Intertidal Habitats Research Articles

Relating absolute abundance of an estuarine fish to habitat area in an urbanizing environment

Organisms that rely on salt marsh habitat are an important trophic link, helping to maintain estuarine ecosystem productivity. We used GIS to quantify intertidal (assumed salt marsh) area from aerial photographs taken in 1939 and from software-supplied satellite imagery taken in 2021 for tidal creeks in North Carolina (USA) that have experienced minor (<20%), moderate (20-60%), or substantial (>60%) losses of intertidal habitat over the 8 decades. The current (2022) absolute abundance of adult Fundulus heteroclitus, a trophically important resident fish in US Atlantic estuaries, was estimated over each season in each creek by fitting a Lincoln-Petersen model to tag-recapture data. Current abundances of F. heteroclitus were lowest in creeks with the lowest intertidal area. The median and 2.5/97.5 credible intervals of the posterior probability distribution for the slope of a regression model relating current fish abundance to current intertidal area were positive, demonstrating that intertidal area was a meaningful covariate of abundance. Loss of intertidal area in the creeks between 1939 and 2021 ranged from 8 to 93%. The correlation between current intertidal area and historical loss of this habitat was negative and significant (Pearson r = -0.91, p = 0.012). Parameters from the regression relating current abundance to intertidal area were used to estimate historic F. heteroclitus abundances in each creek using GIS-derived estimates of historic intertidal area. Historic abundances were predicted to have been on average (across study creeks) 7.5 times greater in 1939 than in 2022. Reduced abundances, and thus reduced trophic relay by F. heteroclitus to higher-order consumers, can be expected in estuaries that have lost salt marsh due to inter-decadal development.

Sea anemone microhabitats enhance the diversity and biomass of mobile invertebrates on temperate rocky shores

Sea anemones of the genus Anthopleura are abundant in rocky intertidal communities of the eastern Pacific, but their role as habitat and facilitators of biodiversity in this system has been overlooked. We provide evidence for a previously undescribed mechanism of facilitation associated with these cnidarians on temperate rocky shores. Sea anemones in the genus Anthopleura slowly release stored water at low tide, which helps them maintain ideal temperature conditions via evaporative cooling. This behavior results in leakage of water to surrounding intertidal habitats, producing unique microhabitats in the upper intertidal zone. We hypothesized that mobile invertebrate communities would use this habitat during low tides to ameliorate abiotic stress. In an in situ experiment spanning 3 sites along the coast of California, USA, it was found that maximum temperatures and relative desiccation rates were lower in sea anemone-associated microhabitats as compared to adjacent rock habitats. Observational surveys revealed higher richness and biomass of mobile invertebrates in sea anemone microhabitats, and these differences were supported by manipulative experiments that included both adding and removing sea anemones. Our results support a novel community-wide facilitation driven by an adaptation of intertidal sea anemones. The effects of sea anemone microhabitat on upper shore biodiversity were associated with site and sea anemone species and may suggest a facilitative role of a temperate cnidarian-algal mutualism in mitigating stress and enhancing biodiversity.

Nekton use of co-occurring aquaculture and seagrass structure on tidal flats

On the extensive tidal flats of Willapa Bay (Pacific coast, USA), oyster culture, seagrass, and mudflats create a mosaic of intertidal habitats. Structured habitats are generally considered to increase abundance and diversity of associated species, but less attention has been paid to roles of different kinds of structure (seagrass meadows, reefs, farm infrastructure) or co-occurring structure in shaping nekton assemblage structure. Here, we investigated the effects of different oyster culture methods (suspended culture and bottom culture) on nekton communities and abundance across a gradient of seagrass habitats, during multiple seasons, and using both seine and video sampling methods. Of 23 major estuarine taxa, 2 were generally associated with vertical structure (eelgrass or suspended culture), 3 were seagrass specialists, and 3 primarily used habitats lacking vertical structure (mudflats and bottom culture). Where oyster culture was present, 5 taxa associated with on-bottom and 2 taxa associated with suspended culture. Assemblage structure responded to co-occurring structure as expected from responses to each structure type independently (i.e. additive effects of seagrass and oyster culture). In contrast to much empirical evidence in structured habitats, seagrass density was a poor predictor of overall fish abundance. These findings together suggest that maintaining a mosaic of available habitats is favorable for promoting diversity in Willapa Bay.

