Donald G. Huggins

Thresholds in macroinvertebrate biodiversity and stoichiometry across water-quality gradients in Central Plains (USA) streams

Abstract N and P often limit primary and secondary production in ecosystems, but they also can cause eutrophication and negatively influence sensitive species above a certain level or threshold point. Aquatic biodiversity can have negative threshold relationships with water-quality variables at large scales, but the specific mechanism(s) driving these threshold relationships are not well established. We hypothesized that resource quality (i.e., C:P) might partly drive primary consumer (grazer and detritivore) richness thresholds by altering competitive interactions among species with differing resource demands, but might have less influence on predator richness. We estimated total N (TN), total P (TP), and turbidity thresholds for macroinvertebrate richness across trophic levels and feeding groups in Central Plains (USA) streams. We also determined if mean taxon body C:P of groups with diversity losses were negatively related to TP, a pattern that would suggest that eutrophic communities were dominated by a few species with high dietary P demands. Primary consumers were more sensitive to TN and TP (threshold mean  =  1.0 mg N/L and 0.06 mg P/L) than secondary consumers (threshold mean  =  0.09 mg P/L), a result supporting the resource quality hypothesis. Turbidity reduced richness regardless of feeding mode (threshold mean  =  4.7 NTU), a result suggesting that turbidity and nutrient thresholds were driven by different factors. The TP-richness threshold could be driven partially by changes in food quality because the mean body C:P of shredding and collector-gathering taxa declined as TP increased (threshold mean  =  0.07 and 0.75 mg P/L, respectively). Mean scraper C:P was not related to TP, a result indicating other factors might be responsible for the scraper richness threshold. Our results suggest that changes in resource quality could contribute to large-scale losses in biodiversity in nutrient-enriched lotic ecosystems. Within shredder and collector-gatherer macroinvertebrate feeding groups, P-rich food might allow faster growing taxa with high body P demands to out-compete slower growing taxa adapted to lower quality food resources. This pattern suggests that biotic integrity is directly linked to nutrients in streams and that toxicity, low dissolved O2, and increased turbidity might not be the only mechanisms leading to reductions in diversity as nutrient concentrations increase.

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.

Current status of native fish species in Kansas

Abstract A re-evaluation of the status of fishes in Kansas suggests that 54 of the 116 native species should be assigned special conservation status due to substantial declines in distribution or abundance and/or their rarity in the state. Nine species are recommended for retention in their existing status of endangered, threatened, or species in need of conservation. We recommend elevated conservation status for 44 additional species, and provide information on trends in distribution and abundance for these taxa. A single species, the Arkansas River Shiner, Notropis girardi, is considered to be extirpated recently from Kansas.

Relationships between cyanobacterial production and the physical and chemical properties of a Midwestern Reservoir, USA

Drinking water reservoirs in agricultural dominated watersheds are particularly vulnerable to cyanobacterial blooms. A major byproduct of cyanobacteria is the production of objectionable taste and odor compounds such as geosmin. During May 1997 to September 1998, we studied spatial and temporal patterns of cyanobacterial abundance and composition with respect to a series of physical and chemical properties in Clinton Lake, located in east central Kansas, USA. Our results suggest that nutrients (in particular TN, NO3‘–N concentrations), turbidity, and hydrologic regime all played potentially important roles in regulating cyanobacterial production. Specifically, low levels of nitrogen coupled with the internal release of phosphorus from the lake sediment under brief periods of anoxia may have helped promote cyanobacterial blooms. There was also a strong association between cyanobacterial blooms, geosmin production, and most taste and odor events in Clinton Lake. Anabaena circinalis appeared to be the source for geosmin production as a result of senescing algal cells just after the primary die-off of cyanobacteria.

Effects of sediment resuspension on nutrient concentrations and algal biomass in reservoirs of the Central Plains

Abstract Historically, lake and reservoir management has focused on controlling external nutrient loading. However, it is becoming increasingly clear that internal mechanisms, such as the episodic resuspension of benthic sediments, can also contribute to the processes of eutrophication. We conducted laboratory bioassay experiments to determine how resuspended sediments affected nutrient concentrations and algal biomass in four eutrophic reservoirs of the Central Plains. Surficial sediments and surface water were collected from each reservoir and returned to the laboratory where they were added to 1-L bioassay bottles at five turbidity concentrations (0, 50, 150, 250, and 500 NTUs). Sediments in the bioassay bottles were resuspended daily, and algal biomass (measured as relative fluorescence) was measured for 11–14 days. Resuspended sediments at the lowest experimental turbidity concentration, 50 NTUs, had highly significant effects on algal biomass in each of the sediment resuspension bioassays. Algal biomass appeared to increase following experimental sediment resuspension due to an increase in available nutrients and/or the establishment of algae (meroplankton) from the sediment. Overall, our results highlight the importance of considering internal mechanisms when developing reservoir management and restoration plans for these important 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.

