Intertidal Rocky Shores Research Articles

Revisiting the taxonomy of Korean Ischnochiton species (Polyplacophora, Ischnochitonidae) based on a combined analysis of morphological and molecular data.

Chiton species belonging to the genus Ischnochiton J. E. Gray, 1847 are commonly found in intertidal rocky shores worldwide, with the exception of the northern Atlantic and Arctic oceans. Ischnochiton species are characterised by imbricate girdle scales that are uniform in size, rounded, sculpted with striae or occasionally smooth. However, their species-level taxonomy is complicated due to the high variation in their shell microstructures. Despite more than a hundred species reported worldwide, taxonomic studies of this group remain relatively unexplored in Korean waters, with only a few species recorded to date. In this study, we compared the microstructural characteristics of tegmentum sculpture, girdle scales and radula amongst four Korean Ischnochiton species using high-resolution microscopic images and a scanning electron microscope (SEM). Along with mtDNA cox1 sequence comparison, a comprehensive analysis of their morphology revealed that I.hayamii Owada, 2018 was identified for the first time in Korean waters. This species is morphologically distinguished by its small body size of adults, smooth lateral areas on valves and small perinotum scales sculptured with weak longitudinal ribs. Phylogenetic analysis of the mtDNA cox1 sequence provides distinct resolution at the species level, but interrelationships amongst Ischnochiton species remain unresolved. Results from the morphological and molecular analyses presented in this study offer valuable taxonomic information for accurate species identification amongst closely-related Ischnochiton species.

Rapid diagnosis of the geospatial distribution of intertidal macroalgae using large-scale UAVs

Macroalgae have been used as indicators of the health of coastal ecosystems, they function as sinks of CO2 and are essential contributors to primary production. With the increase in anthropogenic activities, it is crucial to assess the impact of such activities on these ecosystems. As traditional surveying techniques, although accurate, are time-consuming and their area coverage is limited, novel techniques are required to monitor the coverage and diversity of intertidal macroalgae. We propose a methodology using the free-source Semi-Automatic Classification Plugin from QGIS to use UAV and multispectral cameras for the spatiotemporal monitoring of intertidal macroalgae. We also compared the performance of six classifiers: Minimum Distance (MD), Maximum Likelihood (ML), Spectral Angle Mapping (SAM), Multi-Layer Perceptron (MLP), Random Forest (RF) and Support Vector Machine (SVM), for three types of macroalgae classification: general, taxonomical groups and species. As proof of concept, an intertidal rocky shore in a marine protected area (NW Spain) was studied for four months. RF and SVM achieved similar results, with both being recommended for the general (OASVM = 97.4±1.7 and OARF = 98.3±1.7) and taxonomical groups (OASVM = 91.6±1.9 and OARF = 89.2±4.5). SVM and ML were found to be more suitable for species classification (OASVM = 77.4±11.4 and OAML = 74.2±9.7). SAM and MLP provided the least performant species classifiers because of the overlap in the macroalgae spectral signatures. The plugin showed limitations when tuning the input parameters of the MLP classifier and did not let to add a validation dataset. Additionally, we present an open-access GIS web application, Alganat 2000 GIS web, to facilitate the monitoring and management of coastal areas. We conclude that the proposed methodology using the SVM or ML classifiers is an effective tool for assessing intertidal macroalgal assemblages. Its easy and rapid implementation is beneficial for researchers who are not very familiar with coding and machine learning frameworks and reduces the time and cost of fieldwork. As future work, we propose the combination of the multispectral bands with topographic and spectral indices and to research the application of deep learning models to the classification of intertidal macroalgae.

Ecology of Intertidal Rocky Shores Related to Examples of Coastal Geology across Phanerozoic Time

