Selenium in sediments, pore waters and benthic infauna of Lake Macquarie, New South Wales, Australia

Abstract

Measurements of selenium in sediments and benthic infauna of Lake Macquarie, an estuary on the east coast of Australia, indicate that sediments are a significant source of selenium in the lake's food web. Analysis of surficial sediment samples indicated higher selenium concentrations near what are believed to be the main industrial sources of selenium to the lake: a smelter and a power station. Sediment cores taken from sediments in Mannering Bay, near a power station at Vales Point, contained an average of 12 times more selenium in surficial sections than sediment cores from Nord's Wharf, a part of the lake remote from direct inputs of selenium. The highest selenium concentration found in Mannering Bay sediments (17.2 μg/g) was 69 times the apparent background concentration at Nord's Wharf (0.25 μg/g). Pore water concentrations in Mannering Bay were also high, up to 5 μg/l compared to those at Nord's Wharf which were below detection limits (0.2 μg/l). Selenium concentrations in muscle tissues of three benthic-feeding fish species (Mugil cephalus, Platycephalus fuscus, Acanthopagrus australis) were significantly correlated (p<0.05) with surficial sediment selenium concentration. Selenium concentrations in polychaetes and molluscs of Mannering Bay were up to 58 times higher than those from Nord's Wharf. Two benthic organisms, the eunicid polychaete Marphysa sanguinea and the bivalve mollusc Spisula trigonella, were maintained at different densities in selenium-spiked sediments. Both animals accumulated selenium from the spiked sediment, confirming that bioaccumulation from contaminated sediments occurs. Collectively, these data suggest that benthic food webs are important sources of selenium to the fish of Lake Macquarie.

Introduction

Selenium contamination of aquatic ecosystems has been shown to cause fish and bird mortality (Gillespie & Baumann, 1986Ohlendorf, Hoffman, Saiki, & Aldrich, 1986). Sublethal effects are also prevalent in animals exposed to high selenium concentrations and for fish these include oedema, reduced hematocrit and heamoglobin levels, swollen gill lamella with extensive vacuolation, degeneration of ovarian follicles and liver, myocardial and pericardial damage and chromosomal aberrations (Krishnaja & Rege, 1982, Sorensen & Bauer, 1983Sorensen, Cumbie, Bauer, Bell, & Harlan, 1984Gillespie & Baumann, 1986, Saiki, 1990).

Concern about selenium contamination of Lake Macquarie became public after the release of reports (Roberts, 1994Maher, Deaker, Jolley, Krikowa, & Roberts, 1997) of concentrations of selenium in mullet (Mugil cephalus) and silverbiddy (Gerres subfasciatus) that were up to 12 times the acceptable limit for human consumption (1 μg/g wet wt). The fish analysed in these studies were taken from areas close to coal-fired power stations. Subsequently, the Hunter Public Health Unit conducted a study in which mullet, luderick (Girella tricuspidata), trumpeter whiting (Sillago maculata), yellowfin bream (Acanthopagrus australis) and dusky flathead (Platatycephalus fuscus) were caught from most parts of Lake Macquarie and trace metal concentrations measured (Wlodarczkyk & Beath, 1997). The results obtained by these studies, when compared to the selenium concentrations of Australian fish from unpolluted locations (Maher, Baldwin, Deaker, & Irving, 1992), showed that, on average, fish from Lake Macquarie contained six times the selenium concentration of those taken from unpolluted areas. In the case of mullet, the average selenium concentrations in fish from Lake Macquarie were found to be fourteen times higher than the national average.

It has been shown in previous studies (e.g. Fowler & Benayoun, 1976aLui, Yang, Hu, Harrison, & Price, 1987Zhang, Hu, Huang, & Harrison, 1990) that food chain accumulation is the major route of selenium bioaccumulation in marine animals. Selenium concentrated in organic detritus in sediments is thought to be more important than that dissolved in water in contaminating food webs (Canton and Van Derveer, 1997). High concentrations of selenium in Lake Macquarie sediments have been reported. Batley (1987)measured a selenium concentration of 14 μg/g in a single sediment core from Cockle Bay at the northern end of Lake Macquarie (Fig. 1), which receives discharges from smelting operations. Carroll, Nobbs, and Smith (1996)measured selenium concentrations in surficial sediments of up to 1.94 μg/g at Bennet Park (northeast Lake Macquarie) and up to 1.8 μg/g from the southern perimeter of Cockle Bay and adjacent to the coal-fired power station at Vales Point. Crawford et al. (1976)showed that approximately 20–40% w/w of sediments in Wyee Bay were composed of fly ash. Davies and Linkson (1991)subsequently reported that fly ash from Eraring and Vales Point power stations contained 21–22 μg/g of selenium.

The chemical forms of selenium present in sediments are unknown. Selenium from smelting operations may be entering the lake as selenite, selenate or elemental selenium. Fly ash and vapour phase selenium from power generation activities is probably elemental selenium (Andren, Klien, & Talmi, 1975). Elemental selenium is rapidly converted to selenite on oxidation (Masscheleyn, Delaune, & Patrick, 1990). In aerobic sediments selenium will exist as an oxyanion in the form of selenite, selenate or biselenite (Masscheleyn, Delaune, & Patrick, 1991a) while under reducing conditions selenium will exist as elemental selenium or metal selenides (Masscheleyn & Patrick, 1993). Selenite and selenate are readily taken up by bacteria (Carroll et al., 1998) while selenite is preferred by phytoplankton (Price, Thompson, & Harrison, 1987). Bacteria and phytoplankton probably contain selenocysteine and selenomethionine (Wrench, 1978, Doran, 1982, Bottino et al., 1984) and form the base of food chains.

It was expected that high concentrations of selenium exist in sediments near power generation and smelting activities in Lake Macquarie, that benthic infauna are accumulating selenium and that contamination of fish is occurring in areas with contaminated sediments, i.e. via benthic food chains. In order to examine the first two hypotheses we measured selenium concentrations in surficial sediments around the lake to identify contaminated locations. To determine if any link existed between selenium concentrations in sediment and fish, these values were regressed. We then focussed on a contaminated area near one of the power stations, Mannering Bay, comparing sediment, pore water and infaunal selenium concentrations with those from Nord's Wharf, a relatively uncontaminated location. Bioaccumulation experiments using Marphysa sanguinea, an omnivorous polychaete worm, and a filter-feeding bivalve Spisula trigonella which lives in sediment, were then conducted to confirm that bioaccumulation of selenium from contaminated sediments would occur in these common species.