Geology topics

Jody A. Kubitz

Publications and source records attributed to Jody A. Kubitz.

4 recordsLinked to original sources

USGS2025

Responses of larval fish and zooplankton to whole-lake 2,4-D herbicide treatments used to control Eurasian watermilfoil in northern Wisconsin lakes

In North America, Eurasian watermilfoil Myriophyllum spicatum is one of the most widespread non-native aquatic plant species in freshwater ecosystems. Applications of 2,4-dichlorophenoxyacetic acid (2,4-D) herbicides are often utilized to control Eurasian watermilfoil. Herbicide applications may have unintended effects on non-target organisms like zooplankton and fish, but these effects are poorly understood. Our objectives were to determine if whole-lake 2,4-D herbicide treatments (epilimnetic target rate = 0.3 ppm) used to control Eurasian watermilfoil affected (1) density, diversity, and size of zooplankton and (2) density, diversity, and growth of larval fishes in three northern Wisconsin lakes when compared to trends observed in three untreated reference lakes. Average peak concentrations of 2,4-D following applications ranged from 0.152 to 0.257 ppm. We found no statistically significant evidence that the applications influenced the zooplankton and larval fish metrics we examined, but subtle responses to the herbicides may not have been detected given the inherent variation in our response metrics. Additional replication and research are needed to assess responses to higher concentrations and repeated applications over time and to document responses across a broader range of lake types and fish communities.

Wisconsin↗

USGS1996

A two-step experimental design for a sediment bioassay using growth of the amphipod Hyalella azteca for the test end point

We designed a sediment bioassay using 25% growth inhibition of Hyalella azteca as the end point. Hyalella azteca exhibits size-specific fecundity, so growth is a surrogate of reproductive production. We investigated density effects on growth to address whether crowding could affect test interpretation; amphipods in 14,000/m 2 exposures were 16 to 20% smaller than those at 7,000/m 2 . Using power analysis, we found that 20 to 25 samples are required to determine significance when α = 0.10 and 1 − β = 0.90. To minimize the need for laboratory resources, we designed a two-step (screening and confirmatory) bioassay, which we tested with field-collected sediments. The screening bioassay compared 11 sediments to a reference. Three sediments were “toxic” (significant growth inhibition when 1 − β = 0.66 and n = 5), five sediments were “nontoxic” (>90% of reference), and three sediments were “possibly toxic” (growth inhibition was insignificant). In the confirmatory bioassay, three possibly toxic and two nontoxic samples were reevaluated. Two were toxic (1 − β = 0.91 and n = 20), and the remaining four samples were nontoxic. In summary, five sediments were toxic and six sediments were nontoxic. The two-step analysis used minimal laboratory resources but maximized statistical power, where needed, to discriminate growth effects.

Environmental Toxicology and Chemistry↗

USGS1996

Assessment of sediment quality in dredged and undredged areas of the Trenton Channel of the Detroit River, Michigan USA, using the sediment quality triad

The “sediment quality triad” approach was used to assess the effects of dredging on the sediment quality of a new marina in the Trenton Channel of the Detroit River, and to evaluate spatial and temporal variation in sediment quality in the Trenton Channel. Samples were collected in November of 1993 (10 months after dredging) and characterized by chemical analysis, sediment bioassays, and assessment of benthic invertebrate communities. The three study components indicated little difference in sediment quality at dredged sites in the marina relative to nearby areas in the Trenton Channel, and little change in sediment quality of Trenton Channel sites relative to conditions reported in the mid-1980s. These results suggest that improvement in sediment quality in the Trenton Channel, due to dredging or natural processes, will depend on elimination of sediment “hot spots” and other upstream contaminant sources. Concentrations of chemical contaminants, especially metals and polycyclic aromatic hydrocarbons, exceeded concentrations associated with effects on biota and were significantly correlated with results of sediment bioassays and characteristics of benthic communities. Laboratory sediment bioassays with Hyalella azteca and Chironomus tentans produced better discrimination among sites with differing degrees of contamination than did characterization of benthic communities, which were dominated by oligochaetes at all sites in the marina and the Trenton Channel.

Journal of Great Lakes Research↗

USGS1995

Influences on copper bioaccumulation, growth, and survival of the midge, Chironomus tentans, in metal-contaminated sediments

Sediment bioassays with larvae of the midge, Chironomus tentans , were used to evaluate influences on the bioavailability and toxicity of copper (Cu) in sediments with a wide range of concentrations of metals, acid-volatile sulfide (AVS), and other physicochemical characteristics. Sediments were collected from sixteen lakes in Michigan, USA, and from twelve sites in the Clark Fork River drainage of Montana, USA, which are contaminated with metals from mining activities and from other anthropogenic sources. Bioassays with C. tentans larvae were conducted for ten days in a static-renewal test system, with endpoints of survival, growth, and metal bioaccumulation. Bioaccumulation of copper (Cu) was strongly correlated with Cu concentrations in porewater, and was increased significantly at Cu concentrations less than those affecting growth or survival. Midge survival and growth were not significantly correlated with concentrations of Cu in sediment or porewater, and were poorly predicted by ratios of acid-extractable metals to AVS in sediments. Principal components analysis indicated that Cu concentrations in porewater and bioaccumulation of Cu by midge larvae were influenced by AVS, sediment organic carbon, and porewater pH, and that toxicity was associated with high concentrations of Cu, high concentrations of zinc (Zn) and ammonia. No toxicity was observed in several sediments which contained low concentrations of AVS and high concentrations of Cu and Zn. In sediments which contain little AVS, bioavailability of metals may be controlled by constituents other than sulfides, such as organic matter and metal hydrous oxides. These results indicate that assessments of toxicity in metal-contaminated sediments should evaluate the importance of metal-binding phases other than sulfides, and the possible contributions of ammonia or other toxicants to toxicity in sediment bioassays.

Michigan, Montana↗