Russell G. Kreis

Checklist of Diatoms from the Laurentian Great Lakes. II

An updated diatom (Bacillariophyta) checklist for the Great Lakes is provided. The present checklist supplants the preliminary checklist published in The Journal for Great Lakes Research in 1978 and effectively represents a 20-year update. A series of procedures were used in this update which included: a reexamination of taxa reported in the 1978 list, additions of taxa reported from the Great Lakes during the past 20 years, and a revision of taxonomy, commensurate with systematic and nomenclatural changes which have occurred primarily during the past 8 years. 1488 diatom species or subordinate taxa are considered to be correct reports from the Great Lakes out of the 2188 diatom entities reported in the list. Of the 124 genera reported 105 are considered to be names in current use. The number of diatom species reported represents a 16.5% increase and the number of genera reported represents a 78% increase over those reported in the 1978 checklist. 13% of the species reported and 32% of the genera reported are due solely to nomenclatural changes. Results indicate that Great Lakes diatoms are a biodiverse component of the ecosystem, commensurate with the wide range of habitats found in the system. The present checklist indicates that most of the newly added species are primarily benthic or periphytic in nature and these represent largely understudied habitats. These results suggest that the present checklist may only represent approximately 70% or less of the extant diatom flora of the Great Lakes system.

Integrated assessment of contaminated sediments in the lower Fox River and Green Bay, Wisconsin.

Samples of sediment and biota were collected from sites in the lower Fox River and southern Green Bay to determine existing or potential impacts of sediment-associated contaminants on different ecosystem components of this Great Lakes area of concern. Evaluation of benthos revealed a relatively depauperate community, particularly at the lower Fox River sites. Sediment pore water and bulk sediments from several lower Fox River sites were toxic to a number of test species including Pimephales promelas, Ceriodaphnia dubia, Hexagenia limbata, Selenastrum capricornutum, and Photobacterium phosphorum. An important component of the observed toxicity appeared to be due to ammonia. Evaluation of three bullhead (Ictalurus) species from the lower Fox River revealed an absence of preneoplastic or neoplastic liver lesions, and the Salmonella typhimurium bioassay indicated relatively little mutagenicity in sediment extracts. Apparent adverse reproductive effects were noted in two species of birds nesting along the lower Fox River and on a confined disposal facility for sediments near the mouth of the river, and there were measurable concentrations of potentially toxic 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), and planar polychlorinated biphenyls (PCBs) both in the birds and in sediments from several of the study sites. Based on toxic equivalency factors and the results of an in vitro bioassay with H4IIE rat hepatoma cells, it appeared that the majority of potential toxicity of the PCB/PCDF/PCDD mixture in biota from the lower Fox River/Green Bay system was due to the planar PCBs. The results of these studies are discussed in terms of an integrated assessment focused on providing data for remedial action planning.

Toxicity of Detroit River Sediment Interstitial Water to the Bacterium Photobacterium Phosphoreum

We used the Photobacterium phosphoreum bacterial luminescence assay (MicrotoxR) to survey the distribution of the toxicity of the sediments from the lower Detroit River during the summer of 1986. Of the 136 locations tested, 25 were classified as very toxic, 60 as moderately toxic, 10 as slightly toxic, and 41 were classified as being non-toxic. The greatest number of very toxic sites was observed on the western shore of the Trenton Channel; however, some very toxic locations were observed throughout the study area. The least toxic areas were observed at the eastern-most locations studied. The MicrotoxR assay has been found to be a sensitive assay, which can be calibrated to the responses of other organisms such as macroinvertebrates and can be related to the potential for distribution of macroinvertebrates in sediments. Therefore, the MicrotoxR assay is useful for rapid screening and mapping of toxicity of sediments.

Sediment pore water toxicity identification in the lower fox river and Green Bay, Wisconsin, using the microtox assay

Microtox assays with two different methods of osmotic adjustment were used to assess the toxicity of pore waters from 13 sediment samples collected from the Fox River watershed in Wisconsin. No toxicity was observed in Microtox assays osmotically adjusted with NaCl; however, 15-min EC50 values for assays osmotically adjusted with sucrose ranged from 52 to 63% pore water. Un-ionized ammonia accounted for a large part of the observed toxicity, but, based on a toxic units approach, did not account for all observed toxicity. Metals (Cu, Zn) and an unidentified compound(s) may potentially contribute to the observed effects in Microtox assays osmotically adjusted with sucrose. The use of alternative osmotic adjustment techniques in the Microtox assay is one potentially useful tool for elucidating several classes of compounds responsible for effects observed in toxicity assays.

Resurrection of the Lake Michigan Eutrophication Model, MICH1

ABSTRACT The Lake Michigan model, MICH1, was developed more than 30 years ago. This framework was evaluated using field data collected in 1976 and was later applied to predict total phosphorus and phytoplankton concentrations in Lake Michigan during the 1980s and early 1990s. With a renewed interest in the interaction of phytoplankton with toxics and the applicability to Total Maximum Daily Load studies, several new models have been developed and older models have been revived. As part of our interest in plankton dynamics in Lake Michigan, the MICH1 model was resurrected. The model was evaluated over the 1976–1995 period, with a surprisingly good model fit to lake-wide average total phosphorus (TP) field data. However, the model was less successful in mimicking the chlorophyll-a measurements, especially in the hypolimnion. Given the results, the model was applied to perform a few long-term TP model simulations. Using the model with average 1994–95 phosphorus loadings, a steady state was reached within approximately 20 years, and the lakewide phosphorus concentration was below the International Joint Commission water quality guideline of 7 μg/L. This exercise demonstrated that a relatively simple, four-segment model was able to mimic the TP lake-wide data well. However, this model was less suitable to predict future chlorophyll-a concentrations due to the limitation in the representation of the foodchain and the difficulty of the coarse segmentation of the model to capture the deep chlorophyll-a layer. Strengths and limitations of this model can guide future development of eutrophication models for Lake Michigan and the other Great Lakes.