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True mangroves are vascular plants (Tracheophyta) that evolved into inhabiting the mid and upper intertidal zone of tropical and subtropical soft-sediment coasts around the world. While several dozens of species are known from the Indo-West Pacific region, the Atlantic-East Pacific region is home to only a mere dozen of true mangrove species, most of which are rare. Mangrove trees can form dense monospecific or multispecies stands that provide numerous ecosystem services. Despite their eminent socioecological and socioeconomic relevance and the plethora of studies on mangroves, many details of the ecology of mangrove ecosystems remain unknown; and our knowledge about general ecological principles in mangrove ecosystems is scarce. For instance, the functional trait concept has hardly been applied to mangroves. Here we provide an inventory of 28 quantitative and 8 qualitative functional traits of true mangrove species and stipulate some insight into how these traits may drive ecosystem structure and processes. The differentiation between true mangroves and mangrove associates, which can dwell inside as well as outside mangrove forests, is reflected by a number of leaf traits. Thus, true mangroves exhibit lower specific leaf area, lower leaf N content, and lower K∶Na ratio, and higher leaf succulence, higher Na and Cl content, and higher osmolality than mangrove associates. True mangrove species that form pure stands produce larger leaves and exhibit higher N content per leaf area, higher leaf K and Ca content, greater maximum plant height, longer propagules, and lower root porosity than more sporadic species. The species-specific expression of most traits does not reflect the species' position along intertidal gradients, suggesting that adaptation to tidal inundation does not explain these traits. Rather, many of the traits studied herein exhibit strong phylogenetic signals in true mangroves. Thus, wood density is high in most species of the Rhizophoraceae, irrespective of their habitat or maximum height. On the other hand, species of the genus

Indonesian mangrove forests are of major local and global importance for ecological and economic reasons. Indonesia has both the largest area of mangrove forests and the highest mangrove deforestation rate by country. Using the mangrove-fringed Segara Anakan Lagoon on Java as a prime example, this chapter explains the ecosystem services provided by mangrove-dominated coastal ecosystems, as well as the threats to it. Related governance approaches and interventions are discussed, while special emphasis is given to water quality, “Blue Carbon” storage, biodiversity, natural resource use, land use change, and the underlying political and societal dynamics. While ecosystem service supply is strongly impaired in the Segara Anakan Lagoon, mainly because of deforestation and high sediment deposition related to land use change, mangrove ecosystems in other areas appear to be in a better state. Finally, directions of future research and recommendations for policy and society are given. Abstrak Hutan bakau Indonesia sangat penting secara lokal dan global karena memiliki nilai ekologis dan ekonomis. Indonesia merupakan negara dengan wilayah hutan bakau terluas, namun laju deforestasi hutan bakaunya tertinggi. Menggunakan Laguna Segara Anakan yang bertipe hutan bakau tepian pulau di Jawa sebagai contoh utama, bab ini membahas tentang jasa ekosistem yang diberikan oleh ekosistem pesisir yang didominasi hutan bakau maupun ancaman terhadap jasa ekosistem tersebut. Pembahasan meliputi pendekatan dan intervensi tata kelola yang terkait, sedangkan penekanan khususnya adalah pada kualitas air, cadangan karbon pada ekosistem pesisir dan laut ( ‘Blue Carbon’ storage), keanekaragaman hayati, pemanfaatan sumber daya alam, perubahan penggunaan lahan, dan dinamika sosial politik yang mendasarinya. Meskipun pasokan jasa ekosistem di Laguna Segaran Anakan sangat buruk, terutama karena deforestasi dan tingginya sedimentasi terkait dengan perubahan penggunaan lahan, ekosistem bakau di daerah lain kondisinya lebih baik. Di bagian akhir bab ini disajikan arah penelitian kedepan dan rekomendasi untuk kebijakan dan masyarakat.

Heavy metal pollution associated with human activity is of big concern in tropical bays. Microorganisms may be highly sensitive to heavy metals. Nonetheless, little is known about effects of heavy metals on microbial structure in tropical bay sediments. In this study, 16S rRNA gene sequencing and potential ecological risk index analysis were used to analyze the relationships between nine metals (arsenic, lead, cadmium, cobalt, chromium, copper, zinc, manganese, and nickel) and bacterial communities in the sediments of Bamen Bay, China. Our results showed that Bamen Bay was under a considerable ecological risk and cadmium had the highest monomial potential ecological risk. In addition, individual metal contamination correlated with bacterial community composition but not with bacterial α-diversity. Arsenic was the metal influencing bacterial community structure the most. Our findings provide a novel insight into the monitoring and remediation of heavy metal pollution in tropical bays.

Deforestation results in habitat fragmentation, decreasing diversity, and functional degradation. For mangroves, no data are available on the impact of deforestation on the diversity and functionality of the specialized invertebrate fauna, critical for their functioning. We compiled a global dataset of mangrove invertebrate fauna comprising 364 species from 16 locations, classified into 64 functional entities (FEs). For each location, we calculated taxonomic distinctness (Δ+), functional richness (FRi), functional redundancy (FRe), and functional vulnerability (FVu) to assess functional integrity. Δ+ and FRi were significantly related to air temperature but not to geomorphic characteristics, mirroring the global biodiversity anomaly of mangrove trees. Neither of those two indices was linked to forest area, but both sharply decreased in human-impacted mangroves. About 60% of the locations showed an average FRe < 2, indicating that most of the FEs comprised one species only. Notable exceptions were the Eastern Indian Ocean and west Pacific Ocean locations, but also in this region, 57% of the FEs had no redundancy, placing mangroves among the most vulnerable ecosystems on the planet. Our study shows that despite low redundancy, even small mangrove patches host truly multifunctional faunal assemblages, ultimately underpinning their services. However, our analyses also suggest that even a modest local loss of invertebrate diversity could have significant negative consequences for many mangroves and cascading effects for adjacent ecosystems. This pattern of faunal-mediated ecosystem functionality is crucial for assessing the vulnerability of mangrove forests to anthropogenic impact and provides an approach to planning their effective conservation and restoration., SCOPUS: ar.j, info:eu-repo/semantics/published

