Intertidal assemblages on groynes along sandy shores in Portugal: Exploring the effects of orientation and distance to rocky shore.

Coastal erosion is becoming increasingly problematic as sea level rise and coastal areas become more urbanised. In response, more defence structures such as groynes are being built, which are crucial for counteracting sediment loss and coastline retreat. Despite worldwide use, comparatively little is known about the factors that determine the species composition on such structures. In this study, the composition and abundance of intertidal benthic species on groynes was investigated as a function of groyne orientation (North vs. South) and distance to natural rocky shores (5 km vs. 42 km). While orientation showed no effect on benthic assemblages, distance to rocky shores was identified as a key factor influencing the assemblage composition. Macroalgae were found in greater abundance further away from rocky shores, while snail and barnacle species were found in greater numbers closer to rocky shores.

Short-term effects of trampling on intertidal Mytilus galloprovincialis beds.

Human trampling represents one of the main anthropogenic pressures in the rocky intertidal. This habitat includes many ecosystem engineers such as mussels that provide biogenic habitat and multiple services. This research assessed potential impacts of human trampling on beds of the mussel, Mytilus galloprovincialis, on NW shores of Portugal. To test for direct effects of trampling on mussels and indirect effects on the associated assemblages, three treatments were applied: control (untouched beds), low and high intensity of trampling. Effects of trampling were dependent on the taxa. Thus, values of shell length of M. galloprovincialis were greater under the highest intensity of trampling while abundances of Arthropoda, Mollusca and Lasaea rubra showed the opposite pattern. Moreover, total number of taxa and abundances of Nematoda and Annelida showed higher values under low trampling intensity. The implications of these results to manage human use in areas with ecosystem engineers are discussed.

Effects of habitat homogenisation on assemblages associated with mussel clumps.

Biodiversity loss is considered one of the main threats to marine ecosystems. In this framework of biodiversity decline, organisms that provide biogenic habitat play a relevant role by their capacity to structure assemblages and influence ecological processes. The Mediterranean mussel Mytilus galloprovincialis is considered an ecosystem engineer because it alters local environmental conditions maintaining habitat suitability for other organisms, and enhancing local biodiversity. Although it is widely recognized that mussel beds increase diversity, the drivers shaping these assemblages are poorly explored. We investigate whether mussel size homogenisation shapes the abundance, richness and structure of macrobenthic assemblages associated with mussel beds in two shores of the Galician coast (NW Spain). At each shore, two sites, 10 m apart, were selected and at each site, faunal assemblages were compared between mussel clumps showing shells of various sizes (control), and mussel clumps with closely similar-sized mussels, considered as homogenised. Homogenised clumps showed, in general, higher values in total number of individuals and species than control clumps. Regarding the effect of mussel size homogenisation on the multivariate structure of the assemblages, significant differences between control and homogenised clumps were found in three out of the four sites. Most relevant associated species usually reached higher abundances in homogenised clumps than control ones. Therefore, mussel size homogenisation influenced the structure of the macrofaunal assemblages associated with mussel beds but, its effect was context dependent (i.e., varied with sites). Information about the species contribution to dissimilarities among homogenised and control clumps was provided and the potential influence of sediment and algae on mussel clumps was discussed.

Reproductive Cycle of the Seagrass Zostera noltei in the Ria de Aveiro Lagoon.

Sexual reproduction in seagrasses is essential to increase their resilience towards environmental stressors, but its phenology is still unknown in some regions, limiting our knowledge about the recovery capacity of these ecosystems. In this study, the flowering effort, reproductive phenology, seed production and ability of germination of Zostera noltei was studied for the first time in the Ria de Aveiro lagoon, Portugal. Flowering of Z. noltei in the Ria de Aveiro lasts from June to November, reaching a peak between July and August. All the meadows showed similar flowering effort and phenology over time. Comparing with other European populations, the flowering effort of Z. noltei in Ria de Aveiro lasted for a longer period, which could be related with the milder temperatures in summer and autumn and the great anthropogenic stress to which the meadows are subjected in the lagoon. The number of seeds produced and their ability of germination were similar among meadows and sampling periods, reaching levels similar to those of other European regions. Nevertheless, future studies are needed to determine the fate of the produced seeds in the field to have a better understanding about the natural recovery capacity of the species.

Fucoid Macroalgae Have Distinct Physiological Mechanisms to Face Emersion and Submersion Periods in Their Southern Limit of Distribution.

