Mark R. Luttenton

Population Dynamics of Mysis relicta in Southeastern Lake Michigan, 1995–1998

The abundance and life history characteristics of Mysis relicta were evaluated at an offshore (110-m) and a nearshore (40 to 45-m) station during 1995, 1996, and 1998. Data were collected to monitor mysids relative to ongoing ecological changes in Lake Michigan and as a comparison to studies from the 1970s and 1980s. Mean densities of M. relicta during May through September each year were higher offshore (210/m2 to 373/m2) compared to nearshore (41/m2 to 168/m2). Growth rates ranged between 0.026 to 0.041 mm/day and did not differ between stations or with age. Juvenile mysids (< 10 mm) dominated the population, and accounted for 30 to 90% of the catch. The size distribution of M. relicta suggested that reproduction occurred year-round with the most consistent influxes of juveniles in the spring (April through June) each year; winter (February and March) and summer (July through September) influxes of juveniles did not occur consistently each year. Mean length of females with broods differed between nearshore (14 mm) and offshore (16 mm). Brood size and the proportion of females with broods did not differ between stations. Abundance estimates were equal or higher and life history characteristics were similar to reported data from the 1970s and 1980s. However, ongoing declines in the benthic macroinvertebrate Diporeia may result in higher fish predation pressure on M. relicta in the near future.

An environmental assessment of an impacted, urbanized watershed: the Mona Lake Watershed, Michigan

The ecological health and integrity of watersheds throughout the world are being threatened by a variety of stressors. Often, restoration practices focus on single problems whereas comprehensive, multidisciplinary approaches are needed to address both the symptoms and underlying causes of impairment. A comprehensive assess- ment of a small, urbanized watershed in west Michigan, USA was conducted to evalu- ate the major stressors in the system. This assessment approach for the Mona Lake wa- tershed included analyses of land use/land cover change, water quality in both the major surface inflows and the receiving water body, and toxic inputs into a major in- flow. Because these issues are common to many watersheds, we developed a concep- tual model that spatially links these stressors and predicted impacts, allowing us to as- sess them in a comprehensive manner. Based on our results, we generated a set of re- commendations targeted for specific source or problem areas. This approach can be applied to other watersheds.

Effects of Three Orconectes Crayfishes On Epilithic Microalgae: a Laboratory Experiment

[We tested the implications of littoral zone food web changes for periphyton abundance by comparing algal removal rates of three Orconectes crayfishes and a grazing snail (Amnicola sp. or spp.) in a laboratory experiment. Periphyton communities were established on unglazed clay tiles incubated in grazer free enclosures in the littoral zone of Carrol Lake, Wisconsin. In the laboratory, tiles were placed in individual arenas that were randomly assigned to one of four grazing treatments or a control treatment. After 96 h, total algal biovolume was reduced except by O. rusticus. However, when algal removal rates were expressed as per unit shell-free dry weight, Amnicola removal rates were at least 17 × higher than that of any crayfish. These data are consistent with previous field observations that show snails remove (primarily grazing) periphyton more efficiently than crayfish. Combined with previous work on crayfish predation on snails, our results suggest that crayfishes have a strong indirect positive effect on periphyton by reducing snail abundances, whereas the direct effects due to crayfish grazing are minimal., We tested the implications of littoral zone food web changes for periphyton abundance by comparing algal removal rates of three Orconectes crayfishes and a grazing snail (Amnicola sp. or spp.) in a laboratory experiment. Periphyton communities were established on unglazed clay tiles incubated in grazer free enclosures in the littoral zone of Carrol Lake, Wisconsin. In the laboratory, tiles were placed in individual arenas that were randomly assigned to one of four grazing treatments or a control treatment. After 96 h, total algal biovolume was reduced except by O. rusticus. However, when algal removal rates were expressed as per unit shell-free dry weight, Amnicola removal rates were at least 17 × higher than that of any crayfish. These data are consistent with previous field observations that show snails remove (primarily grazing) periphyton more efficiently than crayfish. Combined with previous work on crayfish predation on snails, our results suggest that crayfishes have a strong indirect positive effect on periphyton by reducing snail abundances, whereas the direct effects due to crayfish grazing are minimal.]

