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Inshore Scotian Shelf Ecosystem Overview Report: Status and Trends
Abstract and Figures
The Inshore Scotian Shelf Ecosystem Overview Report (EOR) describes the geological, oceanographic and biological systems of the inshore region and their relationships at the habitat and ecosystem levels. Its objectives are to provide the ecological context for integrated management, a baseline for impact assessment and planning for sustainable use of the area.
The geographical scope of the Inshore Scotian Shelf EOR is the waters less than 100 m deep or less than 25 km offshore Nova Scotia between Cape North and Cape Sable Island. This definition is largely based on the inshore limit of the Fisheries and Oceans Canada (DFO) Research Vessel trawl surveys, and does not necessarily fully reflect either the functional role of the inshore region in the structuring and population dynamics of diadromous and marine species, or the distribution of species, habitats and ecological processes considered in this report. However, it does contain distinct habitat and species that do not occur in deeper waters. Information is also presented from outside of these boundaries when relevant to the ecological and biological processes of the larger Scotian Shelf ecosystem.
There is a long history of coastal marine research in Nova Scotia, although it is patchy in nature, focusing on specific areas, specific time periods, or both. As a result, the quantity of information is not equally distributed across species, habitats or ecological processes, meaning that information quantity is not necessarily related to relative importance. Information is drawn from primary literature; provincial, federal, municipal and environmental consultants’ reports; and preliminary analyses from the DFO Inshore Ecosystem Project. Although a historical perspective is provided, this report is largely based on information from the last 50 years.
Most of the inshore region is characterized by relatively rugged and hard bedrock outcrop terrain at or immediately below the seabed. Mapping along the Atlantic coast shows that sand and gravel are present over most of the inner shelf but in such a thin layer as to have little effect on the seabed morphology. Shoreline habitats include rocky shores and headlands, large bays and inlets, estuaries, salt marshes and sandy and rocky beaches.
The entire coastline is influenced by periodic forcing of large scale shelf processes, such as coastal upwelling and the Nova Scotia Current (NSC). The NSC is a longshore current bringing fresher water from the Gulf of St. Lawrence onto the shelf, resulting in an along-shore gradient of increasing salinity and decreasing stratification from east to west. However, many of the invertebrate and fish species of the inshore region are ubiquitous. Community composition and diversity vary at the habitat level, with the degree of exposure to the open ocean largely defining the inter-tidal and sub-tidal communities.
The inshore and offshore regions are linked through the export of production by macrophytes, larvae from sessile invertebrates, and anadromous fishes. There is also a net loss of production to migrating birds, reptiles, large pelagic fishes and marine mammals that seasonally visit and feed in the inshore region. Many species caught offshore in shelf-based commercial fisheries use the inshore region as a nursery area and also feed upon the anadromous fishes and larvae exported into the pelagic food chains of the offshore region. Human activities that have the largest influence on inshore ecosystems are fishing, aquaculture, coastal development and infilling, transportation, mining, and climate change. Four centuries of fishing have left the inshore region low in abundance of traditional fish species and depauperated of spawning areas for species such as cod and herring, while the abundance of invertebrates such as lobsters and crabs has increased. Macrophytes, the defining biological feature upon which inshore organisms depend for food and habitat, will be impacted by the effects of climate change on shoreline habitats. The nature and extent of these impacts are currently unknown, requiring urgent research.
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... from Cape Sable Island (43.4905°N, 65.6214°W) to Cape North (47.0295°N, 60.3921°W; Figure 1). This expanse of the inshore Scotian Shelf is characterized by extensive bedrock outcrops with thin sand and gravel deposits occurring throughout and infill of mud constrained mainly to deep basins and inner harbours (Bundy et al., 2014). The predominantly rocky shoreline is intersected by large bays, long and narrow inlets, salt marsh and sandy beaches (Bundy et al., 2014). ...
... This expanse of the inshore Scotian Shelf is characterized by extensive bedrock outcrops with thin sand and gravel deposits occurring throughout and infill of mud constrained mainly to deep basins and inner harbours (Bundy et al., 2014). The predominantly rocky shoreline is intersected by large bays, long and narrow inlets, salt marsh and sandy beaches (Bundy et al., 2014). Human impacts to eelgrass beds in this region are relatively low in comparison to other areas of Atlantic Canada (Murphy et al., 2019). ...