During high tide, macroalgae are submersed, facing adequate environmental conditions, however, at low tide, these species can be exposed to high UV radiation and desiccation, leading to an overproduction of reactive oxygen species, causing oxidative stress. Since intertidal organisms present differential sensitivity to abiotic fluctuations, this study aimed to evaluate the physiological responses [photosynthetic pigments, hydrogen peroxide (H2O2), lipid peroxidation (LP), and thiols and proline] of three macroalgae, from different intertidal levels, towards tidal regimes. Samples of Pelvetia canaliculata, Ascophyllum nodosum, and Fucus serratus were collected from beaches located on the southern limit of distribution in periods of potential stress (Summer and Spring), under low and high tide. The photosynthetic pigments of P. canaliculata and F. serratus were generally higher during low tide, and the oxidative damage evidenced by H2O2 and LP increased in the Summer, while A. nodosum showed greater oxidative damage in the Spring. While thiol content did not change, proline levels were species- and tidal-specific among sampling dates. P. canaliculata presented higher resilience to unfavorable conditions, while F. serratus was the most sensitive species. The physiological responses analyzed were species-specific, pointing to the high susceptibility of low intertidal organisms to expected extreme climatic events.

Sediment Characteristics Determine the Flowering Effort of Zostera noltei Meadows Inhabiting a Human-Dominated Lagoon.

Recent studies have shown increasing Zostera noltei meadows in areas modified by anthropogenic activities. However, it is not entirely clear whether this trend of expansion could be linked to a greater reproductive effort in the species. Anthropogenic stressors can induce the reproductive effort of seagrass meadows as a response to stress, but other variables, such as seagrass biometrics or environmental factors, can also influence their sexual reproduction. To increase the knowledge regarding this issue, we monitored the flowering effort, seagrass biometrics and abiotic parameters of three Z. noltei meadows in an area that has been highly modified by anthropogenic activities during the past decades. Results showed that silt and clay content in the sediment (strongly correlated with organic matter) and seagrass vertical shoot density explained 54% of the variability in the flowering effort of the meadows. This study suggests that stress-induced flowering of Z. noltei may occur under determinate environmental conditions, such as silty environments with organic enrichment.

Spatial-temporal variability of Mytilus galloprovincialis Lamarck 1819 populations and their accumulated sediment in northern Portugal.

Mytilus galloprovincialis is an ecosystem engineer that provides habitat and generates environmental heterogeneity, increasing local biodiversity. Moreover, it is an economically important species representing 14% of the global production of marine bivalves. Natural drivers and the increase of anthropogenic pressures, such as sediment stress, influence its populations on rocky shores. The objective of this study was to explore the spatial-temporal patterns of different M. galloprovincialis attributes along the north of Portugal. For that purpose, six rocky shores were selected and sampled six times along the year 2019. The percentage of cover, density, spat density, condition index, clump thickness, size classes and clump sediment content were considered. Results showed the lack of seasonality in M. galloprovincialis along the north coast of Portugal. However, density, spat stage, clump thickness, condition index and size classes showed some variability among dates and shores. The percentage cover and sediment content only significantly differed among shores. Our results indicated an absence of seasonality for all the studied variables, probably because temperature was always within the optimum range for this species and the abundance of food supply in the study area independently of the season. The accumulated sediment on mussel clumps did not show any temporal variability with only significant differences among shores. The accumulated sediment was composed mainly by medium and coarse sand and it was correlated with mussel average size, condition index, but especially with the mussel clump thickness.

The role of urbanisation in affecting Mytilus galloprovincialis.

Urbanisation is considered as one of the most critical and widespread threats to coastal marine ecosystems. The aim of this study was to compare the density, percentage cover, thickness of clumps, condition index and size-frequency distribution of Mytilus galloprovincialis between urban and non-urban shores, at nested spatial scales, in the Northern Portuguese coast. M. galloprovincialis was selected as model because it is economically and ecologically relevant. Moreover, the relationship between mussel size and the other variables (i.e. density, percentage cover, thickness and condition index) were investigated. Mussels on urban shores showed a smaller density and a greater frequency of larger individuals. A significant negative correlation between mussel length with density and with thickness of clumps was also found. Our results seem to indicate that recruitment has declined on urban shores and, as a result, intraspecific competition is also smaller, leading to more resources being available for a fewer individuals which can reach larger sizes. As mussel beds support a great biodiversity of invertebrates and provide many ecosystem services, urbanisation may have indirect effects on communities associated with mussels. Understanding the vulnerability of mussel beds to urbanisation could inform management.

Batillipes pennaki Marcus, 1946 (Arthrotardigrada: Batillipedidae): deciphering a species complex.

