Faith A. Cole

Temporal changes in the benthos along a pollution gradient: Discriminating the effect of natural phenomena from sewage-industrial wastewater effects

Abstract As pollution from the Los Angeles County Sanitation Districts (LACSD) outfalls decreased between 1980 and 1983, the macrobenthic community partially recovered and surficial (0–2 cm deep) sediment contamination and toxicity decreased at 60 m water depth along a pollution gradient from the outfalls. Pollution from the LACSD outfalls continued to decrease but macrobenthic conditions and surficial sediment quality deteriorated 1 km, was unchanged 3 km, and improved 5–15 km from the LACSD outfalls between 1983 and 1986. The net effect of natural phenomena is indicated when ecosystem changes occur in the opposite direction from that expected under prevailing pollution conditions. Our data suggest that the net effect of natural phenomena (e.g. winter storms, El Nino) on the benthos was greater than LACSD wastewater effects 1 km, about equal to LACSD wastewater effects 3 km, and less than the LACSD wastewater effects 5–15 km from the outfalls at the LACSD 1983–1986 mass emission rate. Surficial sediment samples collected beyond the 1 km station from the LACSD outfalls probably represented ⪢ 3 years of natural + effluent particulates accumulation, and they were, therefore, better suited for detecting long-term trends than for testing short-term temporal variability in surficial sediment contamination and toxicity. Nevertheless, some contaminants in the surficial sediments significantly increased between 1983 and 1986, probably primarily reflecting renewed wastewater effects near the outfalls and the effects of natural phenomena (e.g. storm-induced sediment transport or erosion) further from the outfalls. Since natural phenomena may have an effect on the benthos ≥ 3 years of LACSD wastewater effects, short-term benthic changes must be interpreted cautiously at the study site.

Life History and Productivity of the Phoxocephalid Amphipod Rhepoxynius Abronius (Barnard)

ABSTRACT Rhepoxyniusabronius (Barnard) (Amphipoda: Phoxocephalidae) is a predominantly subtidal species of the North American Pacific coast. It is also found sub- and intertidally within the polyhaline region of estuaries of Oregon and Washington. Within the Yaquina Bay estuary, Oregon, R. abronius is an annual species producing one or two broods per year. Recruitment occurs over an extended period from mid to late winter through summer. Mortality was 20-25% per month during mid to late spring through fall, and was low in winter through early spring. Mortality may be largely due to predation. Mortality of males appears higher than that of females during the reproductive season. The annual range in biomass was 40– 180 mg ash-free dry weight (AFDW)/0.5 m2, averaging 104 mg AFDW/0.5 m2. Secondary production was 160-216 mg AFDW/0.5 m2/yr and the annual ratio of production to mean biomass was 1.54-2.08. Production and the production: biomass ratio are similar to values reported for other marine amphipods with one or fewer generations per year.

Optimal benthic macrofaunal sampling protocol for detecting differences among four habitats in Willapa Bay, Washington, USA

As part of an effort to estimate estuarine habitat values with respect to ecological indicators of benthic macrofaunal community condition, an optimal (effective and least costly) sampling protocol (sample unit size [area x depth], sieve mesh size, and sample number [n]) was determined. The goal was to use four ecological indicators (number of species, abundance, biomass, and fish and crab prey abundance) to detect differences among four intertidal habitats in Willapa Bay, Washington, United States. The four habitats were eelgrass (Zostera marina), Atlantic cordgrass (Spartina alterniflora), mud shrimp (Upogebia pugettensis), and ghost shrimp (Neotrypaea californiensis). Four sample unit areas (0.005, 0.010, 0.015, and 0.020 m2), two sample unit depths (0–5 and 0–10 cm), and two sieve mesh sizes (1.0 and 0.5 mm) were evaluated. The optimal sampling protocol was defined as the least costly protocol capable of reliably (statistical power, 1−β≥0.80) detecting significant (α=0.05) differences among ≥4 of the 6 pairwise habitat contrasts by ANOVA on all four ecological indicators. The relative cost of each sampling protocol was estimated as a direct function of the sample unit size and number and the cost-in-processing-time ratios of 1 (5 cm deep):1.7 (10 cm deep) and 1 (≥1.0 mm macrofauna size fraction); 2.5 (≥0.5 mm macrofauna size fraction), which were taken from previous studies. The optimal sampling protocol was 15–20, 0.01-m2×5-cm deep, 0.5-mm mesh samples per habitat.

Optimum macrobenthic sampling protocol for detecting pollution impacts in the southern California bight

The optimum macrobenthic sampling protocol [sampling unit, sieve mesh size, and sample size (n)] was determined for detecting ecologically important pollution impacts in the Southern California Bight, U.S.A. Cost, in laboratory processing time, was determined for samples obtained using fourteen sampling units (0.005–0.1 m2 surface area) and two sieve mesh sizes (1.0 and 0.5 mm). Statistical power analyses for t-tests of means were performed to estimate the minimum sample size (nmin) needed to reliably (α=0.05, 1−β≧0.95) reject the null hypothesis of no difference between a reference and both a stimulated and a degraded station on twelve measures of community structure. The optimum sampling protocol for detecting impacts was determined as that with the lowest total cost ×nmin on most measures.Five replicate, 0.02 m2×5 cm deep, 1.0 mm mesh samples per station could reliably distinguish reference from impacted conditions on nine or ten measures of community structure at less than one quarter of the cost of the standard sampling protocol of 5 replicate, 0.1 m2, 1.0 mm mesh samples per station. About 5 replicate, small (<0.1 m2), 1.0 mm mesh samples per station may often be optimal for detecting important structural changes in macrobenthic communities with naturally high species richness and abundance.

Ecological periodic tables for nekton usage of four US Pacific Northwest estuarine habitats

We compared the species composition and abundance of the total nekton community, using the Bray–Curtis similarity coefficient, and mean total nekton, fish and crab species richness, abundance and biomass, and shrimp abundance across four intertidal habitats in a US Pacific Northwest estuary: (i) eelgrass (Zostera marina); (ii) burrowing mud shrimp (Upogebia pugettensis); (iii) burrowing ghost shrimp (Neotrypaea californiensis); and (iv) unvegetated sand. Field sampling was conducted during daytime high tides, and was quantitative, stratified-by-habitat, randomized, and estuary-wide. More than 10 000 nekton specimens belonging to 64 taxa were collected in 454 samples during 10 sampling periods, each approximately one-month-long (from June to November), over 3 years (1998–2000). Non-metric multidimensional scaling analyses revealed annually recurring across-habitat patterns in total nekton Bray–Curtis similarity. Two-way (habitat, year) analyses of variance revealed annually recurring across-habitat pattern...