Mangrove Stands Research Articles

Sustainable forest management through natural mangrove regeneration on Pannikiang Island, South Sulawesi

Sustainable management of mangrove forests is determined by the ability of the forest to regenerate naturally. This study aims to determine the potential of natural stands and regeneration of mangrove forests on Pannikiang Island, Barru Regency. Determination of sample plots was done by Purposive Line Sampling plot technique. All plants in the observation transect were identified and classified based on the growth phase, namely seedlings, saplings, poles, and trees. The results showed that there were 20 species, consisting of 8 true mangroves, 5 supporting mangroves, and 7 species of mangrove associations. The estimated total volume of mangrove stands in the Pannikiang island area was 23,624.71 ≤ 39,679.45 ≤ 55,734.19 m³. The potential for natural regeneration of mangrove species on Pannikiang Island is determined by the highest Importance Value Index (IVI) from seedling to tree level. Mangrove natural regeneration with the highest IVI at all tree growth rates was dominated by the species of Brugueira gymnorhiza, Rhizophora mucronata, Sonneratia alba, and Rhizophora stylosa. These species can guarantee the survival of natural regeneration for mangrove communities on Pannikiang Island, while other species require intervention through artificial regeneration.

Pengujian dan Penentuan Spesies Gastropoda sebagai Bioindikator di Kawasan Reboisasi Mangrove Kepulauan Seribu, Indonesia

The development of coastal zones throughout the world has resulted in changes in the order of the mangrove ecosystem, therefore, planting activities are carried out in various regions. The study of the testing and determination of gastropod species as bioindicators in the mangrove reforestation area was carried out in the Seribu Islands. This research aims to determine how suitable the gastropod species are used as bioindicators in assessing the success of mangrove reforestation, especially in the Seribu Islands. Collection of gastropod species is done by making line transects and plots drawn from the reference point (outermost mangrove stands) and perpendicular to the coastline to the mainland. Line transects are made of plots of size 10 x 10 m and in the size of 10 x 10 m a small plot of 1 x 1 m is made. Furthermore, testing is carried out with several criteria and analyzed using multivariate Principal Component Analysis (PCA) statistics. The results of the study show that the species Littoraria scabra has met all the specified testing criteria. Then L. scabra also has the highest eigenvalue compared to the other species, making it suitable to be used as a bioindicator species in assessing the success of the Seribu Islands mangrove reforestation.

Mangroves alter predator-prey interactions by enhancing prey refuge value in a mangrove-marsh ecotone

Black mangroves (Avicennia germinans) are becoming more common along the edges of their range, potentially displacing salt marsh vegetation in transition zones such as the Texas coast in the Gulf of Mexico (USA). Consequences of this shift on trophic interactions within wetland ecosystems are largely unknown. We investigated how increasing mangrove cover might alter predator-prey interactions involving an important consumer in coastal wetlands, blue crabs (Callinectes sapidus), and one of their key prey items, penaeid shrimp (Family Penaeidae). We conducted a series of mesocosm experiments to assess predation rates and prey refuge values in artificial vegetation (AV) matrices simulating flexible marsh grasses (e.g., Spartina patens, Distichlis spicata) and rigid mangrove pneumatophores (aerial root structures). In predation experiments within each of these AV matrices, blue crabs captured 50% fewer penaeid shrimp in the rigid mangrove treatment compared to the flexible marsh treatment, and time between captures was 83% longer among the simulated pneumatophores. In a prey refuge experiment that allowed both predator and prey to move freely among the AV matrices, penaeid shrimp occupied the rigid pneumatophore matrix 30% more often than the grass matrix when blue crabs were present but had no preference when the predator was absent. This study suggests that where A. germinans and marsh grasses co-occur, the mangroves may provide superior refuge for prey items such as penaeid shrimp. Pneumatophores will likely restrict the mobility of predators such as blue crabs, resulting in lower predation efficiency. These results suggest that as mangrove stands continue to increase in cover within mangrove-marsh ecotones, there are likely to be consequences for upper trophic level dynamics.