Understanding local patterns of species-specific litterfall can help predict spatial differences in the amount and quality of organic matter input to systems under different environmental conditions. However, little is known about the drivers of differences in litterfall production in mangroves. Here we combined data from leaf litterfall (LL) studies (n = 13) and floristic studies (n = 16) conducted in the mangroves of the Ajuruteua peninsula (North of Brazil), at sites composed mainly of Rhizophora mangle and/or Avicennia germinans. We investigated the relationship between LL and vegetation parameters (height, diameter, basal area, density, and relative density) using partial least-squares regressions (PLS-R), building four models with different combinations of these parameters. Vegetation parameters explained 69–85% of the annual LL of A. germinans and 50–66% of R. mangle. Relatively strong, univariate significant relationships were also found between basal area and A. germinans LL (R2 = 0.40), and between height and R. mangle LL (R2 = 0.41). Nonetheless, models with four to five predictors yielded better fits. To illustrate the applicability of our approach we used the PLS-R models to calculate the LL of simulated sites. This simulation indicated a clear increase in LL production along the transition from Avicennia- to Rhizophora-dominated mangroves. As the leaf litter of these species differ substantially in chemical composition and decomposability, such transition in species composition will likely affect nutrient dynamics in the region. Thus, we suggest reporting species-specific site characteristics along with LL in future studies to obtain more robust models to predict future LL production at sites of changing vegetation structure.

Urban development is driving the loss and subsequent fragmentation of mangrove forests in Penang, Malaysia. However, little research has focused on the implications of urbanization onto the biodiversity within mangrove forests. This study investigates and compares both vegetation and crab assemblages between urban and rural mangrove forests. Collectively, 5853 trees were recorded including 15 species from six families: Acanthaceae, Arecaceae, Lythraceae, Malvaceae, Meliaceae, and Rhizophoraceae. Avicennia marina accounted for 88.6% of all trees in the study and held the highest species importance (IV). Although the total number of mangrove tree species varied significantly between urban (14) and rural (7) mangrove forests, the mangrove forest structure based on IV did not vary significantly. In total, 633 crabs were recorded comprising 13 different species from three superfamilies: Grapsoidea, Ocypodoidea, and Paguroidea. Crab species richness did not vary between urban and rural sites, but the biomasses of five and the densities of four crab species varied significantly. Redundancy analysis (RDA) indicated that land use, salinity, and abundance of Avicennia officinalis can best describe the distribution of crab species (r2 =32.7). This study indicates that smaller fragmented urban mangroves at the east coast of Penang have a relatively high tree and crab diversity and are worth protecting, in addition to the larger mangrove forests on the west coast. The preservation of small yet interconnected mangrove sites could be critical to the recruitment of their flora and fauna and should be considered in decision-making processes.

Coastal aquaculture expansion resulted in mangrove area loss and ecosystem degradation in the past decades, mainly in tropical Asia. Despite increasing environmental concerns regarding nutrient and organic matter-rich effluents, little is known on the effects on adjacent estuarine and coastal food webs. To assess the impact and fate of anthropogenic nitrogen released from aquaculture facilities, we studied water quality and nitrogen (N) flow across an estuarine food web in an estuary in Hainan, China, using nitrogen stable isotopes (δ15N). We found higher δ15N values of ammonium, nitrate and suspended matter in the pond-covered inner estuary than further upstream, suggesting a strong influence of untreated pond effluents, which had a high δ15N (ammonium: ~16‰, nitrate: ~7‰, suspended matter: ~8‰). Fish and benthic invertebrates of the inner estuary had a higher δ15N than consumers further upstream and in similar aquaculture-free estuaries elsewhere, most likely due to direct or indirect uptake of 15N-enriched aquaculture effluents by phytoplankton and benthic algae. A major part of the artisanal catches from the estuary consists of small-size fish which is used as feed in the local aquaculture. Thus, estuarine fish incorporating aquaculture-effluent based food web signals are harvested and recycled as feed in aquaculture facilities, whose effluents sustain this local food web. The δ15N being at the high end of the global range on all trophic levels indicates an anthropogenic nitrogen loop in which some portion of the reactive nitrogen initially introduced into aquaculture ponds is continuously recycled and affects the estuarine food web. This recycling also indicates a shortcut in the otherwise inefficient nitrogen sink function of estuaries. Therefore, in areas with large-scale coastal aquaculture like in China and SE Asia the effect of reactive nitrogen from aquaculture sources on the performance of coastal ecosystems may be larger than previously thought.

The structure and functioning of coastal ecosystems are shifting worldwide as a result of natural changes and, even more important, consequences of intense human intervention, of which habitat destruction, overexploitation of resources and environmental pollution are among the most serious. In this context, the 56th Conference of the Estuarine Coastal Sciences Association was held in Bremen, Germany, in September 2016 under the umbrella topic ‘Coastal Systems in Transition: From a natural to an anthropogenically-modified state’. The objective of this Special Issue is to demonstrate and synthesize the effects of both, natural variations and human intervention in estuaries and other coastal ecosystems. The 22 articles originate from various disciplines and cover a wide range of ecosystems, including temperate and tropical estuaries, hypersaline lagoons, mangrove forests, coral reefs and coastal dunes. The articles are categorized under four main topics, (1) drivers and dynamics of coastal systems, (2) impacts on estuarine biodiversity and community structure, (3) impacts on estuarine and bay functioning, and (4) management options for protecting estuarine diversity, functions and services. Several of the studies clearly show that estuarine systems are affected by multiple pressures, of which changes in salinity, hydrology, trophic state and habitat complexity as a consequence of human intervention are most frequently addressed. One of the main challenges remains distinguishing between natural and human-induced changes in biological, geochemical and physical processes and the interactions between them. A number of studies provide excellent examples of how biological indicators (e.g., benthic and fish diversity and community structure) are suitable for assessing the effects of stressors on ecosystems. It remains an important task to standardize these indicators for easier application in other locations and for evaluating the success of management measures. The high variability of coastal systems, the complex process interactions, and increasing pressure require interdisciplinary studies on a deeper understanding of processes as well as scenario experiments by model applications.

