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Cong, N.V. and Thao, H.V., 2023. Farming practices and environmental quality of integrated mangrove-shrimp farming systems in Tra Vinh province, Vietnam. Journal of Coastal Research, 39(4), 643–652. Charlotte (North Carolina), ISSN 0749-0208. Integrated mangrove-shrimp farming (IMSF) systems play a pillar role in environmental protection and deliver significant livelihood for communities in coastal areas. Identifying farming practices and environmental quality could improve mangrove forest ecosystem management and conservation. Therefore, practices of 30 households in the IMSF models were investigated. Also, surface water samples in the IMSF models and neighbouring rivers and sediment samples in the IMSF systems in the Long Khanh Mangrove Forest Reserve Area, Long Khanh commune, Duyen Hai district, and Tra Vinh province were collected. The results indicated that average mangrove coverage proportion of interviewed households in IMSF systems was 13% lower than the minimum required by the provincial government (55%). The productivities of shrimp and crab in IMSF systems were 45.86–75.38% and 22.81–60.65% lower than the IMSF systems in the Vietnamese Mekong Delta, respectively. Of all households, 13.33% directly discharged dredged sediment to surrounding rivers. Dissolved oxygen (DO), total suspended solids (TSS), and NH4+ values measured in water-distributed rivers were intolerable to permissible levels per the national standard, posing risks for aquacultural activities and coastal environmental protection as well, while these parameters in the IMSF ponds were in acceptable ranges. These Fe values were 3.50 fold and 1.16 fold higher for the IMSF ponds and adjacent rivers, respectively, than the national standard, but no significant discrepancy was revealed between Fe concentration in ponds and rivers. The present study also showed robustly reliable evidence that the concentration of trace elements, toxicity, persistent organic parameters, oil and grease, and coliform were consistently lower than the allowable degree of the national standard. This study suggests (i) increasing the ratio of mangrove forest coverage, (ii) reorganizing the annual IMSF pond renewal schedule, (iii) intervening techniques reducing total Fe concentration, and (iv) monitoring environmental quality in IMSF systems during and after dredging mangrove-shrimp ponds. [ABSTRACT FROM AUTHOR]

Zhang, Y.; Yan, S.; Wang, W., and Wang, M., 2021. Habitat use by fish across tidal cycles in a tropical estuarine mangrove ecosystem (Dongzhaigang Bay, Hainan, China). Journal of Coastal Research, 37(1), 156–167. Coconut Creek (Florida), ISSN 0749-0208. Mangroves wetlands are recognized as nursery areas for large numbers of marine organisms. Yet, many properties of this nursery function remain poorly understood. In this study, the seasonal use of a tropical mangrove bay by fish assemblages over tidal cycles was investigated in 2009. Fish were sampled using centipede nets from three sites (located in the mouth, middle, and top of the bay) at Dongzhaigang Bay, Hainan, China. At each site, three replicates were sampled from each of the three different habitat types (i.e. vegetated area, creek, and mudflat). A generalized linear mixture model was used to explore the spatial and temporal variations in fish assemblages. The results showed that fish species richness, abundance, and biomass per sampling unit were significantly lower in the vegetated areas and mudflats than in the creeks. In the vegetated areas, fish species richness, abundance, and biomass per sampling day were significantly higher during spring tides than during neap tides. However, a similar pattern was not found both along the creeks and on the mudflats. In addition, tidal height showed a positive effect on biomass per sampling unit, especially in the vegetated areas; meanwhile, effects on species richness and abundance were not significant. The results indicate that larger tidal amplitude could support more fish (both richness and abundance) in the vegetated areas, which might occur because larger tidal amplitude provides fish with access to more habitats. These results provide basic knowledge related to mangrove management at an important fish nursery ground. [ABSTRACT FROM AUTHOR]

Loría-Naranjo, M.; Sibaja-Cordero, J.A., and Cortés, J., 2019. Mangrove leaf litter decomposition in a seasonal tropical environment. Journal of Coastal Research, 35(1), 122–129. Coconut Creek (Florida), ISSN 0749-0208. Seasonal changes in rainfall might have an impact on the decomposition of mangrove leaf litter. This study analyzed the influence of weather conditions (season) on the decay rate, nitrogen, and phosphorus content as a decomposition indicator of leaf litter of Rhizophora racemosa. These measurements were taken at two sites in the Térraba–Sierpe National Wetland (TSNW) South Pacific, Coasta Rica, in 2013. The dry and wet season decay constants were similar and fast (k = 0.012 day–1). Decay constants were positively associated with salinity and water temperature (p <0.10). Moreover, season had an effect on the leaf litter nitrogen (high in dry season) and phosphorus content (high in rainy season). The effect of decomposition time on nitrogen and phosphorus content varies between sites. Leaf litter from R. racemosa acts as a substrate that releases nutrients to the ecosystem, contributing to carbon, nitrogen, and phosphorus budgets. The similar and fast decay constants among seasons is possibly because of the small difference in seasonal rainfall in TSNW, while seasonal variation in nitrogen and phosphorus is possibly a result of changes in microbial activity. This study highlights the need for an integral approach to research on nutrient cycling in mangrove forests because of its complex decay patterns. [ABSTRACT FROM AUTHOR]

