Scott McNaught | Central Michigan University (original) (raw)

Papers by Scott McNaught

Transactions of the American Fisheries Society, 2020

The inclusion of sublethal behavioral effects in population models has predicted lower estimates ... more The inclusion of sublethal behavioral effects in population models has predicted lower estimates of cohort abundance and survival. Methylmercury (MeHg), a persistent contaminant in the Great Lakes, has been shown to alter foraging and predator avoidance behaviors of larval yellow perch, which may have indirect effects on recruitment. Poor recruitment of yellow perch in Lake Michigan has been

Journal of Great Lakes Research, 2018

Dreissenid mussels are known to disrupt the base of the food web by filter feeding on phytoplankt... more Dreissenid mussels are known to disrupt the base of the food web by filter feeding on phytoplankton; however, they may also directly ingest zooplankton thereby complicating their effects on plankton communities. The objective of this study was to quantify the effects of quagga mussel feeding on the composition and size structure of Lake Michigan zooplankton assemblages. Two mesocosm (six 946 L tanks) experiments were conducted in summer 2013, using quagga mussels and zooplankton collected near Beaver Island, MI, to examine the response of zooplankton communities to the presence and absence of mussels (experiment 1) and varying mussel density (experiment 2). Mesocosms were sampled daily and zooplankton taxa were enumerated and sized using microscopy and FlowCAM® imaging. In experiment 1, the presence of quagga mussels had a rapid negative effect on veliger and copepod nauplii abundance, and a delayed negative effect on rotifer abundance. In experiment 2, mussel density had a negative effect on veliger, nauplii, and copepodite abundance within 24 h. Multivariate analyses revealed a change in zooplankton community composition with increasing mussel density. Ten zooplankton taxa decreased in abundance and frequency as quagga mussel density increased: except for the rotifer Trichocerca sp., treatments with higher mussel densities (i.e., 1327, 3585, and 5389 mussels/m 2) had the greatest negative effect on small-bodied zooplankton (≤128 μm). This study confirms results from small-scale (≤1 L) experiments and demonstrates that quagga mussels can alter zooplankton communities at mesoscales (~1000 L), possibly through a combination of direct consumption and resource depletion.

Wetlands, 2018

Wild rice (Zizania spp.) has ecological and cultural importance in the Great Lakes region, but ha... more Wild rice (Zizania spp.) has ecological and cultural importance in the Great Lakes region, but has been declining due to habitat loss and fragmentation. We investigated the potential impact of bed area and isolation by distance on genetic structure, reproductive effort, and morphometrics in populations of two wild rice species (Z. palustris and Z. aquatica) in Michigan. Leaves were analyzed with Amplified Fragment Length Polymorphisms (AFLPs) and stem height, leaf length, panicle length, and number of male and female flowers were recorded. Despite finding multiple genetic clusters in each species, we found no geographic pattern to the clusters or any isolation by distance. Correlations revealed no associations between bed area and AFLP band diversity, nor bed area and morphometric traits. The number of female flowers was positively correlated with AFLP band diversity, demonstrating a possible impact of genetic diversity on reproductive effort. The results of this study suggest that habitat loss is not yet affecting the genetic diversity of wild rice in Michigan, possibly because of long distance dispersal vectors facilitating gene flow. Nevertheless, the ongoing decline of populations shows their need for protection and restoration, such as through more seeding efforts.

Journal of Great Lakes Research, 2019

The St. Clair River delta, part of the St. Clair-Detroit River System (SCDRS), is the most fished... more The St. Clair River delta, part of the St. Clair-Detroit River System (SCDRS), is the most fished coastal wetland area in the Laurentian Great Lakes and provides nursery habitat for a variety of fish species; however, few large-scale surveys of larval fish have been performed within the delta since the 1980s. Larval fish, zooplankton, and aquatic plants were sampled at 20 sites from May through July in 2010 and 2011 to characterize shallow channel and backwater delta habitats used by fish. The larval fish assemblage was sampled using active and passive gears (conical nets and light traps) and was dominated by Cyprinidae, Catostomidae, and Gobiidae. The microzooplankton assemblage was composed of rotifers, copepod nauplii, and Dreissena spp. veligers, while the macrozooplankton assemblage was composed of mostly cyclopoids and harpacticoids in May and cladocerans later in the season. Scirpus spp. dominated the plant assemblage in June and was replaced by Chara spp. in July. Seasonal compositional shifts were evident for larval fish, zooplankton, and plant assemblages, and greater densities of microzooplankton and cladocerans were typically found in backwater areas. Assemblage compositions were comparable to those in historical surveys but invasive Gobiidae and Dreissena spp. veligers now represent substantial proportions of the larval fish and zooplankton assemblages, respectively. Due to the high connectivity and advective nature of the SCDRS, understanding the larval fish assemblage dynamics of the delta can help inform estimates of system productivity.