How to restore mangroves for greenbelt creation along eroding coasts with abandoned aquaculture ponds

Globally, erosion of muddy tropical coasts that are dominated by aquaculture ponds, is an increasing problem. Restoration of mangrove greenbelts may counteract such erosion, by restoring the sediment balance. Hence, we aim to unravel the processes controlling natural mangrove regeneration in both “landward” (i.e., into aquaculture ponds) and seaward direction, using the fast eroding coastline of Demak (Indonesia) as case study. Firstly, we investigated which physical and chemical factors drive landward mangrove expansion by relating them to the presence/absence of mangrove seedlings in abandoned aquaculture ponds. Secondly, we investigated which physical parameters control seaward mangrove expansion by relating them to expansion and retreat at the sea-side of mature mangrove stands.Landward mangrove expansion into abandoned aquaculture ponds was positively related to both emergence time (%) and sediment stability (i.e., shear strength), which are in turn both associated to bed level elevation and pond drainage. Surprisingly, there was no effect of soil chemistry. Seaward expansion of existing mangrove stands was strongly associated to foreshore morphology. Mangroves only expanded in the presence of an elevated mudflat, whereas the absence of a mudflat in combination with a concave (hollow) profile was associated with mangrove retreat. Our findings suggest that restoration of a mangrove greenbelt can be stimulated landward by improving drainage of abandoned aquaculture ponds. This enhances sediment stability and allows ponds to accrete. Seaward expansion can be induced by restoring foreshore morphology. Present results are discussed in the context of large-scale applications.

Relationship analysis of vegetation structural properties and the aboveground carbon stock of mangrove forest

Mangrove forests have important ecological functions as a controller of environmental quality in coastal areas and absorber of atmospheric carbon. The mangrove ecosystem has a unique vegetation structure which form vegetation zonation that consists of different forest stands characteristics and tree species. This study aims to analyze the relationship between vegetation structural properties and the estimated aboveground carbon (AGC) stock of mangrove forest in Bedul mangrove, Banyuwangi, East Java, Indonesia. The study was conducted by field observation at some purposively selected sample locations. Field measurement was aimed to collect data about mangrove tree diameter at breast height (DBH), species, tree height, and fractional canopy cover. Mangrove biomass was indirectly calculated by allometric method based on mangrove species to estimate AGC in mangrove stands. The highest total AGC found in this study was 114.09 tons/ha at Rhizophora mucronata dominated forest, while the lowest total AGC was 12.86 tons/ha with Ceriops tagal as the dominant species. The AGC estimation in mangrove stands correlated positively with DBH and tree height. However, the biomass content and AGC are affected by the number of mangrove stands. The difference in the number of stands affect the amount of carbon content at each sample point.

Tourism Impact on Marine Ecosystems in the North of Red Sea

The unique marine environment of the northern Red Sea region is among the richest and most productive marine ecosystems in the world. The sea is populated with extensive algae blooms and at least five types of coral reefs. However, the region’s tourism sector is largely dependent on the surrounding environment, including the coral reefs, which are highly sensitive to human activities. A large tourist project (Neom) is scheduled to be installed in the northern Red Sea, further increasing tourist activities in the area and leading to human intrusion into crucial but fragile marine habitats such as seagrass beds, coral reefs and mangrove stands. The present study investigates how human activities are currently affecting Red Sea ecosystems. Field visits were done in order to investigate and to study human activities impact on marine ecosystems in the north of Red Sea. To the best of our knowledge, this work is the first of its kind to evaluate the impact of tourism on marine ecosystems in Saudi Arabia’s northern Red Sea coast.