Ocypodid crabs inhabit intertidal sandy/muddy flats of tropical and sub-tropical mangroves. Iran has three species of the genus Austruca. In contrast to A. sindensis and A. lactea, almost nothing is known about the population dynamics and its driving factors in Austruca iranica. Thus, population ecology and reproductive biology of A. iranica were studied in relation to sediment temperature and rainfall in a sub-tropical Iranian mangrove forest over a period of 13 months. Crab density and Gonado Somatic Index (GSI) were significantly correlated with sediment temperature (r2 = 0.87, p ≤ 0.05). Reproduction was restricted to spring and summer and ovigerous females appeared when both sediment temperature and rainfall had their maximum values. Rainfall triggered crab reproduction, but did not significantly correlate with crab density. Symptotic carapace width (L∞) and growth constant (k) were 16.9 mm and 1.0 yr. −1 in females (n = 251), and 18.5 mm and 0.9 yr. −1 in males (n = 325), respectively. Size frequency distributions in both females and males had a common asymmetrical bi-modal pattern with two cohorts. Total mortality was higher in females (2.74) than in males (2.29). The overall sex ratio did not differ significantly from the expected 1:1 proportion (χ2 = 20.50, p > 0.05). Size at the onset of maturity was 10.2 mm in females. In comparison to other literature on ocypodid crab species, this study revealed that A. iranica is a relatively slow growing crab, with low fecundity and mortality rates, and with a relatively long life expectancy of about two years. The results of this research are a key for establishing a management plan to conserve the population of A. iranica along the Iranian coasts.

Many ecological processes are influenced by salinity. Burrowing crabs, abundant fauna of mangrove forests around the world, can facilitate sediment water fluxes, which may decrease the salinity in mangrove sediments. We investigated whether and how crab burrow density and secondary fine root biomass interact to drive sediment salinity during the dry season in a northern Brazilian mangrove forest. Areas with high density of Rhizophora mangle prop roots and areas free of such roots were compared. We found no correlation between burrow density and sediment salinity in areas with dense prop and fine roots, while crab density correlated negatively with sediment salinity in areas without prop roots, where fine root density was low. Hence, the strength of sediment desalination effects of crabs seems to be context dependent, and high root density of a salt-excluding mangrove species (R. mangle) seems to counteract the crabs’ effect. Our results complement those of a former study conducted in the same area during the rainy season, highlighting that the findings are independent from seasonality and should be considered when evaluating the overall ecological effects of crabs in mangrove ecosystems.

Mangrove leaves form a large pool of carbon, nitrogen and energy that is a major driver of element cycles and detrital food webs inside mangrove forests as well as in adjacent coastal waters. However, there are large gaps in knowledge on the transformation pathways and ultimate fate of leaf nitrogen. Therefore, the main objective of this study was to determine the amount and composition of nitrogenous organic matter and possible species-specific differences during the decomposition of mangrove leaf litter. For that purpose a three month decomposition experiment with litterbags was conducted using leaves of Aegiceras corniculatum, Avicennia alba, Ceriops decandra, Rhizophora apiculata, and Sonneratia caseolaris in the mangrove forest of the Segara Anakan Lagoon, Java, Indonesia. Detrital leaves were analyzed for bulk carbon and total nitrogen (N), stable carbon and nitrogen isotope composition (δ13C, δ15N), total hydrolyzable amino acids (THAA) and total hydrolyzable hexosamines (THHA). Decomposition rates (k d−1) were highest and tM50 values (when 50% of the original mass had been degraded) lowest in S. caseolaris (k = 0.0382 d−1; tM50 = 18 days), followed by A. alba, C. decandra, A. corniculatum, and R. apiculata (k = 0.0098 d−1; tM50 = 71 days). The biochemical composition of detrital leaves differed significantly among species and over time. S. caseolaris and A. alba had higher concentrations of N, THAA and THHA and a lower C/N ratio than the other three species. For most of the species concentrations of N, THAA and THHA increased during decomposition. The hexosamine galactosamine, indicative of bacterial cell walls, was first found in leaves after 5–7 days of decomposition and increased afterwards. Our findings suggest an increasing, but species-specific varying, portion of labile nitrogenous OM and total N in decomposing leaves over time that is partly related to the activity of leaf-colonizing bacteria. Despite a higher relative nitrogen content in the remaining litter of the fast decomposing S. caseolaris and A. alba as compared to the other three species, the total loss of nitrogen was even higher because of the much higher mass loss after three months of decomposition. It is inferred that the amount of labile nitrogenous organic matter plays a major role in determining the rate of decomposition of leaf litter in mangroves.

Java is the economic and political center of Indonesia, a country with > 17,500 islands. Southeast Asia is a hotspot of marine biodiversity, and Java hosts coral reefs, seagrass beds, and mangrove forests, which have an unparalleled role in providing ecosystem services. The Indonesian seas play a decisive role for the coupled ocean and climate system. For the local population, coastal and marine resources are a crucial protein source and have a high economic importance. Java is one of the most densely populated regions in the world, so there is a very strong influence of human activities on the terrestrial and marine ecosystems. Overexploitation, pollution, and ecosystem conversion have already led to habitat degradation and shortage of many natural resources. Here we review the regional oceanic system of Java, its major coastal habitats, coastal and marine resource uses, and human impacts on its coastal and marine ecosystems.

Non-target screening analyses were conducted in order to identify a wide range of organic contaminants in sediment and animal tissue samples from Jakarta Bay. High concentrations of di-iso-propylnaphthalenes (DIPNs), linear alkylbenzenes (LABs) and polycyclic aromatic hydrocarbons (PAHs) were detected in all samples, whereas phenylmethoxynaphthalene (PMN), DDT and DDT metabolites (DDX) were detected at lower concentrations. In order to evaluate the uptake and accumulation by economic important mussel (Perna viridis) and fish species, contaminant patterns of DIPNs, LABs and PAHs in different compartments were compared. Different patterns of these contaminant groups were found in sediment and animal tissue samples, suggesting compound-specific accumulation and metabolism processes. Significantly higher concentrations of these three contaminant groups in mussel tissue as compared to fish tissue from Jakarta Bay were found. Because P. viridis is an important aquaculture species in Asia, this result is relevant for food safety.