Development of water quality criteria for ammonia and total residual chlorine for the protection of aquatic life in two Johnson County, Kansas, streams

A study was conducted to determine water quality criteria for ammonia and total residual chlorine (TRC) for the protection of aquatic life in two streams in Johnson County, Kan. The test streams selected were Mill and Cedar Creeks. The parallel streams flow into the Kansas River and share similar watershed characteristics. However, unlike Mill Creek, Cedar Creek does not receive sewage treatment plant effluents. Species indigenous to the streams were collected, and 96-h acute toxicity tests were conducted with ammonia and TRC. Following the laboratory work, a test was conducted in Cedar Creek whereby ammonia was introduced for 24-h. Test organisms were placed in cages in the stream, and mortalities were observed throughout the test period Based on this research and other existing evidence, the conclusion was reached that if un-ionized ammonia concentrations in the two streams do not exceed 0.07 mg/litre un-ionized ammonia expressed as nitrogen (NH 3 -N) as a 24-h average, or 0.4 mg/litre NH 3 -N at any time, aquatic life in the two streams will suffer no adverse effects. Nor will these organisms be adversely affected by total residual chlorine concentrations that do not exceed 0.02 mg/litre TRC as a 24-h average. or 0.03 mg/litre TRC at any time.

Sediment Contamination of Residential Streams in the Metropolitan Kansas City Area, USA: Part II. Whole-Sediment Toxicity to the Amphipod Hyalella azteca

This is the second part of a study that evaluates the influence of nonpoint sources on the sediment quality of five adjacent streams within the metropolitan Kansas City area, central United States. Physical, chemical, and toxicity data (Hyalella azteca 28-day whole-sediment toxicity test) for 29 samples collected in 2003 were used for this evaluation, and the potential causes for the toxic effects were explored. The sediments exhibited a low to moderate toxicity, with five samples identified as toxic to H. azteca. Metals did not likely cause the toxicity based on low concentrations of metals in the pore water and elevated concentrations of acid volatile sulfide in the sediments. Although individual polycyclic aromatic hydrocarbons (PAHs) frequently exceeded effect-based sediment quality guidelines [probable effect concentrations (PECs)], only four of the samples had a PEC quotient (PEC-Q) for total PAHs over 1.0 and only one of these four samples was identified as toxic. For the mean PEC-Q for organochlorine compounds (chlordane, dieldrin, sum DDEs), 4 of the 12 samples with a mean PEC-Q above 1.0 were toxic and 4 of the 8 samples with a mean PEC-Q above 3.0 were toxic. Additionally, four of eight samples were toxic, with a mean PEC-Q above 1.0 based on metals, PAHs, polychlorinated biphenyls (PCBs), and organochlorine pesticides. The increase in the incidence of toxicity with the increase in the mean PEC-Q based on organochlorine pesticides or based on metals, PAHs, PCBs, and organochlorine pesticides suggests that organochlorine pesticides might have contributed to the observed toxicity and that the use of a mean PEC-Q, rather than PEC-Qs for individual compounds, might be more informative in predicting toxic effects. Our study shows that stream sediments subject to predominant nonpoint sources contamination can be toxic and that many factors, including analysis of a full suite of PAHs and pesticides of both past and present urban applications and the origins of these organic compounds, are important to identify the causes of toxicity.

Effects of a Large Kansas Reservoir on Downstream Groundwater Quality

ABSTRACT Several water quality parameters, including inorganic nitrogens and phosphorus, were measured in groundwater from the Republican River aquifer above and below Milford Reservoir, Kansas. Ammonia and total phosphorus concentrations were considerably higher (>50%) in groundwater from the pressure relief wells along the toe of Milford Reservoir dam than from well water sampled upstream of the lake. However, the concentration of these compounds decreased to near upstream levels within 1.2 km downstream of the dam. Within the array of pressure relief wells, the concentration of ammonia was greatest in water from wells near the center of the dam. Conductivity, hardness, and alkalinity were lower, and pH was higher, in groundwater below Milford Reservoir than above it. The ratio of ammonia to total inorganic nitrogen in elutriates from Milford Reservoir sediments and water from the pressure relief wells was similar. These results suggest that water seeping out of reservoirs into underlying alluvial aquif...