Mangrove Matter Research Articles

Fatty acids and stable isotopes distribution in the mangrove dominated Parnaíba River Delta

Characterizing the origin and quality of the organic matter (OM) present in estuaries, as well as its export toward the ocean, is a key issue to better understanding the carbon cycle and its impact on global change. In this study, fatty acid markers and δ13C and δ15N values were used to characterize the particulate and sedimentary organic matter composition in the large mangrove-dominated Parnaíba Delta, known as a large reservoir of blue carbon. The presence of some long-chain fatty acids and other mangrove OM markers, such as the 18:2ω6 and 18:3ω3, indicated that the material produced in mangroves contributed largely to the particulate organic matter of water and sediments of the delta. Their presence in further oceanic stations also reveals the mangrove material is exported to the adjacent coastal ocean. In the main river channel, the higher contribution of 18:2ω6 in the sediments than in the mangrove regions, indicated an additional source related to anthropogenic activities, probably agriculture. The branched fatty acids found in the samples point to the presence of bacteria and indicated the intense modifications of the organic matter in the region, reflecting the heterotrophic nature of the delta. In addition, the predominance of saturated fatty acids in the delta suggests that the organic matter exported to the coastal ocean is dominated by detrital material.

Utilization of Mangrove Ecotourism as a Science Learning Resource for Junior High School Students

The research was carried out with the aim of finding out the use of mangrove ecotourism as a learning resource, because almost all regions in Indonesia manage mangrove ecosystem areas into ecotourism. The data collection technique uses proportional random sampling, with descriptive quantitative research methods. The research subjects used in this research process were the population of junior high school students and junior high school science teachers, with a sample of 118 students and 22 science teachers. The instrument used in this research is a questionnaire. The results obtained from the science teacher questionnaire stated that 80.8% of teachers had never integrated mangroves in the science learning process, reinforced by the results of the student questionnaire which stated that 83.2% of teachers had never presented mangrove material in the classroom. In this way, science teachers should change the way they deliver material using the Argument Driven Inquiry (ADI) learning model to make it easier for science teachers to utilize mangrove ecotourism as a learning resource through the stages of the learning model syntax.

Diet of hawksbill turtles (Eretmochelys imbricata) in the Gulf of California, Mexico

Abstract Hawksbill turtles (n = 56) in a foraging ground around Isla San Jose, Gulf of California, Mexico, were caught, measured, and their skin and scutes sampled. Tissue samples from putative prey species were collected from observed hawksbill feeding areas in the foraging ground. Measurements of each turtle's straight carapace length were used to estimate the average life stage of the population. Tissue samples were processed for stable carbon and nitrogen isotope analysis to estimate foraging habits of turtles in this location. The majority (96.4%) of measured individuals' straight carapace length fell in the size range considered to be juveniles. A Bayesian mixing model analysis of the δ13C and δ15N values of hawksbill skin and potential prey indicated that hawksbills consume primarily invertebrates and algae, with lesser contributions from seagrass and mangrove material. There was a positive linear relationship between turtle size and the δ13C values from scute samples, and an increase in the δ13C values of five individuals recaptured in subsequent years suggested a potential location shift from a pelagic habitat in the turtles' post‐hatching, earliest juvenile years to the nearshore foraging area around Isla San Jose in their later juvenile years.

Leaf consumption and experimental discrimination of stable isotopes between mangrove leaves and the tree-climbing crab (Brachyura: Sesarmidae: Aratus pisonii)