Impacts of an invasion by green crab Carcinus maenas on the intertidal food web of a Patagonian rocky shore, Argentina

The green crabCarcinus maenas(L., 1758) is a highly invasive species that has altered various coastal marine ecosystems worldwide. Green crabs were first found on the Argentinian Patagonian coast in 2001 and were detected in Golfo Nuevo (Chubut, Argentina) in 2015. In this study, we described a rocky intertidal food web in the Golfo Nuevo and evaluated the effect of green crab invasion on the network. We assembled the intertidal food web from a compilation of diet studies and compared 2 scenarios: pre-invasion (without green crab) and post-invasion (with green crab). We calculated several structural network metrics to compare the scenarios. The green crab was positioned as a top predator in the intertidal food web, consuming prey from different trophic levels and exhibiting the capacity to exert top-down control. Green crab presence altered the structure and stability of the food web. Additionally, we evaluated the effect of potential competitive interactions between native species and the green crab on the food web. Possible competitive interactions increased the effect the green crab had on the structure of the food web. Our results show that green crab invasion decreased food web stability by reducing the capacity of the food web to contain small- and long-range disturbances. These results contribute to the assessment and monitoring of the possible effects of other factors of global change. The system is less stable than before green crab invasion, and the drastic changes in community composition already recorded in rocky intertidal ecosystems in Patagonia are more likely to amplify through the food web.

Effect of increased inundation time on intertidal ecosystem functions of South West Atlantic soft-bottom environments

Soft-bottom intertidal systems are valuable due to the ecosystem services they provide. Although these systems are normally subjected to highly variable environmental conditions, disturbances have become more frequent due to increases in anthropogenic pressure. Sea level rise (SLR) may generate changes in the ecosystem functioning of intertidal systems and in the ecosystem services they provide. In the Argentinean coast (SW Atlantic), SLR analysis shows trends similar to the global ones. It is not known how disturbances may affect the activity of benthic communities and the associated ecosystem functions. Therefore, through a field experiment at the marsh-mudflat edge in northeastern Argentina, we evaluated the effect of increased inundation time on bioturbation intensity, detritus decomposition and microphytobenthic primary production. Sediment physicochemical parameters (pH, temperature, water content and organic matter) were also measured. The results showed that increased inundation time had no effect on microphytobenthic primary production or bioturbation intensity in summer. Nevertheless, inundation time increased the burrowing activity of the intertidal crabNeohelice granulatain winter and spring and greatly decreased the variability inSpartina densifloradecomposition and organic matter content. In the context of a changing world due to global climate change, reduced variability in ecosystem functioning could indicate a decline in ecosystem resilience. As a consequence, vital ecosystem functions could be altered or lost, thus impacting the ecosystem services they deliver.

Impacts of marine heatwaves on byssus production in highly invasive fouling mussels

Marine heatwaves (MHWs) are projected to increase in their frequency, intensity, and duration, causing irreversible and catastrophic consequences for intertidal ecosystems around the world. The highly invasive fouling mussel, Arcuatula senhousia, can cause marked habitat alteration by constructing extremely intense byssal mats, devastating the biodiversity of many intertidal systems, yet very little is known about its fate under conditions of more frequent, hotter and longer MHWs. Here, we assessed impacts of two scenarios of MHWs (low-intensity with 4 °C rise of seawater temperature and high-intensity with 8 °C rise, respectively) on the byssal production of A. senhousia. Mussels exposed to low-intensity MHWs did not show any significant differences in the number, length and diameter of byssal threads, compared with those not thermally stressed. Under high-intensity scenario, the byssus production was significantly depressed, and byssal threads became fewer, shorter and finer, in line with significant decreases in cumulative length and volume. These findings provide a better understanding of responses of invasive fouling mussels such as A. senhousia to MHWs and make a leap forward in linking climate change and biological fouling in marine ecosystems.

