Seagrass Habitats Research Articles

Effect of temperature on photosynthetic physiology and the kinetics of nutrient absorption in Zostera caespitosa

The ecological fabric of coastal zones is intricately linked to the vitality of seagrass meadows, with Zostera caespitosa serving as a foundational species. Integral to biodiversity conservation and the carbon cycle, these ecosystems are facing unprecedented thermal stress due to global warming. Our research delves into the temperature-dependent physiological responses of Z. caespitosa, focusing on growth rates, photosynthetic activity, and nutrient uptake dynamics across varying thermal regimes. We pinpoint an optimal temperature window of 10–20 °C for these critical physiological processes. These findings not only chart a course for the protective measures of seagrass beds but also furnish pivotal data for predictive models assessing the resilience of these ecosystems under climatic fluctuations. The insights gained offer a strategic advantage for the restoration and stewardship of seagrass habitats, informing climate change mitigation strategies, biodiversity preservation, and the sustained provision of ecosystem services along coastal frontiers. This research, by bridging gaps in our ecological understanding, underscores the imperative of nuanced ecosystem management in an era of changing global temperatures.

Daily, seasonal, and long-distance movements inferred from Fastloc-GPS telemetry of immature green turtles (Chelonia mydas) at a high-latitude, mid-ocean developmental site.

To characterize the movements and habitat use of juvenile green turtles (Chelonia mydas) in benthic developmental habitat, we deployed Fastloc-GPS-enabled satellite transmitters on 16 individuals captured as part of a multi-decade study of green turtles on the Bermuda Platform. We characterized residence areas, distinct use areas within them, and seasonal movements based on an average of 562 Fastloc-GPS positions and 284 tracking days per turtle. We estimated residence area sizes using traditional home range methods, e.g., 90% utilization distribution (UD) (mean 2.29 ±2.71 km2) and 50% UD (mean 0.54 ±0.69 km2). Total residence area size increased significantly over the 8-year study, from <1 km2 before 2013 to ≥3 km2 in 2018 (R2 = 0.51, F1,14 = 14.55, p = 0.0019), corresponding to a period of decline in seagrass habitat and suggesting increased foraging effort. We identified three types of distinct use areas within residence areas where tracked turtles typically exhibited behavioral fidelity: foraging, resting, and cool weather refugia. These distinct use areas were smaller than high-use areas from previous studies; e.g., seagrass meadow foraging areas averaged 0.05 km2. Most turtles made daily transits between foraging and resting sites; for some individuals, these involved crossing frequently used vessel navigation channels. Seasonal variation in behavior suggested that the overwintering strategy for green turtles on the Bermuda Platform involves "optional dormancy," during which turtles spent less time on seagrass meadows and made brief excursions to distinct deeper habitats. Four individuals made directed (mean path straightness = 0.93 ±0.02 SD) developmental migrations away from Bermuda toward known adult foraging range. Results of our study further knowledge of the green turtle life cycle at a high-latitude site; they demonstrate that green turtles show fidelity to distinct use areas within developmental habitats over many years and exhibit seasonal movements.

Substantial seagrass blue carbon pools in the southwestern Baltic Sea include relics of terrestrial peatlands

Seagrass meadows have a disproportionally high organic carbon (Corg) storage potential within their sediments and thus can play a role in climate change mitigation via their conservation and restoration. However, high spatial heterogeneity is observed in Corg, with wide differences seen globally, regionally, and even locally (within a seagrass meadow). Consequently, it is difficult to determine their contributions to the national remaining carbon dioxide (CO2) budget without introducing a large degree of uncertainty. To address this spatial heterogeneity, we sampled 20 locations across the German Baltic Sea to quantify Corg stocks and sources in Zostera marina seagrass-vegetated and adjacent unvegetated sediments. To predict and integrate the Corg inventory in space, we measured the physical (seawater depth, sediment grain size, current velocity at the seafloor, anthropogenic inputs) and biological (seagrass complexity) environment to determine regional and local drivers of Corg variation. Here we show that seagrass meadows in Germany constitute a significant Corg stock, storing on average 1,920 g C/m2, three times greater than meadows from other parts of the Baltic Sea, and three-fold richer than adjacent unvegetated sediments. Stocks were highly heterogenous; they differed widely between (by 22-fold) and even within (by 1.5 to 31-fold) sites. Regionally, Corg was controlled by seagrass complexity, fine sediment fraction, and seawater depth. Autochthonous material contributed to 12% of the total Corg in seagrass-vegetated sediments and the remaining 88% originated from allochthonous sources (phytoplankton and macroalgae). However, relics of terrestrial peatland material, deposited approximately 6,000 years BP during the last deglaciation, was an unexpected and significant source of Corg. Collectively, German seagrasses in the Baltic Sea are preventing 2.01 Mt of future CO2 emissions. Because Corg is dependent on high seagrass complexity, the richness of this pool may be contingent on seagrass habitat health. Disturbance of this Corg stock could act as a source of CO2 emissions. However, the high spatial heterogeneity warrant site-specific investigations to obtain accurate estimates of blue carbon, and a need to consider millennial timescale deposits of Corg beneath seagrass meadows in Germany and potentially other parts of the southwestern Baltic Sea.

