Seagrass Cover Research Articles

Decade of change in Enhalus acoroides seagrass meadows in Guam, Mariana Islands

Seagrasses provide important ecosystem services, including carbon sequestration. However, there are significant gaps in our estimates of seagrass coverage, particularly in the western tropical Pacific. In the present study we assessed the status and extent of seagrass meadows, dominated by Enhalus acoroides, around Guam, the largest and most populated island in the Marianas. The combined above- and belowground biomass of E. acoroides (~2300g dry weight m–2) is the highest reported for this species and among the highest for all seagrass species. Elemental analysis of C, N and P revealed variations across site and plant part (i.e. above- v. belowground); N:P ratios suggested N limitation. Between 2004 and 2015, seagrass meadows in Guam decreased in total size by 22%, although it is unclear whether this change was part of a long-term trend and whether it was caused by natural or human factors. The high standing stock of E. acoroides suggests that further examination of this species and this region will be needed to better estimate global seagrass carbon stocks.

POTENSI EKOSISTEM PADANG LAMUN DI KAWASAN WISATA BAHARI GUGUSAN PULAU PARI, DKI JAKARTA

Marine Tourism Area at Pari Island cluster has a variety of ecosystems, one of them is the seagrass ecosystem. Seagrass is one of the coastal and marine resources, which has the potential to be developed as a resource for tourist attraction in the marine tourism area of Pari Islands. Purpose this study is to describe seagrass conditions, is it worthed to be used as a tourist attraction by conducting field research of species composition, distribution, percent cover at marine tourism territory Pari Islands, DKI Jakarta. The study was conducted from April-May 2017 with the descriptive method, where this method is done by describing or describe seagrass conditions. Survey and field data acquisition carried out in Pari Islands at 10 stations using the quadrant transect method. Based on field observation, in the field was found 5 species of seagrass species Cymodocea rotundata, Enhalus acoroides, Halophila ovalis, Syringodium isoetifolium and Thalassia hemprichii that can be a potential attraction for marine tourism. The results of calculations percent cover of seagrass shows that the highest percent cover was at station 9 with total percent was 76,2 %, while the lowest percent cover was at station 2, amounting to 20,4 %.
 Keywords: Marine Tourism, Pari Islands, Seagrass Beds

Variability of UK seagrass sediment carbon: Implications for blue carbon estimates and marine conservation management.

Seagrass meadows provide a multitude of ecosystem services, including a capacity to sequester carbon dioxide (CO2) within their sediments. Seagrass research in the UK is lacking and there is no published data on sediment carbon (C) within UK seagrass meadows. We sampled 13 Zostera marina meadows along the southwest coast of the UK to assess the variability in their sedimentary organic carbon (OC) stocks. The study sites were considered representative of sub-tidal Z. marina meadows in the UK, spanning a gradient of sheltered to exposed sites, varying in formation, size and density, but found along the same latitudinal gradient. OC stocks (Cstocks) integrated across 100cm depth profiles were similar among all sites (98.01 ± 2.15 to 140.24 ± 10.27 Mg C ha-1), apart from at Drakes Island, which recorded an unusually high Cstock (380.07 ± 17.51 Mg C ha-1) compared to the rest of the region. The total standing stock of C in the top 100cm of the surveyed seagrass meadows was 66,337 t C, or the equivalent of 10,512 individual UK people’s CO2 emissions per year. This figure is particularly significant relative to the seagrass area, which totalled 549.79 ha. Using estimates of seagrass cover throughout the UK and recent UK C trading values we approximate that the monetary value of the UK’s seagrass standing C stock is between £2.6 million and £5.3 million. The C stock of the UK’s seagrass meadows represent one of the largest documented C stocks within Europe and are, therefore, of important ecosystem service value. The research raises questions concerning the reliability of using global or regional data as a proxy for local seagrass C stock estimates and adds to a growing body of literature that is looking to understand the mechanisms of seagrass C storage. When taken with the fact that seagrass meadows are an important habitat for commercially important and endangered species in the UK, along with their declining health and cover, this research supports the need for more robust conservation strategies for UK seagrass habitats.

