Numerous studies demonstrate the utility of information from coastal seine surveys for monitoring... more Numerous studies demonstrate the utility of information from coastal seine surveys for monitoring juveniles of Atlantic cod Gadus morhua, but few studies have linked such surveys to older ages within cohorts. We related juvenile (age-0 and-1) cod population components at a long-term monitoring site in Newfoundland to offshore pre-adult (age-3) cod recruitment at multiple spatial scales and explored some environmental and biological factors that affect juvenile−recruit relationships. Our models revealed significant relationships between juvenile and pre-adult abundance. The strength of these relationships varied with distance from nursery habitats and among fisheries management zones. Additionally, chlorophyll a concentration and body length during early life stages appeared to influence the strength of the relationship between juvenile and age-3 abundance. The potential to use juveniles as general indicators of future preadult abundance can aid in planning for low recruitment years and improve inferences about the response of cod population abundance to environmental changes. This study contributes to the growing body of knowledge demonstrating the utility of juvenile surveys in anticipating future year-class strength.
Current knowledge on the role of food for benthic communities and associated food webs focuses on... more Current knowledge on the role of food for benthic communities and associated food webs focuses on quantity of available organic matter; however, the few studies that specifically address food quality show significant potential influences on food web and community structure. We examine current understanding of food quality, and consider its contribution to regulating benthic ecosystems. By assembling data from the literature we found that, whereas food quantity increases benthic stocks (i.e., abundances), various trophic groups respond differently to quality parameters, suggesting that food quality can alter benthic trophic structure substantially. Moreover, contrasting ecosystems respond differently to food quantity and quality inputs. Based on our literature review we find that, for many highly productive coastal marine ecosystems (coral reefs, seagrass meadows, kelp forests), the detrital compartment represents the most important primary food source because low nutritional value (i.e., hard skeleton, lignin, deterrent substances, etc.) often characterizes this high productivity. Strong seasonality in the flux of organic matter, such as in polar ecosystems, results in food webs based on relatively consistent but often poorer quality food sources (i.e., "food banks"). Benthic community structure may shift dramatically in food-poor deep-sea ecosystems where otherwise rare species become dominant in response to food pulses. These ecosystems appear to respond more strongly than other benthic ecosystems to quantity and quality of food input. In deep-sea chemosynthetic environments, high food quantity and quality fuel benthic communities through resource partitioning of specialized chemosynthesis-based food sources. Lastly, we argue that food quality may have significant implications for benthic ecosystem functioning and services (e.g., bioturbation, nutrient fluxes, organic carbon preservation), particularly in the context of global warming. These implications point to several key gaps and opportunities that future food web studies should consider by applying knowledge gained in aquaculture to field studies, understanding the mechanisms for particle selection within the detrital compartment, and better understanding how rising temperatures and ocean acidification impact ecosystem functioning through changes in food quality.
This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Highlights Food arrives at 400 m depth, and deposits and accumulates deeper in the canyon. To... more Highlights Food arrives at 400 m depth, and deposits and accumulates deeper in the canyon. Topography, sediments, and surface primary productivity predicted food distribution. Oxygen and hydrocarbon drove macrofaunal distribution at large spatial scales. Food patchiness within sites was high in the upper canyon (≤ 800 m). A distinct community coincided with a sea urchin aggregation (small spatial scale).
In order to evaluate the influence of food quality on deep-sea macroinfaunal and mega-epifaunal c... more In order to evaluate the influence of food quality on deep-sea macroinfaunal and mega-epifaunal communities, we deployed experimental food pulses at 890 m depth in Barkley Canyon, NE Pacific. Pulses of 2 microalgal species (i.e. Chaetoceros calcitrans and Nannochloropsis oculata) differed in nitrogen, carotenoid, and lipid content (i.e. quality). After 8 mo, we sampled the enriched patches and controls with push cores. The community structure between the 2 treatments differed in the deeper sediment layers (5−10 cm). Despite no significant differences in the surface sediments (0−5 cm) among the 2 enrichment patches and the control, the macroinfaunal community from sediments enriched with N. oculata separated in ordination space. These results suggest that the experimental duration exceeded the appropriate time-frame to detect initial colonizers at the surface sediments. Analyses of functional traits, including migration, colonization, foraging, and food selectivity, separated communities in ordination space among algal treatments and control, although not significantly. Based on fixed camera images of each treatment over the course of the experiment, we observed more epifaunal Brachyura visits (between 50 and 40 more) to a patch enriched with N. oculata than to a patch enriched with C. calcitrans or the procedural control patch during the first 2 wk of the experiment. The visible area of 1 enrichment patch per algal treatment disappeared (> 90%) ~1.5 mo after deployment. Our study points to influences of food quality, at the algal class level, on macroinfaunal community structure and function, epifaunal disturbance, and sediment reworking.
