between seagrass and C. calyculata are essential to establish the precise interrelationship between seagrass and the biodiversity of associated faunal assemblages. [ABSTRACT FROM AUTHOR]

Large grazers (megaherbivores) have a profound impact on ecosystem functioning. However, how ecosystem multifunctionality is affected by changes in megaherbivore populations remains poorly understood. Understanding the total impact on ecosystem multifunctionality requires an integrative ecosystem approach, which is especially challenging to obtain in marine systems. We assessed the effects of experimentally simulated grazing intensity scenarios on ecosystem functions and multifunctionality in a tropical Caribbean seagrass ecosystem. As a model, we selected a key marine megaherbivore, the green turtle, whose ecological role is rapidly unfolding in numerous foraging areas where populations are recovering through conservation after centuries of decline, with an increase in recorded overgrazing episodes. To quantify the effects, we employed a novel integrated index of seagrass ecosystem multifunctionality based upon multiple, well‐recognized measures of seagrass ecosystem functions that reflect ecosystem services. Experiments revealed that intermediate turtle grazing resulted in the highest rates of nutrient cycling and carbon storage, while sediment stabilization, decomposition rates, epifauna richness, and fish biomass are highest in the absence of turtle grazing. In contrast, intense grazing resulted in disproportionally large effects on ecosystem functions and a collapse of multifunctionality. These results imply that (i) the return of a megaherbivore can exert strong effects on coastal ecosystem functions and multifunctionality, (ii) conservation efforts that are skewed toward megaherbivores, but ignore their key drivers like predators or habitat, will likely result in overgrazing‐induced loss of multifunctionality, and (iii) the multifunctionality index shows great potential as a quantitative tool to assess ecosystem performance. Considerable and rapid alterations in megaherbivore abundance (both through extinction and conservation) cause an imbalance in ecosystem functioning and substantially alter or even compromise ecosystem services that help to negate global change effects. An integrative ecosystem approach in environmental management is urgently required to protect and enhance ecosystem multifunctionality. [ABSTRACT FROM AUTHOR]

Drift macroalgae, often found in clumps or mats adjacent to or within seagrass beds, can increase the value of seagrass beds as habitat for nekton via added food resources and structural complexity. But, as algal biomass increases, it can also decrease light availability, inhibit faunal movements, smother benthic communities, and contribute to hypoxia, all of which can reduce nekton abundance. We quantified the abundance and distribution of drift macroalgae within seagrass meadows dominated by turtle grass Thalassia testudinum across the northern Gulf of Mexico and compared seagrass characteristics to macroalgal biomass and distribution. Drift macroalgae were most abundant in areas with higher seagrass shoot densities and intermediate canopy heights. We did not find significant relationships between algal biomass and point measures of salinity, temperature, or depth. The macroalgal genera Laurencia and Gracilaria were present across the study region, Agardhiella and Digenia were collected in the western Gulf of Mexico, and Acanthophora was collected in the eastern Gulf of Mexico. Our survey revealed drift algae to be abundant and widespread throughout seagrass meadows in the northern Gulf of Mexico, which likely influences the habitat value of seagrass ecosystems. [ABSTRACT FROM AUTHOR]

To understand the demographic responses of green turtles to seagrass decline, we examined a data set from study of a mixed-stock foraging aggregation of immature green turtles, Chelonia mydas, collected in Bermuda (32o18'N, − 64o46'W) over five decades. Average turtle size (SCLmin) and mass declined by 22.3% and 58.2%, respectively. Aggregation size structure shifted to smaller sizes and now consists of more small turtles and fewer large turtles. Density (turtles ha−1) increased significantly but biomass (kg ha−1) remained unchanged and low compared to C. mydas biomass observed elsewhere. Green turtles exhibited reduced site fidelity during two portions of the study period, suggesting increased foraging effort. Reduction in turtle body condition index and seagrass coverage occurred from offshore to inshore. Changes in aggregation composition and behavior were consistent with expectations given a documented decline in seagrass availability, combined with increased output from source rookeries. Apparent response to resource decline is traced back to 1976, well before seagrass loss was first documented. Green turtles and their primary food source (Thalassia testudinum) are at the northern limit of their range in Bermuda, where seagrasses would be expected to have a reduced tolerance for natural grazing pressure and increased susceptibility to synergistic stressors, especially temperature, bioturbation and phosphorus limitation. Our results suggest that synergistic stressors, and not green turtles alone, have produced the observed reduction in seagrasses on the Bermuda Platform. Given that seagrass declines have been reported worldwide, our findings may suggest how green turtles will respond elsewhere. [ABSTRACT FROM AUTHOR]

Drift macroalgae, often found in clumps or mats adjacent to or within seagrass beds, can increase the value of seagrass beds as habitat for nekton via added food resources and structural complexity. But, as algal biomass increases, it can also decrease light availability, inhibit faunal movements, smother benthic communities, and contribute to hypoxia, all of which can reduce nekton abundance. We quantified the abundance and distribution of drift macroalgae within seagrass meadows dominated by turtle grass Thalassia testudinum across the northern Gulf of Mexico and compared seagrass characteristics to macroalgal biomass and distribution. Drift macroalgae were most abundant in areas with higher seagrass shoot densities and intermediate canopy heights. We did not find significant relationships between algal biomass and point measures of salinity, temperature, or depth. The macroalgal genera Laurencia and Gracilaria were present across the study region, Agardhiella and Digenia were collected in the western Gulf of Mexico, and Acanthophora was collected in the eastern Gulf of Mexico. Our survey revealed drift algae to be abundant and widespread throughout seagrass meadows in the northern Gulf of Mexico, which likely influences the habitat value of seagrass ecosystems.

