Species range movement due to changing ocean conditions is occurring around the world. As species move, they build new interaction networks as they shift from or into new ecological communities. Typically, species ranges are modeled individually, but biotic interactions have been shown to be important to creating more realistic modeling outputs for species. Kelp forests are known to be one of the most productive ecosystems in the world. To understand the importance of consumer interactions in Eastern Pacific kelp forest species distributions, I used a Maxent framework to model a key foundation species, giant kelp (Macrocystis pyrifera), and a dominant herbivore, purple sea urchins (Strongylocentrotus purpuratus). With neither species having previously been modeled in the Eastern Pacific, I found evidence for M. pyrifera expansion in the northern section of its range, with no projected contraction at the southern range edge. Despite its known co-occurrence with M. pyrifera, models of S. purpuratus showed a non-concurrent southern range contraction and a co-occurring northern range expansion. While the co-occurring movement may lead to increased spatial competition for suitable substrate, this non-concurrent contraction could result in community wide impacts such as herbivore release, tropicalization, or ecosystem restructuring. When looking at species distributions, an aspect that is often overlooked is species abundance. Drops in species abundance could lead to a species being functionally extinct while still being labeled as present in presence/absence distribution maps. Alternatively, rises in abundance could lead to trophic imbalance without being labeled as an area undergoing change. To understand how species abundance might change in Eastern Pacific kelp forests, I used a Generalized Additive Model framework to understand the relationship between abundance and environmental conditions for a suite of echinoderm species representing a variety functional groups. I then created a series of abundance based distribution models across climate change scenarios using these relationships. These models provide further clarity to how ocean warming may impact several ecologically important marine species as well as giving us a better understanding of where communities may be more vulnerable to restructuring due to altered abundance patterns. In addition to range movement, thermal stress is also expected to alter interaction strength. Thermal anomalies occur in both short-term heatwaves and long-term increases to annual mean temperatures. In ectothermic organisms, increased temperatures should directly increase organism metabolism, but studies looking at metabolic change after heatwaves have shown conflicting results to long-term climate change studies leaving questions as to how species will be impacted on short-term and long-term scales. In eastern Pacific kelp forests, red sea urchins (Mesocentrotus franciscanus) and purple sea urchins (Strongylocentrotus purpuratus) are the dominant kelp forest herbivores consuming kelp from Baja California to Alaska. I tested the hypothesis that moderate experimental warming would increase herbivory rates over time, with a more pronounced increase occurring during long-term warming in comparison to simulated short-term heatwaves. After simulating both short-term and long-term warming events I found that feeding rates and thermal maxima varied by species and the length of warming event. While short-term heatwave events showed no increase in herbivory rates, longer-term warming led to increased herbivory in both species. Purple urchins demonstrated a lower thermal maximum than red urchins despite purple urchins being generally more thermally tolerant. This study provides valuable insights into the differences in species interaction strength under varying global change scenarios highlighting variation in physiological response to the same thermal stress imposed at different timescales. Integration of these studies allows us to create more holistic predictions about ecosystem wide change—providing information not just on changes to organisms’ biogeographic range but also how interactions and trophic dynamics may change within that range. / Biology

<div>Biodiversity loss is the silent crisis of the 21st century. Human activities are drastically altering the diversity of life on Earth, yet the extent of this transformation is shrouded by our limited information on biodiversity and how it is changing. Emerging technologies may be suited to fill this information gap, and as a result increase our capacity to measure and manage natural systems. Acoustic monitoring is a remote sensing technique that is rapidly reshaping the temporal and spatial scales with which we can assess animal biodiversity. Through recording and analyzing soundscapes—the collection of sounds occurring at a given place and time—we can assess biodiversity, habitat condition, and environmental change. However, the relationships between soundscapes and these three ecological dimensions are still in the early phases of categorization, especially in aquatic systems. </div><div><br></div><div>This dissertation investigates how soundscapes can be used to measure biodiversity, habitat condition, and environmental change in aquatic habitats. It addresses several knowledge gaps: First, I develop a framework for classifying unknown sounds within a soundscape, which I use to measure the acoustic diversity and dynamics within a tropical freshwater wetland. Second, I demonstrate that soundscapes can reflect the resilience of animal communities following disturbance events. Altered soundscapes revealed that Hurricane Maria, which swept through Puerto Rico in September 2017, impacted dry forest animal communities more than adjacent coral reef communities. Third, in kelp forest habitats off the coast of California, USA, I showed that soundscape variables correlated with ecological variables associated with regime shift in kelp forests, including urchin density, kelp cover, and fish diversity. Overall, this dissertation demonstrates that soundscape recording and analysis is a promising way to assess the ecological conditions of aquatic systems. </div>