Deep-sea Research Part I-oceanographic Research Papers, Oct 1, 2018
Abstract Increasing evidence points to greater temporal variation in deep-sea ecosystems than pre... more Abstract Increasing evidence points to greater temporal variation in deep-sea ecosystems than previously thought. In cold seeps, most available evidence focuses on successional stages of megafauna, with few studies on temporal variability in infaunal communities. We present a temporal study of infaunal communities and sedimentary organic matter characteristics from Barkley Hydrates outcrop, a chemosynthetic environment that receives organic matter from chemosynthetic and photosynthetic (phytodetritus) origins. In order to help interpret results from the outcrop, we contrast temporal variability in outcrop communities during two sampling periods with corresponding variation in an adjacent background sedimentary habitat (both habitats at ~900 m depth, offshore of British Columbia, Canada), that receives food input only from a photosynthetic source (phytodetritus). Comparisons with the background community help in differentiating chemosynthetic from photosynthetic food effects at the outcrop. Our results show contrasting temporal patterns for each community. First, lower (though not significantly) total density at the outcrop site in May 2014 corresponded to a significant change in species characteristic of that location (i.e., oligochaetes, dorvilleid polychaetes, and bivalves) in the previous sampling period (i.e., September 2013). Background communities did not change significantly in total density or species composition. Changes at the outcrop coincided with higher values of δ13C in sediment layers in May 2014, indicating reduced contributions of chemosynthetic organic matter to the total organic carbon pool relative to September 2013, and low bottom water methane concentrations. Second, although not significantly different, we detected more recruits in September 2013 for multiple species (Bipalponephtys cornuta, Cossura longocirrata, ampharetid polychaetes, Leitoscoloplos sp., and Levinsenia sp.) at the background site, following increased surface primary productivity in summer (June-August 2013). The presence of recruits of ampharetid polychaetes at both sites in September 2013 suggests that, although most individuals from the hydrate site depend on chemosynthetic food sources and therefore track temporal variation of organic matter chemosynthesised from methane, some outcrop site species also track phytodetritus pulses, much as observed in the background community. Our results demonstrate the utility of temporal studies in identifying the primary food source(s) fueling seafloor communities, and the dynamic nature of deep-sea infaunal communities from contrasting sites in Barkley Hydrates.
Deep-sea Research Part I-oceanographic Research Papers, Oct 1, 2018
In order to assess the influence of organic matter patchiness on deep-sea biodiversity, we examin... more In order to assess the influence of organic matter patchiness on deep-sea biodiversity, we examined organic matter patchiness and macrofauna at small spatial scales (meters-100s of meters) in a chemosynthetic environment (Barkley methane hydrates, British Columbia continental slope, ~900 m depth). Specifically, we assessed quantity, quality, and sources of organic matter and their influence on the associated infaunal community and food web structure (feeding guild composition) at the methane outcrop, as well as at sites 20 m and 600 m away. We found greater patchiness in food composition at the outcrop site (containing clam beds) than the more distant locations. Trophic diversity (ES [10]) was significantly greater at the outcrop compared to that at the 20 m site, suggesting that the outcrop added rather than replaced trophic niche opportunities. Diversity (ES [10]) was lower at the outcrop compared to the other two sites, although not significantly so. We re-analysed the community data at higher spatial resolution (5 to 10 m, and lower replication) to identify the distance of influence of the hydrates habitat and found a transition from outcrop to background at 9 and 15 m away from the most active site, with greater similarity in the communities at 28 m to those at 600 m than the outcrop itself. Food quality (i.e., nutritional value for benthic organisms) and source played a significant role in determining food web structure, outweighing the influences of food quantity and sediment type. However, our distancebased linear model (distLM) using all variables, food quality, or topography explained only 33.56 %, 33.54 %, and 33.18 % respectively of the total variation in feeding guild composition, suggesting important roles for other environmental variables. We conclude that the higher food patchiness in Barkley Hydrates compared to ambient sediments likely contributed to increased trophic niche opportunities. We emphasize the importance of sampling at adequate spatial scales to detect the influence of methane hydrates in infaunal communities and food webs.
