Effects of Sewage Pollution in the White River, Arkansas

Recently there has been much emphasis placed on the importance of leaf detritus processing to the energetics of stream invertebrates. This study was designed primarily to assess the effects of municipal effluent on the ability of a stream community to utilize leaf detritus, and secondarily to evaluate the extent of the pollution of the White River by the Fayetteville, Arkansas, effluent discharge. Physical and chemical water quality and benthos were sampled periodically at one station upstream and two stations downstream from the discharge, and in the Richland Creek tributary. Processing of leaf detritus was also studied at each site using 5 g of red oak (Quercus shumardi) leaves. The physicochemistry and benthic community structure indicated moderate to heavy pollution by the effluent. Despite this, leaf detritus processing rates were extremely rapid which indicated that leaf decomposition is virtually unaffected by macroinvertebrates

Benthic and Hyporheic Macroinvertebrate Distribution Within the Heads and Tails of Riffles During Baseflow Conditions

The distribution of lotic fauna is widely acknowledged to be patchy reflecting the interaction between biotic and abiotic factors. In an in-situ field study, the distribution of benthic and hyporheic invertebrates in the heads (downwelling) and tails (upwelling) of riffles were examined during stable baseflow conditions. Riffle heads were found to contain a greater proportion of interstitial fine sediment than riffle tails. Significant differences in the composition of benthic communities were associated with the amount of fine sediment. Riffle tail habitats supported a greater abundance and diversity of invertebrates sensitive to fine sediment such as EPT taxa. Shredder feeding taxa were more abundant in riffle heads suggesting greater availability of organic matter. In contrast, no significant differences in the hyporheic community were recorded between riffle heads and tails. We hypothesise that clogging of hyporheic interstices with fine sediments may have resulted in the homogenization of the invertebrate community by limiting faunal movement into the hyporheic zone at both the riffle head and tail. The results suggest that vertical hydrological exchange significantly influences the distribution of fine sediment and macroinvertebrate communities at the riffle scale

The Acid Test of Fluoride: How pH Modulates Toxicity

Background: It is not known why the ameloblasts responsible for dental enamel formation are uniquely sensitive to fluoride ($F^−$). Herein, we present a novel theory with supporting data to show that the low pH environment of maturating stage ameloblasts enhances their sensitivity to a given dose of $F^−$. Enamel formation is initiated in a neutral pH environment (secretory stage); however, the pH can fall to below 6.0 as most of the mineral precipitates (maturation stage). Low pH can facilitate entry of $F^−$ into cells. Here, we asked if $F^−$ was more toxic at low pH, as measured by increased cell stress and decreased cell function. Methodology/Principal Findings: Treatment of ameloblast-derived LS8 cells with $F^−$ at low pH reduced the threshold dose of $F^−$ required to phosphorylate stress-related proteins, PERK, eIF2α, JNK and c-jun. To assess protein secretion, LS8 cells were stably transduced with a secreted reporter, Gaussia luciferase, and secretion was quantified as a function of $F^−$ dose and pH. Luciferase secretion significantly decreased within 2 hr of $F^−$ treatment at low pH versus neutral pH, indicating increased functional toxicity. Rats given 100 ppm $F^−$ in their drinking water exhibited increased stress-mediated phosphorylation of eIF2α in maturation stage ameloblasts (pH<6.0) as compared to secretory stage ameloblasts (pH∼7.2). Intriguingly, $F^−$-treated rats demonstrated a striking decrease in transcripts expressed during the maturation stage of enamel development (Klk4 and Amtn). In contrast, the expression of secretory stage genes, AmelX, Ambn, Enam and Mmp20, was unaffected. Conclusions: The low pH environment of maturation stage ameloblasts facilitates the uptake of $F^−$, causing increased cell stress that compromises ameloblast function, resulting in dental fluorosis

Should digestion assays be used to estimate persistence of potential allergens in tests for safety of novel food proteins?

Food allergies affect an estimated 3 to 4% of adults and up to 8% of children in developed western countries. Results from in vitro simulated gastric digestion studies with purified proteins are routinely used to assess the allergenic potential of novel food proteins. The digestion of purified proteins in simulated gastric fluid typically progresses in an exponential fashion allowing persistence to be quantified using pseudo-first-order rate constants or half lives. However, the persistence of purified proteins in simulated gastric fluid is a poor predictor of the allergenic status of food proteins, potentially due to food matrix effects that can be significant in vivo. The evaluation of the persistence of novel proteins in whole, prepared food exposed to simulated gastric fluid may provide a more correlative result, but such assays should be thoroughly validated to demonstrate a predictive capacity before they are accepted to predict the allergenic potential of novel food proteins

Effects of Sewage Pollution in the White River, Arkansas on Benthos and Leaf Detritus Decomposition

Recently there has been much emphasis placed on the importance of leaf detritus processing to the energetics of stream invertebrates. This study was designed primarily to assess the effects of municipal effluent on the ability of a stream community to utilize leaf detritus, and secondarily to evaluate the extent of the pollution of the White River by the Fayetteville, Arkansas effluent discharge. Physical and chemical water quality, benthos, and fish were sampled periodically at one station upstream and two stations downstream from the discharge, and in the Richland Creek tributary. Processing of leaf detritus was studied at each site using 5 g packs of red oak (Quercus shumardi) leaves. Dissolved oxygen was far below recommended levels which resulted in a fish kill. Substantial increases in orthophosphate, ammonia, chlorides, conductivity and turbidity were observed downstream. Only 1 fish species (Morone chrysops) was collected downstream as it migrated through. The pattern of benthic species (25 immediately upstream, 8 just downstream, 17 downstream 8 km and 20 in a tributary) indicated heavy pollution. Despite this, leaf detritus processing rates were extremely rapid (K = 0.01-0.03) indicating that leaf decomposition is virtually unaffected by macroinvertebrates