# Autumnal deep scattering layer from moored acoustic sensing in the subtropical Canary Basin

## TL;DR

This study reports a seasonal deep scattering layer in the NE-Atlantic's bathypelagic zone, likely composed of zooplankton or similar organisms, showing slow vertical movement and reduced diel migration during autumn.

## Contribution

It provides new insights into deep scattering layers' seasonal presence, composition, and behavior in the subtropical Atlantic, using moored acoustic sensing.

## Key findings

- Deep scattering layer observed at 1650 m depth during autumn.
- Layer exhibits slow vertical movement of 2-5 m per day.
- Diel vertical migration is significantly reduced during the layer's presence.

## Abstract

An enhanced acoustic scatterer reflectance layer was observed in the bathypelagic zone around 1650 m in the subtropical NE-Atlantic Ocean for about two months during autumn. It resembles a classic pattern of diapause-resting, possibly of large zooplankton, shrimp and/or Cyclothone, at great depths well below any sunlight penetration, which is more commonly found at higher latitudes. The observed slow sink and rise of about 2-5 m per day into and out of this deep layer is considerably slower than the more than 1000 m per day of diel vertical migration (DVM). During the two-month period of deep scattering, DVM is observed to be greatly reduced.

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Source: https://tomesphere.com/paper/1903.01285