Perfectly circular patches bare of vegetation in otherwise continuous swards of seagrass, and perfect circles of seagrass with lush fringes of shoots on the outer margins but with virtually bare centres, have both attracted popular attention as ‘fairy circles’ or ‘fairy rings’ in view of the folklore surrounding the supernatural origins of their terrestrial fungal counterparts. Aerial photographic and satellite surveys show that, on the Isles of Scilly, circles of Zostera marina of the second type occur sporadically, with exceptionally prolific clusters in specific localities associated with the colonization of bare substratum after disturbance, gradually disappearing over the period of this study at one site and appearing at another. Their abundance is the highest recorded anywhere in the world. Early suggestions that they represent seaweed growth on the stones of ancient hut-circles, submerged for centuries as a result of sea-level rise, are refuted. It is argued that they result from the unrestricted clonal growth of genets arising from individual Zostera seedlings, expanding equally in two dimensions and colonizing vacant habitat, with the older central shoots senescing and dying. Diameters of the circles constitute a stepwise increase in size, and the growth increments may represent a similar rate of seasonal growth in consecutive years, implying a linear rhizome growth rate of ~2.5 m year−1, which would be exceptional for Zostera marina, but which is supported by an observation on circles exposed on a low spring tide and would be an evolutionary adaptation for rapid recolonization in such a physically disturbed environment.

The recruitment of the endangered limpet Patella ferruginea in the Chafarinas Islands (SW Mediterranean) was studied over a 17-year period (1999‒2015). A total of 8115 recruits <20 mm in maximum diameter were counted in 95 transect censuses sampled during the study period. The presence of recruits began at the end of winter or beginning of spring (March‒April), when they reached a maximum shell diameter (MD) of at least 4 mm, with a peak in abundance occurring in spring. Smaller recruits were found on the lower midlittoral on the fringe of the vermetid gastropod Dendropoma lebeche and the crustose coralline algae Neogoniolithon brassica-florida, which suggests that settlement occurs at this shore level. Recruits reach 12‒27 mm at the end of their first year of life. A regular recruitment was detected for all studied years, with an average of 11.71 recruits m−1 across the study period. However, recruitment exhibited high interannual variability and did not occur evenly along the coastline of the islands. Higher recruitment was observed in 2001, 2011 and 2012, with a maximum density of 69.07 recruits m−1 in one transect in 2012. The density of recruits decreased in summer. No significant correlation was found between the density of recruits and adults. Between 1999‒2010, 29.29% of recruits were ‘phoretic’ on the shell of adults (1.81 recruits per host on average). Recruits climbed on to adults sometime after settlement, thus we suggest that ‘phoresy’ could favour the survival of young limpets instead of being due to selective settlement on adults. To improve and standardize recruitment monitoring in future studies, we propose that recruits are considered as those specimens <20 mm in MD and that recruitment censuses are carried out in spring, with additional censuses after summer to detect juvenile mortality. Additionally, we propose that 1 mm interval size classes are used for growth studies based on size‒frequency analyses.

The pleustonic siphonophore Physalia physalis (Linnaeus, 1758) reported in the present study were collected in May 2018 on the north-western coast of Algeria. Two specimens of P. physalis have been observed, photographed and measured for the first time on the Al-Wardania beach, in Aïn Temouchent city. Their size is between 34.8 and 42 cm total length (TL). Morphometrics, meristics and diagnostic characteristics of the species are presented.

One shark was landed at the Naval Base Pasha Liman, Bay of Vlore, Albania, the Adriatic Sea. Photographic records only enabled the specimen to be placed in family Odontaspididae or Carchariidae. Later examination of the preserved head, dry jaw and dentition identified the specimen as Odontaspis ferox. This is a rare record and the northernmost Mediterranean observation of this species, and the first Adriatic record for several decades.

Antagonism among bacteria is widespread and plays an important role in structuring communities. Inhibitory compounds can confer competitive advantage, but energetic trade-offs can result in non-transitive (i.e. ‘rock-paper-scissors’) interactions, ultimately allowing co-existence and community stability. Competition in sedimentary habitats is especially keen given high densities and attachment to inorganic particles. Because measuring trade-offs between bacterial species is challenging, much of our understanding of competitive interactions is based on theoretical modelling and simplified in vitro experiments. Our objectives were to determine (1) if interference competition occurs in microcosms mimicking in situ conditions; (2) whether the presence of sediment influences antagonistic interactions; and (3) if more complex assemblages alleviate or synergize interactions. Four sedimentary isolates, including antibiotic-producing, resistant and susceptible strains were incubated in porewater microcosms in 1-, 2- and 3-species combinations, both with and without natural sediments. Microcosms were sampled over 72 h to generate growth curves using quantitative PCR. Multiple growth attributes (growth rate, maximum density, lag time) were used to assess effects of treatment (species combinations) and environment (sediment vs porewater alone). Antimicrobial producers were more effective at inhibiting target species in microcosms that included sediment, in agreement with theory. We observed growth inhibition by antimicrobial-producing bacteria in both 2- and 3-species microcosms. However, the expected protection of sensitive bacterial strains by resistant strains was observed in only one (of four) 3-species combinations, thus the ‘rock-paper-scissors’ prediction was not fully supported. These results reinforce the notion that interspecies interactions are context-dependent, reliant on environmental conditions and the species involved.

