Frank deNoyelles

The Responses of Plankton Communities in Experimental Ponds to Atrazine, the Most Heavily Used Pesticide in the United States

Experimental ponds received single additions of the herbicide atrazine in concentra- tions of 20 and 500 gg/L, and were compared to control ponds for 136 d. Atrazine is an inhibitor of photosynthesis, and both concentrations depressed phytoplankton growth in the ponds within a few days. This was followed by successional changes leading to the establishment of species of phyto- plankton more resistant to inhibition by atrazine. Laboratory studies verified this resistance and verified effects on other species at concentrations of atrazine as low as 1-5 Jig/L. When and to what extent resistant species appeared in the phytoplankton communities differed with treatment. At the atrazine concentration of 500 gg/L, there was a delayed appearance but eventually a greater biomass and persistence of these species. The grazing zooplankton influenced these differences and were in turn affected by them. Natural interactions such as competition and predation among the species of the communities greatly affected their responses to the toxic chemical. The importance of atrazine as an environmental pollutant is suggested by these responses to concentrations of 1-5 gg/L, which are common downstream in many agricultural watersheds, 20 /Ig/L, which is the high level found in these waters, and 500 gg/L, which is the high level found in waters directly adjacent to treated fields. zine in experimental ponds. This study will demon- strate both the immediate inhibition of certain species and the secondary effects which such a response has on other species. Species with some tolerance to the effects of the chemical will be identified in the com- munities, and their role in the changing conditions will also be considered. Atrazine (2-chloro-4-ethylamino-6-isopropylamino- s-triazine) is the single most heavily used pesticide in the United States. In 1976, 41 million kilograms (active ingredient) of this herbicide were applied on farms in

The ecology of algal biodiesel production

Sustainable energy production represents one of the most formidable problems of the 21st century, and plant-based biofuels offer significant promise. We summarize the potential advantages of using pond-grown microalgae as feedstocks relative to conventional terrestrial biofuel crop production. We show how pond-based algal biofuel production, which requires significantly less land area than agricultural crop-based biofuel systems, can offer additional ecological benefits by reducing anthropogenic pollutant releases to the environment and by requiring much lower water subsidies. We also demonstrate how key principles drawn from the science of ecology can be used to design efficient pond-based microalgal systems for the production of biodiesel fuels.

Photosynthetically Elevated pH as a Factor in Zooplankton Mortality in Nutrient Enriched Ponds

During a nutrient enrichment study of eight small ponds, the mortality of crustacean zooplankton species was investigated using a life table technique. There was close agreement between high pH values and the disappearance of crustacean zooplankton in four of the highly fertilized ponds. Pond water containing phytoplankton was toxic to the dominant Ceriodaphnia reticulata, yet pond phytoplankton isolated from pond water and resuspended in chlorinated tap water supported excellent growth of C. reticulata. Millipore—filtered pond water was not toxic. Analysis of chemical changes occurring in pond water with filtration showed a slight decrease in pH as the only significant alteration that is directly related to zooplankton mortality. The existence of such a pH mortality factor was demonstrated by testing the survivorship of newborn. C. reticulata in artificially adjusted pH treatments. A change from pH 10.8 to 11.2 radically altered the survivorship. Other hypothesis to explain the disappearance of C. reticu...

Development of predictive models for geosmin-related taste and odor in Kansas, USA, drinking water reservoirs

The presence of taste and odor compounds can greatly reduce the quality of drinking water supplies. Because the monetary costs associated with the removal of these compounds can be high, it is impractical for most facilities to continuously treat their raw water. Instead, new tools are needed to help predict when taste and odor events may be most likely to occur. Water quality data were collected between June and October in 2006-2007 from five Kansas (USA) reservoirs in order to develop predictive models for geosmin, a major taste and odor compound; two of these reservoirs were also sampled during specific taste and odor events in December 2006 and January 2007. Lake trophic state alone was not a good predictor of geosmin concentrations as the highest average geosmin concentration was observed in the reservoir with the lowest nutrient and chlorophyll a concentrations. In addition, taste and odor events were not confined to summer months; elevated geosmin concentrations were observed in several reservoirs during the winter. Growth limitation by inorganic phosphorus appeared to be the primary determinant of geosmin production by algal cells in these reservoirs.

Managing Taste and Odor Problems in a Eutrophic Drinking Water Reservoir

ABSTRACT Drinking water for the City of Wichita, KS is provided by Cheney Reservoir, a eutrophic impoundment constructed by the U.S. Bureau of Reclamation in 1962. This large, shallow reservoir has a mean depth of 5.3 meters and a surface area of 40 km2. Numerous reports of undesirable taste and odor in drinking water were received by the City of Wichita Water and Sewer Department in the early 1990s, and periodic episodes of objectionable tastes and odor have occurred up through fall 2001. An intensive limnological sampling program was carried out from August 1999-October 2000, and simultaneous measurements of two taste and odor-causing compounds (geosmin and methylisoborneol) in the lakewater were also performed. These data were used to construct empirical, phosphorus-based water quality management recommendations designed to help reduce the likelihood of objectionable taste and odor events in Cheney Reservoir. The general framework developed here should also be applicable to other waterbodies exhibiting taste and odor-related problems.

