Finding mesopelagic prey in a changing Southern Ocean.

Area of Science:

• Marine Ecology
• Oceanography
• Biogeochemical Processes

Background:

• Mesopelagic fish and squid are crucial for energy and carbon transfer in the ocean.
• Mapping their distribution in remote areas like the Southern Ocean is challenging.
• Understanding mesopelagic prey is vital for assessing ecosystem structure and predator impacts.

Purpose of the Study:

• To infer the vertical distribution and relative abundance of mesopelagic prey in the Southern Ocean.
• To investigate the influence of hydrographic processes on prey distribution.
• To project potential changes in prey distribution due to future ocean conditions.

Main Methods:

• Utilized 14 years of southern elephant seal tracking and dive data.
• Employed predator-derived indices to estimate mesopelagic prey distribution.
• Combined observational data with future projections of Southern Ocean conditions.

Main Results:

• Mesopelagic prey vertical migration is restricted, with higher abundance near the surface where Circumpolar Deep Water upwells.
• Physical hydrographic processes significantly influence prey vertical distribution.
• Future ocean conditions may lead to redistribution of mesopelagic prey, with increased abundance east of the Kerguelen Plateau and decreased abundance to the west.

Conclusions:

• Mesopelagic prey distribution is linked to oceanographic features, particularly upwelling zones.
• Projected changes in ocean conditions could alter prey availability for marine predators.
• These shifts in energy flow have implications for mesopelagic predators and the wider pelagic ecosystem.