Area Of Particular Environmental Interest Research Articles

Unexpected high abyssal ophiuroid diversity in polymetallic nodule fields of the northeast Pacific Ocean and implications for conservation

Abstract. The largest and commercially appealing mineral deposits can be found in the abyssal sea floor of the Clarion-Clipperton Zone (CCZ), a polymetallic nodule province, in the NE Pacific Ocean, where experimental mining is due to take place. In anticipation of deep-sea mining impacts, it has become essential to rapidly and accurately assess biodiversity. For this reason, ophiuroid material collected during eight scientific cruises from five exploration licence areas within CCZ, one area being protected from mining (APEI3, Area of Particular Environmental Interest) in the periphery of CCZ and the DISturbance and re-COLonisation (DISCOL) Experimental Area (DEA), in the SE Pacific Ocean, was examined. Specimens were genetically analysed using a fragment of the mitochondrial cytochrome c oxidase subunit I (COI). Maximum-likelihood and neighbour-joining trees were constructed, while four tree-based and distance-based methods of species delineation (automatic barcode gap discovery, ABGD; barcode index numbers, BINs; general mixed Yule–coalescent, GMYC; multi-rate Poisson tree process, mPTP) were employed to propose secondary species hypotheses (SSHs) within the ophiuroids collected. The species delimitation analyses' concordant results revealed the presence of 43 deep-sea brittle star SSHs, revealing an unexpectedly high diversity and showing that the most conspicuous invertebrates in abyssal plains have been so far considerably underestimated. The number of SSHs found in each area varied from five (IFREMER area) to 24 (BGR (Federal Institute for Geosciences and Natural Resources, Germany) area) while 13 SSHs were represented by singletons. None of the SSHs were found to be present in all seven areas while the majority of species (44.2 %) had a single-area presence (19 SSHs). The most common species were Ophioleucidae sp. (Species 29), Amphioplus daleus (Species 2) and Ophiosphalma glabrum (Species 3), present in all areas except APEI3. The biodiversity patterns could be mainly attributed to particulate organic carbon (POC) fluxes that could explain the highest species numbers found in BGR (German contractor area) and UKSRL (UK Seabed Resources Ltd, UK contractor area) areas. The five exploration contract areas belong to a mesotrophic province, while conversely the APEI3 is located in an oligotrophic province, which could explain the lowest diversity as well as very low similarity with the other six study areas. Based on these results the representativeness and the appropriateness of APEI3 to meet its purpose of preserving the biodiversity of the CCZ fauna are questioned. Finally, this study provides the foundation for biogeographic and functional analyses that will provide insight into the drivers of species diversity and its role in ecosystem function.

Macrostylis metallicola spec. nov.-an isopod with geographically clustered genetic variability from a polymetallic-nodule area in the Clarion-Clipperton Fracture Zone.

BackgroundThe Clarion-Clipperton Fracture Zone (CCFZ) in the Northeast Central Pacific Ocean is a region of heightened scientific and public interest because of its wealth in manganese nodules. Due to a poor ecological understanding at the abyssal seafloor and limited knowledge of the organisms inhabiting this area, huge efforts in alpha taxonomy are required. To predict and manage potential hazards associated with future mining, taxonomy is an essential first step to grasp fundamental ecosystem traits, such as biogeographic patterns, connectivity, and the potential for post-impact recolonization. Amongst samples from the Global Sea Mineral Resources NV exploration area (EA) in the CCFZ an undescribed species of the isopod crustacean family Macrostylidae was discovered. Previously, it has been reported from two other nearby regions, the Institut Français de Recherche pour l’Exploitation de la Mer and BGR EAs. There it was one of the more widely distributed and abundant species of the benthic macrofauna and exhibited geographically structured populations. It nevertheless remained taxonomically undescribed so far.MethodsThe new species is described by means of integrative taxonomy. Morphologically, macro photography, confocal microscopy, scanning electron microscopy and light microscopy were used to describe the species and to get first insights on its phylogenetic origin. Additionally, mitochondrial DNA markers were used to test the morphological allocation of the two dimorphic sexes and juvenile stages, to analyze geographic patterns of genetic differentiation, and to study intra-and inter-species relationships, also in light of previously published population genetics on this species.ResultsThe new species, Macrostylis metallicola spec. nov., is a typical representative of Macrostylidae as recognizable from the fossosoma, prognathous cephalothorax, and styliform uropods. It can be morphologically distinguished from congeners by a combination of character states which include the autapomorphic shape of the first pleopod of the copulatory male. A sexual dimorphism, as expressed by a peculiar sequence of article length-width ratios of the male antennula, indicates a relationship with M. marionae Kniesz, Brandt & Riehl (2018) and M. longipes Hansen (1916) amongst other species sharing this dimorphism. Mitochondrial genetic markers point in a similar direction. M. metallicola appears to be amongst the more common and widely distributed components of the benthic macrofauna in this region which may suggest a resilience of this species to future mining activities because of its apparent potential for recolonization of impacted sites from adjacent areas of particular environmental interest. The genetic data, however, show geographic clustering of its genetic variability, pointing towards a limited potential for dispersal. Local extinction of populations could potentially not be compensated quickly and would mean a loss of genetic diversity of this species.

