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A commonly assumed pattern in species assemblages is the abundance–occupancy relationship (AOR), which refers to a relationship between the mean local abundance of each species and the proportion of local sites that each species occupies. The AOR concept is relevant because it allows researchers to make inferences or predictions between species abundance and occupancy, which are key variables in ecology. Although the AOR is thought to be ubiquitous, it has not been found for every system where it has been tested. To date, the studies that have evaluated its generality were largely done in terrestrial systems. Therefore, there is a need to evaluate its occurrence in aquatic systems. This study tests whether the AOR occurs in rocky intertidal systems. Using data for algae and invertebrates from Atlantic Canada, we show that the negative binomial model properly describes the relationship between abundance and occupancy in rocky intertidal communities. Moreover, we found the AOR to hold for two hydrodynamically contrasting habitat types. Overall, these findings expand the applicability of the AOR to marine benthic systems. The raw data are included as part of this article and should be valuable for future syntheses on the AOR, as such studies will benefit from using datasets spanning terrestrial and aquatic systems. In this sense, our abundance data are particularly relevant because they describe density of organisms, which is a condition for AOR modelling that intertidal ecological studies typically do not follow entirely, as the abundance of sessile species is often measured as percent cover. [ABSTRACT FROM AUTHOR]

Benthic species from rocky intertidal systems are irregularly distributed along marine coastlines. Nearshore pelagic conditions often help to explain such variation, but most such studies have been done on eastern ocean boundary coasts. We investigated possible benthic–pelagic coupling along the Atlantic coast of Nova Scotia, a western ocean boundary coast. In 2014, we surveyed high‐intertidal habitats from nine wave‐exposed bedrock locations spanning 415 km of coastline. At each location in the spring, we measured the recruitment of barnacles and mussels, the two main filter‐feeders. Recruitment varied irregularly along the coast. Satellite data on coastal phytoplankton and particulate organic carbon (food for intertidal filter‐feeders and their pelagic larvae) and in‐situ data on sea surface temperature explained, to varying degrees, the geographic structure of recruitment. In turn, the summer abundance of barnacles and mussels was positively related to their spring recruitment. Ultimately, intertidal predator (dogwhelk) abundance was positively related to the recruitment and/or abundance of barnacles and mussels (the main prey of dogwhelks). Sea ice may also have influenced this predator–prey interaction. Drift ice leaving the Gulf of St. Lawrence in late winter strongly disturbed the northern surveyed locations, making barnacles (through high spring recruitment) the only food source for dogwhelks (which survived ice scour in crevices) in such places. Overall, this study supports the occurrence of benthic–pelagic coupling and bottom‐up forcing on this coast. Investigating the oceanographic drivers of pelagic food supply and seawater temperature should help to further understand how this large metacommunity is organized. [ABSTRACT FROM AUTHOR]

Predator chemical cues can elicit behavioral changes in prey to minimize predation risk. Recent field studies have shown that such predator nonconsumptive effects (NCEs) can ultimately affect prey demography. The environment is known to modulate predator consumptive effects on prey demography, but the environmental modulation of predator NCEs on prey demography remains unstudied. We investigated this knowledge gap using an intertidal predator-prey system. Dogwhelk (Nucella lapillus) chemical cues can limit barnacle (Semibalanus balanoides) recruitment by limiting larval settlement. As waves disperse chemicals in coastal environments, we experimentally tested the hypothesis that wave exposure limits dogwhelk NCEs on barnacle recruitment. Shortly before the barnacle recruitment season of 2013 (May-June), we established cages in rocky intertidal habitats in Atlantic Canada under two levels of wave exposure. The cages were used to manipulate the presence and absence of dogwhelks. At the center of each cage, we installed a tile where barnacle pelagic larvae could settle and develop into recruits. Mesh prevented caged dogwhelks from accessing the tiles, but allowed their waterborne cues to reach the tiles. Data collected at the end of the recruitment season indicated that dogwhelk cues limited barnacle recruitment in wave-sheltered habitats but had no effect on recruitment in wave-exposed habitats. These findings suggest that predicting predator NCEs on prey demography may require environmental information related to the ability of prey to locate predators. [ABSTRACT FROM AUTHOR]

