Trends in abundance of rocky intertidal seaweeds and filter feeders across gradients of elevation,wave exposure,and ice scour in eastern Canada

On NW Atlantic rocky shores, the main basal organisms in intertidal communities are seaweeds (Ascophyllum nodosum, Fucus spp. and Chondrus crispus) and filter feeders (barnacles, Semibalanus balanoides, and mussels, Mytilus spp.). Their ecology has been extensively studied in New England (United States), but knowledge gaps exist for northern shores, which are subjected to stronger environmental stress. Therefore, we studied the above organisms on Canadian shores. We quantified the summer abundance of these seaweeds and filter feeders across full vertical (intertidal elevation) and horizontal (wave exposure and winter ice scour) environmental gradients on the Gulf of St. Lawrence and open Atlantic coasts of Nova Scotia. At the regional scale along the open Atlantic coast, seaweeds showed similar abundances in Nova Scotia than values reported for New England. However, both filter feeders were considerably less abundant in Nova Scotia. At the local scale in Nova Scotia, intense winter ice scour (which only occurs on the Gulf of St. Lawrence coast) was associated with a very low abundance of all species except barnacles. Spatial trends in Nova Scotia were similar to patterns known for certain species elsewhere, such as A. nodosum being almost restricted to sheltered habitats, regardless of elevation, and C. crispus being almost restricted to low elevations, regardless of exposure. Other trends were, however, characteristic of Nova Scotia, such as C. crispus being frequent at low elevations in exposed habitats, unlike in New England, where mussels often predominate there because of competitive advantages. In Nova Scotia, mussels were always restricted to cracks and crevices, unlike in New England, where they form extensive intertidal beds on exposed shores. The direct effects of increased environmental stress and indirect effects through altered interspecific interactions might explain the regional differences in local species distribution, which will require experimental validation. Handling editor: K. Martens     

Mussel and dogwhelk distribution along the north‐west Atlantic coast: testing predictions derived from the abundant‐centre model

Aim We performed the first test of predictions from the abundant‐centre model using north‐west Atlantic coastal organisms. We tested the hypotheses that the density of intertidal mussels (Mytilus edulis and M. trossulus) and dogwhelks (Nucella lapillus) and mussel age and size would peak at an intermediate location along their distribution range. We also assessed the latitudinal variation in critical aerial exposure time. Location North‐west Atlantic coast between Newfoundland (Canada) and New York (USA), covering 1800 km of shoreline. Methods Using a nested design, we measured mussel density, age and size and dogwhelk density in 60 wave‐exposed rocky intertidal sites spread evenly in six regions. Critical aerial exposure times were determined using online data. Results Mytilus edulis peaked in abundance in Maine and was much less abundant in the other regions. Mytilus trossulus peaked in abundance in southern Nova Scotia and Maine, was less abundant in the other regions to the north, and was absent in the southernmost region (New York). Both mussel species were least abundant in a northern region (Cape Breton), although not in the northernmost region (Newfoundland). Critical aerial exposure times were negatively correlated with overall mussel density. Mussel age and size were similar among regions. Dogwhelks peaked in abundance in Maine and were much less abundant in the other regions, being positively correlated with overall mussel density across regions. Main conclusions Density data for M. edulis and N. lapillus provide limited support for an abundant‐centre pattern, while M. trossulus shows a clear ramped‐south distribution. Critical aerial exposure times suggest that physiological stress during summer and winter low tides may be lowest in Maine and southern Nova Scotia, which might partially explain mussel predominance in those regions. Winter ice scour in Cape Breton may explain the abundance trough observed there. Mussel size and age may be more limited by wave exposure at our sites (as they all face open waters) than by regional differences in environmental stress. Dogwhelks, which prey on mussels, seem to respond positively to prey density at the regional scale. Our study supports the notion that, while the abundant‐centre model is a useful starting point for research, it often represents an oversimplification of reality.     

Seaweed resources of North America and their utilization

From the coasts of Nova Scotia, Maine, Massachusetts, North Carolina, California and Lower California, seaweeds are harvested that yield agar, algin, carrageenin and iridophycin for industrial use.     

