Intertidal Habitats Research Articles

Biogeographic Patterns in Density, Recruitment, Body Size and Zonation of Rocky Intertidal Predators Suggest Increased Population Vulnerability Near Southern Range Limits

ABSTRACTAimSurveying the demography of populations near species range edges may indicate their vulnerability to range contractions or local extinction as the climate changes. In the rocky intertidal, not only are latitudinal ranges constricted by thermal stress, but tides also create zonation or a ‘vertical range’ driven by sharp environmental gradients. By investigating demographics along the latitudinal and vertical ranges simultaneously, we can investigate whether populations may be vulnerable to a changing climate.LocationRocky intertidal habitats along west coast of the United States.TaxaOchre sea star Pisaster ochraceus, six‐armed sea star Leptasterias spp., emarginate whelks (Nucella ostrina and N. emarginata) and channeled whelk N. canaliculata.MethodsIn 2018, we surveyed the demographics of the taxa above at 33 sites spanning > 11° latitude from central Oregon to southern California, near the southern range limits of each taxon. We counted and sized individuals from the high to low intertidal zone. To understand how environmental stress changed with latitude, we evaluated intertidal temperatures in situ, as well as tidal extremes, tidal amplitude and wave exposure using offshore buoys.ResultsFor all taxa, population density, the relative proportion of smaller individuals (except for emarginate whelks) and the upper vertical limits on the shore declined from north to south as temperatures increased and high tide height, tidal amplitude and wave heights decreased. In addition, smaller individual Leptasterias spp. generally inhabited lower shore levels while smaller individual emarginate whelks inhabited higher shore levels coastwide. For N. canaliculata, smaller animals were higher on shore northward, but lower on shore southward.Main ConclusionsWhile this study is a snapshot in time and cannot assess impacts of climate change, our surveys suggest environmentally‐related demographic limitation toward southern range limits and demographically vulnerable southern populations. Therefore, a warming climate may cause local extinctions or range contractions near southern limits.

Social Perception and Engagement in Mangrove Restoration: A Case Study in Central America

Mangroves are vital intertidal ecosystems that support biodiversity and protect coastal communities, but face increasing pressure from anthropogenic activities that sustain local livelihoods. It is crucial to integrate the social dimension into conservation efforts by encouraging community participation in mangrove restoration. Chame Bay, located on the central Pacific coast of Panama, is a protected area with significant mangrove cover, but despite its management plan, degradation continues due to intensive timber extraction for charcoal production and insufficient natural regeneration. This study investigates local knowledge and perceptions of mangrove functions and regeneration. A proportional stratified sampling of the Chame Bay population was used, with 300 interviews conducted among key stakeholders, including residents and mangrove resource users. Variables such as age, education, and profession were analyzed in relation to perceptions, participation, and willingness to participate in restoration efforts. Results indicate that 24.67% of the population’s primary economic activity is charcoal production from mangrove wood, with 15% of producers already involved in restoration and 60% willing to participate. These findings highlight the potential for community-driven restoration and emphasize the need for environmental education to encourage participation. This study provides essential information for designing restoration strategies in mangrove areas in Central America.

Extremely Rare Finding of a Chiton (Mollusca, Polyplacophora) in a Rocky Intertidal Habitat in Nova Scotia (Canada)

Chitons are a group of mollusks (polyplacophores) that differ from the mollusks that are most often found on marine rocky shores (bivalves and gastropods). On the Atlantic coast of North America, chitons have been reported in subtidal habitats from Newfoundland (Canada) to New England (USA). Here, we report the finding of Boreochiton ruber in an intertidal habitat in Nova Scotia (Canada). After surveying various coastal locations across Nova Scotia for 20 years (2004 to 2024), this was the only intertidal chiton we ever found, making this an extremely rare occurrence. Rare species may contribute in unique ways to community functioning, making their reports valuable for biodiversity and ecosystem research.

Metabolic rates of different demographics in the sand fiddler crab Leptuca pugilator.

