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In February 2023, a severe cold snap took place in Atlantic Canada and was followed by the mass loss of mussels at mid-to-high intertidal elevations on the southeastern Nova Scotia coast. This loss was concerning because mussels sustain upper trophic levels in coastal food webs and because mussel stands enhance local biodiversity by sheltering many small invertebrate species. Using photographs taken in the second summer after that cold snap (July 2024), this article provides visual evidence of active ongoing recolonization of intertidal mussels on this coast, including the incipient formation of new stands. These are encouraging signs of ecological resilience. Reaching historical values of abundance will likely depend on the future occurrence of weather extremes, which are becoming more frequent with the ongoing climate change. [ABSTRACT FROM AUTHOR]

In the early summer of 2021, an intense heatwave killed millions of intertidal mussels in British Columbia, Canada. Using photographs taken three years later (June 2024), this article provides visual evidence of active recovery of intertidal mussel stands in the Vancouver region, revealing the resilience of these intertidal systems. Future monitoring should evaluate their ability for long-term persistence in light of the ongoing climate change, which is expected to increase the frequency and intensity of heatwaves. [ABSTRACT FROM AUTHOR]

Rocky intertidal habitats occur worldwide and are mainly characterized by primary space holders such as seaweeds and sessile invertebrates. Some of these organisms are foundation species, as they can form structurally complex stands that host many small invertebrates. The abundance of primary space holders is known to vary along coastlines driven directly or indirectly by environmental variation. However, it is less clear if the invertebrate assemblages associated to a foundation species may remain relatively unchanged along coastlines, as similar stands of a foundation species can generate similar microclimates. We examined this question using abundance data for invertebrate species found in mussel stands of a similar structure in wave-exposed rocky habitats at mid-intertidal elevations along the Atlantic coast of Nova Scotia (Canada). While the most abundant invertebrate species were found at three locations spanning 315 km of coastline, species composition (a combined measure of species identity and their relative abundance) differed significantly among the locations. One of the species explaining the highest amount of variation among locations (a barnacle) exhibited potential signs of bottom-up regulation involving pelagic food supply, suggesting benthic–pelagic coupling. The abundance of the species that explained the highest amount of variation (an oligochaete) was positively related to the abundance of their predators (mites), further suggesting bottom-up forcing in these communities. Overall, we conclude that species assemblages associated to structurally similar stands of a foundation species can show clear changes in species composition at a regional scale. [ABSTRACT FROM AUTHOR]

Broadly distributed species need to perform well in a range of environmental conditions, but knowledge of how wide‐ranging marine larvae perform along latitudinal gradients remains limited. The fatty acid composition of larvae is important for their physiological responses to changing conditions. Here, we investigated the fatty acid composition of the last, non‐feeding stage of barnacle larvae (cyprids) using an integrative (larvae–environment) and comparative (latitudinal) approach. We measured fatty acids in the pelagic particulate matter and cyprids from Chthamalus bisinuatus, Chthamalus proteus, and Semibalanus balanoides from tropical to polar (Arctic) latitudes to identify potential food sources during the feeding larval stages (nauplius) that precede the cyprids and to ascertain larval capacity to integrate neutral (energetic) and polar (structural) fatty acids. We demonstrate that particulate matter in tropical waters mainly consisted of low‐quality saturated fatty acids derived from detrital pathways, while particulate matter from polar waters was rich in polyunsaturated fatty acids originating from living microalgae. Across the studied regions, neutral fatty acids were assimilated from various food sources including diatoms, dinoflagellates, detritus, and microeukaryotes. Cyprids consistently retained higher essential fatty acid levels than the relative share in the particulate matter. Particularly, the essential docosahexaenoic acid (22:6ω3), which was scarce in the particulate matter, was highly retained across all species but highest for the tropical cyprids. We argue that this latitudinal pattern in fatty acid retention is related to periods of reduced nutrient intake, increased energetic and/or synthetic requirements, and responses to physical large‐scale differences in environmental conditions. [ABSTRACT FROM AUTHOR]

This article discusses the mass disappearance of intertidal mussels in eastern Canada after an unusual winter cold snap in February 2023. The decline in mussel abundance is concerning due to its impact on coastal biodiversity. The cold snap, which saw temperatures drop below -20°C, is believed to be the main driver of the mass disappearance. Other factors such as predation, ice scour, and wave action were ruled out as causes. The article highlights the potential implications of climate change on the future of coastal ecosystems and emphasizes the need to study the frequency of extreme weather events. [Extracted from the article]

Intertidal mussel stands are common on temperate rocky seashores and host many small invertebrates, so they are important biodiversity reservoirs. Their integrity, however, is being increasingly affected by environmental extremes. An unusual cold snap in Nova Scotia (Canada) in February 2023 was followed by the mass disappearance of mussel stands at mid-to-high elevations in rocky intertidal habitats. The present article presents evidence of significant losses at middle intertidal elevations following the passage of cyclone Lee in September 2023, which created severe surf conditions. The increasing occurrence of successive environmental extremes might challenge the persistence of these important biological systems. [ABSTRACT FROM AUTHOR]