Variations in body condition of green turtles (Chelonia mydas) in two nearby foraging grounds indicate their sensitivity to foraging habitats

Abstract Coastal seagrass habitats are critical foraging grounds for endangered green turtles (Chelonia mydas). However, these habitats are vulnerable to anthropogenic effects, potentially leading to their degradation with consequent impacts on the health status of foraging green turtles. Two foraging habitats of green turtles in Tun Mustapha Park, Sabah, Malaysia were surveyed: Kudat Mainland and Balambangan Island, by capturing green turtles and evaluating their physical body condition as well as assessing seagrass cover. Despite having similar genetic compositions, the Kudat Mainland aggregation had significantly higher body size (curved carapace length: 61.7 ± 14.5 cm, body weight: 30.0 ± 22.2 kg), Fulton's body condition index (BCI: 1.49 ± 0.13), barnacle (Chelonibia testudinaria) occurrence (78.8%) and barnacle abundance (5.46 ± 9.90 barnacles/turtle) than the Balambangan Island aggregation (curved carapace length: 51.6 ± 8.1 cm, body weight: 17.3 ± 7.7 kg, BCI: 1.40 ± 0.09, barnacle occurrence: 31.0%, barnacle abundance: 0.50 ± 0.92 barnacles/turtle). The differences in BCI between the nearby aggregations could not be attributed to size and barnacle occurrence differences, suggesting the foraging habitat is the primary factor affecting the body condition of green turtles. Seagrass cover at Kudat Mainland was only slightly higher than at Balambangan Island. These findings suggest that the body condition of green turtles is potentially sensitive to the quality of foraging habitats such as nutrients and water quality. It is crucial to monitor the health of foraging habitats and their impact on the body condition of turtles. It is recommended that habitat‐turtle dynamics are given conservation priority, in parallel to water quality monitoring – with action taken to reduce pollution if necessary. A holistic approach to turtle conservation is therefore required.

Macroinvertebrate assessment in seagrass ecosystem in Sinacaban Municipality, Misamis Occidental, Philippines

Abstract. Mahilac HMO, Tandingan JP, Torres AG, Amparado JRR, Roa-Quiaoit HA. 2023. Macroinvertebrate assessment in seagrass ecosystem in Sinacaban Municipality, Misamis Occidental, Philippines. Biodiversitas 24: 5586-5597. Marine ecosystems such as seagrasses are economically and ecologically important in tropical coastal areas like Sinacaban municipality, southern Philippines. This study assessed the macrobenthic species and water quality (e.g., pH, salinity, temperature, Dissolved Oxygen (DO), and total suspended solids (TSS) in three seagrass areas in the municipality. The study showed the seagrass habitats with 40 macrofaunal species from the classes Gastropoda (27), Bivalvia (11), and Crustacea (2), with Clibanarius longitarsus as the most abundant species (77 individuals or 24% relative abundance). The Strombidae family holds the highest dominance within the Gastropoda class, whereas the Arcidae family is the most dominant within the Bivalvia class. However, there is no dominant family within the Crustacea class. Water quality showed pH at 7, 30 ppt salinity, and 28? within their standard limits, while DO (8 mg/L) and TSS (127 mg/L) exceeded their range. This study recorded eight economic important species and five least concern International Union for Conservation of Nature (IUCN) species. Among the three (3) sites, the seagrass area in Libertad has the highest species richness (28), Shannon’s Index (2.92), and species evenness (0.66). The Chao estimation result revealed that Libertad (37.17) and Poblacion (18.5) have lower uncertainty in their species estimates than Colupan (39.60), which has a wider range of potential species richness. The Canonical Correspondence Analysis (CCA) proved that there are species that can adapt to a certain level of environmental parameters, like Angaria delphinus, while Decatopecten radula is one of the species that does not correlate with the water parameters in the study. The findings are critical for biodiversity conservation, ecosystem management, sustainable resource use, and adaptation to changing environments in order to maintain ecological balance and the long-term health of the seagrass ecosystem.

