Search

Marine ecosystems and their associated biodiversity sustain life on Earth and hold intrinsic value. Critical marine ecosystem services include maintenance of global oxygen and carbon cycles, production of food and energy, and sustenance of human wellbeing. However marine ecosystems are swiftly being degraded due to the unsustainable use of marine environments and a rapidly changing climate. The fundamental challenge for the future is therefore to safeguard marine ecosystem biodiversity, function, and adaptive capacity whilst continuing to provide vital resources for the global population. Here, we use foresighting/hindcasting to consider two plausible futures towards 2030: a business-as-usual trajectory (i.e. continuation of current trends), and a more sustainable but technically achievable future in line with the UN Sustainable Development Goals. We identify key drivers that differentiate these alternative futures and use these to develop an action pathway towards the desirable, more sustainable future. Key to achieving the more sustainable future will be establishing integrative (i.e. across jurisdictions and sectors), adaptive management that supports equitable and sustainable stewardship of marine environments. Conserving marine ecosystems will require recalibrating our social, financial, and industrial relationships with the marine environment. While a sustainable future requires long-term planning and commitment beyond 2030, immediate action is needed to avoid tipping points and avert trajectories of ecosystem decline. By acting now to optimise management and protection of marine ecosystems, building upon existing technologies, and conserving the remaining biodiversity, we can create the best opportunity for a sustainable future in 2030 and beyond.

Autoimmune inflammatory arthritides (AIA), such as psoriatic arthritis and rheumatoid arthritis, are chronic systemic conditions that affect multiple joints of the body. Recently, total-body (TB) PET/CT scanners exhibiting superior technical characteristics (total-body coverage, geometric sensitivity) that could benefit AIA evaluation, compared with conventional PET/CT systems, have become available. The objectives of this work were to assess the performance of an ultra-low-dose, (18)F-FDG TB PET/CT acquisition protocol for evaluating systemic joint involvement in AIA and to report the association of TB PET/CT measures with joint-by-joint rheumatologic examination and standardized rheumatologic outcome measures. Methods: Thirty participants (24 with AIA and 6 with osteoarthritis) were prospectively enrolled in this single-center, observational study. All participants underwent a TB PET/CT scan for 20 min starting at 40 min after intravenous injection of 78.1 ± 4.7 MBq of (18)F-FDG. Qualitative and quantitative evaluation of (18)F-FDG uptake and joint involvement were performed from the resulting images and compared with the rheumatologic assessments. Results: TB PET/CT enabled the visualization of (18)F-FDG uptake at joints of the entire body, including those of the hands and feet, in a single bed position, and in the same phase of radiotracer uptake. A range of pathologies consistent with AIA (and non-AIA in the osteoarthritis group) were visualized, and the feasibility of extracting PET measures from joints examined by rheumatologic assessments was demonstrated. Of 1,997 evaluable joints, there was concordance between TB PET qualitative assessments and joint-by-joint rheumatologic evaluation in the AIA and non-AIA cohorts for 69.9% and 91.1% joints, respectively, and an additional 20.1% and 8.8% joints, respectively, deemed negative on rheumatologic examination showed PET positivity. On the other hand, 10.0% and 0% joints in the AIA and non-AIA cohorts, respectively, were positive on rheumatologic evaluation but negative on TB PET. Quantitative measures from TB PET in the AIA cohort demonstrated a moderate-to-strong correlation (Spearman ρ = 0.53–0.70, P

One of the most pronounced effects of climate change on the world’s oceans is the (generally) poleward movement of species and fishery stocks in response to increasing water temperatures. In some regions, such redistributions are already causing dramatic shifts in marine socioecological systems, profoundly altering ecosystem structure and function, challenging domestic and international fisheries, and impacting on human communities. Such effects are expected to become increasingly widespread as waters continue to warm and species ranges continue to shift. Actions taken over the coming decade (2021–2030) can help us adapt to species redistributions and minimise negative impacts on ecosystems and human communities, achieving a more sustainable future in the face of ecosystem change. We describe key drivers related to climate-driven species redistributions that are likely to have a high impact and influence on whether a sustainable future is achievable by 2030. We posit two different futures—a ‘business as usual’ future and a technically achievable and more sustainable future, aligned with the Sustainable Development Goals. We then identify concrete actions that provide a pathway towards the more sustainable 2030 and that acknowledge and include Indigenous perspectives. Achieving this sustainable future will depend on improved monitoring and detection, and on adaptive, cooperative management to proactively respond to the challenge of species redistribution. We synthesise examples of such actions as the basis of a strategic approach to tackle this global-scale challenge for the benefit of humanity and ecosystems. Supplementary Information The online version contains supplementary material available at 10.1007/s11160-021-09641-3.