Jakarta, the capital of Indonesia, is one of the rapidly growing coastal megacities in Asia. The implementation of the urban wastewater infrastructure is not keeping up with the rapid expansion of the city, leading to a severe deterioration of water and sediment quality in the metropolitan area. The present study aimed to assess sediment contamination with organic pollutants in Jakarta rivers and the related risks to the coastal ecosystem. To this end, the site-specific and most harmful organic pollutants in the sediments were quantified, and the obtained chemical data were compared to reported sediment toxicity thresholds for an impact assessment on the benthic community. The detected pollutant spectrum included several compounds, such as the detergent residues nonylphenols and the insect repellent DEET (N,N-diethyl-m-toluamide), that were previously reported as contaminants in industrialized countries but have been banned or partly substituted. The risk of sediment contamination for benthic macroinvertebrates was associated with PAHs (polycyclic aromatic hydrocarbons), DDT (bis(chlorophenyl)dichloroethane), nonylphenols and a synthetic fragrance. High concentrations of paper manufacturing educts, a compound class that was recently reported in industrialized areas with a flourishing paper industry, were found in Jakarta sediments. However, sediment quality guidelines or sediment toxicity thresholds for these compounds are not available, which limited the ecotoxicological risk assessment. More studies on sediment toxicities considering emerging industrial pollutants and test species from all climate regions are urgently required, as a prerequisite for an adequate impact assessment of sediment contamination.

Antibiotic residues and antibiotic resistance genes (ARGs) have been found worldwide. Chloramphenicol, one of antibiotics, had been banned for its use in breeding industry in many countries. The status about chloramphenicol resistance genes (CRGs) in mangrove ecosystems is still unknown. In the present study, quantitative PCR was employed to investigate the abundance of CRGs. The residual determination of chloramphenicols was performed via ultra-high pressure liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Although the concentrations of chloramphenicol residues were at undetectable or relatively low levels, the abundance of CRGs was still alarming. The CRG abundance was dynamically different with the season change, and was highest in the surface layer and gradually decreased with the sampling sites away from the mangrove. The 16S rRNA high-throughput gene sequencing results revealed that cyanobacteria, fusobacteria and planctomycetes were the most dominant phyla co-occurring with CRGs. The results indicated that antibiotic residues could make a long term impacts on the environment eventhough after their degradation.

Coral reefs have extremely high ecological value in tropical and subtropical waters worldwide. However, they have been subjected to the most extensive and prolonged damage in recent decades. Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous hazardous pollutants and are highly resistant to degradation in marine environments. Among these compounds, benzo(a)pyrene (BaP) has exerted pressure on corals due to water discharges, oil spills and coastal tourism. In the present study, the physiological response, oxidative stress and stress-related genetic expressions of two Acropora spp. (Acropora formosa and Acropora nasuta) were analysed. These two coral species were exposed to 10 and 40 μg·L−1 BaP for 24 hand 72 h, respectively. The results show that (1) BaP affects the health of the zooxanthellae in coral symbiosis after BaP exposure for 72 h due to a significant decline in chlorophyll a concentrations in Acropora spp. during this period. (2) An exposure of 10 μg·L−1 BaP for 24 h induced serious oxidative damage to Acropora spp., with a significant decline and increase in superoxide dismutase (SOD) activities in A. formosa and A. nasuta. (3) The P-gp gene is more sensitive in A. formosa, while the Hsp70 gene is more sensitive in A. nasuta. (4) A. formosa showed a lower ability to resist organic pollutants in coral reefs. Overall, further ecotoxicological studies are needed to investigate the impact of chemical pollutants on corals and to compare their different response mechanisms.

This chapter assesses the response of mangrove ecosystems to possible outcomes of climate change, with regard to the following categories: (i) distribution, diversity, and community composition, (ii) physiology of flora and fauna, (iii) water budget, (iv) productivity and remineralization, (v) carbon storage in biomass and sediments, and (vi) the filter function for elements beneficial or harmful to life. These categories are then used to identify the regions most vulnerable to climate change. The four most important factors determining the response of mangrove ecosystems to climate change are sea level rise, an increase in frequency and/or intensity of storms, increases in temperature, and aridity. While these changes may be beneficial for some mangrove forests at latitudinal distribution limits, they will threaten forest structure and functions and related ecosystem services in most cases. The interaction of climate change with human interventions is discussed, as well as the effects on ecosystem services including possible adaptation and management options. The chapter closes with an outlook on knowledge gaps and priority research needed to fill these gaps.

The mud crab Scylla serrata (Forskal, 1775) (Portunidae) is a commercial species in the Indo-West-Pacific. Despite its high fishery value, the microhabitat of its early juvenile stages remains unknown. We studied microhabitat use by the ‘early benthic stage’ (EBS, between 3 and 30 mm carapace width, CW) at two sites in eastern Australia by two types of artificial benthic collectors and baited traps. 92% of EBS mud crabs were captured in muddy areas, compared to 8% on sandy habitats. The majority of the EBS mud crabs (87%) was found in intertidal areas within the mangrove fringe, only few individuals (13%) were found on unvegetated mud flats seawards to the mangroves. EBS from the mudflat (including first instars of 3-4 mm CW) were significantly smaller (p

Mangrove crabs influence ecosystem processes through bioturbation and/or litter feeding. In Brazilian mangroves, the abundant and commercially important crab Ucides cordatus is the main faunal modifier of microtopography establishing up to 2 m deep burrows. They process more than 70% of the leaf litter and propagule production, thus promoting microbial degradation of detritus and benefiting microbe-feeding fiddler crabs. The accelerated nutrient turn-over and increased sediment oxygenation mediated by U. cordatus may enhance mangrove tree growth. Such positive feed-back loop was tested in North Brazil through a one year crab removal experiment simulating increased harvesting rates in a mature Rhizophora mangle forest. Investigated response parameters were sediment salinity, organic matter content, CO2 efflux rates of the surface sediment, and reduction potential. We also determined stipule fall of the mangrove tree R. mangle as a proxy for tree growth. Three treatments were applied to twelve experimental plots (13 m × 13 m each): crab removal, disturbance control and control. Within one year, the number of U. cordatus burrows inside the four removal plots decreased on average to 52% of the initial number. Despite this distinct reduction in burrow density of this large bioturbator, none of the measured parameters differed between treatments. Instead, most parameters were clearly influenced by seasonal changes in precipitation. Hence, in the studied R. mangle forest, abiotic factors seem to be more important drivers of ecosystem processes than factors mediated by U. cordatus, at least within the studied timespan of one year.