Carbon storage variability in seagrass meadows of Marine Poton Bako, East Lombok, West Nusa Tenggara, Indonesia

Rahman FA, Qayim I, Wardiatno Y. 2018. Carbon storage variability in seagrass meadows of Marine Poton Bako, East Lombok, West Nusa Tenggara, Indonesia. Biodiversitas 19: 1626-1631. The increase of atmospheric CO2 concentration in the last decades leads to global warming, having an adverse effect on the environment condition on the Earth. One of the natural mechanism as an effort to reduce the impact of global warming is carbon absorption and storage through photosynthesis mechanism of seagrass vegetation. Research conducted at Poton Bako, a district in East Lombok was aimed to reveal the composition of seagrass species, density, seagrass coverage, the biomass of seagrass tissue, content of carbon storage in seagrass tissue (above and below substrates), carbon content in seagrass sediments, and estimation of carbon stock in the area. The research included observation of species composition, and the sample was collected from 0.5 m × 0.5 m plot area. The total plot area was 36 on six lanes with the space between plots 25 m and between lanes 100 m. Six species from two families were found in the seagrass meadows, i.e., Cymodocea rotundata, Enhalus acoroides, Halophila minor, Holodule uninervis, Thalassia hemprichii and Thalassodendron ciliatum. The three highest total densities were C. rotundata 214.67±110.469 stands m-2, T. hemprichii 85.11±41.471 stands m-2, and H. minor 42.22±44.204 stands m-2. Species with the highest coverage value at all observation plots was C. rotundata (33.47±26.748 %), and T. ciliatum had the lowest value (2.12±5.071 %). The total biomass was 676.32 g DW m-2 with biomass above substrate 329.94±57.725 g DW m-2 and below substrate 654.88±81.199 g DW m-2. The carbon content of substrate ranged from 0.11% to 0.51% with the average of 0.35±0.081%, which was categorized low. The total average of carbon storage in seagrass was 447.92 g C m-2 comprising 142.77 g C m-2 of their tissue above substrate and 305.15 g C m-2 below substrate. Regarding the area, the total carbon stored in seagrass meadows with 56.65 ha area was 249.27 t C ha-1.

Kondisi dan Keanekaragaman Jenis Lamun di Perairan Pulau Serangan, Provinsi Bali

Serangan Island is one of the tourism destinations in Bali which is administratively belong to the municipality of Denpasar. Tourism development near with the segrass habitat cause the segrass ecosystem being degraded in the waters of Serangan Island. This study was aimed to determine the diversity and conditions of seagrass species which were observed from the density and percentage of seagrass coverage and to examine the effect of water quality on the percentage of seagrass coverage. This research was conducted from February to March 2017 on Serangan Island using quantitative descriptive method. Sampling was conducted at three stations by taking data and samples of seagrass, measuring water quality (temperature, salinity, pH, turbidity, substrate observation) and analyze of nitrates and phosphates content. Seven types of seagrass species were found i.e. Enhalus acoroides, Thalassia hemprichii, Cymodocea rotundata, Halophila ovalis, Halodule pinifolia, Syringodium isoetifolium, and Thalassodendron ciliatum. The study showed that the diversity index value was in the medium category. The density of seagrass was classified as very tight (condition scale of 5). The highest density was found on Cymodocea rotundata spesies at station I about 777 ind/m2. The highest percentage of seagrass coverage (79,55%) was found in station I which classified as good condition, while station II and station III were classified as damaged condition with value 13.65% and 20,79% respectively. Finally, the water quality parameters have relatively low effect to seagrass coverage percentage.

Ten years of conservation efforts enhance seagrass cover and carbon storage in Thailand

AbstractSeagrasses are known as engineering ecosystems that play important roles in coastal environments. Globally, seagrass areas have been declining, and many conservation projects have been carried out to prevent further decline. The goal of this work was to determine how successful conservation efforts have been in a seagrass meadow at Koh Tha Rai in the Nakhon Si Thammarat Province of southern Thailand in terms of meadow extent, coverage and organic carbon storage. A study was conducted in 2017 and compared to a previous study from 2006 to determine the effects of the various conservation efforts devoted to this area. The results show that the total seagrass area increased by 0.7 ha with a rate of increase of approximately 0.06 ha year−1. The total coverage of seagrass increased by approximately 3 times. The organic carbon in existing seagrass meadows (2006) was 53.35 Mg ha−1, while growth was 32.34 Mg ha−1in the areas of new seagrass. Moreover, the total organic carbon storage in the sediment increased by 26.86 MgC from 2006 to 2017 (from 211.60 MgC to 235.46 MgC). In conclusion, this study demonstrated the importance of successful conservation efforts in terms of increasing seagrass meadow areas, seagrass coverage and carbon storage within the meadow.

