Insights into the abundance and diversity of abyssal megafauna in a polymetallic-nodule region in the eastern Clarion-Clipperton Zone

There is growing interest in mining polymetallic nodules in the abyssal Clarion-Clipperton Zone (CCZ) in the Pacific. Nonetheless, benthic communities in this region remain poorly known. The ABYSSLINE Project is conducting benthic biological baseline surveys for the UK Seabed Resources Ltd. exploration contract area (UK-1) in the CCZ. Using a Remotely Operated Vehicle, we surveyed megafauna at four sites within a 900 km2 stratum in the UK-1 contract area, and at a site ~250 km east of the UK-1 area, allowing us to make the first estimates of abundance and diversity. We distinguished 170 morphotypes within the UK-1 contract area but species-richness estimators suggest this could be as high as 229. Megafaunal abundance averaged 1.48 ind. m−2. Seven of 12 collected metazoan species were new to science, and four belonged to new genera. Approximately half of the morphotypes occurred only on polymetallic nodules. There were weak, but statistically significant, positive correlations between megafaunal and nodule abundance. Eastern-CCZ megafaunal diversity is high relative to two abyssal datasets from other regions, however comparisons with CCZ and DISCOL datasets are problematic given the lack of standardised methods and taxonomy. We postulate that CCZ megafaunal diversity is driven in part by habitat heterogeneity.This open access work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0

Resilience of benthic deep-sea fauna to mining activities

With increasing demand for mineral resources, extraction of polymetallic sulphides at hydrothermal vents, cobalt-rich ferromanganese crusts at seamounts, and polymetallic nodules on abyssal plains may be imminent. Here, we shortly introduce ecosystem characteristics of mining areas, report on recent mining developments, and identify potential stress and disturbances created by mining. We analyze species' potential resistance to future mining and perform meta-analyses on population density and diversity recovery after disturbances most similar to mining: volcanic eruptions at vents, fisheries on seamounts, and experiments that mimic nodule mining on abyssal plains. We report wide variation in recovery rates among taxa, size, and mobility of fauna. While densities and diversities of some taxa can recover to or even exceed pre-disturbance levels, community composition remains affected after decades. The loss of hard substrata or alteration of substrata composition may cause substantial community shifts that persist over geological timescales at mined sites. (C) 2017 Elsevier Ltd. All rights reserved.European Union Seventh Framework Programme (FP7) under the MIDAS project; FCT [IF/00029/2014/CP1230/CT0002, SFRH/ BPD/110278/2015]; Spanish RTD project NUREIEV [CTM2013-44598-R]; Ministry of Economy and Competitiveness [SGR 1068]; Generalitat de Catalunya autonomous government; European Union Horizon research and innovation programme [689518]; Fundacao para a Ciencia e a Tecnologia [UID/MAR/04292/2013]; German Ministry of Research (BMBF) [03F0707A-G]; Program Investigador FCT [IF/01194/2013/CP1199/CT0002]info:eu-repo/semantics/publishedVersio

Is the meiofauna a good indicator for climate change and anthropogenic impacts?

Our planet is changing, and one of the most pressing challenges facing the scientific community revolves around understanding how ecological communities respond to global changes. From coastal to deep-sea ecosystems, ecologists are exploring new areas of research to find model organisms that help predict the future of life on our planet. Among the different categories of organisms, meiofauna offer several advantages for the study of marine benthic ecosystems. This paper reviews the advances in the study of meiofauna with regard to climate change and anthropogenic impacts. Four taxonomic groups are valuable for predicting global changes: foraminifers (especially calcareous forms), nematodes, copepods and ostracods. Environmental variables are fundamental in the interpretation of meiofaunal patterns and multistressor experiments are more informative than single stressor ones, revealing complex ecological and biological interactions. Global change has a general negative effect on meiofauna, with important consequences on benthic food webs. However, some meiofaunal species can be favoured by the extreme conditions induced by global change, as they can exhibit remarkable physiological adaptations. This review highlights the need to incorporate studies on taxonomy, genetics and function of meiofaunal taxa into global change impact research

FIGURE 15. Microlaimus discolensis, females. A in Deep-sea nematodes of the family Microlaimidae from the Clarion-Clipperton Fracture Zone (North-Eastern Tropic Pacific), with the descriptions of three new species*