Use of the intertidal zone by fish in Nova Scotia

Synopsis In Nova Scotia the annual harvest of the intertidal seaweed Ascophyllum nodosum exceeds 20 000 tons. This study investigated the possible impact of removal of the seaweed on intertidal abundance of fishes and their gut contents. At sites near Lower Argyle, Nova Scotia, absolute abundance of fish in small areas with Ascophyllum removed and intact was determined with pop-up seines. Gut contents were investigated from fish collected with the seines and with trammel nets. Number and weight of fish were not significantly different between cleared and intact areas and averaged 4.6 individuals and 160 g per 400 m² during June to October. Cunner and sculpins had more food in their guts when leaving than when entering the intertidal, but only cunner had more food in their stomachs when leaving intact areas than when leaving cleared areas. Most fish captured in the intertidal were small (< 15 cm) and of no commercial value, and the numbers of commercial species were too low to be of much value. Numbers of fish in the intertidal was significantly lower than in the shallow subtidal. This study provided no evidence for adverse effects of the removal of patches of Ascophyllum on fishes.     

On the human consumption of the red seaweed dulse (Palmaria palmata (L.) Weber & Mohr)

The red seaweed dulse (Palmaria palmata) is one of the more popular seaweed species for human consumption in the Western world. With a documented historical use up to present days in Ireland, Brittany (France), Iceland, Maine (USA), and Nova Scotia (Canada), it has remained a snack, a food supplement, and an ingredient in various dishes. The trend towards more healthy and basic foodstuffs, together with an increasing interest among chefs for the seaweed cuisine, has posed the need for more quantitative knowledge about the chemical composition of dulse of relevance for human consumption. Here, we report on data for amino acid composition, fatty acid profile, vitamin K, iodine, kainic acid, inorganic arsenic, as well as for various heavy metals in samples from Denmark, Iceland, and Maine.     

Frequency of mallard-black duck hybrids along the atlantic coast determined by electrophoresis and plumage analysis

The frequency of mallard and black duck hybrids along the Atlantic flyway was estimated based on serum protein and serum esterase electrophoresis and plumage analysis. Hybrid frequencies for black ducks were low (below 10%) in Nova Scotia - Maine, Ontario and New Jersey and high (above 10%) in Maryland and Massachusetts. Plumage estimates tended to be higher for black ducks in Massachusetts and Maryland than estimates based on the electrophoretic work.     

A preliminary examination of genetic variation in a peripheral population of Blanding's turtle, Emydoidea blandingii

Random amplified polymorphic DNA (RAPD) was used to compare the Nova Scotia population of Blanding's turtle (Emydoidea blandingii) with several populations from the species' main range. The Nova Scotia population is believed to have been isolated from the main range for 4000-8000 years. Cluster analysis using a neighbour-joining algorithm produced a dendrogram showing the Nova Scotia population clustering separately from those populations in the main range. Analysis of molecular variance shows 34.28% of total variance to be accounted for between the Nova Scotia population and populations in the main range. While this study is preliminary, the results suggest that the Nova Scotia population of Blanding's turtle may be important to the maintenance of genetic diversity in the species.     

Understanding Fluctuations in Bobcat Harvest at the Northern Limit of Their Range

ABSTRACT In Quebec, Canada, harvest of bobcats (Lynx rufus) started to decline in 1985 and by 1991, harvest seasons were closed due to concerns of a perceived population decline. Since the closing of harvest season in 1991, the average temperature has increased, snow quantity has decreased, and important changes in agriculture and forest management have occurred. In light of changing conditions, the situation of Quebec bobcats needed reassessment. Thus, we analyzed harvest data to clarify the current status of bobcat populations in Quebec. From 1980 to 1991, bobcat harvest in Quebec was strongly correlated with bobcat harvest in Maine (USA), Nova Scotia (Canada), Ontario (Canada), and Vermont (USA). Extrapolations of harvest in Quebec relative to harvest in Maine, Ontario, Vermont, and Nova Scotia suggested an increase in number of bobcats after 1991. Mass of male and female bobcats before 1991 was less than mass of animals captured after 1991. Percentage of juveniles in the reported harvest before 1991 was higher than after 1991. However, percentage of males and litter sizes in the harvest did not differ before and after 1991. The geographic distribution of bobcats captured has gradually expanded after the closure of the harvest season. Our findings suggest that bobcat populations in Quebec have recovered from the 1985–1991 decline, and that the harvest season for this species could resume. This study also illustrates how managers can rely on data from neighboring jurisdiction to manage species when local harvest data is unavailable.     

