Physicochemistry or physiology: cadmium uptake and effects of salinity and osmolality in three crabs of different ecologies

Abstract

The effects of salinity and osmolality differences on the uptake rates of dissolved cadmium were investigated in 3 crabs of different ecologies -the euryhaline common shore crab Carcinus maenas, the extremely euryhaline Chinese mitten crab Eriocheir sinensis, and a more stenohaline crab, the velvet swimming crab Necora puber. This study tests predictions derived from the interpretations of the authors from a study of Zn uptake by the same crabs, in terms of the balance between physicochemical and counteractive physiological effects controlling trace metal uptake rates from solution. As predicted, reduced salinities caused increases in the cadmium uptake rate of E. sinensis as expected from the free metal ion model, with increased free cadmium ion availabilities in conditions of reduced chloride complexation. In the cases of C. maenas and N. puber, however, decreased salinity was associated with reduced cadmium uptake, a result interpreted in terms of a physiological response by these crabs to low salinity offsetting the physicochemical effect of increased free cadmium ion availability. This physiological response may include reductions in apparent water permeability with reduced salinities. Osmolality experiments showed that the physiological responses made by the crabs to decreases in salinity could not be explained simply by responses to changes in osmotic pressure of the medium. The interaction of physiology and physicochemistry controls rates of trace metal uptake from solution by these ecophysiologically distinct crab species.KEY WORDS: Cadmium uptake · Salinity · Osmolality · Crabs · Carcinus maenas · Eriocheir sinensis · Necora puber Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 286: [217][218][219][220][221][222][223][224][225][226][227][228][229] 2005 al. 1990, Rainbow et al. 1993), or changes in salinity that alter concentrations of inorganic anions such as chloride that complex particular metal ions (Nugegoda & Rainbow 1989a,b, Rainbow et al. 1993, Rainbow & Black 2002. For example, dissolved cadmium in seawater exists mostly as chloro-complexes (e.g. CdCl + , CdCl 2 0 , CdCl 3 -) with only a small percentage (ca 2.5%) as the free Cd ++ ion (Zirino & Yamamoto 1972, Mantoura et al. 1978, Bruland 1983, Rainbow et al. 1993. Reductions in salinity reduce the amount of chloride present and increase the percentage of dissolved cadmium present as the free metal ion (Rainbow et al. 1993). Such physicochemical effects on the rates of uptake of trace metals by invertebrates are independent of the invertebrates themselves (Rainbow 1997, Rainbow & Black 2002.On the other hand, some aquatic invertebrates can affect the rate of trace metal uptake from solution by making a physiological response to changes in the medium, for example to salinity reduction (Rainbow et al. 1993, Rainbow & Kwan 1995, Rainbow & Black 2002. Such physiological intercession that affects trace metal uptake rates is by no means a universal feature of aquatic invertebrates, and see...

Predicting Risks of Cadmium Toxicity in Salinity-Fluctuating Estuarine Waters Using the Toxicokinetic–Toxicodynamic Model

“…These inhibitory effects of "complexation" and "competition" on Cd uptake were empirically described using eq 7. Similar inhibitory effects of salinity against Cd bioaccumulation were consistently observed for various other organism species, such as mussels, 29,30 clams, 30 snails, 29 copepods, 31 shrimps, 32 crabs, 33 and fish. 8,34 Similarly, at the high Cd concentration of 500 μg L −1 , Cd k u decreased from 0.697 to 0.293 and 0.154 L g −1 d −1 when the salinity increased from 5 to 15 and 25, respectively (Figure 2c, Table 1).…”

“…These inhibitory effects of “complexation” and “competition” on Cd uptake were empirically described using eq . Similar inhibitory effects of salinity against Cd bioaccumulation were consistently observed for various other organism species, such as mussels, , clams, snails, copepods, shrimps, crabs, and fish. , …”

Linking trace element variations with macronutrients and major cations in marine mussels Mytilus edulis and Perna viridis

“…Specifically, salinity can directly affect the speciation and bioavailability of some trace elements in ambient seawaters and subsequently affect their bioaccumulation . Meanwhile, salinity variation can cause ecophysiological changes (e.g., apparent water permeability, feeding physiology, and growth) in the animals and subsequently affect bioaccumulation of trace elements . Little is known, however, about combined effects of salinity‐induced speciation and ecophysiological changes, as well as their relative contribution to trace element bioaccumulation.…”

Quality Standard Setting and Environmental Monitoring

“…The need for separate marine and freshwater standards remain a topic of discussion (Matthiessen et al, 2010;TGD, 2011), considering the possibility that salinity can influence both the physicochemistry of contaminants and organisms as exemplified in the case of cadmium by Rainbow and Black (2005); also, there is the possibility that sensitivity differs between marine and freshwater organisms. Examples of substances (ammonia, pyrethroid insecticides, organometallics, metals) for which toxicity is different are provided in Matthiessen et al (2010).…”