DIREKT: Direct Effects of ocean alKalinity enhancement on early life history stages of herring
Purpose and justification:
The experiment will test the direct effects of ocean alkalinity enhancement (OAE) as a proposed CO2- removal-method with the aim of documenting a method countering negative effects of ocean acidification (OA) on survival, growth, development, physiology and behavior of herring eggs and larvae.
Distress: The effect of OAE is an emerging field, and this experiment will be the first study to look at the effect of OAE on fish eggs and larvae. Based on the expected OAE-induced changes in carbonate chemistry and increase in pH, the direct effects will be minimal, and as such the severity is deemed justified.
Expected benefits:
Given a scientific documentation of non-deleterious effects of OAE, this may provide the a way forward in mitigating local negative effects of OA.
Numbers of animals and what kind:
Offspring of spring-spawning herring (Clupea harengus) will be incubated in the laboratory. Three different setups will be conducted and totally 10800 larvae will be used.
- Setup 1: direct effects of enhanced alkalinity on egg development, survival and metabolism under three treatments (ambient, ΔTA 1200 and ΔTA 2400), each with 4 replicate tanks. An initial number of 600 eggs per replicate tank will be used. Eggs will be observed daily for development and survival rates (no sampling needed), and metabolic rates will be estimated several times throughout the experiment.
- Setup 2. direct effects of enhanced alkalinity on larval growth and other traits. In this case, a long-term rearing experiment will be performed lasting until 50 days post-hatch. Newly hatched larvae will be individually counted and transferred to the rearing containers (two treatments: ambient and ΔTA 2400, each with 3 replicate tanks). A total of 1800 larvae will be introduced on each tank. Larvae will be monitored for growth, survival, deformities, metabolic rates, biochemical condition (RNA:DNA, lipids) and swimming behavior.
- Set up 3: indirect effects of enhanced alkalinity on larval growth. Here two tanks with ambient conditions will be set up to rear larval herring for the mesocosms experiment at Espegrend Research Station. Larvae will be transported there and introduced in the mesocosms when they are around 10-12 mm (2-3 weeks).
How to adhere to 3R:
In the lab, negative effects of extreme ocean acidification (OA) (>1800 μatm pCO2) have been measured on growth and survival in herring, but not on alteration of swimming or feeding behavior. The target species is Atlantic herring and thus no replacement is possible. The number of experimental animals has carefully been reduced to the minimum needed to observe an effect on the different measured traits.
This will be a cooperation between GEOMAR, Kiel, University of Bergen and University of Agder. Researchers from the team have previously worked together in other laboratory and mesocosm experiments. Previous experiments have been investigating the effect of ocean acidification (opposite effect on pH in comparison to OAE) on herring larvae of local herring populations in the lab (direct effects) and in the KOSMOS mesocosms (direct effect + indirect effect via food web).
The experiment will test the direct effects of ocean alkalinity enhancement (OAE) as a proposed CO2- removal-method with the aim of documenting a method countering negative effects of ocean acidification (OA) on survival, growth, development, physiology and behavior of herring eggs and larvae.
Distress: The effect of OAE is an emerging field, and this experiment will be the first study to look at the effect of OAE on fish eggs and larvae. Based on the expected OAE-induced changes in carbonate chemistry and increase in pH, the direct effects will be minimal, and as such the severity is deemed justified.
Expected benefits:
Given a scientific documentation of non-deleterious effects of OAE, this may provide the a way forward in mitigating local negative effects of OA.
Numbers of animals and what kind:
Offspring of spring-spawning herring (Clupea harengus) will be incubated in the laboratory. Three different setups will be conducted and totally 10800 larvae will be used.
- Setup 1: direct effects of enhanced alkalinity on egg development, survival and metabolism under three treatments (ambient, ΔTA 1200 and ΔTA 2400), each with 4 replicate tanks. An initial number of 600 eggs per replicate tank will be used. Eggs will be observed daily for development and survival rates (no sampling needed), and metabolic rates will be estimated several times throughout the experiment.
- Setup 2. direct effects of enhanced alkalinity on larval growth and other traits. In this case, a long-term rearing experiment will be performed lasting until 50 days post-hatch. Newly hatched larvae will be individually counted and transferred to the rearing containers (two treatments: ambient and ΔTA 2400, each with 3 replicate tanks). A total of 1800 larvae will be introduced on each tank. Larvae will be monitored for growth, survival, deformities, metabolic rates, biochemical condition (RNA:DNA, lipids) and swimming behavior.
- Set up 3: indirect effects of enhanced alkalinity on larval growth. Here two tanks with ambient conditions will be set up to rear larval herring for the mesocosms experiment at Espegrend Research Station. Larvae will be transported there and introduced in the mesocosms when they are around 10-12 mm (2-3 weeks).
How to adhere to 3R:
In the lab, negative effects of extreme ocean acidification (OA) (>1800 μatm pCO2) have been measured on growth and survival in herring, but not on alteration of swimming or feeding behavior. The target species is Atlantic herring and thus no replacement is possible. The number of experimental animals has carefully been reduced to the minimum needed to observe an effect on the different measured traits.
This will be a cooperation between GEOMAR, Kiel, University of Bergen and University of Agder. Researchers from the team have previously worked together in other laboratory and mesocosm experiments. Previous experiments have been investigating the effect of ocean acidification (opposite effect on pH in comparison to OAE) on herring larvae of local herring populations in the lab (direct effects) and in the KOSMOS mesocosms (direct effect + indirect effect via food web).