The mangrove tree-climbing crab Aratus pisonii (Sesarmidae) is one of the most abundant and iconic arboreal brachyurans in the Neotropics. Despite being traditionally regarded as an herbivorous consumer leaving visible rasping marks on Rhizophora mangle leaves, gut content analyses, field observations and experimental feeding trials also suggest facultative omnivory. In addition, there are still questions regarding the nutritional challenge of leaf consumption, particularly whether the relatively nutrient-poor mangrove leaf litter is assimilated when offered as the sole component of the diet. This study aimed to: 1) experimentally compare consumption rates of fresh (green) and senescent (yellow) Rhizophora mangle leaves during a 26 d experiment; 2) estimating stable isotope trophic discrimination of carbon and nitrogen between leaves and muscle tissue after a 58 d controlled feeding experiment with A. pisonii from the Southwestern Caribbean Sea (Atrato River Delta, Colombia). A. pisonii consumed a total of 17.11 ± 20.75 mg leaf dry wt (g crab wet wt) −1 d−1 of R. mangle leaves during the experimental trial. However, the consumption was greater for green leaves (12.05 ± 13.07 mg) than for yellow leaves (5.06 ± 13.85 mg). Our experimental estimates of mean ± SD TDFs (trophic discrimination factors) were Δ13C 5.4 ± 0.9‰ and Δ15N 3.9 ± 0.5‰, close to those suggested for other sesarmid crabs. These results can be used in future estuarine food webs studies from Neotropical mangrove habitats, and provide new insights into the importance of A. pisonii as a key herbivore converting low-quality mangrove material into nutritious secondary production (biomass), potentially linking primary producers with intermediate and top predators (both aquatic and terrestrial).

Pengolahan Sirup Buah Pedada (Sonneratia caseolaris) dan Keripik Daun Jeruju (Acanthus ilicifolius) di Desa Teluk Pambang Kecamatan Bantan Kabupaten Bengkalis

Community service activities are making processed products as various food products based on the potential of local plants by utilizing the fruit and leaves of mangroves (Sonneratia caseolaris) and (Acanthus ilicifolius) in Teluk Pambang Village. This activity has the aim of developing the business of processing pedada fruit syrup and jeruju leaf chips using mangrove raw materials from local potential with the objectives of: a) technological innovation of processing mangrove leaves and fruit as product raw materials; b) utilization of processed mangroves for food products that have economic value; c) manufacture of processed mangrove products as an altervative to increase people’s income; d) products packaging; and e) increasing the capacity of business management and marketing of processed products from mangroves. The method used is counseling and practice of processing pedada fruit syrup and jeruju leaf chips. The target community in this activity is the mother of the KPM BELUKAP group in Teluk Pambang Village. The results of the activity show that the community strongly agrees with this activity, being involved in practicing the processing of pedada fruit syrup and jeruju leaf chips as an alternative to increase income. Economic analysis of processed pedada fruit syrup is IDR252,000.00,- and jeruju leaf chips are IDR622,400.00,-. After is this service activity shows that there is a culinary business opportunity that is made from mangroves and can be used by the Teluk Pambang Village community to develop mangroves which were originally only for the tourism sector, as well as to cultivate and preserve mangroves.

Carbon stock of disturbed and undisturbed mangrove ecosystems in Klang Straits, Malaysia

Ecosystem carbon stocks were compared in three island mangrove forests, subjected to different anthropogenic stresses, close to Port Klang in Selangor State on the west coast of Peninsular Malaysia. Carbon stocks in living biomass, litter, deadwood and soil were quantified, and the carbon isotopic signature in mangrove soils was also measured, to estimate their carbon source. We hypothesize that carbon stock would be more readily available in undisturbed mangroves. The results indicated that, in general, soil organic carbon pool comprised the majority of the ecosystem carbon stock, while dead organic matter made a negligible contribution. The highest ecosystem carbon stock was measured in the permanent undisturbed mangrove reserve on Pulau Klang. Carbon isotope data revealed that disturbed mangroves in Pulau Ketam had a more enriched δ13C signature of soil samples compared to the other two sites. The soil organic carbon in Pulau Ketam was mostly derived from mangrove materials (92.8%). The results suggested that the organic carbon accumulated in the soils was not only regulated by the burial of mangrove-derived organic carbon, but also the site conditions.

