Environmental Science & ecology.
Chemical insecticides are pervasively applied to farm fields, gardens, ponds, golf courses, wetlands, streams and roadside ditches for the control of select insect populations. However, the killing mechanism of these chemicals, largely neurotoxins, is not selective, hut can adversely affect the physiology of any animal. As widespread use of chemical insecticides continues, and issues of pesticide runoff, bioaccumulation and ground water contamination are illuminated, there is mounting concern for the effects these chemicals have on humans and complex, natural communities. One alternative to traditional insecticide application is the commercial use of Bacillus thuringiensis israelensis (Bti). Bti is a toxin-producing bacterium naturally found in soil. Upon ingestion, Bti toxin selectively kills specific orders of insects by causing a disruption in the ion balance in the membranes of midgut cells. While Bti has been deemed "nontoxic" for selected fish and mammalian wildlife, studies have not been performed on sensitive amphibian populations or any natural community. This paper presents data showing the direct effects of Bti on frog larvae development and the implications these effects may have on the balance of organisms in aquatic communities. In addition, designs for future mesocosm community studies will be discussed.
Prioritizing Public Open Space Purchases Using Environmental Benefit Scores and Acquisition Costs. Erik E. Nordman and John E. Wagner, Grand Valley State University, Biology Department
Rapid land cover change has prompted public agencies and private land trusts to purchase remaining open spaces. Agencies and land trusts often use non-monetary environmental benefit scores to prioritize the conservation purchases, but the use of acquisition cost data is less common. Economic theory suggests that agencies using both benefit scores and acquisition costs to prioritize their purchases would be able to preserve more environmental benefits than if they used benefit scores alone. This is especially true if properties with high benefit scores are also the most expensive. We hypothesized that the priority ranking of open space purchases by a public agency using only benefit scores would be significantly different from the ranking by an environmental benefit score/acquisition cost ratio. While the results did not show a statistically significant difference between the rankings, we recommend that cost data be included in the decision-making process to ensure that future open space purchases are cost-effective. Though the study area was the Town of Brookhaven, on New York State's Long island, the results also have implications for Michigan's open space preservation programs.
Survival of Stocked Brown Trout (Salmo trutta) in the Pigeon River, Ottawa County, Michigan. Daniel W Mays, Neil W. MacDonald, Grand Valley State University, Department of Biology; Amy Harrington, Michigan Department of Natural Resources, Fisheries Division, and Carl R. Ruetz, Grand Valley State University, Annis Water Resources Institute
Degraded water quality in the Pigeon River during the 1980s resulted in the loss of its trout population. In the mid-1990s, reductions in point and non-point source pollution improved water quality, and the Michigan Department of Natural Resources reinstituted trout stocking in 2005. To evaluate the success of stocking, we conducted fish, habitat, and water quality surveys in the designated coldwater stretch of the Pigeon River. We established nine 1000-ft survey stations, and sampled their fish communities in mid-June, mid-August, and mid-fall, 2006. Water quality, habitat, and the forage base of small fish were generally suitable to sustain a stocked brown trout population in the Pigeon River. Several age classes of brown trout were present in the majority of stream stretches, but only in low numbers, suggesting low survival, high emigration, or a combination of both. Gilchrist Creek-strain trout surviving from initial stockings in 2003 and 2004 had attained lengths of between 15 and 18 inches, suggesting that continued stocking with this strain of brown trout may be warranted. Continued efforts to improve water quality, reduce high storm flows, maintain adequate summer base flows, and provide spawning areas also are needed to improve conditions for trout survival in the Pigeon River.
Histological Examination of Spermatogenesis in the Freshwater Mussel Venustaconcha ellipsiformis (Bivalvia: Unionidae). J. M. Watson, R. J. Trdan, S. P. Shepardson, Saginaw Valley State University, Department of Biology, and W. R. Hoeh, Kent State University, Department of Biological Sciences
Freshwater mussels in the superfamily Unionoidea display two interesting characteristics with respect to sperm formation. First, the formation, of large accumulations of mature sperm embedded in a spherical matrix (~40-60 microns in diameter) has been reported in a number of species. These motile "sperm balls" have been designated spermatozeugmata. Second, spermatogenesis may occur in two separate and distinct ways depending upon the time of year. In atypical spermatogenesis, sperm develop from small clusters of cells (i.e., sperm morulae floating free in the lumen of the acinus of the testis). Typical spermatogenesis occurs in the wall of the acinus. Venustaconcha ellipsiformis, a dioecious species, were collected at least monthly between January 2006 and October 2006. Data analysis demonstrated that free floating sperm morulae (~4-32 cells) were found in the lumen of she acinus throughout most of the dimpling period alongside small numbers of active spermatozoa probably derived from these morulae. However, between mid June and mid July the number of morulae steadily decreased. By mid July, morulae were almost non-existent. Concurrently, the number of free active spermatozoa showed a steady increase and maximized by mid July.