CURRENT STATUS OF THE INVASIVE GREEN ALGA CODIUM FRAGILE IN EASTERN CANADA

Ten years after the initial discovery of Codium fragile in eastern Canada on the Atlantic coast of Nova Scotia, C. fragile has extended its range considerably to northern Nova Scotia, southern New Brunswick and Prince Edward Island (P.E.I.) in the Gulf of St. Lawrence. In all principal areas C. fragile subsp. tomentosoides is present. In two regions of Prince Edward Island, Codium is becoming extremely abundant, and is known by local fishers as the "oyster thief". A potential second taxon of Codium was collected in 1999 at three sites in Malpeque Bay where it is locally abundant. These plants are distinguished from C. fragile subsp. tomentosoides by their smaller frond size, flatter utricle tops, smaller mucrons, and smaller gametangia. Principal component analysis distinguishes plants of the two types. The abundance of C. fragile on both hard bottom and soft bottom substrata suggests that it will become the dominant alga in many subtidal algal communities in eastern Canada.     

Species richness and diversity in different functional groups across environmental stress gradients: a model for marine rocky shores

We present a model predicting how the species richness and diversity within benthic functional groups should vary across the full environmental stress gradient across which a regional biota from marine rocky shores can occur. Built upon previous models, our model makes predictions for sessile species (macroalgae and filter feeders), herbivores, and carnivores. We tested some of its predictions by surveying vertical (intertidal elevation) and horizontal (wave exposure and ice scour) stress gradients in northern Nova Scotia, Canada. Because of harsh winter conditions, these coasts only depict approximately intermediate‐to‐high yearly levels of stress that the cold‐temperate, rocky intertidal biota from the northwestern Atlantic can experience. The observed trends matched predictions for sessile species in 75% of the studied gradients, and showed a moderate agreement for herbivores and carnivores only when they were combined as mobile consumers. Agreement meant that both richness and diversity increased from the most stressful to the most benign habitats that can be found in northern Nova Scotia. Also as predicted, sessile species generally showed a faster rate of increase in richness than mobile consumers. Our model also predicted a higher overall richness for sessile species than for mobile consumers, which was true by a factor of 3. Therefore, our model may constitute a useful tool to understanding community composition as a function of abiotic stress, which may in turn facilitate studies on community functioning. Model predictions for lower stress ranges could be tested on more southern shores where the same regional biota occurs.     

Patterns and correlates of songbird movements at an ecological barrier during autumn migration assessed using landscape‐ and regional‐scale automated radiotelemetry

Departure decisions of songbirds at ecological barriers they encounter en route can strongly influence time, energy and survival costs of migration. To date, most field studies of departure decisions and their correlates have used indirect methods and followed migrants at a single stopover site, with limited information on what happens to individuals after they depart from the site. We used an automated radiotelemetry array extending 350 km from southwest Nova Scotia to southern Maine to study the migratory and stopover movements of Northern Waterthrushes Parkesia noveboracensis, Red‐eyed Vireos Vireo olivaceus and Yellow‐rumped Warblers Setophaga coronata in relation to fuel load and weather at the northeastern edge of the Gulf of Maine. From the 105 radio‐transmitters we deployed in southwest Nova Scotia, we recorded 42 landscape‐scale stopover flights and 47 migratory flights by 75 individuals. Of the migratory flights, 57% were orientated southwest, a trajectory that, if held, would require individuals to complete a 350–440 km overwater flight. The remaining 43% of migratory flights were orientated northwest, away from the Gulf of Maine, and 15 individuals were confirmed to have detoured around all or a portion of the barrier, as evidenced by their being re‐detected over the Bay of Fundy and/or along the coast of Maine between 4 h and 15 days later. Across all individuals, initial fat score had a positive effect on departure probability, especially for individuals that made stopover flights. Among weather variables, tailwind assistance was the best predictor of migratory departures but did not appear to be the main factor determining whether individuals orientated towards or away from the Gulf of Maine. Weather had little effect on departure decisions of individuals that made stopover flights. These differences in the correlates of migratory departures and stopover flights would probably not have been distinguishable had our study been restricted to a local scale. Therefore, our findings highlight the importance of expanding the scale at which departure decisions and the ecology of stopover in general are studied.     

