A spatial analysis of seagrass habitat and community diversity in the Great Barrier Reef World Heritage Area

The Great Barrier Reef World Heritage Area (GBRWHA) in north eastern Australia spans 2500 km of coastline and covers an area of ~ 350,000 km2. It includes one of the world’s largest seagrass resources. To provide a foundation to monitor, establish trends and manage the protection of seagrass meadows in the GBRWHA we quantified potential seagrass community extent using six random forest models that include environmental data and seagrass sampling history. We identified 88,331 km2 of potential seagrass habitat in intertidal and subtidal areas: 1111 km2 in estuaries, 16,276 km2 in coastal areas, and 70,934 km2 in reef areas. Thirty-six seagrass community types were defined by species assemblages within these habitat types using multivariate regression tree models. We show that the structure, location and distribution of the seagrass communities is the result of complex environmental interactions. These environmental conditions include depth, tidal exposure, latitude, current speed, benthic light, proportion of mud in the sediment, water type, water temperature, salinity, and wind speed. Our analysis will underpin spatial planning, can be used in the design of monitoring programs to represent the diversity of seagrass communities and will facilitate our understanding of environmental risk to these habitats.

KOMUNITAS LAMUN DI PERAIRAN PANTAI DESA ORI, MALUKU TENGAH

Seagrass communities play an important role in marine environments and estuary area, supporting communities of fish, snails and shellfish and other invertebrates. The diversity of seagrass species in the world is very low (<60 species). The coastal waters of Ori Village have a seagrass community that has never been studied. The purpose of this study was to estimate the structure of the seagrass community in the coastal waters of Ori Village, Central Maluku which includes the composition of type, density, frequency of occurence and percent of coverage. Seagrass sampling uses the line transect method. Five species of seagrass were found during the study grouped into two families: Cymodoceaceae and Hydrocharitaceae. The seagrass species found were Cymodocea rotundata, Halodule pinifolia, Enhalus acoroides Halophila ovalis and Thalassia hemprichii. T. hemprichii and E. acoroides have the highest densities (157 shoots/m2 and 137 shoots/m2, respectively). E. acoroides and T. hemprichii also have the highest frequency of occurence and relative coverage percent compared to other seagrass species found in the waters of Ori Village. Seagrass community in the waters of Ori Village is classified in a tight condition until dense. ABSTRAK Komunitas lamun memegang peranan penting di lingkungan laut dan daerah estuari, menyokong komunitas ikan, siput dan kerang-kerangan serta invertebrata lainnya. Keragaman spesies lamun di dunia sangat rendah (<60 spesies). Perairan pantai Desa Ori memiliki komunitas lamun yang belum pernah diteliti. Tujuan dari penelitian ini adalah untuk mengestimasi struktur komunitas lamun di perairan pantai Desa Ori, Maluku Tengah yang meliputi komposisi jenis, kerapatan, frekuensi kehadiran dan persen penutupan. Pengambilan sampel lamun menggunakan metode transek garis. Lima spesies lamun ditemukan selama penelitian yang dikelompokan dalam dua famili yaitu famili Cymodoceaceae dan Hydrocharitaceae. Spesies-spesies lamun yang ditemukan adalah Cymodocea rotundata, Halodule pinifolia, Enhalus acoroides Halophila ovalis danThalassia hemprichii. T. hemprichii dan E. acoroides memiliki kerapatan tertinggi (masing-masing 157 tegakan/m2 dan 137 tegakan/m2). E. acoroides dan T. hemprichii juga memiliki frekuensi kehadiran serta persen penutupan relatif tertinggi dibanding spesies-spesies lamun lainnya yang ditemukan di perairan Desa Ori. Komunitas lamun di perairan Desa Ori tergolong dalam kondisi rapat sampai padat. Kata Kunci: Lamun, komunitas, kerapatan, penutupan, Maluku Tengah

Structure of Seagrass Community in the Karapyak Beach, Pangandaran Regency, West Java

Karapyak Beach is one of the beaches that has a variety of abundant marine ecosystems. One of the marine ecosystems is seagrass. This study aims to identify the structure of seagrass communities in Karapyak waters based on seagrass species, species density, species frequency, diversity, and uniformity. This research was conducted in February – April 2021. The method used is a survey method with direct observation at each predetermined station using a square transect measuring 1 x 1 m2. While the determination of stations and observation points is done by purposive sampling method. The research location is divided into three stations, each station is divided into five substations (plots), and a 50 m transect line is made perpendicular to the shoreline. Furthermore, the results showed four types of seagrass found in the waters of Karapyak Beach, namely Cymodocea rotundata, Thalassia hemprichii, Halodule pinifolia, Halodule uninervis. The density of seagrass at station I was in the medium category, namely 125 individuals/m2, with a cover percentage of 86%. Then the lowest seagrass density was found at the second station, which was 104 individuals/m2 including the unhealthy category with a cover percentage of 58%. While the highest density score was shown at the third station, namely 144 individuals/m2 with a closing percentage of 94%.