The boundary between land and sea is among the most extensive and extreme ecological barriers on planet Earth. Intertidal organisms living at this junction are subject to potentially lethal conditions related to desiccation, temperature fluctuations, and wave shock. Although difficult to quantify at a global level, rocky coasts account for between a third and three-quarters of all shorelines today. Resistant to coastal erosion, rocky coasts also exhibit adaptations by marine invertebrates and marine algae within intertidal zones that are geographically widespread. Biotic composition is variable depending on the tidal range at any given place and on climatic differences between tropical and more temperate latitudes. Contemporary granite shores having low recession rates with well-established biotic zones are reviewed in three regions: Mount Desert Island in Maine, USA (44° N latitude), Mahé and Praslin islands in Seychelles (4°30′ S Latitude), and Lizard Island off the coast of Queensland, Australia (14°40′ S Latitude). The zonal composition and overall biotic diversity at these locations are compared, as well as the fossilization potential of key biota. Over the Phanerozoic time period during the last 538 million years, the ratio between land and ocean varied as a function of plate tectonics depending on the maximum dispersal or coalescence of continents and on relative changes in global sea level. Fossil biotas from a dozen paleoislands with dominant rocky shores that range from 485 million to 125,000 years in age are reviewed to show diversification through time, taking into account episodic mass extinctions. Relationships between storm tracks and volcanic eruptions that factor into physical disruptions are also considered as means of rapid burial and preservation. Themes related to rocky-shore ecology and paleoecology benefit from the cross-fertilization of ideas by marine biologists and marine paleontologists. It is hoped this review may attract a cohort of new students to these allied fields of study, especially in Asia, Africa, and South America.

Snail shell shape, force of attachment, and metabolic rate together cope with the intertidal challenge

Inhabitants of rocky intertidal shores, including gastropods, require specific adaptations to cope with numerous challenges that vary across the intertidal levels. We collected Stramonita biserialis snails from upper (wave-protected and intense predation) and lower (wave-exposed and low predation) intertidal sites to compare the following traits: shell skeleton (ventral and abaxial lateral views of shell shape, thickness, and mass), foot size, energy metabolism, and attachment strength to determine whether the trait values of snails from each zone fit the environmental challenges they face. We used a Principal Component Analysis to reduce the dimensionality of the data. Multivariate Analysis of Covariance (MANCOVA) for comparing characteristics between the two intertidal zones, and Partial Least Squares (PLS) analyses for testing the integration of overall snail characteristics. The traits of the snails of the two intertidal sites matched with the adaptations expected to allow them to cope with their contrasting challenges. The snails from the lower intertidal had more streamlined shells (which reduces drag forces) and a larger aperture and foot extension (which increase the strength of their attachment to the substrate) compared to snails from the upper sites. Snails from the lower intertidal also had a high mass-specific metabolism and soft body proportion, indicating that these snails from the wave-exposed sites have an energetically active musculature that matches their strong substrate attachment. The thin shell walls of the snails of the lower intertidal match the relatively low predatory pressure there.

Investigating the interactive effects of habitat type and light intensity on rocky shores

Light availability and habitat complexity are two key drivers of community assembly. Urbanisation has been shown to affect both, with important consequences to ecological communities. On the intertidal, for instance, studies have shown that light intensity is greater on natural rocky shores than on less complex artificial habitats (seawalls), though different habitats can also experience similar light intensities, for example when shaded by urban structures. Understanding therefore how these factors individually, and combined, affect communities is important to understand the mechanisms driving changes in community structure, and consequently provide solutions to tackle the increasing homogenisation of habitats and lightscapes in urbanised spaces through smart infrastructure designs. Here, we assessed how different light levels affect the recruitment of communities in rock pools and on emergent rock on an intertidal rocky shore. We cleared 30 patches of emergent rock and 30 rock pools and manipulated light using shades with different light transmissions (full light, procedural control, 75%, 35%, and 15% light transmission, full shade) and assessed mobile and sessile communities monthly for 6 months. Effects of reducing light levels were generally stronger on rock than in pools. Fully shaded plots supported double the amount of mobile organisms than plots in full sunlight, in both habitats. Algal cover was higher in pools compared to rock, and at intermediate light levels, but effects varied with site. This study highlights the importance of variable light conditions and different habitats for rocky shore communities, which should be considered in future coastal developments to retain natural biodiversity.

Ribbon worms (phylum Nemertea) from Bodega Bay, California: A largely undescribed diversity.