Predicting dispersal paths of marine larvae with long pelagic durations, such as American lobster... more Predicting dispersal paths of marine larvae with long pelagic durations, such as American lobster (Homarus americanus), requires understanding the cues to which larvae respond, and how that response reflects changes in larval behaviour. If larvae respond to conspecific presence by varying their movement, this behaviour can bias laboratory estimates of environmental responses. We tested whether larvae actively decreased their local intraspecific density by measuring how the vertical distribution of larvae changed under high versus low concentrations of conspecifics. We observed weak increases in vertical dispersion at higher concentrations in both newly-hatched larvae and in post-larvae, but not in intermediate larval stages. Further, we found that larvae from different mothers consistently differed in vertical distribution, which may indicate maternal effects on dispersal behavior. We also tested for differences in horizontal swimming behaviour in high and low concentrations, by fitting a novel random walk model that allowed us to model both larval interactions and persistent turning behaviours. We showed substantial reduction in diffusive behaviour under high concentration conditions resulting from more frequent turns by each larva, but no evidence for consistent avoidance of conspecifics. Our study is the first to demonstrate concentration-dependent behaviours in lobster larvae.
Implementation of marine conservation strategies, such as increasing the numbers, extent, and eff... more Implementation of marine conservation strategies, such as increasing the numbers, extent, and effectiveness of protected areas (PAs), can help achieve conservation and restoration of ocean health and associated goods and services. Despite increasing recognition of the importance of including aspects of ecological functioning in PA design, the physical characteristics of habitats and simple measures of species diversity inform most PA designations. Marine and terrestrial ecologists have recently been using biological traits to assess community dynamics, functioning, and vulnerability to anthropogenic impacts. Here, we explore potential trait-based marine applications to advance PA design. We recommend strategies to integrate biological traits into ( a) conservation objectives (e.g., by assessing and predicting impacts and vulnerability), ( b) PA spatial planning (e.g., mapping ecosystem functions and functional diversity hot spots), and ( c) time series monitoring protocols (e.g., using functional traits to detect recoveries). We conclude by emphasizing the need for pragmatic tools to improve the efficacy of spatial planning and monitoring efforts.
Numerous studies demonstrate the utility of information from coastal seine surveys for monitoring... more Numerous studies demonstrate the utility of information from coastal seine surveys for monitoring juveniles of Atlantic cod Gadus morhua, but few studies have linked such surveys to older ages within cohorts. We related juvenile (age-0 and-1) cod population components at a long-term monitoring site in Newfoundland to offshore pre-adult (age-3) cod recruitment at multiple spatial scales and explored some environmental and biological factors that affect juvenile−recruit relationships. Our models revealed significant relationships between juvenile and pre-adult abundance. The strength of these relationships varied with distance from nursery habitats and among fisheries management zones. Additionally, chlorophyll a concentration and body length during early life stages appeared to influence the strength of the relationship between juvenile and age-3 abundance. The potential to use juveniles as general indicators of future preadult abundance can aid in planning for low recruitment years and improve inferences about the response of cod population abundance to environmental changes. This study contributes to the growing body of knowledge demonstrating the utility of juvenile surveys in anticipating future year-class strength.
Current knowledge on the role of food for benthic communities and associated food webs focuses on... more Current knowledge on the role of food for benthic communities and associated food webs focuses on quantity of available organic matter; however, the few studies that specifically address food quality show significant potential influences on food web and community structure. We examine current understanding of food quality, and consider its contribution to regulating benthic ecosystems. By assembling data from the literature we found that, whereas food quantity increases benthic stocks (i.e., abundances), various trophic groups respond differently to quality parameters, suggesting that food quality can alter benthic trophic structure substantially. Moreover, contrasting ecosystems respond differently to food quantity and quality inputs. Based on our literature review we find that, for many highly productive coastal marine ecosystems (coral reefs, seagrass meadows, kelp forests), the detrital compartment represents the most important primary food source because low nutritional value (i.e., hard skeleton, lignin, deterrent substances, etc.) often characterizes this high productivity. Strong seasonality in the flux of organic matter, such as in polar ecosystems, results in food webs based on relatively consistent but often poorer quality food sources (i.e., "food banks"). Benthic community structure may shift dramatically in food-poor deep-sea ecosystems where otherwise rare species become dominant in response to food pulses. These ecosystems appear to respond more strongly than other benthic ecosystems to quantity and quality of food input. In deep-sea chemosynthetic environments, high food quantity and quality fuel benthic communities through resource partitioning of specialized chemosynthesis-based food sources. Lastly, we argue that food quality may have significant implications for benthic ecosystem functioning and services (e.g., bioturbation, nutrient fluxes, organic carbon preservation), particularly in the context of global warming. These implications point to several key gaps and opportunities that future food web studies should consider by applying knowledge gained in aquaculture to field studies, understanding the mechanisms for particle selection within the detrital compartment, and better understanding how rising temperatures and ocean acidification impact ecosystem functioning through changes in food quality.