Changes in insect biodiversity on rehabilitation sites in the southern coastal areas of Java Island, Indonesia

Abstract. Budiadi, Musyafa, Hardiwinoto S, Syahbudin A. 2020. Changes in insect biodiversity on rehabilitation sites in the southern coastal areas of Java Island, Indonesia. Biodiversitas 21: 1-7. Rehabilitation activities on coastal areas such as mangrove wetlands and dry-sandy soils may cause a change in the environmental quality, including insect diversity and their role. The research was conducted to compare the effect of stand structure on the rehabilitation areas of the south coast of Java Island and measure insect biodiversity affected by the changes to land cover. Systematic sampling technique was employed in four different land covers, i.e., dryland site of 10-year old Casuarina equisetifolia, and wetland sites of 12-year old Avicennia sp., mixed mangrove, and open grassland. Experimental plots (100 m x 10 m) were established for day- and night-time insect observation and tree inventory. Results showed that stand structure in the rehabilitation areas was low in tree diversity and lesser occurrence of natural regeneration. The insect taxa were dominated by Coleoptera in the Avicennia and mangrove stands, while different types of grasshopper of Acrididae were found in the grassland and Casuarina stands. Richer and more roles of insect species were found in mixed stands than in monoculture, and more in established stands than open grasslands. The rehabilitation activities change the microenvironment and insect diversity but have yet not been considered as an indicator of the success of rehabilitation.

People and Blue Carbon: Conservation and Settlements in the Mangrove Forests of Mexico

Mangroves provide multiple valuable environmental services, including their high potential for the sequestration of blue carbon. However, mangrove conservation is socially demanding. Through a spatiotemporal analysis of the inhabitants of this dynamic coastal ecosystem in Mexico, we found that the numbers of small settlements within mangroves increased during the study period despite a decline in mangrove stands and in the human populations inhabiting them. Extended rural developments have been banished to external buffer areas, whereas near-subsistence hamlets are increasingly occupying mangrove forest. The ability of mangroves to sequester atmospheric blue carbon relies on regional socioeconomic patterns and stressors that should be considered in the development of mangrove conservation initiatives. Our study enables identification of potential areas of research — e.g., forestry buffer zones, social exclusion, permanent settlements, and integral monitoring — that can incorporate the social dimensions of blue carbon conservation into the political and research agendas.

High temperature and crab density reduce atmospheric nitrogen fixation in Red Sea mangrove sediments

Mangrove ecosystems are highly productive and provide important ecosystem services. However, in the Red Sea mangroves are under severe nutrient-limiting conditions, reflected in dwarf plants. The nutrient limitation is especially acute for iron, as verified experimentally, although the low carbon-to-nutrient stoichiometric ratios reported for Red Sea mangrove leaves are indicative of general nutrient depletion. Therefore, atmospheric nitrogen (N2) fixation in mangrove sediments might be particularly important considering the minimal nitrogen inputs from land. Here, we tested the effect of temperature and crab density on sediment N2 fixation rates in mature and juvenile mangrove (Avicennia marina) stands in the central Red Sea. The average N2 fixation rates (from 0.002 ± 0.002 to 0.46 ± 0.12 mg N m−2 d−1) fall in the low range of N2 fixation rates reported in mangroves elsewhere, which is in agreement with the small size of the mangrove plants. Mature mangrove sediments hold higher N2 fixation rates than the juvenile mangrove sediment, related to a higher sediment organic matter and carbon content. We found a detrimental effect of temperature and crab density on sediment N2 fixation rates. Maximum N2 fixation rates were detected at 28 °C with a sharp decrease at 35 °C. Similarly, high crab-density reduced N2 fixation, likely due to the sediment oxygenation or the grazing of cyanobacteria by crabs. This is supported by i) previously reported higher oxygen concentration and redox around burrows compared to undisturbed sediment and ii) lighter sediment carbon isotopic composition in high crab-density than in low crab-density sediments, indicating a higher contribution of microphytobenthos in the mature sediments supporting low crab-density. Our data document temperature and crab density as factors affecting N2 fixation in the Red Sea mangrove sediments.

