Donald G. Uzarski

Biomass and Pigments of Benthic Algae

Abstract Biomass is one of the most fundamental measurements made in ecology. In stream ecology, biomass is frequently used to estimate the abundance of benthic primary producers, both autotrophic and heterotrophic. In this chapter, we (1) provide a context for the study of benthic algal biomass; (2) discuss in detail some of the more commonly used approaches to measure benthic algal biomass; and (3) describe a field exercise to examine the influence of irradiance on algal biomass, whereby these approaches can be employed and compared with each other to assess their individual performance.

Fish Habitat Use Within and Across Wetland Classes in Coastal Wetlands of the Five Great Lakes: Development of a Fish-based Index of Biotic Integrity

The relative importance of Great Lake, ecoregion, wetland type, and plant zonation in structuring fish community composition was determined for 61 Great Lakes coastal wetlands sampled in 2002. These wetlands, from all five Great Lakes, spanned nine ecoregions and four wetland types (open lacustrine, protected lacustrine, barrier-beach, and drowned river mouth). Fish were sampled with fyke nets, and physical and chemical parameters were determined for inundated plant zones in each wetland. Land use/cover was calculated for 1- and 20-km buffers from digitized imagery. Fish community composition within and among wetlands was compared using correspondence analyses, detrended correspondence analyses, and non-metric multidimensional scaling. Within-site plant zonation was the single most important variable structuring fish communities regardless of lake, ecoregion, or wetland type. Fish community composition correlated with chemical/physical and land use/cover variables. Fish community composition shifted with nutrients and adjacent agriculture within vegetation zone. Fish community composition was ordinated from Scirpus, Eleocharis, and Zizania, to Nuphar/Nymphaea, and Pontederia/Sagittaria/Peltandra to Spargainium to Typha. Once the underlying driver in fish community composition was determined to be plant zonation, data were stratified by vegetation type and an IBI was developed for coastal wetlands of the entire Great Lakes basin.

Validation and performance of an invertebrate index of biotic integrity for Lakes Huron and Michigan fringing wetlands during a period of lake level decline

Development of indicators of ‘ecosystem health’ for the Great Lakes was identified as a major need at the State-of-the-Lakes Ecosystem Conference in 1998, 2000, and 2002. Our goal was to develop an invertebrate-based index of biotic integrity that was robust to water level fluctuations and applied to broad classes of lacustrine wetlands across wave-exposure gradients. Our objectives were to evaluate the performance and test the robustness of our preliminary index (e.g., Burton et al., 1999) at a range of water levels, eliminate any problems with the index of biotic integrity, remove the preliminary status, test the index on similar wetlands of Lake Michigan, and establish stressor:ecological-response relationships. Twenty-two sites, both open- and protected-fringing lacustrine marshes of Lake Huron and Michigan were selected for study. Correspondence analysis and Mann-Whitney U tests were used to test the robustness of existing metrics and search for additional metrics. Wilcoxon Signed Rank tests were used to determine if metrics were responding to inter-annual water level fluctuation. Principal components analysis and Pearson correlations were used to establish stressor:ecological response relationships. Analyses confirmed the utility of most of the metrics suggested in our preliminary index, but we recommended several improvements. With improvements, the index was able to place all sites in a comparable order of disturbance that we placed them a priori based on adjacent landuse/landcover, limnological parameters and observed disturbances. The improved index worked very well from 1998 through 2001 despite the substantial decreases in lake level over this time-period. Analyses of 2001 data collected from similar fringing wetlands along the northern shore of Lake Michigan suggested that the index could also be used for fringing wetlands of northern Lake Michigan. We are confident that our index is ready for implementation as a tool for agencies to use in assessing wetland condition for Lakes Huron and Michigan fringing wetlands.

