pH effect on the susceptibility to parasitoid infection in the marine diatom Coscinodiscus spp. (Bacillariophyceae)

The pH on the frustule of individual cells of the marine centric diatoms Coscinodiscus granii and Coscinodiscus wailesii (Bacillariophyceae) was measured with pH microsensors in culture media with increasing pH values of 8.04, 8.14, and 8.22, respectively. In 85–96% of the C. granii cells the pH on the frustule was up to 0.4 units higher than that of the medium, reaching a maximum pH 8.95. Only in 2–3% the surface pH exceeded that of the medium by up to 0.7 pH units. These results strongly suggest that diatoms in batch cultures differ, at least temporarily, in their individual photosynthetic activities. Infection experiments with the parasitoid nanoflagellate Pirsonia diadema (Stramenopile) showed that flagellates failed to infect when the culture pH was 8.8 and above. pH measurements on freshly infected C. granii showed that the prevalence of infection was higher in tendency on diatoms with low surface pH. Application of these results to parasitoid-diatom interactions in natural waters suggests that within phytoplankton populations a strong photosynthetic activity might prevent diatom cells temporarily from infection by pH-sensitive parasitoids.     

How chemically stable is stabilized hazardous waste?

Bioassays can provide meaningful information about the relative toxicity of remediated soil samples, revealing the unwelcome toxic side effects produced by some cleanup projects. Section 121 of CERCLA's 1986 amendments calls for hazardous waste site remediations to permanently and significantly reduce the volume, toxicity, and mobility of hazardous substances, pollutants, and contaminants. Traditional engineering technology has focused on reducing volume and mobility, assuming that such reduction would lead to reductions in toxicity. Environmental scientists have argued, however, that such reductions are not always the result, but lack of consensus on how hazardous waste mixtures should be measured toxicologically has slowed development of integrated assessments. The aquatic and terrestrial bioassays discussed in this article are evaluated for various chemicals, mixtures of chemicals, and actual waste site chemical mixtures at a Superfund mobility reduction project in Kent, Washington. Results suggest that although remediation accomplished the primary objective of reducing mobility, it also introduced toxic effects. These tradeoffs must be viewed holistically when the ultimate performance of cleanup measures is judged.     

Symbiosis in sacoglossan opisthobranchs: functional capacity of symbiotic chloroplasts

It has been previously reported that many species of the order Sacoglossa (Mollusca: Opisthobranchia) contain algal chloroplasts within the cells of their digestive gland and maintain them in a symbiotic condition. In the present study, two species, Elysia hedgpethi Marcus and Placobranchus ianthobapsus Gould, were compared as to their abilities to retain functional chloroplasts in their tissues. Animals were starved for varying lengths of time, and the functional capacity of the plastids was ascertained at intervals. The chlorophyll content of whole animals, and the ability to incorporate ¹⁴CO₂ were used as the assay for functional capacity. E. hedgpethi decreased in chlorophyll content during starvation until the tenth day, when no chlorophyll was detectable spectrophoto-metrically. Incorporation of ¹⁴CO₂ paralleled the decline in chlorophyll, and was at control levels by the tenth day. P. ianthobapsus showed no decline in chlorophyll content over 27 days starvation, although the ability to incorporate ¹⁴CO₂ showed a decrease.     

Inter-seasonal maintenance of individual nest site preferences in hawksbill sea turtles

Within a single population of hawksbill sea turtles (Eretmochelys imbricata), we found a behavioral polymorphism for maternal nest site choice with respect to beach microhabitat characteristics. Some females preferred to nest in littoral forest and in places with overstory vegetation cover, and others preferred to nest in more open, deforested areas. Nest site choice was consistent within and between nesting seasons two years apart. This was not a result of females simply returning to the same location along the shoreline; beach sections used by individual turtles varied between seasons. Nest site choice was not influenced by changes in beach environment (e.g., beach width and foliage cover) or by changes in females' reproductive output (e.g., clutch size), suggesting that fidelity to particular microhabitats is a major determinant of the observed nesting patterns. Because hawksbills exhibit temperature-dependent sex determination, if the behavioral polymorphism in nest site choice has a genetic basis, as is plausible, then this would have implications for sex ratio evolution and offspring survival. By taking an individual-based approach to the study of maternal behavior we reveal previously overlooked individual variation and hope to provide some impetus for more detailed studies of nest site choice.     

Characteristics of animal-related motor vehicle crashes in select National Park Service units—United States, 1990–2013

Objectives: Nationally, animal–motor vehicle crashes (AVCs) account for 4.4% of all types of motor vehicle crashes (MVCs). AVCs are a safety risk for drivers and animals and many National Park Service (NPS) units (e.g., national park, national monument, or national parkway) have known AVC risk factors, including rural locations and substantial animal densities. We sought to describe conditions and circumstances involving AVCs to guide traffic and wildlife management for prevention of AVCs in select NPS units.

Methods: We conducted an analysis using NPS law enforcement MVC data. An MVC is a collision involving an in-transit motor vehicle that occurred or began on a public roadway. An AVC is characterized as a collision between a motor vehicle and an animal. A non-AVC is a crash between a motor vehicle and any object other than an animal or noncollision event (e.g., rollover crash). The final data for analysis included 54,068 records from 51 NPS units during 1990–2013. Counts and proportions were calculated for categorical variables and medians and ranges were calculated for continuous variables. We used Pearson’s chi-square to compare circumstances of AVCs and non-AVCs. Data were compiled at the park regional level; NPS parks are assigned to 1 of 7 regions based on the park’s location.

Results: AVCs accounted for 10.4% (5,643 of 54,068) of all MVCs from 51 NPS units. The Northeast (2,021 of 5,643; 35.8%) and Intermountain (1,180 of 5,643; 20.9%) regions had the largest percentage of the total AVC burden. November was the peak month for AVCs across all regions (881 of 5,643; 15.6%); however, seasonality varied by park geographic regions. The highest counts of AVCs were reported during fall for the National Capital, Northeast/Southeast, and Northeast regions; winter for the Southeast region; and summer for Intermountain and Pacific West regions.

Conclusions: AVCs represent a public health and wildlife safety concern for NPS units. AVCs in select NPS units were approximately 2-fold higher than the national percentage for AVCs. The peak season for AVCs varied by NPS region. Knowledge of region-specific seasonality patterns for AVCs can help NPS staff develop mitigation strategies for use primarily during peak AVC months. Improving AVC data collection might provide NPS with a more complete understanding of risk factors and seasonal trends for specific NPS units. By collecting information concerning the animal species hit, park managers can better understand the impacts of AVC to wildlife population health.