Changes in vegetation may influence the quality and quantity of the underlying organic peat soils and have impacts on faunal populations. My goal was to determine whether shifts from native slough communities to invasive cattail in the Florida Everglades could affect peat characteristics that could cascade to impact the dry season survival of crayfish (Procambarus fallax). I contrasted peat soils from native slough and cattail-invaded sites as alternative dry-season burrowing substrates for crayfish. Cattail peat had higher average bulk density and inorganic content within the first ten centimeters of the soil profile. Crayfish showed marginally greater initial burrowing success in slough peat than in cattail peat but survival was equivalent in both peat soils and high overall. Understanding these indirect linkages between vegetation and crayfish populations in the Everglades can provide insight on the consequences of plant invasion on ecosystem trophic dynamics. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

Community ecology and conservation are complementary disciplines under the umbrella of ecology, providing insight into the factors that determine where and how communities exist, and informing efforts aimed at sustaining the diversity and persistence of the organisms that comprise them. Conservation ecologists apply the principles of ecology and other disciplines, to the maintenance of biodiversity. This thesis uses this approach to assess the status of freshwater crayfish in south-central Ontario and investigate potential anthropogenic drivers of crayfish community change. I start with a temporal analysis of crayfish relative abundance over a period of 18 years and find that all species have experienced significant population declines across the sampled range, resulting in reduced species distributions and crayfish community diversity. Next I employ multivariate statistical techniques to relate changes in crayfish communities between the two time periods to ecological and anthropogenic changes. I identify a number of threats in the region that are correlated with crayfish decline and are likely to pose a threat to aquatic ecosystems more broadly in the region, including calcium (Ca) decline, metal pollution, human development, and species introductions. In the latter two chapters I look more closely at Ca decline as a mechanism driving crayfish declines. First, laboratory analysis of the effect of Ca availability on juvenile Orconectes virilis (a Shield native) reveals that survival is significantly reduced below 0.5-0.9 mg·L-1, which is one of the lowest ever reported Ca requirement thresholds for a crustacean. Second, a correlative study using adult inter-moult crayfish collected from lakes that range broadly in their Ca concentrations, indicates that for O. virilis, carapace Ca content is significantly related to lake Ca concentration, and is under-saturating below 8 mg·L-1. This collective body of work identifies significant anthropogenic threats to crayfish and their aquatic ecosystems in south-central Ontario.

Community ecology and conservation are complementary disciplines under the umbrella of ecology, providing insight into the factors that determine where and how communities exist, and informing efforts aimed at sustaining the diversity and persistence of the organisms that comprise them. Conservation ecologists apply the principles of ecology and other disciplines, to the maintenance of biodiversity. This thesis uses this approach to assess the status of freshwater crayfish in south-central Ontario and investigate potential anthropogenic drivers of crayfish community change. I start with a temporal analysis of crayfish relative abundance over a period of 18 years and find that all species have experienced significant population declines across the sampled range, resulting in reduced species distributions and crayfish community diversity. Next I employ multivariate statistical techniques to relate changes in crayfish communities between the two time periods to ecological and anthropogenic changes. I identify a number of threats in the region that are correlated with crayfish decline and are likely to pose a threat to aquatic ecosystems more broadly in the region, including calcium (Ca) decline, metal pollution, human development, and species introductions. In the latter two chapters I look more closely at Ca decline as a mechanism driving crayfish declines. First, laboratory analysis of the effect of Ca availability on juvenile Orconectes virilis (a Shield native) reveals that survival is significantly reduced below 0.5-0.9 mg·L-1, which is one of the lowest ever reported Ca requirement thresholds for a crustacean. Second, a correlative study using adult inter-moult crayfish collected from lakes that range broadly in their Ca concentrations, indicates that for O. virilis, carapace Ca content is significantly related to lake Ca concentration, and is under-saturating below 8 mg·L-1. This collective body of work identifies significant anthropogenic threats to crayfish and their aquatic ecosystems in south-central Ontario.