Context‐dependent carryover effects of hypoxia and warming in a coastal ecosystem engineer

Feb 26, 2021Ecological applications : a publication of the Ecological Society of America

How Low Oxygen and Warming Together Affect a Coastal Ecosystem Engineer

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Abstract

Early life exposure to diel-cycling hypoxia and warming significantly affects oyster growth when re-exposed to these stressors later.

Oysters exposed to hypoxia and warming in early life showed strong changes in energy allocation that influenced their growth.
The effects of early stress exposure were only observed when oysters encountered the same stressors again two months later.
Re-exposure to hypoxia and warming later in life also affected oyster tissue and shell growth.
These findings suggest that previous environmental stressors can shape organisms' responses to current conditions.
Context-dependent may impact the fitness and restoration of important species like oysters.

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Organisms are increasingly likely to be exposed to multiple stressors repeatedly across ontogeny as climate change and other anthropogenic stressors intensify. Early life stages can be particularly sensitive to environmental stress, such that experiences early in life can "carry over" to have long-term effects on organism fitness. Despite the potential importance of these within-generation , we have little understanding of how they vary across ecological contexts, particularly when organisms are re-exposed to the same stressors later in life. In coastal marine systems, anthropogenic nutrients and warming water temperatures are reducing average dissolved oxygen (DO) concentrations while also increasing the severity of naturally occurring daily fluctuations in DO. Combined effects of warming and diel-cycling DO can strongly affect the fitness and survival of coastal organisms, including the eastern oyster (Crassostrea virginica), a critical ecosystem engineer and fishery species. However, whether early life exposure to hypoxia and warming affects oysters' subsequent response to these stressors is unknown. Using a multiphase laboratory experiment, we explored how early life exposure to diel-cycling hypoxia and warming affected oyster growth when oysters were exposed to these same stressors 8 weeks later. We found strong, interactive effects of early life exposure to diel-cycling hypoxia and warming on oyster tissue : shell growth, and these effects were context-dependent, only manifesting when oysters were exposed to these stressors again two months later. This change in energy allocation based on early life stress exposure may have important impacts on oyster fitness. Exposure to hypoxia and warming also influenced oyster tissue and shell growth, but only later in life. Our results show that organisms' responses to current stress can be strongly shaped by their previous stress exposure, and that context-dependent carryover effects may influence the fitness, production, and restoration of species of management concern, particularly for sessile species such as oysters.

Key numbers

59%

Increase in tissue growth

Tissue growth at warm vs. ambient temperatures during Phase 2.

106%

Context-dependent growth reduction

Reduction in tissue:shell growth when exposed to both stressors.

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Context‐dependent carryover effects of hypoxia and warming in a coastal ecosystem engineer

Abstract

Key numbers

Full Text

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