David S. White

Distribution of Oligochaetes in Lake Michigan and Comments on Their use as Indices of Pollution

Benthic samples were taken from 286 stations covering all areas of Lake Michigan in 1975 as part of a sedimentological survey of the Great Lakes. From these samples a total of twenty-seven oligochaete species were identified. Stylodrilus heringianus was the most abundant species in the lake and densities were inversely related to organic content of the sediments. Tubificids exhibited localized concentrations in Green Bay and in the northern and southern basins. Comparison of several methods using oligochaete data to assess water quality showed similar patterns, indicating that Southern Green Bay and parts of the southern and northern basins of the lake are organically enriched environments. With the exception of the northern basin, which had not previously been surveyed, these conclusions are consistent with earlier regional oligochaete surveys of the lake. The northern basin of Lake Michigan warrants further study to generate and test hypotheses concerning tubificid species distributions observed there.

Ecology of Shallow and Deep Water Populations of Pontoporeia hoyi (Smith) (Amphipoda) in Lake Michigan

Aspects of the ecology of Pontoporeia hoyi (Smith) were studied at a 15-m and a 42-m deep site along the southeastern shoreline of Lake Michigan. At these shallow and deep sites, respectively, average densities were 3234 and 8292/m2, average annual biomasses were 0.90 and 5.58 g/m2, annual productions were 2.82 and 7.07 g/m2/year, and P/B ratios were 3.13 and 1.27. Mean number of eggs per female at 42 m was 17 with a mean weight per egg of 0.0340 mg, and there was a significant correlation between number of eggs and body length. The life cycle of the 15-m portion of the populations was one year while the 42-m portion was two years. At 42 m the major winter reproductive peak contributes an apparently low density to annual recruitment compared with the minor summer reproductive peak. In part, differences may reflect active onshors migration by winter reproductive adults as nearshore waters cool in early winter. Adults remain onshore and release young in early spring, either dying or moving offshore with rising water temperatures. Young remain onshore as evidenced by very predictable onshore population changes.

Short term lethality and sediment avoidance assays with endrin-contaminated sediment and two oligochaetes from lake Michigan

Mean 96-hr LC50 values and standard deviations for the oligochaetesS. heringianus andL. hoffmeisteri exposed to endrin-contaminated sediment were 2,588±1,974 μg/g dry weight sediment for 4 assays and 2,725±955 μg/g for 2 assays, respectively. Mixed species testing data suggested that the toxicity toL. hoffmeisteri was reduced in the presence ofS. heringianus, yet further testing is required. Ninety-six hour EC50 burrowing avoidance values for both species (19 and 15.3 μg/g forS. heringianus and 59 μg/g forL. hoffmeisteri) were approximately 46 and 150 times lower than their respective mean 96-hr LC50 values. Both S.heringianus andL. hoffmeisteri initially burrowed in contaminated sediment and then returned to the surface in numbers somewhat proportional to the sediment concentration and the length of exposure. Future use of oligochaete behavioral responses to subiethal sediment contamination for pollutant impact on benthic communities is promising.

Sublethal responses to endrin in sediment by Limnodrilus hoffmeisteri (Tubificidae), and in mixed-culture with Stylodrilus heringianus (Lumbriculidae)

Abstract Sediment reworking by Limnodrilus hoffmeisteri (Tubificidae) alone, and with Stylodrilus heringianus (Lumbriculidae) were measured in sediments dosed with endrin by monitoring the burial of a 137 cesium marker layer. Endrin concentrations ranged from 16.1 to 81 400 ng/g dry sediment weight. Alterations in reworking rates were observed at sediment concentrations two to five orders of magnitude below LC 50 values. In single species experiments with L. hoffmeisteri at low endrin concentrations, marker layer burial rate data did not suggest stimulation of reworking, as had previously been found for S. heringianus . At higher concentrations, reworking rates were equal to or slower than control rates early in experiments, followed by dramatic decreases thereafter. Reworking rates with mixed species (1:1 species ratio) suggested that the presence of S. heringianus enhanced the reworking response of L. hoffmeisteri . Post-experimental worm dry weights were inversely related to high sediment concentrations for both species. Reductions in post-experimental L. hoffmeisteri mortalities and increases in L. hoffmeisteri dry weights in mixed species tests at high endrin concentrations implied that L. hoffmeisteri benefits from the presence of S. heringianus , although the reverse was not observed. High final sediment endrin concentrations in the upper three cm implied worm mediated upward contaminant transport. Bioaccumulation factors for S. heringianus ranged from 9.7 to 43.8 and were consistently three to four times greater than bioaccumulation factors for L. hoffmeisteri (1.7 to 13.6).

HUMMOCKING BY LOTIC CHARA: OBSERVATIONS ON ALTERATIONS OF HYPORHEIC TEMPERATURE PATTERNS

Hendricks, S.P. and White, D.S., 1988. Hummocking by lotic Chara: observations on alterations of hyporheic temperature patterns. Aquat. Bot., 31:13-22 Stream-bed temperature profiles were used to examine hyporheic water patterns beneath Chara hummocks in a northern Michigan (U.S.A.) stream. Hummocks were found to alter expected hyporheic temperature patterns significantly, causing apparent upwellings of deeper, colder waters into the hummock. The magnitude of temperature pattern alterations was proportional to the size of the hummock, and hummocks were often situated in areas of the stream where cooler hyporheic water was closest to the stream-bed surface. Upwelling and downwelling patterns caused by hummocks conformed to the literature on hyporheic flow alterations imposed by inanimate objects on the stream-bed surface. Hyporheic water upwellings may be of benefit to Chara by exposing the anchorage system to higher nutrient or ion levels existing in interstitial water.