Seagrass Meadow Distribution Mapping in the Coastal Lagoon of Buan Island, Anambas

Seagrasses are vital monocotyledonous marine flowering plants that serve as essential food sources for megaherbivores, contribute significantly to organic carbon production, and offer a multitude of crucial ecosystem services. Preserving seagrass habitats is of utmost importance, but the lack of comprehensive spatial data poses challenges to conservation efforts. The Anambas Islands, consisting of 255 small islands in the Natuna Sea, the southern part of the South China Sea, exemplify the scarcity of seagrass data, with the current distribution map only covering the Central and East Siantan region. In this study, our aim was to map the Buan coastal lagoon, where previous visual interpretation of Google Earth imagery suggested the presence of seagrasses. To achieve this, we carried out a drone survey and collected field data to classify and map the substrate types in the study area. The field survey documented four species in the location: T. hemprichii, E. acoroides, H. ovalis and S. isoetifolium, thereby expanding the known seagrass species in Anambas to nine. By employing a pixel-based classification of orthophotos, we achieved a promising overall accuracy of 69.5%. Our findings demonstrated that imageries from the Google Earth platform are viable alternatives for identifying seagrass meadows and can be utilized to support seagrass mapping efforts. This discovery offers valuable support for future seagrass mapping initiatives, especially at a local scale. Ultimately, our study contributes to the broader understanding of seagrass distribution in the Anambas Islands, and emphasizes the importance of further exploration to support conservation efforts in the seagrass ecosystem.

Integration of environmental DNA metabarcoding technique to reinforce fish biodiversity assessments in seagrass ecosystems: A case study of Gazi bay seagrass meadows

AbstractAssessing biodiversity in marine nearshore ecosystems is crucial for effective management, especially in the context of climate change and overexploitation of marine resources. Conventional methods often fall short in providing comprehensive information for managing seagrass ecosystems. However, the emergence of environmental DNA (eDNA) techniques has transformed the field by enabling noninvasive surveys that are cost effective and provide detailed information with high resolution. In this study, we utilized eDNA to assess fish diversity and compared its effectiveness to conventional techniques such as catch assessment surveys and underwater surveys. We sampled three habitats (A: mangrove‐seagrass, B: seagrass only, and C: coral‐seagrass) with 4 replicates. Site A recorded 8 fish species, site B had 16 species, and site C, characterized by coral and seagrass habitats, exhibited the highest fish diversity with 45 species (mean H′ index = 2.455), underscoring its ecological importance. To ensure accurate taxonomic identification, we utilized an updated MiFish reference database containing a larger number of fish species compared to the initial library. This expanded reference database with 9569 fish species, facilitated more precise identification and enhanced the reliability of our findings. Notably, the eDNA technique outperformed conventional methods by detecting 23 additional fish species that went undetected using traditional surveys. Moreover, our study documented five fish species previously unknown to occur within the study region, further emphasizing the value of eDNA analysis in uncovering hidden biodiversity. These findings strongly advocate for integrating eDNA techniques into the monitoring and assessment of biodiversity in shallow tropical habitats of the Western Indian Ocean. By leveraging eDNA surveys, we can gain valuable insights into fish diversity, discover hidden species, and make informed decisions for the conservation and management of these ecologically significant areas.

Differences in Bacterial Growth and Mortality between Seagrass Meadows and Adjacent Unvegetated Areas

A seagrass meadow is one of the most important ecosystems around the world, both economically and ecologically. An important feature of this ecosystem is the presence of large coastal seagrass beds, which dominate the primary production and contribute to the secondary productivity of the ecosystem. The microbial loop (consuming bacterial biomass by grazers and using seagrass-derived detritus by bacteria) may be an important mechanism for transferring seagrass-derived organic matter to aquatic food chains. The goal of this study is to gain a better understanding of how bacterial growth and mortality (grazing and viral lysis rates) differ in unvegetated meadow habitats and seagrass habitats. According to this study, DOC levels were higher in seagrass habitats (1685 g L−1) than in unvegetated water surroundings. The instantaneous growth rate of bacteria in seagrass habitats was 2.05 d−1, higher than that of unvegetated water. In a seagrass environment during the summer, we have found that viral lysis and grazing both result in similar mortality rates of bacteria during the summer season. It has been found, however, that bacterial production is controlled by the availability of resources (bottom-up control) in adjacent unvegetated waters, and is thus cycled internally within the bacteria–virus–DOC loop within those waters.

