Do continental shelves export organic matter?

Area of Science:

• Marine ecology
• Biogeochemical cycles
• Oceanography

Background:

• Coastal marine ecosystems may have unbalanced organic matter production and consumption.
• A hypothesis suggested 90% of spring phytoplankton bloom is exported, sequestering carbon on the continental slope.

Purpose of the Study:

• To test the hypothesis of significant organic carbon export from continental shelves.
• To investigate the balance of organic matter production and consumption in coastal marine environments.

Main Methods:

• Summarizing findings from the Shelf-Edge Exchange Processes (SEEP) experiment.
• Analyzing organic carbon budgets, sediment deposition, and biomass on the continental slope.

Main Results:

• The Shelf-Edge Exchange Processes (SEEP) experiment found no positive imbalance in the organic carbon budget.
• Sediment deposition and biomass on the continental slope were modest, not supporting large-scale export.
• A small fraction of continental shelf phytodetritus is exported; most is consumed on the shelf.

Conclusions:

• The hypothesis of 90% phytoplankton export is rejected.
• Pelagic microbial consumption and seasonal production-consumption lags are crucial factors in organic carbon cycling.
• Organic matter is primarily consumed within the continental shelf ecosystem.