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Understanding the population dynamics of commercially fished deep-sea species, on seasonal to inter-annual scales, is of great importance in areas where fishing pressure is high. The remoteness of the deep-sea environment constitutes a challenge for monitoring these populations. The few studies that have investigated population structure of deep-sea species, have used trawls, a destructive approach for benthic ecosystems. The development of deep-sea observatories offers a continuous long-term presence on the seafloor. Using imagery from the Ocean Network Canada deep-sea observatory, video footage was acquired on a daily basis and analyzed to describe the population dynamics of the deep-sea crab Chionoecetes tanneri located in depths of 900–1000 m in Barkley Canyon, off Vancouver Island (BC, Canada). The objectives here were to describe the dynamics of the local population in relation to changes in environment and/or life-cycle related behaviors. Sampling sites were located along the canyon axis and on the canyon wall. Only juveniles (1–10 cm) were found at the axis site (1000 m depth) with densities varying from 0 to 144 individuals/m2. On the canyon wall (900 m depth), adults (>10 cm) were sporadically observed and densities were lower (max. 13 individuals/m2). Variation in density between the two sites reflected the observed arrival of small individuals (<2.4 cm) at the axis site in summer and autumn. Apart from a distinct migration event in January 2015, intra-annual variability in density was higher than inter-annual variability as illustrated by significant annual and sub-annual cycles of 7.5 and 3.5 months. Our results confirmed the hypothesis of ontogenic migration and provide further insight into inter-molt periodicity; we demonstrated a duration of 16 months for one crab to grow from 1.8 cm to more than 5 cm. Our findings also show a correlation between population dynamics, chlorophyll concentration, surface wave height and wind speed, suggesting that surfa

Megafaunal diversity in the deep sea shows a parabolic pattern with depth. It can be affected by factors such as low oxygen concentration, which suppresses diversity, or the presence of submarine canyons, which enhances it. Barkley Canyon, located off the west coast of British Columbia, Canada, is a submarine canyon that extends from the continental margin (200 m) into the deep ocean (2,000 m). This canyon receives drift kelp from shoreline kelp forests and contains an oxygen minimum zone (OMZ) at 500 to 1,500 m depth. Our study investigated the abundance and diversity of epibenthic megafauna over a range of depths (200–2,000 m) and oxygen concentrations (0.5–5.0 ml/L) within Barkley Canyon, as well as changes in abundance near detrital kelp. Video was collected using the remotely operated vehicle ROPOS along seven 1-km cross-canyon (i.e., across the axis of the canyon) transects and three 40-m perpendicular cross-transects over kelp. Taxonomic groups were associated with depth, temperature, and the presence of pebbles. The OMZ restricted pennatulids, and edge effects along OMZ boundaries were observed for ophiuroids. The geomorphology of the sea floor affected the distribution of taxa across the canyon, with Porifera mainly found along the walls and Echinoidea within the canyon axis. Expected richness exhibited a bimodal pattern, peaking at 300 and 2,000 m, possibly due to the combined effect of the OMZ and the submarine canyon. Echinoidea aggregated near drift kelp at 200 and 300 m. We found that faunal communities in Barkley Canyon were influenced by several confounded factors including depth, oxygen and substrate. Understanding faunal patterns is paramount with increased exploitation and a changing climate.

Coastal marine ecosystems can be managed by actions undertaken both on the land and in the ocean. Quantifying and comparing the costs and benefits of actions in both realms is therefore necessary for efficient management. Here, we quantify the link between terrestrial sediment runoff and a downstream coastal marine ecosystem and contrast the cost-effectiveness of marine-and land-based conservation actions. We use a dynamic land-and seascape model to determine whether limited funds should be directed to 1 of 4 alternative conservation actions-protection on land, protection in the ocean, restoration on land, or restoration in the ocean-to maximise the extent of light-dependent marine benthic habitats across decadal timescales. We apply the model to a case study for a seagrass meadow in Australia. We find that marine restoration is the most cost-effective action over decadal timescales in this system, based on a conservative estimate of the rate at which seagrass can expand into a new habitat. The optimal decision will vary in different social-ecological contexts, but some basic information can guide optimal investments to counteract land-and ocean-based stressors: (1) marine restoration should be prioritised if the rates of marine ecosystem decline and expansion are similar and low; (2) marine protection should take precedence if the rate of marine ecosystem decline is high or if the adjacent catchment is relatively intact and has a low rate of vegetation decline; (3) land-based actions are optimal when the ratio of marine ecosystem expansion to decline is greater than 1:1.4, with terrestrial restoration typically the most cost-effective action; and (4) land protection should be prioritised if the catchment is relatively intact but the rate of vegetation decline is high. These rules of thumb illustrate how cost-effective conservation outcomes for connected land-ocean systems can proceed without complex modelling.

