Control by fiddler crabs (Uca vocans) and plant roots (Avicennia marina) on carbon, iron, and sulfur biogeochemistry in mangrove sediment (original) (raw)
Related papers
Biology, 2016
In mangrove ecosystems, litter fall accumulates as refractory organic carbon on the sediment surface and creates anoxic sediment layers. Fiddler crabs, through their burrowing activity, translocate oxygen into the anoxic layers and promote aerobic respiration, iron reduction and nitrification. In this study, the effects of four species of fiddler crabs (Uca triangularis, Uca rosea, Uca forcipata and Uca paradussumieri) on organic content, water content, porosity, redox potential and solid phase iron pools of mangrove sediments were investigated. In each crab's habitat, six cores down to 30 cm depth were taken from burrowed and non-burrowed sampling plots. Redox potential and oxidized iron pools were highest in surface sediment, while porosity, water and organic content were higher in deeper sediment. Reduced iron (Fe (II)) and redox potential were significantly different between burrowed and non-burrowed plots. Crab burrows extend the oxidized surface layer down to 4 cm depth and through the oxidation effect, reduce the organic content of sediments. The effects of burrows varied between the four species based on their shore location. The oxidation effect of burrows enhance the decomposition rate and stimulate iron reduction, which are processes that are expected to play an important role in biogeochemical properties of mangrove sediments.
The role of reactive iron in long-term carbon sequestration in mangrove sediments
Purpose Despite occupying only 0.5% of the global coastal ocean, mangroves play a disproportionately large role in the capture and retention of atmospheric carbon dioxide as organic carbon (OC) in its sediments. However, the capacity of mangrove sediments to store high amounts of OC has never been explained mechanistically. This study elucidates the role of reactive iron (Fe R) in long-term carbon sequestration in mangrove sediments. Materials and methods Sediment samples of up to 1 m in depth were collected from six selected mangrove areas across the Philippines. The samples were characterized using X-ray diffraction (XRD) and X-ray fluorescence (XRF). A citrate-bicarbonate-dithionite reduction procedure was employed to extract Fe R from the sediments. The OC concentration and δ 13 C signatures before and after Fe R extraction were determined using a dichromate oxidation technique and isotope ratio mass spectrometry (IRMS), respectively. Results and discussion XRD diffractograms showed that the mangrove sediment samples varied in terms of mineralogical characteristics, which reflected their different parent materials. It was found that the OC concentration increased exponentially (OC = 8.38e 0.37FeR ; R 2 = 0.88; p < 0.0001) with increasing Fe R concentration. δ 13 C signatures of Fe R-associated OC revealed that Fe R preferentially preserved terrestrial over marine-derived organic matter. Finally, Fe R was estimated to coprecipitate with up to 5.44 × 10 12 g OC in mangrove sediments per year. Conclusions The findings of this study suggest that Fe R is responsible for the preservation of OC, thus making mangrove sediments a Bgiant rusty sponge^ for carbon. This mechanistic understanding of the long-term carbon storage in mangrove sediments could help draft better strategies for blue carbon initiatives that include the mangrove ecosystems.
CRABS ENGINEERING EFFECTS ON SOIL ORGANIC MATTER AND NUTRIENTS FLOW IN SUBTROPICAL MANGROVES FOREST
Burrowing activities of crabs has potential effect on biogeochemical cycles in sediments. A field study was conducted in the Sashiki Bay (Okinawa Island, southern Japan) to compare engineering impact of ocypodid Uca vocans and sesarma crabs Perisesarma bidens on the distribution of organic matter and nutrients processes in intertidal sediments. The organic carbon content tended to be higher in burrows than adjacent surface sediments of both crab species. Burrowing by U. vocans resulted in a massive release of NO 3 to the burrow sediments as compared to that of P. bidens. In contrast, an opposite effect on the NH 4 + concentration was observed in both crab burrows and their adjacent surface sediments. These results suggest that physical structures and activities of ocypodid and sesarmid crabs may lead to a significantly contrasting influence on the organic matter and nutrient distribution in the subtropical mangrove forest.