Widespread recovery of seagrass coverage in Southwest Florida (USA): Temporal and spatial trends and management actions responsible for success

In Southwest Florida, a variety of human impacts had caused widespread losses of seagrass coverage from historical conditions. St. Joseph Sound and Clearwater Harbor lost approximately 24 and 51%, respectively, of their seagrass coverage between 1950 and 1999, while Tampa Bay and Sarasota Bay had lost 46% and 15%, respectively, of their seagrass coverage between 1950 and the 1980s. However, over the period of 1999 to 2016, the largest of the six estuaries, Tampa Bay, added 408 ha of seagrass per year, while the remaining five estuaries examined in this paper added approximately 269 ha per year. In total, seagrass coverage in these six estuaries increased 12,171 ha between the 1980s and 2016. Focused resource management plans have held the line on nitrogen loads from non-point sources, allowing seagrass resources to expand in response to reductions in point source loads that have been implemented over the past few decades.

The effects of El Niño-Southern Oscillation events on intertidal seagrass beds over a long-term timescale.

El Niño-Southern Oscillation (ENSO) events can cause dramatic changes in marine communities. However, we know little as to how ENSO events affect tropical seagrass beds over decadal timescales. Therefore, a diverse array of seagrass (Thalassia hemprichii) habitat types were surveyed once every 3months for 16years (January 2001 to February 2017) in a tropical intertidal zone that is regularly affected by both ENSO events and anthropogenic nutrient enrichment. La Niña and El Niño events had distinct effects on the biomass and growth of T.hemprichii. During La Niña years, higher (a) precipitation levels and (b) seawater nitrogen concentrations led to increases in seagrass leaf productivity, canopy height, and biomass. However, the latter simultaneously stimulated the growth of periphyton on seagrass leaves; this led to decreases in seagrass cover and shoot density. More frequent La Niña events could, then, eventually lead to either a decline in intertidal seagrass beds or a shift to another, less drought-resistant seagrass species in those regions already characterized by eutrophication due to local anthropogenic activity.

Satellite‐ and field‐based facies mapping of isolated carbonate platforms from the Kepulauan Seribu Complex, Indonesia

AbstractQuantitative facies models from modern carbonate are essential for the interpretation of their fossil counterparts. The isolated carbonate platforms of the Kepulauan Seribu archipelago has many atoll‐like islands with reef belts exposed to bidirectional monsoon winds. Statistical analysis based on texture and composition reveal that there are four sedimentary facies; coral grainstone, coral packstone/grainstone, coral‐mollusc packstone and mollusc wackestone. The occurrence of mollusc wackestone in the lagoon is controlled by water depth, while the sand apron and reef front do not show significant facies separation with water depth. The co‐occurrence of these different facies in the same depth window is contrary to the common thought that changes in bathymetry should be reflected in facies changes. The studied reef systems therefore show aspects of random and ordered facies distribution with respect to water depth. A satellite derived environmental facies map generated by an image analysis algorithm indicates that environmental facies distribution is mainly controlled by water depth, density of seagrass cover and coral abundance. The sand apron can be subdivided into three environmental facies with no, sparse and dense seagrass cover. The deeper water zone can be separated into shallow and deep subtidal parts of lagoons and platform margins. In the lagoon, satellite derived environmental facies directly correlated with sedimentary facies. No direct correlation of environmental facies to sedimentary facies was possible in the sand apron due to the heterogeneity and complexity of the environment. However, the mean sediment grain size is significantly smaller in areas of the sand apron colonized by dense seagrass. This study aims to contribute towards a better understanding of modern equatorial Southeast Asian carbonate systems, delineate modern carbonate facies based on sediment texture and composition with the aid of multivariate statistical analysis combined with statistic based satellite mapping, and give insights regarding the correlation between depositional facies and water depth.