Indonesia has the largest area and the highest tree species richness but also one of the highest loss rates of mangroves worldwide. The Segara Anakan lagoon is a mangrove-fringed estuarine system in Java which is highly affected by deforestation, sedimentation, and land-use changes. The spatial variability of diversity, community composition, density, height, aboveground biomass and habitat complexity of the mangrove forest in relation to abiotic conditions was studied in 2014/2015. Vegetation characteristics were compared with those available from 2005/2006, and the effects of deforestation on the forest condition were assessed. In total, 15 mangrove tree species were recorded in 2015, six less than ten years ago. The two main areas of the lagoon, the central and eastern one, had a significantly different tree community composition. The central area was dominated by the palm Nypa fruticans and Aegiceras corniculatum and 74% of the ground was covered by the understorey plants Acanthus spp. and Derris trifoliata. Tree density, stand basal area, species number, aboveground biomass, and habitat complexity were significantly lower in the central area as a result of deforestation. Stand basal area and aboveground biomass decreased significantly over the 10 years as well as the density of Avicennia spp., Sonneratia spp., Ceriops spp., Aegiceras corniculatum, and Bruguiera spp. The eastern area was dominated by A. corniculatum and Rhizophora apiculata, and coverage with understorey plants was only 11%. The density of R. apiculata increased significantly over the 10 years as a result of natural regeneration and reforestation. The overall low tree height (2.8 m) and aboveground biomass (18.4 t dry mass ha−1) point to a young and degraded forest. In the central lagoon, mangrove reforestation is probably extremely difficult due to the strong expansion of understorey plants. It is assumed that ongoing deforestation will cause a further spread of understorey plants, a decrease in species number, tree density and habitat complexity. A decline in microhabitats and aboveground biomass can lead to a decrease of faunal species and biomass which in turn would influence nutrient cycling and impair the nursery function of the area. Also, important ecosystem services, particularly coastal protection against storms and prevention of coastal erosion are most likely affected.

The mud crab Scylla serrata is a highly exploited species, associated to mangrove ecosystems in the Indo-West-Pacific. It has a complex life cycle with a dispersing larvae phase, and benthic juveniles and adults. The former are stenohaline depending on high-salinity conditions to survive, whereas the latter are physiologically well adapted to changing temperatures and salinities, conditions that typically occur in mangrove habitats. Movement and habitat use of large juveniles and adults are well studied, and these life stages are known to utilize and move between various habitats within the mangrove ecosystem: intertidal flats as well as subtidal channels and flats. Females undertake long movements from brackish inshore waters to waters with oceanic conditions for spawning. Sensory abilities—of early stages and adult stages—have hardly been studied, and little is known about larval and early benthic stages in the wild. Summarizing, the literature revealed substantial gaps in the understanding of the spatiotemporal dynamics of the different life stages and of the clues that trigger recruitment, movement, and other behavior. This is the first comprehensive review on the life history, movement patterns, habitat use, and systemic role of S. serrata with emphasis on the respective life stages and geographic differences. We emphasize the need for further research into these processes as a basis for the sustainable management and conservation of this species.

Tropical coastal and marine social–ecological systems (CM-SES) are diverse, complex and dynamic, facing special challenges as hotspots of biodiversity and centres of population growth. Sustainability science focuses on the state of such systems and mostly analyses undesirable social–ecological outcomes. In a collaborative effort between natural and social scientists, this paper examines not only key indicators for identifying the states of CM-SES but puts major emphasis on examining the processes that support sustainable tropical CM-SES dynamics. We identify a number of processes that drive desirable social–ecological dynamics, link the debates on ecosystem services and social–ecological systems analysis and offer a framework for identifying the links between key social–ecological processes. The article suggests linking relevant knowledge production processes and other sustainability-enhancing processes to each other and indicates related research needs.

Diversity and composition of the intertidal brachyuran crab community in the Segara Anakan Lagoon (SAL), Java, Indonesia, during the dry season of 2005 and the rainy season of 2006, shows that crab community composition and structure alone appeared to be poor indicators for the state of a forest in terms of tree diversity and wood-cutting intensity. The lagoon is surrounded by the largest mangrove stand in Java and is under constant anthropogenic pressure, mainly due to logging, land conversion for agriculture, overfishing and industrial pollution. This study aims to determine the crab community composition at different sites of the lagoon in relation to vegetation composition and sediment parameters. In addition it investigates if mangrove crabs can be used as bioindicators to describe the environmental state of mangrove forests (tree diversity, degree of logging). It was assumed to find a low crab diversity and species richness and a strong dominance of a single species at highly disturbed forest sites compared to moderately disturbed sites. A stratified, hierarchical design was used to sample the crab fauna at 13 stations distributed over the entire lagoon. Additionally, abiotic parameters and vegetation composition were recorded. In total 6463 crabs were caught belonging to 49 species, 5 superfamilies and 10 families, with Ocypodidae and Sesarmidae being the families of most note. Mean density of adult crabs was 27.7 individuals*m −2 and mean biomass was 12.8 g wet mass*m −2 or 1.3 g ash free dry mass*m −2 . Density and biomass varied strongly within and between stations but they where within the range reported for other mangrove forests of the Indo-West-Pacific. Species composition was significantly different between stations. The distribution of facultatively leaf-feeding grapsid crabs was related to vegetation parameters (tree, seedling and undergrowth density), but the occurrence of single crab and tree species was not correlated. The distribution of ocypodid crabs, feeding on detritus and microphytobenthos, correlated with sediment characteristics like median grain size and organic content. The crab community was strongly dominated by one species at six stations, however, this was not correlated to the degree of logging. Leaf-feeding crab and mangrove tree diversity was correlated at areas of one hectare (stations), but not at a lower spatial scale (areas of 100 m 2 , “zone”). Species richness of leaf-feeding crabs was not linked to forest diversity. Hence a functional relation between leaf-feeding crab and tree species diversity could not be proven.

