Carbon Export Service of Commercially Important Fish

Responsible: Jesper Negård

E-mail: jespernn@student.ibv.uio.no

Supervisors: Olli Hyvarinen and Alexander Eiler

Aim

The aim of this master`s project is to characterize the carbon export potential of commercially important fish species in the Oslofjord, and investigate how species identity and body size influence this potential. By measuring both sinking and dissolution rates of fecal material, the project will give insight into the carbon export service.

Background

Natural Climate Solutions are strategies, such as conservation, restoration, and management, that intend to reduce the emission of greenhouse gases or increase the biological sequestration of CO₂ (Griscom et al., 2017). These methods are vulnerable against human- and climate-exacerbated disturbances, as the increased activity in the Anthropocene are damaging and reducing ecosystems responsible for carbon sequestration.

Recently the importance of animals in the regulation of carbon sequestering has become of more focus, with fish having potentially significant contributions. Previous studies suggest that fish contribute up to 1.5 Pg C y^-1, on average 16.1% (± 13%) of total carbon flux out of the euphotic zone (Saba et al., 2021), a recognizable amount compared to that of zooplankton contributions (6.5 Pg C y^-1).

Factors including fish abundance, size and diversity of fish influence the potential of the carbon export service. Fishing activities over the last few decades have depleted several fish populations and witnessed a reduction in average individual body size. This phenomenon, called “fishing down the food web” targets large-bodied individuals first, then moving to progressively smaller and smaller-sized fish species (Strecker et al., 2023). The characterization across species identity and size class will evaluate the impact of this practice on this fish carbon export service, estimating how this phenomenon influences sinking and dissolution rates. Recent studies (Saba et al., 2012 and Martin et al., 2021) highlight the lack of empirical data to quantify the carbon export service of marine fish, particularly those that are most heavily exploited by commercial fisheries.

Research questions

1. How do species identity and body size influence the carbon export potential of fish (including fecal sinking and dissolution rates)?
2. How does the feces sampling method influence observed sinking and dissolution rates?
3. How will seasonality, including temperature (summer and winter sampling) influence the sinking rates?