Local Habitat and Seascape Structure Influence Seagrass Fish Assemblages in the Venice Lagoon: The Importance of Conservation at Multiple Spatial Scales

Seagrass meadows are a critical component of estuarine and coastal seascapes, and their structure influences fish assemblages at multiple spatial scales. The patch mosaic model, which defines the seascape as a collection of interacting habitat types, is increasingly adopted to prioritise protected areas and design ecological restoration schemes, hence helping to preserve seagrass meadows and the associated fish assemblages. Despite that, there are few studies investigating the relative contribution of environmental characteristics measured at different spatial scales in determining the distribution of seagrass fish. This study collects fish and environmental observations taken at both site and seascape scales in seagrass meadows in the Venice lagoon (Adriatic Sea, Italy). By means of generalised linear models, it aims to disentangle the relative influence of local water quality and habitat characteristics from that of habitat mosaic properties, investigating the response of whole fish assemblage descriptors, feeding guilds and dominant species. While confirming the primary importance of local habitat quality, the study highlights that also seagrass habitat structure at the seascape scale is relevant for seagrass fish assemblages, influencing total biomass, biomass of macrobenthivorous and hyperbenthivorous/piscivorous species and seagrass specialists such as syngnathids. Conservation of seagrass fish assemblages can therefore be promoted in Mediterranean coastal lagoons by preserving or restoring some features of the habitat mosaic, namely the extension of seagrass patches and their shape complexity, in addition to local water quality and seagrass cover.

The effect of successive storm events and seagrass coverage on sediment suspension in a coastal lagoon

The effect of a succession of eleven storm events (hourly averaged wind speeds exceeding 10.8 m s−1) on the sediment suspension was investigated in a coastal lagoon through in situ measurements of hydro- and sediment dynamics from a mobile jack-up platform. Results showed that wave-driven bed shear stress (0.1–0.7 N m−2) was the main driver for sediment suspension in contrast to large-scale flushing, which did not trigger sediment suspension. The suspended particulate matter concentration (SPMC) reached a maximum of 200 mg l−1. A meteorologically-driven lagoonal seiche effect was identified, which could be the driver for advective sediment transport in the lagoon. Two major findings for the suspension of sediment can be drawn from the results. First, the energy applied to the bed during successive high-energy storm events caused a reduction in the vegetation cover during a particular strong storm event. This increased the SPMC relative to the bed shear stress, suggesting that the sediment availability increased. Second, successive high-energy storm events decreased the bed shear stress threshold for sediment suspension subsequent to initial consolidation of the bed, suggesting an increase in the bed erodibility. The average bed shear stress threshold for sediment suspension was 0.1 N m−2. Furthermore, successive high-energy storm events increased the SPMC relative to the bed shear stress subsequent to initial consolidation of the bed, before an ultimate decrease. This suggested that the sediment availability subsequent to initial consolidation of the bed increased, but ultimately decreased. The impacts were possibly caused by advective sorting processes during settling of the suspended sediment. The study helps improve numerical modelling of coupled physical and biological environments during successive storm events and thus contributes to advance coastal management of shallow coastal lagoons under a changing climate.

Primary productivity of coastal ecosystems in the Seribu Islands (case study on Kelapa Dua Island, Pramuka Island and Pari Island)

A determination of the primary productivity in coastal ecosystems, namely mangrove, seagrass and coral reef was done in the Seribu Islands (Kelapa Dua Island, Pramuka Island and Pari Island). Data collection was performed by oxygen methods with a light-dark bottle. Data were collected on 11 - 16 February 2016. The data were Mangrove density, seagrass density, seagrass cover, and, coral reefs cover. Physical-chemical parameters of the water were water temperature, salinity, dissolved oxygen, and nutrient content. Mangrove density in Pramuka Island is the highest among the others with density 19,500 trees/ha. The highest seagrass density is found in Kelapa Dua Island of 1,099 stand/m2. Life corals in Kelapa Dua Island has the highest coverage by percentage of 53.2 %. The calculation results of primary productivity values show the highest value in Pulau Kelapa Dua up to 3.0062 gC / m2 / day. The lowest value obtained in Pari Island that was equal to 0.6 gC / m2 / day. Based on research, mangrove density, seagrass density and life corals coverage have a positive correlation to primary productivity.

The Ability of Lyzenga’s Algorithm for Seagrass Mapping using Sentinel-2A Imagery on Small Island, Spermonde Archipelago, Indonesia

The existence of the value of depth variation in the study area is also a requirement in the application of this algorithm. The purpose of this study is to determine the ability of the use of algorithms in the mapping of seagrass by comparing the results of classification between imagery using the Lyzenga’s algorithm with imagery without using the Lyzenga’s algorithm. The result of imagery classification applying the Lyzenga’s algorithm shows the visibility of baseline water objects that are more easily recognizable using Depth Invariant Index (DII) value format as evidenced by the increase of 2 classes of seagrass cover. In this study there are five seagrass cover classes of shallow water in Pajenekang Island, Spermonde-Indonesia Islands using Lyzenga’s algorithm, namely class are 1) Very good: > 75%; 2) Good: 50,575,4%; 3) Rather Good: 25,5-50,4%; 4) Bad: 5,5-25,4%; and 5) Very Bad: <5.5%.