Urban-rural gradients in the distribution of trace metals in sediments within temperate mangroves (New Zealand)

Abstract We investigated the sequestering capacity of mangrove sediments through better understanding of trace metal distributions within a temperate estuary. We selected two mangrove stands within Manukau Harbour, New Zealand, based on proximity to contaminant sources. Organic matter (OM), pH, and metal (Cd, Co, Cr, Cu, Fe, Mn, Pb, Zn) concentrations in sediments were analysed. Positive correlations between OM and most trace metals, and metals themselves suggest common contamination sources and sequestering capacity of organic sediments. Higher trace metals in urban versus rural mangrove sediments indicate that contamination source is a major factor controlling metal distribution in these temperate intertidal ecosystems. Specific seasonal trends in metal distributions were not observed due to complex weather patterns and possible fluctuations in anthropogenic inputs. Overall, we suggest that metal dynamics in mangrove sediments are controlled by interacting factors, and that mangroves modulate the ultimate distribution and magnitude of these inputs within temperate estuaries.

Potential of mangrove stands carbon deposits in the north part Pannikang islands, Barru Regency, South Sulawesi province

Global warming is one of the world’s issues today. Global warming is a result of the greenhouse effect because it absorbs infrared light reflected by the earth from the sun. CO2 gas contributes the most to the greenhouse effect. The solution to the problem of global warming is the presence of forests. One type of forest ecosystem is the mangrove forest ecosystem. This study aims to determine the carbon storage of mangrove stands found on Pannikiang Island in the northern part of Barru Regency, South Sulawesi Province. Biomass measurement uses the allometric method performed on mangrove stems by measuring stem diameter in a circle-shaped sample plot of 12.62 m. The results showed that there were ten species found in the study locations: Avicennia alba, Avicennia marina, Bruguiera gymnorrhiza, Bruguiera sexangula, Ceriops decandra, Rhizophora apiculata, Rhizophora mucronata, Rhizophora stilosa, Scyphiphora hydrophyllaceae, and Soneratia alba. The total value of the total stem carbon deposits in the mangrove stands on Pannikiang Island in the northern part of Barru Regency reached a total carbon stem portion of 640,512 tons with a maximum range of 859,174 tons and a minimum of 421,871 tons.

Non-native mangroves support carbon storage, sediment carbon burial, and accretion of coastal ecosystems.

Mangrove forests play an important role in climate change adaptation and mitigation by maintaining coastline elevations relative to sea level rise, protecting coastal infrastructure from storm damage, and storing substantial quantities of carbon (C) in live and detrital pools. Determining the efficacy of mangroves in achieving climate goals can be complicated by difficulty in quantifying C inputs (i.e., differentiating newer inputs from younger trees from older residual C pools), and mitigation assessments rarely consider potential offsets to CO2 storage by methane (CH4 ) production in mangrove sediments. The establishment of non-native Rhizophora mangle along Hawaiian coastlines over the last century offers an opportunity to examine the role mangroves play in climate mitigation and adaptation both globally and locally as novel ecosystems. We quantified total ecosystem C storage, sedimentation, accretion, sediment organic C burial and CH4 emissions from ~70year old R. mangle stands and adjacent uninvaded mudflats. Ecosystem C stocks of mangrove stands exceeded mudflats by 434±33MgC/ha, and mangrove establishment increased average coastal accretion by 460%. Sediment organic C burial increased 10-fold (to 4.5MgCha-1 year-1 ), double the global mean for old growth mangrove forests, suggesting that C accumulation from younger trees may occur faster than previously thought, with implications for mangrove restoration. Simulations indicate that increased CH4 emissions from sediments offset ecosystem CO2 storage by only 2%-4%, equivalent to 30-60MgCO2 -eq/ha over mangrove lifetime (100year sustained global warming potential). Results highlight the importance of mangroves as novel systems that can rapidly accumulate C, have a net positive atmospheric greenhouse gas removal effect, and support shoreline accretion rates that outpace current sea level rise. Sequestration potential of novel mangrove forests should be taken into account when considering their removal or management, especially in the context of climate mitigation goals.