II I 'M-/ LI W I FIU U UEI A.' 1 d Ll 'It I.IL .0. § I A.

Limnology and Oceanography, 1999

Trout stocking in the mid-1960s eliminated the calanoid copepod Hesperodiaptomus arcticus and oth... more Trout stocking in the mid-1960s eliminated the calanoid copepod Hesperodiaptomus arcticus and other largebodied crustaceans such as Gammarus lacustris, Daphnia middendorffiana, and Daphnia pulex from many alpine lakes in the Rocky Mountain Parks of Canada. H. arcticus frequently dominates the plankton communities of fishless lakes, preying on rotifers and nauplius larvae. Following the extirpation of H. arcticus, rotifers and small-bodied cyclopoid copepods dominate the zooplankton assemblages of alpine lakes. We studied the zooplankton community of Snowflake Lake, Banff National Park, from 1966 to 1995. H. arcticus was eliminated following stocking of the lake with trout in the 1960s. It failed to become reestablished after the disappearance of the fish population in the mid-1980s. Several species of rotifers and small-bodied crustaceans, species originally rare or absent from the plankton, became abundant following fish stocking and remained so after the fish population declined. In 1992, we reintroduced H. arcticus to Snowflake Lake. The H. arcticus population grew exponentially for 4 yr, but had not reached stable densities typical of unmanipulated alpine lakes by 1995. By 1994, however, even the small population of Hesperodiaptomus was beginning to suppress populations of rotifers, copepod nauplii, and large diatoms. Because H. arcticus is omnivorous, a simple model of cascading trophic interactions did not predict the outcome of trophic manipulations in this alpine lake.

Limnology and Oceanography, 2009

Aquatic prey species respond to predators with fast (developmental) and slow (selective) feedback... more Aquatic prey species respond to predators with fast (developmental) and slow (selective) feedbacks. Natural selection is assumed to fashion details of induction and to modify baseline morphology, but only rarely do we catch the slower (multi-generation) process in action. Laboratory experiments with Bosmina detected predatormediated induction and estimated spine heritability (h 2 5 0.2-0.5). Third Sister Lake, Michigan, U.S.A., Bosmina exhibited induction to resident (Mesocyclops) and to two nonresident, neighborhood predators (Epischura and Leptodora). However, the magnitude of induction in Third Sister Lake Bosmina to nonresident predators (Epischura, Leptodora) was muted, when compared with induction and final spine lengths in Epischura-Leptodora lakes. Inadvertent escape of Leptodora into Third Sister Lake in 1987 created a long-term (multiyear), whole-lake experiment, where resident Bosmina populations fell under intense size selection. During the interval, Leptodora suppressed a late-season smaller, short-featured species (B. freyii), favored seasonal expansion of an overwintering long-featured species (B. liederi), and selected for longer features in the latter species. Before local extinction, defensive spines of B. liederi achieved lengths comparable to populations that co-occur with Epischura and Leptodora.