A new species of Echinoderes, E. applicitus sp. nov., is described from a brackish water lagoon on the south coast of Central Java, Indonesia. The species is recognized by its complete lack of spines on segments 1–10, lateroventral tubules on segments 5 and 8, laterodorsal tubules on segment 10, and a mid- to subdorsal tergal protrusion of segment 10 that extends beyond the posterior margin of segment 11. The general reduction of spine size and numbers, the absence of lateral terminal accessory spines in females and the enlarged sieve plate suggest a close relationship with E. rex, E. coulli, E. maxwelli and E. teretis. The adaptation to a brackish, estuarine habitat with highly fluctuating salinities is also shared between the three latter species and E. applicitus sp. nov. The examined populations of the new species had a relatively high infection rate (10–15%) of epibiontic growth from at least three different prokaryotic or protist organisms. An infection rate of this magnitude has not previously been reported for kinorhynchs, and it may have a relationship to the brackish habitat.

The large amounts of leaf litter produced by tropical mangrove forests serve as a major food source for the benthic fauna. The reasons for the preferential consumption of mangrove leaves by crabs are unclear as yet. We investigated the diet, food preferences and consumption rates of 8 dominant grapsoid crab species ( Perisesarma spp., Episesarma spp., Metopograpsus latifrons , and Metaplax elegans ) in mangroves of Segara Anakan, Java, Indonesia, by means of stomach-content analysis and feeding experiments. Leaves from the five most abundant mangrove tree species ( Aegiceras corniculatum , Avicennia alba , Ceriops decandra , Rhizophora apiculata , and Sonneratia caseolaris ) were analyzed for organic carbon, total nitrogen, δ 13 C, δ 15 N and amino acids and hexosamines. This study is the first that investigated crab food preferences related to the nitrogen compound composition of leaves. Our results show that Episesarma spp. and Perisesarma spp. are omnivorous crabs which mainly feed on detritus, mangrove litter and bark, and on a small amount of roots, algae and animal matter whereas M. elegans is a detritus feeder. In feeding experiments with green, yellow and brown leaves Perisesarma spp. and E. singaporense had the highest consumption rates for brown leaves of R. apiculata and S. caseolaris , and for green leaves of A. alba . Preferred leaves were characterized by a high amount and/or freshness of nitrogenous compounds and their biochemical composition was significantly different from that of disliked leaves (all leaves of A. corniculatum and C. decandra , green and yellow leaves of R. apiculata and S. caseolaris ). The presence of the hexosamine galactosamine found only in brown leaves indicates that bacteria contribute to the amount of bioavailable nitrogen compounds. We infer that the nitrogen compound composition rather than the C/N ratio alone is a determinant for bioavailability of mangrove leaves and hence may partly explain the crabs' food preferences.

Segara Anakan, a mangrove-fringed coastal lagoon in Indonesia, has a high diversity of macrobenthic invertebrates and is increasingly affected by human activities. We found >50 organic contaminants in water, sediment and macrobenthic invertebrates from the lagoon most of which were polycyclic aromatic compounds (PACs). Composition of PACs pointed to petrogenic contamination in the eastern lagoon. PACs mainly consisted of alkylated PAHs, which are more abundant in crude oil than parent PAHs. Highest total PAC concentration in sediment was above reported toxicity thresholds for aquatic invertebrates. Other identified compounds derived from municipal sewage and also included novel contaminants like triphenylphosphine oxide. Numbers of stored contaminants varied between species which is probably related to differences in microhabitat and feeding mode. Most contaminants were detected in Telescopium telescopium and Polymesoda erosa. Our findings suggest that more attention should be paid to the risk potential of alkylated PAHs, which has hardly been addressed previously.

The benthic macrofauna of the Segara Anakan lagoon, Java, Indonesia and its fringing mangroves were investigated between May 2004 and August 2006. This lagoon has been affected by various human activities for decades, in particular fishing, effluents from agriculture and industry, and illegal deforestation. In total, 163 taxa were identified, including 127 species occurring in the mangrove forest and 59 species in the subtidal. Mean density of macrobenthos was 2.5-fold higher in the central (881.8 ± 1,151.3 ind. m−2) than in the eastern mangrove site (356.3 ± 218.8 ind. m−2). Community structures differed significantly between these sites and showed a serial shift during the investigation period. Gastropods dominated the community in the central mangrove location, whereas sipunculids, polychaetes and gastropods had similar densities in the eastern site. Differences in community composition were best explained by three sediment properties: pore water salinity, δ13Corg, and Corg/N. It is suggested that small-scale heterogeneity of food availability and quality is a main factor determining the small-scale variability of the community composition. Compared to other Indo-West Pacific mangroves, species richness and densities are high. However, the dominance of specific taxa, especially of opportunistic species and the comparably low species richness in the subtidal of the lagoon may be attributed to the high sediment input by rivers in the central part and to the large-scale cutting of mangroves. Continuous tree logging will probably lead to a further spread of two fast growing understorey plants and thus to an increase of uniform swamp sites and a decrease of micro-habitats for benthic macrofauna. To our knowledge, this is the first detailed study on the spatio-temporal variation of benthic macrofauna in mangroves of Indonesia.