Studies on animal energetics often focus on standardized metabolic rates to facilitate comparison across systems. Yet these standardized measurements often do not capture the realistic demographic and environmental variation that is common in natural settings. Rather, individuals included in these studies are often non-reproducing, uninjured, resting adults that have not recently eaten-far from a representative sample. We measured the respiratory rates of the sand fiddler crab Leptuca pugilator in air immediately after capture in the field, and compared rates between males, females of different reproductive states, and juveniles. As expected, we show that metabolic rates were influenced by body mass and activity level. We also show that being vitellogenic or gravid had only minor impacts on metabolic costs of females. Importantly, we demonstrate how considering demographics allows for the detection of phenomena that would otherwise go unnoticed. We found that field metabolic rates of L. pugilator in air are as much as an order of magnitude higher than previous standard metabolic rates measured on post-prandial, quiescent individuals. These higher rates may reflect a combination of high activity and active digestion, as fiddler crabs actively feed during low tide periods. Our results highlight the importance of considering differences in sex, life history stage, and reproductive state of organisms in fluctuating environments, such as intertidal habitats, when assessing energy expenditure.

Current status of plastic waste distribution in the intertidal ecosystem and fishing port in Nha Trang marine protected area, Khanh Hoa province

Current status of plastic waste distribution in the intertidal ecosystem and fishing port in Nha Trang marine protected area, Khanh Hoa province

Tees Tidelands, UK – restore, reconnect, realign

The Tees estuary, in north-east England, is one of the most heavily modified and developed estuaries in the UK, with less than 10% of the original intertidal habitats remaining. The few remaining natural areas of the estuary are dominated by hard flood defences, industrial quaysides and tidal barriers. These features all prevent natural expansion of the estuary. Tees Tidelands is an estuary-wide programme to open up the tributaries to tidal influence, to enable fish passage, re-establish parts of the natural estuary and permit inland migration of the estuary. This will maintain and improve resilience to flood risk through nature-based solutions. The £30 million Environment Agency’s Tees Tidelands programme comprises ten projects and strives to: restore the natural habitat; reconnect people to the estuary, while being resilient to the impact of climate change; realign the estuary, allowing for coastal expansion. This article will set the tone for engineers to be focused on working with the environment, to create a better place.

Planktonic to sessile: drivers of spatial and temporal variability across barnacle life stages and indirect effects of the Pacific Marine Heatwave

ABSTRACT Barnacles are a foundation species in intertidal habitats. During the Pacific Marine Heatwave (PMH), intertidal barnacle cover increased in the northern Gulf of Alaska (GoA); however, the role of pelagic larval supply in this increase was unknown. Using long-term monitoring data on intertidal benthic (percent cover) and pelagic larval populations (nauplii and cyprid concentrations), we examined potential environmental drivers (temperature, chlorophyll-a, mixed layer depth) of larval concentration and whether including larval concentration at regional and annual scales improved intertidal barnacle percent cover models in two study regions in the GoA. In both regions, larval concentrations were slightly higher following the PMH. Percent cover models were improved by including cyprid concentrations (but not nauplii), and the effect strength varied by site and tidal elevation. This indicates that larval concentration contributes as a bottom–up driver of benthic barnacle abundance. There is little evidence of a direct effect of the PMH on either life stage. Instead, our results may illustrate the positive feedback between life stages, where higher adult benthic abundance increased larval concentrations, which then supplied more new recruits to the benthos. As heatwaves continue to occur, integrating various data types can provide insights into factors influencing both benthic and pelagic communities.

Tracing offshore marine ecosystem asset changes based on physical accounting: A case of Xiamen Sea Area

Assessing temporal and spatial changes in marine ecosystem assets is critical for the capitalized management of natural resources and their contribution to human well-being. However, quantifying these changes using different inclusion methods in the System National Account is a challenge. Ecosystem accounting has become a popular topic in recent years, particularly after the System of Environmental and Economic Accounting-Ecosystem Accounting was published in 2021. However, few practical studies have been conducted on offshore marine ecosystem accounting, including marine ecosystem assets and services. This study provides a systematic framework to prioritize the assessment of offshore marine ecosystem assets (extent and condition) in physical terms, including the determined indicators of physical accounts and the presentation of accounting results. We then used this framework to assess marine ecosystem assets in the Xiamen Sea Area selected from 2006 to 2020. The results show that: (a) The extent of the marine ecosystem in Xiamen decreased by 8.34% from 349.64 km2 to 320.49 km2, mainly caused by converting intertidal ecosystem into the land due to the demand for urban and industrial use sea. (b) The area of intertidal vegetation habitats (mangroves and salt marshes) increased from 23.22 hm2 to 132.2 hm2, with an increase of 4.7 times. The results also show that the restoration of the marine ecology in Xiamen has achieved remarkable results. (c) The marine ecosystem condition comprehensive index in Xiamen increased by 3.13% from 0.32 to 0.33. This shows that the marine ecosystem conditions in Xiamen remain well and have even slightly improved under the pressure of a rapidly developing economy and increasing population. This study provides practical technical methods for assessing offshore marine ecosystem in physical term to support integrated coastal management in coastal cities, and is important for assessing marine ecosystem services in the future.