It has been my intent to investigate the processes which regulate aquatic community composition b... more It has been my intent to investigate the processes which regulate aquatic community composition by discovering those factors which influence the distribution and abundance of one invertebrate predator, Leptodora kindti (Cladocera). By constructing predictive models using published survey data for North American lakes, I suggest that biological factors are important in determining the distribution and abundance of Leptodora. Three distinct patterns emerged from my analysis: (1) Leptodora and the midge larva Chaoborus americanus have non-overlapping distributions; (2) Leptodora is found exclusively in lakes inhabited by planktivorous fish; and (3) Leptodora occurs most frequently in large lakes populated by Daphnia species. I have conducted laboratory and field experiments to explain why Leptodora never co-occurs with Chaoborus americanus. Results from one-on-one encounter trials, seven-day aquarium experiments, and two-week in situ enclosure experiments indicate that third and fourth instar C. americanus are able to consume juvenile Leptodora and significantly reduce its population size. Furthermore, my demonstration that planktivorous fish differentially select midge larvae over Leptodora in laboratory choice experiments suggests that planktivorous fish are able to prevent the establishment of sizable C. americanus populations and release Leptodora from its deleterious interaction with the phantom midge. Alternatively, Leptodora may be more successful in the presence of fish than in the absence of fish because size-selective vertebrate predation produces a zooplankton community which is preferred by Leptodora. By monitoring the zooplankton in 750 liter enclosures during a 16-day field experiment, I was able to show that the bluegill sunfish (Lepomis macrochirus) is able to skew the zooplankton community toward small-bodied individuals which are suitable prey for Leptodora. When in contact with the fish, however, few Leptodora survived to take advantage of the newly available food. Finally, stochastic processes alone may explain the distribution of Leptodora among lakes inhabited by fish. The introduction of Leptodora into a local lake, whose zooplankton community has been monitored for over twenty years, suggests that even short inter-lake distances are effective barriers to the dispersal of some zooplankton species.Ph.D.BiologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/103642/1/9332131.pdfDescription of 9332131.pdf : Restricted to UM users only

Journal of Paleolimnology, 2015

Limnology and Oceanography, 2004

The predaceous cladoceran Leptodora kindti (Focke) became established in Third Sister Lake, Michi... more The predaceous cladoceran Leptodora kindti (Focke) became established in Third Sister Lake, Michigan, after individuals escaped from experimental enclosures in 1987. By 1988, the Leptodora population exhibited seasonal dynamics characteristic of natural populations. The maximum seasonal abundance of Leptodora increased to 85 individuals m Ϫ3 3 yr following the introduction. After the appearance of Leptodora, small-bodied cladocerans (Ceriodaphnia and Bosmina) virtually disappeared from the lake. There were strong seasonal shifts in the dominance patterns of both cladocerans and copepods, and Daphnia species diversity increased. Results from this unplanned introduction suggest that invertebrate predators can have a rapid and lasting effect on prey populations, even in the presence of planktivorous fish. Small-scale (Ͻ20 km) geographic barriers might be as important as large-scale barriers to dispersal of planktonic animals.

Background/Question/Methods Ambystomid salamanders utilize ephemeral ponds for breeding and larva... more Background/Question/Methods Ambystomid salamanders utilize ephemeral ponds for breeding and larval habitat. My focal species are the spotted (Ambystoma maculatum) and the blue-spotted complex (Ambystoma laterale and Ambystoma laterale-jeffersonianum) salamanders. In an initial study in June 2012, I found two ponds, one with only Ambystoma maculatum, and the other only with A. laterale-jeffersonianum larvae. The two hypotheses I am testing are (1) abiotic factors caused these species to breed in one pond over another, or (2) the difference was due to competition. In April 2013, I surveyed 9 ephemeral ponds near Farwell, MI for salamander egg masses. Egg masses were identified to species and their locations within the pond were noted. Within each pond, I haphazardly chose several locations to measure the abiotic variables of pH, temperature, dissolved oxygen (D.O.), conductance, turbidity, and depth. The number of locations chosen was in relation to the size of the pond in order to in...

Journal of Great Lakes Research, 2014

Recent investigations in the Detroit River have revealed renewed spawning activity by several imp... more Recent investigations in the Detroit River have revealed renewed spawning activity by several important fishes, but little is known about their early life history requirements. We surveyed two main channel and two backwater areas in the lower Detroit River weekly from May to July 2007 to assess habitat use by larval fishes. Backwater areas included a soft-sediment embayment (FI) and a hard-sediment area (HIW). Main channel sites were located adjacent to each backwater area. Water temperature, velocity and clarity measurements and zooplankton samples were collected weekly. A macrophyte assessment was conducted in July. Growth and diet of larval yellow perch (Perca flavescens), bluegill (Lepomis macrochirus) and round goby (Neogobius melanostomus) were used to assess habitat quality. Macrophyte diversity and percent cover were higher and velocity lower at FI than HIW. Although larval fish diversity was highest in the main channel, yellow perch and bluegill larvae only grew beyond the yolk stage at FI, where they preferentially selected copepods, while Daphnia were selected in the main channel. Round goby ate harpacticoid copepods and Daphnia and grew at similar rates in HIW and the main channel. These data indicate that FI was a valuable nursery area for yellow perch and bluegill, whereas HIW was better suited to round goby. We only assessed two backwater areas, thus a complete census of wetland areas in the Detroit River is needed to identify valuable habitats. Restoration of shallow backwater areas is essential for rehabilitating fish populations and should be a priority in the Detroit River.

