Spatial variation and antecedent sea surface temperature conditions influence Hawaiian intertidal community structure

Abstract

Global sea surface temperatures (SSTs) are increasing, and in Hawaiʻi, rates of ocean warming are projected to double by the end of the 21st century. However, current nearshore warming trends and their possible impacts on intertidal communities are not well understood. This study represents the first investigation into the possible effects of rising SST on intertidal algal and invertebrate communities across the Main Hawaiian Islands (MHI). By utilizing citizen-science data coupled with high-resolution, daily SST satellite measurements from 12 intertidal sites across the MHI from 2004–2019, the response of intertidal algal and invertebrate abundance and community diversity to changes in SST was investigated across multiple spatial scales. Results show high rates of SST warming (0.40°C Decade-1) over this study’s timeframe, similar to predicted rates of warming for Hawaiʻi by the end of the 21st century. Changes in abundance and diversity in response to SST were variable among intertidal sites, but differences in antecedent SST among intertidal sites were significantly associated with community dissimilarity. In addition, a statistically significant positive relationship was found between SST and Simpson’s diversity index, and a significant relationship was also found between SST and the abundance of six dominant taxa. For five of these six dominant taxa, antecedent SSTs over the 6–12 months preceding sampling were the most influential for describing changes to abundance. The increase in community diversity in response to higher SSTs was best explained by temperatures in the 10 months preceding sampling, and the resultant decreased abundance of dominant turf algae. These results highlight rapidly warming nearshore SSTs in Hawaiʻi and the longer-term effects of antecedent SSTs as significant drivers of change within Hawaiian intertidal communities. Therefore, we suggest that future research and management should consider the possibility of lagging effects of antecedent SST on intertidal communities in Hawaiʻi and elsewhere.

Records of the non‐native alga Acanthophora spicifera (Rhodophyta) and their colonial epibionts in La Paz Bay, Gulf of California

“… spicifera to monitor the ecological progress of the expansion process, understand the environmental preferences at annual and interannual scales and, finally, the epiphytes’ role in La Paz Bay biodiversity. Considering that the SST has been an explanatory variable in the response to its non-native distribution in the Pacific Ocean ( Camacho and Houk 2020 , Chávez-Sánchez et al 2022 , Ward et al 2023 ), as well as the presence of precipitation that favours its distribution in both native Atlantic ( Kilar and McLachlan 1986 ) and non-native Pacific areas ( Camacho and Houk 2020 ), which it is limited by the aridity of La Paz Bay ( Obeso-Nieblas et al 2004 ), however, could be compensated by anthropogenic nutrient inputs in the area and the high capacity of this macroalgae to absorb nutrients ( Dulai et al 2021 ).…”