MARBEC (MARine Biodiversity, Exploitation and Conservation), Univ Montpellier, CNRS, Ifremer, IRD, 34000 Montpellier, France.
Centre Universitaire de Formation et de Recherche de Mayotte (CUFR), 97660 Dembeni, Mayotte, France.
Ecotoxicol Environ Saf. 2022 May 1;236:113487. doi: 10.1016/j.ecoenv.2022.113487. Epub 2022 Apr 8.
Mangrove forests are impacted by a large range of anthropogenic activities that challenge their functioning. For example, domestic wastewater (WW) discharges are known to increase vegetation growth but recent studies indicate that they have negative effects on benthic macrofauna, especially on mangrove crabs, these ecosystem engineers playing a key role on the functioning of the mangrove. In experimental areas regularly receiving WW at low tide (Mayotte Island, Indian Ocean), a drastic decrease in burrowing crab density has been reported. In this context, the individual behavioural and physiological responses of the fiddler crab Paraleptuca chlorophthalmus exposed to short-term (6 h) pulse of WW and ammonia-N (as a potential proxy of WW) were investigated. This species is one of the most sensitive to WW within the mangrove crab community. For the behavioural experiment, crabs could choose between the aquatic and aerial environment. Individual metabolic rate (O consumption) was monitored after 6 h of exposure in WW or ammonia-N. Aerobic and anaerobic metabolic markers (citrate synthase and lactate dehydrogenase activities, respectively) were also evaluated. Results indicate that crabs exposed to WW are more active and mobile than controls after 3 h. Crabs actively emersed from WW and reduced their activity and mobility after 6 h. A higher metabolic rate in WW occurred immediately (t = 0 h), 3 and 6 h after WW exposure, with also, a burst in aerobic bacterial consumption in WW, but no effect of ammonia-N. No effect of WW or ammonia-N was observed on enzymatic aerobic and anaerobic metabolic markers. Therefore, short-term pulses with domestic polluted wastewater trigger quick behavioural and metabolic responses that could be deleterious if prolonged. These results could contribute to the understanding of the community-scale changes observed in benthic macrofauna after several years of regular domestic pollution pulses.
红树林受到多种人为活动的影响，这些活动挑战了它们的功能。例如，人们知道生活污水（WW）的排放会促进植被生长，但最近的研究表明，它们对底栖大型动物群有负面影响，尤其是对红树林蟹，这些生态系统工程师对红树林的功能起着关键作用。在经常接受 WW 低潮期排放的实验区域（印度洋马约特岛），报道称挖洞蟹的密度急剧下降。在这种情况下，研究了短时间（6 小时）WW 和氨氮（作为 WW 的潜在替代品）脉冲暴露下，招潮蟹 Paraleptuca chlorophthalmus 的个体行为和生理反应。该物种是红树林蟹群中对 WW 最敏感的物种之一。在行为实验中，螃蟹可以在水和空气环境之间进行选择。在 WW 或氨氮中暴露 6 小时后，监测个体代谢率（O 消耗）。还评估了有氧和无氧代谢标志物（柠檬酸合酶和乳酸脱氢酶活性）。结果表明，与对照组相比，暴露于 WW 中的螃蟹在 3 小时后更活跃和移动。螃蟹从 WW 中主动浮出水面，并在 6 小时后减少其活动和移动性。WW 暴露后立即（t=0 小时）、3 小时和 6 小时，WW 中的代谢率更高，WW 中的有氧细菌消耗也突然增加，但氨氮没有影响。WW 或氨氮对有氧和无氧代谢酶标记物均无影响。因此，如果 WW 或氨氮的影响持续时间延长，短期脉冲会引发快速的行为和代谢反应，这可能是有害的。这些结果有助于理解在多年定期家庭污染脉冲后观察到的底栖大型动物群的群落尺度变化。
