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Predators affect their prey through consumptive and non-consumptive effects (NCEs). Regarding marine NCEs, predator chemical cues (e.g., exudates) can trigger various anti-predator responses in prey that can vary in magnitude according to the intensity of the perceived cues. Specimens of the mussel Perumytilus purpuratus were exposed to seawater that held different densities of the predatory snail Acanthina monodon as a proxy for predator cue intensity. The response of mussels was quantified in terms of valve gape size (VGS), clearance rate (CR), and oxygen consumption rate (OCR). The results showed that mussels reduced VGS, CR, and OCR as a function of the intensity of the predator exudates to which they were exposed. These results suggest that mussels are not only able to detect predators through their chemical exudates but can also detect the intensity of the predatory signal and thus respond physiologically (CR, OCR) and behaviorally (VGS) in accordance to the potential predation risk. These responses may have cascading effects at the community level, given that mussels are foundation species. [ABSTRACT FROM AUTHOR]

Foundation species are spatially dominant species that increase habitat complexity and provide substrate and shelter for many smaller species. Through a mensurative field experiment, we tested the hypothesis that functional aspects of the associated communities are related to structural and functional properties of the foundation species. Specifically, we contrasted invertebrate communities living in mussel (Mytilus) and seaweed (Chondrus) stands from the same rocky intertidal environments in Atlantic Canada. Both stands reach similar heights above the substrate, but they differ structurally (rigid mussel shells vs. flexible seaweed fronds) and functionally (mussels generate biowaste while seaweeds offer food for herbivores). Our data supported the hypothesis in various ways. Detritivory (mostly by oligochaetes) was more prevalent in mussel stands, while herbivory was more prevalent in seaweed stands. Predators were mostly mites and, consequently, they were more prevalent in mussel stands, as mites eat oligochaetes. Functional traits related to body and mobility types were also related to properties of the foundation species. Overall, we conclude that structural and functional properties of foundation species can predict functional aspects of the associated communities. This concept may help to develop effective restoration strategies after the loss of foundation species due to anthropogenic factors. [ABSTRACT FROM AUTHOR]

Mussels form extensive beds in rocky intertidal habitats on temperate seashores worldwide. They are foundation species because their beds host many invertebrates. Mussels and their associated species differ taxonomically among biogeographic regions, but all mussel beds exhibit similar structural and functional properties. Therefore, we investigated if rocky-intertidal mussel beds from around the globe host associated communities that are functionally similar despite their underlying taxonomic differences. We gathered datasets on the abundance of invertebrates found in rocky-intertidal mussel beds from the eastern and western boundaries of the Pacific and Atlantic Oceans from both hemispheres and, then, we compared their taxonomic and functional properties. Taxonomic composition differed markedly among coasts when analyzed at the taxonomic resolution reported by the surveys (often species). However, taxonomic groups with similar ecologies (28 groups including barnacles, decapods, gastropods, polychaetes, etc.) were more universally present in mussel beds. Concomitantly, functional categories of trophic level, body type, and mobility were almost always present on all studied coasts. These taxonomic groups and trait categories, however, showed regional patterns based on their relative abundances. Overall, the ability of mussel beds to host a core community type based on taxonomic groups and functional traits emphasizes their importance for biodiversity and community functioning, making them critical organisms to preserve. [ABSTRACT FROM AUTHOR]

Benthic fauna refers to all fauna that live in or on the seafloor, which researchers typically divide into size classes meiobenthos (32/64 µm–0.5/1 mm), macrobenthos (250 µm–1 cm), and megabenthos (>1 cm). Benthic fauna play important roles in bioturbation activity, mineralization of organic matter, and in marine food webs. Evaluating their role in these ecosystem functions requires knowledge of their global distribution and biomass. We therefore established the BenBioDen database, the largest open-access database for marine benthic biomass and density data compiled so far. In total, it includes 11,792 georeferenced benthic biomass and 51,559 benthic density records from 384 and 600 studies, respectively. We selected all references following the procedure for systematic reviews and meta-analyses, and report biomass records as grams of wet mass, dry mass, or ash-free dry mass, or carbon per m2 and as abundance records as individuals per m2. This database provides a point of reference for future studies on the distribution and biomass of benthic fauna. Measurement(s) marine benthic feature • organic material • mass density Technology Type(s) digital curation Factor Type(s) geographic location • water depth • organism size class Sample Characteristic - Organism meiobenthos • macrobenthos • megabenthos Sample Characteristic - Environment marine benthic biome • ocean Sample Characteristic - Location Atlantic Ocean • Pacific Ocean • Arctic Ocean • Southern Ocean • Indian Ocean Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.12481985 [ABSTRACT FROM AUTHOR]

Predators often have nonconsumptive effects (NCEs) on prey. For example, upon detection of predator cues, prey can reduce feeding activities to hamper being detected by predators. Previous research showed that waterborne chemical cues from green crabs (Carcinus maenas, predator) limit the dogwhelk (Nucella lapillus, prey) consumption of barnacles regardless of dogwhelk density, even though individual predation risk for dogwhelks decreases with conspecific density. Such NCEs might disappear with dogwhelk density if dogwhelks feed on mussels, as mussel stands constitute better antipredator refuges than barnacle stands. Through a laboratory experiment, we effectively found that crab chemical cues limit the per-capita consumption of mussels by dogwhelks at low dogwhelk density but not at high density. The combination of tactile and chemical cues from crabs, however, limited the dogwhelk consumption of mussels at both dogwhelk densities. The occurrence of such NCEs at both dogwhelk densities could have resulted from tactile cues indicating a stronger predation risk than chemical cues alone. Overall, the present study reinforces the notions that prey evaluate conspecific density when assessing predation risk and that predator cue type affects their perception of risk. [ABSTRACT FROM AUTHOR]