Seagrass has important ecological functions, namely as a nursery-grown, spawning and protection areas for marine biota. In the world, there are 60 species of seagrasses, and in Indonesia, there are 14 species from 7 genera. The waters of North Sulawesi store a high potential of seagrass ecosystems. This study aimed to observe the distribution of seagrass from the Bahoi, Manembo-Nembo, and Tandurusa coast, North Sulawesi, Indonesia. Sampling carried out at the lowest ebb at the lunar or full moon phase. The method used for sampling is random, both for transect and squared lines. The results showed that from the Bahoi, Menembo-Nembo and Tandurusa coast, ten seagrass species from 7 genera and two families were found, namely Enhallus acoroides, Cymodocea rotundata, Cymodocea serrulata, Halodule uninervis, Halodule pinifolia, Halophila minor, Halophla ovalis, Syringodium isoetifolium, Thalassia hemprichii, dan Thalassodendron ciliatum. Information on seagrass distribution in an area can be taken into consideration for the government and related agencies in drafting a regulation in the management of seagrass ecosystem resources.

Seven species of seagrass have been found in the Indian River Lagoon (IRL), making it an unusually diverse location at the global scale. From 1994 to 2019, the lagoon-wide distribution of these species reflected variations in temperature, salinity, and the availability of light at depth, which were related to latitudinal differences in hydrology and hydrodynamics along the IRL. In general, species richness was higher near the four southern inlets, and fewer species were found in areas with longer residence times for water. At a finer scale, the distribution of species varied among depths, with the greatest number of species found at mid-depths (~0.4-0.9 m). Prior to 2011, these patterns remained relatively consistent for ~ 40 years, but several, intense and prolonged phytoplankton blooms disrupted them. The areal extent of all seagrasses decreased by over 50%, the offshore ends of canopies moved shoreward and shallower, distributions of species along gradients of latitude and depth were disrupted, and mean percent cover decreased. Major changes in distribution and abundance of seagrasses arose when salinity, temperature, and availability of light at depth exceeded limits derived for each species. These substantial and widespread changes engendered concerns for recovery or rehabilitation of seagrasses in the lagoon. [ABSTRACT FROM AUTHOR]

The intensity of major storm events generated within the Atlantic Basin is projected to rise with the warming of the oceans, which is likely to exacerbate coastal erosion. Nature-based flood defence has been proposed as a sustainable and effective solution to protect coastlines. However, the ability of natural ecosystems to withstand major storms like tropical hurricanes has yet to be thoroughly tested. Seagrass meadows both stabilise sediment and attenuate waves, providing effective coastal protection services for sandy beaches. To examine the tolerance of Caribbean seagrass meadows to extreme storm events, and to investigate the extent of protection they deliver to beaches, we employed a combination of field surveys, biomechanical measurements and wave modelling simulations. Field surveys of seagrass meadows before and after a direct hit by the category 5 Hurricane Irma documented that established seagrass meadows of Thalassia testudinum remained unaltered after the extreme storm event. The flexible leaves and thalli of seagrass and calcifying macroalgae inhabiting the meadows were shown to sustain the wave forces that they are likely to experience during hurricanes. In addition, the seagrass canopy and the complex biogeomorphic landscape built by the seagrass meadows combine to significantly dissipate extreme wave forces, ensuring that erosion is minimised within sandy beach foreshores. The persistence of the Caribbean seagrass meadows and their coastal protection services during extreme storm events ensures that a stable coastal ecosystem and beach foreshore is maintained in tropical regions. [ABSTRACT FROM AUTHOR]

Abstract Background Seagrasses are foundation species in estuarine and lagoon systems, providing a wide array of services for the ecosystem and the human population. Understanding the dynamics of their stands is essential in order to better assess natural and anthropogenic impacts. It is usually considered that healthy seagrasses aim to maximize their stand biomass (g DW m−2) which may be constrained by resource availability i.e., the local environment sets a carrying capacity. Recently, this paradigm has been tested and reassessed, and it is believed that seagrasses actually maximize their efficiency of space occupation—i.e., aim to reach an interspecific boundary line (IBL)—as quick as possible. This requires that they simultaneously grow in biomass and iterate new shoots to increase density. However, this strategy depresses their biomass potential. Results to comply with this new paradigm, we developed a seagrass growth model that updates the carrying capacities for biomass and shoot density from the seagrass IBL at each time step. The use of a joint biomass and density growth rates enabled parameter estimation with twice the sample sizes and made the model less sensitive to episodic error in either of the variables. The use of instantaneous growth rates enabled the model to be calibrated with data sampled at widely different time intervals. We used data from 24 studies of six seagrass species scattered worldwide. The forecasted allometric biomass–density growth trajectories fit these observations well. Maximum growth and decay rates were found consistently for each species. The growth rates varied seasonally, matching previous observations. Conclusions State-of-art models predicting both biomass and shoot density in seagrass have not previously incorporated our observation across many seagrass species that dynamics depend on current state relative to IBL. Our model better simulates the biomass–density dynamics of seagrass stands while shedding light on its intricacies. However, it is only valid for established patches where dynamics involve space-filling, not for colonization of new areas.