This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Highlights Food arrives at 400 m depth, and deposits and accumulates deeper in the canyon. To... more Highlights Food arrives at 400 m depth, and deposits and accumulates deeper in the canyon. Topography, sediments, and surface primary productivity predicted food distribution. Oxygen and hydrocarbon drove macrofaunal distribution at large spatial scales. Food patchiness within sites was high in the upper canyon (≤ 800 m). A distinct community coincided with a sea urchin aggregation (small spatial scale).
In order to evaluate the influence of food quality on deep-sea macroinfaunal and mega-epifaunal c... more In order to evaluate the influence of food quality on deep-sea macroinfaunal and mega-epifaunal communities, we deployed experimental food pulses at 890 m depth in Barkley Canyon, NE Pacific. Pulses of 2 microalgal species (i.e. Chaetoceros calcitrans and Nannochloropsis oculata) differed in nitrogen, carotenoid, and lipid content (i.e. quality). After 8 mo, we sampled the enriched patches and controls with push cores. The community structure between the 2 treatments differed in the deeper sediment layers (5−10 cm). Despite no significant differences in the surface sediments (0−5 cm) among the 2 enrichment patches and the control, the macroinfaunal community from sediments enriched with N. oculata separated in ordination space. These results suggest that the experimental duration exceeded the appropriate time-frame to detect initial colonizers at the surface sediments. Analyses of functional traits, including migration, colonization, foraging, and food selectivity, separated communities in ordination space among algal treatments and control, although not significantly. Based on fixed camera images of each treatment over the course of the experiment, we observed more epifaunal Brachyura visits (between 50 and 40 more) to a patch enriched with N. oculata than to a patch enriched with C. calcitrans or the procedural control patch during the first 2 wk of the experiment. The visible area of 1 enrichment patch per algal treatment disappeared (> 90%) ~1.5 mo after deployment. Our study points to influences of food quality, at the algal class level, on macroinfaunal community structure and function, epifaunal disturbance, and sediment reworking.
Deep-sea Research Part I-oceanographic Research Papers, Oct 1, 2018
Abstract Increasing evidence points to greater temporal variation in deep-sea ecosystems than pre... more Abstract Increasing evidence points to greater temporal variation in deep-sea ecosystems than previously thought. In cold seeps, most available evidence focuses on successional stages of megafauna, with few studies on temporal variability in infaunal communities. We present a temporal study of infaunal communities and sedimentary organic matter characteristics from Barkley Hydrates outcrop, a chemosynthetic environment that receives organic matter from chemosynthetic and photosynthetic (phytodetritus) origins. In order to help interpret results from the outcrop, we contrast temporal variability in outcrop communities during two sampling periods with corresponding variation in an adjacent background sedimentary habitat (both habitats at ~900 m depth, offshore of British Columbia, Canada), that receives food input only from a photosynthetic source (phytodetritus). Comparisons with the background community help in differentiating chemosynthetic from photosynthetic food effects at the outcrop. Our results show contrasting temporal patterns for each community. First, lower (though not significantly) total density at the outcrop site in May 2014 corresponded to a significant change in species characteristic of that location (i.e., oligochaetes, dorvilleid polychaetes, and bivalves) in the previous sampling period (i.e., September 2013). Background communities did not change significantly in total density or species composition. Changes at the outcrop coincided with higher values of δ13C in sediment layers in May 2014, indicating reduced contributions of chemosynthetic organic matter to the total organic carbon pool relative to September 2013, and low bottom water methane concentrations. Second, although not significantly different, we detected more recruits in September 2013 for multiple species (Bipalponephtys cornuta, Cossura longocirrata, ampharetid polychaetes, Leitoscoloplos sp., and Levinsenia sp.) at the background site, following increased surface primary productivity in summer (June-August 2013). The presence of recruits of ampharetid polychaetes at both sites in September 2013 suggests that, although most individuals from the hydrate site depend on chemosynthetic food sources and therefore track temporal variation of organic matter chemosynthesised from methane, some outcrop site species also track phytodetritus pulses, much as observed in the background community. Our results demonstrate the utility of temporal studies in identifying the primary food source(s) fueling seafloor communities, and the dynamic nature of deep-sea infaunal communities from contrasting sites in Barkley Hydrates.