The Complex Interactions Between Sediment Geochemistry, Methylmercury Production, and Bioaccumulation in Intertidal Estuarine Ecosystems: A Focused Review.

Due to their natural geochemistry, intertidal estuarine ecosystems are vulnerable to bioaccumulation of methylmercury (MeHg), a neurotoxin that readily bioaccumulates in organisms. Determining MeHg concentrations in intertidal invertebrates at the base of the food web is crucial in determining MeHg exposure in higher trophic level organisms like fish and birds. The processes that govern the production of MeHg in coastal ecosystems are influenced by many geochemical factors including sulfur species, organic matter, and salinity. The interactions of these factors with mercury are complex, and a wide variety of results have been reported in the literature. This paper reviews conceptual models to better clarify the various geochemical and physical factors that impact MeHg production and bioavailability in intertidal ecosystems.

Diversity of Myxobacteria Isolated from Indonesian Mangroves and Their Potential for New Antimicrobial Sources

Mangroves are unique intertidal ecosystems that provide ecological niches to different microbes, which play various roles in nutrient recycling and diverse environmental activities. The association between myxobacteria and mangroves are hitherto poorly understood. The aim of our study was to evaluate the myxobacterial community composition as well as isolate myxobacteria and to characterize the antimicrobial activity of myxobacteria isolates from Indonesian mangroves. Twenty-five cultivable myxobacteria were affiliated in six genera: Myxococcus, Corallococcus, Archangium, Chondromyces, Racemicystis and Nannocystis of the order Myxococcales based on partial 16S rRNA gene sequences. Thirteen crude extracts showed moderate activities against at least one of human pathogenic microorganisms. The crude extract of Racemicystis sp. strain 503MSO indicated a novel compound, which has not been reported in the database yet and the identification of this compound needs further study. The myxobacterial communities of three different sampling sites were analyzed using primers adapted for the myxobacteria group identification. The results showed that myxobacterial communities are more diverse than assumed. Therefore, our study has highlighted the importance of the mangrove habitat as promising harbor of myxobacteria as well as novel antimicrobial compounds with activity against pathogenic microorganisms.

Structural Characterization and Spatial Mapping of Tetrodotoxins in Australian Polyclads.

Tetrodotoxin (TTX) is a potent marine neurotoxin that occurs in several Australian phyla, including pufferfish, toadfish, gobies, and the blue-ringed octopus. These animals are partially immune, and TTX is known to bioaccumulate and subject to trophic transfer. As such, it could be more ubiquitously distributed in animals than is currently known. Flatworms of the order Polycladida are commonly occurring invertebrates in intertidal ecosystems and are especially diverse in Australian waters. While TTX has been identified in polyclads from Japan and New Zealand, Australian species have yet to be tested. In this study, several eastern Australian polyclad flatworm species from the suborders Cotylea and Acotylea were tested for TTX and analogs by HILIC-HRMS to understand the distribution of this toxin within these suborders. Herein, we report the detection of TTX and some known analogs in polyclad species, one of which is a pest to shellfish aquaculture. We also report, for the first time, the application of MALDI mass spectrometry imaging utilized to map TTX spatially within the intestinal system of polyclads. The identification of TTX and its analogs in Australian flatworms illustrates a broader range of toxic flatworms and highlights that analogs are important to consider when studying the distributions of toxins in animals.

Long-term changes in ecosystem functioning of a coastal bay expected from a shifting balance between intertidal and subtidal habitats