Seagrasses are productive habitats that support diverse communities of economically and ecologically important fishes and macroinvertebrates. However, most seagrass faunal assessments are conducted only during daylight hours. Here, we documented diel patterns in seagrass-associated fish and macroinvertebrate community structure in seagrass near Seahorse Key, Florida (USA). Artificial light is prevalent in many coastal areas and may influence day/night assemblages; therefore, we added lights to the natural environment to get a better understanding of its effect on community composition. Seagrass inhabitants were quantified using 25-m seine transects during different diel periods (day or night) and in areas where light was manipulated to mimic light pollution (artificial + natural light or natural light). Results suggest that the magnitude of diel effects exceeded that of light addition. While total abundance was similar between day and night, communities did change, with Lagodon rhomboides (Pinfish) dominating day samples and Farfantepenaeus duorarum (pink shrimp) most abundant at night. Other fishes such as Orthopristis chrysoptera (Pigfish) and Strongylura notata (Needlefish) had higher catches during the day, while invertebrates such as Callinectes sapidus (blue crab) and Palaeomonetes spp. (grass shrimp) were more prominent at night. In addition to the differences in abundance and community structure, we also identified diel differences in sizes for some species. No clear patterns were observed with the short-term addition of artificial light. This research highlights the role of diel variability in seagrass communities and suggests that diel movement of organisms may represent an important conduit for the transfer of energy to adjacent habitats. [ABSTRACT FROM AUTHOR]

The hypothesis that biotic interactions are stronger at lower relative to higher latitudes has a rich history, drawing from ecological and evolutionary theory. While this hypothesis suggests that stronger interactions at lower latitudes may contribute to the maintenance of contemporary patterns of diversity, there remain few standardized biogeographic comparisons of community effects of species interactions.Using marine seagrasses as a focal ecosystem of conservation importance and sessile marine invertebrates as model prey, we tested the hypothesis that predation is stronger at lower latitudes and can shape contemporary patterns of prey diversity. To further advance understanding beyond prior studies, we also explored mechanisms that likely underlie a change in interaction outcomes with latitude.Multiple observational and experimental approaches were employed to test for effects of predators, and the mechanisms that may underlie these effects, in seagrass ecosystems of the western Atlantic Ocean spanning 30° of latitude from the temperate zone to the tropics.In predator exclusion experiments conducted in a temperate and a tropical region, predation decreased sessile invertebrate abundance, richness and diversity on both natural and standardized artificial seagrass at tropical but not temperate sites. Further, predation reduced invertebrate richness at both local and regional scales in the tropics. Additional experiments demonstrated that predation reduced invertebrate recruitment in the tropics but not the temperate zone. Finally, direct observations of predators showed higher but variable consumption rates on invertebrates at tropical relative to temperate latitudes.Together, these results demonstrate that strong predation in the tropics can have consequential impacts on prey communities through discrete effects on early life stages as well as longer‐term cumulative effects on community structure and diversity. Our detailed experiments also provide some of the first data linking large‐scale biogeographic patterns, community‐scale interaction outcomes and direct observation of predators in the temperate zone and tropics. Therefore, our results support the hypothesis that predation is stronger in the tropics, but also elucidate some of the causes and consequences of this variation in shaping contemporary patterns of diversity. [ABSTRACT FROM AUTHOR]

Physical damage by motor vessels is a widespread problem for seagrass meadows, with hull and propeller strikes accounting for thousands of acres of impaired habitat in Florida, United States, alone. Because the excavations can become topographically unstable, and because recolonization and succession of seagrasses can require decades to reach climax, Thalassia testudinum‐dominated communities, there has been increasing efforts to regrade and stabilize impacted sediments, and to speed succession. A prior project involving eight vessel groundings in two hydrodynamic settings (high and low energy) examined the relative efficacy of capping injuries with sand‐filled fabric tubes or limestone pea rock, followed by planting of fast‐growing seagrass species and nutrient amendment using bird‐roosting stake deployments. Monitoring after 4 years showed recruitment of fast‐growing, subordinate species: Syringodium filiforme or Halodule wrightii, particularly in low‐energy environments; however, T. testudinum had not yet returned to natural densities. The current study extended monitoring an additional 3 years. At 7 years posteffort, T. testudinum recolonization was still incomplete. Of the eight sites, only three had statistically recovered. In low‐energy areas, H. wrightii cover was greater than in reference meadows, and a strong inverse relationship between H. wrightii and T. testudinum was observed. One explanation is that residual nutrients from bird feces switched the competitive outcome. We demonstrate using seagrass tissue N:P that nutrients delivered via bird stakes remained in the sediments of low‐energy environments, and argue that prolonged fertilization resulted in competitive advantages for H. wrightii, depressing T. testudinum recruitment and delaying recovery of the targeted seagrass community. [ABSTRACT FROM AUTHOR]

This study empirically examines predictions concerning boundary permeability as a function of patch contrast (i.e., the magnitude of difference in measures across patch interfaces), light level, and faunal mobility and density, as well as relative rates of emigration and immigration. I assessed permeability using invertebrate transfer in a macroalgal-seagrass-sand landscape, with particular emphasis on the caridean shrimp Thor floridanus. Proportional emigration was estimated by staining algal fauna in situ using neutral red (a live immersion stain) and then later collecting all animals in the algal clumps and in the surrounding sand or seagrass. Permeability was in part a function ofboundary contrast in this milieu; macroalgal patches were more of a closed system in sand than in seagrass. Contrary to predictions, proportional emigration across both the algal-seagrass and algal-sand boundaries was inversely related to faunal density. Another unexpected result was that the rate of change in emigration with increasing density was unaffected by differential contrast among habitat types. The observed enhanced permeability for more motile fauna was consistent with predictions. A related finding was thatpermeability was greater at night than during the day, probably as a function ofincreased nocturnal vagility of benthic fauna. Emigration was not in equilibriumwith immigration at the temporal scale of this study (hours) for the majority ofspecies tested. Emigration-immigration disequilibria should be most likely whenthe temporal scale is small, and in such cases caution should be exercised whenextrapolating from one transfer parameter to the other.

