M.Sc. / Please refer to full text to view abstract

Two benthic amphipod species (Crangonyx richmondensis var occidentalis Hubricht and Harrison and Hyalella azteca Saussure) live together in Marion Lake, but, as previous workers have shown, differ markedly in the distribution of their numbers. The aim of the study was to compare the behaviour of the two species and to see if any differences might account for the differences in distribution. Particular attention was paid to movement and feeding behaviour. Crangonyx was equally abundant on the bottom at all depths in the lake; Hyalella was abundant in the shallows (1m) and scarce in the deeper waters ( 3 m). Numbers of each species differed among areas in the lake. Crangonyx usually moved by crawling over the mud, and seldom swam. It seemed to find food by its smell or motion or both, and to recognize food by touch or taste. It attacked living prey by pouncing on it and grasping it with its gnatho-pods. In contrast, Hyalella moved mainly in a series of swims and pauses. Hyalella fed by grazing on the mud and rooted aquatics, and ingesting detritus. Both species moved away from sources of light. When food was present in various distributions, the search patterns of Crangonyx differed: some animals turned back and thoroughly searched the area where they had just found food; others crawled along a relatively straight path; yet others behaved in an intermediate manner. In general, Crangonyx seemed to be quicker at finding clumped food than uniformly distributed food. In the absence of food, some individual Crangonyx turned more than others. Hyalella searched by swimming, pausing on a surface, and remaining where food was present. Probably neither species moves frequently between depth zones, although both species are mobile enough to do so. Marked amphipods placed at 1 - and 3-m depths in the lake were recaptured in samples taken 1 and 4 m from the release point after an hour. Fewer marked amphipods of either species were recaptured in the deep area than in the shallow area, indicating that they left the deep area faster. Of the behavioural differences noted, only the difference in feeding habits between the species seems likely to account, at least in part, for the difference in the distribution of their numbers. Recent work by Dr. Hargrave has shown that epibenthic algal production decreases with depth, though not as sharply as Hyalella numbers. In laboratory substrate-choice experiments, Hyalella chose areas of abundant food. Its assimilation efficiency and growth differed when it fed on different sediment microflora. Dr. Gruendling found that the abundance of the algal groups in Marion Lake differed with depth. The distribution of Hyalella may be related to the distribution of certain species of algae in its diet. The distribution of food for Crangonyx is unknown. / Science, Faculty of / Zoology, Department of / Graduate

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With rising salinity levels in many freshwaters across the globe caused by for example sealevel rise and de-icing salts, it becomes important to understand what effect it has on freshwater ecosystems, since the lakes and rivers themselves are important parts in the global carbon cycle. In this study I have looked at what effects increased salinity levels have on different lakes metabolism, specifically oxygen concentration and primary production. The experiment was conducted using mesocosms in three different lakes in Sweden, separated both geographically and by nutrient status (eutrophic, oligotrophic, and dystrophic as well as oligotrophic). The response to increased salinity differed between the lakes; the increased salinity had a strong negative effect on the oligotrophic lake. In general, increased salinity caused a decline in oxygen content, both the maximum value and the amount of diurnal variation, as well as primary production. Therefore, the conclusion is that a rise in salinity will affect lake metabolism in a detrimental way, with a stronger effect on more sensitive lakes. / Med stigande saltnivåer i många sötvatten världen över, orsakade av exempelvis ökande havsnivåer och applicering av vägsalt, blir det viktigt att förstå vilken påverkan detta har på ekosystem i sötvatten då de utgör en viktig del I den globala kolcykeln. I den här studien har jag tittat på vilken effekt förhöjda salthalter har på olika sjöars metabolism, specifikt syrehalt och primärproduktion. Experimentet utfördes med hjälp av mesokosmer i tre olika svenska sjöar, skilda både geografiskt och trofiskt (eutrof, oligotrof samt dystrof och oligotrof). Sjöarnas respons till den ökade salthalten varierade; saltet hade en starkt negativ effekt på den oligotrofa sjön. På en generell nivå så sjönk syrehalten, både maximum värden och dygnsvariationen, samt primärproduktionen vid högre salthalter. Slutsatsen blir därför att ökade saltnivåer kommer att påverka sjöars metabolism negativt, med en starkare effekt på mer känsliga sjöar.