Sublethal responses to endrin in sediment by Stylodrilus heringianus (Lumbriculidae) as measured by a 137cesium marker layer technique

Abstract Sediment reworking rates of Stylodrilus heringianus (Oligochaeta: Lumbriculidae) were measured in microcosms containing sediments dosed with the chlorinated pesticide, endrin. Reworking rates were measured at 10°C by monitoring a 137cesium marker layer burial in contaminated and uncontaminated microcosms. Endrin concentrations ranged from 3.1 to 42 000 ng/g dry sediment. Alterations in reworking rates were observed at sediment concentrations five and one half orders of magnitude below the LC50 (1 650 μg/g). For the lower concentrations, marker layer burial rate data suggested possible stimulatory effects in the first 300 to 600 h, followed by significant rate decreases relative to controls. For higher concentrations, rates were equal to or slower than control rates in the first 600 h, followed by dramatic decreases in the last 600 h. High final surficial sediment endrin concentrations at the end of experiments implied worm mediated upward transport. Worm mortalities were 9.3 to 28% for the two highest concentrations (42 000 and 11 500 ng/g) and 0 to 6.7% for all other concentrations including controls. Post experimental worm dry weights were inversely related to high concentrations. Bioaccumulation factors ranged from 34 to 67 on a g dry organism to g dry sediment basis.

Interstitial water patterns: A factor influencing the distributions of some lotic aquatic vascular macrophytes

Fortner, S.L. and White, D.S., 1988. Interstitial water patterns: a factor influencing the distributions of some lotic aquatic vascular macrophytes. Aquat. Bot., 31: 1-12. The distributions of 9 species of aquatic vascular macrophytes were examined in relation to interstitial water patterns (based on temperature) in the beds of three northern Michigan (U.S.A.) streams. Ranunculus septentrionalis Poir., Caltha palustris L. and Nasturtium officinale R.Br. were associated with areas of groundwater discharge. Sparganium chlorocarpum Rydb., Veronica catenata Penn., Potamogeton fili/ormis Pers. and P. richardsonii (Benn.) Rydb. occurred most often at the downstream end of a hyporheic zone (corresponding to the foot of a riffle) where interstitial water was of surface origin. Sagittaria lati[olia Willd. occurred where interstitial temperatures were cool; the water origin was not determined. Potamogeton gramineus L. occurred most often where interstitial temperatures were warm, primarily at the upstream ends and middles of hyporheic zones (heads of riffles) in areas of surface-water infiltration. Complex patterns of interstitial water movement and related physicochemical complexity combined with differences in plant requirements, in part, may determine observed local distributions.

Burrowing avoidance assays of contaminated Detroit River sediments, using the freshwater Oligochaete Stylodrilus heringianus (Lumbriculidae)

The burrowing behavior ofStylodrilus heringianus (Lumbriculidae, Oligochaeta) was examined in bioassays, using sediments from suspected areas of contamination in the Detroit River, Michigan (U.S.A.). In assays with control sediments and sediments from a clean Detroit River site, all worms quickly burrowed (<1 hr) and appeared to feed normally over a 96-hr period. In sediments with suspected sediment-bound contaminants,Stylodrilus initially burrowed but returned to the surface after a few hours, the time of return apparently dependent on the degree of contamination and length of exposure. The presence of volatile contaminants reduced the initial burrowing response. These observations enhance the possibility of using aStylodrilus burrowing behavior assay to aid in examining suspected areas of sediment contamination in the Great Lakes.

Effects of Temperature and Density on Sediment Reworking by Stylodrilus Heringianus (Oligochaeta: Lumbriculidae)

A non-destructive, radio-marker system was used to follow sediment burial, or reworking rate, by the particle-feeding oligochaete Stylodrilus heringianus Claparede over a range of worm densities and water temperatures in laboratory microcosms. Marker layer burial rates were monitored for seven densities (30,000 to 134,000 worms m−2) while slowly altering the temperature from 10°C down to 4°C, up to 20°C, and then back to 10°C. From 10°C to 4°C, reworking rates decreased approximately 90%. When the temperature was increased above 4°C, reworking rates approached levels shown at the initial 10°C but remained relatively constant through the remainder of the experiment. It is assumed that reproductive activities, stimulated by the 4° C period, affected feeding activity. The reworking rate per worm was shown to be independent of the initial oligochaete density. Time dependent and depth dependent models were tested to examine the decline in observed reworking rates during the latter part of the experiment. There was a weak correlation between time and decreased reworking rates and a strong correlation between density and depth of feeding. Correlations suggested that reworking rates per worm remained similar over time, but the depth to which an organism fed increased with increasing worm density.

Trophic Status of Southeastern Lake Michigan Based on the Chironomidae (Diptera)

Abstract Chironomids and oligochaetes were identified from a total of 2,432 samples collected at depths 1.50 (Type 2). A trophic index based on the chironomid fauna was generated for year, depth intervals, and combinations of years and depths. When averaged over all years, the trophic index at the 8- to 24-m depth interval was 1.26, indicating mesotrophic conditions in this portion of the littoral and sublittoral of southeastern Lake Michigan. Similarly, at depths >28 m the trophic index value was 0.41, suggesting oligotrophic conditions in the profundal. No annual trophic status trends were evident.