Craig R. Smith’s research while affiliated with University of Hawaii System and other places

Anthropogenic debris has been documented in Antarctica for the past 40 years. Upon breakdown, large pieces become microdebris, which reaches the seafloor through a variety of physical and biological processes. The Antarctic benthos, deeply reliant on sinking organic particles, is thus vulnerable to ingesting microdebris. By using benthic specimens sampled between 1986 and 2016 and deposited in biological collections, we provide the first record of microdebris in Southern Ocean deep-sea invertebrates. Specimens from 15 species (n = 169 organisms) had their gut content examined, with 13 species yielding microdebris in the shape of fibers (n = 85 fibers). The highest ingestion percentages were recorded in the sea cucumbers Heterocucumis steineni (100%), Molpadia violacea (83%) and Scotoplanes globosa (75%), and in the brittle star Amphioplus peregrinator (53%). Deposit-and suspension-feeding were the strategies which yielded the most fibers, accounting for 83.53% of particles. Seven fibers were identified as microplastics, composed of polyamide, polycarbonate, polyester, polyethylene terephthalate, polyisoprene and polysulfone. We also provide the earliest record of a microplastic in Antarctica, a polysulfone fiber ingested by a Boreomysis sp. mysid caught in 1986. The occurrence of fibers in the world's most remote continental margin renews concerns of pollution in seemingly isolated regions.

Glaciomarine fjords dominate the coastal margin of the West Antarctic Peninsula. Studies in similar habitats in the Arctic have shown that benthic biodiversity and ecosystem functioning in inner and middle fjord basins are reduced by turbidity and sedimentation disturbance caused by climate warming–enhanced glacial melting. In contrast, the inner and middle fjord basins along the West Antarctic Peninsula are characterized as productivity and biodiversity hotspots, but benthic ecosystem functions remain unevaluated. In 2015–2016, we conducted sediment respiration and ¹³C pulse‐chase experiments to assess benthic ecosystem functions along a five‐station transect at ~ 500–600 m depths from the inner Andvord Bay fjord, through to Gerlache Strait, and onto the open continental shelf. Incubation samples from the inner and middle basins of Andvord Bay showed peaks in background seafloor respiration, benthic biomass, and uptake of labeled algal biomass compared to more outlying stations; the continental shelf exhibited the lowest levels of these variables, as well as dissolved inorganic carbon production. Macrofaunal community uptake was responsible for most of the C processing in the inner and middle parts of the fjord (> 45%) while dissolved inorganic carbon was the dominant repository of processed C near the fjord mouth and on the continental shelf (> 80%). The inner parts of Andvord Bay are hotspots of benthic C‐cycling and metabolism, in addition to biodiversity. Ongoing climate warming is likely to negatively impact these inner‐fjord hotspots by increasing meltwater input and sedimentation disturbance, yielding a reduction in the input and recycling of labile detritus at the seafloor in the inner‐middle fjord.

Organic-rich whale bones and wood falls occur widely in the deep sea and support diverse faunal communities, contributing to seafloor habitat diversity. Changes in community structure through succession on deep-sea bone/wood substrates are modulated by ecosystem engineers, i.e., bone-eating Osedax annelids, and wood-boring Xylophaga bivalves. Here, we use a comparative experimental approach and Ocean Networks Canada’s (ONC) cabled observatory in hypoxic Barkley Canyon to study, at high temporal resolution, colonization and succession on whale-bone, Douglas fir wood, and control carbonate rock over 8.3 mo. Experimental substrates were similar in size and mounted on PVC plates near the seafloor at 890 m depth and monitored by high-definition video camera for 5-min intervals every 6-12 h over a period of 8.3 mo. A broad range of seafloor and sea-surface environmental variables were also monitored at this site over the 8.3 mo to account for environmental variability and food input. Following loss of the high-definition camera, substrates were surveyed approximately annually with lower resolution ROV video for an additional 8.5 y. We find that megafaunal abundances, species diversity, and community structure varied substantially over 8.3 mo on each substrate, with markedly different patterns on whale bones due to the development of extensive white bacterial mats. A combination of seafloor and sea surface variables explained < 35% of bone/wood community variation. Bone-eating Osedax annelids failed to colonize whale bones even after 9.2 years, and boring Xylophaga bivalves colonized the wood at much lower rates than in better oxygenated deep-sea locations. Species diversity on whale-bone and wood substrates appeared to be substantially reduced due to the absence of ecosystem engineers and the low oxygen concentrations. We hypothesize that Osedax/Xylophaga colonization, bone/wood degradation, and bone/wood community development may be limited by oxygen concentrations of 0.22 - 0.33 ml.l on the NE Pacific margin, and that OMZ expansion due to climate change will reduce whale-bone and wood degradation, and the contribution of whale falls and wood falls to beta diversity, on the NE Pacific margin.

Marine imagery is a comparatively cost-effective way to collect data on seafloor organisms, biodiversity and habitat morphology. However, annotating these images to extract detailed biological information is time-consuming and expensive, and reference libraries of consistently annotated seafloor images are rarely publicly available. Here, we present the Antarctic Seafloor Annotated Imagery Database (AS-AID), a result of a multinational collaboration to collate and annotate regional seafloor imagery datasets from 19 Antarctic research cruises between 1985 and 2019. AS-AID comprises of 3,599 georeferenced downward facing seafloor images that have been labelled with a total of 615,051 expert annotations. Annotations are based on the CATAMI (Collaborative and Automated Tools for Analysis of Marine Imagery) classification scheme and have been reviewed by experts. In addition, because the pixel location of each annotation within each image is available, annotations can be viewed easily and customised to suit individual research priorities. This dataset can be used to investigate species distributions, community patterns, it provides a reference to assess change through time, and can be used to train algorithms to automatically detect and annotate marine fauna.

The abyssal seafloor (3500–6000m) remains largely unexplored but with deep-sea mining imminent, anthropogenic impacts may soon reach abyssal communities. Thus, there is a growing need for baseline studies of biodiversity, ecosystem functioning, and connectivity in both potential mining and no-mining areas across the Clarion-Clipperton Zone (CCZ), a key target region for polymetallic nodule mining. In this study, in situ pulse-chase lander experiments were conducted for 1.5 days in three no-mining areas (called Areas of Particular Environmental Interest, or APEIs) in the western CCZ, a region with a seafloor particulate organic carbon (POC) flux gradient. A decreasing trend was seen in mean seafloor respiration, macrofaunal abundance, and biomass from the more eutrophic APEI 7 to the more oligotrophic APEI 1, although this trend was not statistically significant (p = 0.18) most likely due to small samples sizes and high variability. In this study, most (96%) of the 13C-labeled processed phytodetritus was respired within 1.5 days. Experimental uptake of phytodetritus by macrofauna and bacteria was detected but was lower than in the previously studied and more eutrophic eastern CCZ over similar time scales (1.5 d). Bacteria dominated the short-term (∼1.5 d) uptake of organic carbon at the seafloor, yet macrofauna processed more organic carbon per unit biomass than previously found in the eastern CCZ (0.003 mg C m−2 d−1 and 0.5 × 10−5 mg C m−2 d−1 for the western and eastern CCZ, respectively). Our study provides important information on C-uptake and respiration rates in areas set aside from mining in the western CCZ and suggests high variability may occur in the rates of benthic Corg-cycling across the CCZ. We recommend that benthic ecosystem functions be explored across gradients of POC flux which may be a major environmental factor driving ecosystem dynamics in the CCZ.