Review of ecological valuation and equivalency analysis methods for assessing temperate nearshore submerged aquatic vegetation.

Nearshore seagrass, kelp, and other macroalgae beds (submerged aquatic vegetation [SAV]) are productive and important ecosystems. Mitigating anthropogenic impacts on these habitats requires tools to quantify their ecological value and the debits and credits of impact and mitigation. To summarize and clarify the state of SAV habitat quantification and available tools, we searched peer-reviewed literature and other agency documents for methods that either assigned ecological value to or calculated equivalencies between impact and mitigation in SAV. Out of 47 tools, there were 11 equivalency methods, 7 of which included a valuation component. The remaining valuation methods were most commonly designed for seagrasses and rocky intertidal macroalgae rather than canopy-forming kelps. Tools were often designed to address specific resource policies and associated habitat evaluation. Frequent categories of tools and methods included those associated with habitat equivalency analyses and those that scored habitats relative to reference or ideal conditions, including models designed for habitat suitability indices and the European Union's Water and Marine Framework Directives. Over 29 tool input metrics spanned 3 spatial scales of SAV: individual shoots or stipes, bed or site, and landscape or region. The most common metric used for both seagrasses and macroalgae was cover. Seagrass tools also often employed density measures, and some categories used measures of tissue content (e.g., carbon, nitrogen). Macroalgal tools for rocky intertidal habitats frequently included species richness or incorporated indicator species to assess habitat. We provide a flowchart for decision-makers to identify representative tools that may apply to their specific management needs.

Protecting a complex intertidal habitat in the severn estuary affected by jetty construction

This case-study presents a coastal engineering scheme that addressed a unique environmental challenge on a marine construction site. Artificially bunded reservoirs were constructed on the rocky shore of the Bristol Channel, United Kingdom, to mitigate the potential impact to ecological features of the Severn Estuary/Môr Hafren Special Area of Conservation resulting from the construction of a jetty at the Hinkley Point C construction site. The installation of piles irreversibly altered the natural supply of seawater from several large rock pools to Corallina officinalis (red seaweed) waterfalls, that the developer, EDF, was obliged to protect. Corallina can die within 30 minutes of drying out. Following rigorous topographic surveys of the foreshore, hydrodynamic modelling, and an evolution of protective measures, concrete structures were designed and installed to ensure the Corallina waterfalls were passively supplied with a constant flow of seawater throughout the tidal cycle. The artificial bunds had to be sympathetic to the natural environment while sufficiently durable to withstand the high-energy conditions of the intertidal site. A local wave buoy 13.5-year dataset shows that the scheme has withstood the two highest wave heights recorded, one of which was the third highest storm peak.

Historical insights, current challenges: tracking marine biodiversity in an urban harbor ecosystem in the face of climate change

The Boston Harbor Islands is the only coastal drumlin archipelago in the USA, featuring a distinctive and uncommon geological intertidal habitat known as mixed coarse substrate, which supports a range of coastal species and ecological processes. Recently designated as one of America’s 11 most endangered historic places due to climate change impacts, coastal adaptation and restoration efforts are crucial to their preservation. Such efforts can benefit from historic and current knowledge of endemic and emergent biodiversity. To investigate broad trends in coastal biodiversity, we compiled an inventory of marine coastal macroalgae, macroinvertebrates, fish, mammals, and shorebirds observed in the harbor since 1861. Records span 159 years, consisting of 451 unique taxa from 19 phyla. Analysis of average taxonomic distinctness (AvTD) revealed increases in diversity towards the end of the twentieth and early twenty-first century, likely associated with improved water quality (dissolved oxygen; AvTD > 85, p = 0.01) due to harbor restoration in the 1980s. Macroinvertebrates comprised 50% of the records, making this the most diverse taxonomic group in the time series. A significant increase of non-indigenous species, primarily macroinvertebrates and macroalgae, was observed over the last 20 years near human infrastructure and across multiple islands, a consequence of global change and characteristic of most urban harbors. The mixed coarse intertidal habitat, which makes up > 70% of Boston Harbor’s inner islands and supports high macroinvertebrate and macroalgal diversity (47% of species records), is not routinely monitored; our findings serve as a foundational resource for climate adaptation projects and decision-making.