Leaf-litter consumption slows crab growth but transforms mangrove food chains

Leaf litter consumption has implications for growth and nutrient balances of mangrove crabs and mangrove trophic pathways. This study (1) addressed the impact of leaf litter quality and quantity on crab life history and growth, and (2) proposed keystone roles of crabs in mangrove material fluxes. Estimates of crab standing stocks, growth, and carbon and nitrogen mass balances were obtained for a field population of Parasesarma messa, a primary consumer of leaf litter in Queensland mangroves. P. messa exhibited slow growth and individuals took >>4 yr to reach maximum size. Females appeared to breed once per year with high reproductive effort relative to other crabs. An apparent trade-off between growth and reproduction in the dry-wet transition season was caused by a shortage of available leaf litter. A nitrogen mass balance indicated that the population ingested twice the amount of nitrogen that could be supplied by leaf litter. Assuming mortality was mainly due to predation, the estimated loss to predators (28 kg ha-1 yr-1) supported a hypothesis that crab consumption by fish short-circuits mangrove food chains. Faecal production by crabs (0.48 Mg C ha-1 yr-1 and 0.03 Mg N ha-1 yr-1) represents a substantial contribution to deposit-feeding food chains. P. messa is a keystone species whose impact on ecosystem processes is large relative to its abundance and biomass.

Higher soil organic carbon sequestration potential at a rehabilitated mangrove comprised of Aegiceras corniculatum compared to Kandelia obovata

The present study compared the ecosystem organic carbon (OC) stocks and soil OC sources between two 12-year-old monospecific mangrove sites comprised of different species (Kandelia obovata in tree form and Aegiceras corniculatum in shrub form). We tested whether the carbon sequestration performance following rehabilitation varied with plantation of species in different forms and whether mangrove vegetation sequestrate OC more rapidly than soil pool. The results showed that mangrove rehabilitation increased the ecosystem OC stock relative to that of a non-vegetated bare flat. The accumulation of soil carbon was accompanied by increased soil total nitrogen contents and decreased δ13C values of soil OC, indicating that the increases in OC and TN contents were a function of accumulation of 13C-depleted mangrove materials in the soil. The sequestrated OC over the 12 years was considerably less in soil than in biomass at each mangrove site, suggesting that mangrove vegetation contributes more rapidly than the soil to ecosystem OC sequestration following rehabilitation before the vegetation has reached maturity. Compilation of the carbon stocks from worldwide rehabilitated mangrove forests with various ages further supports this finding. The K. obovata site had an apparently higher biomass OC stock but less OC in the soil than those at the A. corniculatum site. There was a higher standing leaf litter stock on the forest floor and more mangrove materials incorporated into the top 15 cm soil at the A. corniculatum site. These results suggested that the two rehabilitated mangrove sites had different development trajectories of both biomass and soil OC sequestration. Moreover, the performance of ecosystem carbon sequestration was related to plantation of different mangrove species. These carbon sequestration feature of rehabilitated mangrove forests therefore deserve attention in future rehabilitation programs to promote carbon sequestration performance.

Cellulose digestion abilities determine the food utilization of mangrove estuarine crabs

Food utilization and cellulose digestion abilities of six crab species were examined to clarify the mechanisms driving trophic and spatial segregation among species within a mangrove estuary on the Urauchi River, Iriomote Island, southern Japan. Dual stable isotope signatures (δ13C and δ15N) of dominant crab species inhabiting three microhabitats (bare sandy flat, bare muddy flat and mangrove forest) showed that most crab species, such as the soldier crab Mictyris guinotae and fiddler crab Gelasimus jocelynae, primarily assimilated microphytobenthos (MPB), while the sesarmid crab Parasesarma bidens inside the mangrove forest substantially utilized cellulose-rich mangrove detritus and leaf litter. Analyses of the chemical properties of sediment organic matter indicated that it comprised mainly mangrove detritus, which was more abundant on the muddy flat and in the forest compared to the sandy flat. In contrast, the standing stocks of MPB were at consistently low levels in each microhabitat, particularly inside the mangrove forest than on the bare flats. The enzyme assay revealed that P. bidens exhibited much higher cellulase activity, enabling the species to utilize refractory mangrove materials, whereas the other crab species with lower cellulase activity were highly dependent upon nutritious and easily degradable MPB, although the amount of the latter was largely limited in the mangrove estuary. These findings suggested that the assimilation efficiency of cellulose-rich plant materials as a carbon source, dependent upon the level of cellulase activity, essentially controls trophic and spatial segregation among crab species in the mangrove estuary. Given the greater biomass of plant detritus, it is likely that P. bidens plays an integral part in establishing the detritus food chain in the mangrove ecosystem through the effective digestion/assimilation of cellulose materials.

