Light penetration structures the deep acoustic scattering layers in the global ocean

Area of Science:

• Marine Ecology
• Biological Oceanography
• Acoustic Oceanography

Background:

• The deep scattering layer (DSL) is a major pelagic ecosystem feature formed by mesopelagic organisms.
• DSL organisms are crucial for marine food webs and the biological carbon pump.
• Daily vertical migration patterns of DSL organisms influence carbon transport.

Purpose of the Study:

• To investigate the factors governing the daytime depth of the deep scattering layer (DSL).
• To understand the relationship between DSL depth, light penetration, and oxygen levels.
• To explain the observed correlation between shallow DSL distribution and hypoxic waters.

Main Methods:

• Analysis of deep scattering layer (DSL) daytime depth data from the Malaspina 2010 Circumnavigation Expedition.
• Correlation analysis between DSL depth, light penetration (optical depth), and dissolved oxygen concentrations.
• Examination of global oceanographic data to identify patterns in DSL distribution.

Main Results:

• DSL daytime depth variability is primarily governed by variations in light penetration across the global ocean.
• DSL depth distribution conforms to a consistent optical depth layer.
• A correlation between dissolved oxygen and light penetration explains the association of shallow DSL with hypoxic waters.

Conclusions:

• Light penetration is the key factor determining deep scattering layer (DSL) daytime depth.
• Understanding DSL dynamics is crucial for predicting ocean carbon cycling and food web interactions.
• This research refines models of pelagic ecosystem structure and function.