Effects of seasons and burrowing crabs (Uca spp.) on sediment nutrients and mangrove sapling growth
The influence of fiddler crabs (Uca spp.) and seasons were investigated in a controlled field experiment with emphasis on sediment nutrients and the growth and productivity of Kandelia obovata saplings in a subtropical mangrove forest. Three treatments comprising of experimental exclosures, enclosures and disturbance control were established on an open flat in the middle intertidal zone of the mangrove. Uca crabs were removed from the exclosure treatments and allowed in the enclosure and disturbance controls. Nine K. obovata saplings were planted in each treatment and the conditions were monitored monthly. Growth parameters (sapling height increase and the number of new leaves produced) and the nutrient status were measured seasonally. In all seasons, the NH 4 + concentration was significantly higher in sediments of the exclosure (crab removal) than in the enclosure and disturbance controls (with crabs). In the presence of crabs, NO-3 levels were twofold greater and the amount of PO 4-3 was significantly lower during the autumn. Sapling height increase was not significantly different between treatments, but the number of new leaves produced was significantly higher in the saplings grown in the enclosure and disturbance controls than in the exclosure. The burrowing impact by fiddler crabs was more pronounced during the autumn period and significantly influenced sediment nutrient conditions and K. obovata leaf production, but had limited impact on sapling height elongation.
Journal of Coastal Research, 2008
MACHADO, W.; SANTELLI, R.E.; CARVALHO, M.F.; MOLISANI, M.M.; BARRETO, R.C., and LACERDA, L.D., 2008. Relation of reactive sulfides with organic carbon, iron, and manganese in anaerobic mangrove sediments: implications for sediment suitability to trap trace metals. Journal of Coastal Research, 24(4C), 25-32. West Palm Beach (Florida), ISSN 0749-0208.
Wetlands Ecology and Management, 2018
The land crab Cardisoma guanhumi is one of the most common species in mangroves of the American Atlantic coast and Caribbean islands however, studies of its effects on the physical and chemical soil properties are scarce. This study compares specific physicochemical properties of soil between C. guanhumi burrows (B) and adjacent zones (AZ), and provides the first insights on their role as an ecosystem engineer in mangroves. The study was conducted in an estuarine system dominated by Rhizophora mangle, located at the Río Chico estuary, Miranda state of Venezuela. Random soil samples were taken digging each burrow until reaching the bottom and at the same depth for AZ. Data analysis was carried out using Bayesian inference. Credible mean differences between B and AZ, were found for sand (B = 26.53 ± 10.76, AZ = 17.25 ± 5.7%), silt (B = 73.16 ± 10.77, AZ = 82.42 ± 5.69%), pH (B = 8.71 ± 0.36, AZ = 9.12 ± 0.30), soil organic matter (SOM, B = 0.43 ± 0.21, AZ = 0.17 ± 0.06%), total N (TN, B = 786 ± 232, AZ = 529 ± 107 lg g-1), Mg (B = 4.42 ± 0.60, AZ = 3.48 ± 0.71 cmol c kg-1) and K (B = 0.12 ± 0.05 AZ = 0.06 ± 0.02 cmol c kg-1). Chemical variables as SOM, K, Mg and TN showed the highest values of effect size ([ 1.4). With the exception of the pH, all chemicals variables-which were different between B and AZ-showed strong and decisive evidences of correlations with SOM. When SOM variable was controlled, the relationships between pH-TN, TN-K and Mg-K decreased, even though the correlation evidence between each pair remained. Differences in chemical contents found in B respect to AZ suggest that the activities of C. guanhumi (feeding, moulting, excretion and defecation) within their burrows promote the spatial heterogeneity of mangrove soils.
