Macrofauna-sized foraminifera in epibenthic sledge samples from five areas in the eastern Clarion-Clipperton Zone (equatorial Pacific)

Abstract

Benthic foraminifera cannot be sampled adequately using a single device. Smaller taxa are best collected using multicorers, the larger with box corers, but towed devices (dredges, trawls and epibenthic sledges) also retain many larger species. Here, we describe macrofaunal (>300 µm) foraminiferal assemblages obtained using an epibenthic sledge (EBS) in the Clarion-Clipperton Zone (eastern equatorial Pacific), a region hosting seafloor deposits of polymetallic nodules. Twelve EBS samples were collected in four areas licenced for exploration by the International Seabed Authority (ISA) to German, IOM, Belgium and French contractors, and to APEI-3, one of the protected Areas of Special Scientific Interest designated by the ISA. We recognised 280 morphospecies among 1954 specimens, with between 74 (IOM) and 121 (Belgium) in particular areas. Most (92.7%) were single-chambered monothalamids, of which 75 species (26.8%) belonged to the Komokioidea (‘komoki’), 47 (16.8%) to branched and unbranched tubes, 33 (11.8%) to chain-like and 32 (11.4%) to various ‘komoki-like’ forms. Fragments of megafaunal xenophyophores represented 21 species (7.50%), including Spiculammina delicata, previously reported only from the Russian area. Rarefaction curves and sample coverage completeness curves suggest that only a fraction of the macrofaunal foraminiferal diversity had been sampled. The occurrence of 71.8% of species in 1-2 of the 12 samples and 84.9% in 1-3 of the samples was a likely result of substantial undersampling. Dissimilarity in species composition between areas was very high: 64.2% (German vs IOM area) to 86.9% (German area vs APEI-3). Similarity within a single area was quite low: 29.1% (German) to 45.1% (IOM). In multidimensional scaling (MDS) plots, the APEI-3 area was clearly distinct in terms of faunal composition from all other areas, the French area somewhat separated from the German, IOM and Belgium areas, with the German and IOM samples being the most similar. These patterns may reflect the geographical separation of the French and APEI-3 areas and their location in deeper, more oligotrophic waters. Our study demonstrates that EBS samples from the eastern CCZ are a rich source of novel foraminiferal taxa, particularly light, easily resuspended komoki, providing a valuable perspective on foraminiferal biodiversity.

An Integrative Taxonomic Survey of Benthic Foraminiferal Species (Protista, Rhizaria) from the Eastern Clarion-Clipperton Zone

“…Although sequences were obtained from only ~21% of the 516 specimens analysed, the results are consistent with the high levels of foraminiferal diversity recorded in previous studies of morphospecies diversity in the eastern CCZ, and particularly with the strong predominance of undescribed monothalamids [13][14][15]32,66,67]. The new genetic data for undescribed monothalamids, which are linked by photographs to the corresponding test morphology, will help to improve the interpretation of HTS metabarcoding data derived from environmental samples.…”

“…Abyssal Pacific faunas have been studied since the 19th Century (e.g., [11,12]) but until recently, there were only a few records from within the boundaries of the CCZ. Most of what we know about Foraminifera in this region has come from studies published during the last 10 years (reviewed in [13]; see also [14,15]). The CCZ Foraminifera span a wide size range from the meiofauna to the megafauna.…”

Role of polymetallic-nodule dependent fauna on carbon cycling in the eastern Clarion-Clipperton Fracture Zone (Pacific)

“…Foraminiferans are one of the dominant compartments of meiobenthos (Gooday and Goineau, 2019), macrobenthos (Goineau and Gooday, 2017;Stachowska-Kamińska et al, 2022;Gooday and Wawrzyniak-Wydrowska, 2023), invertebrate megabenthos (Gooday et al, 2017;Simon-Lledóet al, 2019a;Simon-Lledóet al, 2019b), and nodule-encrusting communities (Veillette et al, 2007;Gooday et al, 2015) in the CCZ (Gooday et al, 2021). Nevertheless, their role in carbon cycling as well as the potential importance of small naked protists (i.e., ciliates, flagellates, Frontiers in Marine Science frontiersin.org amoebae) for the microbial communities are almost overlooked, except by a few specialists (Gooday et al, 2020;Gooday et al, 2021).…”