Limnology and Oceanography, 2004

The predaceous cladoceran Leptodora kindti (Focke) became established in Third Sister Lake, Michi... more The predaceous cladoceran Leptodora kindti (Focke) became established in Third Sister Lake, Michigan, after individuals escaped from experimental enclosures in 1987. By 1988, the Leptodora population exhibited seasonal dynamics characteristic of natural populations. The maximum seasonal abundance of Leptodora increased to 85 individuals m Ϫ3 3 yr following the introduction. After the appearance of Leptodora, small-bodied cladocerans (Ceriodaphnia and Bosmina) virtually disappeared from the lake. There were strong seasonal shifts in the dominance patterns of both cladocerans and copepods, and Daphnia species diversity increased. Results from this unplanned introduction suggest that invertebrate predators can have a rapid and lasting effect on prey populations, even in the presence of planktivorous fish. Small-scale (Ͻ20 km) geographic barriers might be as important as large-scale barriers to dispersal of planktonic animals.

Limnology and Oceanography, 2004

Environmental factors regulate biodiversity through species sorting processes. Species distributi... more Environmental factors regulate biodiversity through species sorting processes. Species distributions in communities affect ecosystem processes and environmental factors. These dynamics are determined by the properties (traits) of species in the community. The optimal temperatures for growth, the minimal amount of resource that sustains positive mass balance, and the amount of energy allocated to predator defenses are examples of such traits. Over time, the trait distributions in communities may change in response to environmental changes, which, in turn, changes the processes and consequently the structure of the system. The result of such processes is the focus of complex adaptive systems (CAS) theory. This paper gives an overview of how CAS theory can contribute to understanding the role of biodiversity on the ability of functional groups that make up the ecosystem to change their species compositions in response to changes in the environment. Any trait that requires investment of energy, mass, or time is subjected to a tradeoff for alternative use of this resource. Such interspecies tradeoff relationships can be used to make predictions about past environmental conditions, as well as the response of the properties of a group of species, e.g., total productivity and species distributions, to future changes in the environment. The traitbased framework presented here makes explicit predictions regarding the relation between the environment, trait distributions, and ecosystem processes. Trait variance, a measure of the width of the distribution of traits in the community, is proportional to the rate at which species within functional groups can replace each other in response to environmental changes. This adaptive capacity is crucial for the ecosystem's ability to maintain certain processes under times of change. Examples of empirical tradeoffs are given as well as how to formalize them to use in the CAS framework.

Journal of Plankton Research, 2000

We examined the effect of experimental scale on the predation rate of Gammarus lacustris preying ... more We examined the effect of experimental scale on the predation rate of Gammarus lacustris preying on Daphnia middendorffiana in 20 l cubitainers, 2800 l mesocosms and diurnal whole-lake surveys. The predation rate differed significantly among experimental scales. It was highest in the 20 l cubitainers, intermediate in the 2800 l mesocosms and lowest in the lake. At all experimental scales, the predation of G.lacustris on D.middendorffiana increased as a linear function of prey density (Type I functional response). Very different predation rates were calculated for the whole lake depending on whether D.middendorffiana densities were estimated from whole-water column hauls or stratified depth hauls. This highlights the importance of accurately determining the spatial distribution of prey for estimating reliable in situ predation rates. We also determined prey selection by G.lacustris. Daphnia middendorffiana was strongly selected over the calanoid copepod Hesperodiaptomus arcticus. When presented with different sized Daphnia, G.lacustris preyed size selectively on individuals ≥2 mm. Our results show that the predation rate of small invertebrate predators is sensitive to a wide range of experimental conditions and needs to be corroborated at a variety of scales. We conclude that the impact of G.lacustris on zooplankton communities would be strongest in small fishless lakes or ponds.

