Ray S
Experientia Suppl. 1986;50:65-75. doi: 10.1007/978-3-0348-7238-6_9.
It has been established that, although Cd occurs in the marine environment in only trace concentrations, most marine organisms, especially molluscs and crustaceans, can accumulate it rapidly. Cadmium is not uniformly distributed in the body and selectively accumulates in specific organs like liver, kidney, gills, and exoskeleton. The concentrations in muscle tissues are several orders of magnitude lower. The disposition of Cd in the organisms in the laboratory studies generally parallels those in nature. A number of biotic factors like body size, maturity, sex, etc. influence bioaccumulation but extensive studies are still lacking. The chemical form of Cd in the environment is of prime importance in bioaccumulation by marine organisms. Salinity can affect the speciation of Cd, and bioaccumulation is affected by both temperature and salinity. The ultimate level of Cd in the organisms will depend not only on the biotic and abiotic factors but also on metabolism of the metal by the organisms. A few studies indicate depuration of Cd by some bivalves but other organisms show very effective retention of Cd. Metallothionein formation for detoxification and storage has been observed in a large variety of marine organisms. Recent reports indicate an alternate storage and excretion mechanism in the formation of membrane-limited vesicles or granules. There seems to be a common link between intracellular localisation of Cd in metal-binding proteins and Cd containing vesicles as detoxifying mechanisms in the marine organisms. Much of what is known about Cd bioaccumulation by marine organisms has come from laboratory studies and there are inherent dangers in trying to extrapolate the results to field situations. In spite of tremendous progress made over the years, the basic understanding of the bioaccumulation process is still very nebulous and will remain so until the uptake, storage, and elimination processes are fully understood.
已经确定，尽管镉在海洋环境中仅以痕量浓度存在，但大多数海洋生物，尤其是软体动物和甲壳类动物，能够迅速积累镉。镉在体内分布不均，会选择性地在肝脏、肾脏、鳃和外骨骼等特定器官中积累。肌肉组织中的浓度要低几个数量级。实验室研究中生物体中镉的分布情况通常与自然界中的情况相似。一些生物因素，如体型、成熟度、性别等，会影响生物积累，但仍缺乏广泛的研究。环境中镉的化学形态对海洋生物的生物积累至关重要。盐度会影响镉的形态，生物积累受温度和盐度两者的影响。生物体中镉的最终含量不仅取决于生物和非生物因素，还取决于生物体对金属的代谢。一些研究表明某些双壳贝类会排出镉，但其他生物则表现出对镉的非常有效的保留。在多种海洋生物中都观察到了金属硫蛋白的形成以进行解毒和储存。最近的报告表明在形成膜限制的囊泡或颗粒时有另一种储存和排泄机制。在海洋生物中，镉在金属结合蛋白中的细胞内定位与含镉囊泡之间似乎存在共同的联系，作为解毒机制。目前关于海洋生物镉生物积累的许多知识都来自实验室研究，试图将结果外推到野外情况存在内在风险。尽管多年来取得了巨大进展，但对生物积累过程的基本理解仍然非常模糊，在充分了解吸收、储存和消除过程之前仍将如此。