Schwarzer, K.; Nguyen Cong Thanh and Ricklefs, K., 2016. Sediment re-deposition in the mangrove environment of Can Gio, Saigon River estuary (Vietnam). In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 138-142. Coconut Creek (Florida), ISSN 0749-0208. Sediment re-deposition in mangrove environments is usually attributed to marine and estuarine hydrodynamics - rainfall as a driver was not considered yet. However, combined with annual water level variations, tropical rainfall can play a significant role for sediment re-deposition. Inside mangroves, current velocities induced by rainwater runoff during low tide conditions can be much stronger than tide-induced currents. Along the Saigon River Estuary and the Mekong Delta coastline, rainfall is high from May to October and low from December to April. To study processes controlling sediment re-deposition, data of current and suspended matter concentration have been combined with sediment re-deposition rates. All investigations have been carried out in the Can Gio mangrove reserve, Saigon River mouth. Based on a 19-year data set (1991 - 2009), strong annual variability in water level heights and tidal range are observed, with a mean maximum high tide level of 3.34 m during the rainy season and 3.73 m at the beginning of the dry season. Maximum tidal range is reached during the rainy season coinciding with the lowest annual average sea level. The highest parts of the mangrove forest are not inundated by tides during these periods. Only heavy rainfall during these times can lead to mangrove soil mobilisation, induce strong currents between the mangrove roots and cause erosional gullies. Depending on the amount of precipitation, this sediment mobilisation and the amount of suspension load in the forest can be much stronger than sediment transport induced by tidal currents. [ABSTRACT FROM AUTHOR]

Rahaman, S.M.B.; Rahaman, M.S.; Ghosh, A.K.; Gain, D.; Biswas, S.K.; Sarder, L.; Islam, S.S., and Sayeed, A.B., 2015. A spatial and seasonal pattern of water quality in the Sundarbans river systems of Bangladesh. Comprehensive field measurements were made in three major river systems (RSs) of the Sundarbans during October 2010 to August 2011 under post-monsoon, dry winter, and monsoon seasons to assess the pollution status. Fifteen experimental sites were set for collection of water samples from discrete layers under different tidal conditions. Salinity, temperature, pH, and dissolved oxygen (DO) were determined in situ and chemical oxygen demand (COD), biological oxygen demand (BOD), total nitrogen (TN), total phosphorus (TP), nitrate, phosphate, and ammonium were measured through laboratory analysis. Mean DO was recorded between 3.93 and 7.37 mg/L with an average 5.44 mg/L. Highest average DO was noticed at Rupsha-Passur RS during post-monsoon, whereas the lowest was in Kholpetua-Arpangashia RS during monsoon. Mean BOD ranges between 0.3 and 4.1 mg O2/L, with an average of 2.04 mg O2/L, where maximum and minimum concentrations were measured at Kholpetua-Arpangashia RS in monsoon and dry winter respectively. Mean COD was found to vary from 20 to 240 mg O2/L, with an average 121.33 mg O2/L, exceeding the permissible range of 4-8 mg O2/L. Rupsha-Passur RS shows lowest average COD during post-monsoon, whereas Kholpetua-Arpangashia RS indicated highest COD in winter. Measured COD was higher in the dry season than in the wet season because of precipitation that causes dilution in the RSs. The study indicates the existence of organic pollution, though the DO concentration was within the permissible limit. Analyzed water samples showed nitrate, phosphate, and ammonium values in the range of 0.083 ± 0.03 to 0.627 ± 0.42 mg/L, 0.011 ± 0.005 to 0.449 ± 0.26 mg/L, and 0.038 ± 0.018 to 0.176 ± 0.16 mg/L respectively. TN and TP concentrations were not high enough in most cases, as there is a chance of eutrophication due to algal pollution. Study results will help identify factors responsible for affecting the biodiversity of the Sundarbans intertidal mangrove forest. [ABSTRACT FROM AUTHOR]

Lima, N. G.B, Galvani, E., Falcão, R. M. and Cunha-Lignon, M., 2013. Air temperature and canopy cover of impacted and conserved mangrove ecosystems: a study of a subtropical estuary in Brazil. In: Conley, D.C., Masselink, G., Russell, P.E. and O'Hare, T.J. (eds.) The aim of this study was to analyze and compare the variation of air temperature between impacted and conserved mangrove areas by monitoring the microclimate and canopy cover of mangrove forests in the southern coast of São Paulo State, Brazil. Data were collected from September 2011 to August 2012 using meteorological towers installed below the canopy at a height of 2 m. Hemispherical photographs were processed to acquire the canopy opening and Leaf Area Index, which quantifies the area with leaves, trunks and branches. The mangrove vegetation structure was characterized in permanent plots located in conserved and impacted areas. All plants were identified and described. Evaluations of the temperature data using Pearson linear correlation, T Paired and Wilcoxon tests with a significance level of 5% indicated a 94% correlation with r = 0.973. The vegetation was dominated by Rhizophora mangle (red mangrove) in both areas. The conserved mangrove forest presented a continuous recruitment of red mangrove seedlings and saplings, whereas the impacted mangrove forest was characterized by mangrove associate species and aquatic macrophytes, indicating environmental alteration. The absolute maximum temperatures recorded in the impacted and conserved mangrove forests were 36.1°C and 35.6°C, respectively. Moreover, the minimum recorded temperatures in the impacted and conserved mangroves were 8.6°C and 9.7°C, respectively. These results indicate that the temperature amplitudes are lower in the conserved mangrove (25.9°C) than in the impacted mangrove (27.5°C) and that the conservation status of the mangrove canopy contributes to the temperature variation in this environment. [ABSTRACT FROM AUTHOR]