International audience; Predation is potentially an influential source of early post-settlement mortality of benthic marine invertebrates, but previous studies demonstrate conflicting results. We investigated the effect of large predators on developing subtidal invertebrate communities in cobble-filled collectors in the southwest Bay of Fundy, Canada. Two predation treatments (exclusion of predators ≥ 7 mm body width or full access for predators < 50 mm) were used to test the effect of large predators, and a partial-cage control tested for caging artefacts. Despite a reduction in the abundance and biomass of large predators, multivariate analyses indicated no effect of predator exclusion on the composition of the prey and micropredator communities. Results indicated that the largest differences were between the predator-access treatment and the other two treatments, which was potentially influenced by the caging material. There were significant but weak positive correlations between the micropredator and the other two communities. Previous studies indicate that at low predation intensity, as seemed to be the case here, other factors may play a stronger role in controlling recruit abundance. Predation control probably varies spatially and temporally, and the influence of large predators was not likely the driving force for early post-settlement mortality in the invertebrate communities measured in this study.

Soft-shell clams (Mya arenaria) can serve important ecological roles in intertidal mudflats and are an important economic and recreational resource in the northwestern Atlantic. However, environmental factors affecting newly-settled and juvenile clam abundances within a given settlement season remain uncertain. We conducted a field study assessing relationships between juvenile soft-shell clam abundance and spatial, temporal, and environmental variables in coastal mudflats of the northern shore of the Bay of Fundy. Sediment pH and low-tide water temperature (tide pools) were monitored in situ on a biweekly–monthly basis over the course of the M. arenaria settlement season in 2012 at four study sites to quantify diel variation in sediment pH and temperature. Core samples were also collected to quantify M. arenaria (

Examination of spatial patterns of organisms in the rocky subtidal zone is logistically challenging, particularly over large geographic distances. In the present study, we describe patterns of richness and abundance of decapod crustaceans and small demersal fishes colonizing cobble-filled bio-collectors in 2008 and 2009 at nearshore sites across an important oceanographic and biogeographic gradient in the North-west Atlantic from Rhode Island, USA to Newfoundland, Canada. At least 17 decapod and 24 fish genera were caught, including cryptic fish taxa not readily sampled with other gear. Species richness and abundance of decapods and fishes in collectors at shallow sites (5–10 m) was similar among nearby sites and was greatest in the southernmost region, but did not follow a simple latitudinal cline. The lack of clear latitudinal patterns is likely to be a result of the complex geography of summer temperatures along this coast, with the lowest temperatures at the mouth of the Bay of Fundy, the cent...

While ocean acidification (OA) effects on marine organisms are well documented, impacts of sediment acidification on infaunal organisms are relatively understudied. Here we synthesize CO2-driven sediment acidification effects on infaunal marine bivalves. While sediment carbonate system conditions can already exceed near-future OA projections, sediments can become even more acidic as overlying seawater pH decreases. Evidence suggests that infaunal bivalves experience shell dissolution, more lesions, and increased mortality in more acidic sediments; effects on heavy metal accumulation appear complex and uncertain. Infaunal bivalves can avoid negative functional consequences of sediment acidification by reducing burrowing and increasing dispersal in more acidic sediments, irrespective of species or life stage; elevated temperature may compromise this avoidance behaviour. The combined effects of sediment acidification and other environmental stressors are virtually unknown. While it is evident that sediment acidification can impact infaunal marine bivalves, more research is needed to confidently predict effects under future ocean conditions.

Although ocean acidification will impact marine organisms in the future, few studies have addressed the effects of sedimentary porewater acidification on benthic invertebrates. This study suggests that burrowing behavior and post-settlement dispersal of juvenile bivalves are altered by porewater acidification under present day conditions. We tested the efficacy of a novel method of stabilizing porewater pH using sediment underlain with food grade gelatin in both the lab and field, and then employed this method to test if porewater acidification could alter post-settlement clam dispersal under natural conditions. In the field, clams were exposed to a gradient of porewater acidification in manipulated (CO2 added) sediments for 24 h to determine if acidification could alter dispersal patterns of juvenile clams under natural flow conditions; juvenile clam dispersal in the presence of different buffer types was also tested. In addition, juvenile clams were placed on unmanipulated, field-collected sediment cores in the lab which varied naturally with respect to acidification to test burrowing behavior in response to natural porewater pH. Gelatin stabilized porewater pH for 24–48 h and its presence did not influence clam burrowing behavior. In the field, a significant negative relationship between the percent of clams dispersed and acidification was observed, while stabilizing porewater pH significantly decreased clam dispersal. In the lab, there was a significant positive relationship between the percent of clams burrowed and porewater acidification. This study suggests that porewater acidification has the capacity to alter the burrowing behavior and dispersal patterns of juvenile bivalves under natural conditions.

In soft-bottom habitats, post-settlement dispersal of infaunal organisms can be important in population connectivity and turnover. However, this phase of dispersal is often overlooked and understanding of how spatial and temporal variability in biophysical processes drives dispersal in the field is lacking. To quantify spatial and temporal variability in post-settlement dispersal of bivalves, we conducted a study at three sites in Whangarei Harbour, New Zealand. At each site on two separate occasions, we stained the sediment and infauna in 2 m diameter plots with fluorescein to measure the post-settlement dispersal of the clam, Austrovenus stutchburyi (Gray). Dispersal was quantified by monitoring changes in the abundance of non-fluorescent individuals within the plots and fluorescent individuals outside the plots. Our experiments show that some A. stutchburyi were able to disperse at least 50 cm into the plots within 1 tidal cycle (12 h). Dispersal was size dependent, with adult A. stutchburyi dispersing less than juveniles. Post-settlement dispersal varied both spatially and temporally, as indicated by both the change in abundance of non-fluorescent individuals in the plots through time, and the turnover rate within the plots. Dispersal was greatest at the most wave exposed site, and during a storm event. By replicating an experiment in both space and time, our results demonstrate the variability in bivalve dispersal in the field setting. Through the use of fluorescein staining in situ, this study is one of the few that provides estimates of population turnover due to post-settlement dispersal in undisturbed communities.