Impact of Coastal Reclamation on Seagrass Habitat in Palu Bay, Central Sulawesi, Indonesia

Coastal development by conducting reclamation for various uses, for example port construction and operations, is a growing threat to coastal ecosystems including seagrass meadows. For several decades, reclamation for coastal development in Palu Bay has included port construction or extension of single-purpose privately owned port facilities as well as public shipping ports. In addition, reclamation was carried out to provide land for the construction of hotels, housing, recreational areas and coastal protection. The majority of private port terminals are owned by mining companies exporting rock and aggregate from around Palu Bay. There are many quarries in the mountains along the western coast of Palu Bay, and alluvial materials around several rivers along the eastern shore are also exploited. The purpose of this study was to analyse the impact of reclamation on seagrass habitat in Palu Bay, especially the private ports, which the dominant reclamation purposes conducted in this area. This study found about 66 ports around Palu Bay, the majority privately owned by mining companies operating in Palu City and Donggala Regency. The effects of reclamation include reduced seagrass habitat and decreased water quality.

Identification of seagrass beds using high-resolution satellite imagery to basic inventory data supporting coastal ecosystem management (Case study: Lancang Island)

Seagrass habitat is an important element of the coastal marine ecosystem, as it influences all major fields in the coastal environments. Due to anthropogenic and natural pressure, such identification of habitat distribution becomes crucial. Remote sensing can provide the best solution regarding time and cost to extract seagrass beds’ spatial and temporal information. When the low spatial resolution satellite image provides low accuracy and high uncertainty of seagrass distribution, we assess the high spatial resolution image product, the WorldView-2 image, to identify the seagrass bed distribution in Lancang Island. We confidently found that higher resolution images could leverage the mapping quality, especially on the seagrass beds, which could be highly sensitive to miss-detection. We can produce 83,75% overall accuracy using pixel-based classification; this is better among other low-resolution images for Instants, Landsat, and Sentinel. Our results suggest that the WorldView-2 image could perform better on seagrass beds identification, yet further improvement on more robust classification methods and algorithms could amplify the mapping and monitoring strategy. Based on this, it can be used as basic data to support future coastal ecosystem management on Lancang Island.

Identifying conservation and restoration priorities for degraded coastal wetland vegetations: Integrating species distribution model and GeoDetector

The ongoing degradation of seagrass and seaweed is of global concern. Comprehending the spatial distribution of these wetland vegetation types and the threats they face becomes critical for effective conservation and restoration efforts. In this study, we combined a species distribution model and geographical detector to propose a novel framework for mapping the distribution and disturbance of degraded coastal wetland vegetation in sparsely recorded areas and identifying conservation and restoration priorities. Guangxi is a province in China known for its extensive coastal wetland vegetation. In our study of Guangxi, habitats suitable for two degraded vegetation types, i.e., seagrass and seaweed, were mapped using the maximum entropy model; 669.44 km2 of seagrass habitat and 929.69 km2 of seaweed habitat were identified. The geographical detector model was used to analyze anthropogenic disturbance caused by four local disturbance factors: shoreline development, fisheries, waterways, and ports and anchorages. Shoreline development was identified as the disturbance factor with the strongest impact on potential habitats of both vegetation types. According to these findings, 48.40 %–64.23 % of the vegetation habitats suffered from high anthropogenic disturbance. Preexisting nature reserves had not effectively protected wetland vegetation from human disturbance. Based on the spatial pattern of vegetation habitat and comprehensive anthropogenic disturbance, conservation and restoration priorities for seagrasses and seaweeds covering an area of 302.26 km2 were further mapped. Our results thus help improve wetland vegetation conservation by providing basic information, and they provide a tool to support site planning for seagrass and seaweed conservation and restoration.

Juvenile sparids (Rhabdosargus holubi) consistently select structurally dense vegetated habitat in nursery seascapes.