Baseline data on the distribution and extent of biogenic habitat-forming species at a high spatial resolution are essential to inform habitat management strategies, preserve ecosystem integrity, and achieve effective conservation objectives in the nearshore. Model-based approaches to map suitable habitat for these species are a key tool to address this need, filling in gaps where observations are otherwise unavailable and remote sensing methods are limited by turbid waters or cannot be applied at scale. We developed a high resolution (35 m) ensemble species distribution model to predict the distribution of eelgrass (Zostera marina) along the Atlantic coast of Nova Scotia, Canada where the observational coverage of eelgrass occurrence is sparse and nearshore waters are optically complex. Our ensemble model was derived as a performance-weighted average prediction of 7 different modeling methods fit to 6 physical predictors (substrate type, depth, wave exposure, slope, and two bathymetric position indices) and evaluated with a 5-fold spatially-blocked cross-validation procedure. The ensemble model showed moderate predictive performance (Area Under the Receiver-Operating Characteristic Curve (AUC) = 0.803 ± 0.061, True Skill Statistic (TSS) = 0.531 ± 0.100; mean ± SD), high sensitivity (92.0 ± 4.5), and offered some improvement over individual models. Substrate type, depth, and relative wave exposure were the most influential predictors associated with eelgrass occurrence, where the highest probabilities were associated with sandy and sandy-mud sediments, depths ranging 0 m – 4 m, and low to intermediate wave exposure. Within our study region, we predicted a total extent of suitable eelgrass habitat of 38,130 ha. We found suitable habitat was particularly extensive within the long narrow inlets and extensive shallow flats of the South Shore, Eastern Shore, and Bras d’Or Lakes. We also identified substantial overlap of eelgrass habitat with previously identified Ecologically and Biologically Significant Areas that guide regional conservation planning while also highlighting areas of greater prediction uncertainty arising from disagreement among modeling methods. By offering improved sensitivity and insights into the fine-scale regional distribution of a habitat-forming species with associated uncertainties, our ensemble-based modeling approach provides improved support to numerous nearshore applications including conservation planning and restoration, marine spatial and emergency response planning, environmental impact assessments, and fish habitat protection.
... The Bedford Basin is a coastal inlet connected to the Scotian Shelf by a long (10 km), shallow (20 m) sill (Li & Harrison 2008). These waters are part of the same large-scale physical regime (Loder et al. 1998), and analysis of temperature data has shown that the Bedford Basin experiences the same environmental perturbations as the continental shelf (Bundy et al. 2014). The Bedford Basin exhibits the same climatology as the Scotian Shelf, losing ecological autonomy after only 3 d (Lewis & Platt 1982, Li & Dickie 2001. ...
... Water exchange between the Bedford Basin and Scotian Shelf occurs via Ekman transport and is heavily influenced by the Nova Scotia Current (Greenberg et al. 1997, Shan et al. 2011, Shan & Sheng 2012, Dever et al. 2016. Like coastal and shallow areas of the Scotian Shelf, the Bedford Basin is optically complex and can be classified as a Case 2 water body (Song et al. 2010, Bundy et al. 2014. Results of multi-year time series analyses within the Bedford Basin and across the Scotian Shelf indicate that both nutrient concentrations and phytoplankton abundances are within the same ranges (Platt et al. 1972, Petrie et al. 1999, Li et al. 2006. ...
Studies using marine animals instrumented with biologging devices to estimate phytoplankton biomass have typically omitted continental shelf regions due to the confounding effects of optically active constituents other than phytoplankton present. The lack of algorithms for these regions is problematic, as they are some of the most biologically productive in the world and are often inhabited by the species of interest. We developed a bio-optical model to estimate chlorophyll a concentration (chl a ) using light attenuation ( LA ) measured using a standard oceanographic instrument in an optically complex water body that is applicable to data collected by animal-borne devices. To achieve this, we conducted a replicated experiment to compare measurements made using time-depth-light recorders (TDLRs) to those of a standard oceanographic instrument (the HyperPro) in an adjacent water body, the Bedford Basin, Nova Scotia, Canada. Measurements of LA made by TDLRs were comparable to those of the HyperPro atdepth. The best supported bio-optical model for the estimation of chl a included both LA measured by the HyperPro and season as a fixed effect. The use of animal-borne devices to collect subsurface chl a data not only provides an opportunity to collect valuable oceanographic data but also allows for the exploration of broader ecological questions relating to the influence of primary productivity on the movement patterns of wide-ranging marine species.
