Limited Spatial and Temporal Variability in Meiofauna and Nematode Communities at Distant but Environmentally Similar Sites in an Area of Interest for Deep-Sea Mining

Abstract

To be able to adequately assess potential environmental impacts of deep-sea polymetallic nodule mining, the establishment of a proper environmental baseline, incorporating both spatial and temporal variability, is essential. The aim of the present study was to evaluate both spatial and intra-annual variability in meiofauna (higher taxa) and nematode communities (families and genera, and Halalaimus species) within the license area of Global Sea mineral Resources (GSR) in the northeastern Clarion Clipperton Fracture Zone (CCFZ), and to determine the efficiency of the current sampling of meiofauna and nematode diversity. In October 2015, three polymetallic nodule-bearing sites, about 60–270 km apart, located at similar depths (ca. 4,500 m) were sampled, of which one site was sampled in April in that same year. Despite the relatively large geographical distances and the statistically significant, but small, differences in sedimentary characteristics between sites, meiofauna and nematode communities were largely similar in terms of abundance, composition and diversity. Between-site differences in community composition were mainly driven by a set of rare and less abundant taxa. Moreover, although surface primary productivity in April exceeded that in October, no significant changes were observed in sedimentary characteristics or in meiofauna and nematode communities. At all sites and in both periods, Nematoda were the prevailing meiofaunal phylum, which was in turn dominated by Monhysterid genera and Acantholaimus. Our findings support the earlier purported notion of a low degree of endemism for nematode genera and meiofauna taxa in the deep sea, and hint at the possibility of large distribution ranges for at least some Halalaimus species. Taxon richness estimators revealed that the current sampling design was able to characterize the majority of the meiofauna and nematode taxa present. To conclude, implications of the present findings for environmental management and future research needs are provided

The Contribution of Fine Sieve Fractions (63–150 μm) to Foraminiferal Abundance and Diversity in an Area of the Eastern Pacific Ocean Licensed for Polymetallic Nodule Exploration

“…Stained complete foraminiferal tests were more than an order of magnitude more abundant in our five sample splits from the eastern CCZ than metazoan meiofaunal animals (i.e., 2341 stained tests compared with 167 metazoans, corresponding to overall densities of 496 and 34 individuals per 10 cm 2 , respectively). The metazoan densities are generally lower than those typical for the CCZ (11-394 individuals per 10 cm 2 in nine studies; summarized in Radziejewska, 2014, Table 3.4 therein) and the mean values (88 ± 55 to 151 ± 54 individuals per 10 cm 2 ) recently reported by Pape et al (2017) from the GSR license area in the northeastern CCZ. Moreover, the proportion (62.3%) of nematodes is relatively low and the proportion of nauplii relatively high (15.6%), compared to previous studies.…”

“…For environmental information about the study area see Amon et al (2016) and Goineau and Gooday (2017). Pape et al (2017) provide further environmental data (sediment granulometry, porosity and sorting, total organic carbon and total nitrogen content) for the GSR license area, located to the west of the UK-1 and OMS areas and in somewhat deeper water (∼4500 m). In general terms, our shipboard and laboratory methods followed those described by Goineau and Gooday (2017).…”

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

“…As nodules are confined to the upper sediment layer (Radziejewska, 2014;Petersen et al, 2016), where the majority of the meiofauna also reside, their removal through mining activities will induce drastic changes to these smallsized biota (Thiel, 2001;Miljutin et al, 2015). Inevitably, the ploughing and removal of surface sediments associated with the mining process will lead to an initial decrease in densities (Shirayama et al, 2001;Radziejewska, 2014;Jones et al, 2017).…”

“…As mining of mineral resources on land is increasingly burdened with logistic and geopolitical concerns (Petersen et al, 2016), humankind is now looking towards the deep seafloor (∼ 4000-5000 m) as a potential source to meet the global demand for metallic deposits. The abyssal plains of the Clarion-Clipperton Zone (CCZ) in the central eastern Pacific harbour the largest known accumulation of polymetallic nodules, rich in nickel, manganese, copper and cobalt (Halbach and Fellerer, 1980;Mewes et al, 2014).…”

“…Most deep-sea ecosystems are classified as heterotrophic, since they largely depend on photosynthetic production in overlying waters and the associated downward flux of particulate organic carbon for their food requirements (Levin et al, 2001;Ramirez-Llodra et al, 2010;Tittensor et al, 2011;Mc-Clain et al, 2012;Radziejewska, 2014). Despite this dependency, which is further complicated by low sedimentation rates and hence low food input at these depths (Petersen et al, 2016;Gollner et al, 2017;Sweetman et al, 2017), biodiversity is high in most deep-sea habitats (Levin et al, 2001), especially for the smaller-sized macro-and meiofauna (Hessler and Sanders, 1967;Ramirez-Llodra et al, 2010). This is partially a consequence of high heterogeneity that exists as a result of the complex geological and hydrological features of the deep seafloor (Vanreusel et al, 2010), which create microscale patchiness in both abiotic and biotic features.…”