FIGURE 15. Microlaimus discolensis, females. A, specimen No. 3, total view; B, specimen No. 3, head; C, specimen No. 2, dorsal pore and associated gland. Scale bars: A = 50 µm; B = 20 µm; C = 10 µm.Published as part of <i>Miljutin, Dmitry M. & Miljutina, Maria A., 2009, Deep-sea nematodes of the family Microlaimidae from the Clarion-Clipperton Fracture Zone (North-Eastern Tropic Pacific), with the descriptions of three new species*, pp. 137-172 in Zootaxa 2096 (1)</i> on page 161, DOI: 10.11646/zootaxa.2096.1.11, <a href="http://zenodo.org/record/10093216">http://zenodo.org/record/10093216</a&gt

Trophomera elegantis Miljutin & Miljutina, 2009, sp. n.

Trophomera elegantis sp. n. Fig. 3; Table 2 Type material: Holotype: one gravid female, collection number MNHN-BN494. Type locality: 13°55.63’N, 130°12.20’W, 4900 m depth, 2–5 cm sediment layer, 28.05.2004, submersible “Nautile”, station 1597-5 CL 06. Etymology: From Latin elegans/ elegantis as adj. (slender, well-proportioned). Description: Female. Body cylindrical, with fine cuticular transversal striation visible using light microscope; anterior and posterior ends in shape of rounded cone. Cuticle thickness approximately 2 µm along whole body. Amphidial apertures pore-like, 2 µm in diameter, located at 1.3 c.b.d. from anterior end. Amphidial fovea 3.5–4.0 µm in diameter; visible under cuticle. There are four submedian, thick papillae-like, cephalic setae 2.0–2.5 µm long at half the c.b.d. of their insertion from anterior end. Two cervical papilloid sensilla 1 µm long visible laterally before and behind amphid. Mouth opening reduced to a thin apical channel in cuticle. Pharynx a non-muscular, cellular mass devoid of an internal lumen; thin, axial, tube-like structure approximately 10 µm long visible in anterior part of pharynx only. Cardia absent. Midgut, an oligocellular trophosome without internal lumen and consisting of 1 row of cells at most part of body length; borders between cells indistinct. Trophosomal cells filled with large hyaline granules; density of these granules decreasing from anterior and posterior ends towards mid-body region. Rectum vestigial, in shape of hardly distinguishable duct. Anus also vestigial, visible as a thin transverse line/bar in cuticle. Female reproductive system didelphic, amphidelphic, occupying approximately 1/6 of total body length. Ovaries reflected, both about 120 µm long; anterior one lying at right side of body, and posterior one at left side. Oviducts short, with thin walls. Uterus with several mature eggs 24x23 µm in size. Neither morphologically differentiated spermatheca nor spermatozoa observed. Hyaline ring representing a circular vaginal sphincter visible around vagina. Caudal glands absent. Host unknown. Male, juveniles: unknown. Differential diagnosis: T. elegantis sp. n. resembles T. iturupiensis Rubtzov & Platonova, 1974, T. hureaui (Petter, 1983) (Petter 1983b), and T. conicauda (Petter, 1987) by the shape and tail characteristics (tail in shape of rounded cone; ratio c’ is 1.5; ratio “maximum c.b.d. / anal c.b.d.” is between 1 and 2). The new species differs from T. iturupiensis by its shorter body length (1.5 mm vs. 26–38 mm), by the size of the cephalic sensilla (2.0–2.5 µm vs. 30–32 µm), by the structure of the trophosome (consisting of one row of cells vs. several cells on the sagittal optical section). T. elegantis sp. n. differs from T. hureaui by its shorter body length (1.5 mm vs. 2.5–3.8 mm); by the smaller length of the mature, female genital system (occupying 1/6 body length vs. 1/4–1/3 body length); by the relatively bigger size of the eggs (ratio “c.b.d. at the uterus level / maximum egg diameter” = 1.8 vs. 4.0–5.0); by the caudal tip shape (rounded vs. pointed). T. elegantis sp. n. differs from T. conicauda by its shorter body length (1.5 mm vs. 5.2–6.8 mm); by a thicker body (a = 37.3 vs. 49–58); by the relatively bigger size of the eggs (ratio “c.b.d. at the uterus level / maximum egg diameter” = 1.8 vs. 3.0). Each ovary of T. elegantis contains only 10–20 oocytes, whereas, in T. conicauda, number of oocytes in each ovary reaches hundred or more. T. elegantis sp. n. resembles T. minutissima sp. n. by parameters of its female genital system (short reflected ovaries, short oviducts, few oocytes, and comparatively large mature eggs (ratio “c.b.d. at the uterus level / maximum egg diameter” is approximately 2 in both species). T. elegantis sp. n. differs from T. minutissima by its tail shape (in shape of rounded cone vs. rounded); and by its longer and thinner tail (c = 36.3 vs. 81.8 and the ratio “tail length / anal body diameter” = 1.5 vs. 0.55).Published as part of Miljutin, Dmitry M. & Miljutina, Maria A., 2009, Description of Bathynema nodinauti gen. n., sp. n. and four new Trophomera species (Nematoda: Benthimermithidae) from the Clarion-Clipperton Fracture Zone (Eastern Tropic Pacific), supplemented with the keys to genera and species *, pp. 173-196 in Zootaxa 2096 (1) on page 179, DOI: 10.11646/zootaxa.2096.1.11, http://zenodo.org/record/532211