Alpha and beta diversity patterns of polychaete assemblages across the nodule province of the eastern Clarion-Clipperton Fracture Zone (equatorial Pacific)

Abstract. In the abyssal equatorial Pacific Ocean, most of the seafloor of the Clarion-Clipperton Fracture Zone (CCFZ), a 6 million km2 polymetallic nodule province, has been preempted for future mining. In light of the large environmental footprint that mining would leave and given the diversity and the vulnerability of the abyssal fauna, the International Seabed Authority has implemented a regional management plan that includes the creation of nine Areas of Particular Environmental Interest (APEIs) located at the periphery of the CCFZ. The scientific principles for the design of the APEIs were based on the best – albeit very limited – knowledge of the area. The fauna and habitats in the APEIs are unknown, as are species' ranges and the extent of biodiversity across the CCFZ. As part of the Joint Programming Initiative Healthy and Productive Seas and Oceans (JPI Oceans) pilot action “Ecological aspects of deep-sea mining”, the SO239 cruise provided data to improve species inventories, determine species ranges, identify the drivers of beta diversity patterns and assess the representativeness of an APEI. Four exploration contract areas and an APEI (APEI no. 3) were sampled along a gradient of sea surface primary productivity that spanned a distance of 1440 km in the eastern CCFZ. Between three and eight quantitative box cores (0.25 m2; 0–10 cm) were sampled in each study area, resulting in a large collection of polychaetes that were morphologically and molecularly (cytochrome c oxidase subunit I and 16S genes) analyzed. A total of 275 polychaete morphospecies were identified. Only one morphospecies was shared among all five study areas and 49 % were singletons. The patterns in community structure and composition were mainly attributed to variations in organic carbon fluxes to the seafloor at the regional scale and nodule density at the local scale, thus supporting the main assumptions underlying the design of the APEIs. However, the APEI no. 3, which is located in an oligotrophic province and separated from the CCFZ by the Clarion Fracture Zone, showed the lowest densities, lowest diversity, and a very low and distant independent similarity in community composition compared to the contract areas, thus questioning the representativeness and the appropriateness of APEI no. 3 to meet its purpose of diversity preservation. Among the four exploration contracts, which belong to a mesotrophic province, the distance decay of similarity provided a species turnover of 0.04 species km−1, an average species range of 25 km and an extrapolated richness of up to 240 000 polychaete species in the CCFZ. By contrast, nonparametric estimators of diversity predict a regional richness of up to 498 species. Both estimates are biased by the high frequency of singletons in the dataset, which likely result from under-sampling and merely reflect our level of uncertainty. The assessment of potential risks and scales of biodiversity loss due to nodule mining thus requires an appropriate inventory of species richness in the CCFZ.

