Impacts of pesticides in a Central California estuary

Recent and past studies have documented the prevalence of pyrethroid and organophosphate pesticides in urban and agricultural watersheds in California. While toxic concentrations of these pesticides have been found in freshwater systems, there has been little research into their impacts in marine receiving waters. Our study investigated pesticide impacts in the Santa Maria River estuary, which provides critical habitat to numerous aquatic, terrestrial, and avian species on the central California coast. Runoff from irrigated agriculture constitutes a significant portion of Santa Maria River flow during most of the year, and a number of studies have documented pesticide occurrence and biological impacts in this watershed. Our study extended into the Santa Maria watershed coastal zone and measured pesticide concentrations throughout the estuary, including the water column and sediments. Biological effects were measured at the organism and community levels. Results of this study suggest the Santa Maria River estuary is impacted by current-use pesticides. The majority of water samples were highly toxic to invertebrates (Ceriodaphnia dubia and Hyalella azteca), and chemistry evidence suggests toxicity was associated with the organophosphate pesticide chlorpyrifos, pyrethroid pesticides, or mixtures of both classes of pesticides. A high percentage of sediment samples were also toxic in this estuary, and sediment toxicity occurred when mixtures of chlorpyrifos and pyrethroid pesticides exceeded established toxicity thresholds. Based on a Relative Benthic Index, Santa Maria estuary stations where benthic macroinvertebrate communities were assessed were degraded. Impacts in the Santa Maria River estuary were likely due to the proximity of this system to Orcutt Creek, the tributary which accounts for most of the flow to the lower Santa Maria River. Water and sediment samples from Orcutt Creek were highly toxic to invertebrates due to mixtures of the same pesticides measured in the estuary. This study suggests that the same pyrethroid and organophosphate pesticides that have been shown to cause water and sediment toxicity in urban and agriculture water bodies throughout California, have the potential to affect estuarine habitats. The results establish baseline data in the Santa Maria River estuary to allow evaluation of ecosystem improvement as management initiatives to reduce pesticide runoff are implemented in this watershed.     

Transport of Sewage Sludge From the 106-Mile Site - Results From an October Survey

Approximately 8 million tons of sewage sludge were disposed of annually at the 106-Mile Deepwater Municipal Sludge Dump Site (106-Mile Site) between 1987 and 1990. Beginning in 1988 and continuing to the present, the focus of monitoring at the 106-Mile Site moved towards improved understanding of the fate of the sludge. A survey conducted in October 1989 was designed to (1) detect the presence of any sludge particles that settle rapidly following disposal, (2) determine if sludge could be detected in the surface waters at locations away from the immediate disposal site, and (3) determine if water quality was degraded, by assessing whether the Environmental Protection Agency's marine water quality criteria were being exceeded.

The survey showed that the sludge does have a rapidly settling component composed of organic floc. mineral grains, and other heavy, gritlike particles, all of which are relatively large. These particles may settle at rates of between 8 and 180 m h^-1 and may reach the sea floor within 1 to 13 days following disposal. Even though a rapidly settling component is present in the sludge, a significant fraction of the sludge was detectable in the form of intact sludge plumes in the upper 35 m of the water column at least 15 km from the Site. in addition, unique tracers of sludge such as xylem tracheids and Clostridium perfringens plus elevated total suspended solids and trace metals concentrations, were found at locations up to 40 km from the Site. the presence of these tracers correspond with in situ transmissometry data suggesting that a fraction of the sludge was remaining in the near-surface waters above the seasonal pycnocline. Concentrations of metals were below EPA chronic marine water quality criteria, which indicates that the water quality downstream of the Site was not impaired. the detection of sludge downstream of the 106-Mile Site is consistent with the southwestward movement of the surface water mass during the survey, as recorded by satellite-tracked surface drifters and current vectors derived from a current meter moored at 100-m depth immediately west of the Site. Near-surface transport was generally towards the southwest at a speed of approximately 22 cm s^-1*.     

The structure of work values: A cross cultural comparison

Several years ago a research project on work values was originated. The study strived to examine the relative importance of work value items and to analyze the structure of the domain for samples from various cultural environments. A facet definition of work values was suggested that provided guidelines for constructing the Work Values Questionnaire and the formulation of hypotheses regarding the structure of relationships among components of work values. Based on data collected from 2280 respondents in eight countries the hypotheses were tested by means of Guttman's Smallest Space Analysis. The results support the hypotheses. An empirical double-ordered conceptual system, a radex structure, was obtained in each of the samples reflecting the facets of the definition: modality of outcome — cognitive, affective and instrumental, and system - performance contingency — reward, resource. In terms of the issue of cultural differences the results indicate the presence of cultural differences in the rating of a limited number of specific values. These differences are only minor variations within a much broader pattern of structural similarity. The fact that essentially the same structure was obtained in eight independent samples lends substantial support to the definitional framework of work values suggested.     

Temporal and spatial variation in bacterial production in the water column over a coral reef

Production and doubling times of the bacterial populations in the water around and over the reefs at Lizard Island, Great Barrier Reef were measured during summer and winter, 1982 and 1983. Bacterial productivity, determined from the rate of tritiated thymidine incorporation into DNA, was high over the reef flats and a Thalassia hemprichii sand flat (28 to 58 g Cl^-1 d^-1). Bacterial growth rates increased during the day and fell at night over the reef flats and seagrass bed. Growth rates were slower over the reef front and in open water. Doubling times ranged from about 2 d in the open water to about 3 h over the reef flat in summer. As numbers did not increase, grazing was probably intense on the reef flats. Growth rates were much slower in winter. The main source of organic nutrient used by the bacteria was probably mucus released following photosynthesis in the corals. The cyanobacterium Synechococcus sp. was sometimes very numerous, especially in summer when 2×10⁸ cells l^-1 were recorded in one water mass. The number of bacteria was also very high in summer, with values ranging from 1×10⁹ to 2.5×10⁹l^-1.     

Reply to Discussion

In the Discussion, Nash et al. (2019) estimate the seasonal change in groundwater volume for a portion of the restored Sierra Nevada Meadow that we evaluated (Hunt et al. 2018) and use this estimate as an upper bound on the possible contribution to flow that is attributable to restoration. The authors conclude that raising the channel bed elevation and reconnecting the meadow floodplain most likely reduced summer streamflow. In contrast, we report at least a fivefold increase in baseflow from the meadow in the years following restoration. In addition, we observed that, after restoration, the previously intermittent stream below the meadow flowed continuously throughout the summer months, despite record drought conditions, and in 2015, the lowest snowpack on record. We suggest that the groundwater budget presented in the Discussion may not adequately represent conditions within the meadow because the authors extrapolate from 5 near‐channel groundwater wells across 62 ha of meadow and assume an area of influence that is approximately one‐sixth of the meadow area. We conclude that the conversion of an intermittent stream to perennial flow during drought conditions is a stronger check on our gauge data than the groundwater budget presented in the Discussion.     

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.