ABSTRACT Thalassia testudinum and Halodule wrigthii are the dominant seagrasses in the Caribbean, being common across shallow shorelines, either as monospecific or as intermixed meadows. Among the macrofauna associated with these beds, crustaceans are considered essential for the whole ecosystem functioning. However, knowledge about the associated community of decapod crustaceans in assemblages of T. testudinum and H. wrigthii is still scarce, particularly outside of protected areas. Here we report eight new decapod species for the Paraguaná Peninsula (Falcón State, Venezuela) in association with intermixed seagrass beds: Achelous tumidulus Stimpson, 1871, Alpheus aff. floridanus Kingsley, 1878, Chorinus heros (Herbst, 1790), Clibanarius antillensis (Stimpson, 1859), Clibanarius sclopetarius (Herbst, 1796), Latreutes parvulus (Stimpson, 1866), Panopeus occidentalis Saussure, 1857, and Processa fimbriata Manning & Chace, 1971. These records represent habitat extensions and fill gaps in the geographical distribution of the species along the northern coast of South America. Furthermore, we found that statistical differences in decapod species abundance and composition are likely to be caused by the joint action of coverage and heterogeneity of the beds. Our results indicate that typical Caribbean species were the most influential in the community; nevertheless, the abundance of juvenile Penaeus schmitti Burkenroad, 1936 was notable, since they have rarely been found in these habitats. This finding highlights the role of non-protected areas as nursery habitats for economically important species. Our results show that seagrass meadows in the Paraguaná Peninsula reflect overall good health when compared to other Caribbean zones, representing an important habitat for the maintenance of crustacean populations.

Background: Seagrasses are foundation species in estuarine and lagoon systems, providing a wide array of services for the ecosystem and the human population. Understanding the dynamics of their stands is essential in order to better assess natural and anthropogenic impacts. It is usually considered that healthy seagrasses aim to maximize their stand biomass (g DW m−2) which may be constrained by resource availability i.e., the local environment sets a carrying capacity. Recently, this paradigm has been tested and reassessed, and it is believed that seagrasses actually maximize their efficiency of space occupation—i.e., aim to reach an interspecific boundary line (IBL)—as quick as possible. This requires that they simultaneously grow in biomass and iterate new shoots to increase density. However, this strategy depresses their biomass potential. Results: to comply with this new paradigm, we developed a seagrass growth model that updates the carrying capacities for biomass and shoot density from the seagrass IBL at each time step. The use of a joint biomass and density growth rates enabled parameter estimation with twice the sample sizes and made the model less sensitive to episodic error in either of the variables. The use of instantaneous growth rates enabled the model to be calibrated with data sampled at widely different time intervals. We used data from 24 studies of six seagrass species scattered worldwide. The forecasted allometric biomass–density growth trajectories fit these observations well. Maximum growth and decay rates were found consistently for each species. The growth rates varied seasonally, matching previous observations. Conclusions: State-of-art models predicting both biomass and shoot density in seagrass have not previously incorporated our observation across many seagrass species that dynamics depend on current state relative to IBL. Our model better simulates the biomass–density dynamics of seagrass stands while shedding light on its intricacies. However, it is only valid for established patches where dynamics involve space-filling, not for colonization of new areas. [ABSTRACT FROM AUTHOR]

The abundance and distribution of Thalassia hemprichii (Ehrenb.) Aschers and Cymodocea rotundata Asch. & Schweinf. based on their different degrees of wave exposure and shore levels were investigated. T. hemprichii was the most dominant seagrass and occupied large areas from sheltered to exposed shores with the greatest percentage of cover (46±4.63%) whereas C. rotundata was restricted to the sheltered shore with a 12.22±4.95% cover. There were significant differences in abundance of these two species among the different degrees of wave action, shore sites, and month. Wave action might be the main influence on the percentage cover and distribution of these two seagrasses. In this study, the area covers of T. hemprichii and C. rotundata were around 0.104 km² and 0.096 km², respectively. [ABSTRACT FROM AUTHOR]

Abstract: Effective culturing and restocking of any commercial holothurian are dependent on understanding the biology and ecology of the species throughout its life history. Inherent differences between species require distinct strategies in larval and juvenile rearing. This study evaluated the effect of macroalgal and seagrass detritus as supplemental food on growth, feeding and sheltering behaviour, and biochemical composition of cultured Stichopus cf. horrens juveniles (2.6–3.8 g) under nursery rearing conditions. The addition of detritus to sediments did not significantly affect juvenile growth and body composition when compared to a biofilm‐only control. Average specific growth rates were positive throughout the experiment (1.58%–7.88% per day), however size variability, feeding rate, and sheltering behaviour differed significantly. Juveniles in treatments with macroalgal detritus had the highest coefficient of variation in weight (40%–51%) and a propensity to avoid sheltering near the sediments. This is presumably due to anoxic sediment conditions that developed in the macroalgal treatment over time. Juveniles in detritus treatments exhibited lower faecal production rates at the beginning of the experiment and after 75 days without significant differences in growth, suggesting the availability of high‐quality food in these treatments. This study provides key insights on husbandry conditions highly relevant to further develop S. cf. horrens aquaculture. [ABSTRACT FROM AUTHOR]