Batillipes pennaki has been considered a common and a cosmopolitan marine tardigrade species. However, the original diagnosis of this species is very incomplete, and consequently there is a high probability of incorrect records. Therefore, a comparative analysis of quantitative and qualitative morphological characters among eight different populations from the Atlantic basin was done in this study to investigate if B. pennaki is a complex of similar species, each with a restricted distribution range. The result of discriminant analyses showed clear morphometric differences between populations that were arranged into three main groups, distinguishing Western Atlantic populations, Eastern Atlantic populations and a Mediterranean population. Furthermore, the result of analyses of morphological structures revealed peculiarities of some traits with taxonomic relevance, such as leg IV sensory organs and primary clavae, consistent with the clusters revealed by quantitative data, allowing us to distinguish three different pseudocryptic species and supporting the hypothesis that B. pennaki is a species complex.

Mollusc diversity associated with the non-indigenous macroalga Asparagopsis armata Harvey, 1855 along the Atlantic coast of the Iberian Peninsula.

The aims of this study were to explore mollusc assemblages associated with the non-indigenous macroalga Asparagopsis armata, to compare them with those on other macroalgae at the study region and to explore potential differences on mollusc assemblages between two regions in the Atlantic coast of the Iberian Peninsula, where A. armata is present. To achieve this, at each region, four intertidal shores were sampled. Twenty-nine mollusc species were reported and thus, A. armata harboured similar or higher diversity than other annual macroalgae in this area. When compared with perennial macroalgae, results depend on the species and studied area. Moreover, significant differences in structure of mollusc assemblages between the two studied regions were found. However, these were due to differences in the relative abundance of species rather than the presence of exclusive species at each region.

Relationship between structure of macrobenthic assemblages and environmental variables in shallow sublittoral soft bottoms.

We establish baseline knowledge of abundance, diversity and multivariate structure of macrobenthos from shallow sublitoral soft bottoms in the North Portuguese coast and elucidate main environmental factors that shape their spatial patterns. In this area distribution of soft bottoms is patchy, surrounded by boulders and rocky substrates. This particular landscape and the lack of significant anthropogenic disturbances are values for the conservation of this habitat. Sediment and physicochemical properties of the water column were studied to provide models for each studied macrobenthic variable. Our models highlighted that most of variation (59%-72%) in macrobenthic spatial patterns was explained by the studied environmental variables. Sedimentary variables were more relevant that those of the water column. Therefore, disturbances affecting sedimentary environment could cause dramatic changes in macrobenthic assemblages because of the limited availability of soft bottoms in the area. In this way, results are useful to adopt right management and conservation strategies.

Two new species of Tardigrada (Eutardigrada: Ramazzottiidae, Macrobiotidae) from the supralittoral zone of the Atlantic Iberian Peninsula rocky shores.

Two new species of Eutardigrada were found in supralittoral lichens, growing on rocky shores at two localities of the Western Atlantic coast of the Iberian Peninsula. Ramazzottius littoreus sp. nov., found in San Cibrao (North of Spain), has the dorsal cuticle sculptured with small tubercles and claws with accessory points similar to R. oberhaeuseri. It can be distinguished from all the other known Ramazzottius species with the same type of cuticular sculpture by the dotted egg shell and the peculiar reticulation visible at the bulbous base of egg processes. Macrobiotus halophilus sp. nov., found in Cascais (Centre of Portugal), belongs to the Macrobiotus hufelandi group. The slightly wrinkled egg shell and egg processes in the shape of inverted chalice with dentate distal disc, identifies it as a member of the Macrobiotus persimilis subgroup. The new dioecious species differs from the six other species of the M. persimilis subgroup by a unique combination of some characters (small and very sparse circular cuticular pores, granulation on legs I-III and dentate lunules on legs IV), by measurements of some structures (claws and buccal apparatus), and by the number, dimension and shape of egg processes.

Consistent patterns of variation in macrobenthic assemblages and environmental variables over multiple spatial scales using taxonomic and functional approaches.

Spatial variability of environmental factors and macrobenthos, using species and functional groups, was examined over the same scales (100s of cm to >100 km) in intertidal sediments of two transitional water systems. The objectives were to test if functional groups were a good species surrogate and explore the relationship between environmental variables and macrobenthos. Environmental variables, diversity and the multivariate assemblage structure showed the highest variability at the scale of 10s of km. However, abundance was more variable at 10s of m. Consistent patterns were achieved using species and functional groups therefore, these may be a good species surrogate. Total carbon, salinity and silt/clay were the strongest correlated with macrobenthic assemblages. Results are valuable for design and interpretation of future monitoring programs including detection of anthropogenic disturbances in transitional systems and propose improvements in environmental variable sampling to refine the assessment of their relationship with biological data across spatial scales.