INFLUENCE OF CATTLE GRAZING AND PASTURE LAND USE ON MACROINVERTEBRATE COMMUNITIES IN FRESHWATER WETLANDS

Responses of wetland abiotic variables and aquatic invertebrate community structure to cattle stocking density, pasture type, and dominant vegetation were evaluated in subtropical pastures. Cattle were stocked at four treatment levels on improved (fertilized) and semi-native (unfertilized) pastures in south-central Florida, USA. Improved pasture wetlands were dominated either byPanicum hemitomon (maidencane) or by a mixture ofPolygonum spp. (smartweed) andJuncus effusus; semi-native pasture wetlands were dominated mainly by maidencane. Cattle stocking density had few significant effects on water-column nutrient concentration or invertebrate community structure. However, water-column nutrient concentrations were significantly greater in the wetlands on improved pastures compared to semi-native pastures. Invertebrate richness and diversity were greater in wetlands on semi-native pastures than on improved pastures, despite lower nutrient concentrations in the former. Overall, the cattle stocking treatment had little impact on invertebrate community structure in these systems relative to prior pasture land use. However, vegetation type influenced invertebrate communities and explained some of the differences between pasture types. Seminative (lower nutrient) wetland pastures dominated by maidencane had significantly greater invertebrate richness and diversity than improved (higher nutrient) wetland pastures dominated by mixed vegetation but showed no difference when compared to improved wetland pastures dominated by maidencane. Chironomids were the dominant invertebrate in wetlands of both pasture types. Correspondence analysis revealed that ostracods and Culicidae larvae might be useful as bioindicators of subtropical wetlands that are experiencing cultural eutrophication.

Sampling a Littoral Fish Assemblage: Comparison of Small-Mesh Fyke Netting and Boat Electrofishing

Abstract We compared small-mesh (4-mm) fyke netting and boat electrofishing for sampling a littoral fish assemblage in Muskegon Lake, Michigan. We hypothesized that fyke netting selects for small-bodied fishes and electrofishing selects for large-bodied fishes. Three sites were sampled during May (2004 and 2005), July (2005 only), and September (2004 and 2005). We found that the species composition of captured fish differed considerably between fyke netting and electrofishing based on nonmetric multidimensional scaling (NMDS). Species strongly associated with fyke netting (based on NMDS and relative abundance) included the brook silverside Labidesthes sicculus, banded killifish Fundulus diaphanus, round goby Neogobius melanostomus, mimic shiner Notropis volucellus, and bluntnose minnow Pimephales notatus, whereas species associated with electrofishing included the Chinook salmon Oncorhynchus tshawytscha, catostomids (Moxostoma spp. and Catostomus spp.), freshwater drum Aplodinotus grunniens, walleye Sande...

Invertebrate habitat use in relation to fetch and plant zonation in northern Lake Huron coastal wetlands

Northern Lake Huron marshes are among the most pristine wetlands in the Great Lakes. Almost 200 invertebrate taxa were collected from eight of these marshes from 1997 through 2001. Our objective was to explore relationships between wave exposure (fetch), plant community zones and invertebrate community composition using exploratory data analysis of invertebrate relative abundance. Effective fetch, an exposure measure which integrates fetch along three directions, ranged from 0.4 to 35.3 km. Invertebrates were collected with dip nets from wet meadow, Typha, and inner and outer Scirpus zones from 3 very protected (fetch <1 km), 3 protected (fetch 1–10 km) and 2 exposed (>10 km) marshes. Correspondence analyses of invertebrate relative abundance did not plot invertebrate communities of wet meadows along fetch gradients even though 7 of 30 common taxa were significantly (p < 0.05) correlated with fetch. After removing wet meadow data, correspondence analyses of data from remaining plant zones plotted marshes according to fetch with very protected and exposed sites at opposite ends of U-shaped gradients. Most taxa were generalists, occurred in marshes in all exposure categories, and plotted in the middle of correspondence analyses plots. Characteristic taxa plotting at the very protected end of the gradient included Gammarus, Crangonyx, Caecidotea, Chironomini, Tanytarsini, most Gastropoda and Sphaeriidae. Characteristic taxa plotting at the most exposed end included Sigara, Trichocorixa, Naididae (Stylaria), Tubificidae, and Bezzia. We present a conceptual model of potential changes in invertebrate community composition along gradients of wave exposure. In very protected marshes, organic sediments, detritus, and plant density are higher and dissolved oxygen is lower than in exposed marshes. Conditions are too harsh for some taxa found in very protected marshes.

Distribution of Round Gobies in Coastal Areas of Lake Michigan: Are Wetlands Resistant to Invasion?

