High species richness in deep-sea chemoautotrophic whale skeleton communities

Abstract

While biodiversity in deep-sea soft sediments appears to be high, little is known about diversity levels on deep-sea hard substrates. To determine the contribution of potentially abundant whale-skeleton habitats to deep-sea biodiversity, we compare the local macrofaunal species richness and composition on 3 sulfide-rich whale skeletons to assemblages from vents, seeps, and other deepsea hard substrates. Based on rarefaction curves, whale skeleton diversity is higher than diversity in any other deep-sea hard substrate habitat. The average local species richness (185 spp.) on single chemoautotrophic whale skeletons approaches known levels of global cold-seep macrofaunal species richness (229 spp.), and exceeds the richness of the most speciose vent field known (121 spp.). Species richness on the whale skeletons is also substantially higher than on other deep-sea nonreducing hard substrates, such as manganese nodules and rocks. Richness levels approach those in deep-sea soft sediments and exceed some shallow-water hard substrates. This high species richness may be explained by unusually high trophic diversity on whale bones due to the presence of sulphophiles, generalized organic-enrichment respondents, whale-bone consumers, and background hard-substrate fauna such as suspension and deposit feeders. High species richness levels on whale skeletons and deep-sea sponge stalks suggest deep-sea hard substrates may harbor higher levels of diversity than previously recognized.