Mussels often act as ecosystem engineers in rocky intertidal habitats, favoring the occurrence of many small invertebrates by increasing habitat complexity and improving local environmental conditions. This study tests the hypothesis that invertebrate assemblages from intertidal mussel beds differ between wave-sheltered and wave-exposed habitats. To this aim, we surveyed exposed and sheltered sites spanning 350 km of coastline in Nova Scotia, Canada. We identified all invertebrates and measured their abundance in replicate quadrats that were fully covered by mussels. In total, we found 50 invertebrate taxa living in these mussel beds. Multivariate analyses revealed that the composition of invertebrate assemblages differed significantly between both habitat types. Exposed habitats supported a greater species richness, and the species that mainly explained the compositional difference between both environments were more abundant in exposed ones. Assemblages were taxonomically dominated by arthropods, annelids, and molluscs and numerically dominated by tubificid oligochaetes regardless of exposure. Our results suggest that exposed habitats may favor the occurrence of filter-feeders, such as barnacles, and sheltered habitats the occurrence of predators, such as small crabs and sea stars, in intertidal mussel beds from the NW Atlantic coast. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We investigated the effects of elevation, wave exposure, and year on the proportion of gametophytes and tetrasporophytes in populations of the intertidal red seaweed Mazzaella parksii (= M. cornucopiae, Gigartinaceae) from the Pacific coast of Canada. In July 2002, we determined the life-history phase of 864 frond samples from four populations from Barkley Sound, using the resorcinol-acetal test. For these populations, gametophytes were significantly more numerous than tetrasporophytes, and the proportion of gametophytes was significantly higher at higher elevations. The proportion of gametophytes varied directly (although less markedly) with the degree of wave exposure, but significance could not be assessed for this factor. All of these patterns were spatially consistent, as they held for two different rocky points with similar physical characteristics. One of these points had also been surveyed in 1994-1995, which allows us to conclude that the population-wise gametophyte predominance and the positive relationship between elevation and the proportion of gametophytes are stable features of this species in this area. However, the average proportion of gametophytes was similar between the studied levels of wave exposure in 1994–1995; such a difference revealed as non-significant when data were combined with those for 2002. This suggests that wave exposure is not important in determining the proportion of life-history phases for this species. Comparisons with other species are done in search of general patterns for the Gigartinaceae. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Marine invertebrate herbivores occasionally prefer particular tissues of a given seaweed depending on tissue age. For the intertidal alga Mazzaella parksii (=M. cornucopiae), however, important tissue differences result from abiotic stress: distal tissues of many fronds become bleached under strong irradiance and desiccation during spring and summer low tides. Snails of the genus Littorina (periwinkles) are significant grazers of M. parksii. Through a multiple-choice feeding-preference experiment, we found that periwinkles actively consume bleached tissues, but almost no photosynthetic tissues. This suggests that bleached tissues of M. parksii may support Littorina populations to a good extent during spring and summer. In addition, since photosynthetic tissues are basal, the impact of periwinkles on frond mortality might be lower than if they preferred photosynthetic tissues. Photosynthetic tissues are actively consumed by periwinkles when they are the only food choice, as shown by other researchers. Therefore, retaining bleached tissues for some time might have evolved in M. parksii to divert grazing pressure away from vital tissues. [ABSTRACT FROM AUTHOR]

The seaweed Mazzaella cornucopiae (Postels & Ruprecht)Hommersand is common in rocky intertidal areas from Pacific Canada andis a potential economic resource. In both 1993 and 1994, the abundanceof M. cornucopiae from Prasiola Point, southern Barkley Sound, washigh in spring and summer and low in fall and winter. In 1995, however,the abundance in summer was unexpectedly low, and this trend deepenedin 1996. Correlations between the temporal changes of abundance and ofsome abiotic variables were done as a first approach to explaining thesechanges of abundance. The abiotic variables used were air temperature,sea surface temperature, wave height, all three measured on an oceanicbuoy close to Prasiola Point, and seawater salinity, determined for coastalwaters from northern Barkley Sound. These were the closest sites toPrasiola Point for which reliable abiotic data existed. None of thecorrelations were significant. Field observations done at Prasiola Pointsuggest that air temperatures reached higher values there than at theoceanic buoy. Together with irradiance, in situ air temperature may havehad an important role in the interannual differences of abundance througha higher physical stress on thalli, resulting in the high proportion ofbleached tissues observed in summer 1996. Future studies on thepopulation dynamics of M. cornucopiae should benefit fromquantifying these variables in situ. [ABSTRACT FROM AUTHOR]

Canopy-forming seaweeds are important foundation species or ecosystem engineers in intertidal habitats. By limiting a variety of abiotic stresses during low tides, algal canopies improve the performance of many understory organisms. The reduction of heat stress through substrate shading and moisture retention has received considerable attention in marine biology. However, the thermal influence of canopies during winter has not been empirically evaluated. Using intertidal fucoid canopies (Ascophyllum nodosum) from Atlantic Canada, we did a field experiment contrasting canopy-covered and no-canopy areas to test the hypothesis that canopies limit low temperatures during winter low tides. During 35 days between January and March, mid-intertidal temperature was often negative near the time of the lowest daily tides, on average more than 1 °C lower on bare substrate than under full canopy cover. The difference between both canopy treatments was higher around spring tides than around neap tides. Temperature on bare substrate was once even up to 10 °C lower than under a full canopy. Previous studies have shown that single occurrences of lethal negative temperatures and frequent occurrences of sublethal temperatures kill intertidal organisms every winter. Thus, our study suggests that, in addition to their bioprotective role during summer, canopy-forming seaweeds might also play a relevant facilitative role during winter. [ABSTRACT FROM AUTHOR]