Effects of fluoranthene and ambient oxygen levels on survival and metabolism in three sibling species of Capitella (Polychaeta)

The successful persistence of Capitella spp. in disturbed and/or oil-pollut ed habitats is widely known, but demographic adaptations might be only part of the explanation and Little is known about differences among species. Th e present study investigates ecophysiological effects of the common PAH (po lycyclic aromatic hydrocarbon) fluoranthene (FLU) on juvenile and adult sur vival, comparing 3 sibling species of Capitella (Polychaeta; Capitellidae). Subsequently, the influence of FLU on the aerobic and anaerobic metabolism in the most 'sensitive' species, Capitella sp. S, and most 'tolerant' spec ies, Capitella sp. I, was assessed. Oxygen uptake and internal succinate co ncentration tan indicator of anaerobic metabolism) were measured after shor t-term (7 h) and long-term (2 wk) FLU pre-exposure (100 mu g g(-1)). FLU ex posure reduced mean survival times of juveniles (4 d old) of all sibling sp ecies, but tolerance varied among the 3 species of Capitella adults. Capite lla sp. S, originally collected from 'clean' oxygen-rich North Sea intertid al sediments, was most sensitive and Capitella sp. M, and Capitella sp. I, which is the most opportunistic of the sibling species described to date, w ere most tolerant. In Capitella sp. S, O-2 uptake decreased at lower ambien t oxygen levels and increasing FLU concentrations increased oxygen consumpt ion. Similarly, O-2 uptake decreased at lower ambient oxygen levels in Capi tella sp. I; however, FLU concentrations had no effect on oxygen uptake. Fo r both species, anaerobic metabolism increased with declining ambient oxyge n levels, and was influenced by FLU exposure in Capitella sp. S, but not in Capitella sp. I. Part of the explanation for the success of Capitella sp. I in oil-polluted habitats may be that this species is able to channel ener gy into vital processes without a measurable increase in energy expenditure . We conclude that these 3 Capitella species are ecophysiologically diverse in their responses to toxicant exposure. Our results suggest that toxicant tolerance differences among sibling species have a genetic basis and that increased aerobic and anaerobic metabolic rates in response to toxicant exp osure can have negative survival consequences. This has to be considered wh en using these species as pollution indicators or to improve sediment quali ty.