Physiological and cellular responses of oysters (Crassostrea hongkongensis) in a multimetal‐contaminated estuary

Abstract

The Pearl River estuary, southern China, suffers from multiple sources of metal contamination as a result of the rapid industrial development in the region; but the biological impacts of contamination remain unknown. In the present study, a euryhaline oyster, Crassostrea hongkongensis, was collected from different sites of the Pearl River estuary; and various physiological (heart rate, alkaline phosphatase as homeostatic regulation, and glycogen as energy reserve) and cytological (lysosomal membrane stability) biomarkers were quantified to assess this species as a potential bioindicator of metal pollution in contaminated areas. Large variations of metal accumulation levels in the oysters were documented, especially for copper (Cu), zinc (Zn), cadmium (Cd), chromium, and nickel (Ni). Among these metals, the authors demonstrated significant correlations between the digestive gland metal accumulation of Cu, Zn, and Ni and the cellular homeostasis (alkaline phosphatase) and glycogen reserves. Heart rate was positively correlated with Cd but negatively correlated with Cu and Zn concentrations in the gills. Lysosomal membrane stability was significantly inhibited at the most contaminated sites but had no relationship with the accumulated metal concentrations. These measurements indicate that multimetal contamination in the Pearl River estuary impacts the physiological and cytological performance of oysters. Environ Toxicol Chem 2016;35:2577-2586. © 2016 SETAC.

Antioxidant and detoxification responses of oysters Crassostrea hongkongensis in a multimetal‐contaminated estuary

“…The sites had been exposed to different types and levels of metal pollution. Site 1, located near Shenzhen Airport, was the most heavily contaminated, whereas site 3, located in Lau Fau Shan, was the least metal contaminated . The concentrations of organic pollutants in the oysters of the Pearl River Estuary were reported to be at low levels .…”

“…Previous studies have reported that C. hongkongensis have survived in some metal‐polluted estuaries of Southern China with extremely high metal levels in their bodies . In the companion study, we quantified the metal burdens in oyster tissues and found that the total Cu and Zn contents could reach up to 2.0% of oyster dry weights, even though the dissolved labile Cu and Zn concentrations were not high in waters of sampling sites . Such high concentration of metals in tissues may impact the antioxidant and detoxification systems of oysters, which play important roles in defending metal stresses by deleting reactive oxygen species (ROS) and detoxifying toxic metals.…”

“…In November of 2013, adult oysters C. hongkongensis of similar size (length, 5–6 cm) were randomly collected on the same day from rocky shores at 7 sites of the Pearl River Estuary in November 2013, as follows: 3 sites (1, 2, and 3) on the eastern shore, 3 sites (5, 6, and 7) on the western shore, and 1 site (4) on an island located in the middle of the Pearl River Estuary . The sites had been exposed to different types and levels of metal pollution.…”

“…The oyster gonads were immature in November , which was therefore selected as the sampling period. Detailed descriptions of the sampling sites, as well as details on sampling, transportation, acclimation, dissection, storage, extraction processes, and metal concentration measurements, are given in the companion study . Briefly, the collected oysters (24 individuals/site) were immediately transported back to the laboratory within 2 h without an additional oxygen supply after sampling.…”

“…The present study aimed to identify possible links between biological responses (biomarkers) in oysters and metals in the environment or biota, as well as the metals responsible for the changes in biomarkers. Combined with the results presented in the companion study , the applicability of the multibiomarkers technique, a promising environmental monitoring method employing bioindicator species, in evaluating the environmental risk of estuarine metal pollution is tested.…”