The Potential Habitat Fragmentation Caused by White-Tailed Deer (Odocoileus viginianus) and its Impact on Nest Predation. Benjamin Heys and Robert Keys, Cornerstone University, Science Department
Migratory songbird populations have been declining. Habitat loss and fragmentation are two possible reasons for the declines. This study proposes the heavily used trails of white-tailed deer may be a potential cause of habitat" fragmentation. The purpose of this study was to determine whether fragmentation caused by heavily used deer trails has an impact on nest predation. We hypothesized that nests located closer to well-traveled deer trails would be depredated more often than those a greater distance from the trail. Two types of artificial bird nests simulating the black and white warbler and ruffed grouse were placed at different distances from heavily used deer trails. The nests located further from the deer trails were depredated significantly less often than nests closer to the trails. Warbler nests were depredated more often than grouse nests. Deer mils closer to edges had higher depredation rates than trails farther from edges. The results and photographic evidence collected at the artificial nest sites suggest that predators of ground nesting birds may be employing deer trails to access the forest interior to prey upon bird nests.
Population Genetics of the Mecoptera of Saginaw County, Michigan. Jennifer Privette and David J. Stanton., Saginaw Valley State University, Department of Biology
The order Mecoptera contains the scorpionflies (genus Panorpa) and hangingflies (genus Bittacus). Field studies have identified two populations of the hangingfly B. stigma terns in Saginaw County, which has nor been previously reported in distributional records. Two populations of B. strigosus and two populations of scorpionflies (P. debilis) were also discovered. These populations are small and isolated, occupying relatively undisturbed moist forest under story habitats separated by large tracts of unsuitable intervening habitat. In order to assess the genetic impact of drift and inbreeding in these populations, specimens from these three species were assayed for allozyme variation. Sex ratios were found to be significantly female biased in all populations studied. Average heterozygosity values varied widely and some populations were found to display significant deviation from Hardy Weinberg Equilibrium. Genetic distances between populations and F ST values also varied widely, indicating substantial population substructure and inbreeding in some populations. The results demonstrate the dramatic effect of genetic drift and inbreeding in isolated populations of Mecoptera in Saginaw County. The results also have broader implications for conservation efforts in small isolated populations.
Population Genetics of Great Lakes Zebra Mussels (Dreissena polymorphs). Michael Barber and David. J. Stanton, Saginaw Valley State University, Department of Biology
Zebra mussels are an invasive species introduced into the Great Lakes from Europe in 1986. Since then, they have spread aggressively throughout the eastern United States and have had a significant impact on Great Lakes ecology and biodiversity. Cellulose acetate gel electrophoresis was used in order to score genetic markers for samples taken from Great Lakes locations over the past four years. Sampling sites included the Great Lakes, inland lakes and rivers. Genotypes were scored for 48 individuals per population, and allele frequencies and genotype frequencies were determined. Genetic variation was generally high; however, diversity was generally lower in river than in lake populations. Average heterozygosity values were also generally high and most populations were found to be in Hardy-Weinberg equilibrium. Genetic distances between populations were generally low and there was no correlation between genetic distance and geographic distance. Population substructure and inbreeding was also generally low throughout the Great Lakes region. We are currently developing an independent data set using RAPD markers that will allow us to confirm and extend our findings.
Rotifers in the Grand River, Michigan. G. M. Ross, Kissing Rock Farm, Lowell, Michigan
Lotic plankton were sampled on seventeen dates during 2001-02 from two stations on the lower Grand River using a six inch plankton net at or a few centimeters below the surface. Microscopic analysis was by Palmer Cell. In this downstream community, rotifers were very nearly all the animals observed, a result that differs from earlier Midwestern workers, but not dramatically so. As expected, Keratella spp. were most heavily represented. Polyarthra spp. were ubiquitous, while Synchaeta spp. were the next most numerous. Genera Conochilus and Kellicottia were also present in significant numbers. Genus Brachionis was not observed. The Flat Rivet, a large slow moving tributary, had no discernible impact on the generic mixture. Twenty genera of rotifers were in common with those of a large study of lakes in northern Michigan thirty years ago. The absence of large zooplankton may be in accord with the hypothesis that smaller forms enjoy rapid reproduction times advantageous in moving waters, whilst the larger are eliminated by planktiverous fish.
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|Date:||Jan 1, 2008|
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