Seagrass contribution to blue carbon in a shallow karstic coastal area of the Gulf of Mexico

Seagrass meadows provide multiple ecosystem services, including carbon sequestration. However, seagrass meadows are among the most threatened ecosystems worldwide. Determining the magnitude of the carbon stocks in seagrass meadows at the regional scale allows for the estimation of their global magnitude and identification of their importance in regional environmental mitigation strategies. The objective of the present study was to determine the structure of seagrass meadows in the Los Petenes Biosfera Reserve (LPBR) and evaluate their contributions to sinks of carbon in this system, located in Yucatan, which is considered the region with the largest seagrass extension in Mexico. Analyses of the seagrass meadows were executed following standardized protocols (spectral analysis, and isotope and carbon stock analyses). The LPBR stores an average of 2.2 ± 1.7 Mg C ha−1 in living biomass and 318 ± 215 Mg C ha−1 in sediment (top 1 m), and this carbon stock decreases with water depth. The seagrass community extends 149,613 ha, which represents the largest organic carbon stock (47 Tg C) documented in seagrass meadows in Mexico. Macroalgae and seagrass represent 76% of the organic carbon stored in sediment. If LPBR seagrass meadows are lost due to natural or anthropogenic impacts, 173 Tg CO2eqemissions could be released, which corresponds to the emissions generated by fossil fuel combustion of 27% of the current Mexican population. This information emphasizes the importance of seagrass meadows as a carbon sink in the region and their contribution to climate change mitigation, thus allowing for the implementation of necessary conservation strategies.

Struktur Komunitas Padang Lamun Di Perairan Gili Air, Lombok Utara

Seagrass is a coastal ecosystem that has important role as a feeding ground, a spawning ground and a nursery ground for various marine biota. This study aims to examine the biodiversity of seagrass at Gili Air, North Lombok Regency, West Nusa Tenggara. This study was conducted to observe the cover percentage of seagrass, it's composition, the number of seagrass stands, canopy's height, frequency of seagrass presence, and index of importance of seagrass. Seagrass data was collected using a 50cm x 50cm quadrant transect, with a total area of 100 m2, referring to the monitoring standards set by SeagrassNet. Water quality analysis was carried out at the Bioecology Laboratory of the Aquaculture Study Program, University of Mataram, and at the Laboratory of the Marine Aquaculture Center (BPBL) of Sekotong, West Lombok. The results showed that the seagrass communities in Gili Air waters were composed of 5 (five) species: Halophila ovalis, Thalassia hemperichii, Cymodocea rotundata, Halodulea pinifolia, and Halodule uninervis, with the percentage of coverage ranging from 26.88-39.17%, and the average coverage by 31.53%. Thalassia hemperichii is the species that has the highest contribution to the seagrass community at Gili Air.

Community Structure of Seagrass Field in Litoral Zone of Leweung Sancang Garut Nature Reserve

Seagrass meadows or seagrass beds are one of the important components in coastal ecosystems. Seagrasses provide ecosystem services for various biota that live in it as well as components of the surrounding coastal ecosystems. The Sancang Nature Reserve is one of the coastal areas that has seagrass communities, and seagrass observation data is needed for reference to conservation strategies. This study aims to determine the condition of the cover and the structure of the seagrass community that fills the littoral zone of the Sancang Nature Reserve using the quadratic transect method, which was conducted from March 17 – 21, 2021. The data collected were seagrass species, species frequency, species cover and total cover, and the importance value index of species. Observations were made at 3 stations with an area of 100 m2 each along Ciporeang Beach, at each station 30 square transects with a size of 50 cm were placed, with 1 square transect divided into 25 grids measuring 10 cm. As well as the observation of environmental physical and chemical indicators. The results showed that the seagrass community in the research sites were overgrown by species Cymodocea rotundata and Thalassia hempricii which had a cover condition in the rich category with a percentage of 61.09%. Species densities were 117 i/m and 679 i/m, species closures were 36.95% and 25.63%, and the importance value index of species were 1.49 and 0.54. The difference was significantly influenced by physical indicators such as substrate structure and current velocity, while the chemical indicators at each station did not show a significant difference. Nutrient content data in the substrate at each station is needed to get more detailed conclusions about the factors that affect seagrass cover on the Sancang coast.