Seagrass habitats provide structural complexity in coastal estuarine and marine environments, which offer fish optimal foraging grounds and refuge from predation. However, seagrasses are some of the most threatened ecosystems globally, with anthropogenic activities such as population growth and environmental degradation leading to the fragmentation, thinning, and loss of these habitats. Rhabdosargus holubi is one of only a few vegetation-associated marine fish species in South African estuaries. Although field studies have shown a strong association with seagrass over other aquatic vegetation for the juveniles of this species, habitat choice has never been empirically tested. Here, we used artificial vegetation units to test habitat choice (different structural complexities) for this species. We also tested whether habitat choice is influenced by a predatory threat, with fish preferentially selecting dense habitat in the presence of a predator and whether this effect may be more apparent in smaller individuals. We found that R. holubi significantly prefer greater structural complexity over less complex habitats, in both the absence and presence of a predator and for both small and large juveniles, showing that R. holubi actively choose more complex structures and are attracted to the structure per se irrespective of the threat of predation. This study highlights the importance of dense seagrass as nursery areas for this species and demonstrates how the loss of these habitats could impact the nursery function of estuaries.

Factors influencing the biomass of large-bodied parrotfish species in the absence of fishing on coral reefs in Florida, USA.

Parrotfishes are a functionally critical component of Caribbean reef fish assemblages, with large-bodied parrotfish species exerting particularly important top-down control on macroalgae. Despite their importance, low biomasses of large-bodied parrotfishes on many reefs hamper our ability to study and understand their ecology. Florida reefs, where most parrotfish fishing has been illegal since 1992, present a unique opportunity to explore covariates of their distribution. Using boosted regression tree models and 23 covariates, this study identified the major predictors of four species of Atlantic large-bodied parrotfishes. Maximum hard substrate relief, the area of the surrounding reef, and the availability of seagrass habitat were each positively related to parrotfish presence. Strong positive relationships between parrotfish presence and biomass and the biomass of other parrotfishes on a reef suggest that all four species responded to a similar subset of environmental conditions. However, relationships between parrotfish presence and biomass and depth, habitat type, coral cover, and the proximity of a reef to deepwater habitats differed among species, highlighting distinct habitat preferences. These results can improve managers' ability to target important biophysical correlates of large-bodied parrotfishes with appropriate management interventions and identify areas for protection.

Sea urchin utilisation in Eastern Indonesia

Sea urchins have long been an important component of gleaning invertebrate fisheries and are valued for their highly nutritious gonads. Sea urchin fisheries are often unreported and unregulated, despite increasing indications of overexploitation. Data on the post-harvest utilization of sea urchins are limited, particularly in the Indo-Pacific region. This study at 12 sites across four regions in Indonesia (Sulawesi, Moluccas, Nusa Tenggara, Papua) aimed to provide an overview of sea urchin utilization in eastern Indonesia. Data were collected from July to September 2020 using a questionnaire with a snowballing sampling method. There were 187 respondents (62.6% male and 37.4% female) ranged in age from 3-76 years old, and most had been collecting sea urchins for more than five years. Respondents mostly collected the sea urchins from coral reef or seagrass habitats. Four genera (Tripneustes, Diadema, Echinometra and Echinothrix) were identified. Mean catch ranged from 32 (Makassar) to 169 (Maluku Tengah) individual sea urchin per collection. Most respondents knew local names for sea urchins, especially those they collected. Almost 70% respondents used their catch mainly for home consumption, and only 4.8% respondents mainly selling their catch. Most urchins sold were whole or crudely de-spined, typically fetching IDR 500-1000 each. Additional post-harvest processing before sale included removing the gonads from the test and/or cooking, with a unit price of IDR 5,000-25,000/product. Commonly consumed raw, urchins were sometimes cooked (mostly barbecued). These data indicate a need for efforts towards socio-ecologically appropriate sea urchin conservation and fisheries management to address the widespread indications of increasing exploitation levels and declining sea urchin populations.