Limnology and Oceanography, 2010

Transactions of the American Fisheries Society, 2020

The inclusion of sublethal behavioral effects in population models has predicted lower estimates ... more The inclusion of sublethal behavioral effects in population models has predicted lower estimates of cohort abundance and survival. Methylmercury (MeHg), a persistent contaminant in the Great Lakes, has been shown to alter foraging and predator avoidance behaviors of larval yellow perch, which may have indirect effects on recruitment. Poor recruitment of yellow perch in Lake Michigan has been

Journal of Great Lakes Research, 2018

Dreissenid mussels are known to disrupt the base of the food web by filter feeding on phytoplankt... more Dreissenid mussels are known to disrupt the base of the food web by filter feeding on phytoplankton; however, they may also directly ingest zooplankton thereby complicating their effects on plankton communities. The objective of this study was to quantify the effects of quagga mussel feeding on the composition and size structure of Lake Michigan zooplankton assemblages. Two mesocosm (six 946 L tanks) experiments were conducted in summer 2013, using quagga mussels and zooplankton collected near Beaver Island, MI, to examine the response of zooplankton communities to the presence and absence of mussels (experiment 1) and varying mussel density (experiment 2). Mesocosms were sampled daily and zooplankton taxa were enumerated and sized using microscopy and FlowCAM® imaging. In experiment 1, the presence of quagga mussels had a rapid negative effect on veliger and copepod nauplii abundance, and a delayed negative effect on rotifer abundance. In experiment 2, mussel density had a negative effect on veliger, nauplii, and copepodite abundance within 24 h. Multivariate analyses revealed a change in zooplankton community composition with increasing mussel density. Ten zooplankton taxa decreased in abundance and frequency as quagga mussel density increased: except for the rotifer Trichocerca sp., treatments with higher mussel densities (i.e., 1327, 3585, and 5389 mussels/m 2) had the greatest negative effect on small-bodied zooplankton (≤128 μm). This study confirms results from small-scale (≤1 L) experiments and demonstrates that quagga mussels can alter zooplankton communities at mesoscales (~1000 L), possibly through a combination of direct consumption and resource depletion.

Wetlands, 2018

Wild rice (Zizania spp.) has ecological and cultural importance in the Great Lakes region, but ha... more Wild rice (Zizania spp.) has ecological and cultural importance in the Great Lakes region, but has been declining due to habitat loss and fragmentation. We investigated the potential impact of bed area and isolation by distance on genetic structure, reproductive effort, and morphometrics in populations of two wild rice species (Z. palustris and Z. aquatica) in Michigan. Leaves were analyzed with Amplified Fragment Length Polymorphisms (AFLPs) and stem height, leaf length, panicle length, and number of male and female flowers were recorded. Despite finding multiple genetic clusters in each species, we found no geographic pattern to the clusters or any isolation by distance. Correlations revealed no associations between bed area and AFLP band diversity, nor bed area and morphometric traits. The number of female flowers was positively correlated with AFLP band diversity, demonstrating a possible impact of genetic diversity on reproductive effort. The results of this study suggest that habitat loss is not yet affecting the genetic diversity of wild rice in Michigan, possibly because of long distance dispersal vectors facilitating gene flow. Nevertheless, the ongoing decline of populations shows their need for protection and restoration, such as through more seeding efforts.

Journal of Great Lakes Research, 2019

The St. Clair River delta, part of the St. Clair-Detroit River System (SCDRS), is the most fished... more The St. Clair River delta, part of the St. Clair-Detroit River System (SCDRS), is the most fished coastal wetland area in the Laurentian Great Lakes and provides nursery habitat for a variety of fish species; however, few large-scale surveys of larval fish have been performed within the delta since the 1980s. Larval fish, zooplankton, and aquatic plants were sampled at 20 sites from May through July in 2010 and 2011 to characterize shallow channel and backwater delta habitats used by fish. The larval fish assemblage was sampled using active and passive gears (conical nets and light traps) and was dominated by Cyprinidae, Catostomidae, and Gobiidae. The microzooplankton assemblage was composed of rotifers, copepod nauplii, and Dreissena spp. veligers, while the macrozooplankton assemblage was composed of mostly cyclopoids and harpacticoids in May and cladocerans later in the season. Scirpus spp. dominated the plant assemblage in June and was replaced by Chara spp. in July. Seasonal compositional shifts were evident for larval fish, zooplankton, and plant assemblages, and greater densities of microzooplankton and cladocerans were typically found in backwater areas. Assemblage compositions were comparable to those in historical surveys but invasive Gobiidae and Dreissena spp. veligers now represent substantial proportions of the larval fish and zooplankton assemblages, respectively. Due to the high connectivity and advective nature of the SCDRS, understanding the larval fish assemblage dynamics of the delta can help inform estimates of system productivity.