Post-depositional manganese mobilization during the last glacial period in sediments of the eastern Clarion-Clipperton Zone, Pacific Ocean

Numerous studies have provided compelling evidence that the Pacific Ocean has experienced substantial glacial/interglacial changes in bottom-water oxygenation associated with enhanced carbon dioxide storage in the glacial deep ocean. Under postulated low glacial bottom-water oxygen concentrations (O2bw), redox zonation, biogeochemical processes and element fluxes in the sediments must have been distinctively different during the last glacial period (LGP) compared to current well-oxygenated conditions.In this study, we have investigated six sites situated in various European contract areas for the exploration of polymetallic nodules within the Clarion-Clipperton Zone (CCZ) in the NE Pacific and one site located in a protected Area of Particular Environmental Interest (APEI3) north of the CCZ. We found bulk sediment Mn maxima of up to 1 wt% in the upper oxic 10 cm of the sediments at all sites except for the APEI3 site. The application of a combined leaching protocol for the extraction of sedimentary Mn and Fe minerals revealed that mobilizable Mn(IV) represents the dominant Mn(oxyhydr)oxide phase with more than 70% of bulk solid-phase Mn. Steady state transport-reaction modeling showed that at postulated glacial O2bw of 35 μM, the oxic zone in the sediments was much more compressed than today where upward diffusing pore-water Mn2+ was oxidized and precipitated as authigenic Mn(IV) at the oxic-suboxic redox boundary in the upper 5 cm of the sediments. Transient transport-reaction modeling demonstrated that with increasing O2bw during the last glacial termination to current levels of ∼ 150 μM, (1) the oxic-suboxic redox boundary migrated deeper into the sediments and (2) the authigenic Mn(IV) peak was continuously mixed into subsequently deposited sediments by bioturbation causing the observed mobilizable Mn(IV) enrichment in the surface sediments. Such a distinct mobilizable Mn(IV) maximum was not found in the surface sediments of the APEI3 site, which indicates that the oxic zone was not as condensed during the LGP at this site due to two- to threefold lower organic carbon burial rates. Leaching data for sedimentary Fe minerals suggest that Fe(III) has not been diagenetically redistributed during the LGP at any of the investigated sites. Our results demonstrate that the basin-wide deoxygenation in the NE Pacific during the LGP was associated with (1) a much more compressed oxic zone at sites with carbon burial fluxes higher than 1.5 mg Corg m−2d−1, (2) the authigenic formation of a sub-surface mobilizable Mn(IV) maximum in the upper 5 cm of the sediments and (3) a possibly intensified suboxic-diagenetic growth of polymetallic nodules. As our study provides evidence that authigenic Mn(IV) precipitated in the surface sediments under postulated low glacial O2bw, it contributes to resolving a long-standing controversy concerning the origin of widely observed Mn-rich layers in glacial/deglacial deep-sea sediments.

Deep ocean seascape and Pseudotanaidae (Crustacea: Tanaidacea) diversity at the Clarion-Clipperton Fracture Zone

Understanding the diversity and spatial distribution of benthic species is fundamental to properly assess the impact of deep sea mining. Tanaidacea provide an exceptional opportunity for assessing spatial patterns in the deep-sea, given their low mobility and limited dispersal potential. The diversity and distribution of pseudotanaid species is characterized here for the Clarion and Clipperton Fractures Zone (CCZ), which is the most extensive deposit field of metallic nodules. Samples were taken from the Belgian, German and French license areas, but also from the APEI 3 (Area of Particular Environmental Interest 3) of the Interoceanmetal consortium associates. The combination of morphological and genetic data uncovered one new pseudotanaid genus (Beksitanais n. gen.) and 14 new species of Pseudotanais (2 of them virtual taxa). Moreover, our results suggest that spatial structuring of pseudotanaid diversity is correlated with deep-sea features, particularly the presence of fractures and seamount chains crossing the CCZ. The presence of geographical barriers delimiting species distributions has important implications for the establishment of protected areas, and the APEI3 protected area contains only one third of the total pseudotanaid species in CCZ. The specimen collection studied here is extremely valuable and represents an important first step in characterizing the diversity and distribution of pseudotanaids within the Tropical Eastern Pacific.

