Deep-sea food bonanzas: early Cenozoic whale-fall communities resemble wood-fall rather than seep communities

Abstract

The evolutionary history of invertebrate communities utilizing whale carcasses and sunken wood in the deep-sea is explored using fossil evidence. Compared to modern whale-fall communities, the Eo-Oligocene examples lack those vent-type taxa that most heavily rely on sulphide produced by anaerobic breakdown of bone lipids, but are very similar in their trophic structure to contemporaneous wood-falls. This sheds doubt on the hypothesis that whale-falls were evolutionary stepping stones for taxa that now inhabit hydrothermal vents and seeps. We suggest that the whale-fall communities reported here represent a new ecologic stage among whale-falls, which we have coined the 'chemosymbiotic opportunist stage' and that the 'sulphophilic stage' of modern whale-falls developed during the Early Miocene, resulting from a significant increase in both body size and/or oil content of bones among cetaceans during this time.

Several deep-sea mussels and their associated symbionts are able to live both on wood and on whale falls

“…Numerous metazoan taxa are endemic to these ecosystems (Sibuet & Olu 1998;Van Dover 2000;Smith & Baco 2003;Rouse et al 2004), and recent evidence from fossil records suggests overlapping fauna compositions between these ecosystems at least since the Cretaceous period (Kiel & Goedert 2006).…”

A new Miocene deep-sea chiton and early evidence for Teredinidae-sustained wood-fall communities

“…Twenty-nine molluscs (excluding shipworms) were identified from 28 wood-fall communities from the Eocene to Oligocene, and a species attributed to Leptochiton was present in five of these communities (Kiel and Goedert, 2006a). Also, a single intermediate valve of an unidentified chiton was found in a wood-fall from the Eocene of the Lincoln Creek Formation in Washington State, USA (Kiel and Goedert, 2006b).…”

“…Proposals of ancient origins for deep-sea taxa should be treated cautiously, however, as well as the Palaeozoic origin of the specialization on wood substrates because their fossil record is not extensively known. In addition, Glaphurochiton was not found associated with fossil wood, but in black and dark shales assumed to be a palaeoenvironment rich in organic material (Kiel and Goedert, 2006a). The three families also have shell features that are generally interpreted as plesiomorphic so that it is difficult to pinpoint their origin in the fossil record.…”

Magnetostratigraphy and Tectonic Rotation of the Eocene-Oligocene Makah and Hoko River Formations, Northwest Washington, USA

“…Some of these fossils come from apparent chemosymbiotic communities [40][41][42], including communities that are apparently associated with decaying whale carcasses and sunken wood [22,[43][44][45].…”

“…However, many of the benthic foraminiferal zones are also very long and low in resolution. For example, the middle Eocene Narizian stage spans about 8 million years (39)(40)(41)(42)(43)(44)(45)(46)(47)(48), the late Eocene Refugian stage spans about 7 million years , and the Zemorrian stage spans most of the Oligocene [15]. In addition, benthic foraminifera also track paleobathymetric changes, and so some of the zonations based on benthic foraminifera have proven to be timetransgressive, especially between California and Washington [15,16].…”