PHYSICAL AND CHEMICAL CONDITIONS SURROUNDING THE DIURNAL VERTICAL MIGRATION OF CRYPTOMONAS SPP. (CRYPTOPHYCEAE) IN A SEASONALLY STRATIFIED MIDWESTERN RESERVIOR (USA)

Cross Reservoir, a small mesotrophic reservoir located at the University of Kansas Ecological Reserves (Kansas, USA), contained a dense metalimnetic community of algae and photosynthetic bacteria between early July and late October 1997–1999. Within this community, various Cryptomonas species, primarily C. erosa (Ehrenberg), C. erosa var. reflexa (Marsson), and C. rostratisformis (Skuja), diurnally migrated as indicated by in situ fluorescence monitoring and direct phytoplankton enumeration. The Cryptomonas spp. typically resided near the oxic–anoxic boundary of the water column; however, they actively migrated upward during the day and descended to lower anoxic locations at night, apparently responding to diurnal changes in their local habitat. Their nocturnal environment had moderate levels of sulfide, elevated secondary nutrients, and a community of anoxygenic phototrophic bacteria, whereas their daytime environment had higher light, lower nutrients, and no local photosynthetic bacteria. Monitoring indicated that the Cryptomonas spp. migration was generally linked to daily variations in absolute light intensity (e.g. sunny vs. cloudy days) and the level of other potentially growth‐limiting resources, particularly nitrogen and phosphorus. However, further analyses showed that the primary factor that determined whether the Cryptomonas spp. migrated or not on a given day was the slope of the light gradient immediately above the Cryptomonas spp. peak.

Response of three phytoplankton bioassay techniques in experimental ponds of known limiting nutrient

In a controlled enrichment study of eight experimental ponds, results from the batch bioassay, primary productivity incubation bioassay, and chemostat techniques for measuring limiting factors of phytoplankton algae were compared to the change in the natural system with nutrient addition. In the ponds, rapid and dramatic increase in both phytoplankton biomass and primary productivity upon the addition of nitrogen and phosphorus fertilizer offered conclusive evidence that these nutrients were limiting in the control ponds to which no nutrients were added. Both the batch bioassay and chemostat techniques clearly indicated nitrogen and possibly phosphorus as the limiting factors; however, the primary productivity incubation bioassay technique showed no increase in 14C uptake with addition of these nutrients. A species- and/or nutrient-specific time lag between nutrient uptake and increased carbon fixation is suggested to explain the failure of the technique to yield positive results within the 4-hour incubation period used.

Effects of non-algal turbidity on cyanobacterial biomass in seven turbid Kansas reservoirs

Abstract One of the most visible consequences of eutrophication in freshwater lakes is an increase in the biomass of cyanobacteria. While growth of cyanobacteria has been shown to be coupled to water column concentrations of total phosphorus (TP) in natural lakes, the ecological behavior of cyanobacteria in turbid impoundments is less well understood. Patterns of cyanobacterial biovolume in 7 turbid Kansas (USA) reservoirs exhibited overlap with published data from natural lakes in North America. Non-algal turbidity (NAT) influenced the relationship between cyanobacteria and TP in these systems. Relative to yields predicted from natural lakes, the biomass of cyanobacteria per unit TP was typically higher in the reservoirs, except in those systems that had exceptionally high levels of NAT (>∼2.0 2/m) where observed concentrations were mostly lower than predicted. A more consistent pattern was observed with respect to the effects of NAT on yields of chlorophyll-a per unit TP in the reservoirs: across almost the entire NAT gradient, observed chlorophyll-a concentrations were typically lower than those predicted from natural lakes. Taken together, our results confirm that NAT plays an important role in regulating relationships between TP and phytoplankton biomass in reservoir ecosystems.

An Analysis of the Trophic State of Clinton Lake

ABSTRACT The trophic state of Clinton Lake was assessed. Typical longitudinal gradients were observed with nutrient concentrations (TN, TP, NO3-N, NH4-N, PO4-P) decreasing from the riverine areas of the reservoir to the main basin. The TN:TP ratio went from 6.7 in the riverine zones to 14.2 in the main basin. The reservoir was eutrophic according to all the criteria assessed. Using growing season means for the main basin: chlorophyll a = 16 μg·L−1 > 10 μg·L−1, TP = 39 μg·L−1 >20 μg·L−1, TN = 0.52 mg·L−1 > 0.50 mg·L−1, Secchi disk depth = 1.13m < 2 m. Practices aimed at reducing phosphorus and sediment loadings are suggested to improve water quality.

Effects of Cadmium Stress on the Plankton Communities of Experimental Ponds

Abstract Experimental ponds were used to determine the impact of a single low-level addition of cadmium on naturally occuring plankton communities. Cadmium (as CdCl2) was added to two ponds to create nominal concentrations of 5 μgCd/1 and two ponds served as non-addition controls. Plankton responses were then monitored for 31 days. Cadmium concentrations declined rapidly in treated ponds to < 1 μg/1 by day 10. Biomass and productivity of the phytoplankton community were slightly lower in treated ponds immediately following cadmium addition, but by day 10 had returned to control pond levels. The zooplankton community exhibited a wide range of responses. Simocephalus serrulatus populations were virtually eliminated in treated ponds initially, but later recovered. In situ and laboratory bioassays verified this decreasing effect of cadmium with time. Populations of another cladoceran, Diaphanosoma brachyurum, were enhanced in the cadmium ponds; it appeared earlier and was more abundant on each date sampled. C...