Growth of Corophium volutator under laboratory conditions.

Temperature-dependent growth is an important factor in the population model of Corophium volutator that was developed to translate responses in a 10-day acute bioassay to ecological consequences for the population. The growth rate, however, was estimated from old data, based on a Swedish population. Therefore, new growth rates are estimated herein from two experiments using Corophium volutator. To save time, a tool was developed to use image analysis to measure Corophium volutator. The experiments show that Corophium volutator has a low growth rate at low temperatures (5-10 degrees C). At higher temperatures no difference in growth rate between 15 degrees C and 25 degrees C was found. The growth rate from these experiments is comparable to data found in literature. A new relationship between temperature and individual growth was estimated, and incorporated into the Corophium population model. As the model also uses the same temperature relationship for reproduction, the modelled population growth rate at different temperatures changes as a result of the new data. The new growth rate and the updated temperature relationship result in reduced tolerance to external stressors, as previously predicted by the model.

Ammonium toxicity at high pH in a marine bioassay using Corophium volutator.

Two forms of ammonium exist in water: un-ionized ammonia NH3 and ionized ammonium NH4+. The toxicity to many aquatic organisms is primarily attributed to the NH3 (un-ionized) species, with the NH4+ ion (ionized) species being relatively less toxic. The pH level influences the degree of ionization. It is therefore very important that quality criteria be derived for total ammonium levels at several pH values in order to allow correct interpretation of the sediment bioassay with Corophium volutator. The responses of Corophium to total ammonium were studied in a series of pH-controlled experiments. The LC50 of total ammonium showed a significant decrease with increasing pH, in both water-only and sediment experiments. The results indicated a combined NH4+ and NH3 toxicity at pH levels less than 8.3. The results can be used to set pH-dependent water quality criteria for total ammonium in overlying water in a 10-day sediment bioassay with Corophium volutator.

Chemical and biological evaluation of sediments from the Wadden Sea, The Netherlands.

We describe the results of an evaluation of marine sediments using chemical measurements and bioassays. Four groups of chemicals, i.e., heavy metals, PAHs, chlorinated aromatic compounds, and tin compounds, were measured at 16 locations in the Wadden Sea, The Netherlands. Extractions of sediments from each location also were assessed using five bioassays. Our objective was to identify chemicals likely to pose biological risks, characterize the relation between bioassay results and particular classes of chemical(s) and determine "clean" reference sites on the basis of the chemical and biological evaluations. A multivariate technique (Principal Component Analysis; PCA) was used to meet these objectives. Results of the PCA indicated that the response of the Microtox Solid Phase bioassay had a positive, significant relationship with the levels of PAHs and organotin compounds. The responses of the other bioassays did not consistently relate to the concentrations of the other measured chemicals. Our findings indicate that the organotin compounds may still be a stressor for aquatic invertebrates in the Dutch Wadden Sea. On the basis of the chemical and biological evaluations, four sites (Dantziggat, Malzwin, Richel and Lauwers) can be considered to be "clean" reference sites.

Oil effect in freshly spiked marine sediment on Vibrio fischeri, Corophium volutator, and Echinocardium cordatum.

The purpose of this study was to provide data to be used in The Netherlands for development of ecotoxicologically based quality criteria for oil-contaminated sediments and dredged material. In addition, the relation of toxicity to specific oil boiling-point fraction ranges was explored. Natural marine sediment, with a moisture, organic carbon, and silt content of approximately 80, 1.8, and 33% of the dry weight, respectively, was artificially spiked using a spiking method developed in this project. Aliquots of one part of the sediment were spiked to several concentrations of Gulf distillate marine grade A (DMA) gasoil (containing 64% C10-19) and aliquots of the other part to several concentrations of Gulf high viscosity grade 46 (HV46) hydraulic oil (containing 99.2% C19-40). Thus, for each individual oil type, a concentration series was created. Vibrio fischeri (endpoint: bioluminescence inhibition), Corophium volutator (endpoint:mortality), and Echinocardium cordatum (endpoint:mortality) were exposed to these spiked sediments for 10 min, 10 d and 14 d, respectively. Based on the test results, the effective concentration on 50% of the test animals was statistically estimated. For DMA gasoil and HV46 hydraulic oil, respectively, the effective concentrations were 43.7 and 2,682 mg/kg dry weight for V. fischeri, 100 and 9,138 mg/kg dry weight for C. volutator, 190, and 1064 mg/kg dry weight for E. cordatum. This study shows that the toxicity is strongly correlated with the lower boiling-point fractions and especially to those within the C10-C19 range.