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The urbanisation of coastal areas increases both Artificial Light At Night (ALAN) and man-made structures. ALAN poses significant challenges to coastal ecosystems by altering species physiology and behaviour. Its effects might differ considerably between man-made and natural habitats due to varying habitat complexity and biological assemblages. This systematic review assesses the current knowledge and gaps regarding the ecological effects of the interaction between ALAN and different coastal hard-bottom habitats on intertidal and shallow-subtidal reefs. Of the 57 retrieved studies, most are laboratory experiments (40) on the physiology and behaviour of rocky shore (24) or coral reef (16) species. Field studies were conducted in artificial (6) and natural habitats (9), with only 2 comparing the two habitat types. These studies illustrate ALAN impacts on various species, with potential cascading effects on entire communities through the alteration of competitive and consumer-resource interactions. Different habitat structures may interact with ALAN by generating highly heterogeneous lightscapes (e.g., natural rocky shores), regular light-shadow mosaics (e.g., breakwaters), vast homogeneously lit areas (e.g., seawalls), or constantly shaded areas (e.g., pontoons). This creates a variable mismatch in natural light conditions, which may be further influenced by the introduction of additional light sources (e.g., moored boats with underwater coloured lights). As coastal development and light pollution continue to grow, research should prioritise understanding their interactive effects in shaping species relationships and ecosystem dynamics. Although the available evidence suggests that ALAN effects may vary between natural and man-made habitats, further research is needed to draw any general conclusion. [ABSTRACT FROM AUTHOR]

An observational study comparing beach reflection characteristics for sea‐swell waves along six rocky and three sandy shores, spanning from Monterey to Santa Cruz, CA, shed light on the previously unknown wave reflection along rocky shores. Wave reflection is derived from directional spectra acquired via several surface GPS‐based wave buoys. Owing to the Lagrangian nature of the buoy, they were validated r2=0.7 $\left({r}^{2}=0.7\right)$ against Eulerian beam velocities from a bottom‐mounted acoustic Doppler current profiler, providing a spatial array for more degrees of freedom in resolving wave direction and now including adjustment for instrument tilt. Reflection varies across shoreline types: sandy shores (< ${< } $20%), rough, rocky shores (< ${< } $10%), rocky shores with cliffs (< ${< } $15%), and rocky platforms with cliffs (< ${< } $30%). Contrary to expectations, rocky shores exhibit minimal reflection. Existing reflection estimators developed for sandy shores are found inadequate for rocky shores r2=0.23;RMSE=6.4 $\left({r}^{2}=0.23\mathrm{;}\,\mathrm{R}\mathrm{M}\mathrm{S}\mathrm{E}=6.4\right)$, necessitating a new estimator considering beach slope, wave steepness, and shoreline rugosity r2=0.63;RMSE=0.05 $\left({r}^{2}=0.63\mathrm{;}\,\mathrm{R}\mathrm{M}\mathrm{S}\mathrm{E}=0.05\right)$. Beach reflection is limited by the dissipation of incident waves due to bottom friction and depth‐limited wave breaking as well as by the reduction in reflected waves caused by wave trapping. Observed reflection increased offshore on all beaches attributed to sea‐swell waves' resonant interaction with the rough rocky bottom, causing backward Bragg scattering. The Bragg scattering was less on larger‐sloped bottoms, attributed to larger slopes hindering effective wave‐bottom interactions. Plain Language Summary: Approximately 75% of global shores are rocky, featuring rougher bottoms and steeper beaches compared to sandy shores, thus expecting larger wave reflections. Directional spectra are obtained using numerous surface‐floating GPS‐based wave buoys. The directional spectra are partitioned into onshore and offshore directions to calculate wave reflection. These buoys were validated against stationary bottom‐mounted acoustic Doppler current profilers, adapting a directional wave method to accommodate instrument tilt. Reflection estimates align well between the measurement platforms. Twenty‐two wave buoys were deployed across three experiments, revealing varied reflection patterns among rocky and sandy shores with higher reflection on sandy shores during high tides and rocky platforms with cliffs. A new reflection estimator yields reasonable estimates for both sandy and rocky shores. The study investigates factors influencing wave reflection characteristics. Wave reflection increased offshore on all beaches, attributed to backward Bragg scattering, but was limited by wave trapping caused by the offshore‐propagating waves refracted back to the shore. Bragg scattering occurs when ocean waves interact with the rough rocky seabed, causing the waves to scatter and create reflected wave components at specific angles related to the wavelength and the surface roughness. The result was generally a weak reflection on both sandy and rocky shores. Key Points: Observed wave energy reflection is generally low on all beaches owing to breaking wave dissipation and refractive wave trappingBackward Bragg scattering is estimated as a significant contributor to observed wave reflection though much is lost to wave trappingNew wave reflection estimators, including beach slope, wave steepness, and shoreline rugosity, are proposed for rocky and sandy shores [ABSTRACT FROM AUTHOR]

Intertidal macroalgae define complex habitats and play a key role in structuring coastal areas. While, they are primarily studied during field campaigns, remote sensing acquisitions are becoming increasingly prevalent. However, the use of hyperspectral imagery on drones is not developed even though it allows species identification even in heterogeneous environments such as intertidal rocky shores. Based on hyperspectral drone imagery acquired in summer 2021, this study aims to identify and validate an algorithm suitable for easy integration into an operational framework for monitoring macroalgal dominated shore. The study focuses on two sites along the Brittany coast (Western France). Species identification and abundance were determined in the field. Six algorithms were tested: Mahalanobis, Minimum Distance, Maximum Likelihood, Random Forest, Spectral Angle Mapper and Support Vector Machine. Classifications showed overall accuracies ranging from 70% to 90% depending on the algorithm. The Maximum Likelihood is retained as it provides good accuracies and valuable information about the species distributions. Our analyses based on a combination of field and remote sensing data reveals globally consistent results when considering the main Phaeophyceae species but a divergence was highlighted for Rhodophyta. Despite environmental differences, the two studied sites were faithfully characterized in terms of intertidal species and habitat distribution, highlighting the potential of hyperspectral drone imagery to better understand seaweed-dominated ecosystem dynamics. [ABSTRACT FROM AUTHOR]

