Sublethal effects of zinc and municipal effluents on larvae of the red abalone Haliotis rufescens

Experiments were conducted to develop a sensitive sublethal toxicity test protocol to determine the toxicity of municipal wastewater effluents to larvae of the red abalone Haliotis rufescens. In multiple tests, fertilized abalone embryos were exposed for 48 h to dilutions of a reference toxicant, zinc sulfate, and to dilutions of primary-and secondary-treated effluents. The resulting veliger larvae were examined microscopically for larval shell abnormalities. In a longer flowthrough experiment, abalone were exposed for the entire larval phase, from the two-cell stage through metamorphosis, to compare zinc effects on metamorphosis with zinc effects on short-term larval shell development. Dissolved oxygen, pH, salinity and temperature were measured daily in test solutions, and zinc concentrations were verified by chemical analysis. No observed effect concentrations (NOECs) for zinc were 39±2.1 g l^-1 in three 48 h exposures, and 19 g l^-1 for the 9 d exposure through metamorphosis. Median effect concentrations (EC₅₀s) were 68±6.9 g l^-1 in 48 h tests and 50 g l^-1 in the 9 d test. Abalone larvae were affected at lower concentrations of primary than of secondary effluent.     

Ambient toxicity due to chlorpyrifos and diazinon in a central California coastal watershed

The Salinas River watershed along the central coast of California, U.S.A., supports rapidly growing urban areas and intensive agricultural operations. The river drains to an estuarine National Wildlife Refuge and a National Marine Sanctuary. The occurrence, spatial patterns, sources and causesof aquatic toxicity in the watershed were investigated by sampling four sites in the main river and four sites in representative tributaries during 15 surveys between September1998 and January 2000. In 96 hr toxicity tests, significant Ceriodaphnia dubia mortality was observed in 11% of the mainriver samples, 87% of the samples from a channel draining anurban/agricultural watershed, 13% of the samples fromchannels conveying agricultural tile drain runoff, and in 100% of the samples from a channel conveying agricultural surface furrow runoff. In six of nine toxicity identificationevaluations (TIEs), the organophosphate pesticides diazinon and/or chlorpyrifos were implicated as causes of observed toxicity, and these compounds were the most probable causes oftoxicity in two of the other three TIEs. Every sample collectedin the watershed that exhibited greater than 50% C. dubia mortality (n = 31) had sufficient diazinon and/or chlorpyrifos concentrations to account for the observed effects.Results are interpreted with respect to potential effects on other ecologically important species.     

The ‘hidden’ social costs of forestry offsets

The article quantifies the size of ‘hidden’ social costs that are incurred by forestry offsets in the voluntary market that promise to offset present emissions sometime in the future. It does this by estimating the difference between the social costs of carbon (C) emitted and of costs offset by removal of C from the atmosphere by reforestation/afforestation. All current attempts to make forestry offsets more reliable focus on quality control rather than the mismatch of the timing of emissions and their offset. Recommendations that follow from the analysis are twofold. First, that markets for carbon dioxide equivalent (CO2e) removals by voluntary offsets should be confined to the annual incremental removals actually achieved. Second, the promoters of voluntary offsets projects should declare the annual stream of carbon credits and debits expected so that buyers can place a present value on such projects.     

An Air Quality Data Analysis System for Interrelating Effects,Standards, and Needed Source Reductions: Part 6. Calculating Concentration Reductions Needed to Achieve the New National Ozone Standard

The new ozone National Ambient Air Quality Standard specifies that the expected number of days per calendar year that the 1 hour average ozone concentration can exceed 0.12 ppm must be equal to or less than 1. This paper describes a method to calculate design frequency, design concentration, and the percentage concentration reduction necessary to achieve this standard. The design frequency is once per year (1/365) if daily maximum hour ozone concentrations are available at a particular site for an equal number of days in summer (April through September) and winter (October through March). An equation is used to adjust design frequency as a function of the number of summer and winter samples available. The design concentration (the ambient concentration measured at the design frequency) needs to be reduced to 0.12 ppm. Graphical and digital methods for determining the design concentration are presented. Percentage concentration reductions needed to achieve the standard are calculated for each site which has ozone concentration data available in the National Aerometric Data Bank for at least half of the days in one summer of years 1975 through 1977. The degree of reduction calculated for the site with the highest concentrations in each county is indicated by shading on a map of the United States.     

Hazardous air pollutant emissions from gas-fired combustion sources: emissions and the effects of design and fuel type

Air emissions from gas-fired combustion devices such as boilers, process heaters, gas turbines and stationary reciprocating engines contain hazardous air pollutants (HAPs) subjected to consideration under the federal clean air act (CAA). This work presents a recently completed major research project to develop an understanding of HAP emissions from gas-fired boilers and process heaters and new HAP emission factors based on field emission tests of gas-fired external combustion devices used in the petroleum industry. The effect of combustion system design and operating parameters on HAP emissions determined by both field and research tests are discussed. Data from field tests of gas-fired petroleum industry boilers and heaters generally show very low emission levels of organic HAPs. A comparison of the emission data for boilers and process heaters, including units with and without various forms of NOx emission controls, showed no significant difference in organic HAP emission characteristics due to process or burner design. This conclusion is also supported by the results of research tests with different burner designs. Based on field tests of units fired with natural gas and various petroleum industry process gases and research tests in which gas composition was intentionally varied, organic HAP emissions were not determined to be significantly affected by the gas composition. Research data indicate that elevated organic HAP emission levels are found only under extreme operating conditions (starved air or high excess air combustion) associated with poor combustion.     