Bioekologi Lamun di Perairan Teluk Awur, Jepara, Jawa Tengah

Padang lamun merupakan ekosistem pesisir dan laut yang memiliki peran, fungsi, dan manfaat besar bagi kelangsungan hidup berbagai organisme laut. Tujuan dilakukannya penelitian ini adalah untuk mengetahui kondisi terbaru dari kondisi kesehatan serta kondisi ekologi ekosistem lamun yang terdapat di lokasi penelitian. Penelitian dilakukan di Perairan Teluk Awur, Jepara, Jawa Tengah. Metode penelitian yang digunakan adalah analisis deskriptif. Hasil penelitian menemukan 4 jenis lamun yang tersebar cukup merata pada 3 stasiun penelitian, yaitu: Enhalus acoroides, Thalasia hemprichii, Cymodocea serulata, dan Cymodocea rotundata. Kisaran persentase penutupan rata-rata antara 12,50% – 14,96%. Kerapatan lamun berkisar antara 164,40 – 196,52 ind/m2 dengan komposisi dan kerapatan jenis tertinggi adalah Thalasia hemprichii dan terendah adalah Cymodocea rotundata. Jenis substrat yang ditemukan di ketiga stasiun penelitian adalah substrat pasir dan pasir berlumpur. Nilai indeks ekologi lamun meliputi indeks dominansi masuk kategori rendah, keanekaragaman masuk kategori sedang, dan indeks keseragaman masuk kategori stabil. Hasil ini menunjukan bahwa secara ekologi tidak terdapat spesies yang sangat mendominasi dalam komunitas lamun di Perairan Teluk Awur, Jepara. Kondisi perairan meliputi suhu, salinitas, DO, pH, kecerahan, arus, kadar nitrat, kadar fosfat dan kadar bahan organik masih dikategorikan baik dan cocok bagi pertumbuhan lamun. Berdasarkan kriteria status kondisi padang lamun (Kepmen LH No 200 Tahun 2004), status ekosistem lamun di Perairan Teluk Awur, Jepara adalah kurang kaya/kurang sehat. Secara keseluruhan kondisi ekosistem lamun berserta kondisi ekologinya masih dapat mendukung pertumbuhan lamun. Segrass beds are coastal and marine ecosystems that have a major roles, functions, and benefits for the survival of various marine organism.The purpose of this study was to determine the latest health and ecological conditions of the seagrass ecosystem in the research location. This research was conducted in the waters of Teluk Awur, Jepara, Central Java. The research method used is descriptive analysis. The results of the study found 4 types of seagrass that were spread fairly evenly at 3 research stations, namely: Enhalus acoroides, Thalasia hemprichii, Cymodocea serulata, and Cymodocea rotundata. The range of the average coverage percentage is between 12,50% – 14,96%. Seagrass density ranges from 164,40 – 196,52 ind/m2 with the highest composition, and species density was Thalasia hemprichii and the lowest was Cymodocea rotundata. The types of substrates found in three research stations were sand and muddy sand. The ecological index value of seagrass includes the dominance index which is categorized as a low, the diversity is in the medium category, and the uniformity index is in the stable category. These results indicate that ecologically there are no species that dominate the seagrass community in the waters of Teluk Awur, Jepara. Water conditions, including temperature, salinity, DO, pH, water brightness, current, nitrate content, phosphate content, and organic matter levels are still categories as good and suitable for seagrass growth. Based on the criteria for the status of seagrass beds (Kepmen LH No 200 of 2004), the status of the seagrass ecosystem in the waters of Teluk Awur, Jepara is less rich / less healthy. Overall, the condition of the seagrass ecosystem along with its ecological conditions still supports the growth of seagrass.

Mediterranean seagrasses as carbon sinks: Methodological and regional differences

The increasing rates of CO2 due to anthropogenic activities are causing important potential climate threats for the Mediterranean Sea: ocean acidification and warming. In this region, two seagrass species, Posidonia oceanica and Cymodocea nodosa can play a crucial role in climate change mitigation. Through their metabolic activity, they can act as carbon sinks; buffer lowering pH values during the day and store carbon in the sediment underneath their meadows. In this study we analyse the metabolism synthesized from published data on seagrass community metabolism and from own results to evaluate trends through time of these two species comparing two methodologies: benthic chambers and multiparametric sensors. Furthermore, we analysed seasonal trends of both seagrass species´ metabolic rates and their variation between the Eastern and Western Mediterranean basins, with no significant results despite the clear visual trends. Our analysis revealed that there are significant differences between methodologies, with multiparametric sensors estimating higher rates, but unable to differentiate between habitats and useful to assess seagrass metabolism at a community level whereas benthic chambers are capable to evaluate rates at a seagrass species level. We found significant differences between the two Mediterranean regions for both methodologies, with highest rates of Net Community Production found in the Easter basin. At a species level, we found that Posidonia was more productive compared to Cymodocea. Furthermore, 86.7 % of the metabolic values reflected that the meadows were acting as carbon sinks in the Western basin.

Natural recovery of a marine foundation species emerges decades after landscape-scale mortality

Globally, the conditions and time scales underlying coastal ecosystem recovery following disturbance remain poorly understood, and post-disturbance examples of resilience based on long-term studies are particularly rare. Here, we documented the recovery of a marine foundation species (turtlegrass) following a hypersalinity-associated die-off in Florida Bay, USA, one of the most spatially extensive mortality events for seagrass ecosystems on record. Based upon annual sampling over two decades, foundation species recovery across the landscape was demonstrated by two ecosystem responses: the range of turtlegrass biomass met or exceeded levels present prior to the die-off, and turtlegrass regained dominance of seagrass community structure. Unlike reports for most marine taxa, recovery followed without human intervention or reduction to anthropogenic impacts. Our long-term study revealed previously uncharted resilience in subtropical seagrass landscapes but warns that future persistence of the foundation species in this iconic ecosystem will depend upon the frequency and severity of drought-associated perturbation.