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Establishing species biological thresholds of OA and multiple stressors

Dr. Emily Rivest

Virginia Institute of Marine Science

A. Devlin/VASG

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What is the definition of biological thresholds?

Waldbusser et al. Nat Clim Change 2015

Proportion normal development

Conditions of carbonate chemistry beyond which there is a change in a biological property:

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  • Survival
  • Growth
  • Reproduction
  • Physiological rates
  • Cellular properties

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OA thresholds* in eastern oysters

2 yo

6 mo

*Ωcalcite value where net calcification rate = 0

2yo: Ωcalcite = 1.34

6mo: Ωcalcite = 1.04

Statistically similar

Funded by NOAA OAP – OA Thresholds

Rivest et al., in prep

Calcification was the only parameter sensitive to the range of Ωcalcite tested

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Thresholds can differ by population, life stage, chemistry parameter

Page Rock reef: S=18

Parrot’s Rock reef: S=13

Larvae produced from oysters at lower salinity reef are more tolerant of low-pH conditions.

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The biological threshold for shell length would be at a lower pH for larvae from Parrot’s Rock reef than Page Rock.

Funded by Mid-Atlantic Sea Grants / NOAA OAP

Himes et al. 2024

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What is the definition of biological thresholds?

Waldbusser et al. Nat Clim Change 2015

Proportion normal development

Conditions of carbonate chemistry beyond which there is a change in a biological property:

​

  • Survival
  • Growth
  • Reproduction
  • Physiological rates
  • Cellular properties

To understand risks and vulnerabilities posed by OA, what should the definition be?

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What is the definition of biological thresholds?

Waldbusser et al. Nat Clim Change 2015

Proportion normal development

Significant change with respect to a baseline?

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Value relevant to user group, impact, or management action?

  • Different user groups have different sensitivities to change: Bottom line of shellfish hatchery, small vs. large

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  • Effects on predators vs. ecosystem services

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  • Catch restriction vs. site selection for restoration

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To understand risks and vulnerabilities posed by OA, what should the definition be?

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What is the value of biological thresholds?

  • Early detection / targets
  • Development of monitoring and mitigation plans
    • Simplifies monitoring – focus on carbonate chemistry and co-stressors

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Funded by NOAA OAP

Rivest et al., OA Thresholds

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What is the impact of biological thresholds?

  • How to interpret [current] monitoring dashboards

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M. Friedrichs, VIMS

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What is the impact of biological thresholds?

  • Predict exposure and consequences

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Funded by NOAA OAP - RVA

Rivest et al, in prep

50-Year Difference

Δ Shell Weight (g)

Funded by NOAA OAP - RVA

Czajka, Rivest et al, in prep

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What is the impact of biological thresholds?

  • How to interpret [current] monitoring dashboards

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M. Friedrichs, VIMS

  • Predict exposure and impacts

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  • Ideally, avoid negative outcomes
    • Take action!

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Takeaways on biological thresholds of OA

  • The definition matters! Co-production of definitions is essential for effective policy development and implementation.

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  • More multi-stressor work is critically needed. In situ validation is important.

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  • Thresholds should not replace, but should complement, co-monitoring of OA and its biological impacts.

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  • Thresholds are only practically useful if action is taken in response.

A. Devlin/VASG