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1. Foraminiferal population dynamics on elevated plastic substrates and in sediments at 4000 m in the Eastern Pacific

   Burkett, A.M.; Rathburn, A.E.; Gonzolez Acevedo, A; Gonzolez Acevedo, C; Ezpeleta, J (November 2023, Marine ecology Progress series)

   none. (Ed.)

   ABSTRACT: Although plastics are becoming more prevalent, even in the far reaches of the deep sea, the influence of these novel attachment surfaces has yet to be systematically studied regarding the ecology and distribution patterns of attached fauna. Herein, we report the abundances and vertical distribution patterns of epibenthic foraminifera living on plastics after 2 yr on the seafloor at 4000 m water depth and compare these populations with those of nearby naturally occurring substrates and their surrounding sediments. After 2 yr, 239 foraminifera were found attached to 4 Seafloor Epibenthic Attachment Cubes (SEA3s). Dominant taxa included Cibicidoides wuellerstorfi var. lobatulus, Pyrgoella sp., and arborescent foraminifera. Variations in colonization height and abundance between plastic types were observed, but no clear drivers of these patterns can be ascertained from this study. Foraminiferal populations from elevated substrates and the nearby sediment cores showed no significant overlap in populations, suggesting that foraminifera colonizing SEA3s did not originate from surrounding sediments and likely recruited from other elevated substrates common in the area (e.g. glass sponges). This study demonstrates that plastics serve as hard substrates which deep-sea foraminifera inhabit and that plastics may persist for extended periods of time, potentially altering ecosystem compositions in environments dominated by soft sediments. There is a significant difference between colonizing epifaunal and sediment populations, which raises interesting questions about colonization and distribution processes in deep bathyal and abyssal environments. Epi benthic foraminifera at - tached to elevated substrates may be underrepresented in the sedimentary record through preservation and sampling biases. 

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2. Metazoan diversity and seasonality through eDNA metabarcoding at a Mediterranean long-term ecological research site

   https://doi.org/10.1093/icesjms/fsab059  

   Di Capua, Iole; Piredda, Roberta; Mazzocchi, Maria Grazia; Zingone, Adriana (April 2021, ICES Journal of Marine Science)

   Fields, David (Ed.)

   Abstract Metabarcoding of environmental DNA has provided striking insights into marine microbial diversity. With this approach, we assessed the diversity of metazoan assemblages and their temporal variations at the Long-Term Ecological Research site MareChiara (LTER-MC) in the Gulf of Naples (Mediterranean Sea). The Illumina sequencing of the V4-18S rRNA fragment from 48 surface samples collected from 2011 to 2013 produced a total of 5 011 047 marine metazoan reads. The normalized dataset was generally dominated by copepods (60.3%), followed by annelids (34.7%) mostly represented by the invasive benthic polychaete Hydroides elegans. Non-copepod holoplankton was mainly represented by siphonophores, rotifers, and appendicularians, with occasional mass occurrences of jellyfish. The rest of meroplankton (mainly molluscs, annelids, and anthozoans) showed a high diversity, covering all 11 zooplankton phyla, from Porifera to Craniata. A high number of copepod genera were identified, with seasonal recurrence matching patterns observed in 30 years of studies in the Gulf of Naples. Despite limitations related to the molecular marker resolution and reference dataset, the study provided valuable insights into diversity and seasonal patterns of the whole metazoan assemblage, expanding the knowledge on rare or hardly identifiable taxa and confirming DNA metabarcoding as a powerful approach to be integrated at LTER sites. 

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3. Community structure along the Western Antarctic continental shelf and a latitudinal change in epibenthic faunal abundance assessed by photographic surveys

   https://doi.org/10.3389/fmars.2023.1094283  

   Grimes, Candace J.; Donnelly, Kyle; Ka, Cheikhouna; Noor, Nusrat; Mahon, Andrew R.; Halanych, Kenneth M. (April 2023, Frontiers in Marine Science)

   The Southern Ocean’s continental shelf communities harbor high benthic biodiversity. However, most census methods have relied on trawling or dredging rather than direct observation. Benthic photographic and videographic transect surveys serve a key role in characterizing marine communities’ abundance and diversity, and they also provide information on the spatial arrangement of species within a community. To investigate diversity and abundance in Southern Ocean benthic communities, we employed photographic transects during cruises aboard the RVIB Nathanial B. Palmer (November 2012) and the ASRV Laurence M. Gould (February 2013). One kilometer long photographic transects were conducted at 8 sites along 6,000 km of Western Antarctica from the tip of the Antarctic Peninsula to the Ross Sea from which epifaunal echinoderms, tunicates, arthropods, cnidarians, poriferans, and annelids were identified and counted allowing estimations of biodiversity. Our results do not support a latitudinal trend in diversity, but rather a decrease in abundance of macrofaunal individuals at higher latitude sites. All communities sampled on the Western Antarctic shelf were primarily dominated by ophiuroids, pycnogonids, holothuroids, and demosponges. However, the most abundant taxon across all sites was Ophionotus victoriae , followed by the symbiotic partners Iophon sp. (demosponge) and Ophioplinthus spp. (ophiuroid). Data also confirm that the Southern Ocean is composed of discretely unique benthic communities. These results provide critical understanding of the current community structure and diversity serving as a baseline as the Antarctic continental shelf changes due to rising ocean temperatures, climate change, and collapse of large ice sheets. 