Coastal areas are subjected to several anthropogenic stressors with much of the world's intertidal areas receding due to human activities, coastal erosion and sea level rise. The Dutch Eastern Scheldt (ES) has been predicted to lose around 35% of intertidal areas by 2060. This study investigates differences between biogeochemical fluxes of intertidal and subtidal sediments of the ES and assesses how ongoing erosion may modify the sedimentary ecosystem functioning of this coastal bay in the coming decades. Monthly fluxes and porewater concentrations of dissolved inorganic nitrogen (DIN), phosphorous (DIP), silica (DSi), carbon (DIC) and oxygen (O2) as well as organic matter (OM) characteristics were measured from intertidal and subtidal sediments from June 2016–December 2017. Compared to subtidal stations, OM was significantly more reactive in intertidal samples and exhibited 37% higher O2 fluxes, suggesting a strong influence from microphytobenthos. Subtidal sediments exhibited an average efflux of nitrates (0.28 mmol m−2 d−1) and phosphates (0.09 mmol m−2 d−1) into the water column, while intertidal areas displayed average influxes (nitrates = −1.2 mmol m−2 d−1, phosphates = −0.03 mmol m−2 d−1) directed into the sediment. The calculated removal of total DIN and DIP from the water column was 34–38% higher in intertidal compared to subtidal samples suggesting stronger denitrification and phosphorus adsorption to solid particles from intertidal sediments. As an upscaling exercise, we estimate potential erosion induced changes if the ES stations are representative for the system. With this assumption, we estimate 11% and 8% reductions for respective nitrogen and phosphorus removal in the entire ES by 2060. Given the global observations of eroding intertidal areas and rising sea levels, we suggest that the predicted habitat loss may cause significant changes for coastal biogeochemistry and should be investigated further to understand its potential consequences.

Modeling Holocene coastal ecosystem availability and site distribution patterns for Borikén, Puerto Rico

Coasts are dynamic environments prone to the physical and social impacts of climate change. Examining the archaeological and environmental records of coastal areas can deepen our understanding of how humans respond to changing environmental conditions. In this article we consider how sea-level rise impacted coastal environments through time, and how these changes could pose opportunities or challenges to local indigenous populations. We present new findings of coastal zone transformations and past settlement patterns for Borikén, the largest island of the Puerto Rican archipelago, during the Holocene. We use paleogeographic modeling to reconstruct ecosystem availability for six discernible coastlines at 1000-year resolutions that accounts for past relative sea-level (RSL) heights and paleotidal ranges. We then compared ecosystem availability trends with the spatiotemporal distributions of available archaeological data to demonstrate the localized impacts of climate-related RSL rise across the island’s coastal ecosystems and suggest a consideration of habitat availability in past decision-making strategies. We observe a strong presence of Archaic Period sites in the island’s southwest coast where high coastal ecosystem availability and stability were present during this period. We also observe a significant expansion of intertidal ecosystems beginning at 3 kya for the north-central, north-eastern, south-central, and south-eastern coastlines that correspond to the appearance of materials associated with Early and Late Ceramic Periods cultures in these areas. This comparison of differential coastal transformations and site distributions conveys a deeper understanding of factors involved in past decision-making strategies and contributes to the emerging picture of human adaptations amidst changing environmental conditions.

Efficient removal of Spartina alterniflora with low negative environmental impacts using imazapyr

Invasion by smooth cordgrass (Spartina alterniflora Loisel) has greatly impacted the intertidal ecosystems of China. Worldwide, chemical control is the most widely used method to control Spartina species, but it has not been widely implemented along the Chinese coast due to concerns about the potential impacts of herbicide residues on the environment and organisms. Macrobenthos, both natural and cultured on intertidal mudflats, is an important seafood resource, so human food safety is a particular concern. Here we tested the effectiveness of imazapyr (an imidazolinone herbicide inhibiting the synthesis of branched-chain amino acids) in controlling S. alterniflora from August 2020 to June 2021 on the Jiangsu Coast, an area severely impacted by S. alterniflora. We used two different concentrations of the herbicide and monitored the density of S. alterniflora seedlings and flower spikelets, the effects of herbicide use on macrobenthos, and residues in organisms and the environment at different times post-application. Ten months after application, imazapyr had killed all plants and within 30 days it inhibited the two reproductive processes of germination and flowering; there were no significant differences between the two concentrations used. Imazapyr residues were detected in the environment for up to 14 days post-application, but at very low concentrations and exponentially decreased with time. No residues were found in any macrobenthos. Imazapyr use did not result in a reduction of macrobenthos density. We conclude that the herbicide imazapyr effectively removes S. alterniflora with little collateral damage to other organisms and the environment. However, in view of the relatively small scale of our trials and the great extent of S. alterniflora in many sites in China, we recommend that larger scale field trails be conducted to assess any potential adverse effects when imazapyr is used at a landscape level.

