Wastewater bioremediation by mangrove ecosystems impacts crab ecophysiology: In-situ caging experiment

Abstract

Mangroves are tidal wetlands that are often under strong anthropogenic pressures, despite the numerous ecosystem services they provide. Pollution from urban runoffs is one such threats, yet some mangroves are used as a bioremediation tool for wastewater (WW) treatment. This practice can impact mangrove crabs, which are key engineer species of the ecosystem. Using an experimental area with controlled WW releases, this study aimed to determine from an ecological and ecotoxicological perspective, the effects of WW on the red mangrove crab Neosarmatium africanum. Burrow density and salinity levels (used as a proxy of WW dispersion) were recorded, and a 3-week caging experiment was performed. Hemolymph osmolality, gill Na+/K+-ATPase (NKA) activity and gill redox balance were assessed in anterior and posterior gills of N. africanum. Burrow density decreased according to salinity decreases around the discharged area. Crabs from the impacted area had a lower osmoregulatory capacity despite gill NKA activity remaining undisturbed. The decrease of the superoxide dismutase activity indicates changes in redox metabolism. However, both catalase activity and oxidative damage remained unchanged in both areas but were higher in posterior gills. These results indicate that WW release may induce osmoregulatory and redox imbalances, potentially explaining the decrease in crab density. Based on these results we conclude that WW release should be carefully monitored as crabs are key players involved in the bioremediation process. Highlights ► Mangroves are suggested as biofiltering systems of domestic effluent. ► Mangrove crabs are involved through their bioturbation activities. ► Wastewater release impacts crab burrow density. ► Mangrove crabs are physiologically impacted by wastewaters.

Review of the mudflat varunid crab genus Metaplax (Crustacea, Brachyura, Varunidae) from East Asia and northern Vietnam

“…The habitat preferred by species of Metaplax is suggested to be related to physiological constraints (e.g., food, temperature, salinity, etc. ; Curtis and McGaw 2012; Theuerkauff et al 2018). Understanding of the population structure may help reveal larval dispersal in the region of East Asia and northern South China Sea (Chan et al 2007; Shih et al 2015; Wang et al 2015; Chai et al 2017).…”

The Kandelia obovata transcription factor KoWRKY40 enhances cold tolerance in transgenic Arabidopsis

“…In this study, the KoWRKY40 expression was induced during the entire process under cold stress, indicating the KoWRKY40 gene could be induced by cold stress individually. Since mangrove plants generally grow in the intertidal zones and were subjected to various stresses [ 1 – 3 ], whether other WRKY genes of mangrove plants were induced by individual or combined stresses remains to be studied.…”

“…Mangrove plants are tropical/subtropical communities of xylophyta that grow in the intertidal zones of coastlines [ 1 ]. As an important marine wetland ecosystem, mangrove plants play important ecological and economic roles, such as keeping coastlines and beaches away from storm tide and tsunami, remediating contaminated environment, and providing food and shelters for marine organisms [ 2 , 3 ]. As a dominant community, mangrove plants have evolved to adapt and survive in such extreme habitat (high ultraviolet radiation, high salinity, submerged and hypoxia soil) [ 4 ].…”

Effect of climate change on birds in mangrove

“…The composition of the crustaceans' population in mangrove forest is also under the influence of climate change. As the precipitation in wet season increases annually due to climate change, crabs as mentioned above may be forced to migrate and abandon their caves which put them under great survival pressure [27].…”