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4. Patterns of in situ Mineral Colonization by Microorganisms in a ~60°C Deep Continental Subsurface Aquifer

   https://doi.org/10.3389/fmicb.2020.536535  

   Mullin, Sean W.; Wanger, Greg; Kruger, Brittany R.; Sackett, Joshua D.; Hamilton-Brehm, Scott D.; Bhartia, Rohit; Amend, Jan P.; Moser, Duane P.; Orphan, Victoria J. (November 2020, Frontiers in Microbiology)

   The microbial ecology of the deep biosphere is difficult to characterize, owing in part to sampling challenges and poorly understood response mechanisms to environmental change. Pre-drilled wells, including oil wells or boreholes, offer convenient access, but sampling is frequently limited to the water alone, which may provide only a partial view of the native diversity. Mineral heterogeneity demonstrably affects colonization by deep biosphere microorganisms, but the connections between the mineral-associated and planktonic communities remain unclear. To understand the substrate effects on microbial colonization and the community response to changes in organic carbon, we conducted an 18-month series of in situ experiments in a warm (57°C), anoxic, fractured carbonate aquifer at 752 m depth using replicate open, screened cartridges containing different solid substrates, with a proteinaceous organic matter perturbation halfway through this series. Samples from these cartridges were analyzed microscopically and by Illumina (iTag) 16S rRNA gene libraries to characterize changes in mineralogy and the diversity of the colonizing microbial community. The substrate-attached and planktonic communities were significantly different in our data, with some taxa (e.g., Candidate Division KB-1) rare or undetectable in the first fraction and abundant in the other. The substrate-attached community composition also varied significantly with mineralogy, such as with two Rhodocyclaceae OTUs, one of which was abundant on carbonate minerals and the other on silicic substrates. Secondary sulfide mineral formation, including iron sulfide framboids, was observed on two sets of incubated carbonates. Notably, microorganisms were attached to the framboids, which were correlated with abundant Sulfurovum and Desulfotomaculum sp. sequences in our analysis. Upon organic matter perturbation, mineral-associated microbial diversity differences were temporarily masked by the dominance of putative heterotrophic taxa in all samples, including OTUs identified as Caulobacter , Methyloversatilis , and Pseudomonas . Subsequent experimental deployments included a methanogen-dominated stage ( Methanobacteriales and Methanomicrobiales ) 6 months after the perturbation and a return to an assemblage similar to the pre-perturbation community after 9 months. Substrate-associated community differences were again significant within these subsequent phases, however, demonstrating the value of in situ time course experiments to capture a fraction of the microbial assemblage that is frequently difficult to observe in pre-drilled wells. 

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5. The emerging picture of a diverse deep Arctic Ocean seafloor: From habitats to ecosystems

   https://doi.org/10.1525/elementa.2023.00140  

   Ramirez-Llodra, Eva; Meyer, Heidi K; Bluhm, Bodil A; Brix, Saskia; Brandt, Angelika; Dannheim, Jennifer; Downey, Rachel V; Egilsdóttir, Hrönn; Eilertsen, Mari Heggernes; Gaudron, Sylvie M; et al (January 2024, Elem Sci Anth)

   Interest in the deep Arctic Ocean is rapidly increasing from governments, policy makers, industry, researchers, and conservation groups, accentuated by the growing accessibility of this remote region by surface vessel traffic. In this review, our goal is to provide an updated taxonomic inventory of benthic taxa known to occur in the deep Arctic Ocean and relate this inventory to habitat diversity. To achieve this goal, we collected data for Arctic metazoan deep-sea taxa from open-access databases, information facilities, and non-digitised scientific literature, limiting the collection to the area north of 66°N and below 500 m depth (excluding all shelf seas). Although notable progress has been made in understanding the deep Arctic using novel technologies and infrastructure, this data gathering shows that knowledge of deep-sea benthic Arctic communities remains very limited. Yet, through our compilation of habitat maps, we show that the Arctic contains a high diversity of geomorphological features, including slopes, deep basins, submarine canyons, ridges, and seamounts, as well as chemosynthesis-based and biogenic (biologically engineered) ecosystems. To analyse taxon richness and density, using both morphological and molecular data, we compiled 75,404 faunal records with 2,637 taxa. Phyla with the most records were the Arthropoda (21,405), Annelida (13,763) and Porifera (12,591); phyla with the most documented taxa were the Arthropoda (956), Annelida (566) and Mollusca (351). An overview of the dominant groups inhabiting the different geomorphological features highlights regions in the deep Arctic where data are particularly scarce and increased research efforts are needed, particularly the deep basins of the central Arctic Ocean. This scarcity of deep benthic Arctic biodiversity data creates a bottleneck for developing robust management and conservation measures in a rapidly changing region, leading to a call for international collaboration and shared data to ensure understanding and preservation of these fragile Arctic ecosystems. 

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