The diversity of nemerteans along the Pacific coast of the United States is regarded as well characterized, but there remain many cryptic, undescribed, and "orphan" species (those known only in their larval form). Recent sampling of nemerteans in Oregon and Washington has begun to fill in these taxonomic gaps, but nemertean diversity in California has received relatively little attention over the past 60 years. During the summers of 2019 and 2020, nemertean specimens were collected from 20 locations in the Bodega Bay region of northern California, USA, including rocky intertidal shores, sandy beaches, mudflats, and other habitats. Based on morphological assessment and DNA sequence analysis (partial Cytochrome Oxidase I and 16S rRNA genes), our surveys identified 34 nemertean species. Only 13 of these (38%) can be confidently assigned to described species. Another 11 represent species that are new to science, including members of the genera Riserius, Nipponnemertes, Poseidonemertes, Zygonemertes, Nemertellina, Oerstedia, and three species of uncertain affiliation. The remaining ten species include undescribed or cryptic species of uncertain status that have been found previously along the Pacific Coast of North America. Our surveys also document extensions of known geographic ranges for multiple species, including the first records in California of Antarctonemertesphyllospadicola, Cephalothrixhermaphroditica, and Maculauraoregonensis. This is the first report of the genus Nemertellina in the northeast Pacific and Riserius in California. Overall, our findings highlight how much remains to be learned about the diversity and distribution of nemerteans in the northeast Pacific.

Seabird-vectored pelagic nutrients integrated into temperate intertidal rocky shores

Seabirds provide inter-habitat connectivity by transporting vast quantities of nutrients from their pelagic feeding grounds to terrestrial and marine ecosystems via their nitrogen and phosphorous rich guano. However, it remains unclear whether seabird nutrients are cycling through many nearshore, temperate systems, such as United Kingdom (UK) rocky shores. Furthermore, it also remains unknown how seabird nutrient subsidies impact biodiversity, productivity, and recolonisation rates in UK rocky intertidal systems. Here, the impact of seabird nutrient subsidies to the Farne Islands, Northumberland, areas of high seabird densities during their breeding seasons, was compared to nearby low seabird density areas on the Northumberland coast. Estimated seabird derived nitrogen inputs and seabird densities were 420-1,025 and 949-2,279 times higher, respectively, on seabird islands than on the mainland. Seabird derived nutrient inputs led to substantially enriched nitrogen stable isotope (δ15N) values and total nitrogen content in terrestrial soil, plants, and lichen, and intertidal barnacles, and limpets, and higher δ15N values in macroalgae and turf algae. The seabird islands contained marginally greater algal species richness and higher densities of intertidal predators. However, other drivers could not be ruled out, such as nutrient inputs from mainland sources and marginally higher wave exposure at the mainland sites. No difference in limpet size, biomass, or abundance existed between the seabird islands and the mainland. On plots artificially cleared to simulate a disturbance event, barnacles recolonised faster on mainland sites. These findings provide evidence that seabird vectored pelagic nutrients are incorporated into terrestrial and intertidal ecosystems of UK islands, and therefore play an important role in facilitating ecosystem connectivity.

The Multiphasic Teeth of Chiton Articulatus, an Abrasion‐Resistant and Self‐Sharpening Tool for Hard Algae Collection

AbstractChiton articulatus is a species of mollusk living in the tropical Pacific intertidal rocky shores of Mexico. This species feeds on solid waste organic sources, including hard crustose algae that grow on rocky substrates, by grazing on them with its radula, a flexible chitinous membrane lined with mineralized major lateral teeth. In this study, the composition, morphology, and resulting mechanics of the mature teeth of this species, which have yet to be examined, are revealed. The results show the presence of multiphasic mature teeth, each consisting of aligned hard magnetite nanoparticles on the leading edge of the tooth underneath which are magnetite lamellae, followed by goethite, lepidocrocite, and eventually hydroxyapatite near the trailing edge. This multiregional structure demonstrates a gradation in hardness as well as different microstructural features integrated with tough interfaces. The combination of these microstructural and phase arrangements results in an abrasion‐resistant tough structure with a self‐sharpening ability. The results of this work will help contribute to developing new bioinspired designs while also helping to understand the evolution and feeding habits of these intriguing invertebrates.

Effects of harvesting and an invasive mussel on intertidal rocky shore communities based on historical and spatial comparisons.