Checklist of bivalve molluscs in mangroves of Khánh Hòa Province, Vietnam

ABSTRACTThe diversity of bivalves was studied in four mangrove stands in the vicinity of Nha Trang city: planted mangroves in Dâm Bay (Tre Island) and three natural associations, in Dâm Bay, Nha Phu Bay and Cam Ranh Bay. Forty-five species from 18 families of bivalve molluscs were recorded in total. The richest families were Veneridae (eight species), Tellinidae (six species) and Lucinidae (five species). Five of the species are considered to be true mangrove associates, while others are eurybiotic species normally inhabiting mudflats and hard intertidal substrata, although some of them are commonly found in mangroves. An illustrated guide is provided, with short synonymies and data on ecology and distribution. The recorded molluscan diversity is compared with published data on mangrove Bivalvia in different regions of the Indo-Pacific. Since all characteristic groups and mangrove associates were present in our samples (except wood-borers that were not sampled), species composition of studied mangrove stands in Vietnam fits the general pattern of Indo-Pacific mangrove bivalve fauna.

The application of δ13C, TOC and C/N geochemistry of mangrove sediments to reconstruct Holocene paleoenvironments and relative sea levels, Puerto Rico

We assessed the use of δ13C, TOC and C/N values of bulk sedimentary organic matter (OM) to reconstruct paleoenvironmental and relative sea-level change from mangrove environments in Puerto Rico. The modern distribution of δ13C, TOC and C/N values was described from 63 vegetation and 59 surface sediment samples collected from three sites containing basin and riverine mangrove stands, and was compared to microfossil (foraminiferal and thecamoebian) assemblages. Four vertically-zoned environments were identified: tidal flat (δ13C: −18.6 ± 2.8‰; TOC: 10.2 ± 5.7%; C/N: 12.7 ± 3.1), mangrove (δ13C: −26.4 ± 1.0‰; TOC: 33.9 ± 13.4%; C/N: 24.3 ± 6.2), brackish transition (δ13C: −28.8 ± 0.7‰; TOC: 40.8 ± 11.7%; C/N: 21.7 ± 3.7), and freshwater swamp (δ13C: −28.4 ± 0.4‰; TOC: 42.8 ± 4.8%; C/N: 17.0 ± 1.1). These environments had distinct δ13C, TOC and C/N values, with the exception of the brackish transition and freshwater swamp zones that were difficult to distinguish on a geochemical basis alone. The foraminiferal assemblages were complicated by a group that did not show a relationship to elevation due to the presence of calcareous foraminifera occurring above mean higher high water (MHHW), likely resulting from washover or transport by storms. However, the ratio of foraminifera to thecamoebians (F/T) along with δ13C, TOC and C/N values refines the distinction between brackish and freshwater environments. Using linear discriminant analysis, we applied the δ13C, TOC, C/N and F/T distributions to a 1.7 m core containing a continuous sequence of Rhizophora mangle peat, which began accumulating at ~1650–1930 CE. Together, microfossils, δ13C, TOC, and C/N values, and the core chronology from 137Cs and radiocarbon dating revealed that sediments in the core likely accumulated in response to anthropogenic sediment delivery, making it unsuitable for relative sea-level reconstruction. We caution that in the absence of detailed litho-, bio-, chemo-, or chrono-stratigraphic analyses as presented here, care should be taken in interpreting sea-level histories derived from single dates on mangrove peats.

Holocene establishment of mangrove forests in the western coast of the Gulf of Mexico

The successful establishment of mangrove ecosystems depends on an intricate network of interactions among physical and biological factors that are highly dynamic through time. At millennial to centennial time scales, regional climates, sea levels, and local geomorphology play critical roles in the establishment of mangroves. Whereas fluvio-marine dynamics define coastal sedimentary settings, regional precipitation and freshwater input modulate salinity and seasonal flooding patterns. We analyzed a ~7800-year-old, continuous sedimentary record from the western coast of the Gulf of Mexico to shed light on regional biophysical coastal processes and the history of the mangroves that occupy the region today. We used a systematic sampling of mud-water interface sediments to generate a modern reference frame for interpreting fossil pollen assemblages. Our results indicate that the cored location that is currently approximately at sea level, was below sea level from ~7800 to 4000 calibrated years before present (cal BP). The establishment of dense mangrove stands took place around 3700 cal BP, when regional sea levels stabilized, resulting in a substantial increase of organic matter and therefore carbon stored in the sediments. However, the mangrove ecological succession that started at ~6000 cal BP was interrupted by a regional drought that extended from ~5400 to 3700 cal BP. From 3700 cal BP to Present, the lagoon has been characterized by relatively stable both substratum and sea level, that together have facilitated the establishment of mangrove forests. Overall, our record demonstrates the complexity of the interactions between local and regional factors in the development and evolution of both coastal geomorphology and ecosystems.