Biodiversity of mudflat intertidal viromes along the Chinese coasts

Viruses constitute the most diverse and abundant biological entities on Earth. However, our understanding of this tiniest life form in complex ecosystems remains limited. Here, we recover 20,102 viral OTUs from twelve intertidal zones along the Chinese coasts. Our analysis demonstrates high viral diversity and functional potential in intertidal zones, encoding important functional genes that can be potentially transferred to microbial hosts and mediate elemental biogeochemical cycles, especially carbon, phosphate and sulfur. Virus-host abundance dynamics vary among different microbial lineages. Viral community composition is closely associated with environmental conditions, including dissolved organic matter. Concordant biogeographic patterns are observed for viruses and microbes. Viral communities are generally habitat specific with low overlaps between intertidal and other habitats. Environmental factors and geographic distance dominate the compositional variation of intertidal viromes. Overall, these findings expand our understanding of intertidal viromes within an ecological framework, providing insights into the virus-host coevolutionary arms race.

Utilizing sentinel-1 SAR for delineation of narrow intertidal zones and habitat types in Svalbard

ABSTRACT Intertidal habitats have been significantly impacted by accelerated climate change in Arctic regions over the past few decades, particularly in Svalbard. New substrates are exposed as glacier retreat, making them accessible to benthic vegetation. Remote sensing techniques, including Sentinel-1 synthetic aperture radar (SAR) imagery and drones, provide the opportunity to acquire and study submerged habitats when they are exposed to the atmosphere during low tide. St. Jonsfjorden, Eidembukta, and Trygghamna were the three bays in Svalbard where this research was conducted. We used SAR imagery to determine relatively narrow intertidal zones, acknowledging that the spatial resolution of Sentinel-1 SAR imagery is limited to 10 m. Although this limitation posed a challenge when attempting to classify these narrow intertidal zones due to the coarse resolution of the data, we categorized the intertidal zones into three habitat types: vegetated rock, rock, and mixed sediment. The accuracy of this classification was consistently reliable, with a range of 64–78%. The classification results indicated that 25% of the total intertidal zone is composed of substrates that are suitable for macroalgae growth. It is remarkable that 80% of this substrate is vegetated. Additionally, this investigation demonstrated that vegetation is significantly absent in areas adjacent to glaciers. The magnitude of the glacier appears to influence the extent of this vegetation-free zone.

Community Structure of Intertidal Macrofauna: Spatial Autocorrelation of Two Rocky Coasts of Gujarat, India

The present study describes the community structure of intertidal macrofauna on two rocky coasts of the Kathiawar Peninsula, Gujarat State. The results show significant spatial autocorrelation between the two study sites, with the Mantel correlogram identifying contrasting patterns of species distribution across the coasts. The Veraval coast shows a strong positive correlation owing to its rocky coastal regions. The homogeneity of the intertidal habitats leads to a diverse and cohesive macrofaunal community. In contrast, the Adri coast displays a negative correlation, attributed to the heterogeneous habitats of its intertidal zones. The combination of sandy and rocky patches creates a range of microhabitats, resulting in distinct ecological regions within the coast. This environmental variability promotes a more distinct and less uniform distribution of species. The study underscores the importance of conducting further ecological research on diverse marine ecosystems, particularly in areas with varied habitat types.

