Coupled changes in pH, temperature, and dissolved oxygen impact the physiology and ecology of herbivorous kelp forest grazers

Publication Date

5-1-2022

Document Type

Article

Publication Title

Global Change Biology

Volume

28

Issue

9

DOI

10.1111/gcb.16125

First Page

3023

Last Page

3039

Abstract

Understanding species’ responses to upwelling may be especially important in light of ongoing environmental change. Upwelling frequency and intensity are expected to increase in the future, while ocean acidification and deoxygenation are expected to decrease the pH and dissolved oxygen (DO) of upwelled waters. However, the acute effects of a single upwelling event and the integrated effects of multiple upwelling events on marine organisms are poorly understood. Here, we use in situ measurements of pH, temperature, and DO to characterize the covariance of environmental conditions within upwelling-dominated kelp forest ecosystems. We then test the effects of acute (0–3 days) and chronic (1–3 months) upwelling on the performance of two species of kelp forest grazers, the echinoderm, Mesocentrotus franciscanus, and the gastropod, Promartynia pulligo. We exposed organisms to static conditions in a regression design to determine the shape of the relationship between upwelling and performance and provide insights into the potential effects in a variable environment. We found that respiration, grazing, growth, and net calcification decline linearly with increasing upwelling intensity for M. francicanus over both acute and chronic timescales. Promartynia pulligo exhibited decreased respiration, grazing, and net calcification with increased upwelling intensity after chronic exposure, but we did not detect an effect over acute timescales or on growth after chronic exposure. Given the highly correlated nature of pH, temperature, and DO in the California Current, our results suggest the relationship between upwelling intensity and growth in the 3-month trial could potentially be used to estimate growth integrated over long-term dynamic oceanographic conditions for M. franciscanus. Together, these results indicate current exposure to upwelling may reduce species performance and predicted future increases in upwelling frequency and intensity could affect ecosystem function by modifying the ecological roles of key species.

Funding Number

EF‐1416919

Funding Sponsor

National Science Foundation

Keywords

energetics, grazers, kelp forests, physiology, upwelling, variability

Department

Moss Landing Marine Laboratories

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