Introduction: Diabetes mellitus (DM) is an endocrine disorder characterized by high blood glucose levels. One of the approaches for treating DM is by regulating the postprandial blood glucose via inhibition of α-glucosidase enzymes. Seagrass is known as a plant containing bioactive compounds, especially for therapy antidiabetic. This research aims to evaluate the α-glucosidase inhibition activity of three species seagrasses (Enhalus acoroides, Thalassia hemprichii and Cymodocea rotundata) from the Banten Bay, Indonesia. Methods: The extracts of all parts (root, leaf, and stem) from three seagrasses were prepared with maceration method using 80% ethanol solvents. The α-glucosidase inhibitory activity was conducted by microplate reader at 400 nm using acarbose as a positive control. Furthermore, the kinetics of α-glucosidase inhibition, phytochemical screening, and total phenolics content were evaluated against extract which has the most potential α-glucosidase inhibition. Results: The result showed that the 80% ethanol extracts of Enhalus acoroides (IC50 values 168.15 ± 2.71 µg/mL) had the most potential α-glucosidase inhibitors activity compared with the positive control acarbose, Thalassia hemprichii and Cymodocea rotundata (IC50 values 197.27 ± 3.07 µg/mL, 425.86 ± 5.15 µg/mL and 429.28 ± 8.89 µg/mL). The kinetic type of inhibition against α-glucosidase was noncompetitive inhibition. The phytochemical compounds were phenols, flavonoid, terpenes, and tannin with the total phenolic content was 28.76 ± 2.46 mgGAE/g. Conclusion: Enhalus acoroides has the strongest inhibitor of α-glucosidase and can be further developed for DM therapy agents. [ABSTRACT FROM AUTHOR]

Accurate evaluation of target organisms is fundamental to quantify responses to disturbances, elucidate thresholds and strengthen effective management. Threats to seagrasses in Singapore are excessive nutrients and sedimentation, leading to an evaluation of descriptor utility to detect plant response to nutrient and light availability using Thalassia hemprichii as the model species. A combination of popularly used seagrass physio-morphological descriptors and epibiont biomass were measured to assess plant response to environmental quality. Results showed convincing support for the use of leaf pigments as indicators of light availability and salinity changes. Water column nitrification and phosphorus availability had strong effects on leaf nutrient content, leaf morphology and epibiont biomass. Relationships between leaf length and light contradicted expected patterns, where shorter leaves were associated with lowered light. This may be attributable to hydrodynamic or sedimentation regimes and hence, is not a reliable indicator of light limitation. There was strong support for inclusion of epibiont biomass as part of nutrient response evaluation since this descriptor correlated strongly with water column nutrients and appeared to limit light availability to the seagrass. This study demonstrated the importance of integrating various levels of plant descriptors to reliably assess seagrass status, employing different combination of descriptors to monitor specific stressors. [ABSTRACT FROM AUTHOR]

Seagrass ecosystems provide a multitude of ecosystem services by acting as a nursery, limiting erosion, improving water clarity, and acting as a globally-significant sink for atmospheric carbon dioxide. Despite the value of these services being estimated at $1.9 trillion, seagrass ecosystems are in global decline. As study of submerged aquatic vegetation (SAV) increase, specialized techniques are needed to map habitat coverage in regions which are largely inaccessible to current methods. Chief among these habitat types are seagrass meadows residing at depths of 1 m or less which are most susceptible to anthropogenic disturbance including physical disturbance. To encourage study of shallow SAV at large spatial scales a side scan sonar array was developed to efficiently map seagrass beds residing in 1 m or less of water. Constructed from consumer-grade sonar components the array cost approximately 10% of commercial units used in previous studies. The horizontal swath of the array in 1 m of water averaged 50 m in total (port plus starboard), allowing efficient study of large areas. Validation with satellite and aerial imagery of a large and highly-disturbed seagrass meadow demonstrates the array's capacity to produce high-resolution imagery (up to 2.5 cm/pixel) with sufficient spatial accuracy to produce detailed maps of seagrass habitat structure in very shallow environments. Results demonstrate operational readiness of the array, including benefits over traditional optical surveys during periods of high algal cover. The implications of an efficient, low-cost alternative to current mapping methods of seagrass habitats are discussed and a schematic for array construction is provided. [ABSTRACT FROM AUTHOR]

The population genetics of two seagrasses, Syringodium isoetifolium and Thalassia hemprichii were assessed throughout the Indonesian Archipelago. We genotyped 257 blades of S. isoetifolium at 15 microsatellite loci collected from 14 sampling sites and 406 blades of T. hemprichii at 17 microsatellite loci from 16 sampling sites. Once clones were removed, 165 individuals of S. isoetifolium and 389 of T. hemprichii were used in downstream analyses. Bayesian clustering methods revealed two genetically distinguishable clusters in each species, although the geographic boundaries of these clusters differed. Syringodium isoetifolium has a cluster that is located exclusively on the shallow Sunda Shelf and appears to follow the demarcation defined by Wallace's line. Thalassia hemprichii, however, has a genetically distinguishable cluster located within the Banda Sea. The Banda Sea has unique physical oceanographic conditions, which may be driving the observed differentiation in T. hemprichii. We speculate that historical sea level changes exposing the Sunda Shelf, and the unique oceanographic conditions of the Banda Sea are contributing to the observed population differentiation. The observed genetic differentiation in both species is a possible starting point for speciation. [ABSTRACT FROM AUTHOR]