Aim: The poleward range expansion of tropical species, and range contraction of temperate species (known as tropicalisation) has mainly been studied from an ecological perspective, with little research on its genetic consequences. Here, we used distributional and genetic data to document the consequences of tropicalisation in rocky shore gastropods and assess more broadly the future implications of tropicalisation on phylogeographic patterns. Location: Nineteen sampling sites along >3000 km of the eastern Pacific rocky intertidal zone, from the tip of the Baja California Peninsula to southern California. Taxon: Temperate gastropods: Lottia conus, L. strigatella, Fissurella volcano and Tegula gallina. Tropical gastropods: Fissurella rubropicta, Nerita funiculata and N. scabricosta. Methods: We determine historical and modern distributions of tropical and temperate species by combining historical records with current field surveys. Using a section of the cytochrome oxidase subunit I gene, we utilised comparative phylogeography, analysis of molecular variance, FST pairwise comparison, mismatch distributions of haplotype differences and neutrality tests to detect genetic signatures of tropicalisation and to better understand its consequences. Results: We identified range contractions in two temperate species and range expansion in all three tropical species. We detected genetic signatures of range expansion in the tropical species through unimodal distributions of pairwise haplotype differences and strongly negative values for the Fu and Li D and F* statistics. We found population subdivision and phylogeographic breaks in three temperate species, although the geographic location of the breaks differed among species. Main Conclusions: Genetic signatures and field surveys indicate recent range expansions in tropical species, supporting tropicalisation along the studied coastline. Conversely, we found phylogeographic breaks in temperate species, suggesting that tropicalisation may cause genetic erosion of evolutionary distinct lineages with range‐contraction. The different locations of the phylogeographic breaks among temperate species suggests that some barriers are species specific. [ABSTRACT FROM AUTHOR]

The distribution of genetic diversity is often heterogeneous in space, and it usually correlates with environmental transitions or historical processes that affect demography. The coast of Chile encompasses two biogeographic provinces and spans a broad environmental gradient together with oceanographic processes linked to coastal topography that can affect species' genetic diversity. Here, we evaluated the genetic connectivity and historical demography of four Scurria limpets, S. scurra, S. variabilis, S. ceciliana and S. araucana, between ca. 19° S and 53° S in the Chilean coast using genome‐wide SNPs markers. Genetic structure varied among species which was evidenced by species‐specific breaks together with two shared breaks. One of the shared breaks was located at 22–25° S and was observed in S. araucana and S. variabilis, while the second break around 31–34° S was shared by three Scurria species. Interestingly, the identified genetic breaks are also shared with other low‐disperser invertebrates. Demographic histories show bottlenecks in S. scurra and S. araucana populations and recent population expansion in all species. The shared genetic breaks can be linked to oceanographic features acting as soft barriers to dispersal and also to historical climate, evidencing the utility of comparing multiple and sympatric species to understand the influence of a particular seascape on genetic diversity. [ABSTRACT FROM AUTHOR]

Intertidal rock pools support diverse assemblages. While there is much research on the importance of rock pools in supporting mobile diversity on rocky shores, there is limited knowledge regarding the role of physical features (microhabitats) within these habitats. Understanding the features of pools that support diversity is crucial to conserve and potentially mimic these important intertidal habitats in restoration projects. Here, we classified and quantified the types of physical features, hereafter "microhabitats" (overhangs and pits), within rock pools at different locations in and around a highly urbanised estuary, Sydney Harbour, Australia. The use of different microhabitats within rock pools by mobile macro-invertebrates was also examined in one location. We surveyed natural rock pools in summer (2 times) and winter (2 times) at seven sites: two sites from each of the inner and outer zones of Sydney Harbour, and three sites along the open coast of Sydney. We found that the type and size of microhabitats within pools decreased from the coastal towards inner harbour sites. Along the open coast, the richness of mobile taxa increased in rock pools with overhangs or pits. Only rock pools with overhangs had increased mobile abundances, likely driven by the gastropod Nerita melanotragus. Several species occurred in greater frequency in pools with overhangs. There was no effect of pits on abundances. This survey suggests that some microhabitats may play an important role in the diversity and abundance of mobile macro-invertebrates in rock pools. A detailed understanding of the local and regional scales of microhabitats should be used to inform eco-engineering of intertidal foreshores. [ABSTRACT FROM AUTHOR]

Phyllospadix spp. play a crucial role in the supply of ecosystem services in rocky shores, but they have been rapidly reduced because of natural and anthropogenic causes. Since Phyllospadix spp. are attached to rocks in the surf zone with a strong hydrodynamic condition, their transplanted shoots easily disappear due to the high current velocity, resulting in the failure of transplantation. We described a leaf trimming method for transplanting shoots of surfgrass Phyllospadix iwatensis and evaluated the method’s establishment success for potential use in large-scale restoration projects. A 30-day laboratory experiment was conducted to determine the effect of leaf trimming on shoot survival, growth, and physiology. Successful establishment of new patches from shoots transplanted with the leaf trimming method was assessed through a shoot-transplanting field experiment over 15 months. The survival of P. iwatensis shoots was not significantly affected by the leaf trimming proportion of 10%–60%. The leaf elongation rate and total leaf area of the shoots exposed to 10%–50% leaf trimming reached or exceeded those of the control at the end of the laboratory experiment; however, the growth of the shoots under 60% leaf trimming was significantly lower than those under the control (p < 0.05). The soluble sugar and starch contents of the shoots also displayed a similar trend to the growth, with the lowest values attained at 60% of leaf trimming. The survival rate of shoots exposed to 50% leaf trimming treatment was 70% after 15 months following transplantation, which was 1.23 times higher than that of shoots in the control (p < 0.05). The shoot height in the 50% leaf trimming treatment was 1.02 times higher than that of shoots in the control at the end of the field experiment. There were no significant differences in photosynthetic pigment contents of P. iwatensis shoots between the leaf trimming treatment and the control (p > 0.05). Our study suggested that the leaf trimming method is an efficient restoration technique for the transplantation of P. iwatensis shoots, and is potentially useful in facilitating large-scale restoration projects.