Intertidal rocky shores are the most accessible marine habitats and therefore heavily impacted by harvesting. In recent years, they have also been increasingly invaded by alien species, which compounds the effects of harvesting on rocky shore community composition and functioning. Recent survey data, combined with historical data from 1970, were used to assess temporal changes over the intervening period in rocky shore communities at two sites (Wireless Point and Wireless Island). Three kinds of changes emerged: (1) the appearance of alien species; (2) the effects of increased harvesting pressure; and (3) the direct and indirect effects of these changes on other species. A striking result was transformation of mid-shore zones on exposed shores by the appearance of the invasive Mediterranean mussel Mytilus galloprovincialis, and the indirect effects of this on the demography and vertical zonation patterns of the granular limpet Scutellastra granularis. Adult limpets have become excluded by the mussel, whereas juveniles find a secondary home on the shells of the mussel and their abundance has increased. To further disentangle the effects of harvesting from those of alien invasions, a spatial comparison was made between two currently unharvested no-take sites (Scarborough South and Scarborough North) and two regularly harvested sites (Kommetjie and Wireless Point). Harvesting has substantially depleted the granite limpet Cymbula granatina and Argenville's limpet Scutellastra argenvillei. This has led to the proliferation of opportunistic seaweeds, such as Ulva spp. The dual effects of alien invasive species and over-harvesting have major ecosystem effects but do not necessarily diminish biodiversity because the alternative habitats that have developed provide opportunities for colonisation by additional species.

Microbial community and network responses across strong environmental gradients: How do they compare with macroorganisms?

The way strong environmental gradients shape multispecific assemblages has allowed us to examine a suite of ecological and evolutionary hypotheses about structure, regulation and community responses to fluctuating environments. But whether the highly diverse co-occurring microorganisms are shaped in similar ways as macroscopic organisms across the same gradients has yet to be addressed in most ecosystems. Here, we characterize intertidal biofilm bacteria communities, comparing zonation at both the "species" and community levels, as well as network attributes, with co-occurring macroalgae and invertebrates in the same rocky shore system. The results revealed that the desiccation gradient has a more significant impact on smaller communities, while both desiccation and submersion gradients (surge) affect the larger, macroscopic communities. At the community level, we also confirmed the existence of distinct communities within each intertidal zone for microorganisms, similar to what has been previously described for macroorganisms. But our results indicated that dominant microbial organisms along the same environmental gradient exhibited less differentiation across tidal levels than their macroscopic counterparts. However, despite the substantial differences in richness, size and attributes of co-occurrence networks, both macro- and micro-communities respond to stress gradients, leading to the formation of similar zonation patterns in the intertidal rocky shore.

Latitudinal biodiversity gradients of rocky intertidal assemblages: Spatial scales and complex associations with environmental factors

AbstractLatitudinal biodiversity gradients vary across taxonomic groups and spatial scales, and various environmental factors have been associated with those patterns. However, it remains unknown whether taxonomic groups with strong ecological associations have similar or different latitudinal patterns. Macroalgae are foundation assemblages on rocky intertidal shores and are often inhabited by invertebrates, predominantly polychaetes. This study analysed latitudinal patterns of macroalgae and their associated polychaetes at different spatial scales and determined how environmental factors influenced those patterns. Macroalgae and polychaetes were collected from transects within 38 rocky intertidal shores of Western Australia at 14 latitudes between 18° S and 34° S. Latitudinal gradients in species richness, diversity (Simpson's diversity index) and abundance were evaluated at transect, site and latitudinal scales. Relationships between environmental factors and rocky intertidal assemblages were analysed using piecewise structural equation modelling based on direct, indirect and complex models. Macroalgae showed increases in species richness, diversity and abundance at transect and site scales towards high latitudes, but species richness and diversity patterns were unclear at the latitudinal scale where transect and site data were pooled. In contrast, polychaete diversity decreased towards high latitudes, although this pattern was unclear at the transect scale. Polychaete richness and abundance tended to follow parabolic patterns that peaked at 27° S. Relationships between environmental factors and rocky intertidal assemblages were best described by a complex model, with significant relationships more often at transect and site scales. Sea surface temperatures showed the strongest relationship with macroalgal and polychaete distributions.