Response of a lentic periphyton community to nutrient enrichment at low N:P ratios

We examined the effect of nitrogen:phosphorus (N:P) ratios and nutrient concentrations on periphyton when nutrients (N and P) are provided in excess. A gradient of seven N:P ratios ranging from 7.5:1 to 1:7.5 and each at three absolute concentrations, was established using nutrient‐releasing substrata placed in a meso‐oligotrophic lake. Differences in total algal biovolume among nutrient ratios were significant (analysis of covariance [ANCOVA]) when P concentration was entered as the co‐variate. In addition, total algal biovolume was significantly correlated with N concentration but not P. To further evaluate the relationship between nutrient ratios and biovolume, we analyzed (using four 1‐way analysis of variances [ANOVAs]) four subsets of data defined as a series of treatments where one nutrient concentration remained relatively constant as the other changed creating different N:P ratios. Ratios of data subsets ranged from 1:1 to 7.5:1 and 1:1 to 1:7.5 with low and high concentrations of both series. Only diatom biovolume varied with ratio but these differences are most likely related to increased green algal abundance. Species richness and diversity differed among N:P ratios (ANCOVA) when P concentration was used as the co‐variate. Stigeoclonium tenue (Ag.) Gomont, which generally accounted for the increase in green algal abundance, varied with nutrient ratio (ANCOVA) when P was the co‐variate. Based on the ANCOVAs, correlations, and one‐way ANOVAs, periphyton in this system appears to be affected by N concentration but not by N:P treatment ratios under nutrient‐rich conditions. When compared with previous studies, these data also suggest that the response of periphyton to in situ treatments constructed with nutrient‐releasing substrata vary between years.

The relationships among disturbance, substratum size and periphyton community structure

Numerous studies have determined the effects of physical disturbance on periphyton, however, the substrata used have varied in size among studies. In this study we examined the influence of substratum size on the change in periphyton exposed to three levels of disturbance. Periphyton communities were established in a large greenhouse tank on square unglazed tiles that were either 2.5, 5, or 7.5 cm on a side. Following community development sets of tiles were randomly assigned to controlled disturbances removing 25%, 50%, or 75% of the community or an undisturbed control. Following disturbance, changes in periphyton density were associated with both disturbance treatment and tile size as was taxa richness. Experimental results and direct observation revealed that algal growth was most concentrated along the edge of the tile and progressively declined toward the center. Thus, substratum size influences colonization and pre-disturbance community structure, which then affects the extent of periphyton community change due to ifferent levels of disturbance.

Benthic Diatom Species List and Environmental Conditions in the Little River Basin, Western Kentucky, USA

ABSTRACT Two hundred eighty-two taxa of diatoms (Bacillariophyta) were identified from composited benthic samples collected at 16 sites on the Little River in western Kentucky in 2000 and 2003. The Little River basin is heavily impacted by non-point source pollution consisting of high nutrient inputs and siltation from agricultural and urban runoff. Pennate diatoms dominated the flora comprising >96% of the total taxa throughout the basin. Commonly occurring pennate species included Achnanthidium minutissimum, Amphora perpusilla, Cocconeis placentula var. euglypta, Gomphonema parvulum, Navicula cryptocephala, N. cryptotenella, N. menisculus, N. minima, N. seminulum, N. tripunctata, Nitzschia amphibia, N. dissipata, N. frustulum, N. palea, Planothidium lanceolata, and Sellophora seminulum. Most common centric species were Cyclotella meneghiniana and Melosira varians. The number of taxa found in the Little River was similar to other eastern North American streams and typical of streams impacted by agricultural and urban non-point source pollution (organic and nutrient enrichment and high siltation). A species checklist of all diatom taxa identified in the Little River with currently accepted nomenclature is presented as a baseline for future comparisons.