Are soil mite assemblages structured by the identity of native and invasive alien grasses?

Associations between plants and animals in aboveground communities are often predictable and specific. This has been exploited for the purposes of estimating the diversity of animal species based on the diversity of plant species. The introduction of invasive alien plants into an ecosystem can result in dramatic changes in both the native plant and animal assemblages. Few data exist at the species level to determine whether belowground animal assemblages share the same degree of association to plants. The hypotheses that soil mites (Acari) form assemblages specifically associated with different native grass species in an unmanipulated natural ecosystem and that invasive alien grasses will impact soil mite assemblage composition in this setting were tested. Soil mites sampled beneath five native and two invasive alien species of grasses at the Konza Prairie Biological Station, Kansas, USA, were similarly abundant, species rich, diverse, and taxonomically distinct. No mite species had affinities for a specific grass species. There was no evidence from analysis of similarity, canonical correspondence analysis, or a nonparametric assemblage analysis that the assemblage composition of soil mites was specific to grass species. Results suggest that soil mite assemblages were more related to characteristics of the plant assemblage as a whole or prevailing soil conditions. The most recent invasive alien grass did not support a successionally younger mite fauna, based on the ratio of mesostigmatid to oribatid mites, and neither of the two invasive grasses influenced mite assemblage structure, possibly because they had not yet substantially altered the soil environment. Our results suggest that extrapolations of soil mite diversity based on assumptions of plant specificity would be invalid.     

Identifying primary stressors impacting macroinvertebrates in the Salinas River (California, USA): relative effects of pesticides and suspended particles

Laboratory dose-response experiments with organophosphate and pyrethroid pesticides, and dose-response experiments with increasing particle loads were used to determine which of these stressors were likely responsible for the toxicity and macroinvertebrate impacts previously observed in the Salinas River. Experiments were conducted with the amphipod Hyalella azteca, the baetid mayfly Procloeon sp., and the midge Chironomus dilutus (Shobanov, formerly Chironomus tentans). The results indicate the primary stressor impacting H. azteca was pesticides, including chlorpyrifos and permethrin. The mayfly Procloeon sp. was sensitive to chlorpyrifos and permethrin within the range of concentrations of these pesticides measured in the river. Chironomus dilutus were sensitive to chlorpyrifos within the ranges of concentrations measured in the river. None of the species tested were affected by turbidity as high as 1000 NTUs. The current study shows that pesticides are more important acute stressors of macroinvertebrates than suspended sediments in the Salinas River.     

Understanding self-evaluations of effectiveness by forestry advisory committee members: a case of Ontario's Local Citizens Committee members

Researchers have devised many criteria that could assist with the development of an effective public participation process. Few studies, however, have linked these criteria to the effectiveness of decision-making resulting from these processes. We assess whether several criteria postulated by others for designing an effective decision-making process are associated with evaluations of the effectiveness of decision-making by advisory group members from a forest management planning process in Ontario, Canada. Data were collected by written questionnaires from 197 advisory group members in 2001. Four criteria were linked to the effectiveness evaluations including process control (influence), trust in decision-makers, information credibility, and process efficiency. The criterion of knowledge along with contextual variables related to experience, economic dependence on forestry, and geographical residence were not associated with evaluations of effectiveness.     

Short-term variation and long-term changes in the oceanographic environment and zooplankton community in the vicinity of a sub-Antarctic archipelago

 Mesozooplankton community structure in the vicinity of the Prince Edward Islands (PEIs) was investigated during six surveys conducted in late austral summer (April/May) from 1996 to 1999. Zooplankton samples were collected by oblique tows using a Bongo net fitted with 300-μm mesh. Surface temperature, average temperature and chlorophyll a were measured in conjunction with each net tow. The positions of the Sub-Antarctic Front (SAF) and the Antarctic Polar Front (APF), in relation to the islands, were determined by CTD and/or XBT transects to the west of the islands (upstream). Both fronts were characterized by a high degree of latitudinal variation. Changes in position of the fronts occurred rapidly, the SAF moving up to ∼120 km in a 2-week period. Consequently, the oceanographic environment in the vicinity of the PEIs was subject to a high degree of intra- and inter-survey variation. The positions of the SAF and APF appeared to have a significant impact on phytoplankton biomass in the vicinity of the PEIs, possibly through the alteration of local oceanographic flow dynamics. Water retention over the island shelf in 1996, associated with location of the SAF far to the north of the PEIs, corresponded to enhanced chlorophyll-a concentrations (∼1.54 mg m⁻³). Conversely, when the fronts were close to the islands, as in 1997 and 1999, higher current velocity limited water retention and chlorophyll-a concentrations in the inter-island region were relatively low (∼0.4 mg m⁻³). Cluster analyses showed that, in many instances, there was greater similarity among zooplankton communities from different surveys than among communities within surveys, indicating that short-term variability exceeded inter-annual variability. The population structure of the copepod Calanus simillimus indicated that there was inter-annual variation in the timing of the biological season. Differences in the population structure of species, and consequently their contribution to abundance and biomass, may therefore have been an important contributor to inter-annual variation in community structure. Evidence is provided of a long-term southward shift in the position of the SAF. It is postulated that this may affect the PEIs by increasing the proportion of allochthonous energy input, because the PEIs now lie in the path of the front, altering the tropho-dynamics of the island ecosystem. Lower mesozooplankton biomass associated with warmer sub-Antarctic water may have important negative consequences for higher trophic levels that depend on mesozooplankton for food. Received: 10 June 2000 / Accepted: 22 September 2000