FIGURE 9 in Deep-sea nematodes of the family Microlaimidae from the Clarion-Clipperton Fracture Zone (North-Eastern Tropic Pacific), with the descriptions of three new species*

FIGURE 9. Microlaimus abyssalis sp. n., male, holotype. A, head; B, tail; C, total view. Scale bars: A, B = 20 µm; C = 100 µm.Published as part of <i>Miljutin, Dmitry M. & Miljutina, Maria A., 2009, Deep-sea nematodes of the family Microlaimidae from the Clarion-Clipperton Fracture Zone (North-Eastern Tropic Pacific), with the descriptions of three new species*, pp. 137-172 in Zootaxa 2096 (1)</i> on page 152, DOI: 10.11646/zootaxa.2096.1.11, <a href="http://zenodo.org/record/10093216">http://zenodo.org/record/10093216</a&gt

FIGURE 2 in Deep-sea nematodes of the family Microlaimidae from the Clarion-Clipperton Fracture Zone (North-Eastern Tropic Pacific), with the descriptions of three new species*

FIGURE 2. Aponema martinezi sp. n., male, holotype. A, total view; B, posterior end; C, anterior end. Scale bars: A = 50 µm; B, C = 20 µm.Published as part of <i>Miljutin, Dmitry M. & Miljutina, Maria A., 2009, Deep-sea nematodes of the family Microlaimidae from the Clarion-Clipperton Fracture Zone (North-Eastern Tropic Pacific), with the descriptions of three new species*, pp. 137-172 in Zootaxa 2096 (1)</i> on page 142, DOI: 10.11646/zootaxa.2096.1.11, <a href="http://zenodo.org/record/10093216">http://zenodo.org/record/10093216</a&gt

FIGURE 19 in Deep-sea nematodes of the family Microlaimidae from the Clarion-Clipperton Fracture Zone (North-Eastern Tropic Pacific), with the descriptions of three new species*

FIGURE 19. Microlaimus parviporosus sp. n., light micrographs. A, female, paratype No. 7, pores at cervical part (marked by arrows); B, female, paratype No. 7, head, optical section at level of stoma; C, paratype No. 5, female, pharyngeal bulb; D, male, holotype, anal region, optical section at level of distal part of spicule; E, male, paratype No. 4, dorsal row of pores; F, male, holotype, anal region, optical section at level of gubernaculum (marked by arrow); G, male, holotype, posterior testis (marked by arrow); H, female, paratype No. 7, vulvar region (thickened sclerotized part of dorsal wall of uterus marked by arrow); I, female, paratype No. 5, vulvar region (thickened sclerotized part of dorsal wall of uterus marked by arrow). Scale bars: A–F, H–I = 10 µm; G = 20 µm.Published as part of <i>Miljutin, Dmitry M. & Miljutina, Maria A., 2009, Deep-sea nematodes of the family Microlaimidae from the Clarion-Clipperton Fracture Zone (North-Eastern Tropic Pacific), with the descriptions of three new species*, pp. 137-172 in Zootaxa 2096 (1)</i> on page 166, DOI: 10.11646/zootaxa.2096.1.11, <a href="http://zenodo.org/record/10093216">http://zenodo.org/record/10093216</a&gt