Resource use by and trophic variability of Armases cinereum (Crustacea, Brachyura) across human-impacted mangrove transition zones.

In Florida, resource use patterns by Armases cinereum (Armases), a highly abundant crab in coastal habitats, may serve as important indicators of habitat condition. Here we investigated feeding patterns of Armases in coastal palm scrub forest to intertidal mangrove forest transition zones (transitions) as well as the relationship between habitat disturbance and Armases’ trophic position across three pairs of geographically separated populations in Tampa FL, USA. Each pair of sites represented an unmodified “natural” location as well as a “disturbed” location lacking upland terrestrial palm scrub forested habitat. Laboratory experiments established a baseline understanding of feeding preference of Armases offered strictly mangrove material as well as sources abundant at the transition. In-situ feeding behavior was examined using MixSIAR mixing models with δ13C and δ15N stable isotope tracers. Armases showed a strong preference for consuming partially-decomposed mangrove material from Avicennia germinans and an equally strong preference for Iva frutescens. Armases also displayed predatory behavior under laboratory conditions, confirming omnivory in the presence of mangrove material. Stable isotopes revealed a pattern of elevated trophic position of Armases in disturbed habitats over paired natural locations. Diet reconstruction provided coarse resolution of in-situ feeding and results show high spatial variation: in natural habitats, Armases appears to rely heavily upon upland plant material compared to disturbed habitats where it may consume more animal prey. Combined, these findings support that Armases trophic position and diet may indicate habitat quality in mangrove transitions in the southeastern United States.

Complete chloroplast genome of a Mangrove Natural Hybrid, Rhizophora × lamarckii

Rhizophora × lamarckii is a natural hybrid of R. apiculata and R. stylosa, and it is also an endangered mangrove material in China with the exclusive location in Hainan Island. In this paper, we reported and characterized the complete chloroplast genome sequence of R. × lamarckii by assembling from short reads generated using Illumina sequencing. Total chloroplast genome size was 164,325 bp, including inverted repeats (IRs) of 26,325 bp, separated by a large single copy (LSC) and a small single copy (SSC) of 92,433 bp and 19,244 bp, respectively. A total of 121 genes, including 42 tRNAs, eight rRNAs, and 81 protein-coding genes, were identified. The GC content of R. × lamarckii is 34.67%. Phylogenetic analysis using the maximum likelihood algorithm showed that R. × lamarckii is sister to a clade with four species in the order Malpighiales.

Tropical peat debris storage in the tidal flat in northern part of the Bengkalis island, Indonesia

Currently, CO2 emissions from the peat is a global problem. Particularly, it is caused by biodegradation of dry peat or peat fire. In the northern coast of Bengkalis island, peat is flowing out due to coastal erosion, and mangrove tidal flat is formed the west coast by peat. The core samples of the mangrove have been confirmed that the clay layer and the peat layer are in mutual layers, and decomposition was inhabited because these sandwiched peat soils was an anoxic state. In the northern part of the Bengkalis island, peat is sandwiched in the clay layer. Biodegradation can be suppressed by being sandwiched, there is a possibility of suppressing the amount of peat decomposed by providing a place to store peat in tidal flats. In this research, we examined the degree of decomposition of peat accumulated in the mangrove tidal flats and confirmed that decomposition was suppressed for the peat soils in the tidal flat under mangrove trees, we call it “sandwich effect”. The peat materials in deeper layer came from originally peat swamp forest, however, the surface organic materials were thought to be come from mangrove materials. Considering the change from 1988 to 2015, the carbon fixation rate by mangrove is 1.7 × 103 tC km-2 yr-1, the carbon accumulation rate by accumulation of secondary deposition of peat was 7.4×103 tC km-2 yr-1.