The intertidal invertebrate community on rocky shores in northern Chile is characterised by a high species richness resulting from the high productivity of this ecosystem. The present study aims to do the first characterisation of invertebrate communities on rocky shores in Antofagasta town and surroundings (23°S), using species co-occurrence and niche-sharing null models, analysis of similarities (ANOSIM) and nonmetric multidimensional scaling (NMDS). The null model results revealed that species associations are not structured, that the existing species do not have the same ecology, which would result in many repeated species by site, and that specificity in their ecological niches exists. The ANOSIM and NMDS revealed the absence of significant differences between sites with human intervention and without human intervention. The obtained results agree with the literature for northern and central Chilean and southern Peruvian rocky shores, and other coastal marine ecosystems with high productivity. [ABSTRACT FROM AUTHOR]

Little is known about the ichthyofauna from intertidal rock pools of the west coast of Africa, especially in the Gulf of Guinea. Rock pools are characteristic habitats of the intertidal zone of structurally complex rocky shores, adding important niche space to coastal fish species. In this study, rock pools of three similar rocky shores of Príncipe Island were sampled to describe the composition, abundance and distribution of fish assemblages and their relation to parameters of pool structure (volume, depth), water mass (temperature, salinity and pH) and biology (algal and coral cover, and biological species richness). A total of 18 fish species and one leptocephalus larva of unknown species, representing 13 families, were observed during sampling. In decreasing order, the five-most-abundant species were the goby Bathygobius burtoni, night sergeant Abudefduf taurus, West African rockhopper Entomacrodus cadenati, sailfin blenny Microlipophrys velifer and Biafra doctorfish Prionurus biafraensis, which together represented 81% of the total number of fish recorded during this study. The four-most-abundant species also proved to be the better adapted to the range of conditions found in rock pools. Overall, larger rock pools with minimal biological cover and higher salinity were found to support higher fish abundance and species richness. Most species individually preferred rock pools with larger volumes, but some presented a degree of habitat specificity, such as the absence or presence of biological cover. Species that were more-active swimmers preferred deeper pools. [ABSTRACT FROM AUTHOR]

Aim: Seascape genomic studies aim to understand how environmental variables shape species diversity through genotype–environment associations. Identifying these effects on lecithotrophic larval species that live in intertidal zones is particularly challenging because they are subject to environmental heterogeneity and anthropogenic events. Here, we evaluate how biotic and abiotic features in the Southwest Atlantic littoral zone can affect a high dispersal species' present and historical demography. Location: Brazilian coast, covering more than 3000 km. Taxon: Perinereis ponteni. Methods: We investigated population genetic diversity, connectivity and past dynamics using 23,300 single‐nucleotide polymorphisms (SNPs) generated using genotyping by sequencing. We tested whether environmental abiotic variables could explain the variance found in genotype frequencies using isolation‐by‐environment (IBE) and landscape association approaches. These data, combined with palaeodistribution simulations and oceanic circulation modelling, were used to infer species demographic history and connectivity patterns. Results: Along with high levels of connectivity detected, we found a genetic boundary in the southeastern region of Brazil around Cabo Frio (Rio de Janeiro), and a cline trend for some loci. The palaeodistribution simulations reveal a spatial refuge in the southeast during the Last Glacial Maximum (21 kya), with the expansion of the northern region. We identified 1421 SNPs with frequencies associated with eight environmental variables, most of which were related to temperature—the main environmental factor determining IBE. Main Conclusions: Perinereis ponteni, a polychaete with high gene flow capability responds to biogeographic barriers, highlighting the importance of biotic and abiotic factors in shaping population connectivity. Furthermore, the effect of temperature indicates that future climate change and ocean warming can hugely impact this species. [ABSTRACT FROM AUTHOR]

The unprecedented rates of current biodiversity loss have motivated a renewed interest in environmental and biodiversity monitoring. The need for sustained monitoring strategies has prompted not only the establisment of new long-term monitoring programmes, but also the rescue of data from historical or otherwise archived sources. Amongst the most valuable datasets are those containing information on intertidal systems, as they are particularly well suited for studying the biological effects of climate change. The Portuguese rocky coast is quite interesting for studying the effects of climate change on the distribution of species due to its geographical orientation, latitudinal patterns in temperature, species richness, species' distribution patterns and availability of historical information. This work aims at providing a comprehensive picture of the distribution and abundance of intertidal macro-invertebrates and macro-algae along the Portuguese rocky coast in the early 2000s.This study provides a description of the rocky shore intertidal biodiversity of the mainland Portuguese coast in the early 2000s. The spatial distribution and semi-quantitative abundance of a total of 238 taxa were assessed at 49 wave-exposed locations. These data provide a comprehensive baseline against which biodiversity changes can be effectively and objectively evaluated.

Abstract We hypothesized congruence in the spatial structure of abundance data sampled across multiple scales for an ecological guild of consumers that exploit similar nutritional and habitat resources. We tested this hypothesis on the spatial organization of abundance of an herbivorous guild of sea urchins. We also examined whether the amount of local along‐shore rocky habitat can explain the observed spatial patterns of abundance. Standardized estimates of abundance of four intertidal sea urchins—Diadema cf. savignyi, Echinometra mathaei, Parechinus angulosus, and Stomopneustes variolaris—were determined by six observers at 105 sites across 2,850 km of coast of South Africa. For each species and observer, wavelet analysis was used on abundance estimates, after controlling for potential biases, to examine their spatial structure. The relationship between local sea urchin abundance and the amount of upstream and downstream rocky habitat, as defined by the prevailing ocean current, was also investigated. All species exhibited robust structure at scales of 75–220 km, despite variability among observers. Less robust structure in the abundances of three species was detected at larger scales of 430–898 km. Abundance estimates of sympatric populations of two species (D. cf. savignyi and E. mathaei) were positively correlated with the amount of rocky habitat upstream of the site, suggesting that upstream populations act as larval sources across a wide range of scales. No relationship between abundance and habitat size was found for P. angulosus or S. variolaris. Within the range of scales examined, we found robust congruence in spatial structure in abundance at the lower, but not the larger, range of scales for all four species. The relationship between abundance and upstream habitat availability in two species suggests that larval supply from upstream populations was probably the mechanism linking habitat size and abundance.

Abstract The Environmental Sensitivity Index (ESI) for oil spills was developed to assist coordinators to evaluate oil spill impact along shorelines and also to coordinate the allocation of resources during and after the incident, aiming to reduce environmental damage and consequences. Recently, Remotely Piloted Aerial Systems (RPAS) are being used in a wide range of areas, since they complement traditional remote sensing data (e.g., satellite images) and offer a rapidly, precise, detail and high-resolution images that fit well for environmental studies. Herein, the use of high-resolution RPAS images for ESI analysis of rocky shores in the Brazilian territory was performed. Using RPAS images, with their higher-resolution compared with ArcGIS Pro Basemap satellite images, increased the detailed of ESI analysis for oil spills, increasing the number of regions in the rocky shore that are more sensitive to oil spills. The RPAS images were able to decrease the number of areas that were less sensitive to oil spills, and increase areas that are more sensitive to oil spills. This increase is important, since they were not detected in the ESI analysis using conventional ArcGIS Pro Basemap satellite images. The RPAS images permit to delineate precisely rocky shores, improving ESI interpretation in rocky shores.