Obituary: Eve Caroline Southward (née Judges) 1930–2023

Abstract Eve Caroline Southward (1930–2023) was a multi-talented scientist, motivated by her curiosity and love of nature. Since she was never paid as a scientist, Eve was an amateur, in the best sense of the word. She was highly proficient at transmission electron microscopy and made lasting contributions to polychaete taxonomy, morphology and ecology. Eve was internationally respected, especially for her studies on the Siboglinidae, mouthless and gutless tubeworms (formerly called Pogonophora) that are found worldwide in the deep-sea. She described how the siboglinids obtained nutrition from symbiotic, sulphur-oxidising bacteria and described similar symbiotic relationships in several bivalve species. Eve wrote over 140 scientific publications and described 56 new benthic species, 47 being mouthless and gutless ‘pogonophores’. Eve assisted her husband Alan Southward in starting broad-scale intertidal surveys around the British Isles and Northwest Europe. These surveys formed the foundation for the time-series, later continued by others, that allowed assessments of the influence of climatic fluctuations, using intertidal rocky shore biota as indicators. Eve contributed, with Alan, to what became a 50-year study describing the long-term effects on intertidal communities of the oil pollution and excessive dispersant use resulting from the Torrey Canyon oil spill in 1967. Eve also co-wrote the Linnaean Society Synopsis on Echinoderms of the British Isles and helped complete unpublished work by Alan Southward and others on barnacle taxonomy.

A facultative mutualism between habitat-forming species enhances the resistance of rocky shore communities to heat waves

Heat waves have increased in frequency, duration, and magnitude in recent decades, causing mass mortality events in terrestrial and aquatic ecosystems. Arguably, mass mortalities of habitat-forming organisms – i.e., dominant sessile organisms that define habitats via their own physical structure – would be amongst the most dramatic impact of heat waves because of their negative, cascading consequences on their associated biodiversity. However, the resistance of habitat-forming organisms to heat waves can be enhanced if they associate with secondary habitat formers able to tolerate and modulate extreme heat levels. Here we show that a seaweed of the Porphyra/Pyropia (P/P) clade can shield primary habitat-forming mussels, Brachidontes rodriguezii, from the impacts of extreme temperatures in a southwestern Atlantic rocky intertidal shore. By means of P/P removal experiments and surveys, we illustrate that P/P cover (a) buffers temperatures in the understory mussel beds during daytime air exposure periods in the summer, (b) reduces mussel mortality and leads to increased mussel body condition during warm summer periods, and (c) can prevent mass mortality of mussels during the course of a heat wave. Additionally, by means of a mussel removal experiment we illustrate that mussel cover is critical for P/P establishment, which is in consonance with the remarkably higher P/P densities and cover observed in mussel beds relative to exposed rock surfaces across a ~70 km coastal range. Collectively, these findings reveal a facultative mutualism where mussels provide a favorable substrate for P/P colonization and P/P attenuates heat mediated mortality on mussels. The ability of P/P to enhance the resistance of mussel beds to extreme heat events and the occurrence of similar P/P-mussel associations during spring-summer at globally dispersed sites suggests a widespread importance of P/P for the stability of mussel beds and their associated communities under warming climates.

Spatial variation in key functional traits of Mediterranean fucoid algae: Insights from Cystoseira sensu lato intertidal canopies

Cystoseira sensu lato are fucoid algae that form dense stands on intertidal and subtidal rocky reefs sustaining species-rich associated assemblages. The increasing human pressure is causing the decline of these marine forests, raising wide concerns on the ecological consequences of their loss. Yet, little is known about functional trait variables of Cystoseira s.l. species, which are essential to a deeper understanding of their contribution to the functioning of coastal ecosystems. We analysed the intraspecific spatial variation of the total organic matter, Corg, N and P contents in Ericaria amentacea from intertidal rocky shores in the W Mediterranean Sea. Specifically, we quantified spatial patterns of variation of traits at large (100s km), small (1000s m), and local (100s cm) scale. We also explored potential interspecific variation by comparing the combined functional profile of trait variables between E. amentacea and Cystoseira compressa, an often co-occurring or vicariant species. Tissue contents of organic matter, Corg, N and P, were consistent among E. amentacea stands, supporting the hypothesis of a large-scale (100s km) spatial homogeneity of such key traits in this species. Overlapping functional profiles between E. amentacea and C. compressa also suggested putative interspecific trait congruencies. However, a small-scale (1000s m) significant variability was found for all trait variables in E. amentacea. Variance components at small (1000s m) and local (100s cm) scale accounted for the largest contribution to the total spatial variation for all traits, recommending caution in the use of small and local-scale trait values to generalize functional performances of Cystoseira s.l. forests over large areas. This study represents one of the first attempts to shed light on the variability of key functional attributes of Cystoseira s.l. species at a range of spatial scales, which could assist more reliable assessments of their functional role and improve their management and conservation.

