Four nutrient enrichment bioassay experiments were conducted in Sycamore Creek, Arizona, during summer and autumn 1983. In two experiments, nitrogen and phosphorus were added alone and in combination while in the other experiments nitrogen was added singly. In experiments involving enrichment of both nutrient-diffusing substrates (clay flowerpots) and streamwater overlying tileigravel artificia...

Stream grazers have a major impact on food web structure and the productivity of stream ecosystems; however, studies on the longitudinal (upstream versus downstream) and temporal changes in their drift dynamics and resulting distributions remain limited. Here, we investigated the longitudinal and temporal distributions and drift propensity of a trichopteran grazer, the caddisfly, Micrasema quad...

Hydrogen stable isotopes (δ2H) have recently been used to complement δ13C and δ15N in food web studies due to their potentially greater power to separate sources of organic matter in aquatic food webs. However, uncertainties remain regarding the use of δ2H, since little is known about the potential variation in the amount of exchangeable hydrogen (Hex) among common sample materials or the patte...

The neurotoxin BMAA (β-N-methylamino-l-alanine) and its isomer DAB (2,4-diaminobutyric acid) have been detected in seafood worldwide, including in Thau lagoon (French Mediterranean Sea). A cluster of amyotrophic lateral sclerosis (ALS), a neurodegenerative disease associated with BMAA, has also been observed in this region. Mussels, periphyton (i.e. biofilms attached to mussels) and plankton we...

Phosphorus (P) can leach from topsoil in inorganic and organic forms. While some evidence has shown P (orthophosphate) to depth soils, less is known of dissolved (DOP). This not helped by a paucity DOP data for groundwater. We hypothesized that species would greater amounts at faster rate through aquifer gravels than orthophosphate. applied superphosphate with or without dung low P-sorption soi...

Sampling of three sites on the upper Tongariro River was carried out in summer (January) 1996 to evaluate impacts of the Mt Ruapehu eruption and subsequent flushings of accumulated sediment from behind Rangipo Barrage on substrate, periphyton, invertebrates and blue duck (Hymenolaimus malacorhynchos) diet. Levels of sand and gravels increased markedly in summer 1996 in blue duck feeding habitat...

A variety of anthropogenic influences threaten the Everglades. One of the most publicized perturbations to the system has been excessive inputs of phosphorus (P). The Everglades is a P-limited ecosystem, and its biota are adapted for survival under highly oligotrophic conditions (e.g., Browder 1982; Steward and Ornes 1975a,b; Swift and Nicholas 1987; Davis 1991). Indeed, numerous experiments ha...

Consumption of periphyton is a potentially important route of metal exposure to benthic invertebrate grazers. The present study examined the bioaccumulation kinetics of dissolved and dietary Cd and Cu in five species of mayflies (class Insecta). Artificial stream water and benthic diatoms were separately labeled with enriched stable metal isotopes to determine physiological rate constants used ...