Influence of genotype and geography on shell shape and morphometric trait variation among North Atlantic blue mussel (Mytilus spp.) populations

The influence of geography and genotype on shell shape (outline) and trait (morphometric) variation among North Atlantic blue mussels and their hybrids has been examined. Shape differences among reference taxa (Mytilus trossulus, Mytilus edulis and Mytilus galloprovincialis) were consistent with an association between taxon‐specific genes and shape genes. Newfoundland M. edulis × M. trossulus populations and northern Quebec M. trossulus populations exhibited an uncoupling of taxon‐specific genes from shape genes, whereas Nova Scotia M. trossulus populations and SW England M. edulis × M. galloprovincialis populations exhibited an association between taxon‐specific genes and shape genes. We found no evidence of a geographic effect (NE versus NW Atlantic) for shape variation, indicating that the genotype effect is stronger than any geographic effect at macrogeographic scales. Pronounced differences were observed in trait variability consistent with an association between taxon‐specific genes and trait genes in European populations, and trait divergence of New York M. edulis from all European mussels. Trait variability in mussels from Newfoundland, Nova Scotia and northern Quebec indicated an uncoupling of taxon genes from trait genes, whereas trait variability in SW England M. edulis × M. galloprovincialis populations was consistent with background genotype, indicating a strong association between taxon genes and trait genes. A pronounced macrogeographic split (NE versus NW Atlantic) regardless of taxonomy was observed, indicating that geography exerts a greater influence than genotype on trait variation at the macrogeographic scale. This is consistent with pronounced within‐taxon genetic divergence, indicative of different selection regimes or more likely of different evolutionary histories of mussels on either side of the North Atlantic. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96 , 875–897.     

Genetic diversity of coastal Northwest Atlantic herring populations: implications for management

Analysis of nine tetranucleotide microsatellite loci for Atlantic herring at five locations in the Northwest Atlantic including the Bras d'Or Lakes shows considerable genetic variation and significant population structure within the Coastal Nova Scotia management component, and among coastal populations and herring collected from Georges Bank. However, results are also consistent with gene flow across the Gulf of Maine. The magnitude of differentiation between the Bras d'Or Lakes sample and all others considered was sufficient to warrant further investigation. These data support the precautionary spawning-ground based management approach implemented in this area.     

DISTRIBUTION OF SAXICOLOUS CRUSTOSE CORALLINES IN THE NORTHWESTERN NORTH ATLANTIC1

The relative abundances of species of crustose coralline, as derived from areal measurements of large collections taken from Nova Scotia to Labrador, are given as a function of depth and as a function of mean maximum temperature and depth. The relative effects of depth and temperature independently are indicated and in most cases the results are markedly similar to those found in earlier Gulf of Maine studies. The distributions of Pseudolithophyllum orbiculatum and Phymatolithon rugulosum apparently are not controlled by summer temperatures in this area.     

Persistence of gametophyte predominance in Chondrus crispus (Rhodophyta,Gigartinaceae) from Nova Scotia after 12 years

Gametophytes predominated clearly over tetrasporophytes in an intertidal population of Chondrus crispus at Tor Bay (Nova Scotia, Canada) in the summer of 1991. Since this species is perennial and the rocky substrate is stable at this site, we predicted that gametophyte predominance would persist after several years. We confirmed this hypothesis by re-sampling the same area in the summer of 2003. This is one of the first long-term studies of the relative abundance of life-history phases done unequivocally at the same site for the Gigartinaceae.     