Benthic Algae Taxa (Exclusive of Diatoms) of the Little River Basin, Western Kentucky, 2000–2003

ABSTRACT The Little River is a highly disturbed system, heavily impacted by non-point source pollution from agricultural runoff in the form of excessive siltation, nitrogen and phosphorus, and organic pollution. Sixty-seven taxa of non-diatom benthic algae were documented for 16 sites in the Little River basin of western Kentucky during four sampling periods in 2000 and 2003. Algal taxa most often encountered included members of the Cyanophyta: Oscillatoria lutea (15 of 16 sites), O. subbrevis (13 of 16 sites), and Schizothrix calcicola (15 of 16 sites). Chlorophyta taxa most often encountered included Oedogonium sp. and Rhizoclonium hieroglyphicum, both at 10 of 16 sites. No trends were found between the algal taxa and areas of nutrient enrichment in the Little River basin. Because little is known of the benthic algal flora in the Little River, this report represents information complementary to that published previously on the benthic diatom taxa found at the same sites during the same study period.

Genetic Identification of Hatchery Stocks of Brown Trout Using Mitochondrial DNA Polymorphism

Abstract Molecular genetics techniques provide an accurate and cost-effective way to identify hatchery strains and to measure genetic variation in fish populations. In this study, we sought to identify genetic differences at the mitochondrial DNA (mtDNA) level in two of the three hatchery strains of Michigan brown trout Salmo trutta by using restriction fragment length polymorphisms (RFLPs) of segments of mtDNA amplified by polymerase chain reaction. We show that the RFLP approach can provide valuable information about the genetic composition of Michigan brown trout strains and a method of population analysis that can be used to enhance short- and long-term fisheries management studies.

Genetic Variation at the mtDNA ND-1 Locus Among North American Wild and Hatchery Brown Trout (Salmo trutta)

ABSTRACT Despite extensive knowledge of mitochondrial DNA (mtDNA) variation in European brown trout (Salmo trutta) populations, little is known about their nucleotide sequence variation in North America. The objective of this study was to quantify single nucleotide polymorphisms (SNPs) at the ND-1 mtDNA locus of 62 brown trout from hatcheries in Michigan and Wisconsin as well as Michigan streams and Lake Michigan. We identified 25 SNPs that characterized nine distinct mtDNA haplotypes in the Wild Rose, Gilchrist and Seeforellen brown trout strains. Although most SNPs were represented by synonymous nucleotide substitutions, three individuals of the Seeforellen strain had non-synonymous nucleotide changes. MtDNA haplotypes identified in North American brown trout in this study showed nucleotide similarity at the ND-1 locus to brown trout from northern Europe.

What lies beneath? Fungal diversity at the bottom of Lake Michigan and Lake Superior

Fungi are phylogenetically diverse organisms found in nearly every environment as key contributors to the processes of nutrient cycling and decomposition. To date, most fungal diversity has been documented from terrestrial habitats leaving aquatic habitats underexplored. In particular, comparatively little is known about fungi inhabiting freshwater lakes, particularly the benthic zone, which may serve as an untapped resource for fungal biodiversity. Advances in technology allowing for direct sequencing of DNA from environmental samples provide a new opportunity to investigate freshwater benthic fungi. In this study, we employed both culture-dependent and culture-independent methods to evaluate the diversity of fungi in one of the largest freshwater systems on Earth, the North American Laurentian Great Lakes. This study presents the first comprehensive survey of fungi from sediment from Lake Michigan and Lake Superior, resulting in 465 fungal taxa with only 7% of sequence overlap between these two methods. Additionally, culture-independent analyses of the ITS1 and ITS2 regions revealed 49% and 72%, respectively, of the OTUs did not match a described fungal taxonomic group below kingdom Fungi. The low level of sequence overlap between methods and high percentage of fungal taxa that can only be classified at the kingdom level suggests an immense amount of fungal diversity remains to be studied in these aquatic fungal communities.