The role of forest restoration in conserving mangrove plant at the eastern coast of North Sumatra

Mangrove forests are wetland resources in coastal areas that important role in supporting of life. However, in recent decades, many mangrove forests have been degraded or lost, mainly due to the conversion of mangroves into ponds. Mangrove restoration activities on ex-pond lands have begun in recent years on the eastern coast of North Sumatra. This study aimed to measure the recovery of mangrove species through restoration activities on ex-pond lands and to know the composition of the restored mangrove forests at the eastern coast of North Sumatra. A total of 30 sample plots, each plot size of 10m by 10m, have been established at each age of mangrove stands (5-9 years) and secondary forests. All trees with the diameter (DBH) ≥ 2 cm in the sample plot were identified and measured the DBH. Overall, there were 14 mangrove species in all sample plots, equivalent to 42.42% of all true mangrove plants found in Indonesia. This result indicated that mangrove restoration has succeeded in restoring mangrove species diversity. Therefore, the mangrove restoration on ex-pond land needs to be promoted in an effort to restore various mangrove functions for community and coastal resources resilience.

Phenology and floral synchrony of Rhizophora mangle along a natural salinity gradient

AbstractRhizophora mangle is the most common species of mangrove within its range and a major component of coastal ecosystems in the tropics and subtropics. Its phenology is affected by seasonal variations in temperature, salinity, and precipitation, all of which may be altered by impending climate change. In this work, the monthly leaf, flower, and fruit phenology of R. mangle was assessed at three sites, along a natural salinity gradient for 12 months. We assessed phenological states using litter traps installed in mangrove stands, and by direct observation of leaf production at two sites, and flower, and fruit production at a single site. Phenological events were compared with seasonal climatic variations (in wind, rain, and temperature) to explore potential abiotic controls on the phenology of this species. Leaf shedding was lowest at the low salinity site. Leaf and stipule production showed a seasonal trend, decreasing during the cool and dry winter months. Flowering was highly seasonal and synchronous and peaked during the rainy season. Flowering was correlated with average temperature (r = 0.82; p < 0.05) at all three study sites, but was not correlated with precipitation. At the high‐salinity site, flowering was restricted to the rainy season. Fruit abortion was associated with wind speed (r = 0.79; p < 0.05). Flowering of R. mangle is induced by increasing temperatures and the onset of rains. Rising temperatures, drier summers, and more frequent and intense storms, due to climate change, may influence mangrove productivity, population dynamics, and floral synchrony.

Composition and Abundance Of Crustacea and Polychaeta In Mangrove Stands At Bulalo Kwandang District North Gorontalo Regency.

The aim of the study to determine the composition and abundance of Crustacea and Polychaeta based Mangrove stands in the village of Bulalo Kwandang District of North Gorontalo regency. The research conducted over four months. The method used is survey method and techniques of data collection was done by using a sample square. The data were analyzed by descriptive quantitative. The results showed that crustacea species which consists of 3 family, that is Portunidae, Sesarmidae, Ocypodidae, while the Polychaeta only one family that is Capitellidae family. At station 1 species which have the highest index of abundance that is Sesarma sp. Indv/m2 and 0.189 for species that have the lowest abundance index of 0.023 Indv/m2 Scylla serata . While at the station two species that have the highest abundance index Sesarma sp . of 0.188 Indv/m2 which has an index of abundance and low of Scylla serata the abundance index of 0.020 Indv/m2. The most abundance species found in the Rhizophora sp stands. Where species of the least discovered that the stand Avicenia sp.