Morphodynamic signatures derived from daily surface elevation dynamics can explain the morphodynamic development of tidal flats

Understanding the sensitivity of tidal flats to environmental changes is challenging. Currently, most studies rely on process-based models to systematically explain the morphodynamic evolution of tidal flats. In this study, we proposed an alternative empirical approach to explore tidal flat dynamics using statistical indices based on long-term time series of daily surface elevation development. Surface elevation dynamic (SED) indices focus on the magnitude and period of surface elevation changes, while morphodynamic signature (MDS) indices relate sediment dynamics to environmental drivers. The statistical analyses were applied to an intervention site in the Netherlands to determine the effect of recently constructed groynes on the tidal flat. Using these analyses, we were able to (1) detect a reduction in the daily SED and (2) determine that the changes in the daily SED were predominantly caused by the reduction in wave impact between the groynes rather than the reduction in tidal currents. Overall, the presented results showed that the combination of novel statistical indices provides new insights into the trajectories of tidal flats, ecosystem functioning, and sensitivity to physical drivers (wind and tides). Finally, we suggested how the SED and MDS indices may help to explore the future trajectories and climate resilience of intertidal habitats.

Spatial and seasonal variation in macrozoobenthic density, biomass and community composition in a major tropical intertidal area, the Bijagós Archipelago, West-Africa.

The coastal intertidal ecosystem of the Bijagós Archipelago, Guinea-Bissau, one of the largest and most important in West Africa, sustains a considerable proportion of the migratory shorebird populations of the East Atlantic Flyway and operates as a nursery area for benthic fish in the region. The macrozoobenthos in these mudflats constitute the main food source for both groups so that spatial and temporal variation in their abundance and community composition is likely to influence the abundance and distribution of fish and birds. In this study we described the spatial and temporal dynamics in the density, biomass, and community composition of macrozoobenthos across six intertidal flats in three islands of the Bijagós Archipelago. Overall, the Bijagós Archipelago was characterised by a highly species-rich macrozoobenthic community, with ca. 88 taxa identified across all sites, reaching a mean density of 1871 ± 58.3 ind.m-2 (mean ± SE) and mean biomass of 5.65 ± 0.41 g of AFDM.m-2 (ash-free dry mass per m2), values much lower than what was described for nearby intertidal areas, namely the Band d'Arguin, Mauritania. Density and biomass of major macrozoobenthos classes (Bivalvia, Polychaeta, Malacostraca and Gastropoda) differed across sites and months, displaying an overall increase in density towards the final months of the dry season (March and April). Similarly, community composition also differed significantly between sites and throughout the season. The site with most distinct community composition (Adonga) supported low diversity and high abundance of a few bivalve species, whilst other two sites that hosted the most diverse communities, were also the most similar between them (Anrumai and Abu). These spatial and temporal patterns constitute an important baseline to improve knowledge of this intertidal ecosystem and will contribute towards a better understanding of the spatial and temporal distribution patterns of their consumers.

Mussels Fabricate Porous Glues via Multiphase Liquid-Liquid Phase Separation of Multiprotein Condensates.