Effects of variations in hydrological connectivity on the macrobenthic community structure in reclaimed wetlands

The Nanhui Dongtan Wetland is the most extensively reclaimed part of the Yangtze River Estuary wetland. In recent decades, urbanization has led to the extensive reclamation of the intertidal wetlands of Nanhui Dongtan. Macrobenthos are crucial as secondary production groups in the food web. However, there is a lack of in-depth research on the response mechanisms of macrobenthic communities to environmental disturbances in reclaimed wetlands. This study investigated the impact of hydrological connectivity changes caused by land reclamation on the macrobenthic community based on the macrobenthic community composition in preserved tidal flats and closed and open reclamation areas in Nanhui Dongtan. The results showed that the macrobenthos species richness in the closed reclamation area was significantly lower than that in the other areas. After dividing the functional groups of macrobenthos, structural equation modeling revealed a negative correlation between the salinity and the functional group composition. Analysis of the food sources revealed significant positive correlations between predatory and sediment-feeding populations and sediment organic matter content, between detritivorous group and environmental chlorophyll-a content, and between herbivorous group and suspended organic matter content in water. Therefore, variations in hydrological connectivity in different reclamation areas caused differences in food source distribution, which led to different compositions of macrobenthic functional groups. The results of this study provide a theoretical reference for the study of intertidal wetland habitat restoration.

Colonization of mudflat substrate by microarthropods: the role of distance, inundation frequency and body size

Salt marshes represent a unique ecosystem at the marine-terrestrial boundary of shallow protected coastlines. Microarthropods form an essential component of soil food webs, but how they colonize new intertidal habitats is little understood. By establishing two experimental systems without animals, we investigated microarthropod colonization (1) at the seashore from the pioneer zone to the lower and upper salt marsh and (2) at the same tidal height on artificial islands 500 m from the seashore. Potential source populations of microarthropods in the respective zones were also investigated. Colonization of microarthropods after 5 years was consistently faster on the seashore than on the artificial islands. Collembola and Mesostigmata colonized all the zones both on the seashore and on the artificial islands, with colonization being faster in the upper salt marsh and in the pioneer zone than in the lower salt marsh. Oribatida colonized the new habitats on the seashore, but only little on the artificial islands. Variations in species composition were more pronounced between salt marsh zones than between experimental systems, indicating that local environmental conditions (i.e., inundation frequency) are more important for the assembly of microarthropod communities than the distance from source populations (i.e., dispersal processes). Variations in community body size of Oribatida and Mesostigmata indicated environmental filtering of traits, with smaller species suffering from frequent inundations. Notably, Mesostigmata most successfully colonized the new habitats across salt marsh zones on both systems. Overall, the results document major mechanisms of colonization of intertidal habitats by microarthropods with different life histories and feeding strategies.

Prevalence and seasonal variation of Olpidiopsis porphyrae (Oomycota) infecting red algal Bangiales from the Southern Pacific

ABSTRACT The Bangiales are one of the most common seaweeds in sub-Antarctic and Southeastern Pacific upper intertidal habitats. Here we report records of an ‘olpidioid’ marine obligate parasite infecting Bangiales between 39°20′–41°44′S in the Southeastern Pacific for the first time. The disease resembles the ‘Olpidiopsis blight disease’ reported for farmed Bangiales in Japan and Korea and wild Pyropia from Scotland morphologically and developmentally. The Chilean isolate infects commercial Chilean laver or ‘luche’ (Porphyra sensu lato) and Bangia sensu lato from wild populations in the Southeastern Pacific. Phylogenetic markers (cox2, 18S) identify it as Olpidiopsis porphyrae. We relate the occurrence of this pathogen to both ‘luche’ fisheries in Chile and the potential consequences for its emergent aquaculture in the Southeastern Pacific.

Latitudinal gradients and sex differences in morphology of the Black Oystercatcher (Haematopus bachmani).