The availability of suitable substrate for settlement can alter the behaviour of larvae of benthic marine invertebrates and consequently their settlement patterns. We tested the effect of the background substrate of a site (rocky vs sediment) on recruitment of invertebrates settling into standardized cobble-filled collectors deployed at shallow subtidal sites in the south-western Bay of Fundy, Canada, in 2009 and 2010. The assemblage of invertebrates that settled into the collectors differed significantly in both abundance and species composition between “paired sites” (≈0.003–0.009 km2 in area and 345–861 m apart) with rocky vs sediment background substrate, and markedly less so between paired sites comprised of rocky bottom. Species that are known to be rock-dwelling recruited in greater abundance to cobble-filled collectors at rocky sites, while those known to be sediment-dwelling recruited more to cobble-filled collectors at sediment sites. At the smaller spatial scale of patches of sediment within one site (14–107 m apart), differences in abundance but not species composition were detected between collectors on the two types of background substrate. This study supports the idea that larvae of some species of marine invertebrates respond to substrate at a larger spatial scale than their immediate location of settlement.

There is limited understanding of the relationship between mobile gear fishing intensity and the magnitude of the resulting perturbation in marine benthic communities. Theory predicts that instantaneous fishing-induced mortality should generally scale directly with fishing intensity. This study used a before–after-impact experimental design with 16 fishing intensity levels to assess the impact of scallop dredging on benthic communities at two experimental sites. Few instances of statistically significant effects of fishing intensity were detected for individual taxa, although there was some evidence of impacts on community structure at one site. In contrast, short-term natural abundance fluctuations were much more prevalent and were of a magnitude similar to that estimated to be produced by fairly intense fishing, as would occur in only very limited geographic areas in the commercial fishery. Post-hoc simulations used to estimate the statistical power of the study suggest that true effects of elevated fishing mortalities could reasonably be detected, but that power was low for small instantaneous fishing mortalities. This situation is comparable to other well-designed mobile gear impact studies that reported power. The simulations also revealed comparable levels of statistical power for correctly detecting abundance changes due to fishing and due to natural fluctuations. The results of this study taken in the context of the commercial fishery suggest that impacts of scallop dredging on the local benthic communities are small with respect to natural variation in the ecosystem. This study highlights the need to account for natural spatio-temporal variation in the designs of studies of mobile fishing gear impacts. Failure to do so increases the risk of drawing incorrect conclusions.

Sediment acidification is known to influence the burrowing behaviour of juvenile marine bivalves. Unlike the alteration of behaviour by ocean acidification (OA) observed in many marine organisms, this burrowing response to present-day variation in sediment pH is likely adaptive in that it allows these organisms to avoid shell dissolution and mortality. However, the consequences of global climate stressors on these burrowing responses have yet to be tested. Further, while neurotransmitter interference appears to be linked to the alteration of behaviour by OA in marine vertebrates, the mechanism(s) controlling the burrowing responses of juvenile bivalves in response to present-day variation in sediment acidification remain unknown. We tested the interactive effects of elevated seawater temperature and sediment acidification on juvenile soft-shell clam burrowing behaviour (measured as the proportion of clams burrowed into sediment) to test for effects of elevated temperature on bivalve burrowing responses to sediment acidification. We also examined whether GABAA-like receptor interference could act as a potential biological mechanism underpinning the burrowing responses of these clams to present-day variation in sediment acidification. Results showed that both elevated temperature and gabazine administration reduced the proportion of clams that avoided burrowing into low pH sediment. These results suggest that CO2 effects on neurophysiology (GABAA receptors) can act to mediate adaptive behaviours in juvenile marine bivalves to elevated CO2, but that these behaviours may be adversely affected by elevated temperature.

Although ocean acidification is expected to reduce carbonate saturation and yield negative impacts on open-ocean calcifying organisms in the near future, acidification in coastal ecosystems may already be affecting these organisms. Few studies have addressed the effects of sedimentary saturation state on benthic invertebrates. Here, we investigate whether sedimentary aragonite saturation (Ωaragonite) and proton concentration ([H+]) affect burrowing and dispersal rates of juvenile soft-shell clams (Mya arenaria) in a laboratory flume experiment. Two size classes of juvenile clams (0.5–1.5 mm and 1.51–2.5 mm) were subjected to a range of sediment Ωaragonite and [H+] conditions within the range of typical estuarine sediments (Ωaragonite 0.21–1.87; pH 6.8–7.8; [H+] 1.58 × 10− 8–1.51 × 10- 7) by the addition of varying amounts of CO2, while overlying water pH was kept constant ~ 7.8 (Ωaragonite ~ 1.97). There was a significant positive relationship between the percent of juvenile clams burrowed in still water and Ωaragonite and a significant negative relationship between burrowing and [H+]. Clams were subsequently exposed to one of two different flow conditions (flume; 11 cm s− 1 and 23 cm s− 1) and there was a significant negative relationship between Ωaragonite and dispersal, regardless of clam size class and flow speed. No apparent relationship was evident between dispersal and [H+]. The results of this study suggest that sediment acidification may play an important role in soft-shell clam recruitment and dispersal. When assessing the impacts of open-ocean and coastal acidification on infaunal organisms, future studies should address the effects of sediment acidification to adequately understand how calcifying organisms may be affected by shifting pH conditions.