Environmental stress can influence species traits and performance considerably. Using a seaweed-snail system from NW (Nova Scotia) and NE (Helgoland) Atlantic rocky shores, we examined how physical stress (wave exposure) modulates traits in the seaweed Fucus vesiculosus and indirectly in its main consumer, the periwinkle Littorina obtusata., In both regions, algal tissue toughness increased with wave exposure. Reciprocal-transplant experiments showed that tissue toughness adjusted plastically to the prevailing level of wave exposure., Choice experiments tested the feeding preference of snails from sheltered, exposed and very exposed habitats for algae from such wave exposures. Snails from exposed and very exposed habitats consumed algal tissues at similar rates irrespective of the exposure of origin of the algae. However, snails from sheltered habitats consumed less algal tissues from very exposed habitats than tissues from sheltered and exposed habitats. Choice assays using reconstituted algal food (triturated during preparation) identified high thallus toughness as the explanation for the low preference of snails from sheltered habitats for algae from very exposed habitats., Ultrastructural analyses of radulae indicated that rachidian teeth were longest and the number of cusps in lateral teeth (grazing-relevant traits) was highest in snails from very exposed habitats, suggesting that radulae are best suited to rupture tough algal tissues in such snails., No-choice feeding experiments revealed that these radular traits were also phenotypically plastic, as they adjusted to the toughness of the algal food., Synthesis. This study indicates that the observed plasticity in the feeding ability of snails is mediated by wave exposure through phenotypic plasticity in the tissue toughness of algae. Thus, plasticity in consumers and their resource species may reduce the potential effects of physical stress on their interaction. [ABSTRACT FROM AUTHOR]

We determined the distribution of two cryptic mussel species (Mytilus edulisandM. trossulus) along full gradients of wave exposure in northwest Atlantic rocky intertidal habitats. Research was conducted in Nova Scotia (Canada) and Maine (United States) and species were determined using genetic analyses. In very sheltered habitats, onlyM. edulisoccurred. In sheltered, exposed, and very exposed habitats, both species co-existed,M. edulispredominating in Maine andM. trossulusin Nova Scotia. Hybrids were absent or rare. The distribution of mussels regardless of species (Mytilusspp.) was remarkably consistent across levels of wave exposure in both regions. In very sheltered habitats, organisms were large (4–5 cm long, on average) and old (7–8 years, on average) and occurred in low densities. In sheltered, exposed, and very exposed habitats, organisms were small (< 1 cm, on average) and young (1–2 years, on average); density was low in sheltered and very exposed habitats, but high in exposed habitats. Abundance data for predatory snails (dogwhelks,Nucella lapillus) and canopy-forming algae (Ascophyllum nodosumandFucusspp.) suggest that predation and facilitation may explain some of the observed changes in mussel population traits along the wave exposure gradients. Our results could be useful as baseline information to predict the effects of the progressive increase in wave action caused by climate change on intertidal mussel populations. [ABSTRACT FROM AUTHOR]

This data set describes the abundance of 50 invertebrate taxa found in intertidal mussel beds along the Atlantic Canadian coast. This information resulted from a regional‐scale study that investigated the effects of wave exposure on the richness and composition of invertebrate assemblages from intertidal mussel beds. Abundance data are provided for taxa representing the Annelida, Arthropoda, Bryozoa, Chordata, Cnidaria, Echinodermata, Mollusca, Nematoda, Nemertea, and Platyhelminthes. The data characterize mussel beds from wave‐sheltered and wave‐exposed locations spanning 315 km of the coast of Nova Scotia. Univariate and multivariate analyses revealed that the compositional structure of these invertebrate assemblages differed markedly depending on wave exposure. Overall, because of its taxonomic diversity, the inclusion of data for basal, intermediate, and top trophic levels, and the coverage of two extremes of environmental stress, this data set could be useful to test broader aspects of ecological theory. Areas of ecology that could advance using this data set are those concerning environmental stress models of community organization, abundance–occupancy relationships, species co‐occurrence, species abundance distributions, dominance and rarity, spatial scales of population and community variation, and distribution of functional and phylogenetic diversity. Use of this data set for academic or educational purposes is allowed as long as the data source is properly cited. When used for academic or educational purposes, this data set should be cited using the title of this Data Paper, the names of the authors, the year of publication, and the corresponding volume and article numbers. [ABSTRACT FROM AUTHOR]