Effects of Photoperiod on the Occurrence of Symbiotic Rotifers, Nematodes and Branchiobdellids of Two Orconectid Species of Crayfishes

Representative specimens of O. immunis and O. pellucidus were brought to the laboratory in order to investigate the influence of light on the occurrence of the symbionts encountered during the preliminary field study. After one week of acclimating the crayfishes they were distributed among environments control chambers that permitted exposure of the hosts and symbionts to 1) continuous light (C.L.), 2) a daily cycle of 12 hours of light and 12 hours of darkness (12L-12D) and 3) continuous darkness (C.D.)

Zn and Cu Isotopes As Tracers of Anthropogenic Contamination in a Sediment Core from an Urban Lake

In this work, we use stable Zn and Cu isotopes to identify the sources and timing of the deposition of these metals in a sediment core from Lake Ballinger near Seattle, Washington, USA. The base of the Lake Ballinger core predates settlement in the region, while the upper sections record the effects of atmospheric emissions from a nearby smelter and rapid urbanization of the watershed. δ66Zn and δ65Cu varied by 0.50‰ and 0.29‰, respectively, over the 500 year core record. Isotopic changes were correlated with the presmelter period (~1450 to 1900 with δ66Zn = +0.39‰ ± 0.09‰ and δ65Cu = +0.77‰ ± 0.06‰), period of smelter operation (1900 to 1985 with δ66Zn = +0.14 ± 0.06‰ and δ65Cu = +0.94 ± 0.10‰), and postsmelting/stable urban land use period (post 1985 with δ66Zn = 0.00 ± 0.10‰ and δ65Cu = +0.82‰ ± 0.12‰). Rapid early urbanization during the post World War II era increased metal loading to the lake but did not significantly alter the δ66Zn and δ65Cu, suggesting that increased metal loads during this time were derived mainly from mobilization of historically contaminated soils. Urban sources of Cu and Zn were dominant since the smelter closed in the 1980s, and the δ66Zn measured in tire samples suggests tire wear is a likely source of Zn

Acute Toxicity of Runoff from Sealcoated Pavement to <i>Ceriodaphnia dubia</i> and <i>Pimephales promelas</i>

Runoff from coal-tar-based (CT) sealcoated pavement is a source of polycyclic aromatic hydrocarbons (PAHs) and <i>N</i>-heterocycles to surface waters. We investigated acute toxicity of simulated runoff collected from 5 h to 111 days after application of CT sealcoat and from 4 h to 36 days after application of asphalt-based sealcoat containing about 7% CT sealcoat (AS/CT-blend). <i>Ceriodaphnia dubia</i> (cladocerans) and <i>Pimephales promelas</i> (fathead minnows) were exposed in the laboratory to undiluted and 1:10 diluted runoff for 48 h, then transferred to control water and exposed to 4 h of ultraviolet radiation (UVR). Mortality following exposure to undiluted runoff from unsealed asphalt pavement and UVR was ≤10% in all treatments. Test organisms exposed to undiluted CT runoff samples collected during the 3 days (<i>C. dubia</i>) or 36 days (<i>P. promelas</i>) following sealcoat application experienced 100% mortality prior to UVR exposure; with UVR exposure, mortality was 100% for runoff collected across the entire sampling period. Phototoxic-equivalent PAH concentrations and mortality demonstrated an exposure-response relation. The results indicate that runoff remains acutely toxic for weeks to months after CT sealcoat application