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Seagrass beds are the largest organism-built marine habitat in Dominica, yet have only been surveyed since 2007. Standardized examinations along a depth gradient between 0 and 24m, focusing on magnoliophyte species composition and benthic cover of shoots at 17 seagrass bed sites, were carried out between September 10 and December 7, 2008. The Cymodoceaceae Syringodium filiforme (Kuetzing 1860) and Halodule wrightii (Ascherson 1868), as well as the Hydrocharitaceae Halophila decipiens (Ostenfeld 1902), H. stipulacea (Fosskal & Ascherson 1867) and Thalassia testudinum (Banks ex König 1805) displayed distinct regional and horizontal distribution patterns. Syringodium filiforme is the island’s dominant seagrass along the western and northern coasts, occurring at depths between 2 and 18m and with a mean benthic cover ranging from 0.9-10% along the West coast. Along the North coast it grew between 0.2 and 1m depth with a mean maximum benthic cover of 48.9%. Halodule wrightii grew along the North and West coasts, in depths between 1 and 14m in areas of recent and chronic disturbances. Its delicate morphology and sparse benthic cover (Pastos marinos son los ambientes más grandes constituidos por organismos en Dominica. Sin embargo, sólo se han examinado desde 2007. Entre el 10 de septiembre y 9 de diciembre 2008, se examinaron la composicion de especies y la densidad de magnoliofitas en profundidades de 0 a 24m. Los Cymodoceaceae: Syringodium filiforme y Halodule wrightii, tal como los Hydrocharitaceae: Halophila decipiens, H. stipulacea y Thalassia testudinum, mostraron una distribución regional y horizontal muy distinta. Syringodium filiforme fue la especie dominante en las costas del oeste y del norte de la isla. Se encontró en profundidades de 2 a 18m y con un promedio de cobertura béntica de 0.9-10% en la costa del oeste. En las costas del norte creció entre 0.2 y 1m de profundidad con un pormedio de cobertura béntica de 48.9%. Halodule wrightii creció en las costad del norte y oeste, en profundidades de 1 a 14m en áreas de perturbaciones recientes o crónicas. Su morfología delicada y su baja cobertura béntica (

The relative influence of top-down and bottom-up factors in seagrass communities has received considerable attention; however, individual seagrass attributes do not always respond in consistent fashion across studies. Because these metrics have been used as indicators of ecosystem stress, it is necessary to examine whether seagrass response to nutrient enrichment and grazing is persistent. To do so, we examined seagrass and epiphyte response to field manipulations of nutrients and grazing in Big Lagoon, FL, USA where previous studies were conducted with similar methodologies. Our manipulations were successful in elevating water column and porewater nutrient levels. Nutrient additions caused significant increases in tissue nitrogen contents ( p = 0.01), but they did not affect seagrass or epiphyte biomass, shoot density, or percent cover. Aboveground biomass was significantly reduced in both treatments involving grazing simulations when compared to the fertilizer addition only treatment ( p = 0.001). Fish counts revealed greater numbers of pinfish in fertilized plots compared to all other treatments ( p = 0.000), suggesting the fish were attracted to plots in which fertilization resulted in elevated tissue nitrogen contents. Overall, effects of fertilization and grazing on various seagrass attributes showed both similarities and differences in comparison to other studies from the same and different locations, raising the question about how predictable and informative the responses of individual seagrass characteristics for discerning the relative, long-term influence of these factors on seagrass populations. [ABSTRACT FROM AUTHOR]

The seagrasses Halophila ovalis and Thalassia hemprichii commonly occur in the upper-intertidal zone where they are subjected to prolonged desiccation during low tides. This study investigated their desiccation tolerance and the mechanisms underlying their eventual recovery. Halophila ovalis exhibited a faster decline in photosynthetic efficiency, measured as effective quantum yield of photosystem II (φPSII), during 90 min of desiccation and did not recover when rehydrated. Thalassia hemprichii, however, showed a nearly full recovery. Desiccation also imposed greater membrane damage on H. ovalis as indicated by a higher electrolyte leakage. In a subsequent experiment, seagrasses were desiccated for 60 min before being rehydrated with seawater containing either chloramphenicol (CMP), cycloheximide (CHX), dithiothreitol (DTT) or no metabolic inhibitor (control). Recovery of φPSII of H. ovalis was hindered by CMP and DTT while CHX had little effect. Recovery of φPSII of T. hemprichii, however, was partially affected by both CMP and CHX to a similar extent and not by DTT. The results indicate that H. ovalis relies substantially on the synthesis of chloroplast-encoded proteins and excess energy dissipation by the xanthophyll cycle whereas T. hemprichii requires limited protein synthesis in both chloroplast and cytoplasm to completely recover their photosynthetic function from desiccation stress. [ABSTRACT FROM AUTHOR]