Abyssal fauna of polymetallic nodule exploration areas, eastern Clarion-Clipperton Zone, central Pacific Ocean: Annelida: Capitellidae, Opheliidae, Scalibregmatidae, and Travisiidae.

We present DNA taxonomy of abyssal polychaete worms from the eastern Clarion-Clipperton Zone (CCZ), central Pacific Ocean, using material collected as part of the Abyssal Baseline (ABYSSLINE) environmental survey cruises ‘AB01’ and ‘AB02’ to the UK Seabed Resources Ltd (UKSRL) polymetallic nodule exploration contract area ‘UK-1’, the Ocean Mineral Singapore exploration contract area ‘OMS-1’ and an Area of Particular Environmental Interest, ‘APEI-6’. This is the fourth paper in a series to provide regional taxonomic data with previous papers reporting on Cnidaria, Echinodermata and Mollusca. Taxonomic data are presented for 23 species from 85 records within four polychaete families: Capitellidae, Opheliidae, Scalibregmatidae and Travisiidae, identified by a combination of morphological and genetic data, including molecular phylogenetic analyses. Two taxa (genetically separated from one another) morphologically matched the same known cosmopolitan species, Ophelina abranchiata that has a type locality in a different ocean basin and depth from where no genetic data was available. These two species were assigned the open nomenclature ‘cf.’ as a precautionary approach in taxon assignments to avoid over-estimating species ranges. Twelve (12) taxa are here described as new species, Ammotrypanella keenanisp. nov., Ammotrypanella kerstenisp. nov., Ophelina curlisp. nov., Ophelina ganaesp. nov., Ophelina juhazisp. nov., Ophelina martinezarbizuisp. nov., Ophelina meyeraesp. nov., Ophelina nunnallyisp. nov., Oligobregma brasieraesp. nov., Oligobregma tanisp. nov., Oligobregma whaleyisp. nov. and Travisia ziegleraesp. nov. For the remaining nine taxa, we have determined them to be potentially new species, for which we make the raw data, imagery and vouchers available for future taxonomic study. The CCZ is a region undergoing intense exploration for potential deep-sea mineral extraction from polymetallic nodules. We present these data to facilitate future taxonomic and environmental impact study by making both data and voucher materials available through curated and accessible biological collections.

Distribution of free-living marine nematodes in the Clarion–Clipperton Zone: implications for future deep-sea mining scenarios

Abstract. Mining of polymetallic nodules in abyssal seafloor sediments promises to address the growing worldwide demand for metallic minerals. Given that prospective mining operations are likely to have profound impacts on deep seafloor communities, industrial investment has been accompanied by scientific involvement for the assessment of baseline conditions and provision of guidelines for environmentally sustainable mining practices. Benthic meiofaunal communities were studied in four prospective mining areas of the Clarion–Clipperton Zone (CCZ) in the eastern Pacific Ocean, arranged in a southeast–northwest fashion coinciding with the productivity gradient in the area. Additionally, samples were collected from the Area of Particular Environmental Interest no. 3 (APEI-3) in the northwest of the CCZ, where mining will be prohibited and which should serve as a “source area” for the biota within the larger CCZ. Total densities in the 0–5 cm upper layer of the sediment were influenced by sedimentary characteristics, water depth and nodule density at the various sampling locations, indicating the importance of nodules for meiofaunal standing stock. Nematodes were the most abundant meiobenthic taxon, and their assemblages were typically dominated by a few genera (generally 2–6) accounting for 40 %–70 % of all individuals, which were also widely spread along the CCZ and shared among all sampled license areas. However, almost half of the communities consisted of rare genera, each contributing less than 5 % to the overall abundances and displaying a distribution which was usually restricted to a single license area. The same observations (dominant and widely spread versus rare and scattered) could be made for the species of one of the dominant genera, Halalaimus, implying that it might be mainly these rare genera and species that will be vulnerable to mining-induced changes in their habitat.