Isotopic evidence of subtle nutrient enrichment in mangrove habitats of Golfo Dulce, Costa Rica

AbstractMangroves are of great ecological and socio‐economic importance, yet they are under threat from urban development on the southern Pacific coast of Costa Rica. To test for possible nutrient‐related impacts, we compared water‐column nutrient concentrations, C and N stable isotope values and other environmental variables between mangroves with known sewage loading (three “nutrient loaded” locations) and those without such loading (three “reference” locations). Instantaneous nutrient concentrations were low at all locations, Secchi depth was greater at reference locations, and chlorophyll concentrations were higher at nutrient loaded mangroves. Suspended matter did not vary between reference and nutrient loaded mangroves, and nor did bivalve and algal δ13C and δ15N values. Enrichment of δ15N and δ13C of red mangrove leaves at the nutrient loaded locations is attributed to pulsed inputs of materials that were not detected in the instantaneous nutrient data. We provide evidence of isotopic enrichment at nutrient loaded locations from mangrove material and recommend that adequate waste water treatment be carried out on all anthropogenic discharges into this vulnerable marine system.

Small-scale variability in geomorphological settings influences mangrove-derived organic matter export in a tropical bay

Abstract. Organic matter (OM) exchanges between adjacent habitats affect the dynamics and functioning of coastal systems, as well as the role of the different primary producers as energy and nutrient sources in food webs. Elemental (C, N, C : N) and isotope (δ13C) signatures and fatty acid (FA) profiles were used to assess the influence of geomorphological setting in two climatic seasons on the export and fate of mangrove OM across a tidally influenced tropical area, Gazi Bay (Kenya). The main results indicate that tidal transport, along with riverine runoff, plays a significant role in the distribution of mangrove organic matter. In particular, a marked spatial variability in the export of organic matter from mangroves to adjacent habitats was due to the different settings of the creeks flowing into the bay. Kinondo Creek acted as a mangrove retention site, where export of mangrove material was limited to the contiguous intertidal area, while Kidogoweni Creek acted as a flow-through system, from which mangrove material spreads into the bay, especially in the rainy season. This pattern was evident from the isotopic signature of primary producers, which were more 13C-depleted in the Kinondo Creek and nearby, due to the lower dilution of the dissolved inorganic carbon (DIC) pool, typically depleted as an effect of intense mangrove mineralisation. Despite the trapping efficiency of the seagrass canopy, suspended particulate OM showed the important contribution of mangroves across the whole bay, up to the coral reef, as an effect of the strong ebb tide. Overall, mixing model outcomes indicated a widespread mixed contribution of both allochthonous and autochthonous OM sources across Gazi Bay. Moreover, FAs indicated a notable contribution of brown macroalgae and bacteria in both sediment and suspended pools. These results suggest that ecological connectivity in Gazi Bay is strongly influenced by geomorphological setting, which may have far-reaching consequences for the functioning of the whole ecosystem and the local food webs.