Contemporary climate change is increasing the occurrence of extreme weather events, heat waves being common examples. Here, we present visual evidence of mass bleaching in intertidal seaweeds following an unusually severe cold snap in Atlantic Canada. In February 2023, the air temperature on the Nova Scotia coast dropped below −20 °C for the first time in at least ten years. Such extreme temperatures lasted for several hours at low tide and were followed by extensive bleaching in whole thalli of the canopy-forming algae Chondrus crispus and Corallina officinalis. The loss of these foundation species might negatively impact intertidal biodiversity. [ABSTRACT FROM AUTHOR]

Beta diversity measures the spatial variation in species composition. Because it influences several community attributes, studies are increasingly investigating its drivers. Spatial environmental heterogeneity is a major determinant of beta diversity, but canopy‐forming foundation species can locally modify environmental properties. We used intertidal communities dominated by the canopy‐forming alga Mazzaella laminarioides as a model system to examine how a foundation species affects spatial environmental heterogeneity and the resulting beta diversity. Since canopies were found to reduce the spatial variation of temperature and desiccation during low tides, we hypothesized that canopies would decrease understory beta diversity, which we tested through a field experiment that contrasted canopy removal with presence treatments over 32 months. The beta diversity of sessile species was always lower under canopies, but canopies never affected the beta diversity of mobile species. The observed responses for sessile species may result from their abundance being more dependent on spatial abiotic variation than for mobile species, which can occur in stressful areas while temporarily foraging or in transit to other areas. These responses may likely apply to other systems exhibiting canopy‐forming foundation species hosting sessile and mobile species assemblages. [ABSTRACT FROM AUTHOR]

Nonconsumptive predator effects on prey behaviour are common in nature, but the possible influence of prey life-history stage on such responses is poorly known. We investigated whether prey life-history stage may be a factor affecting prey feeding activity responses to predator chemical cues, for which we used dogwhelks (Nucella lapillus (L., 1758)) and their main prey, barnacles (Semibalanus balanoides (L., 1758)), as a model system. Barnacles use their modified legs (cirri) to filter food from the water column. Through a manipulative laboratory experiment, we tested the hypothesis that the presence of dogwhelks affects the frequency of leg swipes differently in juvenile and adult barnacles. Juveniles showed a similar feeding activity with and without nearby dogwhelks, but adults exhibited a significantly lower frequency of leg swipes when dogwhelks were present. Such an ontogenetic change in the response of barnacles to predatory cues might have evolved as a result of dogwhelks preferring adult barnacles over juvenile barnacles, as found previously. Alternatively, barnacles could learn to recognize predator cues as they age, as shown for other prey species. Overall, our study indicates that the nonconsumptive effects of predators on prey need to be fully understood under consideration of the possible ontogenetic changes in prey responses to predator cues. Les effets des predateurs, autres que la consommation de la proie, sur le comportement des proies sont courants en nature, mais l'influence possible du stade du cycle biologique de la proie sur ces effets reste mal connue. Nous examinons si le stade du cycle biologique de la proie peut etre un facteur qui affecte les reactions d'alimentation des proies a la presence de signaux chimiques de predateurs en utilisant des pourpres de l'Atlantique (Nucella lapillus (L., 1758)) et leur proies principales, les balanes communes (Semibalanus balanoides (L., 1758)) comme systeme modele. Les balanes utilisent leurs partes modifiees (cirres) pour extraire leur nourriture par filtration de la colonne d'eau. Lors d'une experience de manipulation en laboratoire, nous avons teste l'hypothese selon laquelle la presence de pourpres affecte la frequence de balayage des cirres differemment chez les balanes jeunes et adultes. Les jeunes ont une activite alimentaire semblable, que les pourpres soient presents a proximite ou non, mais les adultes ont une frequence de balayage des pattes significativement reduite en presence des pourpres. Une tel changement ontogenique dans la reaction des balanes aux signaux de predation des pourpres peut s'etre developpe du fait que les pourpres preferent les balanes adultes aux jeunes, comme on l'a demontre anterieurement. D'un autre cote, les balanes pourraient avoir appris avec l'age a reconnaitre les signaux des predateurs, comme c'est le cas chez d'autres especes de proies. Globalement, notre etude indique que pour pleinement comprendre les effets (autres que la consommation de la proie) des predateurs sur les proies, il est necessaire de tenir compte des changements ontologiques possibles dans les reactions des proies aux signaux des predateurs. [Traduit par la Redaction], Introduction Predator-prey interactions are often important in structuring communities. Most research on predator influences has focused on the consumption of prey, which generally leads to the mortality of prey organisms [...]