Natural habitats can be described using an array of variables, but metrics that distil these multiple parameters into a single readily comparable value (e.g. a score) can prove useful for spatio-temporal comparisons as well as decisions concerning environmental resource management. In the lagoon of south-western New Caledonia, multiple habitat variables sampled from seagrass meadows were integrated into a single score for comparison of habitat structure across two spatial scales. Collectively, seagrass meadows scored at 69/100, indicating a 'fair-to-good' habitat structure. Spatial variation was evident, however, being greatest at the scale of 'site' (0.5-5 km) relative to 'location' (tens of kilometres). Key metrics of seagrass area, percentage cover and species identity appeared to drive spatial patterns in habitat structure scores. Although the causes of observed site-scale variation in seagrass structure are untested, differences in wave exposure among sites appear a likely contributing factor. Overall, integrated sampling techniques such as that used herein can provide a convenient way to rapidly compare seagrass habitats, and could be useful as early warning indicators of habitat change in regions where anthropogenic impacts that cause seagrass decline (e.g. eutrophication, sediment released from mining) are of concern. [ABSTRACT FROM AUTHOR]

Seagrasses comprise 78 species and are rarely invasive. But the seagrass Halophila stipulacea , firstly recorded in the Caribbean in the year 2002, has spread quickly throughout the region. Previous works have described this species as invasive in the Caribbean, forming dense mats that exclude native seagrass species. During a reconnaissance field survey of Caribbean seagrass meadows at the islands of Bonaire and Sint Maarten in 2013, we observed that this species was only extremely dense at 5 out of 10 studied meadows. Compared to areas with sparse growth of H. stipulacea , these dense meadows showed consistently higher nutrient concentrations, as indicated by higher leaf tissue N contents of the seagrass Thalassia testudinum (dense when C:N < 22.5) and sediments (dense when %N > 11.3). Thus, the potential invasiveness of this non-native seagrass most likely depends on the environmental conditions, especially the nutrient concentrations. [ABSTRACT FROM AUTHOR]

This study was designed to gain more advanced insights about the efficacy of some marine organisms that thrive along the Saudi Arabian red sea coast against the larvae of Aedes aegypti mosquito, the main transmitter of the dengue fever virus in Jeddah Governorate. Ethanolic extracts were prepared from marine organisms of seagrass Thalassia hemprichii and sea cucumber Holothuria atra in addition to the use of a commercial insecticide from a botanical origin Bug Slug as a kind of a positive control comparison. The preparation of the aqueous measuring solutions of the alcoholic crude extracts was conducted in addition to a series of concentrations for testing their efficacy against the 4th larval stage of Ae. aegypti according to the assessment and recommended protocols of the World Health Organization (WHO, 2005). Five replicates for each concentration was prepared with the positive control comparison and the recording of data on the mortality rate was all conducted 24 hours post larval treatment for all the aforementioned series of the concentrations. Our results showed that the percentage mortality of the 4th larval stage of Ae. Aegypti mosquito vector post-treatment with the extracts under investigation was positively correlated with the applied concentrations, however the commercial insecticide Bug Slug have produced the highest efficacy of the larval mortality of the mosquito vector with the LC50 values (the concentration that kills 50% of the larval population) as 0.0287 ppm and the Lower Confident Limit was (LCL = 0.02) and the Upper Confident Limit (UCL = 0.04 ppm) and this was followed by the efficacy of H. atra extract that gave LC50 =188.6 ppm (LCL = 181.9 and UCL = 194.9 ppm) then followed by the efficacy of T. hemprichii extract with LC50 = 201.7 (LCL=181.9 and UCL = 194.9 ppm). Based on the outcome of this investigation it is fair enough to say that the ethanolic extract of the sea cucumber H. atra contains promising constituents as insecticides against the larvae of the mosquito vector of dengue fever followed by the seagrass T. hemprichii. [ABSTRACT FROM AUTHOR]

The article presents strategies to improve the resilience of the world's seagrass meadows. It states the need of more effective management and mitigation across geographical scales to protect seagrass meadows. It notes the need of proper catchment management for improved water quality. It mentions the importance of the maintenance of the key functional biota of the resilient ecosystem.

A circadian rhythm of the dinoflagellate Peridinium quadridentatum was studied at a time-series station in the southwestern Gulf of Mexico, in May 2007. Different substrates (water column, the seagrass Thalassia testudinum , macroalgae, coral rubble and sandy sediment surface) were sampled at the site at 1.5–3.5 m depth. In the samples of coral rubble, P. quadridentatum was scarce. In the water column, the species showed an abundance peak at 15:00. The cell abundance of P. quadridentatum in Thalassia samples increased from 15:00 until 18:00 (1.81 × 10 4 cells/g substrate wet weight), and then continuously decreased until 06:00. Changes in P. quadridentatum cell abundance on macroalgae followed the same trend as on Thalassia , with the maximal value at 18:00. The higher abundance of P. quadridentatum (up to 1.40 × 10 4 cells/g SWW) in macroalgae samples showed the preference for seaweeds. P. quadridentatum has a neritic tropical–boreal distribution. A new combination is proposed: Peridinium quadridentatum var. trispiniferum . [ABSTRACT FROM AUTHOR]