Vegetative fragment production as a means of propagule dispersal for tropical seagrass meadows

Background and aimsLong distance dispersal (LDD) contributes to the replenishment and recovery of tropical seagrass habitats exposed to disturbance, such as cyclones and infrastructure development. However, our current knowledge regarding the physical attributes of seagrass fragments that influence LDD predominantly stems from temperate species and regions. The goal of this paper is to measure seagrass fragment density and viability in two tropical species, assessing various factors influencing their distribution. MethodsWe measured the density and viability of floating seagrass fragments for two tropical seagrass species (Zostera muelleri and Halodule uninervis) in two coastal seagrass meadows in the central Great Barrier Reef World Heritage Area, Australia. We assessed the effect of wind speed, wind direction, seagrass growing/senescent season, seagrass meadow density, meadow location and dugong foraging intensity on fragment density. We also measured seagrass fragment structure and fragment viability; i.e., potential to establish into a new plant. Key resultsWe found that seagrass meadow density, season, wind direction and wind speed influenced total fragment density, while season and wind speed influenced the density of viable fragments. Dugong foraging intensity did not influence fragment density. Our results indicate that wave action from winds combined with high seagrass meadow density increases seagrass fragment creation, and that more fragments are produced during the growing than the senescent season. Seagrass fragments classified as viable for Z. muelleri and H. uninervis had significantly more shoots and leaves than non-viable fragments. We collected 0.63 (±0.08 SE) floating viable fragments 100 m−2 in the growing season, and 0.13 (±0.03 SE) viable fragments 100 m−2 in the senescent season. Over a third (38%) of all fragments collected were viable. ConclusionThere is likely to be a large number of viable seagrass fragments available for long distance dispersal. This study's outputs can inform dispersal and connectivity models that are used to direct seagrass ecosystem management and conservation strategies.

Diel fish migration facilitates functional connectivity of coral reef and seagrass habitats via transport of ectoparasites

Connectivity between habitats and ecological communities is a critical component of trophic structure. Coral reef systems include reef, seagrass, and mangrove habitats, and the movement of fishes is a key component of habitat connectivity among them. Fishes that undergo diel migrations between habitats are among the best-studied functional groups. Studies on their role in energetic connectivity between adjacent habitats have not considered the possible contribution of parasites. Some diel-migratory species are both highly susceptible to and disproportionately exploited by gnathiid isopods, temporary, tick-like parasites of marine fishes. By leaving the reef at night, diel-migratory fishes reduce their overall exposure to gnathiids, which are more active at night and more abundant in reef habitat. Here we show that for sites in both the Caribbean and the Great Barrier Reef, gnathiids are attached to diel-migratory fishes at the time they depart reef habitat. Because gnathiids associate temporarily with host fishes, they can be acquired by hosts in one habitat and can become dislodged and deposited in another. Field experiments in the Caribbean show that gnathiids from reef habitat dislodge in seagrass habitat, where they likely remain until their next feeding. Sequencing blood meals from free-living gnathiids in seagrass beds, where they are least abundant, shows that diel-migratory and other transient fishes are the most frequently exploited hosts, confirming that deposition of gnathiids in seagrass is facilitated mainly by migratory hosts. These findings have important implications for trophic, population-genetic, and disease connectivity involving gnathiid isopods and potentially other external parasites.

Sedimentary seagrass carbon stock and sources of organic carbon across contrasting seagrass meadows in Indonesia.

Seagrass meadows are an important component of coastal ecosystems globally, and they capture and store organic carbon in living biomass and sediments. Geographical estimates of blue carbon in seagrass habitats are regionally biased, with limited information from the Indo-Pacific region, including Indonesia. Seagrass extent in Indonesia is declining rapidly, and it has been suggested that marine protected areas (MPAs) are an important instrument to support protection of seagrass ecosystems and their services. Thus, this study is aimed at quantifying and comparing sedimentary carbon stocks and sources of organic carbon from seagrass meadows located in undisturbed areas outside MPA, disturbed areas outside MPA, and within MPA in three small islands in Indonesia. The sediment carbon stocks from this study ranged from 19.81 to 117.49 Mg C ha-1, with the highest stock measured inside MPA (77.15 ± 1.38 Mg C ha-1), followed by undisturbed outside MPA (36.08 Mg C ha-1), and the lowest stock at disturbed outside MPA (21.86 ± 0.31 Mg C ha-1). The predominant source of organic carbon in disturbed meadows was from coastal POM (particulate organic matter, ~ 36%), while in MPA and undisturbed sites, the main source was from seagrass, with ~ 38% and ~ 60% contributions, respectively. The results of this study add more data and information on seagrass blue carbon potential from three different islands with different degrees of disturbance in Indonesia.