Recruitment patterns of marine bivalves are influenced by pre-settlement, settlement and post-settlement factors. Settlement patterns of the soft shell clam, Mya arenaria, were recorded at multiple tidal heights at Mill Cove, New Brunswick. It was found that the initial settlement of M. arenaria occurred at all locations on the shore and was significantly related to adult abundance and sediment grain size. At all transects there was a decrease in abundance of M. arenaria within the first month after settlement, but not all transects showed a similar decrease. While predation likely contributed to the decrease in abundance at all locations on the shore, post-settlement dispersal was an important factor in determining changes in distribution of the juvenile bivalves on the shore. By utilizing bedload traps, spatial variation in the movement of both sediment and M. arenaria was quantified. Transplants of stained clams quantified immigration and emigration rates and showed there was emigration away from the low transects, but no net movement at the high transects on the shore. Dispersal rates of recently settled M. arenaria are generally linked to sediment movement. At Mill Cove, tracking of sediment indicated that the movement of sediment increased from 1–2 m day− 1 in the high intertidal to 5–8 m day− 1 in the low intertidal, and all movement was in a shoreward direction. This study demonstrates that post-settlement dispersal can greatly affect the distribution of juvenile bivalves on an intertidal shore.

Sea urchins can have important ecological effects on benthic communities through their aggregation and feeding behaviour. Urchin movement has been demonstrated to be negatively affected by wave action, but the impact of unidirectional tidal currents on urchin movement has not been investigated. This study examines the effect of unidirectional water velocity on the direction of displacement and movement rate of the green sea urchin, Strongylocentrotus droebachiensis. In laboratory flume experiments there was a clear effect of water currents on the displacement of sea urchins. At speeds ≤30 cm s−1 urchins moved across the current in a downstream direction, but at speeds of ≥36 cm s−1 the urchins switched directions by more than 90° and moved across the current in an upstream direction. There was a significant effect of flow speed on urchin movement speed, with urchin movement speed decreasing as water current speed increased.

While ocean acidification (OA) effects on marine organisms are well documented, impacts of sediment acidification on infaunal organisms are relatively understudied. Here we synthesize CO

Early post-settlement events can have a large impact on the successful recruitment of benthic invertebrates. A field caging experiment was conducted in 2007 to examine whether preda- tion by, and/or competition with, small macrofauna affects mortality or growth of recently settled sea urchins Strongylocentrotus droebachiensis or sea stars Asterias spp. Kelp was added to half of the sea urchin cages to test whether the addition of this food source (including its associated biofilms) altered growth or survival. Sea urchins survived 25% better in cages where the other organisms were removed, indicating that predation or bulldozing likely plays an important role. The growth of sea urchins was greatest in cages without other organisms and lowest in cages with other organisms and with food, possibly indicating competition that affects sea urchin behaviour. Sea stars showed the opposite trend in survival. A greater proportion of sea stars survived in cages where the other organ- isms were present (31.3 vs. 11.5%), presumably due to them being a food source for the sea stars, indicating that starvation, cannibalism and/or competition for food are likely important for recent set- tlers of this taxon. The declines in abundance in the cages were greater than those in the natural environment for sea urchins, but similar for sea stars, suggesting that caution is required when extrapolating experimental results to the field. These results indicate that multiple factors, which dif- fer between these species, affect early post-settlement growth and mortality.

Recruitment patterns of marine invertebrates are affected both by settlement and early post-settlement events. This study examined the settlement and recruitment patterns of echinoderms at three sites in the rocky subtidal zone of Bocabec Cove, Bay of Fundy, Canada using artificial turf collectors and quadrats on the natural substrate. Potential predators were quantified at two of the sites along transects and in 1-m2 quadrats. Both potential predators and competitors were quantified in 0.0625-m2 quadrats. Settlement varied across sites (1.5–3 km apart) and two years of sampling (2004, 2005). The site of most potential settlement differed for the three groups of echinoderms: sea urchins (Strongylocentrotus droebachiensis), sea stars (Asterias spp.) and sea cucumber (Psolus fabricii). Settlement densities on the artificial turf collectors tended to be greater than the densities of settlers on the natural substrate. On the natural substrate, the only significant difference between densities of juveniles over time was that newly settled sea stars were found in July and were not found the following October. Large lobsters and carnivorous worms were potential predators with densities that varied between sites. Potential competitors that differed in abundance between sites were herbivorous gastropods and conspecifics for sea urchins; and carnivorous worms for sea stars. This study suggests that patterns of recruitment are either set up by patterns of settlement or by events during the first few weeks/months on the benthic substrate for these echinoderms.

