Adeleke Babatunde, Robertson-Andersson Deborah, Moodley Gan
Marine Biology, School of Life Sciences, University of KwaZulu-Natal, Westville, Durban, KZN, South Africa.
Heliyon. 2020 Aug 28;6(8):e04725. doi: 10.1016/j.heliyon.2020.e04725. eCollection 2020 Aug.
Durban Bay and Richards Bay Harbours are the largest and most economically active shipping harbours in South Africa supporting a diversity of ecosystems and biota of ecological importance. This study assessed and compared levels of metals in selected tissues of the sand bubbler crab (), water and sediments from anthropogenically impacted Durban and Richards Bay Harbours with those of Mlalazi estuary, a considered pristine site due to its sheltered catchments. Metal concentrations (Cd, Cu, Pb and Zn) were investigated using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). Metals concentrations in crab tissues were as follows; exoskeleton > gill > digestive gland, metal concentrations in tissues followed the order Cu > Zn > Pb > Cd. Metal levels in crabs from Durban Harbour (Cd 0.42, Cu 83.8, Pb 2.43and Zn 6.4 μg/g) were significantly higher than Richards Bay (Cd 0.22, Cu 27.7, Pb 1.23 and Zn 9.54 μg/g) and Mlalazi estuary (Cd 0.17, Cu 18.7, Pb 3.53 and Zn 6.91 μg/g). Metal levels in sediments followed the order Zn > Cu > Pb > Cd. Mlalazi had significantly elevated metal levels in sediment (Cd 6.83, Cu 35.63, Pb 33.43 and Zn 56.27 μg/g) compared to Durban Harbour (Cd 2.73, Cu 16.07, Pb 12.20 and Zn 38.70 μg/g) and Richards Bay (Cd 3.10, Cu 16.00, Pb 11.43 and Zn 26.07 μg/g). Metal concentrations in water were Cu > Zn > Pb > Cd save Mlalazi estuary with significantly higher Zn levels. Mlalazi estuary, the considered pristine site had significantly elevated metal levels in the sediments and water compared with the impacted sites; however, had significantly lower metal levels in the crabs' tissues due to lower metal bioavailability. Factors such as high natural metal concentrations, metal speciation, sediment grain and organic matter content could possibly account for high metal concentrations without corresponding bioaccumulation and magnification in crabs from Mlalazi estuary.
德班湾和理查兹湾港口是南非最大且经济活动最为活跃的航运港口，支撑着多种具有生态重要性的生态系统和生物群。本研究评估并比较了来自受人为影响的德班和理查兹湾港口的沙泡蟹特定组织、水和沉积物中的金属含量，并与因集水区受保护而被视为原始地点的姆拉腊齐河口的相应样本进行了比较。使用电感耦合等离子体发射光谱法（ICP - OES）研究了金属浓度（镉、铜、铅和锌）。蟹组织中的金属浓度如下：外骨骼＞鳃＞消化腺，组织中的金属浓度顺序为铜＞锌＞铅＞镉。德班港蟹类的金属含量（镉0.42、铜83.8、铅2.43和锌6.4微克/克）显著高于理查兹湾（镉0.22、铜27.7、铅1.23和锌9.54微克/克）和姆拉腊齐河口（镉0.17、铜18.7、铅3.53和锌6.91微克/克）。沉积物中的金属含量顺序为锌＞铜＞铅＞镉。与德班港（镉2.73、铜16.07、铅12.20和锌38.70微克/克）和理查兹湾（镉3.10、铜16.00、铅11.43和锌26.07微克/克）相比，姆拉腊齐河口沉积物中的金属含量显著升高（镉6.83、铜35.63、铅33.43和锌56.27微克/克）。水中的金属浓度顺序为铜＞锌＞铅＞镉，但姆拉腊齐河口的锌含量显著更高。被视为原始地点的姆拉腊齐河口，其沉积物和水中的金属含量与受影响地点相比显著升高；然而，由于金属生物可利用性较低，蟹类组织中的金属含量显著较低。诸如高天然金属浓度、金属形态、沉积物颗粒和有机物含量等因素可能是姆拉腊齐河口蟹类中金属浓度高但无相应生物累积和放大现象的原因。