ABSTRACT Great Lakes coastal wetlands may be more resistant to invasion by certain nonindigenous species and thus serve as refuge habitats for native species. As a first step in testing this hypothesis, we investigated the distribution of round goby (Apollonia melanostomus, formerly Neogobius melanostomus) in the lower reaches of several Lake Michigan tributary systems that contain both wet-land and lake habitats near their confluences with Lake Michigan. Using fyke nets, we sampled round gobies in lake and adjacent wetland habitats in four systems in 2004 and six systems in 2005. In each macrohabitat (lake or wetland), we sampled three microhabitats (mono-dominant stands of Nuphar, beds of submersed aquatic vegetation, and bare sediment). We found that round goby catch was generally lower in wetland macrohabitats than adjacent lake macrohabitats and that round gobies appeared to prefer beds of submersed aquatic vegetation in lakes among the three microhabitats. The majority of round gobies in all habitats were relatively small (< 7 cm standard length). We also found a significant negative correlation between round goby catch and distance of sampling points from the Lake Michigan shoreline in 2005, suggesting that 1) Lake Michigan nearshore waters (including the connecting navigation channels and pier areas) may be serving as round goby spawning and nursery habitats with subsequent dispersal into the tributary lake/wetland complexes, and 2) round gobies may still be invading these systems from Lake Michigan. Our results provide evidence that coastal wetland habitats are more resistant to invasion by round gobies than adjacent lake habitats.

MACROINVERTEBRATE COMMUNITY COMPOSITION IN RELATION TO ANTHROPOGENIC DISTURBANCE, VEGETATION, AND ORGANIC SEDIMENT DEPTH IN FOUR LAKE MICHIGAN DROWNED RIVER-MOUTH WETLANDS

Lake Michigan drowned river-mouth wetlands have a unique geomorphology and hydrology. Macroinvertebrate communities in these systems respond to multiple biotic and abiotic factors that are not well understood. In June and August 2003, we sampled macroinvertebrate communities at 22 sites in four Lake Michigan drowned river-mouth wetlands. Sites were distributed along gradients of anthropogenic disturbance, vegetation, and sediment types. The relative influences of anthropogenic disturbance, vegetation, and sediment type on macroinvertebrate community composition were determined using non-metric multidimensional scaling (NMDS) and multi-response permutation procedures (MRPP). The depth of organic deposits best explained the gradients revealed with NMDS and MRPP for both sampling dates. The MRPP did not detect differences in community composition among vegetation types and wetlands with different levels of anthropogenic disturbance. These results suggest that 1) macroinvertebrate community structure in Great Lakes drowned river-mouth habitats is influenced substantially by sediment characteristics, and 2) anthropogenic practices that affect the deposition of organic sediment in coastal wetlands (e.g., eutrophication and hydrologic manipulation) will likely affect macroinvertebrate community structure.

The Interplay of Morphology, Habitat, Resource Use, and Genetic Relationships in Young Yellow Perch

Abstract Morphological divergence resulting from differences in resource and habitat use is common in many fishes inhabiting postglacial ecosystems. We tested whether young yellow perch Perca flavescens differ in morphology, genetic composition, or diet in the nearshore (deep open-water) versus wetland and littoral habitats (shallow zones) of Lake Michigan and Saginaw Bay, Lake Huron. Twenty-one morphological measurements and six meristic counts were compared for 132 age-1 yellow perch, and the genetic variation at 12 nuclear DNA microsatellite loci was assessed for a subset of age-1 individuals across habitats and adults from nearshore zones. The results showed morphological and genetic divergence in yellow perch between Lake Michigan and Lake Huron and among those in nearshore versus wetland habitats in Lake Michigan (but not Lake Huron). Lake Huron yellow perch had deeper, longer bodies and larger dorsal fins than those from Lake Michigan. Those in nearshore habitats from both lakes had deeper, longer ...

Habitat Use and Diet of the Round Goby (Neogobius melanostomus) in Coastal Areas of Lake Michigan and Lake Huron

ABSTRACT The non-indigenous round goby (Neogobius melanostomus) has caused considerable impact in the Laurentian Great Lakes. We sampled round gobies in shoreline habitats and tributary systems of Lake Michigan and Lake Huron to determine patterns of habitat use and diet, including the extent dreissenid mussels were consumed. Along the shoreline, round goby catch did not significantly differ based on the presence of emergent vegetation, but deeper habitats were preferred relative to shallow areas closer to shore. In tributary systems, submersed aquatic vegetation in coastal lakes was preferred. The majority of round gobies were small, generally between 3 and 7 cm, and had diets comprised mainly of zooplankton and dipterans with few dreissenids. Our results indicate that the round goby has invaded coastal areas inconsistently across habitat types and that the species can proliferate in the absence of dreissenid mussels.