Time‐integrated habitat availability is a resource attribute that informs patterns of use in intertidal areas

AbstractIn dynamic environments, resource availability may change by several orders of magnitude, over hours to months, but the duration of resource availability is not often included as a characteristic attribute of resources even though temporal resource dynamics might limit patterns of use. In our study of wading birds foraging in intertidal areas, tides cause large changes in the areal extent of shallow‐water foraging habitat (i.e., the resource), but tides also constrain the duration of availability, which is often overlooked. We hypothesized that temporal constraints on habitat availability from tides would be reflected in patterns of habitat use by foraging birds. We estimated the time‐integrated habitat availability and compared it to traditional habitat attributes (seagrass cover, substrate type, instantaneous water depth, and proximity to mangrove islands or deep water) that have strong evidential support for influencing patterns of use. To evaluate our hypotheses, we quantified habitat attributes at intertidal areas in the Florida Keys, USA, where wading birds were observed foraging (Little Blue Heron, Egretta caerulea: N = 183; Great White Heron, Ardea herodias occidentalis: N = 162). We tested for nonrandom use by sampling habitat attributes at two spatial scales around the observed feeding locations and we analyzed the data using a conditional logistic regression model. There was no evidence that seagrass cover or substrate explained patterns of use. The proximity of foraging locations relative to mangroves and to deep water were important at both spatial scales but had lower effect sizes (odds ratios) than time‐integrated habitat availability and water depth, and the latter may only serve as a physical constraint on access. We found support that time‐integrated habitat availability was a distinct resource attribute, had the greatest effect size (four‐ to eightfold change in relative probability of use), and best explained patterns of habitat use at the largest spatial scale. In studies of resource use where changes in resource availability are nonlinear or when strong constraints on access are imposed by behavior, incorporating time‐integrated estimates of resource availability into analyses can improve insights into spatiotemporal patterns of resource use.

Multivariate Analysis of Water Quality and Benthic Macrophyte Communities in Florida Bay, USA Reveals Hurricane Effects and Susceptibility to Seagrass Die-Off.

Seagrass communities, dominated by Thalassia testudinum, form the principal benthic ecosystem within Florida Bay, Florida USA. The bay has had several large-scale seagrass die-offs in recent decades associated with drought and hypersaline conditions. In addition, three category-5 hurricanes passed in close proximity to the bay during the fall of 2005. This study investigated temporal and spatial trends in macrophyte abundance and water quality from 2006 to 2013 at 15 permanent transect sites, which were co-located with long-term water quality stations. Relationships, by year and by transect location (basin), between antecedent water quality (mean, minimum and maximum for a 6-month period) and benthic macrophyte communities were examined using multivariate analyses. Total phosphorus, salinity, pH, turbidity, dissolved inorganic nitrogen (DIN), DIN to phosphate ratio (DIN:), chlorophyll a, and dissolved oxygen correlated with temporal and spatial variations in the macrophyte communities. Temporal analysis (MDS and LINKTREE) indicated that the fall 2005 hurricanes affected both water quality and macrophyte communities for approximately a 2-year period. Spatial analysis revealed that five basins, which subsequently exhibited a major seagrass die-off during summer 2015, significantly differed from the other ten basins in macrophyte community structure and water quality more than 2 years before this die-off event. High total phosphorus, high pH, low DIN, and low DIN:, in combination with deep sediments and high seagrass cover were characteristic of sites that subsequently exhibited severe die-off. Our results indicate basins with more mixed seagrass communities and higher macroalgae abundance are less susceptible to die-off, which is consistent with the management goals of promoting more heterogeneous benthic macrophyte communities.

The use of remote sensing to estimate changes of seagrass extent and biomass in Cockburn Sound, Western Australia

The extent of seagrasses in Cockburn Sound was examined using Nearmap images of year 2010, 2012, 2014, and 2016 to be compared to the last assessment in 1999. It was identified that the seagrass coverage has increased by 231 Ha since 1999, with most of the growth occurred in the southern part. While the water quality in Cockburn Sound has improved, it is believed that there are other pressures affecting the slow growth rate of the seagrasses. Seagrass biomass was also evaluated using Landsat images of year 1994, 1999, 2010, 2012, 2014, and 2016 in addition to a field survey data of leaf biomass in 2016. Despite its increasing extent, seagrass in Cockburn Sound indicated a declining biomass since 1994, which is believed due to the changing nutrient content.