Exploring the adaptability of the secondary structure of mRNA to temperature in intertidal snails based on SHAPE experiment.

RNA-based thermal regulation mechanism is an important strategy for organisms to cope with temperature changes. Inhabiting on intertidal rocky shore, a key interface of the ocean, atmosphere and terrestrial environments, intertidal species have developed variable thermal adaptation mechanisms, however, adaptions at the RNA level remain largely uninvestigated. For investigating the relationship between mRNA structural stability and species distribution, in the present study, the secondary structures of cytosolic malate dehydrogenase (cMDH) mRNAs of Echinolittorina malaccana, E. radiata and Littorina brevicula were determined using the selective 2'-hydroxyl acylation analyzed by primer extension (SHAPE), and the change in folding free energy of formation (ΔGfold) were calculated. The results showed that ΔGfold increased as the temperature increased. The difference in ΔGfold (ΔΔGfold) between two specific temperatures (0° to 25°C, 0° to 37°C, and 0° to 25°C) among the three species were different, and the ΔΔGfold value of E. malaccana was significantly lower than those of E. radiata and L. brevicula. The number of stems of cMDH mRNA of the snails decreased with temperature increased, and the breakpoint temperature of E. malaccana was the highest among them. The number of loops was also reduced with temperature increased, while the length of the loop structure increased accordingly. Consequently, these structural changes can potentially affect the translational efficiency of mRNA. These results implied that there were interspecific differences in the thermal stability of RNA secondary structures in intertidal snails, and these differences may be related to their distribution.

Changing webs—Variation of complex networks over a tidal cycle in an intertidal rocky reef

Incorporating temporal variation in models is one of the most important challenges in food web research. One of the environments where time causes profound changes is the intertidal zone, where the immersion-emersion cycle drastically changes the abiotic and biotic conditions. Intertidal rocky shores have been intensively studied, however the variation in the complex food web network that occurs during a tidal cycle remains undescribed. Highly resolved food web networks were assembled for an intertidal reef depicting the food web during low and high tide, and with and without tide pools. It was concluded that high tide adds new species to the web, but it does not add complexity since network connectance was not changed. This occurs because incoming species are mostly highly generalist fish, which add many new links to the web. Tide pools, however, add not only diversity but also complexity. Webs were dominated by intermediate species, with the proportion of top consumers fluctuating throughout the tidal cycle, being lowest during low tide and highest at high tide, due to the incoming larger vertebrate predators. Consumer taxa outnumbered resource taxa, except at low tide when pools are present. Mean trophic level was lowest at low tide (2.3) and highest at high tide with pools (2.6). Omnivory was high and showed little change. “Chain”, the number of links connecting top to basal species, was stable but low. This implies that disturbance can rapidly travel bottom-up or top-down through predator-prey links. The increased connectance given by the addition of tide pools likely increases robustness to disturbances, an important feature in coastal areas so often impacted by human action.

Null models to explain highly diverse community of intertidal decapods on a temperate rocky coast in Antofagasta, northern Chile (23º27ʹS)

Abstract The decapod fauna on intertidal shores in northern Chile is characterized by its relatively high diversity and abundance due to the presence of continuous upwelling by the Humboldt Current, which results in a high productivity. The decapod fauna on intertidal rocky shores is characterized by coexisting species that inhabits in natural shelters such as cracks and eroded rocks, as well as among macroalgae. We aimed to monitor the brachyuran and anomuran (porcellanid) crabs in three intertidal sites during two periods of time in September-December 2019 in the Antofagasta region, one site without human intervention and two sites in the city of Antofagasta, for which we applied null models in ecology. We assumed that the communities are random, a viewpoint that is more robust because it reduces the risk of error type I. The results of the application of null models on the co-occurrence species revealed that species associations are mainly structured for all sites, whereas the niche-sharing null model revealed that the reported species did not share ecological niches and in consequence there is not interspecific competition. The results would probably indicate that the species of intertidal decapods have a micro-specific ecological-niche differentiation, which would explain the existence of structured pattern in species associations. The results were compared with information for other sites along the continental Chilean coast.