The potential consequences of bedload transport of postlarvae for patterns of distribution of marine invertebrates were explored by developing a bedload transport model for juvenile bivalves in a small estuary in New Jersey, USA. A simple numerical model of tidal current hydrodynamics was developed based on field measurements of shear stresses near the bottom. Burrowing behavior of bivalves was incorporated into the model of bedload transport by using estimates of entrainment rates of Gemma gemma and Mya arenaria in a laboratory flume, and jump lengths of the bivalves were estimated by methods previously developed for noncohesive particles. Based on the flood domination and strong gradient of shear stresses in the Navesink estuary, our model predicted that juvenile bivalves would accumulate in the center of the estuary, traveling up to several kilometers over 30 days. Field distributions of juvenile bivalves were consistent with the model predictions for other species of bivalves but not for G. gemma, for which field distributions of both 500-μm individuals were concentrated in the eastern end of the estuary. Differences between the bedload model and G. gemma distributions suggest that spatial variation in burrowing behavior or biological interactions are playing an important role in maintaining distribution patterns of this species in spite of high levels of bedload transport. This modeling approach is applicable to other juvenile benthic invertebrates that disperse as bedload and is a useful model against which to compare field observations of rates of transport and patterns of distribution and abundance.

Although it is recognized that many species of benthic invertebrates continue to disperse after settlement, particularly in soft-bottom habitats, the scale over which movements of juveniles occur is not well known. This study combined laboratory flume experiments assessing the effects of clam size, species, and water velocity on rates and distances of dispersal of three species of juvenile bivalves with field measurements of loss rates and distances of dispersal of transplanted bivalves in the Navesink River estuary in New Jersey, USA. Dispersal distances measured in the laboratory ranged from an average of 1.6 to 40 cm h− 1 depending on clam size, species, and flow speed. Distances and likelihood of dispersal were generally greater for Mya arenaria than for Mercenaria mercenaria or Gemma gemma, although differences between species were not consistent. As predicted, smaller (1.3 mm) M. arenaria tended to disperse more than larger (3.7 mm) ones, although no significant differences were detected between two sizes (1.8 and 3.4 mm) of M. mercenaria. The similarity of the erosion thresholds of dead clams across sizes and species suggests that burrowing behaviour plays an important role in determining variation in dispersal due to clam size and species. In the field, densities of clams (M.arenaria and M.mercenaria) were reduced to half of that in controls after 3.5–5 h, indicating high levels of dispersal and/or mortality. Some individuals were recovered up to 50 cm away from their initial locations. Overall, our results suggest that dispersal distances of these three species due to bedload transport are likely to be on the order of centimeters per hour. Although these dispersal distances are small, such movements are likely to occur frequently due to tidal currents and, consequently, may have profound impacts on patterns of abundance and distribution.

To examine the roles of settlement and early postsettlement processes in the recruitment of the soft-shell clam, Mya arenaria, abundance of recent settlers and juveniles was monitored over two field seasons at four locations on the northern shore of the Bay of Fundy in New Brunswick, Canada. Results showed great spatial and temporal variability in patterns of settlement. M. arenaria appeared to become highly vulnerable to postsettlement processes at a shell length of approximately 2 mm. Postsettlement processes drastically altered patterns of settlement less than 1 year after they were established. Results suggest that local factors at specific sites within the Bay of Fundy, such as hydrodynamics, larval behavior, and early postsettlement events, likely control the abundance of juvenile clams. Additionally, postsettlement events are extremely important in shaping M. arenaria populations in this area. Very few mature adult clams greater than 50 mm in shell length were found at any sampling sites, and no relationship was found between abundance of setters and density of juveniles and adults.

Many species of benthic marine invertebrates, including bivalves, continue to disperse as juveniles (post-settlement). This dispersal has the potential to alter patterns set up at the time of settlement. Great spatial and temporal variability in rates of dispersal of juvenile bivalves has been observed in the field. We made synoptic measurements of current speeds and rates of bedload trans- port of sediment and dispersal of juvenile bivalves in the Navesink estuary, New Jersey, USA to examine the contribution of spatial and temporal variation in current speed to dispersal patterns. Daily rates of juvenile bivalve dispersal were high and varied strongly across sites. Bivalve dispersal was positively related to rates of sediment transport and current velocities, but not significantly to ambient density of bivalves. Variability in bivalve dispersal across dates was considerably less than that across sites, likely because tidal current speeds varied less by date than by site. The strong rela- tionship between bivalve dispersal and sediment transport and velocity suggests that dispersal of the bivalve species in this estuary is initiated by sediment transport.

Designing an effective environmental monitoring system for population responses requires knowledge of the biology of appropriate sentinel species and baseline information on the area's physical and chemical characteristics. This study collected information in Saint John Harbor, NB, Canada, for two abundant marine benthic invertebrates, the Atlantic nut clam (Nucula proxima) and the catworm (Nephtys incisa) to characterize their seasonal and spatial variability, determine the ideal sampling time and methods, and develop baseline data for future studies. We also evaluated whether contamination is impacting invertebrates by comparing sediment metal concentrations to responses of benthic infauna. Metals were generally below sediment quality guidelines except for nickel and arsenic. Clam densities were variable between sites but not seasons, whereas catworm densities were not significantly different between sites or seasons. Overall, these species show potential for environmental monitoring, although investigation at more contaminated sites is warranted to assess their sensitivity.

