Date of Award

Winter 1-22-2025

Document Type

Thesis: Open Access

Degree Name

MS Marine Science

Department

Environmental and Ocean Sciences

Committee Chair

Drew Talley

Committee Member

Keith Lombardo

Committee Member

Zhi-Yong Yin

Abstract

The rocky intertidal ecosystem, the coastal area between high and low tides, serves as a critical buffer between land and sea. This ecosystem supports a diverse array of species and provides rich opportunities for exploration and education. With the influence of climate change, this ecosystem faces significant shifts in species distribution, resilience and recovery from environmental disturbances, as well as habitat loss (Jackson & McIlvenny 2011; Jueterbock et al. 2013; Menge & Gravem 2022; Rilov et al. 2021; Sagarin & Barry 1999). Between 2014-2016, climate anomalies El Niño (ENSO) and the Pacific Decadal Oscillation (PDO) combined to create a period of extreme ocean warming, called the Pacific Marine Heatwave or “The Blob” (Gentemann et al. 2017). The Pacific Marine Heatwave has been documented to have impacted marine ecosystems through mass mortality events, changes in community structure, and poleward expansion of species (Piatt et al. 2020). As sea surface temperature (SST) increases, shifts in species distribution result in ecological “winners” and “losers” based on thermal tolerances and competitive dynamics. This study reveals periods of increased ocean warming influenced by the Pacific Marine Heatwave may have resulted in both “winners” and “losers” in rocky intertidal community structure along the San Diego, California coastline. Understanding how rocky intertidal community structure transformed under the pressures of the Pacific Marine Heatwave may help to predict how increasing SST will continue to impact rocky intertidal ecosystems. Specifically, this study examines 1) spatial and temporal patterns within rocky intertidal community structure in relation to SST change, and 2) the ecological implications of these patterns. Data collected by the Multi-Agency Rocky Intertidal Network (MARINe) revealed site-specific community responses to increasing SST. Rocky intertidal “losers” were Silvetia compressa, red algae, Mytilus, and Pollicipes polymerus, as their species abundance 11 decreased with increasing SST. In contrast, the “winners” in this study were brown algae, green algae, and Tetraclita rubescens. Declines in abundance, potentially triggered by warming waters, may facilitate community change, where decreases in certain species leaves behind bare substrate, allowing space for opportunistic species to colonize. These findings highlight not only current changes in intertidal community structure in response to changes in SST as a result of the Pacific Marine Heatwave, but also provide insights into potential future shifts as ocean waters continue to warm. Understanding these changes is crucial for guiding conservation efforts in San Diego’s rocky intertidal ecosystems. Further research is needed to disentangle the interplay between climate change and local environmental factors.

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