Fe-Mn nodule morphotypes from the NE Clarion-Clipperton Fracture Zone, Pacific Ocean: Comparison of mineralogy, geochemistry and genesis

Ferromanganese nodules are polymetallic ore deposits considered to be archives of paleoceanographic proxies and targets of deep-sea mining. In the present paper, nodules and underlying sediments from a claim area (UK-1) within the eastern Clarion-Clipperton Fracture Zone (CCFZ) and from Area of Particular Environmental Interest (APEI-6) were analyzed. In each area, nodules are characterized by contrasting morphology, mineralogy, geochemistry and abundance. The obtained results reveal three types of Fe-Mn nodules. Type 1: smooth irregular nodules with sizes of 1–1.5 cm containing mainly 10 Å phyllomanganates and phillipsite; Mn/Fe = 2.50, high trace metal abundances Co + Ni + Cu = 2.10%, high rare earth element and yttrium (REY) concentrations (1515 ppm), positive Ce anomaly; hydrogenetic origin. Type 2: smooth discoidal nodules with sizes of 2–4 cm composed of 10 Å phyllomanganates and buserite I; Mn/Fe = 3.65, high trace metal enrichment Co + Ni + Cu = 2.35%, positive Ce anomaly; mainly formed by hydrogenous precipitation. Type 3: nodules (3–15 cm) with botryoidal surfaces and well-defined concentric zonality; Mn/Fe = 5.1, trace metal content Co + Ni + Cu = 2.42%. The textural and chemical characteristics of nodules suggest that they acquire metals as a result of both hydrogenetic and diagenetic processes during nodule growth in alternating oxic/suboxic conditions. Scanning electron microscopy (SEM), in conjunction with energy-dispersive X-ray spectroscopy (EDS), reveals abundant pseudomorphs, which is considered possible evidence for biomineralization within the nodules. The morphology, mineralogy and geochemistry of the studied nodules are strongly affected by post-accretional diagenetic processes, which are closely linked to biomineralization.

Ecology of a polymetallic nodule occurrence gradient: Implications for deep-sea mining.

Abyssal polymetallic nodule fields constitute an unusual deep‐sea habitat. The mix of soft sediment and the hard substratum provided by nodules increases the complexity of these environments. Hard substrata typically support a very distinct fauna to that of seabed sediments, and its presence can play a major role in the structuring of benthic assemblages. We assessed the influence of seafloor nodule cover on the megabenthos of a marine conservation area (area of particular environmental interest 6) in the Clarion Clipperton Zone (3950–4250 m water depth) using extensive photographic surveys from an autonomous underwater vehicle. Variations in nodule cover (1–20%) appeared to exert statistically significant differences in faunal standing stocks, some biological diversity attributes, faunal composition, functional group composition, and the distribution of individual species. The standing stock of both the metazoan fauna and the giant protists (xenophyophores) doubled with a very modest initial increase in nodule cover (from 1% to 3%). Perhaps contrary to expectation, we detected little if any substantive variation in biological diversity along the nodule cover gradient. Faunal composition varied continuously along the nodule cover gradient. We discuss these results in the context of potential seabed‐mining operations and the associated sustainable management and conservation plans. We note in particular that successful conservation actions will likely require the preservation of areas comprising the full range of nodule cover and not just the low cover areas that are least attractive to mining.

Controls on the chemical composition of ferromanganese nodules in the Clarion-Clipperton Fracture Zone, eastern equatorial Pacific