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 recov- ered 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, sug- gesting that larvae may be retained within the valley. Abundances of all vent species varied signifi- cantly 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, indicat- ing 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.

Erosion and transport of juvenile benthic invertebrates, including bivalves, has the potential to alter patterns of distribution and abundance during the early postsettlement period. Field observations indicate that there is often great spatial variability in rates of transport of juvenile bivalves. Differences in transport among sites may arise from both physical and biological causes, including variation in water flow, sediment grain size, and the local biological community. In this study, an experiment was conducted in a laboratory flume to examine the effect of sediment source (4 subtidal sites in the Navesink River estuary, New Jersey, USA) and flow velocity on rates of trans- port of juvenile Mya arenaria and Gemma gemma. Rates of erosion of M. arenaria were significantly related to sediment volume eroded, suggesting that dispersal at high flow speeds is linked to bedload transport. Sediment erosion and clam transport was lower for sediment cores from the 2 sites where the sediment was covered by a mat of amphipod Ampelisca abdita tubes. Reduction of the tube mat resulted in a small but significant increase in sediment erosion. The results of this study and compar- ison of shear velocities between the laboratory and the field suggest that both the presence of an amphipod mat and low shear velocities will result in low rates of transport of sediment and juvenile clams in the field.

Erosion and transport of juvenile benthic invertebrates, including bivalves, have the potential to alter patterns of distribution and abundance during the early post-settlement period. However, the factors influencing rates of postlarval dispersal are not well understood. Both hydrodynamics and behaviour (e.g. burrowing) are likely to play a role in determining patterns of transport of juvenile bivalves. To determine the relationship between sediment transport and bivalve dispersal, experiments were conducted in a racetrack flume to examine the effect of grain size, flow, and clam size on rates of erosion of two species of juvenile clams (Mya arenaria and Mercenaria mercenaria). Results of the experiments were compared to predictions of erosion thresholds based on the physical characteristics of the sediment and clams. Erosion of Mercenaria was greater than Mya, the opposite of predictions based on Mercenaria's greater density, indicating the importance of burrowing behaviour. In most cases, erosion also was greater in the finer sand, in contrast to the predicted similarity of erosion thresholds of the two sediments. However, clam erosion did increase with increasing shear velocity and decrease with clam size, as expected. The results of this study indicate that both hydrodynamics and behaviour play roles in the transport of these two species of juvenile bivalves and that their vulnerability to passive erosion cannot be predicted solely from knowledge of sediment transport.

The authors examined the impact of pharmaceutical companies' advertisements on college students' perceptions of depression and concomitant treatment with antidepressants among 13 male and 31 female undergraduates from a midwestern university. The students were randomly assigned to groups that read either pharmaceutical company advertisements or scientific information about depression and its treatment. The analysis revealed that 40% of the women in the advertisement condition as opposed to 1 woman (6%) in the scientific condition rated themselves as having mild, moderate, or severe depression on the Beck Depression Inventory, second edition. Women in the advertisement condition were significantly more likely to believe that depression required treatment with antidepressant medication and were more willing than women in the scientific condition to suggest antidepressant treatment to others.

Three species of vestimentiferans are found at hydrothermal vents on the East Pacific Rise (EPR). Tevnia jerichonana is an early colonist and Riftia pachyptila has the greatest biomass in established vent assemblages, but the role of Oasisia alvinae, a small species that occurs sporadically, is unknown. Anecdotal evidence suggests that O. alvinae may be abundant in the microhabitat underneath mussels. Previous studies have suggested that early T. jerichonana colonists may facilitate settlement of the late colonist R. pachyptila. To address potential mechanisms for the successional sequence and to explore the role of O. alvinae, we examined the effects of the presence of vestimentiferan (R. pachyptila and T. jerichonana) tubes and mussel (Bathymodiolus thermophilis) shell cover on recruitment of vestimentiferans on basalt blocks deployed at 9°50′N, 104°17′W on the EPR. A molecular assay was used to identify individuals to species since they were too small to be identified morphologically. Although colonists in both experiments belonged to all three species of vestimentiferans, only a few were T. jerichonana. Colonization of vestimentiferans did not increase in the presence of vestimentiferan tubes. The presence of mussel shell cover did not influence the proportions of R. pachyptila and O. alvinae, or the total number of colonists. Because the experimental blocks in this study were placed within dense clumps of R. pachyptila, we suggest that, while T. jerichonana may be an important cue for vestimentiferans settling at new vents, adult R. pachyptila also can act as a settlement cue for larvae. O. alvinae colonists were abundant in all of the treatments in our experiments, indicating that, although adults of this species are apparently rare at these sites, O. alvinae can settle in abundance if a suitable micro-environment is available.