II I 'M-/ LI W I FIU U UEI A.' 1 d Ll 'It I.IL .0. § I A.

Limnology and Oceanography, 1999

Trout stocking in the mid-1960s eliminated the calanoid copepod Hesperodiaptomus arcticus and oth... more Trout stocking in the mid-1960s eliminated the calanoid copepod Hesperodiaptomus arcticus and other largebodied crustaceans such as Gammarus lacustris, Daphnia middendorffiana, and Daphnia pulex from many alpine lakes in the Rocky Mountain Parks of Canada. H. arcticus frequently dominates the plankton communities of fishless lakes, preying on rotifers and nauplius larvae. Following the extirpation of H. arcticus, rotifers and small-bodied cyclopoid copepods dominate the zooplankton assemblages of alpine lakes. We studied the zooplankton community of Snowflake Lake, Banff National Park, from 1966 to 1995. H. arcticus was eliminated following stocking of the lake with trout in the 1960s. It failed to become reestablished after the disappearance of the fish population in the mid-1980s. Several species of rotifers and small-bodied crustaceans, species originally rare or absent from the plankton, became abundant following fish stocking and remained so after the fish population declined. In 1992, we reintroduced H. arcticus to Snowflake Lake. The H. arcticus population grew exponentially for 4 yr, but had not reached stable densities typical of unmanipulated alpine lakes by 1995. By 1994, however, even the small population of Hesperodiaptomus was beginning to suppress populations of rotifers, copepod nauplii, and large diatoms. Because H. arcticus is omnivorous, a simple model of cascading trophic interactions did not predict the outcome of trophic manipulations in this alpine lake.

Limnology and Oceanography, 2009

Aquatic prey species respond to predators with fast (developmental) and slow (selective) feedback... more Aquatic prey species respond to predators with fast (developmental) and slow (selective) feedbacks. Natural selection is assumed to fashion details of induction and to modify baseline morphology, but only rarely do we catch the slower (multi-generation) process in action. Laboratory experiments with Bosmina detected predatormediated induction and estimated spine heritability (h 2 5 0.2-0.5). Third Sister Lake, Michigan, U.S.A., Bosmina exhibited induction to resident (Mesocyclops) and to two nonresident, neighborhood predators (Epischura and Leptodora). However, the magnitude of induction in Third Sister Lake Bosmina to nonresident predators (Epischura, Leptodora) was muted, when compared with induction and final spine lengths in Epischura-Leptodora lakes. Inadvertent escape of Leptodora into Third Sister Lake in 1987 created a long-term (multiyear), whole-lake experiment, where resident Bosmina populations fell under intense size selection. During the interval, Leptodora suppressed a late-season smaller, short-featured species (B. freyii), favored seasonal expansion of an overwintering long-featured species (B. liederi), and selected for longer features in the latter species. Before local extinction, defensive spines of B. liederi achieved lengths comparable to populations that co-occur with Epischura and Leptodora.