A new species of heterochelous tanaidacean Tanaissus (Paratanaoidea: Tanaissuidae) from the north-west Iberian Peninsula.

A new species of tanaidomorph, Tanaissus bamberi, is described from the north-western region of the Iberian Peninsula. Its most remarkable character is the presence of morphologically different right and left chelae in the males. The species occurs sympatrically with T. lilljeborgi, mainly in intertidal and subtidal sediments of medium to muddy sands typical of fully marine and estuarine salinities.

Structural complexity of macroalgae influences epifaunal assemblages associated with native and invasive species.

Habitat structure is a primary factor determining the organism distribution. Here, two native and one invasive macroalgal species, apparently different in morphology, were sampled to examine the effects of habitat complexity on the abundance (N), taxon richness (S) and structure of their associated epifaunal assemblages by means of univariate and multivariate techniques. Dry weight and fractal measures were used as proxies of habitat quantity and habitat architecture respectively. Results revealed significant differences in the complexity and in N, S and the structure of epifaunal assemblages among macroalgae and significant correlations between complexity and epifauna. Results suggested that, beside the effect of habitat quantity, the habitat architecture also seems to play a significant role in shaping epifaunal assemblages. Complexity of the studied invasive macroalga significantly differed from that of native species and hosted also different assemblages. Therefore, our findings suggest that invasive macroalgae, if structurally different from native species, induce changes in the associated epifauna.

Effects of subtle pollution at different levels of biological organisation on species-rich assemblages.

We investigated effects of subtle nutrient enrichment and metal pollution on different levels of biological organization (i.e. whole assemblage, population and individual) of species-rich assemblages. We used rockpools as model system, applying a multi-factorial sampling design to test hypotheses on differences between disturbed and reference locations. Results indicated that disturbed and reference locations supported similar assemblages, as well as individual fitness-related life-traits were ineffective to discriminate between the two conditions. In contrast, assemblages responded to pollution through a reduction of the abundance of sensitive species and a proliferation of tolerant species, although these alterations were detectable only once the influence of dominant taxa was down-weighed by data transformation. Present findings suggest that, contrarily to individual level variables, assemblage structure after data transformation and patterns of distribution and abundance of differently sensitive taxa would be a powerful tool to detect effects of subtle pollution on species-rich assemblages.

Fucus spiralis as monitoring tool of metal contamination in the northwest coast of Portugal under the European Water Framework Directives.

Metals (Cd, Cr, Cu, Fe, Mn and Zn) in coastal seawaters and soft tissues of macroalga Fucus spiralis from the northwest coast of Portugal were determined to assess spatial variations of metal bioavailabilities and bioaccumulation factors to compare different ecological quality classifications. Both coastal seawaters and soft tissues of F. spiralis showed significant spatial variations in their metal concentrations along the coast. The macroalgae F. spiralis accumulated more efficiently Cd, Mn and Zn and showed low bioaccumulation factors to Cr, Cu and Fe. Regarding the metal guidelines of the Norwegian Pollution Control Authority, the entire northwest (NW) coast of Portugal in April 2013 should be classified as 'class I--unpolluted' for all metals, except in Ave for Cu ('class II--moderately polluted') and Cavado for Cd and Cu ('class II-moderately polluted'), revealing the low metal bioavailabilities of these seawaters. As there were always significant positive correlations between all metals in seawaters and F. spiralis, this macroalga species was considered a suitable monitoring tool of metal contamination in the NW coast of Portugal and a useful aquatic organism to be included in the European Environmental Specimen Banks in order to establish a real-time environmental monitoring network under the European Water Framework Directives.

Shifts from native to non-indigenous mussels: enhanced habitat complexity and its effects on faunal assemblages.

Ecosystem engineers such as mussels may affect strongly both the structure of benthic assemblages and the ecosystem functioning. The black-pygmy mussel Limnoperna securis is an invasive species that is spreading along the Galician coast (NW Spain). Its current distribution overlaps with the distribution of the commercial native mussel species Mytilus galloprovincialis, but only in the inner part of two southern Galician rias. Here, we analysed the assemblages associated with clumps of the two mussel species and evaluated if the invasive species increased complexity of habitat. To measure complexity of clumps we used a new method modified from the "chain and tape" method. Results showed that the identity of the mussel influenced macrofaunal assemblages, but not meiofauna. L. securis increased the complexity of clumps, and such complexity explained a high percentage of variability of macrofauna. The shift in dominance from M. galloprovincialis to L. securis may alter habitat structure and complexity, affecting the macrofaunal assemblages with unpredictable consequences on trophic web relations.