Bouet, A.; Collin, A.; James, D.; Rintz, C-L.; Dusseau, P.; Lesacher, M., and Feunteun, E., 2024. On the synergy of the UAV spatial modelling and citizen science for tidal coasts: The case of canopy-forming macroalgae and gastropods on the Emerald Coast, Brittany, France. In: Phillips, M.R.; Al-Naemi, S., and Duarte, C.M. (eds.), Coastlines under Global Change: Proceedings from the International Coastal Symposium (ICS) 2024 (Doha, Qatar). Journal of Coastal Research, Special Issue No. 113, pp. 154-158. Charlotte (North Carolina), ISSN 0749-0208. Coastal marine ecosystems provide crucial services to cope with accelerating global changes. Among them, intertidal rocky shores and their canopy-forming macroalgal habitats support a high biodiversity, provide food, offer coastal protection, and multiple cultural services. Due to their location, at the land-sea interface, these coastal areas are threatened by various distal and local anthropogenic pressures. Their monitoring at very high (dm) spatial resolution is necessary to better inform their sustainable management. The very high temporal resolution of the unmanned airborne vehicle (UAV) imagery can be agile enough to monitor intertidal shores during the low tide's short window. Active or passive UAV imagery, coupled with machine learning, has the capabilities to map habitats, but requires ground-truth data, whose amount is strongly constrained by the low tide period. The study proposes to combine quantitative information, collected by trained citizens, with UAV data. UAV-based data were collected using two different sensors: a topographic Light Detection and Ranging (LiDAR) system DJI L1 and a multispectral imager MicaSense Altum-PT. Linear regressions of the canopy-forming macroalgae cover and the abundance of the gastropod, Steromphala umbilicalis, were run based on UAV by-products. Multispectral orthomosaics better predicted the algae cover (R2 = 0.52) and the abundance of gastropod (R2 = 0.45) than lasergrammetric data (algae cover: R2 = 0.48; gastropod abundance: R2 = 0.42). A combination of both source of data revealed better prediction for the algae cover (R2 = 0.68), as well as for the gastropod abundance (R2 = 0.55). Results are discussed in the light of the cm-scale remote sensing but also in its aspect of environmental awareness and responsive action. [ABSTRACT FROM AUTHOR]

Intertidal macroalgal habitats are major components of temperate coastal ecosystems. Their distribution was studied using field sampling and hyperspectral remote mapping on a rocky shore of Porspoder (western Brittany, France). Covers of both dominating macroalgae and the sessile fauna were characterized in situ at low tide in 24 sampling spots, according to four bathymetric levels. A zone of ca. 17,000 m2 was characterized using a drone equipped with a hyperspectral camera. Macroalgae were identified by image processing using two classification methods to assess the representativeness of spectral classes. Finally, a comparison of the remote imaging data to the field sampling data was conducted. Seven seaweed classes were distinguished by hyperspectral pictures, including five different species of Fucales. The maximum likelihood (MLC) and spectral angle mapper (SAM) were both trained using image-derived spectra. MLC was more accurate to classify the main dominating species (Overall Accuracy (OA) 95.1%) than SAM (OA 87.9%) at a site scale. However, at sampling points scale, the results depend on the bathymetric level. This study evidenced the efficiency and accuracy of hyperspectral remote sensing to evaluate the distribution of dominating intertidal seaweed species and the potential for a combined field/remote approach to assess the ecological state of macroalgal communities. [ABSTRACT FROM AUTHOR]

The edible marine gastropod Trophon geversianus shows a large geographic distribution along the southern tip of South America, inhabiting both rocky intertidal and shallow subtidal zones, with distinct behavioural responses to environmental stressful conditions (desiccation, temperature amplitude and high irradiation). Nevertheless, its reproductive biology has been poorly reported to date. We studied the gametogenic cycle of an intertidal rocky shore population from northern Patagonia (Argentina), in order to investigate the relation between gonadal changes and seasonal environmental variables. Mature individuals were taken monthly during an annual reproductive season and processed by standard histology procedures (haematoxylin and eosin). Adults of T. geversianus registered different gonadal maturation stages along the year, showing a marked seasonal variation without a resting period. The highest gamete evacuation season in both sexes was registered when the environmental stress was minimum (winter), while a greater number of individuals with gonads in proliferation and growth were predominant during maximum environmental stress (summer). The reproduction pattern presented an extended period of evacuation and a short phase of non-evacuation, associated to drastic seasonal environmental changes in the intertidal zone of Atlantic Patagonia. This information is useful to protect the resource and assure the sustainability of intertidal populations. [ABSTRACT FROM AUTHOR]

Light pollution is becoming prevalent among other coastal stressors, particularly along intertidal habitats, arguably the most exposed to anthropogenic light sources. As the number of light pollution studies on sandy beaches, rocky shores and other intertidal habitats raises, commonalities, research gaps and venues can be identified. Hence, the influence of light pollution on the behavior and ecology of a variety of intertidal macro-invertebrates and vertebrates are outlined by examining 54 published studies. To date, a large majority of the reported effects of light pollution are negative, as expected from the analysis of many species with circadian rhythms or nocturnal habits, although the severity of those effects ranges widely. Experimental approaches are well represented throughout but methodological limitations in measurement units and standardization continue to limit the proposal of general conclusions across species and habitats. In addition, studies targeting community variables and the explicit influence of skyglow are heavily underrepresented. Likewise, studies addressing the interaction between light pollution and other natural and anthropogenic stressors are critically needed and represent a key venue of research. The nature of those interactions (synergistic, additive, antagonistic) will likely dictate the impact and management of light pollution in the decades ahead.

Global warming has been causing severe impacts on marine ecosystems, a notorious one being shifts in the geographical ranges of species. The north-western coast of the Iberian Peninsula is an especially interesting zone to study distributional shifts as it has a strong latitudinal thermal gradient, is influenced by the Canary upwelling system (which partially cancels coastal warming) and holds some of the most diverse macroalgae communities in Europe. Notably, it is within this region that many cold-water species, common in northern Europe, have their southernmost distribution refuge. Recent studies hypothesize that the environmental conditions may be nonetheless changing and already threatening this biodiversity hotspot. The main goal of this study was to carry out a fine-scale assessment of the distributional limits of several macroalgae in North-western Iberia, as well as identify possible population and range shifts using historical data (2001-2005) as reference. In addition, non-indigenous species were also surveyed. We also assessed if the regions of (i) Galicia, (ii) Northern Portugal, and (iii) Central Portugal displayed distinctive characters regarding macroalgae composition and abundance. We identified an increase in abundance of some non-indigenous macroalgae as well as a decrease in the abundance of some cold-water species. In the most severe cases, cold-water species were extirpated along hundreds of km. The compounded effect of the decrease in the abundance of cold-water species and the increase in the abundance of non-indigenous species is leading to the homogenization of macroalgae communities in north-western Iberia.

