Macrofauna are an abundant and diverse component of abyssal benthic communities and are likely to be heavily impacted by polymetallic nodule mining in the Clarion-Clipperton Zone (CCZ). In 2012, the International Seabed Authority (ISA) used available benthic biodiversity data and environmental proxies to establish nine no-mining areas, called Areas of Particular Environmental Interest (APEIs) in the CCZ. The APEIs were intended as a representative system of protected areas to safeguard biodiversity and ecosystem function across the region from mining impacts. Since 2012, a number of research programs have collected additional ecological baseline data from the CCZ. We assemble and analyze macrofaunal biodiversity data sets from eight studies, focusing on three dominant taxa (Polychaeta, Tanaidacea, and Isopoda), and encompassing 477 box-core samples to address the following questions: (1) How do macrofaunal abundance, biodiversity, and community structure vary across the CCZ, and what are the potential ecological drivers? (2) How representative are APEIs of the nearest contractor areas? (3) How broadly do macrofaunal species range across the CCZ region? and (4) What scientific gaps hinder our understanding of macrofaunal biodiversity and biogeography in the CCZ? Our analyses led us to hypothesize that sampling efficiencies vary across macrofaunal data sets from the CCZ, making quantitative comparisons between studies challenging. Nonetheless, we found that macrofaunal abundance and diversity varied substantially across the CCZ, likely due in part to variations in particulate organic carbon (POC) flux and nodule abundance. Most macrofaunal species were collected only as singletons or doubletons, with additional species still accumulating rapidly at all sites, and with most collected species appearing to be new to science. Thus, macrofaunal diversity remains poorly sampled and described across the CCZ, especially within APEIs, where a total of nine box cores have been taken across three APEIs. Some common macrofaunal species ranged over 600–3000 km, while other locally abundant species were collected across ≤ 200 km. The vast majority of macrofaunal species are rare, have been collected only at single sites, and may have restricted ranges. Major impediments to understanding baseline conditions of macrofaunal biodiversity across the CCZ include: (1) limited taxonomic description and/or barcoding of the diverse macrofauna, (2) inadequate sampling in most of the CCZ, especially within APEIs, and (3) lack of consistent sampling protocols and efficiencies.

Typhlotanaidae Sieg, 1984, is one of the most diverse Tanaidacea families from deep-sea waters. Its diversity is underestimated, and evolutionary relationships within the family remain mostly unknown. Deep-sea typhlotanaids collected from 23 sites across the Kuril-Kamchatka Trench and nearby waters were studied using an integrative taxonomy approach, combining morphological and genetic data (i.e., the mitochondrial subunit I of the cytochrome oxidase (COI) and the 18S rDNA nuclear gene). One new species of Typhlamia and two new species belonging to two new genera are described, significantly increasing the known diversity of typhlotanaids from the NW Pacific. The molecular phylogeny obtained, despite being preliminary results, was congruent with morphological data and supports the monophyly of different groups such as the ‘short-bodied’ forms (represented by Ty. cornutus and Ty. eximius) or the ‘collar’ forms (e.g., Ty. variabilis and Torquella). Molecular data confirm the non-monophyly of Typhlotanais species. Finally, the new typhlotanaid taxa seem to have distinct bathymetric distribution and ecological requirements, but further data on environmental factors and species abundances are still needed.

As one of the oldest branches of biology, taxonomy deals with the identification, classification and naming of living organisms, using a variety of tools to explore traits at the morphological and molecular level. In the deep sea, particular challenges are posed to the taxonomic differentiation of species. Relatively limited sampling effort coupled with apparent high diversity, compared to many other marine environments, means that many species sampled are undescribed, and few specimens are available for each putative species. The resulting scarce knowledge of intraspecific variation makes it difficult to recognize species boundaries and thus to assess the actual diversity and distribution of species. In this review article, we highlight some of these challenges in deep-sea taxonomy using the example of peracarid crustaceans. Specifically, we offer a detailed overview of traditional as well as modern methods that are used in the taxonomic analysis of deep-sea Peracarida. Furthermore, methods are presented that have not yet been used in peracarid taxonomy, but have potential for the analysis of internal and external structures in the future. The focus of this compilation is on morphological methods for the identification, delimitation and description of species, with references to molecular analysis included where relevant, as these methods are an indispensable part of an integrative taxonomic approach. The taxonomic impediment, i.e. the shortage of taxonomists in view of a high undescribed biodiversity, is discussed in the context of the existing large taxonomic knowledge gaps in connection with the increasing threat to deep-sea ecosystems. Whilst peracarid crustaceans are used here as an exemplary taxon, the methodology described has broad relevance to many other deep-sea taxa, and thus will support broader research into deep-sea biodiversity and ecology more widely.

A new family of paratanaoidean Tanaidacea, the hamatipedids, formerly part of the Typhlotanaidae, is established to accommodate three genera (Hamatipeda and two new). Deep-sea hamatipedids collected from four sites in the Atlantic (Argentine and Guiana basins) and 14 sites from the Southeast coast of Australia were studied using a taxonomic approach combining morphological and morphometric data. Four new species of Hamatipeda and one of a new genus are described from different deep-sea areas of the Atlantic and Pacific oceans. Hamatipeda sima originally classified within Hamatipeda, is transferred to a new genus. We observed that several morphometric characters (i.e., length of the last two pereonites) in different life-stages of one of the new Hamatipeda species (neuter, manca-2, and manca-3) are correlated with the total body length (TBL). Applying a morphometric approach, we aimed: (1) to identify those ontogenetic-dependent characters, and (2) to detect the characters, which can be used in discrimination of Hamatipedidae species, regardless their life-stage.

publisher: Pensoft Publishers articletitle: The London Workshop on the Biogeography and Connectivity of the Clarion-Clipperton Zone journaltitle: Research Ideas and Outcomes copyright: http://creativecommons.org/licenses/by/4.0/ received: 2016-09-16 published: 2016-09-1