Side scan sonar: A cost-efficient alternative method for measuring seagrass cover in shallow environments

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.

Essential ocean variables for global sustained observations of biodiversity and ecosystem changes.

Sustained observations of marine biodiversity and ecosystems focused on specific conservation and management problems are needed around the world to effectively mitigate or manage changes resulting from anthropogenic pressures. These observations, while complex and expensive, are required by the international scientific, governance and policy communities to provide baselines against which the effects of human pressures and climate change may be measured and reported, and resources allocated to implement solutions. To identify biological and ecological essential ocean variables (EOVs) for implementation within a global ocean observing system that is relevant for science, informs society, and technologically feasible, we used a driver-pressure-state-impact-response (DPSIR) model. We (1) examined relevant international agreements to identify societal drivers and pressures on marine resources and ecosystems, (2) evaluated the temporal and spatial scales of variables measured by 100+ observing programs, and (3) analysed the impact and scalability of these variables and how they contribute to address societal and scientific issues. EOVs were related to the status of ecosystem components (phytoplankton and zooplankton biomass and diversity, and abundance and distribution of fish, marine turtles, birds and mammals), and to the extent and health of ecosystems (cover and composition of hard coral, seagrass, mangrove and macroalgal canopy). Benthic invertebrate abundance and distribution and microbe diversity and biomass were identified as emerging EOVs to be developed based on emerging requirements and new technologies. The temporal scale at which any shifts in biological systems will be detected will vary across the EOVs, the properties being monitored and the length of the existing time-series. Global implementation to deliver useful products will require collaboration of the scientific and policy sectors and a significant commitment to improve human and infrastructure capacity across the globe, including the development of new, more automated observing technologies, and encouraging the application of international standards and best practices.

Seagrass distribution changes in Swan Lake of Shandong Peninsula from 1979 to 2009 inferred from satellite remote sensing data

Seagrass and associated bio-resources are very important for swan’s overwintering in Swan Lake in Rongchengof Shandong Peninsula of China. The seagrass distribution changes, which are usually affected by the regional humanactivities, can indirectly affect swan’s habitat. In this study the satellite remote sensing data in years 1979–2009 togetherwith in-situ observations in recent years were used to examine the seagrass distribution changes in Swan Lake. The bandratio of band 1 to band 2, Lyzenga’s methods and band synthesize of band 1, band 2 and band 3 were used for seagrassretrieval. The band ratio of band 1 to band 2 with ranges greater than 4.5 was used for estimating the seagrass coveragegreater than 50%. Results showed that in years 1979–1990 seagrass coverage greater than 50% occupied more than half ofthe surface area of Swan Lake. In years 2000–2005, the total area with seagrass distributions reduced greatly, only aboutone sixth to one fourth of Swan Lake’s surface area. After 2005, the seagrass area in Swan Lake increased gradually andoccasionally was greater than one third of the total surface area of the Lake. It was shown that human activities such as thedam and fish pond establishment and the awareness of seagrass importance and protected actively result in the seagrassdistributions changes in Swan Lake which decreased first and then increased afterwards.

Komposisi Jenis Lamun (Seagrass) Di Kawasan Pantai Malagoso Desa Dumolodo Kecamatan Gentuma Raya Kabupaten Gorontalo

This research aims to identificated the composition of the type and seagrass beds density in malagoso beach, Dulomodo Village. The data was undetaken by survei method and transect square method. There are 3 stations where every stations will cut in 3 times. The analysis used and covering identification of the type of seagrass beds, density, coverage of seagrass and the closure of the parameters of the enviroment. The results of identification to research is found 4 types species of seagrass, there is Enhalus acoroides, Cymodocea serurulata, Halophila ovalis, Syringodium isoetifolium. Seagrass beds density ranged from 20 tegakan/m -600 tegakan/m. The parameter of water quality there are temperature 200C, salinity31 ppt, pH 8,2, brightess about 0,2-1 meters, the substrates are muddy and rocky.Keywords : Seagrass density, The seagrass bed, Malagoso beach.