Data about meiobenthic ostracodes species on the different substrates of Zmiiniy Island nearshore water area are presented. The density and biomass means of the ostracodes were higher on the algal substrates (on Laurencia paniculata made up 41931 ± 12689 ind.·m-2 and 400.56 ± 125.65 mg·m-2 respectively). In the current study for the first time 13 ostracodes species were found, most of which are common in all types of substrate. The dominant species were Loxoconcha pontica Klie, 1937, Paradoxostoma intermedium Müller, 1894, Xestoleberis cornelii Caraion, 1963 and Xestoleberis decipiens (Müller, 1894). All of them are common species in the north-western Black Sea. Non-metric multidimensional scaling (nMDS) analysis of ostracodes species abundance shown that the samples of sandy-shells bottom differed significantly from algal and mussel substrates. According to the cluster analysis sand-shells bottom samples on almost 80 % differed from hard substrates. [ABSTRACT FROM AUTHOR]

Background Climate change has been increasing at an unprecedented rate in the last decades. Global warming has been causing a variety of impacts in marine ecosystems, including shifts in the geographical ranges of species. The north-western Iberian Peninsula coast is particularly interesting to study distribution shifts as it features a strong latitude thermal gradient, establishing a biogeographical transitional region where several cold- and warmadapted species have their equatorward or poleward distributions. In the early 2000s, it appeared that, while warm-water species were already responding to warming, cold-water species did not display a coherent response. It is now necessary to gather up-to-date data on the distribution of the same group of species to understand if current patterns of change confirm or deny those observed back then, which may give us important clues about the mechanisms setting species limits in the area. New information This study provides a fine-scale description of the occurrence of intertidal macroalgae species in the rocky shores of the north-western Iberian coast. Specifically, the spatial distribution and semi-quantitative abundance of 34 native and invasive species were assessed at 70 wave-exposed locations. This included 19 species of cold-water affinity, 10 species of warm-water affinity and five neutral species. When contrasted with historical observations, these new data can be used to quantify and map biodiversity change in the region, as well as help understanding the mechanisms constraining species distributions. [ABSTRACT FROM AUTHOR]

The seaweed Caulerpa cylindracea Sonder is one of the most important invaders on Mediterranean rocky shores. However, many driving pressures affecting its spread are poorly understood and seem to involve the interactions between abiotic and biotic factors. We studied the invasiveness of C. Cylindracea on two shallow vermetid platforms with a con­trasting ecological status on which C. Cylindracea was first detected simultaneously 15 years ago. The cover values of C. Cylindracea and the other macroalgal species were assessed for one year, embracing the whole platform width. Caulerpa cylindracea cover was higher on the platform that had a low ecological status, especially during warmer months at the outer seaward margin. The ecological status of the overstory of native species seems to be a key point conditioning the success of C. Cylindracea invasiveness on these platforms.

Data about meiobenthic ostracodes species on the different substrates of Zmiiniy Island nearshore water area are presented. The density and biomass means of the ostracodes were higher on the algal substrates (on Laurencia paniculata made up 41931 ± 12689 ind.·m-2 and 400.56 ± 125.65 mg·m-2 respectively). In the current study for the first time 13 ostracodes species were found, most of which are common in all types of substrate. The dominant species were Loxoconcha pontica Klie, 1937, Paradoxostoma intermedium Müller, 1894, Xestoleberis cornelii Caraion, 1963 and Xestoleberis decipiens (Müller, 1894). All of them are common species in the north-western Black Sea. Non-metric multidimensional scaling (nMDS) analysis of ostracodes species abundance shown that the samples of sandy-shells bottom differed significantly from algal and mussel substrates. According to the cluster analysis sand-shells bottom samples on almost 80 % differed from hard substrates.

Kelps dominate rocky shores in temperate latitudes, acting as important foundation species. Recently, kelp forests have received growing attention for their decline around the world. Climate change is one of the main drivers of their deforestation, both through abiotic stress and/or distortion of biotic interactions. In NW Spain, golden kelp (Laminaria ochroleuca) forests have recently declined in some areas due to excessive grazing. To further investigate the mechanisms behind this decline, a thorough 1-year seasonal demographic study was carried out on eight golden kelp reefs: four healthy and four degraded by herbivory. Kelps covered the full range of size classes throughout the year on healthy reefs. By contrast, only small, newly recruited kelps were found on degraded reefs in spring-summer, because excessive herbivory in autumn-winter caused a total collapse of kelp populations on a reef-scale (i.e., all kelps reduced to inviable stubs with no blade and no growth meristem). Bite marks in kelps covering all size classes showed that fishes, instead of invertebrates, were the culprits of the excessive herbivory. Recent studies, mostly conducted in the Indo-Pacific, also found that fish herbivory, alone or in combination with abiotic stressors, can maintain a canopy-free state in kelp reefs. To the best of our knowledge, this is the first time that fish is also shown to cause the collapse of entire kelp forests on a reef scale in the temperate Atlantic. The implications of this finding for the management and potential recovery of degraded reefs are discussed.

Environments with strong gradients in physical conditions, such as rocky intertidal, induce animal morphological strategies to face them. The gastropod Trophon geversianus inhabit within the intertidal and subtidal habitats of Patagonian rocky shores. Although there is a wide knowledge of the phenotypic differences of this species regarding habitats (i.e., intertidal/subtidal), little is known about the interaction between habitat and latitude. Here, we studied form variation (size and shape) by using 3D geometric morphometric of T. geversianus shells from alive gastropods and analyzed the phenotypic effect from micro-scale (habitat), macro-scale (latitude), and the interaction habitat-latitude (site). Lastly, we tested the classification accuracy of the shape variable for each predictor variable and a synthetic variable (from a cluster analysis). We found that habitats and sites had the greatest influence on shape variation. Moreover, we found that the largest shell sizes were more likely to be located in subtidal habitats. Also, the size differences between sites were not negligible. Finally, habitat demonstrated the highest classification accuracy for shape, even higher than genetically determined (sex) and synthetic variables. We found that the gastropods from the intertidal habitat presented a globular morph with shorter spire and larger relative size of the shell aperture, while subtidal gastropod showed an elongated morph, with smaller aperture and longer spire. We present evidence of the complexity of size and shape variation in T. geversianus, highlighting that site-dependence on shape variation must be considered in geometric morphometrics studies at a latitudinal scale. [ABSTRACT FROM AUTHOR]