Mussels (Mytilus edulis) adhere to hard surfaces in intertidal marine habitats with a porous underwater glue called the byssus plaque. The plaque is an established role model for bioinspired underwater glues and comprises at least six proteins, most of which are highly cationic and enriched in the post-translationally modified amino acid 3,4-dihydroxyphenylalanine (DOPA). While much is known about the chemistry of plaque adhesion, less is understood about the natural plaque formation process. Here, we investigated plaque structure and formation using 3D electron microscopic imaging, revealing that micro- and nanopores form spontaneously during secretion of protein-filled secretory vesicles. To better understand this process, we developed a method to purify intact secretory vesicles for in vitro assembly studies. We discovered that each vesicle contains a sulfate-associated fluid condensate consisting of ∼9 histidine- and/or DOPA-rich proteins, which are presumably the required ingredients for building a plaque. Rupturing vesicles under specific buffering conditions relevant for natural assembly led to controlled multiphase liquid-liquid phase separation (LLPS) of different proteins, resulting in formation of a continuous phase with coexisting droplets. Rapid coarsening of the droplet phase was arrested through pH-dependent cross-linking of the continuous phase, producing native-like solid porous "microplaques" with droplet proteins remaining as fluid condensates within the pores. Results indicate that histidine deprotonation and sulfates figure prominently in condensate cross-linking. Distilled concepts suggest that combining phase separation with tunable cross-linking kinetics could be effective for microfabricating hierarchically porous materials via self-assembly.

Coastal engineering infrastructure impacts Blue Carbon habitats distribution and ecosystem functions

Intertidal estuarine habitats (e.g., saltmarshes and tidal flats) provide important ecosystem services to society, including coastal protection, food provision and Corg sequestration. Yet, estuaries and estuarine habitats have been subjected to intense human pressure, such as land-use change and artificialization of the shoreline to support economic activities and uses. Construction of engineering infrastructures (e.g., piers, bridges) in these areas alters estuary-wide hydromorphological conditions and thus sedimentation patterns at the estuarine scale, which are key drivers of habitats distribution and ecosystem structure, processes and functions. Most of the research on the impact of civil engineering structures on coastal habitats has focused on the biological communities that colonize them or the bottoms where they are placed, whereas their indirect impacts on adjacent habitats has been largely unexplored. Understanding the influence of man-made infrastructures on the distribution of estuarine habitats and functions is critical, particularly considering that shoreline armoring is expected to increase as a way to protect coastal areas from hazards derived from climate change. Shifts in habitat distribution and functions occur in several years or decades and relating them with the occurrence of past historical events is challenging when no monitoring data is available. By examining historical aerial photographs and different biogeochemical properties along a saltmarsh soil record, this study demonstrates that the construction of an infrastructure (i.e. bridge) caused a rapid transformation (~ 30 years) of a bare sandflat into a high marsh community and to significant changes in sediment biogeochemical properties, including the decrease in sediment accretion rate and Corg burial rates since then. This study contributes to increase the knowledge on the impact that the construction in coastal areas of civil engineering infrastructures can cause in intertidal habitats distribution and the ecological functions they provide for climate change adaption and mitigation.

Diversity and Disturbance: How Mussels and Sea Stars Strengthen the Rocky Intertidal Community

In the rocky intertidal zone, tides and rocks set the stage. Together they create habitat for a diverse community of species adapted to a world both underwater (high tide) and exposed to air (low tide). In some protected areas, like national parks, we study rocky intertidal ecosystems as vital signs of nature’s health. Studying them helps us understand the impact of disturbances, which play an important role in shaping these communities. Some disturbances, like the tides, happen daily. Others, like diseases, might happen once every decade. This article is about how tides and diseases affect two important members of rocky intertidal communities—mussels and sea stars. We explain the roles these organisms play and what happened when ochre sea stars, an important species in these habitats, suffered a major disease outbreak. Last, we emphasize the importance of protecting these vital ecosystems so we can continue to learn about the health of the natural environment.

Mapping services for an ecosystem based management along the Andalusian coastal zone (Spain)

The coastal zone is an area where a multitude of physical-natural, social and economic issues converge. The interactions among these elements are accentuated by the demographic concentration that characterises coastal areas all over the world. Coastal areas have the unique characteristic of being located in the connecting space between land and marine areas. The economic activities that take place on the coast require the services provided by terrestrial, intertidal and marine ecosystems for their proper functioning. In consequence, the main objective of this research is to identify and map ecosystem services provided by coastal ecosystems in the region of Andalusia (Spain) in order to move towards an Ecosystem-Based Management of this area.Ecosystem services are obtained from a literature review supported by a participatory process through expert consultation. The results obtained from the participatory process, together with the analysis and mapping of the ecosystems, make it possible to obtain those areas where the diversity of potential ecosystem services is greatest. The results of the research highlight certain ecosystems, such as the intertidal ecosystems, which, although they occupy the smallest surface area, are the ones that offer the greatest services to the population. Therefore, studying ecosystem services in coastal areas in order to move towards an Ecosystem-Based Management must be done from a broad perspective, considering the coastal zone as a complete socio-ecological system.