Over the past 15 years, multiple areas in the North Atlantic have been closed to destructive fishing practices to protect vulnerable deep-water coral ecosystems, known to provide habitat for diverse associated fauna. Despite the growing number of conservation measures, long-term studies on the recovery of deep-water coral communities from fisheries impacts remain scarce. In the Gulf of Maine, the Northeast Channel Coral Conservation Area (NECCCA)1 was established in 2002 to protect dense aggregations of the two numerically dominant octocoral species in the region, Primnoa resedaeformis and Paragorgia arborea. To evaluate the effectiveness of the conservation measures, we monitored shifts in abundance and size of these two coral species in the shallow section (400–700 m) of the NECCCA for 12 years after the fisheries closure. We also evaluated the appropriateness of the location of the deep boundaries of the NECCCA that were placed based on a precautionary approach with limited information on coral distribution at depths >500 m. Video transects were conducted with ROV “ROPOS” in 2001, 2006, 2010 and 2014. We found potential signs of recovery from fisheries impact at some of the shallow locations in 2014: higher coral abundance and the presence of some very large colonies as well as recruits compared to 2001 and 2006. However, spatial heterogeneity was pronounced and small colonies (<20 cm) indicative of successful recruitment were not found at all sites, underscoring the need for long-term protection measures to allow full recovery of impacted coral communities. At 700–1500 m different coral taxa were dominant than at the shallow locations and coral abundance peaked between 700 and1200 m. High abundance and diversity of corals at this depth range, 8–10 km southwest of the NECCCA, suggest that an extension of the southwest boundary should be considered. Comparably low coral abundance was found at depths of 1200–1500 m inside the NECCCA indicating an appropriate initia

Deep-sea hydrothermal vents are patchily distributed ecosystems inhabited by specialized animal populations that are textbook meta-populations. Many vent-associated species have free-swimming, dispersive larvae that can establish connections between remote populations. However, connectivity patterns among hydrothermal vents are still poorly understood because the deep sea is undersampled, the molecular tools used to date are of limited resolution, and larval dispersal is difficult to measure directly. A better knowledge of connectivity is urgently needed to develop sound environmental management plans for deep-sea mining. Here, we investigated larval dispersal and contemporary connectivity of ecologically important vent mussels (Bathymodiolus spp.) from the Mid-Atlantic Ridge by using high-resolution ocean modeling and population genetic methods. Even when assuming a long pelagic larval duration, our physical model of larval drift suggested that arrival at localities more than 150 km from the source site is unlikely and that dispersal between populations requires intermediate habitats ("phantom" stepping stones). Dispersal patterns showed strong spatiotemporal variability, making predictions of population connectivity challenging. The assumption that mussel populations are only connected via additional stepping stones was supported by contemporary migration rates based on neutral genetic markers. Analyses of population structure confirmed the presence of two southern and two hybridizing northern mussel lineages that exhibited a substantial, though incomplete, genetic differentiation. Our study provides insights into how vent animals can disperse between widely separated vent habitats and shows that recolonization of perturbed vent sites will be subject to chance events, unless connectivity is explicitly considered in the selection of conservation areas.

The industrialization of the deep sea is expanding worldwide. Increasing oil and gas exploration activities in the absence of sufficient baseline data in deep-sea ecosystems has made environmental management challenging. Here, we review the types of activities that are associated with global offshore oil and gas development in water depths over 200 m, the typical impacts of these activities, some of the more extreme impacts of accidental oil and gas releases, and the current state of management in the major regions of offshore industrial activity including 18 exclusive economic zones. Direct impacts of infrastructure installation, including sediment resuspension and burial by seafloor anchors and pipelines, are typically restricted to a radius of ~100 m on from the installation on the seafloor. Discharges of water-based and low-toxicity oil-based drilling muds and produced water can extend over 2 km, while the ecological impacts at the population and community levels on the seafloor are most commonly on the order of 200–300 m from their source. These impacts may persist in the deep sea for many years and likely longer for its more fragile ecosystems, such as cold-water corals. This synthesis of information provides the basis for a series of recommendations for the management of offshore oil and gas development. An effective management strategy, aimed at minimizing risk of significant environmental harm, will typically encompass regulations of the activity itself (e.g., discharge practices, materials used), combined with spatial (e.g., avoidance rules and marine protected areas), and temporal measures (e.g., restricted activities during peak reproductive periods). Spatial management measures that encompass representatives of all of the regional deep-sea community types is important in this context. Implementation of these management strategies should consider minimum buffer zones to displace industrial activity beyond the range of typical impacts: at least 2 km from

