Applied taphonomy of gorgonian and antipatharian corals in Atlantic Canada: experimental decay rates, field observations, and implications for assessing fisheries damage to deep-sea coral habitats

Abstract

Taphonomic degradation of cold-water gorgonian and antipatharian corals may affect the record of dead or broken corals remaining on the sea floor after damage by deep-sea fisheries. A taphonomic experiment on skeletal degradation of four species of gorgonians and one antipatharian was run in aquaria for 14 months. Paragorgia arborea skeletal fragments, composed of spongy proteins and calcite spicules, were completely degraded within 14 months. Protein-skeletons of Paramuricea and antipatharian fragments gained 10-20% wet weight through hydration of their proteinaceous skeletons. Calcitic gorgonian skeletons of Primnoa resedaeformis and Keratoisis grayi experienced no significant weight change during the experiment. Field observations of dead dislodged and dead skeletons corroborated experimental results. Dislodged and dying P. arborea skeletons were rigid in their live parts, but friable and fragile in their dead parts. Subfossil calcareous gorgonian skeletons up to 2000 years in age have been recovered from the sea floor by trawl bycatch or ROV. Documenting fisheries damage to gorgonian coral forests on the sea floor requires observation within a few months after the fisheries impacts.