Mollusks are a very important component of the invertebrate faunal biodiversity in marine ecosystems. However, knowledge on this (and other groups) is still incomplete. Inventories of fauna are very important tools to learn the biodiversity associated with specific regions and of specific zoological groups. In this paper, I report 103 species of heterobranch mollusks occurring along the Pacific coast of Colombia, including previous peer-reviewed records and new information. Of these, 23 are new records for the Pacific coast of Colombia, and a total of 32 species are registered for the first time in at least one locality along this shore. The most species diverse family is Chromodorididae, followed by Ellobiidae. The most diverse locality is Gorgona Island, closely followed by Malpelo Island. There is still much to learn from this rather isolated region, the northern Pacific coast of the South American continent. [ABSTRACT FROM AUTHOR]

To enable the process of energy transition towards carbon neutrality, it is important to educate the community on the need for social, economic, environmental and institutional transformation, and to educate and inform citizens to participate proactively in this change. This study evaluated the effectiveness of participation by elementary school students in educational activities and citizen science actions in enhancing their scientific knowledge and skills related to Ocean Literacy in the context of climate change. The activities were directed to children (aged 9–11) and involved pre-service teachers, in-service teachers and researchers, in formal and non-formal contexts. A total of 329 elementary school students participated in interdisciplinary science activities, focusing on the cause & effect of climate change in the ocean. They learned to identify rocky shore marine species used to monitor climate change and acquired ICT skills by inserting species observations in a biodiversity mapping platform. Finally, students worked collaboratively to communicate to the community what they have learned through an exhibition at the Museum João de Deus. To assess the impact of the activities on acquisition of scientific knowledge and skills by the students, a mixed methodology was applied using pre and post-tests, analysis of the data inserted by students in the platform, and content analysis of the students’ work for the museum exhibition. The results of pre and post-tests revealed a significant increase in knowledge of the effects of climate change on the rocky shore species distribution, as well as of the importance of monitoring these species distribution. The data from the online biodiversity platform showed that 42% of the species identifications made by the students were correct. The ability of the students to communicate their learning to the wider community was evaluated by the scientific content, structure, presentation and creativity and of posters, models, videos and games produced. Most of students focused their communications and creations on the greenhouse effect, cause & effect of climate change in the ocean and biodiversity. This study reinforces the importance of addressing Ocean Literacy and climate change through formal and non-formal educational activities with an investigative nature.

Populations within the same species range edge may experience contrasting local conditions and exhibit diverse levels of environmental tolerance. This heterogeneity within a range boundary has seldom been considered in studies forecasting the impact of anthropogenic habitat alteration and climate change on species distributions. Moreover, any ecological prediction under changing environmental conditions requires a good understanding of the combined responses of organisms to multiple stressors, in particular the effects on key life cycle stages of species. The intertidal seaweed Fucus serratus is a dominant species on northern Atlantic shores and whose southern limit is in the NW Iberian Peninsula. We examined how early developmental stages of southern-edge populations of this foundation alga responded to the combined effects of environmental stressors, including salinity and aerial and seawater temperature. Four populations from two different areas of the NW Iberian coast were considered: two populations from open shores on the northern coast and two populations from the western rias on the Atlantic coast. The study findings revealed inter-population variability in the response to heat stress, with greater survival of germlings from the northern populations than those from western rias. Environmental conditions are still more benign within western rias, under the influence of strong summer upwelling events. The results also suggest the key role of aerial thermal stress in determining the southern limit of distribution of the target species. The future of these heterogeneous edge populations from NW Iberian Peninsula depends on trends in climate change and the ability of populations to cope with these. Environmental changes may already be occurring at rates that exceed the plastic and adaptive potential of edge populations in N Spain, while the future of western rias as climate refugia for this and other foundation alga is also uncertain. [ABSTRACT FROM AUTHOR]

Background: The unprecedented rates of current biodiversity loss have motivated a renewed interest in environmental and biodiversity monitoring. The need for sustained monitoring strategies has prompted not only the establisment of new long-term monitoring programmes, but also the rescue of data from historical or otherwise archived sources. Amongst the most valuable datasets are those containing information on intertidal systems, as they are particularly well suited for studying the biological effects of climate change. The Portuguese rocky coast is quite interesting for studying the effects of climate change on the distribution of species due to its geographical orientation, latitudinal patterns in temperature, species richness, species' distribution patterns and availability of historical information. This work aims at providing a comprehensive picture of the distribution and abundance of intertidal macro-invertebrates and macro-algae along the Portuguese rocky coast in the early 2000s. New information: This study provides a description of the rocky shore intertidal biodiversity of the mainland Portuguese coast in the early 2000s. The spatial distribution and semi-quantitative abundance of a total of 238 taxa were assessed at 49 wave-exposed locations. These data provide a comprehensive baseline against which biodiversity changes can be effectively and objectively evaluated. [ABSTRACT FROM AUTHOR]

We hypothesized congruence in the spatial structure of abundance data sampled across multiple scales for an ecological guild of consumers that exploit similar nutritional and habitat resources. We tested this hypothesis on the spatial organization of abundance of an herbivorous guild of sea urchins. We also examined whether the amount of local along‐shore rocky habitat can explain the observed spatial patterns of abundance. Standardized estimates of abundance of four intertidal sea urchins—Diadema cf. savignyi, Echinometra mathaei, Parechinus angulosus, and Stomopneustes variolaris—were determined by six observers at 105 sites across 2,850 km of coast of South Africa. For each species and observer, wavelet analysis was used on abundance estimates, after controlling for potential biases, to examine their spatial structure. The relationship between local sea urchin abundance and the amount of upstream and downstream rocky habitat, as defined by the prevailing ocean current, was also investigated. All species exhibited robust structure at scales of 75–220 km, despite variability among observers. Less robust structure in the abundances of three species was detected at larger scales of 430–898 km. Abundance estimates of sympatric populations of two species (D. cf. savignyi and E. mathaei) were positively correlated with the amount of rocky habitat upstream of the site, suggesting that upstream populations act as larval sources across a wide range of scales. No relationship between abundance and habitat size was found for P. angulosus or S. variolaris. Within the range of scales examined, we found robust congruence in spatial structure in abundance at the lower, but not the larger, range of scales for all four species. The relationship between abundance and upstream habitat availability in two species suggests that larval supply from upstream populations was probably the mechanism linking habitat size and abundance. [ABSTRACT FROM AUTHOR]