The government of Saudi Arabia launched the Jazan Economic City (JEC) at Baish near Jezan city in 2006. However, there is a concern that immense industrial and urban development at JEC will seriously impact the coastal mangrove habitats. To explore the related environmental stresses on mangrove forests near JEC, the present study was conducted at three locations characterized as one close to an industrial port, one close to shrimp aquacultures, and one further from immediate human impacts: (1) to assess the vertical distribution of the sediment bulk density (SBD), sediment organic carbon (SOC) concentration, and SOC density in two polluted mangrove (Avicennia marina) locations in comparison with a non-polluted location along the southern Red Sea coast of Saudi Arabia; and (2) to estimate the SOC pool and carbon sequestration rate (CSR) of these locations. We hypothesise that each of the above-mentioned parameters varied between the polluted and non-polluted locations. In total, 400 sediment samples were collected and analysed to determine the SBD, the SOC concentration, density and pool, and the CSR, to reveal significant variation between the polluted and non-polluted mangrove locations in terms of the total mean values of the SBD, the SOC concentration, density and pool, and the CSR. An increase in SBD with a decrease in concentration and density of SOC is evident with an increase in depth at both polluted and non-polluted mangrove locations. The SOC pool at the non-polluted location (11.5 kg C m −2 ) is significantly (p < 0.05) larger than the SOC pool at the polluted locations (9.9 kg C m −2 ). Similarly, the average CSR at the non-polluted location (5.1 g C m −2 yr −1 ) is significantly (p < 0.001) greater than the average CRS at the polluted locations (4.4 g C m −2 yr −1 ). Thus, there is an urgent need to implement climate mitigation projects in order to manage and restore the mangrove ecosystems along the coastal regions of Saudi Arabia, and protect and conserve the present SOC pools.
Nutrient dynamics in mangrove crab burrow sediments subjected to anthropogenic input
Bioturbation by burrowing macroinvertebrates has a major impact on sediment properties, pollutant redistribution, and biogeochemical cycling. We assessed the impact of bioturbation on the nutrient dynamics and organic matter of sediments receiving anthropogenic inputs in the Manko wetland, located in southern Okinawa, Japan. We compared sediments that were and were not subjected to the activities of the tidal-flat crab Helice formosensis. The fatty acid composition of sediments indicated that different sources contributed to the organic matter profile. Agricultural and domestic waste discharge seemed to induce a high amount of green macroalgae and bacteria in the tidal flat. Sediments without crabs exhibited 2.1-2.4× more NH 4 -N release, which was associated with a low C/N ratio during the summer. In the crab burrow sediments, NO 3 -N concentrations were 1.4-1.9× more pronounced during winter. A significant correlation existed between NO 3 -N and NO 2 -N concentrations in sediments of the burrow chamber (r = 0.837, p b 0.02) and the mixed zone of burrow opening shaft and chamber (r = 0.885, p b 0.01). We suggest that burrow wall sediments provide ideal conditions for nitrate reduction (denitrification). H. formosensis thus contributes to balancing the effects of anthropogenic inputs by removing nitrogen loads in sediments.
Review: Biogeochemical process in mangrove ecosystem
International Journal of Bonorowo Wetlands
The mangrove ecosystem, one of the unique and distinctive aquatic ecosystems, is located in the tidal areas of the coast coastal areas in the tropics and subtropics. Mangrove ecosystems have many ecological, environmental, and social benefits. Mangrove forests have the potential to become a potential resource. This review aims to determine the process and function of the biogeochemical cycle in the mangrove ecosystem. The research method used in this research is descriptive qualitative research methods and tends to use inductive analysis. The biogeochemical cycle acts as a cycle that cannot be separated from the mangrove ecosystem. Biogeochemistry is the process of circulating chemical elements or compounds that occur repeatedly and continuously. Biogeochemistry plays a role in maintaining environmental stability and maintaining life on earth. The biogeochemical cycle consists of energy flow and nutrient cycling. Energy flows consist of food chains and food webs. The nutrient cycles include water, carbon, nitrogen, phosphorus, and sulfur. Various chemical elements resulting from the cycle process are needed to survive living things in the mangrove ecosystem.