During the early post-settlement period, dispersal and predation can drastically alter patterns of distribution and abundance of benthic invertebrates. These 2 processes may interact if predators cause disturbance and alter rates of transport of juvenile clams. In this study, experiments were conducted in an annular flume to examine the effect of 2 epibenthic predators, the seven-spine bay shrimp Crangon septemspinosa and juveniles of the green crab Carcinus maenas, on rates of ero- sion and mortality of juvenile soft shell clams Mya arenaria. Clams were exposed to 2 flow speeds (u =9 cm s -1 , shear velocity u * = 0.30 cm s -1 and u = 27 cm s -1 , u * = 0.97 cm s -1 ) in the presence and absence of predators. Erosion of sediment and clams, and formation of ripples occurred at the high- flow velocity only in the presence of shrimp. This also occurred when shrimp disturbed the sediment prior to the experimental run, suggesting that shrimp activity changed bottom topography and the erosion threshold of the sediment. Juvenile green crabs caused less disturbance of the sediment and their activities did not result in transport of sediment or clams. Gut content analysis indicated that juvenile green crabs preyed on juvenile M. arenaria. Shrimp preyed on clams in 1 of 2 experiments, probably due to a difference in size of clams between experiments (shell length = 1.0 vs. 3.0 mm). This study demonstrates that, in addition to causing mortality, predators can indirectly affect their prey by causing transport of sediment and associated small benthic invertebrates.

To examine the roles of settlement and early post-settlement processes in patterns of recruitment of the soft shell clamMya arenaria, abundance of juvenileMya at three intertidal sites in Barnstable Harbor, Massachusetts, was monitored over two settlement seasons. Two peaks of settlement occurred in 1998 (July and September) and one peak was recorded in June 1999, indicating that a late season settlement event is not a consistent feature at this site. Abundance of recent settlers (i.e., early recruits, 3-mm shell length at the end of the settlement season (up to 60 m−2) indicated large losses of individuals during the early post-settlement period. This study demonstrates that spatial patterns inMya abundance can change substantially during the early post-settlement period, and that high mortality rates can result in cohorts contributing little to the population size even when rates of settlement are high.

Rates of mortality and transport of newly settled benthic invertebrates can be very high and potentially have profound effects on patterns of recruitment. We used the soft shell clam Mya arenaria as a model organism to compare the magnitude of rates of postlarval transport and predation on juveniles. We hypothesized that there is a critical size below which spatial variation in abundance of juvenile Mya is hydrodynamically controlled and above which abundance is mainly influenced by mortality, particularly due to epibenthic predators. To test this hypothesis, we examined transport and predation of early juvenile Mya in Barnstable Harbor, Massachusetts, USA. A caging experiment demonstrated that exclusion of epibenthic predators had a large impact on the density and size distribution of juvenile Mya within a few weeks of settlement and disproportionately affected juveniles of >2-mm shell length. Enclosure of the green crab Carcinus maenas changed the size distribution of Mya but did not significantly affect abundance. We attributed the effect of predator exclusion primarily to juvenile green crabs and fish. Current meter measurements suggested that tidal currents were strong enough to cause bedload transport of sediment and Mya. Measurement of gross and net rates of transport of Mya, using bedload traps and pans of defaunated sediment, confirmed that juveniles up to 5-mm shell length were routinely redistributed by tidal currents, particularly during spring tides. The number of postlarval Mya transported varied among sites and dates and was significantly related to ambient density of Mya and sediment flux. The loss of Mya during the caging experiment was compared to the rate of net flux of Mya due to transport during an intermediate tide. This comparison suggested that the loss due to predation was considerably larger than the flux due to transport for individuals >2 mm, but that rates of the two processes were more similar for individuals

Within any particular landscape, patch structure and dynamics likely will differ among habitat types because of environmental differences influencing the intensity and outcome of biological interactions. We compared the dynamics of natural and experimentally constructed mussel patches (Mytilus trossulus and M. edulis) in two intertidal habitats, tidepools and emergent rock, over a time series (5, 10, 15 mo) and among seasons (three successive 5-mo intervals). In tidepools, mussels naturally occurred in small patches (median

Breaking waves impose large hydrodynamic forces which may dislodge mussels and other organisms living on exposed rocky shores. We examined the effect of variation in attachment strength with size, habitat and season on the predicted probability of wave dislodgment of mussels Mytilus trossulus and M. edulis on an exposed shore on the Atlantic coast of Nova Scotia, Canada. Mussels on this shore are exposed to maximum significant wave heights of at least 7 to 9 m each winter and to maximal water velocities of at least 12 m s -1 . We used Denny's (1995) mechanistic approach to predict probabilities of dislodgment from measures of attachment strength of mussels. Predicted probabilities of dislodgment indicated that mussels of 10 to 25 mm shell length are vulner- able to dislodgment by water velocities of >7 m s -1 . As a result of variation in dislodgment forces, probabilities of dislodgment did not differ consistently between tidepools and emergent rock, or with mussel size. Attachment strength increased from July to February as mussels were exposed to stronger wave action, reducing the probability of dislodgment by a given water velocity. This study indicates that knowledge of patterns of change in attachment strength are necessary for prediction of probabilities of dislodgment of mussels.