... Bottom temperatures in the Northumberland Strait (LFA 25) can reach up to 18°C and are warmer than in the other sampled LFAs in this study. Additionally, LFA 25 is less exposed to large ocean currents; for example, the cold and nutrient-rich Labrador Current passes by close to LFA 33 and 34 and ocean currents are proposed to shape aquatic host-associated microbiomes (Bundy et al., 2014;Debertin et al., 2018;Sousa et al., 2021). These factors may contribute to lower microbial diversity in LFA 25 compared to the other sampling regions. ...
Host-microbe dynamics are of increasing interest in marine research due to their role in host health and productivity. Changes in the shell microbiome of American lobsters have been associated with epizootic shell disease, a syndrome that is spreading northwards across the eastern U.S. and Canadian Atlantic coast. This study analyzed differences in alpha and beta diversity, as well as differentially abundant taxa, in the shell-associated bacterial community of apparently healthy lobsters from four lobster fishing areas (LFAs) in Atlantic Canada. Over 180 lobsters from New Brunswick, Nova Scotia and Prince Edward Island (PEI) were sampled during seven sampling events over four sampling months. The bacterial community was identified using novel PacBio long-read sequencing, while alpha and beta diversity parameters were analyzed using linear regression models and weighted UniFrac distances. The bacterial richness, diversity and evenness differed by sampling location, sampling month, and molt stage, but not by lobster sex or size, nor sampling depth. Similarly, based on LFA, sampling month, year and lobster molt stage, the shell microbiome differed in microbial community composition with up to 34 out of 162 taxa differing significantly in abundance between sampling groups. This large-scale microbial survey suggests that the shell microbial diversity of apparently healthy lobsters is influenced by spatial and temporal factors such as geographic location, as well as the length of time the carapace is exposed to the surrounding seawater.
... Tourism has been implicated as a large contributor of MPs at beaches worldwide [24,25,27,71,72] . Due to their proximity to urban centers, Rainbow Haven and Martinique beaches are popular recreational sites throughout the year [73] , lending further support to local tourism as the source of some microfiber pollution in this area. ...
Aim: To investigate the baseline abundance of microplastics on two sandy beaches along an exposed coastline in an understudied region of the Northwest Atlantic.
Methods: Sandy sediments were sampled from two beaches along the eastern shore of Nova Scotia, Canada from High, Mid, and Low intertidal positions. Density floatation using a sodium iodide (NaI) solution was used to separate particles from 100 g of sediments in each sample. Particles were characterized by size, shape, and colour, and Fourier transform infrared (FTIR) spectroscopy was conducted for polymer identification.
Results: At both beaches, the majority of particles found were small (< 1.4 mm), transparent microfibers. Microplastics were polymers of polyethylene terephthalate (PET), nylon, or alkyds (paints). The mean concentrations at both beaches were similar, at 5.08 ± 3.20 and 5.58 ± 4.52 microplastics per 100 g of sediment. Non-plastic (i.e., natural and semi-synthetic cellulosic) microfibers were up to 19 times more abundant than microplastics, with mean concentrations of 75.9 ± 60.1 and 97.7 ± 87.9 per 100 g sediment. Mean particle counts did not differ significantly across tidal ranges due to their high variability over small spatial scales (10 s of m).
Conclusion: Using new investigative tools yielded estimates of microplastic pollution 1-2 orders of magnitude lower than earlier research conducted at these sites, and was generally lower than values reported from other beaches globally. Sources of microfibers were potentially from high recreational use at these sites. Future monitoring could target these sites for time series analysis of microplastic change on exposed sandy beaches.
... The Bay of Fundy, bordered by NB and the northwest coastline of NS, experiences large, semi-diurnal tides, with a tidal range of 5.5 m near the mouth of the bay, and 14.5 m near the head of the bay in Minas Basin (Bundy et al., 2014). Along the southwestern and eastern shoreline of NS, tidal range is lower and varies from 1.5 to 3.0 m. ...
