Description: These data represent the results of a long-term colonization experiment at the Long-Term Ecological Research observatory HAUSGARTEN. Recruitment panels were constructed from plastic and brick and deployed attached to a metal frame in 1999 at the station HG-IV (Arctic Ocean, 79 N, 04 E, 2500 m depth). The experiment was recovered in 2017. Following recovery, all invertebrates and foraminiferans on the panels were counted using a dissecting microscope on board R/V Polarstern and then saved in 95% ethanol. Species were identified by reference to published literature and taxonomic experts. Species richness was low compared to surrounding hard-bottom communities, indicating that Arctic benthic communities may take decades to develop.

Description: In 2017 - 2022, the Ocean Floor Observation System (OFOS) was used to survey epibenthic megafauna at the station HAUSGARTEN-I (79 N, 6 E, 1300 m depth). Data were collected every year except 2020 over a set transect. Images were collected automatically every 30 seconds, and additional images were collected manually when objects of interest came into view. For analysis, 90 automatically-recorded images were selected, with 30 each from the beginning, middle, and end of the transect. Images were individually viewed using the BIIGLE online image analysis tool, and all megafauna were annotated with identifications at the lowest possible taxonomic level. The area of each image was calculated using three parallel lasers mounted on the OFOS a known distance apart and visible in the images. Data represented here are the densities (individuals m^-2) for each species or morphotype in each image.

Description: Poliometra prolixa is a common species of comatulid crinoid in the Arctic deep sea. In this study, we characterize the ontogenetic development through the cystidean and pentacrinoid stages, using specimens from the LTER (Long-Term Ecological Research) observatory HAUSGARTEN in Fram Strait, Arctic Ocean. While embryos and early larval stages (e.g., the doliolaria) were not observed, adult P. prolixa were observed on a moored experimental platform at 2500 m water depth, suggesting that P. prolixa larvae do not disperse far from their mothers; doliolaria may have an abbreviated pelagic duration period or may be brooded in this species. The cystidean has a short, translucent stalk with a star-shaped attachment disc and a diamond-shaped translucent head. Metamorphosis from the cystidean to the pentacrinoid is characterized by the formation of brachial ossicles from oral ossicles and by fusion of the basal and radial ossicles to form the calyx. The pentacrinoid stalk is more opaque and develops synarthrial joints first at the distal end. Late pentacrinoids have a xenomorphic stalk, bifurcated arms with pinnules, and cirri. We discuss the niche of Poliometra prolixa and also consider the question of whether cystidean and pentacrinoid stages of comatulid crinoids should be considered larval forms.

Description: Invertebrates in polar and deep-sea environments that have complex life histories are exposed to unique environmental conditions that may favor non-pelagic development and K-strategist reproduction. Although many polar species follow this strategy, the numerically most abundant species tend to have more r-strategist life-history characteristics. We deployed artificial substrata over 3 years in the Arctic deep sea and collected hundreds of specimens of the athecate hydroid Bouillonia cornucopia. While this species has previously been described as rare, we report dense, patchy recruitment on artificial substrata, suggesting that B. cornucopia is highly opportunistic. This species has rapid growth compared to other sessile invertebrates in the study area, high fecundity, and continuous reproduction—all characteristics of an r-selected life history. The species’ gonophores are simple, lacking an obvious spadix or radial canals. We observed nurse cells in histological sections of female gonophores, but no male gonophores were observed. Gonophores break away from the blastostyles in mature specimens and appear to have fertilization envelopes, suggesting that each gonophore is composed of a single oocyte and that embryological evelopment occurs in the water column. Hydroids are typically the first invertebrates to recruit to substrata in the Arctic but are easily overgrown. The opportunistic life histories of B. cornucopia and other hydroids may be adaptive for maintaining populations in the face of high mortality. Our study demonstrates the utility of artificial substrata for collections of otherwise rare opportunistic species.

Description: © The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Mazurkiewicz, M., Meyer-Kaiser, K., Sweetman, A. K., Renaud, P. E., & Wlodarska-Kowalczuk, M. Megabenthic standing stocks and organic carbon demand in a warming Arctic. Progress in Oceanography, 196, (2021): 102616, https://doi.org/10.1016/j.pocean.2021.102616.

Description: Benthic megafauna (organisms large enough to be visible on seabed photographs) are regarded as important for carbon cycling in benthic habitats. They are a food source for many predators like fish and marine mammals and may stimulate carbon mineralization in sediment by bioturbation. However, few studies address these basic characteristics of megabenthos quantitatively. This study quantifies the spatial variability in standing stock (biomass) and functioning (secondary production, respiration and carbon demand) of benthic megafauna in fjords and on the continental shelf of Svalbard. Organisms were measured from sea bottom images to assess their biomass using length-weight relationships and volumetric methods, then respiration and production were estimated with empirical artificial neural network models. Significantly higher standing stock, secondary production, respiration, and carbon demand were found in fjords categorized as ‘cold’ (as defined by water temperature, prevailing water masses and ice-cover) than in the ‘warm’ ones. Cold fjords were dominated by Echinodermata, while in warm fjords Crustacea prevailed. All megafaunal community parameters were negatively correlated with bottom temperature. It was not possible to assess specific direct impacts of temperature, and indirect effects may be more relevant to our findings. These include temperature-driven changes in primary production, ice cover and ice-algae production or predation pressure from carnivores expanding their ranges northward. The progression of climate warming may affect megafaunal communities by reducing their biomass, production, and carbon demand and have profound effects on ecosystem functioning.

