Feeding ecology ofLeitoscoloplos fragilis

The present study examines the effects of density ofLeitoscoloplos fragilis and of fine sediment on benthic microalgal abundance and production in laboratory microcosms, and the effects of fine sediment on diffusive transport of ammonia. Microcosms having different densities ofLeitoscoloplos fragilis (Verrill, 1873) were determined in sediment collected from one of two field stations (each containing a different amount of fine particles <125 m) from Cape Henlopen, Delaware, USA, in August 1986. The worms were acclimated in a recirculating seawater system for two months prior to experiments. Chlorophylla concentrations were highest in sediments with less fine particles (<125 m). Benthic diatom production, total microbenthic metabolic activity, and concentrations of pore-water ammonia were higher in sediment microcosms containing high densities of worms.L. fragilis grew more in microcosms containing less fine particles and higher worm densities. The upward flux of ammonia across the sediment-water interface was higher in sediments with less fine particles. A greater abundance of fine particles in these sediments impedes the upward flux of ammonia to surface and nearsurface diatoms. The coupling between population density and diatom production, which can be altered by fine-particle abundance could control the distribution and stability of populations ofL. fragilis.     

Experimental variability in characterization of cyfluthrin sorption to soil

To assess the risk of a pesticide to leach to groundwater or to run off to surface water after application, it is necessary to characterize the sorption of the pesticide to soil. For pyrethroids, their hydrophobicity, strong sorption to various materials, and low solubility make it difficult to accurately characterize sorption processes. The objective of this research was to evaluate the variability in cyfluthrin ((RS)-alpha -cyano-4-fluoro-3-phenoxybenzyl (1RS,3RS;1RS,3SR)-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate) sorption to soil as affected by experiment conditions. To minimize cyfluthrin sorption on the walls of glass, silanized-glass, stainless steel, and PTFE centrifuge tubes, cyfluthrin solution was added to aqueous soil slurries or directly to soil, after which it was equilibrated with aqueous solution. Depending on the soil, variation in sorption coefficients, Koc, obtained using different experimental methodologies with one soil can be comparable to the variation in Koc values obtained for soils with different physical and chemical properties using one method. Koc values for cyfluthrin ranged from 56,000 to 300,000 L kg-1. Sorption methodology needs to be evaluated before sorption coefficients are used in predictive transport models.     

Depression of feeding and growth rates of the seastar Evasterias troschelii during long-term exposure to the water-soluble fraction of crude oil

To test the effect of petroleum hydrocarbons on predation by the seastar Evasterias troschelii (Stimpson, 1862) on the mussel Mytilus edulis (L.), we exposed the predator with the prey to six concentrations of the water-soluble fraction (WSF) of Cook Inlet crude oil. Seastars and mussels were collected at Auke Bay, Alaska, in November 1980. During a 28 d exposure in a flow-through system, seastars were more sensitive to the WSF than mussels: the LC₅₀ for the seastars was 0.82 ppm at Day 19 and, although no mussels were exposed to WSF for more than 12 d, none died. Daily feeding rates (whether in terms of number of mussels seastar^-1 d^-1 or dry weight of mussels seastar^-1 d^-1) were significantly reduced at all concentrations above 0.12 ppm. At 0.20, 0.28 and 0.72 ppm WSF, daily feeding rates (in terms of dry weight of mussels) were, respectively, 53, 37, and 5% of the control rate; at the two highest concentrations (0.97 and 1.31 ppm WSF), the seastars did not feed. Seastars at concentrations greater than 0.12 ppm WSF grew slower than individuals from the control group and the 0.12 ppm-treatment group combined. These laboratory results show that E. troschelii is more sensitive to chronic low levels of the WSF of crude oil. The possibility that such oil pollution could reduce predation and permit M. edulis to monopolize the low intertidal zone of southern Alaska remains to be studied.     

Biomass of the invertebrate megabenthos from 500 to 4100 m in the northeast Atlantic Ocean

Data are presented on the biomass of the invertebrate megafauna at 22 stations on the continental slope in the Porcupine Seabight (PSB) (northeast Atlantic Ocean). Samples were collected between 1980 and 1982. Several units of biomass are used, all of which illustrate a decrease by a factor of about 30 from 500 to 4100 m. Lognormal curves were fitted to the data, the gradients of which were very similar for all biomass units and similar to the value for a transect down the continental slope in the western Atlantic. Biomass levels in the PSB are compared with those from other deep-sea environments. Some published values are more than ten times higher than the values reported here, while others are less than a tenth. The reasons for these differences and trends are discussed in terms of food supply. Sampling variability was examined at two stations, but by chance one (at 1300 m) appeared to encompass a sharp faunal discontinuity of the dominant fauna and the other (at 4000 m) contained very small numbers of large animals. For these reasons, sample variability was high at the repeat stations. Suspension-feeders and crustaceans dominated the biomass at upper-slope depths, while echinoderms were dominant on the middle and lower slope. As a result of this phyletic change, there was a small but insignificant decrease in mean body weight with increasing depth. Within phyla there was also a small but insignificant decrease with depth. If large species are excluded from the biomass/depth regression, the gradient changes considerably, demonstrating the increasing importance of small species at greater depths. The size distribution of megafaunal biomass was examined at several stations. This indicated that the megafauna form a functional group distinct from the macrofauna, just as the macrofauna are distinct from the meiofauna.     

EROSION ON LOGGING ROADS IN REDWOOD CREEK,NORTHWESTERN CALIFORNIA1

Road-related erosion was estimated by measuring 100 randomly located plots on a 180 km road network in the middle reach of R'dwood Creek in northwestern California. The estimated erosion ratn of 177 m³ km^-1 was contrasted with two earlier studies in nearby parts of the same watershed. A sizable proportion of the great reduction in erosion from that reported in the earlier studies is attributed to changes in forest practice rules. Those changes have resulted in better placement and sizing of culverts and, especially, to less reliance on culverts to handle runoff from logging roads.     

Acoustically detected year-round presence of right whales in an urbanized migration corridor

Species' conservation relies on understanding their seasonal habitats and migration routes. North Atlantic right whales (Eubalaena glacialis), listed as endangered under the U.S. Endangered Species Act, migrate from the southeastern U.S. coast to Cape Cod Bay, Massachusetts, a federally designated critical habitat, from February through May to feed. The whales then continue north across the Gulf of Maine to northern waters (e.g., Bay of Fundy). To enter Cape Cod Bay, right whales must traverse an area of dense shipping and fishing activity in Massachusetts Bay, where there are no mandatory regulations for the protection of right whales or management of their habitat. We used passive acoustic recordings of right whales collected in Massachusetts Bay from May 2007 through October 2010 to determine the annual spatial and temporal distribution of the whales and their calling activity. We detected right whales in the bay throughout the year, in contrast to results from visual surveys. Right whales were detected on at least 24% of days in each month, with the exception of June 2007, in which there were no detections. Averaged over all years, right whale calls were most abundant from February through May. During this period, calls were most frequent between 17:00 and 20:00 local time; no diel pattern was apparent in other months. The spatial distribution of the approximate locations of calling whales suggests they may use Massachusetts Bay as a conduit to Cape Cod Bay in the spring and as they move between the Gulf of Maine and waters to the south in September through December. Although it is unclear how dependent right whales are on the bay, the discovery of their widespread presence in Massachusetts Bay throughout the year suggests this region may need to be managed to reduce the probability of collisions with ships and entanglement in fishing gear.