@article{2b4da72a30c94de09674feb3fe216524,
title = "Meiofaunal nematode abundance, composition, and diversity at bathyal to hadal depths in the Southeast Pacific Ocean",
abstract = "Seamounts have long been hypothesized to be biodiversity hotspots for benthic organisms, but there is limited empirical evidence to support that notion. The present study sampled meiofauna from different deep-sea sites in the Southeast Pacific Ocean (seamounts, abyssal plain, trench, island) to assess causative factors that influence meiofauna and nematode diversity and community composition. Evidence found in this study suggests that composition of meiofauna is influenced by biogeographic region and biogeochemical factors, and the high diversity that was observed at the majority of seamount sites may be related to intermediate levels of disturbance and/or variability in deposition of organic material. More studies are needed to understand the causes for why biodiversity of meiofauna is often high at seamounts, but it is plausible that seamounts are important biodiversity hotspots for nematodes and other meiofauna owing to the interaction between physical currents and erosion and variability in depositional regimes. This suggests that seamounts could be important sites for the conservation of benthic communities in the deep sea, and this should be considered in the development of marine management strategies.",
keywords = "Deep-sea, Disturbance, Meiofauna, Nematodes, Seamount, Trench",
author = "Horacek, {H. Joseph} and Soto, {Eulogio H.} and Eduardo Quiroga and Jeroen Ingels",
note = "Funding Information: We would like to thank JAMSTEC (Japan Agency for Marine-Earth Science and Technology) and the crew of the R/V MIRAI for this opportunity to sample from these deep-sea sites (trench, island, abyssal plains, and seamounts). The cruise number was MR18-06-03. We would like to additionally thank our technicians aboard the MIRAI who helped with the multi-corer: Yusuke Sato and Yuta Shinomiya (Marine Works Japan Co. Ltd) and the PI's for this cruise: Dhugal Lindsay and Masa Kinoshita (JAMSTEC). We also would like to thank the Pew Charitable Trusts for the funding provided to Eduardo Quiroga and Eulogio Soto, and the Millennium Institute of Oceanography (Universidad de Concepci{\'o}n) for supporting the samples shipping from Japan. Lastly, we thank the Research Department at the Pontificial Catholic University of Valparaiso and the University of Valpara{\'i}so for providing funding and logistical support. We are also indebted to the reviewers, who provided numerous constructive comments which have certainly contributed to a much-improved final manuscript. Funding Information: Based on nematode communities, the nMDS results (Fig, 5) show a clear separation between the westernmost seamounts/island (SPG6 and SPG7) and the eastern seamounts. This indicates that, in addition to the higher taxa composition being different between the SYG and the NR, similar patterns are observed for nematode communities. The separation of the two groups of sampling stations seems to adhere to the biogeographical classification proposed by Watling et al. (2013) in the southeast Pacific, encompassing the Southeast Pacific Ridges (incl. SYG) and the Nazca Plate (NR). Watling et al. (2013) used POC (particular organic carbon) flux (based on data from Lutz (2007)) to the seafloor between depths of 3500m and 6500m to distinguish between regions of the South Pacific Region. When applied to our study sites, it suggests our eastern stations are receiving POC influx from upwelling near the continent, whereas our western stations are receiving relatively little amounts of POC. This is corroborated by our CPE (and Chla and phaeopigment) values as proxies for organic matter of phytoplanktonic origin: SPG1-4 are all characterized by high CPE values (0.37–0.98, and 20.61 for SPG1, Atacama Trench), whereas at SPG5-7, CPE values are much lower (0.04–0.16) (values in μg/g) (Table 2). Interestingly, the separation between SYG and NR as evidenced by the communities is not as clear-cut when considering only sedimentary environmental variables (PCA in Fig. 2). However, an East-West gradient is visible in addition to a water depth gradient, with both likely influencing the amount of food resources that are available at great depth. Further support of this is given by the separation of SPG5 from SPG6-8 and SPG5 exhibiting more similarities to the eastern SPG2-4 in our PCA and nMDS plots (despite low CPE values - We suspect the low CPE values at SPG5 to be the result of nodule presence). SPG5 is situated on the SYG, but is geographically closer to the eastern seamounts, and seems to harbor communities more similar to eastern sites. It may very well be that it is situated close enough to the border of the two regions that it has communities similar to those at the NR and what is typically found in the Eastern Pacific Ocean; if correct, this would corroborate the findings in Parin et al., (1997). Aside from the overall influences of phytodetrital influx and water depth, we must also consider the roles that different habitat types and the small-scale conditions and processes at the sampling sites may play in differentiating the type of communities. Heterogeneity and variability in meiofauna communities is often expressed at the scale of centimeters (Ingels & Vanreusel 2013), and meiofauna can exhibit aggregated distributions with patches smaller than 10 cm (Rosli et al., 2016). Hence, presence of nodules, or small aggregations or retentions of organic material, or hydrodynamic disturbances at the base of seamounts and other topographical structures, may substantially alter observations and contribute to the differences we observed.This work was supported by the PEW Charitable Trusts [2018], the Research Department of Pontificial Catholic University of Valpara{\'i}so and Universidad de Valpara{\'i}so [2018], and the Millennium Institute of Oceanography, Universidad de Concepci{\'o}n [2019].We would like to thank JAMSTEC (Japan Agency for Marine-Earth Science and Technology) and the crew of the R/V MIRAI for this opportunity to sample from these deep-sea sites (trench, island, abyssal plains, and seamounts). The cruise number was MR18-06-03. We would like to additionally thank our technicians aboard the MIRAI who helped with the multi-corer: Yusuke Sato and Yuta Shinomiya (Marine Works Japan Co. Ltd) and the PI's for this cruise: Dhugal Lindsay and Masa Kinoshita (JAMSTEC). We also would like to thank the Pew Charitable Trusts for the funding provided to Eduardo Quiroga and Eulogio Soto, and the Millennium Institute of Oceanography (Universidad de Concepci{\'o}n) for supporting the samples shipping from Japan. Lastly, we thank the Research Department at the Pontificial Catholic University of Valparaiso and the University of Valpara{\'i}so for providing funding and logistical support. We are also indebted to the reviewers, who provided numerous constructive comments which have certainly contributed to a much-improved final manuscript. Publisher Copyright: {\textcopyright} 2022 Elsevier Ltd",
year = "2022",
month = oct,
doi = "10.1016/j.dsr.2022.103837",
language = "English",
volume = "188",
journal = "Deep-Sea Research Part I: Oceanographic Research Papers",
issn = "0967-0637",
}