Ferromanganese nodules have long been considered an attractive source for Mn, Co, Ni and Cu and, potentially, for the rare earth elements and yttrium (REY). Sixteen exploration contracts have recently been granted for the Clarion-Clipperton Fracture Zone (CCFZ) in the eastern equatorial Pacific and, because of concern about the environmental impacts of seafloor mining, some parts of the CCFZ have been designated ‘Areas of Particular Environmental Interest’ (APEI) from which mining will be excluded. As the APEIs were selected based on surface ocean characteristics and seafloor topography, estimated from satellite altimetry, the abundance and composition of nodules in these areas are unknown, and as a result their relevance as an intended baseline for mining disturbance has not been demonstrated.To fill this gap, we have undertaken a detailed study of the chemical composition of nodules and seafloor sediments in the UK Contract area in the CCFZ and its closest APEI, APEI-6. There are distinct differences between the two sites: nodules from the UK Contract area are larger (10–15 cm in diameter) compared to those from APEI-6 (2–4 cm diameter), and they have faster growth rates (~11 vs ~3 mm/Ma). Nodules from APEI-6 have, on average, higher contents of Fe (7.2 vs. 5.7 wt%), Co (0.28 vs. 0.13 wt%) and total REY (1120 vs. 715 ppm) relative to those from the UK Contract area. Analyses of individual growth layers reveal that nodules from the UK Contract area contain a greater proportion of Mn-rich phases that are also enriched in Ni and Cu. Although pore waters in the uppermost sediments are oxygen replete today, these layers likely precipitated from suboxic sediment pore waters indicating that the supply of organic material to the sediments in this area has been higher in the past. Sediments from the UK Contract area, in turn, have higher Mn/Al ratios compared to sediments from APEI-6 and have a higher proportion of Mn in easily-reducible phases. Nodules from APEI-6 have a greater proportion of Fe-rich layers that are also enriched in Co and the REY, and likely precipitated from seawater. These differences in the chemical composition of nodules from the UK Contract area and APEI-6, as well as differences in the oxygen penetration depth in the sediments, mean that APEI-6 does not provide a relevant geochemical baseline for mining disturbance in the UK Contract area, or for many other contract areas within the CCFZ.

Megafaunal variation in the abyssal landscape of the Clarion Clipperton Zone

The potential for imminent polymetallic nodule mining in the Clarion Clipperton Fracture Zone (CCZ) has attracted considerable scientific and public attention. This concern stems from both the extremely large seafloor areas that may be impacted by mining, and the very limited knowledge of the fauna and ecology of this region. The environmental factors regulating seafloor ecology are still very poorly understood. In this study, we focus on megafaunal ecology in the proposed conservation zone ‘Area of Particular Environmental Interest 6′ (study area centred 17°16′N, 122°55′W). We employ bathymetric data to objectively define three landscape types in the area (a level bottom Flat, an elevated Ridge, a depressed Trough; water depth 3950–4250 m) that are characteristic of the wider CCZ. We use direct seabed sampling to characterise the sedimentary environment in each landscape, detecting no statistically significant differences in particle size distributions or organic matter content. Additional seafloor characteristics and data on both the metazoan and xenophyophore components of the megafauna were derived by extensive photographic survey from an autonomous underwater vehicle. Image data revealed that there were statistically significant differences in seafloor cover by nodules and in the occurrence of other hard substrata habitat between landscapes. Statistically significant differences in megafauna standing stock, functional structuring, diversity, and faunal composition were detected between landscapes. The Flat and Ridge areas exhibited a significantly higher standing stock and a distinct assemblage composition compared to the Trough. Geomorphological variations, presumably regulating local bottom water flows and the occurrence of nodule and xenophyophore test substrata, between study areas may be the mechanism driving these assemblage differences. We also used these data to assess the influence of sampling unit size on the estimation of ecological parameters. We discuss these results in the contexts of regional benthic ecology and the appropriate management of potential mining activities in the CCZ and elsewhere in the deep ocean.

Implications of population connectivity studies for the design of marine protected areas in the deep sea: An example of a demosponge from the Clarion-Clipperton Zone.

The abyssal demosponge Plenaster craigi inhabits the Clarion-Clipperton Zone (CCZ) in the northeast Pacific, a region with abundant seafloor polymetallic nodules with potential mining interest. Since P.craigi is a very abundant encrusting sponge on nodules, understanding its genetic diversity and connectivity could provide important insights into extinction risks and design of marine protected areas. Our main aim was to assess the effectiveness of the Area of Particular Environmental Interest 6 (APEI-6) as a potential genetic reservoir for three adjacent mining exploration contract areas (UK-1A, UK-1B and OMS-1A). As in many other sponges, COI showed extremely low variability even for samples ~900km apart. Conversely, the 168 individuals of P.craigi, genotyped for 11 microsatellite markers, provided strong genetic structure at large geographical scales not explained by isolation by distance (IBD). Interestingly, we detected molecular affinities between samples from APEI-6 and UK-1A, despite being separated ~800km. Although our migration analysis inferred very little progeny dispersal of individuals between areas, the major differentiation of OMS-1A from the other areas might be explained by the occurrence of predominantly northeasterly transport predicted by the HYCOM hydrodynamic model. Our study suggests that although APEI-6 does serve a conservation role, with species connectivity to the exploration areas, it is on its own inadequate as a propagule source for P.craigi for the entire eastern portion of the CCZ. Our new data suggest that an APEI located to the east and/or the south of the UK-1, OMS-1, BGR, TOML and NORI areas would be highly valuable.

