Influence of sediment-organic matter quality on growth and polychlorobiphenyl bioavailability in echinodermata (Amphiura filiformis)

Sediment total organic carbon (TOC) content is considered to be a primary f ood source for benthic invertebrates and a major factor influencing the par titioning and bioavailability of sediment-associated organic contaminants. Most studies report that both toxicity and uptake of sediment-associated co ntaminants by benthic organisms are inversely proportional to sediment TOC content. The aim of this study was to determine the importance of the TOC q uality for the bioavailability of sediment-associated organic contaminants and the growth of benthic macrofauna. The common infaunal brittle star Amph iura/filiformis was exposed to a base sediment covered by a C-14-polychloro biphenyl (3,3'4,4'-C-14-tetrachlorobiphenyl (TCB)) contaminated top layer ( 0-2 cm), enriched to the same TOC content with 31 g TOC/m(2) of different q uality and origin. The following carbon sources, ranging from labile to ref ractory, were used: (I) green macroalga (Ulva lactuca), (2) brown macroalga (Ascophyllum nodosum), (3) eelgrass (Zostera marina), (4) phytoplankton (C eratium spp.), and (5) lignins of terrestrial origin. Characterization of t he organic matter quality was accomplished by measuring the content of amin o acids, lipids, C, N, and polyphenolic compounds. The reactivity of the se dimentary organic matter was assessed by means of respiration and dissolved inorganic nitrogen flux measurements. The experiment was carried out in I- L glass jars, each containing four brittle stars and the contaminated and e nriched sediment. The jars were circulated in a flow-through mode with filt ered seawater. Somatic growth (regeneration of a precut arm) and bioaccumul ation of C-14-TCB were measured at 10 sampling occasions during 48 d of exp osure. Growth rates, TCB uptake rates, and steady-state concentrations diff ered significantly between treatments and were correlated to the qualities of the organic substrates. The greatest TCB accumulation and growth were ob served in treatments with the most labile organic substrates and the lowest accumulation and growth were seen with the most refractory substrates. Res ults from this experiment suggest that the bioaccumulation of organic conta minants in benthic infauna is dependent on the nutritional quality of the s edimentary organic matter.