Deep-sea Research Part I-oceanographic Research Papers, Oct 1, 2018
In order to assess the influence of organic matter patchiness on deep-sea biodiversity, we examin... more In order to assess the influence of organic matter patchiness on deep-sea biodiversity, we examined organic matter patchiness and macrofauna at small spatial scales (meters-100s of meters) in a chemosynthetic environment (Barkley methane hydrates, British Columbia continental slope, ~900 m depth). Specifically, we assessed quantity, quality, and sources of organic matter and their influence on the associated infaunal community and food web structure (feeding guild composition) at the methane outcrop, as well as at sites 20 m and 600 m away. We found greater patchiness in food composition at the outcrop site (containing clam beds) than the more distant locations. Trophic diversity (ES [10]) was significantly greater at the outcrop compared to that at the 20 m site, suggesting that the outcrop added rather than replaced trophic niche opportunities. Diversity (ES [10]) was lower at the outcrop compared to the other two sites, although not significantly so. We re-analysed the community data at higher spatial resolution (5 to 10 m, and lower replication) to identify the distance of influence of the hydrates habitat and found a transition from outcrop to background at 9 and 15 m away from the most active site, with greater similarity in the communities at 28 m to those at 600 m than the outcrop itself. Food quality (i.e., nutritional value for benthic organisms) and source played a significant role in determining food web structure, outweighing the influences of food quantity and sediment type. However, our distancebased linear model (distLM) using all variables, food quality, or topography explained only 33.56 %, 33.54 %, and 33.18 % respectively of the total variation in feeding guild composition, suggesting important roles for other environmental variables. We conclude that the higher food patchiness in Barkley Hydrates compared to ambient sediments likely contributed to increased trophic niche opportunities. We emphasize the importance of sampling at adequate spatial scales to detect the influence of methane hydrates in infaunal communities and food webs.
Predicting dispersal paths of marine larvae with long pelagic durations, such as American lobster... more Predicting dispersal paths of marine larvae with long pelagic durations, such as American lobster (Homarus americanus), requires understanding the cues to which larvae respond, and how that response reflects changes in larval behaviour. If larvae respond to conspecific presence by varying their movement, this behaviour can bias laboratory estimates of environmental responses. We tested whether larvae actively decreased their local intraspecific density by measuring how the vertical distribution of larvae changed under high versus low concentrations of conspecifics. We observed weak increases in vertical dispersion at higher concentrations in both newly-hatched larvae and in post-larvae, but not in intermediate larval stages. Further, we found that larvae from different mothers consistently differed in vertical distribution, which may indicate maternal effects on dispersal behavior. We also tested for differences in horizontal swimming behaviour in high and low concentrations, by fitting a novel random walk model that allowed us to model both larval interactions and persistent turning behaviours. We showed substantial reduction in diffusive behaviour under high concentration conditions resulting from more frequent turns by each larva, but no evidence for consistent avoidance of conspecifics. Our study is the first to demonstrate concentration-dependent behaviours in lobster larvae.
Implementation of marine conservation strategies, such as increasing the numbers, extent, and eff... more Implementation of marine conservation strategies, such as increasing the numbers, extent, and effectiveness of protected areas (PAs), can help achieve conservation and restoration of ocean health and associated goods and services. Despite increasing recognition of the importance of including aspects of ecological functioning in PA design, the physical characteristics of habitats and simple measures of species diversity inform most PA designations. Marine and terrestrial ecologists have recently been using biological traits to assess community dynamics, functioning, and vulnerability to anthropogenic impacts. Here, we explore potential trait-based marine applications to advance PA design. We recommend strategies to integrate biological traits into ( a) conservation objectives (e.g., by assessing and predicting impacts and vulnerability), ( b) PA spatial planning (e.g., mapping ecosystem functions and functional diversity hot spots), and ( c) time series monitoring protocols (e.g., using functional traits to detect recoveries). We conclude by emphasizing the need for pragmatic tools to improve the efficacy of spatial planning and monitoring efforts.
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