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<p>Blanding’s Turtles (Emydoidea blandingii) and Wood Turtles (Glyptemys insculpta) face population declines range wide, largely because of degradation and loss of habitat in the landscapes  they occupy. Studies of spatial ecology inform land managers of both the resource needs of animal  populations and provide insight on site specific conservation priorities. I examined movements  and habitat use of overlapping populations of Blanding’s Turtles and Wood Turtles at a site in  northern Michigan. I used radio telemetry to locate turtles of each species over the course of two  active seasons. I examined full active season and bi-weekly movement patterns and compared  activity between the species and sexes of each using one-way analysis of covariance (ANCOVA)  and repeated measures analysis of variance (RM ANOVA), respectively. Using multiple  commonly used spatial metrics, including range length, 100% minimum convex polygons (MCP),  95% MCP, 50% MCP, and 95% kernel density estimation (KDE), I estimated seasonal activity  ranges of turtles and examined site fidelity, making comparisons of species and sexes using two?way multivariate analysis of variance (MANOVA). Finally, I used Euclidean Distance Analysis  to examine habitat use at Johnson’s 2nd and 3rd orders of selection, making comparisons at different  levels using MANOVA. Movement analyses suggest that Blanding’s Turtles and Wood Turtles at  this site travel similar distances over the active season and during different seasonal periods,  though females of both species make slightly larger movements during the spring nesting season and male Wood Turtles move more than females in late summer. Activity ranges were individually  variable, but comparable among species and sexes. Wood Turtles do appear to exhibit site fidelity  at this site, occupying similarly sized and overlapping activity ranges year to year. Habitat  selection was evident at the 2nd order for Wood Turtles, indicating favorable use of creek, mid?canopy, and high-canopy upland habitat types and avoidance of river habitat. Blanding’s Turtles  also showed selection of habitat at the second order, with scrub-shrub and cut or burned areas  ranking highest among available habitat types. Neither Wood Turtles nor Blanding’s Turtles  showed evidence of habitat selection at the 3rd order, which may indicate an abundance of high?quality habitat available to these species at this site. Maintenance of corridors between high-use  habitat areas, and mitigation of threats especially during times of greater movement may be  advantageous to the conservation of Blanding’s Turtles and Wood Turtles at this site. </p>

<p>Per-and  polyfluoroalkyl  substances  (PFAS)  are  a  large  group  of  emerging  contaminants  that include astrong carbon-flourine bond that makes the compounds resistant to physical, chemical and  biological  degradation.  They  are  found  in  drinking  water  supplies,  daily  human  products, manufacturing  facilities,  and  in  areas  where  aqueous  film-forming  foam  (AFFF)was  used  to extinguish fires. Toxicity levels of these chemicals can vary depending on the characteristics of the specific chemical; longer carbon chain has shown to be more bioaccumulative and toxic than shorter chain length PFAS. Many studies have recognized perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) to be a substantial concern due to their known toxicity to wildlife. For example, studies show strong evidence that PFOA and PFOS suppress the antibody response from animals. Due to adverse health effects and public concern, the U.S stopped perfluorooctanoic acid (PFOA) manufacturing and switched to the production of an alternative fluorinated compound known  as  hexafluoropropylene  oxide  (HFPO)  dimer  acid  or  GenX,  which  is  thought  to  beless bioaccumulative and therefore, potentially less toxic. These anthropogenic pollutants are one of many stressors acting on aquatic organisms like anurans. Natural stressors such as the devastating fungal  pathogen Batrachocytrium  dendrobatidis(Bd)  is  another  stressor  impacting  amphibian populations.  Despite the co-occurrence of these stressors, no studies have examined interactive effects of the fungal pathogen Bd and PFAS, or whether PFAS effects carry over into the terrestrial environment aftera larvae  exposure. This study  tested the growth and developmental effects of PFOS, PFOA, and GenX, on gray treefrog (Hyla versicolor) tadpoles, followed by a Bd challenge in metamorphs. Our results demonstrate that a PFAS larval exposure interacted witha terrestrial Bdchallenge to influence growth and development. Bdexposed animals were significantly shorter (smaller snout vent length)  and had a significant increase in body condition and mass. This is the first study to report effects on amphibian terrestrial life stages after larval exposure to PFAS and to report an increased sensitivity to Bd. The environmentally relevant concentrations tested in this study  (<10  parts  per  billion)  lend  ecological  significance  to  these  results  however,  additional studies are needed to understand the mechanisms behind these effects.</p>

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