1065 Environmental Toxicology and Chemistry, Vol. 22, No. 5, pp. 1065–1074, 2003  2003 SETAC Printed in the USA 0730-7268/03 $12.00 + .00 TOXIC EFFECTS OF POLYCHLORINATED BIPHENYL BIOACCUMULATION IN SEA URCHINS EXPOSED TO CONTAMINATED SEDIMENTS EDDY Y. ZENG,*² S TEVEN M. BAY,² D ARRIN GREENSTEIN,² C HERRIE VISTA,² C HARLIE YU,‡ and KERRY RITTER² ²Southern California Coastal Water Research Project, 7171 Fenwick Lane, Westminster, California 92683, USA ‡City of Los Angeles, 12000 Vista del Mar, Playa del Rey, California 90893, USA ( Received 30 April 2002; Accepted 3 October 2002) Abstract—The uptake patterns and toxicity of polychlorinated biphenyl (PCB) congeners in the white sea urchin, Lytechinus pictus, on exposure to contaminated sediments were investigated. First-order modeling of uptake of the 10 most abundant PCB congeners or domains (containing more than one coeluting congener) by L. pictus indicated that a 35-d exposure was insufficient to reach steady state. Bioaccumulation of PCBs in sea urchins exhibited substantial difference between field and amended sediments, suggesting that caution must be exercised in sample preparation. Some evidence was observed of dependence of measured biota- sediment accumulation factors (BSAFs) on K ow , indicating that equilibrium partitioning of PCBs may not always be achieved between biota lipid, sediment organic carbon, and water. Survival of L. pictus was unaffected by exposure to field and amended sediments with PCB concentrations varying more than three orders of magnitude. The growth measures (diameter, wt, and gonad wt) were significantly reduced in L. pictus exposed to San Diego Bay ([SDB]; San Diego, CA, USA) sediment, whereas they were relatively unaffected after exposure to amended sediments (with much higher PCB concentrations than SDB sediment) prepared from a New Bedford Harbor (MA, USA) sediment. The toxic effects as measured by the growth rates in L. pictus were likely attributable to polycyclic aromatic hydrocarbons (PAHs), which were elevated in SDB sediment (7.3 g/g), rather than PCBs. Keywords—Bioaccumulation Toxicity Polychlorinated biphenyl Sea urchin Equilibrium partitioning INTRODUCTION Polychlorinated biphenyls are widely distributed in sedi- ments throughout the Southern California Bight (USA), yet little information is available by which to accurately assess their impacts on marine organisms. Previous studies have dem- onstrated reduced growth and PCB accumulation in the white sea urchin, Lytechinus pictus, at sites with elevated PCB con- centrations [1,2; http://www.sccwrp.org/pubs/techrpt.htm]. These data, however, are insufficient for developing bioac- cumulation models because multiple contaminants were pre- sent at the sites and too small a range of exposure concentra- tions was available to establish a relationship between con- taminant body burden and toxicity. Regulatory and monitoring programs rely on such bioaccumulation models for purposes such as establishing sediment quality criteria for human health [3] and determining the suitability of dredged materials for ocean disposal. A critical factor in these assessments is the completeness and accuracy of the bioaccumulation data. A popular approach is to describe bioaccumulation phe- nomena using the equilibrium partition theory (EPT) [4–6], in which lipid in biota and organic carbon (OC) in sediments (or soil) are relevant compartments for such partitioning. In a system consisting of sediment, biota, and water, the following partition coefficients can be defined under equilibrium con- ditions: C oc K = (1) oc C w C l BCF = (2) C w * To whom correspondence may be addressed (eddyz@sccwrp.org). where C oc , C w , and C l are compound concentrations in sediment (normalized to OC), water, and biota (normalized to lipid); K oc is the sediment-water partition coefficient; and BCF is bio- concentration factor with the biota being exposed to water only. Generally, C w is low and difficult to measure. In cases where sediment interstitial water is substantially different from the surrounding water that biota aspirate, C w is vaguely de- fined. A more practical and useful parameter, BSAF, can be derived from combining Equations 1 and 2: BCF C l BSAF = = (3) K C oc oc Under strictly equilibrium conditions and the assumption of equal partitioning capacity for OC and lipid, BSAF equals unity. Although using the EPT to determine BSAFs provides a simple method to relate bioaccumulation to sediment con- tamination [7,8], its validity remains questionable [7]. Marine organisms represent a tremendous diversity of physiological (e.g., metabolic rate) and life-history (e.g., feeding mode, de- gree of sediment association) characteristics that may under- mine the assumptions of the EPT. Bioaccumulation studies have been conducted with a variety of infaunal species [9] and indicate considerable variation in BSAFs. Few equivalent data exist for L. pictus, which, as an epibenthic deposit feeder, has life-history characteristics different from species (clams and polychaetes) commonly used in bioaccumulation studies. The research described in this paper was conducted to in- vestigate three aspects of PCB bioaccumulation in L. pictus. The first objective was to describe the uptake kinetics of PCB congeners in L. pictus exposed to field sediment. The second objective was to characterize the patterns of PCB bioaccu- mulation in L. pictus exposed to various levels of sediment