Environment and behavior are widely understood to affect bird morphology, which can lead to differences among subspecies or populations within a wide-ranging species. Several patterns of latitudinal gradients in morphology have been described, though Allen's and Bergmann's rules are the most well-known and have been tested and confirmed across a diversity of taxa and species. These state that individuals at higher latitudes will have larger bodies (Bergmann's Rule) but smaller extremities (Allen's Rule) to conserve heat in colder climates. Migratory behavior also can influence avian morphology, particularly wing shape, where migratory birds tend to have longer, more pointed wings than residents. The Black Oystercatcher (Haematopus bachmani) is a large, partially migratory shorebird species restricted to intertidal habitats and distributed from Alaska to Baja California, spanning about 35° of latitude. A large proportion of Black Oystercatchers that breed in Alaska are migratory, where nearly all individuals breeding in British Columbia through the southern end of their range remain resident through the annual cycle. Their broad latitudinal range and diversity in migratory behavior may drive geographic variation in morphology. Here we evaluate three explanations for geographic variation in morphology of the Black Oystercatcher using data from seven sites across two regions: Alaska and British Columbia. We found evidence consistent with Allen's but not Bergmann's rule; birds in Alaska have shorter bills than those in British Columbia, and these findings held when controlling for body size using wing length. Despite regional differences in migratory behavior, we detected no difference in the wing shape of birds in Alaska and British Columbia. Differences between sexes and among sites suggest that multiple factors drive patterns of morphological variation in the Black Oystercatcher.

Comparative analysis of water-use strategies in three subtropical mangrove species: a study of sap flow and gas exchange monitoring.

Water-use strategies play a crucial role in the adaptive capabilities of mangroves to the saline intertidal conditions, yet the intricacies of daily water-use patterns in mangrove species, which are pivotal for maintaining water balance, remain poorly understood. In this comprehensive study, we aimed to clarify the water use strategies of three co-occurring mangrove species, Avicennia marina, Aegiceras corniculatum and Kandelia obovata, through stem sap flow monitoring, leaf gas exchange and stem diameter change measurements. Our findings revealed that the daily sap flow density of Avicennia and Aegiceras reached the peak about 1 h earlier than that of Kandelia. When transpiration was strong, Kandelia and Aegiceras used stem storage to meet water demand, while Avicennia synchronized stem water storage. These three mangrove species adopted cross-peak water used and unique stem water storage to regulate their water balance. In Kandelia, the daily sap flow in per sapwood area was significantly lower, while water-use efficiency was significantly higher than those of Avicennia and Aegiceras, indicating that Kandelia adopted a more conservative and efficient water-use strategy. Sap flow in Avicennia was the most sensitive to environmental changes, while Kandelia limited water dissipation by tightly controlling stomata. Meteorological factors (photosynthetically active radiation, vapor pressure deficit and air temperature) were the main driving factors of sap flow. The increase of soil temperature can promote the water use of mangrove species, while the increase of salinity resulted in more conservative water use. Our results highlight the diversity of daily water-use strategies among the three co-occurring mangrove species, pinpointing Kandelia as the most adaptive at navigating the changing conditions of intertidal habitats in the future climate. In conclusion, our findings provide a mesoscale perspective on water-use characteristics of mangroves and also provides theoretical basis for mangroves afforestation and ecological restoration.

Vertical arrays of artificial rockpools on a seawall provide refugia across tidal levels for intertidal species in the UK

Eco-engineering of coastal infrastructure aims to address the insufficient intertidal habitat provided by coastal development and flood defence. There are numerous ways to enhance coastal infrastructure with habitat features, but a common method involves retrofitting artificial rockpools. Often these are ‘bolt-on’ units that are fixed to existing coastal infrastructure but there is a paucity of literature on how to optimise their arrangement for biodiversity.In this study, 24 artificial rockpools were installed at three levels between High Water Neaps and Mean Tide Level on a vertical concrete seawall on the south coast of the UK. The species abundance of the rockpools and adjacent seawall were surveyed at low tide for 2 years following rockpool installation and compared. Over the course of the study, sediment had begun to accumulate in some of the rockpools. At the 2-year mark, the sediment was removed and assessed for macrofauna. Algal biomass of the seawall and rockpools was estimated using previously obtained dry weight values for the dominant algae taxa.After 2 years, it was determined that artificial rockpools successfully increase species richness of seawalls, particularly at higher tidal levels where water-retaining refugia are crucial for many species. The rockpools hosted 37 sessile taxa and 9 sessile taxa were recorded on the seawall. Rockpools increased the vertical elevation for brown canopy-forming seaweeds by providing better attachment surfaces. Although the retained sediment only hosted 3 infaunal species, it was observed to provide shelter for shore crabs during surveys. As sea levels and ocean and air temperatures continue to rise, vertical eco-engineering arrangements will play a crucial role in allowing species to migrate up the tidal zone, negating habitat loss and localised extinction.