The genetic structure of mussel recruits on a rocky shore in Nova Scotia was measured after a rare ice-scouring event which completely removed the intertidal community. Genotype frequencies were measured at three enzyme loci, phosphoglucose mutase (PGM), aminopeptidase-I (product of the leucine aminopeptidase (LAP) locus), and mannose phosphate isomerase (MPI), using cellulose acetate gel electrophoresis. The developing mussel assemblage was a mixture of Mytilus trossulus, M. edulis and their hybrids, with a greater proportion of the former species. Mussel settlers were collected for two years to examine whether genetic heterogeneity existed within and between cohorts of settlers. Settlement of mussels of both species began in April or May and continued into January. Temporal genetic heterogeneity was observed among groups of settlers, resulting from both variations in the relative proportions of the two species and from genetic heterogeneity within M. trossulus. Allele frequencies of mussel cohorts were followed from settlement to ten months post-settlement to investigate the possibility of species-specific selection and of genotype-specific selection within M. trossulus. Temporal genetic heterogeneity primarily was attributed to changes in the proportions of each species, indicating that post-settlement processes were species-specific. Early post-settlement changes were inconsistent, but later changes were clearly directional, resulting in decreased proportions of M. edulis in larger mussels in both years. There was some evidence of genotype-specific post-settlement mortality within M. trossulus, particularly during the early post-settlement period. Our results indicate that temporally variable settlement patterns and post-settlement selection interacted to produce temporal genetic heterogeneity in this mussel assemblage.

Boron trifluoride clusters are formed in a supersonic expansion and ionized by electron impact. The resulting ion distribution is analyzed by time-of-flight mass spectrometry. The only consistently observed, extended series of peaks in EI of BF3 clusters is BnF3n-1+. Ab initio modeling of these ions informs our speculation regarding their internal structure and ion−molecule chemistry involved in their formation. Formation of B2F5δ+ is computationally predicted to occur in all of the cluster ions we observe (n = 2−8) except B3F8+. BF4δ- units are evident in the predicted structure of B8F23+.

The whelk Nucella lapillus is the most abundant predator of intertidal mussels (Mytilus trossulus and M. edulis) on rocky shores along the Atlantic coast of Nova Scotia, Canada. Environmental differences among intertidal habitats, such as tidepools and emergent rock, may influence the intensity of predation and its effect on community structure. We manipulated densities of both recruits ( , 5 mm shell length, SL) and post-recruits ( $ 5m m SL) ofN. lapillus in tidepools and on emergent rock to examine the effects of whelk predation on mussel assemblages on a rocky shore near Halifax, Nova Scotia. Mussels . 10 mm SL were more abundant in plots where the density of whelk post-recruits was reduced than in control plots where their density was not manipulated. Percentage cover of mussels remained stable where the density of post-recruits was reduced but declined in control plots, more so on emergent rock than in tidepools. This between-habitat difference probably reflects differences in the density of whelk post-recruits since feeding rates of whelks enclosed in cages did not differ significantly between tidepools and emergent rock. Predation by whelk post-recruits could not fully account for the reduction in mussel cover and abundance on emergent rock or in tidepools. This discrepancy is probably due to dislodgment by wave action of mussels killed by whelks, as well as the live mussels surrounding the empty shells. We could not detect an effect of recently recruited whelks on mussel cover or size distribution. Laboratory experiments indicated that the size of Nucella lapillus could be predicted from the diameter of the drill hole they create when feeding on a mussel. In the laboratory, feeding rate was linearly related to body size for recruits but not for post-recruits. Mean size of mussels consumed increased with increasing whelk size for both recruits and post-recruits. In the field, the size distribution of shells drilled by post-recruits differed from that of live mussels, but the distribution of shells drilled by recruits was generally similar to that of live mussels. Analysis of field-collected

Spatial and temporal patterns in the distribution and abundance of macroalgae and macrofauna were measured in 4 pools in each of 3 intertidal zones (mid, high and splash) on a rocky shore near Halifax, Nova Scotia, Canada. Sheets, filamentous, coarsely branched, thick leathery, jointed calcareous, and crustose forms were the most abundant macroalgal functional groups, and mussels, l~ttorinid snails and whelks were the most abundant macroinvertebrates in the pools. Percentage cover of the late-successional macroalgal forms, such as thick leathery and crustose forms, was greatest in the mid pools where environmental fluctuations are smaller and more predictable. Percentage cover of the more opportunistic forms, such as sheets and filamentous algae, was variable among pools in all zones, whereas percentage cover of the other functional forms was most variable among mid pools on most sampling dates. Mussels and whelks were more abundant in mid pools, whereas littonnes were more abundant in the high pools. Macrofaunal abundance also was variable among pools within most zones on most sampling dates. Multiple regressions showed that grazer density, nutrient regime and physical characteristics of the tidepools can consistently explain the variability in percentage cover of late-successional macroalgal functional forms, but not of the more opportunistic forms. The horizontal spatial variability in percentage cover of macroalgae may result from differential recruitment of opportunistic forms, and/or differences in the physical characteristics of the pools which affect slow-growing, late-successional forms. The Shannon D~versity Index for the macroalgal and the macrofaunal assemblages was greatest in mid pools, suggesting that a smaller number of macroalgal and macroinvertebrate species can survive in the higher pools where conditions are harsher. Cluster analyses showed that the macroalgal assemblages were mostly similar among mid pools, and that macrofaunal assemblages of mid pools were similar to high pools, but not splash pools. Our study shows that macrobenthic community structure in tidepools does not vary consistently with the period of tidal isolation and there is large variability among pools within intertidal zones.