Global distribution and diversity of marine euendolithic cyanobacteria.

Euendolithic, or true-boring, cyanobacteria actively erode carbonate-containing substrata in a wide range of environments and pose significant risks to calcareous marine fauna. Their boring activities cause structural damage and increase susceptibility to disease and are projected to only intensify with global climate change. Most research has, however, focused on tropical coral systems, and limited information exists on the global distribution, diversity, and substratum specificity of euendoliths. This metastudy aimed to collate existing 16S rRNA gene surveys along with novel data from the south coast of South Africa to investigate the global distribution and genetic diversity of endoliths to identify a "core endolithic cyanobacterial microbiome" and assess global diversification of euendolithic cyanobacteria. The cyanobacterial families Phormidesmiaceae, Nodosilineaceae, Nostocaceae, and Xenococcaceae were the most prevalent, found in >92% of categories surveyed. All four known euendolith clusters were detected in both intertidal and subtidal habitats, in the North Atlantic, Mediterranean, and South Pacific oceans, across temperate latitudes, and within rock, travertine tiles, coral, shell, and coralline algae substrata. Analysis of the genetic variation within clusters revealed many organisms to be unique to substratum type and location, suggesting high diversity and niche specificity. Euendoliths are known to have important effects on their hosts. This is particularly important when hosts are globally significant ecological engineers or habitat-forming species. The findings of this study indicate high ubiquity and diversity of euendolithic cyanobacteria, suggesting high adaptability, which may lead to increased community and ecosystem-level effects with changing climatic conditions favoring the biochemical mechanisms of cyanobacterial bioerosion.

Biogeography of algae and invertebrates from wave-exposed rocky intertidal habitats along the Atlantic coast of Nova Scotia (Canada): Latitudinal and interannual patterns and possible underlying drivers

Biogeographic studies aim to understand species distributions and are becoming increasingly relevant to establish baselines to monitor ecological change. The NW Atlantic coast hosts a cold-temperate biota, although knowledge about its biogeography is patchy. This study documents for the first time biogeographic variation at mid-to-high intertidal elevations in wave-exposed rocky intertidal habitats along the open Atlantic coast of Nova Scotia (Canada), a hydrographically distinct subregion of this cold-temperate region. For this goal, we measured the summer abundance of algae and invertebrates at the same nine locations over four consecutive years (2014 to 2017) spanning 415 km of coastline, which allowed us to examine latitudinal and interannual patterns. In addition, we looked for mensurative evidence on possible drivers underlying these patterns, focusing on sea surface temperature, daily maximum and minimum temperature (which often happen at low tides at thus differ from sea surface temperature), pelagic food supply for intertidal filter-feeders (phytoplankton abundance and particulate organic carbon), drift sea ice during the cold season (which can cause intertidal disturbance), and species associations. Our field surveys revealed that northern locations can be severely disturbed by ice scour when drift ice is abundant and, while biological recolonization occurs over the years, it differs in pace among locations. Southern locations, instead, did not experience ice scour during our study and, thus, generally exhibited a higher species richness and abundance than northern locations. Multivariate analyses indicated that the aforementioned expressions of temperature and pelagic food supply explained together 32–55% of the variation in alongshore biogeographic pattern, depending on the year. Species association analyses suggest that algal foundation species (generally more abundant at southern locations) contribute to increase location-wise species richness. Mensurative evidence for bottom-up forcing in seaweed–herbivore and filter-feeder–predator systems differed greatly among years. Overall, in addition to its inherent value to advance NW Atlantic intertidal biogeography, our species distribution database should be valuable to assess ecological change decades into the future as climate change and other anthropogenic influences unfold.