Activity patterns, feeding and burrowing behaviour of the economically important semi-terrestrial mangrove crab Ucides cordatus (Ucididae, L. 1763) was studied in a high intertidal Rhizophora mangle forest stand in Braganca, North Brazil. Video observations in the rainy and dry season were conducted over 24 h cycles at different lunar phases to investigate the behaviour of these litter-feeding crabs outside their burrows. During the rainy season, crabs stayed inside their burrows for 79% and 92% of the time during day and night, respectively. Time spent for feeding, burrowing and other activities outside their burrows was significantly longer during the day with 9.9% (night: 1.7%) and at waning and waxing moon with 9% (full and new moon: 0.9%). At neap tides (no tidal inundation) foraging and feeding activities outside burrows were clearly light-dependent, increasing at dawn and decreasing at dusk. Highest activities during daytime relate to the visual localisation of food. During the dry season, crabs spent less time inside burrows at neap tides than during the rainy season (80% and 91%, respectively). However, time spent for feeding activities was similar during both seasons. During almost all observation periods crabs collected leaf litter, but rarely fed on it outside burrows. At neap tides nearly all available litter was collected, suggesting that the U. cordatus population is litter-limited during these times. At spring tides (regular tidal inundation) the surface activity of U. cordatus was tide-dependent. Crabs closed their burrow entrances 2–3 h before flooding and re-emerged as soon as the tide retreated. During the day, burrow maintenance was the second most frequent behaviour after feeding. Agonistic interactions were regularly observed and were mainly related to burrow defence. The mean foraging radius of the crabs was only 19 cm (max: 1 m) underneath high Rhizophora mangle trees where crab densities were high. The results point to a high competition for burrows and show that U. cordatus is territorial. It is concluded that several exogenous factors, in particular light, leaf litter availability, flooding of burrows and the presence of conspecifics are important in controlling the crabs' activity patterns.

In the Segara Anakan lagoon, Java, 21 tree species and 5 understorey genera have been identified. Average tree density is 0.80 ± 0.99 Ind./m² with 48.71% seedlings and an average basal area of 9.86 ± 10.54 cm²/m². Tree density and diversity are high in the eastern part of the lagoon, located near the city of Cilacap. There, the dominant tree species are Aegiceras corniculatum, Nypa fruticans and Rhizophora apiculata, of which the two latter are characteristic for mature forests. By contrast, understorey species and the pioneer species (Avicennia alba, Aegiceras corniculatum and Sonneratia caseolaris) dominate the central lagoon where several rivers discharge. Compared to former studies, seedling density and tree diameter in the central lagoon has declined considerably and tree species dominance has changed. The high sedimentation rates and deforestation are likely to prevent the formation of a mature forest there. Tree communities are more equilibrated in the eastern lagoon which points to a more stable and less disturbed mangrove forest.

The effect of land use on the biogeochemistry of small tropical rivers and their estuaries was studied using the Kallada River and Ashtamudi estuary located in the State of Kerala, India, as a model system. Water, suspended matter and sediments collected during the monsoon and intermonsoon periods in 2002 and 2003 were analyzed for dissolved nutrients (nitrate, nitrite, phosphate, silicate) and for phytoplankton abundance and composition, amino acid contents and stable carbon (C)) and nitrogen (N) isotope ratios. Seasonal and spatial variations of dissolved nutrients and suspended matter along the course of the river point to distinct differences in the C and N sources that are controlled by hydrology, geology and land use. Unusually low concentrations of dissolved silicate and suspended matter suggest low erosion rates of the Precambrian basement rocks and the firm lateritic soils in non-agricultural areas. Most dissolved nutrients and suspended particulate organic matter originated from fertilized agricultural soils. The biogeochemistry of sedimentary organic matter indicates that most of the Kallada River load is deposited in the upper Ashtamudi estuary, while the middle and lower parts have a stronger marine influence. The spatio-temporal variation of dissolved and particulate river fluxes clearly indicates an effect of land use and land cover on the biogeochemistry of the Kallada River. While the phosphate yield was high (6 × 103 mol km−2 year−1 or 185 kg km−2 year−1), the N yield was relatively low (10 × 103 mol km−2 year−1 or 141 kg km−2 year−1), which is unlike the situation in many other densely populated regions of tropical Asia.

Water uptake by mangrove trees can result in salt accumulation in sediment around roots, negatively influencing growth. Tidal pumping facilitates salt release and can be enhanced by crab burrows. Similarly, flushing of burrows by incoming tidal water decreases sediment salinity. In contrast to burrows with multiple entrances, the role of burrows with one opening for salinity reduction is largely unknown. In a microcosm experiment we studied the effect of artificial, burrow-like macro-pores with one opening on the desalting of mangrove sediment and growth of Rhizophora mangle L. seedlings. Sediment salinity, seedling leaf area and seedling growth were monitored over six months. Artificial burrows facilitated salt release from the sediment after six weeks, but seedling growth was not influenced. To test whether crab burrows with one opening facilitate salt release in mangrove forests, sediment salinities were measured in areas with and without R. mangle stilt roots in North Brazil at the beginning and end of the wet season. In addition, burrows of Ucides cordatus were counted. High crab burrow densities and sediment salinities were associated with stilt root occurrence. Precipitation and salt accumulation by tree roots seem to have a larger effect on sediment salinity than desalting by U. cordatus burrows.

This study provides the first quantification of the population food intake of the litter-consuming mangrove crab Ucides cordatus (Ocypodidae, L. 1763) in a New World mangrove forest. Diet, feeding periodicity, gastric evacuation rates and size-dependent consumption were determined for this intensively exploited semi-terrestrial crab in different types of mangrove forest. Unlike many other crabs Ucides cordatus is a continuous feeder, as shown by gastrointestinal contents over a day's cycle. Starvation experiments revealed that most gastric evacuation occurs during the first 12 h after feeding, following an exponential decay function. Evacuation rates (0.35 h −1 and 0.31 h −1 ) for small (carapace width CW 2.5–3.5 cm) and large (CW 6.5–7.5 cm) crabs, respectively, and the mean daily gastrointestinal contents were used to calculate the daily food intake (DFI) of U. cordatus for both sexes and different size classes. DFI was strongly correlated to body size and ranged from 19.8 to 6.0% of body dry weight in small and large crabs, respectively. The daily energy intake of U. cordatus (37.6 kJ for a 65 g wet weight specimen) was high when compared to other leaf-eating crabs. Litter fall and propagule production were calculated as 16.38 t ha −1 y −1 , corresponding to a daily mean of 4.49 g m −2 in a high intertidal Rhizophora mangle forest stand. The estimated population food intake of Ucides cordatus (4.1 g dw m −2 d −1 ) corresponds to 81.3% of this production. This high litter removal rate, a low litter quantity in burrows and high consumption rates during field experiments suggest that the local crab population is food-limited in many parts of the study area. The very efficient coupling of forest litter production and crab litter consumption is possible due to the high crab density and the low inundation frequency of the mangrove forests, allowing for prolonged foraging periods. By processing the major part of the litter, U. cordatus helps to retain nutrients and energy within the mangrove ecosystem. The impact of this species on litter turnover in a New World mangrove is similar to or even higher than that of litter-feeding sesarmid crabs in the Indo-West Pacific region.