Author Posting. © Inter-Research, 2005. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Marine Ecology Progress Series 293 (2005): 1-16, doi:10.3354/meps293001., We examined larval abundance patterns near deep-sea hydrothermal vents along the East Pacific Rise to investigate how physical transport processes and larval behavior may interact to influence larval dispersal from, and supply to, vent populations. We characterized vertical and lateral distributions and temporal variation of larvae of vent species using high-volume pumps that recovered larvae in good condition (some still alive) and in high numbers (up to 450 individuals sample–1). Moorings supported pumps at heights of 1, 20, and 175 m above the seafloor, and were positioned directly above and at 10s to 100s of meters away from vent communities. Sampling was conducted on 4 cruises between November 1998 and May 2000. Larvae of 22 benthic species, including gastropods, a bivalve, polychaetes, and a crab, were identified unequivocally as vent species, and 15 additional species, or species-groups, comprised larvae of probable vent origin. For most taxa, abundances decreased significantly with increasing height above bottom. When vent sites within the confines of the axial valley were considered, larval abundances were significantly higher on-vent than off, suggesting that larvae may be retained within the valley. Abundances of all vent species varied significantly among sample dates; the variation was not synchronized among taxa, except for consistently low abundances during November 1998. Lateral distributions did not vary among major larval groups (gastropods, polychaetes and bivalves), although polychaetes showed anomalously high abundances off-vent at 1 m above bottom. Lateral patterns also did not vary among species of gastropods, indicating that hydrodynamic processes may be transporting diverse species in similar ways. However, the species-level differences in temporal patterns indicate that there is substantial discontinuity in the abundance of individual species at vent communities, possibly due to timing of spawning and/or behavioral interactions with flow., Funding was provided by NSF grants OCE-961905 and OCE-9712233 to L.S.M., a WHOI Postdoctoral fellowship through the Doherty Foundation and NSERC Discovery Grant to A.M., and a NSERC postdoctorate fellowship to H.L.H.

The importance of species interactions in studies assessing the trace metal tolerance of individual species, has been largely overlooked. Most toxicity assessments involve single-species tests. Although relevant in some cases, this approach does not incorporate the biological environment of an organism as a factor that might influence its survival. On the other hand, this factor is incorporated in studies at the community level. However, the latter, not examining the mechanisms that drive the interactions in the community, do not allow for prediction of the outcome after the addition of a stress inducer, such as trace metals. The purpose of this study was to examine the effect of the interaction of two species of marine diatoms (Skeletonema costatum (Cleve) Greville and Nitzschia thermalis (Ehrenberg) Auerswald) on their individual copper tolerances. The two species were grown in unialgal cultures in order to determine their copper tolerance. 5. costatum did not exhibit growth above 5 x 10⁻⁷ M (pCu = 8.46) and N. thermalis above 6 x 10⁻⁷M added total copper (pCu = 8.36). Skeletonema exhibited increased growth rate and lag phase with increasing copper concentration (and decreasing pCu). On the other hand, Nitzschia demonstrated decreased growth rate. No effect on lag phase was observed for this species. No difference between the tolerances of two strains of S. costatum was observed. Both strains demonstrated unaffected growth at 1 x 10⁻⁷M (pCu = 9.16) and no growth at 1 x 10⁻⁵ M added total copper (pCu = 7.16). Subsequently, Skeletonema costatum and Nitzschia thermalis were grown together at three copper concentrations (1 x 10⁻⁹ M, 4 x 10⁻⁷M and 5 x 10⁻⁷M added total copper). In the unialgal cultures that were used as controls, the two species grew as predicted from their tolerance tests. However, in the mixed cultures, Nitzschia was the only species that exhibited growth, regardless of the copper concentration in the medium. This inhibition of Skeletonema in the pres