Variability in δ<sup>13</sup>C and δ<sup>15</sup>N Stable Isotope Signatures in Mangrove Ecosystem of Hainan, China

δ13C and δ15N dual stable isotope signatures were used to determine the impact of mangrove materials and other organic carbon sources to fish, crab (Scylla paramamosain) and land use communities in an ecologically significant mangrove ecosystem of Hainan Island in the southern part of China. The mean δ13C values of the leaves ranges from-36.72 to 32-89‰ suggesting that mangrove trees follow the C3 type photosynthetic pathway. The analyzed specimen on the crab was found to have δ13C and δ15N values ranging from-21.41 to-19.74‰ and 7.60 to 7.78‰ respectively, and that of fish from-12.92 to-13.02‰ and 7.01-7.53‰. Crabs showed low δ13C values as compared to the fish. The δ13C revealed that the mangrove crabs directly relied on the mangrove materials. The variation of carbon and nitrogen concentration respectively showed considerable difference in the ultimate sources of carbon and trophic level. It was observed that mangrove leaves contribute to the food sources. The land usage that contributes to pollution and the nutrient distribution reflects anthropogenic loading of nitrogen in the mangrove area. Thus, this calls for the need to conserve the mangrove ecosystem at Hainan.

Feeding ecology of mangrove crabs in Cameroon

The feeding ecology of several species of mangrove crabs was studied in Cameroon mangrove forest through tethering experiments and gut analyses from September 2010 to March 2011. Field observations were two-fold: to investigate mangrove propagules predation and feeding preferences of mangrove leaves. Feeding preference was determined on fresh and senescent leaves of Laguncularia racemosa, Avicennia germinans and Rhizophora species. Propagule predation was investigated on Rhizophora mangle, Rhizophora harrisonii and Rhizophora racemosa. In the laboratory, gut content analysis was done on Metagrapsus curvatus, Sesarma huzardi, Sesarma elegans, Sesarma alberti, Goniopsis pelii and Grapsus grapsus to assess their natural diets. The field observations suggest that 65.9% of the propagules studied was predated, 71.3% of the leaves was damaged. Mangrove material was the main component of crabs diet, it constituted 45.4% of Metagrapsus curvatus diet, 55% Sesarma elegans diet, 62.5% Sesarma alberti, 65.9% Goniopsis pelii diet, 47.8% Sesarma huzardi diet and 37.3% Grapsus grapsus diet. Damage on young mangrove trees was highly correlated to the number of crabs on trees (r2 = 0.75). The high damage rate of mangrove materials indicate that crabs play a significant ecological role in the functioning of the mangrove ecosystem, by affecting mangrove recruitment and biogeochemical functioning.

Importance of Mangrove Carbon for Aquatic Food Webs in Wet–Dry Tropical Estuaries

Mangroves are traditionally considered to provide important nutrition to tropical estuarine consumers. However, there is still controversy about this, and the extent and importance of these inputs are largely unquantified. In particular, there is no information for food webs of small estuaries that dominate wet–dry tropical coasts, where freshwater inflow is intermittent, leading to highly seasonal inputs of nutrients from terrestrial systems. Since the relative importance of the different sources depends on the type and extent of different habitats and on hydrological and topographic conditions, results from other regions/type of systems cannot be extrapolated to these estuaries. Here, δ13C is used to determine the importance of mangrove-derived carbon for Penaeus merguiensis (detritivore; shrimp), Ambassis vachellii (planktivore; fish), and Leiognathus equulus (benthivore; fish) from six small wet–dry tropical estuaries that differ in mangrove (C3) cover and in type of terrestrial vegetation adjacent to the estuary. Bayesian mixing models confirmed that mangrove material was important to consumers in all estuaries. There was a gradient in this importance that agreed with the extent of mangrove forests in the estuaries, as C3 sources were the most important contributors to animals from the three estuaries with the greatest (>40 %) mangrove cover. There was also evidence of incorporation of C3 material for the three estuaries with lower (<30 %) mangrove cover. Since these latter estuaries had no adjacent terrestrial C3 forests, the detected C3 influence can only be of mangrove origin. This shows that mangroves are important contributors to these food webs, underlining the importance of mangroves in supporting estuarine nursery ground value and fisheries productivity.