It has been my intent to investigate the processes which regulate aquatic community composition b... more It has been my intent to investigate the processes which regulate aquatic community composition by discovering those factors which influence the distribution and abundance of one invertebrate predator, Leptodora kindti (Cladocera). By constructing predictive models using published survey data for North American lakes, I suggest that biological factors are important in determining the distribution and abundance of Leptodora. Three distinct patterns emerged from my analysis: (1) Leptodora and the midge larva Chaoborus americanus have non-overlapping distributions; (2) Leptodora is found exclusively in lakes inhabited by planktivorous fish; and (3) Leptodora occurs most frequently in large lakes populated by Daphnia species. I have conducted laboratory and field experiments to explain why Leptodora never co-occurs with Chaoborus americanus. Results from one-on-one encounter trials, seven-day aquarium experiments, and two-week in situ enclosure experiments indicate that third and fourth instar C. americanus are able to consume juvenile Leptodora and significantly reduce its population size. Furthermore, my demonstration that planktivorous fish differentially select midge larvae over Leptodora in laboratory choice experiments suggests that planktivorous fish are able to prevent the establishment of sizable C. americanus populations and release Leptodora from its deleterious interaction with the phantom midge. Alternatively, Leptodora may be more successful in the presence of fish than in the absence of fish because size-selective vertebrate predation produces a zooplankton community which is preferred by Leptodora. By monitoring the zooplankton in 750 liter enclosures during a 16-day field experiment, I was able to show that the bluegill sunfish (Lepomis macrochirus) is able to skew the zooplankton community toward small-bodied individuals which are suitable prey for Leptodora. When in contact with the fish, however, few Leptodora survived to take advantage of the newly available food. Finally, stochastic processes alone may explain the distribution of Leptodora among lakes inhabited by fish. The introduction of Leptodora into a local lake, whose zooplankton community has been monitored for over twenty years, suggests that even short inter-lake distances are effective barriers to the dispersal of some zooplankton species.Ph.D.BiologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/103642/1/9332131.pdfDescription of 9332131.pdf : Restricted to UM users only

Journal of Paleolimnology, 2015

Limnology and Oceanography, 2004

The predaceous cladoceran Leptodora kindti (Focke) became established in Third Sister Lake, Michi... more The predaceous cladoceran Leptodora kindti (Focke) became established in Third Sister Lake, Michigan, after individuals escaped from experimental enclosures in 1987. By 1988, the Leptodora population exhibited seasonal dynamics characteristic of natural populations. The maximum seasonal abundance of Leptodora increased to 85 individuals m Ϫ3 3 yr following the introduction. After the appearance of Leptodora, small-bodied cladocerans (Ceriodaphnia and Bosmina) virtually disappeared from the lake. There were strong seasonal shifts in the dominance patterns of both cladocerans and copepods, and Daphnia species diversity increased. Results from this unplanned introduction suggest that invertebrate predators can have a rapid and lasting effect on prey populations, even in the presence of planktivorous fish. Small-scale (Ͻ20 km) geographic barriers might be as important as large-scale barriers to dispersal of planktonic animals.

Background/Question/Methods Ambystomid salamanders utilize ephemeral ponds for breeding and larva... more Background/Question/Methods Ambystomid salamanders utilize ephemeral ponds for breeding and larval habitat. My focal species are the spotted (Ambystoma maculatum) and the blue-spotted complex (Ambystoma laterale and Ambystoma laterale-jeffersonianum) salamanders. In an initial study in June 2012, I found two ponds, one with only Ambystoma maculatum, and the other only with A. laterale-jeffersonianum larvae. The two hypotheses I am testing are (1) abiotic factors caused these species to breed in one pond over another, or (2) the difference was due to competition. In April 2013, I surveyed 9 ephemeral ponds near Farwell, MI for salamander egg masses. Egg masses were identified to species and their locations within the pond were noted. Within each pond, I haphazardly chose several locations to measure the abiotic variables of pH, temperature, dissolved oxygen (D.O.), conductance, turbidity, and depth. The number of locations chosen was in relation to the size of the pond in order to in...

Journal of Great Lakes Research, 2014

Recent investigations in the Detroit River have revealed renewed spawning activity by several imp... more Recent investigations in the Detroit River have revealed renewed spawning activity by several important fishes, but little is known about their early life history requirements. We surveyed two main channel and two backwater areas in the lower Detroit River weekly from May to July 2007 to assess habitat use by larval fishes. Backwater areas included a soft-sediment embayment (FI) and a hard-sediment area (HIW). Main channel sites were located adjacent to each backwater area. Water temperature, velocity and clarity measurements and zooplankton samples were collected weekly. A macrophyte assessment was conducted in July. Growth and diet of larval yellow perch (Perca flavescens), bluegill (Lepomis macrochirus) and round goby (Neogobius melanostomus) were used to assess habitat quality. Macrophyte diversity and percent cover were higher and velocity lower at FI than HIW. Although larval fish diversity was highest in the main channel, yellow perch and bluegill larvae only grew beyond the yolk stage at FI, where they preferentially selected copepods, while Daphnia were selected in the main channel. Round goby ate harpacticoid copepods and Daphnia and grew at similar rates in HIW and the main channel. These data indicate that FI was a valuable nursery area for yellow perch and bluegill, whereas HIW was better suited to round goby. We only assessed two backwater areas, thus a complete census of wetland areas in the Detroit River is needed to identify valuable habitats. Restoration of shallow backwater areas is essential for rehabilitating fish populations and should be a priority in the Detroit River.

