Polyp loss and mass occurrence of sea urchins on bamboo corals in the deep sea: an indirect effect of fishing impact?

Pål Buhl‐Mortensen,Andreia Braga‐Henriques,Angela Stevenson

doi:10.1002/ecy.3564

Abstract

The ability of corals to detach their polyps (leaving behind a naked skeleton) in times of stress, allows polyps to escape from a local source of hostility (Sammarco 1982). In situ observations of this behavior (referred to as 'polyp bailout') were first documented in tropical reef-building corals. Later it was observed in some cold-water corals of Acanthogorgia (Braga-Henriques 2014), and Acanella arbuscula (Rakka et al. 2019) in aquaria.

Highlights

The ability of corals to detach their polyps in times of stress, allows polyps to escape from a local source of hostility (Sammarco 1982)
We describe massive tissue and polyp loss on bamboo corals Keratoisidinae photographed on Discovery seamount south west of Cape Town, South Africa (South East Atlantic Ocean) at 850-960m depth, and at 1135-1160m depth on Mongrel seamount off the coast of Tasmania, Australia (Southwest Pacific Ocean) (Fig. 1)
Naked bamboo coral populated by D. horridus and G. multidentatus were observed on Mongrel seamount in the ‘Huon’ area between 1135-1160m depth

Summary

Introduction

The ability of corals to detach their polyps (leaving behind a naked skeleton) in times of stress, allows polyps to escape from a local source of hostility (Sammarco 1982). Perched atop these naked colonies were large numbers of the deep-sea urchins (family Echinidae) Dermechinus horridus at Discovery and Mongrel seamounts and two instances of Gracilechinus multidentatus at Mongrel seamount. In 2019, R/V Dr Fridtjof Nansen surveyed 14 locations across five seamounts in the SEAFO (South East Atlantic Fisheries Organization) sub area D, at 400-1800 m depth with an ROV (Buhl-Mortensen et al 2020).

Results

Conclusion