Natural spatial variability of depositional conditions, biogeochemical processes and element fluxes in sediments of the eastern Clarion-Clipperton Zone, Pacific Ocean

The manganese nodule belt within the Clarion and Clipperton Fracture Zones (CCZ) in the abyssal NE Pacific Ocean is characterized by numerous seamounts, low organic matter (OM) depositional fluxes and meter-scale oxygen penetration depths (OPD) into the sediment. The region hosts contract areas for the exploration of polymetallic nodules and Areas of Particular Environmental Interest (APEI) as protected areas. In order to assess the impact of potential mining on these deep-sea sediments and ecosystems, a thorough determination of the natural spatial variability of depositional and geochemical conditions as well as biogeochemical processes and element fluxes in the different exploration areas is required.Here, we present a comparative study on (1) sedimentation rates and bioturbation depths, (2) redox zonation of the sediments and element fluxes as well as (3) rates and pathways of biogeochemical reactions at six sites in the eastern CCZ. The sites are located in four European contract areas and in the APEI3. Our results demonstrate that the natural spatial variability of depositional and (bio)geochemical conditions in this deep-sea sedimentary environment is much larger than previously thought. We found that the OPD varies between 1 and 4.5 m, while the sediments at two sites are oxic throughout the sampled interval (7.5 m depth). Below the OPD, manganese and nitrate reduction occur concurrently in the suboxic zone with pore-water Mn2+ concentrations of up to 25 µM. The thickness of the suboxic zone extends over depth intervals of less than 3 m to more than 8 m. Our data and the applied transport-reaction model suggest that the extension of the oxic and suboxic zones is ultimately determined by the (1) low flux of particulate organic carbon (POC) of 1–2 mg Corg m−2 d−1 to the seafloor, (2) low sedimentation rates between 0.2 and 1.15 cm kyr−1 and (3) oxidation of pore-water Mn2+ at depth. The diagenetic model reveals that aerobic respiration is the main biogeochemical process driving OM degradation. Due to very low POC fluxes of 1 mg Corg m−2 d−1 to the seafloor at the site investigated in the protected APEI3 area, respiration rates are twofold lower than at the other study sites. Thus, the APEI3 site does not represent the (bio)geochemical conditions that prevail in the other investigated sites located in the European contract areas. Lateral variations in surface water productivity are generally reflected in the POC fluxes to the seafloor across the various areas but deviate from this trend at two of the study sites. We suggest that the observed spatial variations in depositional and (bio)geochemical conditions result from differences in the degree of degradation of OM in the water column and heterogeneous sedimentation patterns caused by the interaction of bottom water currents with seafloor topography.

Mitochondrial genome and polymorphic microsatellite markers from the abyssal sponge Plenaster craigi Lim & Wiklund, 2017: tools for understanding the impact of deep-sea mining