Quantity and quality of organic matter (detritus) drives N2 effluxes (net denitrification) across seasons, benthic habitats, and estuaries

N2 flux rates (net denitrification) were measured over a diel cycle, seasonally, in 12 benthic habitats across three warm temperate Australian coastal systems. Dark N2‐N fluxes were strongly controlled by sediment oxygen demand (SOD) across the 3 estuaries, 4 seasons, and 12 benthic habitats (r2 = 0.743; p &lt; 0.001; n = 142; slope = 0.0170). However, some of the slopes differed significantly between seasons and among estuaries and habitats, and all of the slopes were correlated with the δ13C values and C:N ratios of sediment organic matter. Ternary mixing diagrams with the contribution of algal, seagrass, and terrestrial/mangrove material to sediment organic matter showed that habitats, seasons, and estuaries dominated by a mixture of seagrass and algal material had the lowest slopes, and slopes increase as habitats, seasons, and estuaries have an increasing contribution from terrestrial/ mangrove material. Overall, the slopes of dark N2 fluxes versus SOD were low compared to previous studies, most likely due to either, or a combination of, the C:N ratio of the organic matter, the mixture of C:N ratios making up the organic matter, the structure of the organic matter, and/or the SOD rates. This study demonstrated that it is not only the quantity but also the type (quality), and maybe the mixture, of organic matter that is an important control on denitrification. As such, rapid global changes to detrital sources to coastal systems due to losses of mangrove, seagrasses, and saltmarshes, and associated increases in algae and macrophytes, are also expected to impact system level losses of nitrogen via denitrification.

Food sources of macro-invertebrates in an important mangrove ecosystem of Vietnam determined by dual stable isotope signatures

Dual stable isotope signatures (δ13C and δ15N) were applied to determine the contribution of mangrove materials and other organic carbon sources to the invertebrate community in an ecologically important mangrove ecosystem of Vietnam. We have analyzed 181 specimens of 30 invertebrate species and found δ13C and δ15N ranging from −14.5 to −26.8‰ and from 1.3 to 12.1‰, respectively. From taxa measured for stable isotopes, polychaete, gastropods, bivalves, and grapsid crabs living in mangrove forest showed relative low δ13C values, while fiddler crabs inhabiting in the land–water ecotone showed the highest δ13C values. The δ13C showed that just a few mangrove inhabitants directly relied on the mangrove materials. The wide ranges of δ13C and δ15N signatures indicated that the invertebrates utilized heterogeneous diets, comprising benthic microalgae, marine phytoplankton, particulate organic matter, sediment organic matter, mangrove detritus, and meiofauna and rotten animal tissues as the supplemental nutrient food sources. Moreover, the significant correlation between δ13C values and body sizes of invertebrates showed that snails Littoraria melanostoma and Terebralia sulcata, bivalve Glauconome virens, and portunid crab Scylla serrata exhibited ontogenetic shifts in diets. The present study showed that adjacent habitats such as tidal flat and mangrove creeks seem to contribute an important microalgal food resource for invertebrates and highlighted the need for conservations of mangrove forests and the adjacent habitats.

Sources of nutrition supporting juvenile penaeid prawns in an Australian dry tropics estuary

Prawn fisheries are among the main sources of income in several tropical countries, where juveniles of many species inhabit estuarine wetlands. Although plants in these wetlands are considered to be essential food sources for juvenile prawns, some studies suggest that wetland producers are of limited importance. In the present study, δ13C and δ15N were used to identify differences in diet between penaeid species and size classes, and to determine if terrestrial wetland producers are important for nutrition. Two estuarine floodplain pools were sampled: one surrounded by mangroves and one surrounded by salt marsh. There were differences in diet between species and size classes. As mangrove δ13C (–29.7 to –26.3‰) was very different from salt marsh δ13C (–16.3 to –15.4‰), the importance of these producers was examined by comparing the isotopic composition of the prawns between sites and by using the IsoSource model. Although aquatic sources were the most important, salt marsh grass was also a significant contributor, supporting the hypothesis that these wetland producers are important for juvenile prawn nutrition. There was no evidence that mangrove material was of major importance for any species, suggesting that mangrove productivity is not the primary reason for the occurrence of penaeid prawns in mangrove habitats.