George R. Ditsworth

Sediment toxicity to a marine infaunal amphipod: Cadmium and its interaction with sewage sludge

Abstract The acute toxicity of cadmium to the marine infaunal amphipod, Rhepoxynius abronius , was determined separately in sediment and seawater. Most cadmium added to test sediment was bound to particles and less than 5% was dissolved in interstitial water. The LC 50 based on cadmium concentration in interstitial water was similar to the LC 50 based on cadmium concentration in seawater without sediment. Cadmium in interstitial water, rather than that bound to particles, therefore appears responsible for acute sediment toxicity to this species. The addition of small quantities of sewage sludge or an increase in the proportion of the fine fraction of sediment particles significantly reduced the toxicity of cadmium in sediment. Binding of cadmium by sediment particles may explain the presence of phoxocephalid amphipods at sites where sewage and metal pollution occur together. The cadmium sensitivity of R. abronius is similar to that of several marine invertebrates commonly used in seawater bioassays. This amphipod is a useful test species for sediment bioassays used in research, monitoring and regulatory programs.

Effects of natural sediment features on survival of the phoxocephalid amphipod, Rhepoxynius abronius

Effects of sediment particle size and water content on the survival of the amphipod, Rhepoxynius abronius, were examined by manipulating these natural sediment features within static laboratory microcosms. Mean amphipod survival in fine, uncontaminated, field sediments (≥ 80% silt-clay) can be 15% lower than survival in native sediment. Storage of sediments at 4°C over 7–14 days did not change sediment toxicity, but handling (i.e. elutriation and recombination) of muddy sediments increased toxicity. Sediment particle size and organic content had greater impact on the survival of R. abronius than did sediment water content in modifying amphipod survival, but we could not independently separate the effects of these two sediment variables. A new set of criteria is proposed to interpret toxicity results from the amphipod bioassay in the light of the mortality associated with fine sediment particle size. The efficacy of these criteria to separate mortality caused by fine particles and chemical contaminants was tested by analyzing field survey data from 78 Puget Sound (WA) Urban sites. Using our new criteria, the toxicity of these sediments was found to closely reflect the degree of chemical contamination. We propose that an approach similar to this be undertaken for toxicity tests whenever natural environmental factors induce mortality above background levels.

Spatio-temporal fluctuations in the distribution and abundance of demersal fish and epibenthic crustaceans in Yaquina Bay, Oregon

A total of over 32,000 demersal fish and epibenthic crustaceans belonging to 62 species were caught in 42 biweekly trawls from 10 stations in Yaquina Bay, Oregon, during 1967 and 1968. English sole,Parophrys vetulus, was the most abundant species. Seventeen species (13 fishes and 4 crustaceans) constituted 95% of the catch. Total numerical abundances of both individuals (mainly juvenile fishes) and species were greatest in the lower 12 km of the estuary during summer and early fall, a period of water mass stability and increased water temperature and salinity. This section of the estuary is used by many immature fishes and crustaceans as a “nursery area”. These fishes generally emigrate from the estuary as subadults in the fall around the onset of the rainy season. The fewest species were taken in January 1968 from the central, upper-estuarine, and riverine areas of the bay, this being a time when high rainfall and river discharge result in low salinity and temperature. Crustaceans (shrimp and subadult crabs) were generally most abundant in late winter and early spring throughout the estuary. Changes in diversity indices reflected variations in community structure, the influence of migratory species and juvenile fishes, and seasonal changes in dominance. Year-to-year fluctuations in abundance may be due, in part, to local hydrographic and meteorological conditions along the central Oregon coast.

Toxicity of sewage sludge toRhepoxynius abronius, a marine benthic amphipod

Relative toxicity of sewage sludges from six treatment plants was determined by the LC50 of sludge-sediment mixtures to the infaunal marine amphipod,Rhepoxynius abronius. LC50s were measured as the increase in the percent total volatile solids (TVS) of the mixture due to the addition of sludge required to kill 50% of the amphipods during a 10-day exposure. LC50s ranged from 2.83% TVS addition for sludge from the small, domestic community of Waldport, Oregon to <0.1% TVS addition for metropolitan, more industrialized sources in Los Angeles, California. The toxicity of the sludge-sediment mixtures is attributed primarily to chemical contamination rather than organic enrichment. Rank correlations between toxicity and specific chemicals were usually not statistically significant, indicating that different combinations of stresses involving multiple or unmeasured factors were probably responsible for observed effects. Integrative measures of contamination (oil/grease concentration; consensus ranking of contamination based on 15 parameters) were significantly correlated withR. abronius survival indicating that the more toxic sludges had a higher overall level of contamination.

Selected chemical contaminants in surface sediments of Commencement Bay and the tacoma Waterways, Washington, USA

Abstract Eight metals, 21 organic priority pollutants, and 11 other contaminants and contaminant-related sediment characteristics were measured in surface sediments (upper 2 cm) at 21 locations in Commencement Bay and the Tacoma Waterways, Washington. Summary statistics were calculated and statistical approaches (analysis of variance, multiple comparisons tests, cluster analysis and principal component analysis) were applied to subsets of the data to classify sediment contamination. Overall sediment contamination was highest in the Sitcum, City and Hylebos Waterways, intermediate in Commencement Bay, at the entrances to the Tacoma Waterways and in the outer reaches of the Blair and Hylebos Waterways, and lowest at the Blair Waterway turning basin, the mouth of the Puyallup River and at a reference site near Browns Point. High concentrations of some contaminants appeared to be related to proximity to sources of contaminants. Depositional vectors, and chemical adsorption processes may also influence the spatial distribution of sediment contamination in the study area. Results of simple and partial correlation analyses indicate that arsenic, iron and manganese may be more closely associated with the clay fraction, while cadmium, copper and polynuclear aromatic hydrocarbons may be more closely associated with the total organic carbon content of sediments. We were unable to discriminate statistically between the affinity of chromium, lead, zinc and phthalates with the % clay or the total organic carbon content of sediments.

Manganese and suspended matter in the Yaquina Estuary, Oregon

The longitudinal distribution of total suspended matter and total, dissolved, and particulate manganese in a small coastal plain estuary is described. The distribution of manganese is a consequence of estuarine circulation; a within-estuary maximum is inversely correlated with river flow, and is a function of residence time in the estuary, resuspension in the upper estuary, and desorption from particles introduced from within the estuary or from the river. The turbidity maximum is similarly most pronounced during low river flows. The upper estuary (salinity <15‰), comprising a small percentage of the total estuary volume during low flow, receives material from the river and along the bottom from the lower estuary; this material is returned to the water column by resuspension and desorption from estuarine and riverine particles. The lower estuary tends to damp out these processes because of the greater volume and (residence) time available for mixing.