Nutrient concentration, stoichiometry, and timing of delivery can regulate cyanobacterial dominance and microcystin production in rivers.

Riverine cyanobacterial blooms are increasing worldwide and are driven in large part by eutrophication. Despite substantial data on nutrient/bloom relationships in lakes and reservoirs, our understanding of nutrient mechanisms driving cyanobacterial blooms in rivers remains limited as rivers can have more complex temporal and spatial nutrient delivery. This study investigated how nutrient conditions influence cyanobacterial dominance and microcystin production in river phytoplankton.

Periphyton responses to nutrient and atrazine mixtures introduced through agricultural runoff.

Agricultural runoff often contains pollutants with antagonistic impacts. The individual influence of nutrients and atrazine on periphyton has been extensively studied, but their impact when introduced together and with multiple agricultural pollutants is less clear. We simulated a field-scale runoff pulse into a riverine wetland that mimicked pollutant composition typical of field runoff of the Mississippi River Alluvial Plain.

Mitigating agrichemicals from an artificial runoff event using a managed riverine wetland.

We examined the mitigation efficiency of a managed riverine wetland amended with a mixture of suspended sediment, two nutrients (nitrogen and phosphorus), and three pesticides (atrazine, metolachlor, and permethrin) during a simulated agricultural runoff event. Hydrologic management of the 500 m-long, 25 m-wide riverine wetland was done by adding weirs at both ends. The agrichemical mixture was amended to the wetland at the upstream weir simulating a four-hour, ~1cm rainfall event from a 16ha agricultural field.

Responses of Hyalella azteca and phytoplankton to a simulated agricultural runoff event in a managed backwater wetland.

We assessed the aqueous toxicity mitigation capacity of a hydrologically managed floodplain wetland following a synthetic runoff event amended with a mixture of sediments, nutrients (nitrogen and phosphorus), and pesticides (atrazine, S-metolachlor, and permethrin) using 48-h Hyalella azteca survival and phytoplankton pigment, chlorophyll a. The runoff event simulated a 1h, 1.27 cm rainfall event from a 16 ha agricultural field.

Macromolecular response of individual algal cells to nutrient and atrazine mixtures within biofilms.

Pollutant effects on biofilm physiology are difficult to assess due to differential susceptibility of species and difficulty separating individual species for analysis. Also, measuring whole assemblage responses such as metabolism can mask species-specific responses, as some species may decrease and others increase metabolic activity. Physiological responses can add information to compositional data, and may be a more sensitive indicator of effect.

Consumer return chronology alters recovery trajectory of stream ecosystem structure and function following drought.

Consumers are increasingly being recognized as important drivers of ecological succession, yet it is still hard to predict the nature and direction of consumer effects in nonequilibrium environments. We used stream consumer exclosures and large outdoor mesocosms to study the impact of macroconsumers (i.e.