The Cochin Backwaters in India are part of the Vembanad-Kol system, which is a protected wetland and one of the largest estuarine ecosystems in South Asia. The backwaters are a major supplier of fisheries resources and are developed as tourist destination. Periyar River discharges into the northern arm of the system and receives effluents from chemical, petrochemical and metal processing industries which release huge amounts of wastewaters after little treatment. We investigated water and sediment contamination in the industrial vicinity and at one station further away including organic and inorganic contaminants. In total 83 organic contaminants were found, e.g. well known priority pollutants such as endosulfan, hexachlorobenzene, DDT, hexachlorocyclohexane and their metabolites, which likely stem from the industrial manufacturing of organochlorine pesticides. Furthermore, several benzothiazole, dibenzylamine and dicyclohexylamine derivatives were detected, which indicated inputs from rubber producing facilities. Several of these compounds have not been reported as environmental contaminants so far. A comparison of organic contaminant and trace hazardous element concentrations in sediments with reported sediment quality guidelines revealed that adverse effects on benthic species are likely at all stations. The chemical assessment was combined with an investigation of macrobenthic diversity and community composition. Benthic organisms were completely lacking at the site with the highest trace hazardous element concentrations. Highest species numbers, diversity indices and abundances were recorded at the station with the greatest distance to the industrial area. Filter feeders were nearly completely lacking, probably leading to an impairment of the filter function in this area. This study shows that a combination of chemical and biological methods is an innovative approach to achieve a comprehensive characterization of industrial contamination, to evaluate associated risks for bottom dwelling consumers regarding sediment quality guidelines, and to observe related adverse effects on the benthic community directly in the field.

Ucides cordatus is an abundant mangrove crab in Brazil constructing burrows of up to 2 m depth. Sediment around burrows may oxidize during low tides. This increase in sediment-air contact area may enhance carbon degradation processes. We hypothesized that 1) the sediment CO2 efflux rate is greater with burrows than without and 2) the reduction potential in radial profiles in the sediment surrounding the burrows decreases gradually, until approximating non-bioturbated conditions. Sampling was conducted during the North Brazilian wet season at neap tides. CO2 efflux rates of inhabited burrows and plain sediment were measured with a CO2/H2O gas analyzer connected to a respiration chamber. Sediment redox potential, pH and temperature were measured in the sediment surrounding the burrows at horizontal distances of 2, 5, 8 and 15 cm at four sediment depths (1, 10, 30 and 50 cm) and rH values were calculated. Sediment cores (50 cm length) were taken to measure the same parameters for plain sediment. CO2 efflux rates of plain sediment and individual crab burrows with entrance diameters of 7 cm were 0.7–1.3 µmol m−2s−1 and 0.2–0.4 µmol burrows−1s−1, respectively. CO2 released from a Rhizophora mangle dominated forest with an average of 1.7 U. cordatus burrows−1m−2 yielded 1.0–1.7 µmol m−2s−1, depending on the month and burrow entrance diameter. Laboratory experiments revealed that 20–60% of the CO2 released by burrows originated from crab respiration. Temporal changes in the reduction potential in the sediment surrounding the burrows did not influence the CO2 release from burrows. More oxidized conditions of plain sediment over time may explain the increase in CO2 release until the end of the wet season. CO2 released by U. cordatus and their burrows may be a significant pathway of CO2 export from mangrove sediments and should be considered in mangrove carbon budget estimates.

The analysis of benthic food webs in mangrove forests is complicated by the lack of experimental investigations of consumer-diet discrimination factors (Δ 15 N and Δ 13 C) for most man- grove invertebrates. This study aimed to determine the fractionation of δ 13 C and δ 15 N between mangrove leaves and Episesarma singaporense and E. versicolor (Sesarmidae) for 90 d in Java, Indonesia. The consumption rates of both species and stable isotope fractionation of leaves from 5 plant species (Acanthus ilicifolius, Aegiceras corniculatum, Avicennia alba, Derris trifoliata, Rhi- zophora apiculata) were compared. Δ 15 N between R. apiculata leaves and muscle tissue was 5.0‰ for E. singaporense and 5.4‰ for E. versicolor after 50 d. δ 15 N of muscle tissue increased signifi- cantly after 50 d, most likely due to the internal recycling of nitrogen. δ 13 C did not change during the experiment, and Δ 13 C was 5.1‰ for E. singaporense and 4.1‰ for E. versicolor after 90 d. Leaves of D. trifoliata and R. apiculata were preferentially consumed, indicating their higher nutritive value. We concluded that (1) the discrimination values for mangrove crabs feeding on a leaf diet are much higher than previously assumed, which can most likely be explained by the selective assimilation of isotopic heavy carbon compounds and by metabolic cycling of non-essen- tial amino acids; (2) the frequently used average discrimination factors are inappropriate for the study of benthic food webs in mangrove forests with a high biomass of leaf-eating crabs; and (3) E. singaporense and E. versicolor can meet their nitrogen demand by assimilating nitrogen from R. apiculata leaves and by using internal reserves for at least 50 d.

At a meeting of world mangrove experts held last year in Australia, it was unanimously agreed that we face the prospect of a world deprived of the services offered by mangrove ecosystems, perhaps within the next 100 years. Mangrove forests once covered more than 200,000 km2 of sheltered tropical