THE ABUNDANCE, DIVERSITY, AND THE DENSITY OF MOLLUSKS IN TUTUWOTO MANGROVE AREA OF ANGGREK DISTRICT, NORTH GORONTALO REGENCY, GORONTALO, INDONESIA

<pre>The aim of the current study is to calculate the value of the abundance, diversity, and the density of phyla mollusks in the Tutuwoto mangrove area of Anggrek District. The survey method is used in this study as a method, which means that it collects the data directly at the research area. The observations were carried out under mangrove stands. The area of the observation plot is 5m x 5m. Phylum mollusks collected at the study site were counted by the number of individuals, abundance, diversity, and density of the types of each species. Sanon-Wienner formula is used to calculate the species diversity, Brower formula is used to calculate the density, and Odum formula is used to calculate the abundance of the species. The findings show that it is found that the reasearch about phylum mollusks in Tutuwoto mangrove area consisted of 6 (six) types namely <em>Terebralia sulcata, Terebralia palustris, Nerita articulate, Hexaplex trunculus, Anadara granosa, and Mactra grandis</em>. Based on the calculation of the abundance, diversity, and density of the mollusks phylum at the research site, there are several types that have the highest value. In the gastropod class, <em>Nerita articulata</em> has the highest score with an abundance of 30.41%, diversity of 0.36, and density of 0.17 ind / m2, followed by <em>Terebralia sulcata</em> with an abundance of 28.07%, diversity 0.36, and density of 0.16 ind / m2. However, the lowest is owned by <em>Terebralia palustris</em> with an abundance value of 17.54%, diversity of 0.31, and density of 0.10 ind / m2. The values of abundance, diversity, and density in the bivalve class have different values. The type of <em>Anadara granosa</em> has an abundance value of 53.06%, diversity of 0.34, and density of 0.08 ind / m2 while <em>Mactra grandis</em> has an abundance value of 46.94%, diversity of 0.36, and density of 0.07 ind / m2. Based on the predetermined criteria of the Gastropod class, it has the abundance in many categories, exceptional of <em>Terebralia palustris</em> which has sufficient criteria.</pre>

Comparison of biomass and net primary productivity among three species in a subtropical mangrove forest at Manko Wetland, Okinawa, Japan

This study was conducted to quantify and compare the above- and belowground biomass, litterfall and net primary productivity of three mangrove species in the family Rhizophoraceae: Bruguiera gymnorrhiza, Kandelia obovata, and Rhizophora stylosa, in Manko Wetland, Okinawa Island, Japan. A total of thirty five plots were monitored over five years. The studied mangrove stands of all three species were mostly dominated by a large number of small sized trees. Total above-ground biomass of B. gymnorrhiza, K. obovata, and R. stylosa was 64.9,111.6, and 208.290.6 Mg ha−1, respectively. There was no significant difference in AGB between B. gymnorrhiza and K. obovata, but AGB of both of these species differed significantly from that of R. stylosa. Similarly, there was no significant difference in total BGB between B. gymnorrhiza and R. stylosa, but BGB of both of these species differed significantly from that of K. obovata AGB and BGB of K. obovata increased with increasing basal area of this species. On the other hand, in case of AGB and BGB of B. gymnorrhiza and R. stylosa, it did not show any relationship with basal area of the respective species. The average annual rate of above-ground biomass increment was 15.7 Mg ha−1 yr−1 in the R. stylosa stands. Hence, R. stylosa stands recored a higher AGNPP (43.8 Mg ha−1 yr−1) than B. gymnorrhiza (17.7 Mg ha−1 yr−1) and K. obovata (22.3 Mg ha−1 yr−1). Annual total litterfall rates for B. gymnorrhiza, K. obovata, and R. stylosa during the five-year period was 10.1, 9.9, and 12.3 Mg ha−1 yr−1, respectively. The annual rate of NPP in the R. stylosa stands was greater than that of two other species. R. stylosa was the most productive tree in the mangroves of Manko Wetland area in terms of dry matter production.