A Reverse Taxonomic Approach to Assess Macrofaunal Distribution Patterns in Abyssal Pacific Polymetallic Nodule Fields

Abstract

Heightened interest in the exploitation of deep seafloor minerals is raising questions on the consequences for the resident fauna. Assessing species ranges and determination of processes underlying current species distributions are prerequisites to conservation planning and predicting faunal responses to changing environmental conditions. The abyssal central Pacific nodule belt, located between the Clarion and Clipperton Fracture Zones (CCZ), is an area prospected for mining of polymetallic nodules. We examined variations in genetic diversity and broad-scale connectivity of isopods and polychaetes across the CCZ. Faunal assemblages were studied from two mining claims (the eastern German and French license areas) located 1300 km apart and influenced by different productivity regimes. Using a reverse taxonomy approach based on DNA barcoding, we tested to what extent distance and large-scale changes in environmental parameters lead to differentiation in two macrofaunal taxa exhibiting different functions and life-history patterns. A fragment of the mitochondrial gene Cytochrome Oxidase Subunit 1 (COI) was analyzed. At a 97% threshold the molecular operational taxonomic units (MOTUs) corresponded well to morphological species. Molecular analyses indicated high local and regional diversity mostly because of large numbers of singletons in the samples. Consequently, variation in composition of genotypic clusters between sites was exceedingly large partly due to paucity of deep-sea sampling and faunal patchiness. A higher proportion of wide-ranging species in polychaetes was contrasted with mostly restricted distributions in isopods. Remarkably, several cryptic lineages appeared to be sympatric and occurred in taxa with putatively good dispersal abilities, whereas some brooding lineages revealed broad distributions across the CCZ. Geographic distance could explain variation in faunal connectivity between regions and sites to some extent, while assumed dispersal capabilities were not as important.

The Benthic Megafaunal Assemblages of the CCZ (Eastern Pacific) and an Approach to their Management in the Face of Threatened Anthropogenic Impacts

“…The data revealed a relatively high taxonomic diversity within all faunal categories, with many species new to science. These findings have been confirmed in the more recent literature (Peterson et al, 1998;Glover et al, 2002;Wang et al, 2010;Janssen et al, 2015;Paterson et al, 2015). Key faunal groups within the CCZ are the cnidarians, echinoderms and sponges among the megafauna, and polychaete worms, nematode worms and protozoan foraminifera among the macrofauna and meiofauna; these taxa represent >50% of faunal abundance and species richness in abyssal sediments and display a broad range of ecological and life history types.…”

Phylogeny of the taxon Paralaophontodes Lang (Copepoda, Harpacticoida, Laophontodinae), including species descriptions, chorological remarks, and a key to species

“…In particular, since molecular methods have been employed for taxonomic, systematic and biogeographic (= phylogeographic) research (e.g. Hebert et al 2003, Tautz et al 2003, Kieneke et al 2012, Janssen et al 2015, Mohrbeck et al 2015, morphological approaches have been increasingly renounced. For instance, genetic investigations of some meiobenthic polychaetes, the gastrotrich Xenotrichula intermedia Remane, 1934, the calanoid copepod Eurytemora affinis (Poppe, 1880) and the harpacticoid copepod Cletocamptus deitersi (Richard, 1897) suggest that their apparent broad geographic distribution ranges, originally based on morphological studies, actually represent sibling species complexes (Westheide and Schmidt 2003, Todaro et al 1996, Lee 2000, and Rocha-Olivares et al 2001 respectively; see also Guil 2011 for further taxa).…”

Editorial: Biodiversity of the Clarion Clipperton Fracture Zone

“…Furthermore, nodule areas seem to contain higher densities of mobile megafauna compared to those lacking nodules (Amon et al 2016b;Vanreusel et al 2016). Many species appear have to have very limited geographic ranges consistent with reproduction patterns; alternatively, these species may simply be rare and undersampled (Glover et al 2002;Janssen et al 2015;Wilson 2017). In addition, there are quite a few common species, in some cases broadcast spawners, occurring widely across the CCZ (e.g.…”

“…The variety of habitats has been thought to promote higher diversity of associated benthic communities compared to abyssal areas elsewhere (Ramirez-Llodra et al 2010;Janssen et al 2015;Amon et al 2016b;Vanreusel et al 2016).…”