<p> Amphipods are found in large numbers from the top elevation at the Nature Institute (TNI) in Madison County, IL to lower areas of the stream that flow into the Mississippi River. Amphipod success depends greatly on their ability to survive dynamic streams with changing flow and physical conditions. It would be thought that by the end of spring rains, all aquatic organisms would be washed downstream. After observations of persistence of amphipods at the highest reaches of a small fishless stream that experiences relatively severe flooding, the present study sought to determine if a relationship existed between stream elevation and microhabitat type with respect to amphipod abundance. Do certain microhabitats serve as systematically better refuges in flooding streams? This study also sought to determine if there was a relationship between amphipod size and stream elevation. Do larger or smaller amphipods persists better at different stream elevations? Two surveys were conducted in July 2015 with sampling at 8 different elevation zones which included 5 microhabitats. One survey was conducted in August 2015 at 10 different elevation zones (8 of which were repeat areas from July), with samples taken from various elevations along the stream from 5 microhabitats. A total of 2,616 amphipods (Gammarus pseudolimnaeus) were collected over the two-month time period, collected, counted and body length measured. Results did not show a relationship between amphipod body length and stream elevation, nor was there a relationship between amphipod abundance and stream elevation.</p>

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

The physiological effects of a natural perturbation (fluctuating. temperatures) and a petroleum-induced perturbation. (dimethylnaphthalene-contaminated food) on the grass shrimp. Palaemonetes pugio were compared. The resistance of shrimp to. environmental challenge, oxygen consumption rates (Vo(,2)) and(' ). several physiological indices of stress were determined after a 32. day exposure to fluctuating temperatures (FT) (18-22�C) and/or dimethylnaphthalene (DMN)-contaminated food (0.24 (mu)g DMN/g wet wt) and again after a 16 day recovery period of stable temperatures (20�C) and uncontaminated food. Both FT and DMN-contaminated food reduced survival to the challenge of hypoxia + reduced salinity. FT were quantitatively more stressful than either stable temperatures or DMN-contaminated food. After the recovery period, FT did not affect survival to hypoxia, while shrimp, which had ingested DMN-contaminated food, exhibited enhanced survival to hypoxia. Ingestion of DMN-contaminated food for 32 days resulted in elevated Vo(,2)(' )in shrimp exposed to declining oxygen concentrations. After the 32 day exposure period, FT had no significant effect on(' )Vo(,2) at 15�C, 20�C and 25�C, tissue Vo(,2),(' )Vo(,2) in declining oxygen and hemolymph copper concentrations. After the 16 day recovery period, shrimp from the FT regime exhibited depressed(' )Vo(,2) when exposed to 25�C but not to 15�C. These depressed respiratory rates were offset by the stimulatory effect of DMN-contaminated food. The ratio of oxygen consumed to nitrogen excreted wwas elevated after the exposure and recovery periods in shrimp exposed to both FT and DMN-contaminated food at the same time. Water flux rates were elevated by FT after the exposure and recovery periods but not when DMN-contaminated food was also ingested. Both water flux rates and the ratio of oxygen consumed to nitrogen excreted were elevated in all shrimp after the recovery period relative to levels observed after the exposure period. After the exposure period, FT induced elevated hemolymph acid phosphatase activities in shrimp exposed to hypoxia. After the recovery period, hypoxia induced elevated hemolymph acid phosphatase activities in shrimp which had ingested nothing but uncontaminated food relative to those ingesting DMN-contaminated food.