Nutrient pollution derived from human land-use activities remains a major cause of the eutrophication of coastal ecosystems around the world. In this study, we conduct a nutrient loading analysis for the coastal watersheds bordering the Bay of Fundy and Scotian Shelf of Atlantic Canada, a cold temperate region of the Northwest Atlantic that exhibits strong gradients in oceanographic conditions and human uses of the coastal zone, and where coastal development is expected to increase in the coming decades. Our objective was to apply the Nitrogen Loading Model (NLM) framework to determine the regional distribution and intensity of nitrogen inputs from land-based sources (wastewater, atmospheric deposition, land use, fertilizer applications, and regional industries) to coastal marine environments, and subsequently identify coastal embayments at risk of developing symptoms of eutrophication. Across all 109 watersheds examined, the estimated mean total nitrogen load varied by three orders of magnitude. The largest loads occurred in the most heavily urbanized and densely populated watersheds, where wastewater inputs contributed the most (>80%) to loading rates. Where the footprint of human activity was small, atmospheric deposition of nitrogen was an important contributor to the total load; however, localized point sources (i.e. seafood processing, fur farming) were significant contributors to the total load in smaller sized watersheds. Coastal embayments with small surface areas and low tidal exchange volumes were most likely to have estuarine loading rates that exceeded previously established thresholds for the loss of submerged aquatic vegetation (e.g., eelgrass). In contrast, none of the embayments were deemed likely to develop anoxia. This analysis enables a novel comparison of nitrogen loading from watersheds across a range of land cover types, watershed characteristics, and human land-use activities, while providing a baseline for the detection of future environmental change in the region. Overall, we emphasize the importance of including human activities that occur on the landscape in future marine coastal planning.
Northern sand lance (Ammodytes dubius) are essential forage fish in most offshore, temperate-to-polar waters on the Northwest Atlantic shelf (NWA), but their population structure and genetic separation from the American sand lance (A. americanus) remain unresolved. We assembled a reference genome for A. dubius (first in the Ammodytidae) and then used low-coverage whole genome sequencing on 262 specimens collected across the species distribution (Mid-Atlantic Bight to Greenland) to quantify genetic differentiation between geographic regions based on single nucleotide polymorphisms. We found strong separation between A. dubius from locations north and south of the Scotian Shelf, largely due to massive genetic differentiation spanning most of chromosomes 21 and 24. Genetic distance increased with geographic distance in the smaller southern cluster but not in the larger northern cluster, where genetic homogeneity appeared across large geographic distances (>103 km). The two genetic clusters coincide with a clear break in winter sea surface temperature, suggesting that differential offspring survival, rather than limited transport, causes a break in realized connectivity. Nuclear and mitochondrial DNA both clearly delineated A. dubius from A. americanus, thereby confirming a species boundary through spatial niche partitioning into inshore (A. americanus) and offshore (A. dubius) sand lance species on the NWA.
The Atlantic coast of Nova Scotia is highly irregular, with numerous embayments containing barrier beaches. These have developed in the context of long-term marine transgression. The beaches consist predominantly of locally-derived sands and gravels supplied from eroding glacial deposits exposed at headlands. We recognize a range of barrier types, including (1) prograded beach-ridge complexes; (2) high gravel storm ridges; (3) gravel barriers subject to high rates of washover; (4) trailing and fringing gravel spits and ridges; and (5) sandy barrier complexes with low dunes. Gravel accumulations of type 1 develop where sediment supply exceeds longshore transport or washover capacity. They may change to type 2 as sediment supply diminishes. With rising sea level, type 2 barriers can be vulnerable to overwash during extreme events and may be transformed ultimately into unstable barriers of type 3. Type-3 barriers show high rates of landward migration. Their instability results primarily from low rates of sediment supply and low crest elevation. Type-4 spits and ridges show highly developed longshore cell development and/or fragmentation. The stability of type-5 barriers depends in part on sediment supply and the size and condition of dunes. The large volume of sand required to form type-5 features may accumulate primarily in embayments, by import through flood-dominated tidal inlets, to be reworked later by waves following a rise in relative sea level and associated landward translation of the coast.