Abstract This study examines the distribution of primary and secondary space holders integrated in morphological and feeder functional groups as well as the species richness over the seasons on northern Patagonian rocky shores. We also evaluated whether the temporal changes in species richness, assemblage structure and species turnover were related to seasonal changes. These patterns were studied by non-destructive samplings between December 2013 and March 2015. Thirty taxa were identified, including six algal morphological functional and three invertebrate feeder groups. The cover of seaweeds and invertebrates was positively correlated with changes in the environmental factors. The marked seasonality in this Patagonian zone changed between two contrasting periods. Species richness and assemblage structure were associated with seasonal changes and were influenced by the more abundant morphological and feeder functional groups. We suggest that habitat-formers, such as articulated calcareous and suspensor feeder groups, can expand and retract over time-scales of months to seasons, generating available space for the colonization and growth of other organisms. We conclude that seasonal changes and the dynamics of articulated calcareous and suspensor feeder groups drive changes in the algal and invertebrate abundances, in turn driving changes in species richness and assemblage structure.

Identifying susceptible regions where biodiversity changes occur at fast rates is essential in order to protect and ameliorate affected areas. Large-scale coastal monitoring programs that focus on long-term variability are scarce, yet the Marine Biodiversity Observation Network Pole to Pole is currently developing a regional collaboration throughout the American continent collecting biodiversity data in coastal habitats with a standardized systematic protocol. The use of photographic methods to collect assemblage data on intertidal rocky shores can be appropriate. The goal of this study was to analyze the performance of a simple, low-cost, non-destructive and low-tech photographic method on a broad geographical scale (∼ 2,000 km) of Atlantic Patagonian coastline. Concurrently, we aimed to identify indicators whose cover, presence or condition can be followed in time and used as beacons of change in biodiversity on these rocky intertidal shores. We also explored the potential relationships between assemblage structure and environmental variables, such as seascape classes. We identified and propose cover of mytilids, Corallina spp. and bare substrate as indicators of change due to their ecological relevance in intertidal assemblages and their visible and rapid response to human stressors or changes in environmental conditions. Finally, we illustrate the practicality and usefulness of remotely accessible environmental data, for instance the seascape classes approach as an integrative tool for large-scale rocky shore studies.

Rocky shore ecology has been studied for a long time, starting with qualitative descriptions and becoming more quantitative and experimental over time. Some of the earliest manipulative experimental ecological studies were undertaken on rocky shores. Many, over time, have made considerable contributions to ecological theory, especially highlighting the importance of biological interactions at the community level. The suitability of rocky shores as convenient test systems for ecological experimentation is outlined. Here we consider contributions from rocky shores to the emerging concepts of supply-side ecology, the roles of competition, predation and grazing, disturbance and succession and positive interactions in structuring communities along environmental gradients. We then address alternative stable states, relationships between biodiversity and ecosystem functioning, and bottom-up and top-down control of ecosystems. We briefly consider the feedback and synergies between ecological concepts and experimental work on rocky shores, whilst still emphasizing the traditional values of marine natural history upheld in JMBA since its first publication. The importance of rigorous experimental designs championed by Underwood and co-workers is emphasized. Recent progress taking advantage of new technologies and emerging approaches is considered. We illustrate how experimental studies have shown the importance of biological interactions in modulating species and assemblage-level responses to climate change and informed conservation and management of coastal ecosystems. [ABSTRACT FROM AUTHOR]

Ocean organisms as diverse as seaweeds and sea cucumbers exhibit life cycles in which dispersal occurs primarily via microscopic larvae or spores, with adults exhibiting limited or even no dispersal. In benthic animals, the larval stage concludes with irreversible settlement into the benthos. The decision of where and when to settle is thus one of substantial import. Prior work has shown that settlement in two shoreline echinoids (a sea urchin and a sand dollar) is unexpectedly sensitive to an environmental feature (intense fluid turbulence) that can be considered as a signal to larvae of their arrival in the neighbourhood of the hydrodynamically energetic habitats in which these taxa live as adults. Here, we used a comparative approach to explore the evolution of turbulence responsiveness in late-stage echinoid larvae. We examined three pairs of closely related sea urchins that differ in the energetic exposure of their adult habitats and found that larval responsiveness to turbulence was more pronounced in urchins that settle in more hydrodynamically exposed locations. These results raise the possibility that evolutionary differences in larval responsiveness to environmental indicators of appropriate adult habitat might reinforce or even provide a mechanism for vicariance in the ocean. [ABSTRACT FROM AUTHOR]

Marine hardground bottom (subtidal) benthic (sessile) communities (HBBC) are subjected to various biotic, abiotic, and anthropogenic factors that can vary over space and time and interact with one another. To evaluate the main drivers of the structure of HBBC in a large tropical bay in the southwest Atlantic (Ilha Grande Bay, Brazil), a total of 98 HBBC were sampled using visually estimated quadrats. Ten variables (depth, grazing intensity, irradiance, temperature, salinity, dissolved oxygen, nutrients (nitrite, nitrate, and phosphate), and chlorophyll a concentrations) were also measured. A total of 74 main space‐occupying taxon/functional groups were recorded which fell into six major HBBC groups. These were organized by depth/irradiance and grazing intensities which explained part of the HBBC variation: (a) Communities dominated by zoantharians occurred in the shallow, highest irradiance sites; (b) foliose and erect algae were inversely related to depth and grazing intensity; (c) crustose coralline algae dominated at greater depths and/or under higher grazing intensity; (d) zooxanthellate corals were associated with shallower and heterotrophic invertebrates with deeper stations; (e) photosynthetically efficient algae were associated with deeper stations, with more encrusting forms under higher grazing intensities; and (f) multi‐species turf‐forming algae were ubiquitous (did not present association with any of the measured variables). As communities' components and main structuring factors were similar to those found in coral reefs, these communities represent compatible receptor habitats for poleward escape, migration, and range extension under the present global warming scenario. [ABSTRACT FROM AUTHOR]