Limnology and Oceanography, 2004

The predaceous cladoceran Leptodora kindti (Focke) became established in Third Sister Lake, Michi... more The predaceous cladoceran Leptodora kindti (Focke) became established in Third Sister Lake, Michigan, after individuals escaped from experimental enclosures in 1987. By 1988, the Leptodora population exhibited seasonal dynamics characteristic of natural populations. The maximum seasonal abundance of Leptodora increased to 85 individuals m Ϫ3 3 yr following the introduction. After the appearance of Leptodora, small-bodied cladocerans (Ceriodaphnia and Bosmina) virtually disappeared from the lake. There were strong seasonal shifts in the dominance patterns of both cladocerans and copepods, and Daphnia species diversity increased. Results from this unplanned introduction suggest that invertebrate predators can have a rapid and lasting effect on prey populations, even in the presence of planktivorous fish. Small-scale (Ͻ20 km) geographic barriers might be as important as large-scale barriers to dispersal of planktonic animals.

Limnology and Oceanography, 2004

Environmental factors regulate biodiversity through species sorting processes. Species distributi... more Environmental factors regulate biodiversity through species sorting processes. Species distributions in communities affect ecosystem processes and environmental factors. These dynamics are determined by the properties (traits) of species in the community. The optimal temperatures for growth, the minimal amount of resource that sustains positive mass balance, and the amount of energy allocated to predator defenses are examples of such traits. Over time, the trait distributions in communities may change in response to environmental changes, which, in turn, changes the processes and consequently the structure of the system. The result of such processes is the focus of complex adaptive systems (CAS) theory. This paper gives an overview of how CAS theory can contribute to understanding the role of biodiversity on the ability of functional groups that make up the ecosystem to change their species compositions in response to changes in the environment. Any trait that requires investment of energy, mass, or time is subjected to a tradeoff for alternative use of this resource. Such interspecies tradeoff relationships can be used to make predictions about past environmental conditions, as well as the response of the properties of a group of species, e.g., total productivity and species distributions, to future changes in the environment. The traitbased framework presented here makes explicit predictions regarding the relation between the environment, trait distributions, and ecosystem processes. Trait variance, a measure of the width of the distribution of traits in the community, is proportional to the rate at which species within functional groups can replace each other in response to environmental changes. This adaptive capacity is crucial for the ecosystem's ability to maintain certain processes under times of change. Examples of empirical tradeoffs are given as well as how to formalize them to use in the CAS framework.

Journal of Plankton Research, 2000

We examined the effect of experimental scale on the predation rate of Gammarus lacustris preying ... more We examined the effect of experimental scale on the predation rate of Gammarus lacustris preying on Daphnia middendorffiana in 20 l cubitainers, 2800 l mesocosms and diurnal whole-lake surveys. The predation rate differed significantly among experimental scales. It was highest in the 20 l cubitainers, intermediate in the 2800 l mesocosms and lowest in the lake. At all experimental scales, the predation of G.lacustris on D.middendorffiana increased as a linear function of prey density (Type I functional response). Very different predation rates were calculated for the whole lake depending on whether D.middendorffiana densities were estimated from whole-water column hauls or stratified depth hauls. This highlights the importance of accurately determining the spatial distribution of prey for estimating reliable in situ predation rates. We also determined prey selection by G.lacustris. Daphnia middendorffiana was strongly selected over the calanoid copepod Hesperodiaptomus arcticus. When presented with different sized Daphnia, G.lacustris preyed size selectively on individuals ≥2 mm. Our results show that the predation rate of small invertebrate predators is sensitive to a wide range of experimental conditions and needs to be corroborated at a variety of scales. We conclude that the impact of G.lacustris on zooplankton communities would be strongest in small fishless lakes or ponds.

Limnology and Oceanography, 2010