The abyssal demosponge Plenaster craigi is endemic to the Clarion - Clipperton Zone (CCZ) in the NE Pacific, a region with abundant seafloor polymetallic nodules and of potential interest for mining. Plenaster craigi encrusts on these nodules and is an abundant component of the ecosystem. To assess the impact of mining operations, it is crucial to understand the genetics of this species, because its genetic diversity and connectivity across the area may be representative of other nodule-encrusting invertebrate epifauna. Here we describe and characterize 14 polymorphic microsatellite markers from this keystone species using Illumina MiSeq, tested for 75 individuals from three different areas across the CCZ, including an Area of Particular Environmental Interest (APEI-6) and two areas within the adjacent UK1 mining exploration area. The number of alleles per locus ranged from 3 to 30 (13.33 average alleles for all loci across areas). Observed and expected heterozygosity ranged from 0.909–0.048 and from 0.954–0.255, respectively. Several loci displayed significant deviation from the Hardy-Weinberg equilibrium, which appears to be common in other sponge studies. The microsatellite loci described here will be used to assess the genetic structure and connectivity on populations of the sponge across the CCZ, which will be invaluable for monitoring the impact of mining operations on its habitat. Also, we provide the annotated mitochondrial genome of P. craigi, compare its arrangement with other closely related species, and discuss the phylogenetic framework for the sponge after Maximum Likelihood and Bayesian Inference analyses using nucleotide and amino acid sequences data sets separately.

Abundance and morphology of Paleodictyon nodosum, observed at the Clarion-Clipperton Zone

Paleodictyon is an important trace fossil characterised by a regular hexagonal structure and typical of ancient deep-ocean habitats as far back as the Ordovician. It is represented in modern deep-sea settings by Paleodictyon nodosum, known from the Mid-Atlantic Ridge, the South Atlantic, and off eastern Australia. Here we report the occurrence of P. nodosum in the Clarion Clipperton Zone (CCZ), abyssal equatorial Pacific, an area characterised by polymetallic nodule fields. At the study site within the International Seabed Authority northeastern Area of Particular Environmental Interest (APEI-6), P. nodosum appeared as a compact, regular pattern of small circular openings on the seafloor, each pattern interpreted as reflecting the activity of an individual organism. The patterns had a mean size (maximum dimension) of 45 mm ± 16 mm SD (n = 841) and occurred at a density of 0.33 individuals m−2. Most (82%) were interrupted by nodules, but those that were not displayed both regular (59%) and irregular (41%) forms, the former having equal numbers of rows along the three axes (6 x 6 x 6 and 8 x 8 x 8). In both size and morphology, our Paleodictyon traces were more similar to the Australian examples than to those from the Mid-Atlantic Ridge.

Seabed mining: International Seabed Authority environmental management plan for the Clarion–Clipperton Zone. A partnership approach

In 2012 the International Seabed Authority approved an Environmental Management Plan (EMP) for the Clarion–Clipperton Fracture Zone CCZ in the Eastern Central Pacific. The EMP is a proactive spatial management strategy that anticipates mining of polymetallic nodules and that includes the designation of Areas of Particular Environmental Interest (APEIs). The implementation of the EMP and the sound application of marine spatial planning require sufficient high-quality data to inform decision-makers and draw credible boundaries of protected areas. This paper outlines the development of the EMP in the context of the Authority׳s responsibilities with respect to the protection of the marine environment. The paper further highlights needs for research and data collection and introduces a related EU research project aiming to inform the development of mining guidelines. The authors suggest that the sustainable development of deep sea resources in the CCZ could be considered as a model for blue growth.

Integrated Assessment of Water Framework Directive Nitrate Reduction Measures

The paper develops a spatially explicit method for integrated assessment of alternative measures to reduce nitrate leaching into rivers and lakes from farms, a key objective of the European Union Water Framework Directive (WFD). This approach combines regression models, based on Farm Business Survey and June Agricultural Census data, for predicting the economic costs to agriculture of nitrate reduction measures with a hydrological model encompassing both diffuse and point source pollution to estimate the water quality changes arising from such instruments. A case study of the agriculturally diverse Yorkshire Derwent catchment in the north of England illustrates the overall approach. We consider three measures previously proposed to the UK Department for Environment, Food and Rural Affairs (Defra) for tackling diffuse agricultural pollution: (i) reducing inorganic fertilizer application; (ii) reducing livestock stocking rates; and (iii) converting arable land to un-grazed grassland. The results reveal marked variability in the economic impacts and nitrate leaching reductions, with the cost effectiveness of these measures varying by up to a factor of three. Furthermore, the analysis suggests that WFD implementation may entail major land use changes resulting in substantial economic impacts. The spatially explicit aspect of our approach permits assessment of the optimal targeting of policy implementation to areas of particular environmental interest.