Effects of salinity and irradiance on early developmental stages of <italic>Grateloupia turuturu</italic> (Halymeniaceae, Rhodophyta) tetrasporophytes

<i>Grateloupia turuturu</i> is a red alga with a flat but firm slippery thallus. Throughout its lifetime, this alga experiences a wide range of environmental stresses in the intertidal rocky shores. The aim of this study is to investigate the effect of salinity and irradiance on the early developmental stages of <i>G. turuturu </i>tetrasporophytes. The released carpospores were cultivated at different salinities (S = 15, 25, and 35) and irradiances (50, 100, and 200 μmol photons m<sup>-2</sup> s<sup>-1</sup>). Germination of carpospores and development of juvenile tetrasporophytes were observed every 5 days and recorded by a digital camera. Discoid crusts were formed at all conditions within 5 days. The discoid crusts at 200 μmol photons m<sup>-2</sup> s<sup>-1</sup> died within 20 days regardless the salinity. The discoid crusts at S = 35 also died at all irradiance conditions within 25 days. Except for those at S = 35 and 200 μmol photons m<sup>-2</sup> s<sup>-1</sup>, the discoid crusts reached about 8,000–9,000 μm<sup>2</sup> by day 20. Regardless of irradiance, the upright thalli formation rate from discoid crusts was 85 and 10% at S = 15 and S = 25, respectively. These results suggest that salinity and irradiance are important factors influencing early developmental stages of <i>G. turuturu</i>.

Intertidal macroalgal and epiphytic polychaete distributions strengthen marine ecoregions of Western Australia

The Marine Ecoregions of the World system separates the oceans into 232 ecoregions based on coastal and shelfwater species distributions. We tested the separation of those ecoregions and delineated subecoregions within Western Australian waters using intertidal macroalgal and epiphytic polychaete distributions. Environmental predictors of those assemblages were also determined. We collected macroalgae and polychaetes on 38 rocky intertidal shores within four marine ecoregions from 18°S to 34°S: (1) Exmouth to Broome, (2) Ningaloo, (3) Houtman, and (4) Leeuwin. We evaluated differences in species composition of macroalgae and polychaetes among those ecoregions using pairwise permutational multivariate analysis of variance and delineated subecoregions within each ecoregion using hierarchical cluster analysis. Multivariate relationships between environmental variables and assemblages were determined using distance-based linear models. The species composition of macroalgae and polychaetes significantly differed among ecoregions, with dissimilarity of 78-96% for macroalgae and 62-75% for polychaetes. We identified three subecoregions within Exmouth to Broome and Ningaloo and two subecoregions within Houtman and Leeuwin based on macroalgal distribution. We also found two subecoregions within Houtman and no subecoregion within Exmouth to Broome, Ningaloo, and Leeuwin based on polychaete distribution. Environmental predictors could explain 51% of the total variation of macroalgae and 41% of the total variation of polychaetes. The top two predictors explaining a high proportion of assemblage distribution were sea surface temperature (15% for macroalgae and 12% for polychaetes) and tidal amplitude (10% for macroalgae and 6% for polychaetes). These ecoregions and subecoregions can be used as an alternative spatial framework for classifying rocky intertidal habitats for designing marine protected area networks within Western Australian waters.

High Species Richness of Decapod Crustaceans on an Urban Rocky Shore Beach

The rocky intertidal shore of La Caleta, an urban beach located in Cádiz (SW Spain), was surveyed for decapod crustaceans over a year. Samplings were taken monthly (March 2015 to February 2016) in three differentiated zones during the spring low tides of every month at five sites, differentiated according to the hydrodynamic regimes and intertidal levels. A qualitative sampling (present/absent) was carried out by visual identification (minimally invasive), and only those specimens with uncertain identification were collected by hand, studied at the laboratory, or identified using their DNA barcode. A total of 44 species were identified. Comparison with species richness of decapod crustaceans in other Atlantic and Mediterranean intertidal or subtidal ecosystems (including protected areas) shows higher values in La Caleta, a surprising fact considering the type of habitat and its placement (an urban and unprotected shore).