Are abyssal scavenging amphipod assemblages linked to climate cycles?

Zoe Gutteridge,Rianna Vlierboom,Brian J Bett,Tammy Horton,Corinne A Pebody,Andrew R Gates,Michael H Thurston

doi:10.1016/j.pocean.2020.102318

Abstract

Scavenging amphipods are a numerically dominant and taxonomically diverse group that are key necrophages in deep-sea environments. They contribute to the detrital food web by scavenging large food-falls and provide a food source for other organisms, at bathyal and abyssal depths. Samples of this assemblage have been collected at the Porcupine Abyssal Plain Sustained Observatory (PAP-SO) in the North Atlantic (48°50′N 16°30′W, 4850 m) for >30 years. They were collected by means of baited traps between 1985 and 2016, covering a period of well-characterised changes in the upper ocean. From the 19 samples analysed, a total of 16 taxa were identified from 106,261 specimens. Four taxa, Abyssorchomene chevreuxi (Stebbing, 1906), Paralicella tenuipes Chevreux, 1908, P. caperesca Shulenberger & Barnard, 1976, and Eurythenes spp., dominated catches and were present in all samples.The dominant species varied in time with P. tenuipes typically dominant early in the time series (1985–1997) and its congener, P. caperesca, typically dominant later (2011–2016). Amphipod faunal composition exhibited a significant correlation with the Atlantic Multi-decadal Oscillation (AMO).Amphipod diversity was significantly lower in years with higher estimated volumetric particle flux at 3000 m. Species richness varied significantly between AMO phases, with higher values during ‘cool’ phase.Our results suggest a ‘regime shift’ in scavenging amphipod communities following a ‘regime shift’ in surface ocean conditions driven by a phase shift in Atlantic climate (from cool to warm AMO). This shift manifests itself in a remarkable change in dominant species, from obligate necrophages such as Paralicella spp., with semelparous reproduction to Abyssorchomene spp. which have a more varied diet and iteroparous reproduction, and are thus potentially more able to take advantage of greater or varied food availability from increased organic matter flux to the abyssal seafloor.

Highlights

Necrophagous amphipods are important components of the deepsea ecosystem owing to their contribution to the detrital food web through the scavenging of large food-falls (Thurston, 1990; Nygard et al, 2012; Havermans et al, 2013; Duffy et al, 2013)
Our results indicate that the dominant species of scavenging amphipod attracted to baited traps at the Porcupine Abyssal Plain Sustained Observatory changed over time
Our results indicate the existence of a possible ‘regime shift’ in scavenging amphipod communities following a ‘regime shift’ in surface ocean biological communities, which is driven by a phase shift in Atlantic climate

Summary

Introduction

Necrophagous amphipods are important components of the deepsea ecosystem owing to their contribution to the detrital food web through the scavenging of large food-falls (Thurston, 1990; Nygard et al, 2012; Havermans et al, 2013; Duffy et al, 2013). The importance of necrophagous amphipods in deep-sea food webs was not appreciated initially because of their rarity in benthic and suprabenthic trawl catches (Thurston, 1990; De Broyer et al, 2004). Traps were deployed as early as 1888 from the Hirondelle during an expedition of the Prince of Monaco, and between 1892 and 1912, 21 deployments of baited traps deeper than 3000 m were undertaken (Richard, 1934) After these early studies, it was not until the advent of more advanced technology, that the use of baited cameras revealed an active guild of mobile scavengers comprised largely of crustaceans and fish (Isaacs, 1969; Hessler et al, 1972). Baited traps are used commonly to study the necrophagous guild in the deep sea, but despite this, few studies have analysed replicate baited trap samples for species composition at depths greater than 2000 m, especially over extended time series

Methods

Results

Discussion

Conclusion