Estimating Population Growth and Recruitment Rates Across the Range of American Common Eiders

Sound management of bird populations rests upon an adequate understanding of their population dynamics. Our study evaluated recruitment and population growth rates of 14 American common eider (Somateria mollissima dresseri) colonies from Labrador, Nova Scotia, Quebec, Canada, and Maine, USA, during various periods between 1970 and 2019. We used Pradel mark-recapture models to estimate colony-specific growth rates and the relative contributions of survival and recruitment on growth. We also validated this approach using annual nest counts (~8,000 pairs) conducted between 2003 and 2019 during down harvest operations in 3 colonies located in the Saint Lawrence estuary in Quebec. There was generally a good agreement between estimates derived using the 2 approaches. We considered that capture-recapture data were suitable to estimate population trends of common eiders in other colonies, especially for colonies where accurate nest monitoring is impaired by dense vegetation. The breeding abundance declined at major colonies in Maine and Nova Scotia and increased or was stable in Quebec and Labrador. Female survival contributed the most to population growth, but variation in recruitment among colonies was more important than variation in survival to explain population growth. Management measures should thus strive to maximize local recruitment in colonies with declining populations. The assumption that apparent survival probabilities were homogeneous throughout an individual capture history was violated at several colonies in Quebec and Labrador. Using recaptures and band recoveries, we showed that the lower apparent survival for newly marked individuals compared to females that had been recaptured at least once was caused by a difference in site fidelity rather than true survival. But <1% of recaptured females dispersed to another colony for breeding, indicating that the lower site fidelity could be related to heterogeneity in capture probability among individuals. © 2021 The Wildlife Society.     

The demography of fronds of Chondrus crispus Stackhouse

A demographic analysis was done of an intertidal stand of Chondrus crispus Stackhouse at Pubnico Point, Nova Scotia. The distribution of gametophytic and tetrasporophytic fronds was assessed. Fronds were placed in one of four size-classes. Size-specific measurements for fronds are presented. Gametophytic fronds dominated the stand. Fronds in Size-Class 2 exhibited high survivorship. Survivorship fell sharply when fronds entered Size-Class 3 and Size-Class 4. Fronds became fertile and highly branched when in the third and fourth size-classes. It is suggested that these two factors contribute to the higher mortality rates of such individuals.Monthly spore release rates·m^?2 for gametophytes and tetrasporophytes were measured. The annual release rate of carpospores exceeded the annual release rate of tetraspores by a ratio of 4.7:1. Rates did not fall below 10⁶ spores released·m^?2·month^?1 for either phase.     

The effects of seaweed harvesting on fishes: a response

References Rangeley (1994) has argued that sampling biases, errors in experimental design and low statistical power make the conclusion by Black & Miller (1991), that there was no large impact of an experimental harvest of the seaweedAscophyllum nodosum on fishes, unmerited and misleading. Our study was conducted mainly at two sites close to Lower Argyle, southern Nova Scotia, Canada where harvesting ofAscophyllum nodosum has been carried out continuously for 30 years along-side intense and productive shellfish and finfish fisheries. In southern Nova Scotia, on-going removal ofAscophyllum nodosum with mechanical harvesters is about 17% (Sharpe & Semple 1991); planned annual removal in New Brunswick where Rangeley has worked will be only about 5% (Anon. 1993). The context of our investigation was a small-scale (400 m²) but extreme, experimental removal (100%) of the seaweed. Our focus was on fishes that moved into the intertidal zone as the tide rose in the evening and early morning and were caught in trammel nets, and on the fishes that were retained in a fixed seine that was set at high tide in early morning and the fishes removed at the next low tide. Thus, subject to the constraint on the size of the fishes imposed by the nature of our fishing gear with its stretch mesh of 25 mm, we were concerned with the identity and abundance of fishes that moved in and out of the intertidal zone and their behavioural response to the 400 m² patches of habitat that formed our experimental units. The most striking result was the unexpected, low abundance of fishes caught in our gear.     

OBSERVATIONS ON CHYTRIDIACEOUS PARASITES OF PHANEROGAMS. XXV. PHYSODERMA JOHNSII SPARROW,A PARASITE OF CALTHA PALUSTRIS L.

The morphology of the endobiotic and epibiotic stages of Physoderma johnsii Sparrow on Caltha palustris is described. Highly characteristic of the endobiotic stage is the formation of numbers of large, narrowly pyriform cells with a tuft of rhizoids at the broader (distal) end. Early developmental features are not included since germination of the resting spore has not as yet been achieved. Reasons for maintaining this taxon distinct from older ones on Caltha palustris are given.