Temporal Changes in the Upper/Lower Limits of Fucus and Endocladia at Cattle Point, San Juan Island

Abstract

Increases in global and seawater temperatures are a rising concern for communities across the planet. Over the last 20 years, the scientific community has taken great interest in climate change, and attempted to analyze how species respond to its stressors. Analyzing heat resistant algal species, such as Fucus distichus and Endocladia muricata could provide insights into how the biota of the high intertidal are changing in response to a warming climate. Our study aims to observe how the Upper and Lower Limits (UL/LL) of these two species have changed between 1972 and 2023. Data was collected at Cattle Point, San Juan Isl., WA, in May 2023, and compared to a study done at the same site from 1972. Our data found that the Upper limits of these species has remained constant over time, while the lower limit of these species has risen in elevation. We were unable to produce an accurate proxy for heat stress. Because of this, correlations to heat stress and the changes observed over time in the UL/LL of Fucus and Endocladia are speculative, and will require more observations over time before significant correlations can be drawn. This study provides recommendations for continuing temporal observations at Cattle Point, San Juan Isl., WA, so that future studies may be able to draw statistically significant correlations between heat stress and changes in species distribution.