Description: Financing was provided by the University Centre in Svalbard and Akvaplan-niva (to PER), by the National Science Centre grant number UMO-2016/23/B/NZ8/02410 (AbeFun), and statutory funds of the Institute of Oceanology, Polish Academy of Sciences (to MWK).

Description: Author Posting. © Company of Biologists, 2020. This article is posted here by permission of Company of Biologists for personal use, not for redistribution. The definitive version was published in Journal of Experimental Biology 224(2), (2020): jeb.239178, https://doi.org/10.1242/jeb.239178.

Description: The swimming behavior of invertebrate larvae can affect their dispersal, survival and settlement in the ocean. Modeling this behavior accurately poses unique challenges as behavior is controlled by both physiology and environmental cues. Some larvae use cilia to both swim and create feeding currents, resulting in potential trade-offs between the two functions. Food availability is naturally patchy and often occurs in shallow horizontal layers in the ocean. Also, larval swimming motions generally differ in the horizontal and vertical directions. In order to investigate behavioral response to food by ciliated larvae, we measured their behavioral anisotropy by quantifying deviations from a model based on isotropic diffusion. We hypothesized that larvae would increase horizontal swimming and decrease vertical swimming after encountering food, which could lead to aggregation at food layers. We considered Crepidula fornicata larvae, which are specifically of interest as they exhibit unsteady and variable swimming behaviors that are difficult to categorize. We tracked the larvae in still water with and without food, with a portion of the larvae starved beforehand. On average, larvae in the presence of food were observed higher in the water column, with higher swimming speeds and higher horizontal swimming velocities when compared with larvae without food. Starved larvae also exhibited higher vertical velocities in food, suggesting no aggregation behavior. Although most treatments showed strong anisotropy in larval behavior, we found that starved larvae without food exhibited approximately isotropic kinematics, indicating that behavioral anisotropy can vary with environmental history and conditions to enhance foraging success or mitigate food-poor environments.

Description: M.H.D. and K.S.M.-K. were supported by postdoctoral scholarships from Woods Hole Oceanographic Institution, and B.T. was supported by a WHOI Summer Student Fellowship. This work was also supported by National Science Foundation grant OCE-0850419.

Description: Larval dispersal is a fundamental process responsible for colonization and connectivity of benthic invertebrate populations. It is difficult to study larval dispersal in polar environments because weather and climate conditions restrict sample collection to certain seasons. In this study, we leveraged oceanographic moorings as long-term scientific platforms for collecting larvae and recruits of benthic invertebrate species in the Fram Strait and along the continental slope north of Svalbard in 2017–2021. Larval traps and fouling panels were deployed at various depths on 15 moorings at 8 locations, and additional specimens of biofouling were obtained opportunistically from moored instruments. Our results showed a significant difference in species composition between samples collected in Atlantic Water in the West Spitsbergen Current (WSC) and samples collected in Arctic Water near the seafloor and in the East Greenland Current (EGC) in the western part of the Fram Strait. There was also a stark difference between Atlantic Water species in the Fram Strait and on the north Svalbard slope. Most specimens collected in the WSC belonged to species with long-duration planktotrophic larvae, such as the ubiquitous bivalve Hiatella arctica, the bryozoan Alcyonidium mamillatum, and two nudibranchs. Samplers exposed primarily to Arctic water at their given depth and location were dominated by hydrozoans. We observed medusae budding off of the hydroids Stegopoma plicatile and Rhizoragium roseum. Our study demonstrates that the WSC is an important vector for larval dispersal into the central Arctic Ocean. Integration of biological samplers on oceanographic moorings holds great promise for monitoring efforts as climate change progresses, especially in environments where research is challenging and seasonally limited, such as the Arctic. 1. Introduction For benthic invertebrates, especially those with sessile adult stages (e.g., sponges, anemones), larval dispersal is the primary mechanism of dispersal to new habitats (Pechenik, 1999). The patterns and mechanisms of larval dispersal are difficult to study in the Arctic Ocean, where weather and climate conditions restrict sample collection to summer months. As a result, larval dispersal and the subsequent processes of settlement and recruitment in benthic invertebrates are poorly understood in the Arctic Ocean, despite their importance. Oceanographic moorings provide excellent platforms for studying larval dispersal, recruitment, and growth of organisms (Chava et al., 2021; Schiaparelli and Aliani, 2019). Instruments and floats on a mooring are deployed in the water column by design, so the