Small copepods could channel missing carbon through metazoan predation

Area of Science:

• Marine ecology
• Biogeochemical cycles
• Climate change science

Background:

• Global ecosystem models struggle to accurately predict climate change impacts on marine systems.
• Current models often misrepresent small copepods (<2 mm) as solely feeding on phytoplankton and microzooplankton.
• This simplification leads to poor agreement between modeled and measured oceanic biogenic carbon fluxes.

Purpose of the Study:

• To investigate the extent of metazoan predation by small copepods in a North Atlantic upwelling region.
• To assess the impact of this previously unaccounted trophic pathway on marine biogeochemical models.
• To quantify the potential global carbon ingestion by small copepods through metazoan predation.

Main Methods:

• Collection and sorting of abundant small copepods (<2 mm) from a seasonal upwelling region.
• Application of a molecular gut content analysis to identify prey items.
• Evaluation under two distinct oceanographic conditions.
• Scaling of findings using published field and laboratory data.

Main Results:

• Small copepods engage in significant metazoan predation, a trophic pathway largely ignored in global models.
• Global ingestion estimates suggest small copepods consume 1.79–27.20 gigatons of carbon annually.
• This overlooked predation could increase estimates of marine biogeochemical fluxes by 15.6%–24.4% and affect export to higher trophic levels.
• It may also explain discrepancies between measured copepod ingestion and metabolic demands.

Conclusions:

• The inclusion of metazoan predation by small copepods is crucial for refining global ecosystem models.
• Accurate representation of copepod feeding behavior is essential for predicting climate change impacts on marine carbon cycling.
• This research highlights substantial implications for understanding ocean processes and the biological pump at a global scale.