Chemical oceanography of the Bras D'Or Lakes
A permanent trap fishery for northern pink shrimp (Pandalus borealis) was established in Chedabucto Bay, Nova Scotia in 1996 after several years of experimental trapping by one fisherman. Despite extensive experimental trapping projects elsewhere in Nova Scotia, only in one other area, Mahone Bay, has a long-term fishery been successfully established. The successful trapping of shrimp from small vessels off the coast of Nova Scotia appears to be dependant on a number of requisite conditions, including the presence of soft mud habitat and low temperatures in large, relatively deep coastal embayments. Catch rates for the established inshore trap fisheries increase in late summer-fall and decrease in spring, suggesting that an inshore migration occurs in the fall from adjacent “feeder” populations. In addition to the seasonal pattern of trapcatches, cyclical changes at a finer temporal scale were observed that appear to be related to tidal cycles, with higher catch rates associated with greater tidal ranges. Coupled with known diurnal vertical migratory behaviour, this pattern could arise as more water, and the shrimp within it, pass horizontally over the trap and come into contact with its bait plume during greater tidal ranges. More complex, selective vertical migration coupled with tidal drift may result in net movement into areas such as Chedabucto Bay. Analysis of length at sex transition and maximum size suggests that shrimp trapped in Chedabucto Bay come from the same population as those caught by trawlers inshore and offshore on the eastern Scotian Shelf. Shrimp trapped in Mahone Bay and St. Margaret’s Bay have significantly different growth characteristics and are probably from a different population. Thus the Mahone Bay and St. Margaret’s Bay population appears to be more locally confined than the widespread shrimp population on the eastern Scotian Shelf, possibly originating from areas within and immediately adjacent to these bays.Une pêche annuelle de la crevette nordique (Pandalus borealis) au casier a étéétablie dans la baie Chedabucto (Nouvelle‑Écosse) en 1996, après plusieurs années de pêche expérimentale au casier par un pêcheur. Malgré les nombreux projets de pêche expérimentale au casier menés ailleurs dans la province, une pêche à long terme a été établie avec succès dans seulement un autre secteur (la baie Mahone). La réussite de la pêche de la crevette au casier par les petits bateaux au large de la côte de la Nouvelle‑Écosse semble dépendre d’un certain nombre de conditions, y compris la présence d’un habitat vaseux mou et de basses températures dans de grandes échancrures relativement profondes de la côte. Les taux de capture pour les pêches côtières au casier établies augmentent à la fin de l’été et à l’automne et baissent au printemps, ce qui suggère que les crevettes migrent de populations sources vers la côte à l’automne. En plus de ce profil saisonnier des prises dans les casiers, deschangements cycliques à une échelle temporelle plus fine ont été observés et ceux‑ci semblent liés au cycle de marée, le taux de capture étant plus élevé lorsque l’amplitude de la marée est grande. Combiné au comportement de migration verticale diurne, ce profil pourrait survenir quand la quantité d’eau (et les crevettes qu’elle contient) qui passe horizontalement au-dessus des casiers est grande et qu’elle entre en contact avec le panache d’attractifs des casiers durant les périodes de grande amplitude de la marée. Une migration verticale sélective plus complexe combinée à une dérive tidale pourrait donner lieu à un mouvement net vers les secteurs comme la baie Chedabucto. L’analyse de la longueur au moment du changement de sexe et de la taille maximale suggère que les crevettes piégées dans la baie Chedabucto appartiennent à la mêmepopulation que celles capturées par les chalutiers en milieux côtiers et extracôtiers dans la partie est du plateau néo‑écossais. Les crevettes piégées dans les baies Mahone et St. Margaret’s ont des caractéristiques de croissance considérablement différentes et font probablement partie d’une autre population. Ainsi, la population des baies Mahone et St. Margaret’s semble avoir une aire de répartition beaucoup plus limitée que la population étendue de crevettes dans la partie est du plateau néo‑écossais, et elle provient peut-être de secteurs à l’intérieur de ces baies ou adjacents à celles-ci.
This book is a rewritten edition of the authors' and M.J. Duncan's 1985 textbook (and review of the primary literature), The physiological ecology of seaweeds. The introductory chapter reviews seaweed morphology, life histories and morphogenesis, serving as an encapsulation of structure and reproduction and providing a background reference for the subsequent chapters. The second chapter comprises six guest essays authored by senior algal ecologists looking at seaweed communities: rocky intertidal zone; tropical reefs; kelp forests; seaweeds in estuaries and salt marshes; seagrass beds as habitats for algae; and the Arctic subtidal. Next, biotic interactions are covered: competition, grazing, and symbiosis. Chapter four looks at light and photosynthesis and chapter five reviews nutrients (requirements, availability, pathways and barriers, uptake kinetics, assimilation, translocation). Chapters six, seven and eight explore temperature and salinity, water motion, and pollution, respectively. The final chapter looks at seaweed mariculture covering the culture of Porphyra, Laminaria, Undaria, Eucheuma, and Kappaphycus. An appendix summarizes the current taxonomic position and nomenclature of the species mentioned in the text. -S.R.Harris