The wide distribution of many seagrasses may be attributable to exploitation of currents. However, many species have seeds heavier than seawater, limiting surface floating, and thus, deep water becomes a potential barrier between suitable habitats. In this investigation, we studied the dispersal potential of various life history stages of two species of seagrasses, Thalassia hemprichii and Halophila ovalis, at Dongsha Atoll and Penghu Islands in Taiwan Strait, west Pacific. The adult plants of both species, often dislodged naturally from substrate by waves, could float, but only that of T. hemprichii could float for months and still remain alive and potentially able to colonize new territories. The seedlings of T. hemprichii could also float for about a month once failing to anchor to substrate of coral sand, but that of H. ovalis could not. The fruits and seeds of T. hemprichii could both float, but for too short a duration to enable long distance travel; those seeds released from long floating fruits had low germination rates in our tests. Obviously, their seeds are not adaptive for long distance dispersal. Fruits and seeds of H. ovalis do not float. The potential of animals as vectors was tested by feeding fruits and seeds of both species to a goose, a duck, and two fish in the laboratory. The fruits and seeds of T. hemprichii were digested and could no longer germinate; those of H. ovalis could pass through the digestive tracts and have a much higher germination rates than uningested controls. Therefore, birds could be important vectors for long distance dispersal of H. ovalis. The two seagrasses adopted very different dispersal mechanisms for long distance travel, and both exploited traits originally adaptive for other purposes. [ABSTRACT FROM AUTHOR]

This study represents the firstin situassessment of seagrasses in the Union of the Comoros. The presence of the following 10 species (ranked in order of abundance) was confirmed:Thalassia hemprichii,Thalassodendron ciliatum,Syringodium isoetifolium,Halodule wrightii,Cymodocea rotundata,Cymodocea serrulata,Halodule uninervis,Halophila ovalis,Zostera capensisandEnhalus acoroides. Seagrasses occurred in large, continuous beds in the shallow waters at the northern and southern tips of Grande Comore Island and around the Bimbini Peninsula on western Anjouan Island, but were sparsely distributed throughout the shallow waters surrounding Mohéli Island. [ABSTRACT FROM AUTHOR]

Se estudio la diversidad y abundancia de la comunidad béntica malacológica asociada a Thalassia testudinum en cuatro localidades de la Bahía de Mochima, Estado Sucre, Venezuela. Las muestras fueron recolectadas mensualmente en cada localidad sobre transeptos perpendiculares a diferentes profundidades (0-4m) desde enero 1991 hasta diciembre 1991, utilizando una cuadrata de 0.25 m² para recolectar los organismos con el sedimento. Un total de 2 988 organismos de la infauna y epifauna, pertenecientes a las clases Gastrópoda (40) y Bivalvia (41) fueron identificados. Las especies más abundantes y en consecuencia mejor adaptadas a los habitats suministrados por la T. testudinum en la Bahía de Mochima fueron Anadara notabilis, Codakia orbicularis, Cerithium litteratum, Cerithium eburneum, Batillaria minima, Modiolus squamosus, Modulus modulus, Chione cancellata, Turritella variegata, Arca zebra, y Laevicardium laevigatum. Se determinaron diferencias significativas en el número de organismos en relación a la profundidad y el tiempo en la localidad de la Gabarra, la cual presentó los valores mas altos de diversidad total (4.51 bits/ind) y mensual (2.75-3.90 bits/ind). La biomasa y la abundancia de moluscos fueron bajas y la estación mas interna (Varadero) presentó los valores mas elevados. El bivalvo A. notabilis y el gastropodo Modulus modulus fueron las especies constantes en las cuatro estaciones.The diversity and abundance of benthic malacological communities associated to Thalassia testudinum beds was studied at four localities of Mochima Bay, Sucre state, Venezuela. At each locality, samples were taken monthly on perpendicular transect at different depths (0-4 m), from January 1991 to December 1991, using a quadrate (0.25 m 2 ) for collecting mollusks and sediments. A total of 2 988 organisms of infauna and epifauna belonging to 81 species of the classes Gastropoda (41) and Bivalvia (40) were collected. More abundant species were Anadara notabilis, Codakia orbicularis, Cerithium litteratum, Cerithium eburneum, Batillaria minima, Modiolus squamosus, Modulus modulus, Chione cancellata, Turritella variegata, Arca zebra, y Laevicardium laevigatum. There were significant differences in number of organisms between depth and month at La Gabarra which presented the highest value of total (4.51 bits/ind) and monthly diversity (2.71-3.90 bits/ind). Biomass and abundance were low in the Mochima Bay while Varadero station presented the highest value. The bivalve A. notabilis and gastropod M. modulus were species common to the four stations.

In order to increase our understanding of the microbial diversity associated with seagrass Thalassia hemprichii in Xincun Bay, South China Sea, 16S rRNA gene was identified by highthrough sequencing method. Bacteria associated with seagrass T. hemprichii belonged to 37 phyla, 99 classes. The diversity of bacteria associated with seagrass was similar among the geographically linked coastal locations of Xincun Bay. Proteobacteria was the dominant bacteria and the α-proteobacteria had adapted to the seagrass ecological niche. As well, α-proteobacteria and Pseudomonadales were associated microflora in seagrass meadows, but the interaction between the bacteria and plant is needed to further research. Burkholderiales and Verrucomicrobiae indicated the influence of the bay from anthropogenic activities. Further, Cyanobacteria could imply the difference of the nutrient conditions in the sites. γ-proteobacteria, Desulfobacterales and Pirellulales played a role in the cycle of sulfur, organic mineralization and meadow ecosystem, respectively. In addition, the less abundance bacteria species have key functions in the seagrass meadows, but there is lack knowledge of the interaction of the seagrass and less abundance bacteria species. Microbial communities can response to surroundings and play key functions in the biochemical cycle. [ABSTRACT FROM AUTHOR]