ELASTICITY ANALYSIS OF THE GRAZING AND DETRITAL PATHWAYS IN A SHALLOW PHILIPPINE SEAGRASS MEADOW

Ecotrophic efficiency (EE) is an estimate of the proportion of production that is utilized by the next trophic level through direct predation or fishing or exported out of the ecosystem. In seagrass systems, analysis of EE provides crucial information on how biomass, when used or lost in biological functioning, affects the higher trophic levels via death or grazing relative to the energy lost via decomposition (i.e., Flow to the detritus, FTD) and exports to another ecosystem (i.e., Sum of all exports, SAE). In this study, projections on the effect of change in the EE of functional groups in seagrass systems due to the alteration of biomass were established heuristically using Elasticity Analysis. Using a previously constructed Ecopath model for a shallow Philippine seagrass meadow, the simulations of altering the biomass of seagrasses and their grazers were done to determine the change in EE, FTD, and SAE, thereby generating information on the dynamics of the grazing and detrital pathways in the seagrass ecosystem. Results showed the effects of biomass increase and decrease of grazers (herbivorous gastropods, Tripneustes gratilla, and polychaetes). If the grazers’ biomass increases, their EE tends to decrease, and biomass accumulation tends to increase. This implies that a fraction of their production used in the system is reduced even if their predators' density and feeding rate are still constant. In addition, the EE of seagrasses tends to increase, leading to a decrease in biomass accumulation at the primary producers’ trophic level. Lastly, the EE of detritus decreased because the FTD and SAE of its major contributors (the seagrasses) had also decreased. The findings contribute to the ongoing analysis of the role of herbivores versus detritivores in the energetics of seagrass habitats.

Satellite tracking reveals use of Biscayne National Park by sea turtles tagged in multiple locations

Although historical observations date back to the 1800’s, there is little information on sea turtle occupancy within Biscayne National Park (BNP). The park is located along the Florida reef tract and is dominated by the Gulfstream, which acts as a corridor for many marine animals. Here we used satellite telemetry to determine areas of use in BNP for two species of imperiled sea turtles, loggerhead (Caretta caretta) and green (Chelonia mydas) turtles. We included data for turtles tagged between 2009–2021 at sites both within park waters and in five locations outside the park boundary; individuals were captured both in the water and on land. We tagged 60 individuals (female, n = 48; male, n = 3; immature, n = 9); loggerheads (n = 33) ranged in size from 66.2 to 109.9 cm CCL (curved carapace length) and green turtles (n = 27) ranged in size from 39.1 to 111.9 cm CCL. We used behavioral switching state-space modeling (SSM) to obtain daily predicted positions for each turtle, classified turtle behavior within the park as either foraging, migration, or both foraging and migration, and summarized high-use areas for each species across all months of the year. Turtles used park waters year-round, with concentrated use of deeper waters during seasonal migrations. Across all 60 turtles, 21 spent their tracking time foraging within BNP boundaries and 30 used the park as part of their migratory pathway; five turtles used the park for both foraging and migration, and the remaining four had SSM points very close to the park. Loggerhead migration occurred from February through November, whereas green turtle migration was concentrated in August. Both turtle species exhibited high overlap (i.e., usage) with seagrass habitat. These findings are relevant as managers consider strategies to minimize anthropogenic impacts to resident and migratory sea turtles using park waters.

Rampant asexual reproduction and limited dispersal in a mangrove population of the coral Porites divaricata.

Corals are critical to marine biodiversity. Reproduction and dispersal are key to their resilience, but rarely quantified in nature. Exploiting a unique system-a fully censused, longitudinally characterized, semi-isolated population inhabiting mangroves-we used 2bRAD sequencing to demonstrate that rampant asexual reproduction most likely via parthenogenesis and limited dispersal enable the persistence of a natural population of thin-finger coral (Porites divaricata). Unlike previous studies on coral dispersal, knowledge of colony age and location enabled us to identify plausible parent-offspring relationships within multiple clonal lineages and develop tightly constrained estimates of larval dispersal; the best-fitting model indicates dispersal is largely limited to a few metres from parent colonies. Our results explain why this species is adept at colonizing mangroves but suggest limited genetic diversity in mangrove populations and limited connectivity between mangroves and nearby reefs. As P. divaricata is gonochoristic, and parthenogenesis would be restricted to females (whereas fragmentation, which is presumably common in reef and seagrass habitats, is not), mangrove populations likely exhibit skewed sex ratios. These findings suggest that coral reproductive diversity can lead to distinctly different demographic outcomes in different habitats. Thus, coral conservation will require the protection of the entire coral habitat mosaic, and not just reefs.