Fluctuating thermal environments of shallow-water rocky reefs in the Gulf of California, Mexico

Grantly R Galland,Philip A Hastings,James J Leichter

doi:10.1038/s41598-019-53730-0

Grantly R Galland, Philip A Hastings + Show 1 more

Open Access

https://doi.org/10.1038/s41598-019-53730-0

Copy DOI

Abstract

As part of a broad-scale study of the biogeography of rocky reefs in the Gulf of California, Mexico (GOC), we collected a continuous 1-yr temperature time series at ~5 m water depth at 16 sites spanning 5° of latitude and ~700 km along the western boundary of the basin. Throughout the region, thermal conditions were most variable in summer with fluctuations concentrated at diurnal and semi-diurnal frequencies, likely associated with solar and wind forcing and vertical water column oscillations forced by internal waves. Temperatures in winter were less variable than in summer, and minimum temperatures also differed among sites. Thermal variability integrated across the diurnal and semi-diurnal frequency bands was greatest near the Midriff Islands in the northern GOC and decreased toward the southern sites. Diurnal variability was greater than semi-diurnal variability at 13 of the 16 sites. A statistic-of-extremes analysis indicated shortest return times for cooling events in summer, and reef organisms at many of the sites may experience anomalous 2 to 5 °C cooling events multiple times per month. The significant extent of local temperature variability may play important roles in limiting species occurrences among sites across this biogeographic region.

Highlights

There is growing recognition that changes in oceanographic conditions, on biologically relevant spatial and temporal scales, are important drivers of marine community ecology, and the term ‘ocean weather’ has been used to describe this high-frequency environmental variability[1]
The Gulf of California (GOC), is a long (~1100 km) and relatively narrow (~150 km) semi-enclosed sea (Fig. 1) known for strong wind forcing, high solar insolation, and dynamic oceanographic conditions resulting from the shape, climate, and geology of the basin[10]
Environmental conditions in the GOC are strongly influenced by climate-scale variability, especially the El Nino Southern Oscillation (ENSO) which exerts a range of biological responses in shallow-water marine communities[21], and longer-term changes in climate detected at centennial scales[22]

Summary

Introduction

There is growing recognition that changes in oceanographic conditions, on biologically relevant spatial and temporal scales, are important drivers of marine community ecology, and the term ‘ocean weather’ has been used to describe this high-frequency environmental variability[1]. In situ measurement of environmental variability, of temperature, is important for ecologists seeking to understand drivers of marine community composition and to project the influences of changing oceanographic climate on marine communities These issues are especially relevant for regions near biogeographic transition, such as the boundary between tropical and temperate areas. Shallow water organisms inhabiting rocky reefs in the GOC are likely to experience variable and fluctuating physical environments, depending on location and complex interactions between local and regional upwelling, surface flow from the Pacific, solar heating, and internal waves. Recurring cooling events may be of physiological and ecological importance for rocky reef organisms, and characterizing site-specific and seasonal thermal variability across a large spatial scale is valuable for considering potential biological adaptation to the heterogeneous physical environments across the region

Objectives

Methods

Conclusion