Doctor of Philosophy (Ph.D.)
Virginia Institute of Marine Science
Robert J Latour
Mary C Fabrizio
Andrew M Scheld
Emily B Rivest
Olaf P Jensen
Climate change has altered marine environments, most notably by increasing water temperatures and reducing dissolved oxygen concentrations. These persistent changes have impacted the phenology and spatiotemporal habitat usage of mobile species, often through distributional shifts poleward or to deeper water. Climate-driven distributional shifts have been documented for numerous species inhabiting the Atlantic Ocean along the US East Coast, a region disproportionately affected by climate change. Adjacent estuaries are experiencing similar alterations to their physical environments and biotic community composition. Many estuarine species are seasonal residents and changes to environmental conditions within an estuary can result in altered usage and residence times. The Chesapeake Bay is one such estuary experiencing these climate-associated effects. The bay serves as an important habitat for a diverse array of seasonally resident marine and estuarine taxa, providing valuable foraging, refuge, and spawning grounds. Concurrent with physical changes, survey data have indicated decreases in relative abundance of many finfishes. However, environmental drivers associated with these declines have not been fully quantified. To evaluate the role of climate change on spatiotemporal habitat usage of Chesapeake Bay fauna, state-of-the-art statistical models were applied to several long-term monitoring data sets. Changes in Chesapeake Bay inhabitance by a suite of seasonally resident species were explored by evaluating estuarine-coastal ocean exchange and comparing the patterns to a more northern estuary, Delaware Bay. Relative habitat utilization of Chesapeake Bay declined for most species, while utilization patterns for Delaware Bay were largely constant or increasing over time. Broad-scale, multispecies analyses of relative habitat utilization time series revealed that the North Atlantic Oscillation, a signal of long-term warming, was an important driver of Chesapeake Bay exchange. Baseline habitat associations for several seasonal resident species in Chesapeake Bay were quantified through the development of ecological niche models. Model output indicated that impacts of climate change on environmental conditions of the bay, including continued increases in temperature and hypoxic volume, will likely exacerbate the decline in relative abundance. The niche envelopes were paired with an estuarine-carbon-biogeochemical regional ocean model to derive estimates of habitat suitability. The temporal patterns in habitat suitability did not match abundance trends, indicating that dynamics outside of the physical conditions of Chesapeake Bay are likely driving the decreased utilization of this estuary. Finally, the traditional mark-recapture modeling framework that includes catch-and-release fishing was extended to a subannual, multi-stock, spatially and temporally explicit version that allowed for simultaneous estimation of key parameters, including mortality rates and occupancy probabilities. Model estimated instantaneous natural mortality increased over time within Chesapeake Bay, particularly for older fish, but has not changed appreciably outside of the estuary, supporting previous findings of increased disease-associated mortality with age, and a possible role of climate change-associated suboptimal environmental conditions. Estimated occupancy probabilities exhibited differences in likelihood of estuarine inhabitance based on age, season, and producer region. Collectively, the results demonstrate heterogeneous changes in spatiotemporal habitat use of several Mid-Atlantic species on various scales. This information can be used by managers tasked with temporally and spatially dynamic policy development in a changing environment.
© The Author
Schonfeld, Adena Jade, "Climate Impacts On Spatiotemporal Habitat Usage Of Mid-Atlantic Fishes" (2023). Dissertations, Theses, and Masters Projects. William & Mary. Paper 1686662915.
Available for download on Thursday, May 09, 2024