Siphonariids are pulmonate gastropods inhabiting rocky intertidal habitats, and many studies have focused on these false limpets around the world. In the southern South Atlantic, studies on reproduction and development in species of Siphonaria are scarce. We studied the embryonic development and egg masses of Siphonaria lateralis at its northernmost distribution in Atlantic Patagonia. In S. lateralis, as in most species of Siphonaria, individuals spawn benthic egg masses that strongly attach to intertidal rocky substrata. A single spherical egg that measures ~120 µm develops inside the egg capsule of S. lateralis. Considering the relatively small egg size, and reports from previous studies, the developmental modality of S. lateralis might be expected to include a planktotrophic larval phase. However, we found that hatchlings emerged as 1‐mm crawling juveniles, probably owing to the presence of intracapsular fluid, which may provide the energetic requirements for direct development. The embryonic size changed little from the egg to veliger stages, and then increased rapidly until the hatchling stage. We compared development in S. lateralis with development in the sympatric Siphonaria lessonii, in which egg size was reported to be ~80 µm and hatching occurs as planktotrophic veliger larvae. In these two species, spawn and early intracapsular developmental modes are remarkably different; these differences represent contrasting ways to survive in the harsh and physically stressful intertidal Patagonian coasts. [ABSTRACT FROM AUTHOR]

It is commonly assumed that the pelagic cyprid larvae of acorn barnacles must permanently attach to a substrate before metamorphosing to the benthic juvenile stage. We show that this is not always the case and demonstrate that some cyprids can metamorphose in the water column, i.e. without first becoming cemented to a surface. We observed early-metamorphosing cyprids to fully developed juveniles in coastal plankton samples during the 2018 recruitment season of Semibalanus balanoides (Linnaeus, 1767) in Atlantic Canada. We demonstrated through a laboratory experiment that cyprids can be induced to fully metamorphose into pelagic juveniles. These novel findings raise the question of whether this phenomenon may also occur in other barnacle species. [ABSTRACT FROM AUTHOR]

Marine protected areas (MPAs) can be an effective tool for the conservation and management of marine coastal habitats. MPAs have been shown to halt habitat degradation, enhance the biomass of exploited species and diversity in general. Yet, we still know little about its role in halting the spread of non-native species. In this study, we assessed the role of MPAs in the structure of shallow subtidal communities around São Miguel Island, in general, and particularly on distribution of the two species of genus Asparagopsis: A. armata and A. taxiformis. In the Azores, the former is a well-established invasive species, whereas the status of A. taxiformis is still questionable. Overall, there was a significant greater diversity in terms of both species richness and number of macroalgal functional groups within MPAs. However, when considering the relative abundance of the various macroalgal functional groups, or the assemblage as a whole (multivariate analysis), there was no significant difference between areas within and outside MPAs. The cover of A. taxiformis was significantly greater within MPAs but not its biomass, whereas no significant variation was observed for A. armata. Overall, results suggest that surveyed MPAs had a positive effect on the diversity of shallow-water macroalgal communities. However, they have a limited role on the distribution of both Asparagopsis spp. and negligible effects when considering the relative abundances of macroalgal functional groups. [ABSTRACT FROM AUTHOR]

Predation is one of the main structuring forces in rocky intertidal communities, though with an effect depending on the environmental context and conditions. On the stressful Patagonia shores of Argentina, experimental studies concluded that predation does not play a significant ecological role. In the biogeographic transition zone of northern Patagonia, where medium-sized predators (like octopuses and sea stars) coexist and are relatively abundant, the effect of predators in the rocky intertidal zone was never tested. The present study evaluated the effect of two intertidal predators, the small octopus Octopus tehuelchus (d'Orbigny, 1834) and the sea star Anasterias antarctica (Lütken, 1857), on the abundance of prey and the interaction strength of these predators on different functional groups in a mid-intertidal rocky community of northern Patagonia. To do so, we conducted a short-term-exclusion experiment in the mid-intertidal area and estimated the interaction strength through dynamic indices. Our experimental exclusion of octopuses and sea stars had no positive effect on the abundance of prey in a short-term period, adding evidence that predation remains weak even in north Patagonia (i.e., under ameliorated physical stress), even with a relatively high abundance of predators. The combined interaction strength of those consumers on prey in the different functional groups was weak, with the dynamic indices being positive for mobile grazers and scavengers and negative for sessile filter feeders. These results emphasize the significance and deepen the understanding of the role of consumers, food web linkages, and community function in the biogeographic transition zone of north Patagonia. [ABSTRACT FROM AUTHOR]

Artificial light at night (ALAN) is becoming a widespread stressor in coastal ecosystems, affecting species that rely on natural day/night cycles. Yet, studies examining ALAN effects remain limited, particularly in the case of sessile species. This study assessed the effects of ALAN upon the feeding activity and two molecular indicators in the widespread plumose sea anemone Metridium senile. Anemones were exposed to either natural day/night or ALAN conditions to monitor feeding activity, and tissue samples were collected to quantify proteins and superoxide dismutase (SOD) enzyme concentrations. In day/night conditions, sea anemones showed a circadian rhythm of activity in which feeding occurs primarily at night. This rhythm was altered by ALAN, which turned it into a reduced and more uniform pattern of feeding. Consistently, proteins and SOD concentrations were significantly lower in anemones exposed to ALAN, suggesting that ALAN can be harmful to sea anemones and potentially other marine sessile species. • We assessed artificial light at night (ALAN) effects on a sea anemone. • ALAN altered the strength and rhythm of the anemone feeding activity. • The stress associated with ALAN also reduced proteins and an enzyme. • ALAN expansion threatens the fitness of this and other sessile species. [ABSTRACT FROM AUTHOR]

Nowadays, coastal urbanization is one of the most serious and prevalent pressures on marine ecosystems, impacting their biodiversity. The objective of this study was to explore differences in attributes and biodiversity associated with an intertidal ecosystem engineer, the mussel Mytilus galloprovincialis Lamarck, 1819 between urban and non-urban shores. For this, mussel attributes and their associated macrofauna were compared between urban and non-urban rocky shores in the north of Portugal. Results showed that the largest sized mussels were more frequent on urban shores, whereas the smallest size class was only present in non-urban shores. Regarding macrofauna associated with mussels, the number of taxa was significantly higher on non-urban shores. Moreover, the structure of the macrobenhic assemblages was significantly different between urban and non-urban shores. Most important taxa responsible for differences were more abundant on non-urban shores except for Nucella lapillus, Idotea pelagica and Oligochaeta that were more abundant on urban shores. Therefore, our results showed that the mussel size frequency and the structure of the associated macrobenthic assemblages changed in urban shores. Considering the relevance of mussel beds for biodiversity and human well-being, our results indicate the need of adopting proper management plans to minimize these effects on urban intertidal ecosystems.