This report provides the first confirmed identifications of wahoo (Acanthocybium solandri) and striped marlin (Kajikia audax) in the Red Sea, expanding the known ranges of these species into the basin. Potential mechanisms responsible for the lack of regional documentation of the two species are further discussed. These findings illustrate the need for systematic biodiversity surveys of pelagic fish assemblages in the Red Sea.

Microphytobenthos (MPB) communities are responsible for most primary production in shallow intertidal mudflats. The effects of short-term changes in temperature and light (1200, 500 and 0 μmol photons m−2 s−1) on the photosynthetic activity of intertidal MPB communities of Browns River, Tasmania, during winter (0, 5, 10 and 15°C) and summer (20, 25, 30, 35 and 40°C) were examined using a Pulse Amplitude Modulated (Water PAM) fluorometer. The MPB communities were primarily dominated by the diatom genera Navicula, Cocconeis and Amphora, with a difference in species dominance during seasons. During summer, Amphora coffeaeformis dominated communities were significantly impacted by temperatures above 30°C regardless of light intensities. The MPB was able to photosynthesize at temperatures only up to 25°C. The rETRmax at 25°C, ranged from 39.18 ± 3.42 (500 μmol photons m−2 s−1) to 22.83 ± 1.05 (0 μmol photons m−2 s−1), which was lower than the values recorded at an equivalent irradiance in in-situ summer. However, if ambient temperature exceeds 25°C in summer, it is likely that the photosynthetic capabilities of the MPB will be diminished and it will cause irreversible photoinhibition.

The study compares the isotopic niche (δ13C–δ15N) of three species of penaeid shrimps (Xiphopenaeus kroyeri, Artemesia longinaris and Litopenaeus schmitti) that are targets of fishing in south-eastern Brazil. The two hypotheses raised are based on the niche theory, in which the coexistence between organisms that have similar dietary demands is possible due to trophic partitioning: (i) shrimp species that share the habitat have segregated isotopic niches; and (ii) stages of maturity and genders vary with the trophic habitat (δ13C) and/or trophic position (δ15N). In multispecific fishing grounds, the isotopic niches of the shrimp species were segregated or had low overlap, indicating trophic partitioning. The intraspecific comparison of δ13C and δ15N showed a similar trend in all species. For δ13C, the values were more enriched in adult individuals than in juveniles, but similar between males and females. For δ15N, adult individuals also had more enriched values, and males were more enriched than females. The results confirm the hypotheses raised, and the assumptions of niche theory apply to these penaeid shrimps.

Marine ectotherms have evolved a range of physiological strategies to cope with temperature changes that persist across generations. For example, metabolic rates are expected to increase following an acute exposure to temperature, with potential detrimental impacts for fitness. However, they may be downregulated in the following generation if offspring experience the thermal conditions of their parents, with a resulting decrease in maintenance costs and fitness maximization. Yet, trans-generational studies on metabolic rates are few in marine ectotherms, thus limiting our ability to accurately predict longer-term implications of ocean warming on organisms' performance, metabolic rates being the fundamental pacemaker for all biological processes. This is particularly true for small-size organisms, for which the determination of individual metabolic rates has been historically challenging, and for many groups of marine invertebrates, such as annelids, which are under-represented in physiological investigations. Here, we exposed the subtidal annelid Ophryotrocha labronica (body length: ~4 mm) to a thermal gradient (21, 24, 26, 29°C) and measured, for the first time in this species, the temperature dependence of metabolic rates across two generations. We found that metabolic rates were positively related to temperature, but this relationship did not differ between generations. Our study provides additional evidence for the diversity of temperature-associated physiological responses of marine ectotherms and offers a number of methodological recommendations for unveiling the mechanisms underpinning the observed trans-generational responses of metabolic rates in marine annelid species.

The present study described the gametogenesis and assessed the pattern of energy storage throughout the reproductive cycle of the golden carpet shell (Polititapes aureus) from the Ria Formosa lagoon (southern Portugal). Monthly sampling was performed for two years (March 2016–February 2018) and the study was based on gonad histology, complemented by the estimation of the mean gonadal index, body condition index and biochemical composition. The species’ reproductive cycle presented a seasonal pattern, with a resting period mainly between October and January and gametogenesis beginning around February–March. The spawning season of P. aureus was shorter in 2016 (June–September) than in 2017 (May–October). Furthermore, ripe individuals were very scarce (1.3%) in 2017 compared with the previous year (11.4%). Mean gonadal index (GI) reflected the species’ reproductive cycle and the body condition index (CI) and biochemical composition of the individuals exhibited high variation between years. Regarding the biochemical composition, proteins ranged between 190.6 and 595.2 μg mg−1, glycogen from 5.7 to 102.6 μg mg−1 and total lipids between 31.6 and 80.7 μg mg−1. The reproduction of P. aureus was strongly influenced by fluctuations in both seawater temperature and chlorophyll a, as reflected through the temporal variation in the gonadal cycle, condition index and biochemical composition. Overall, the information gathered in this study is valuable to propose scientifically based harvesting management measures for the long-term sustainable exploitation of this shellfish resource, further reinforcing the importance of implementing adaptive fishery management strategies to cope with global climate change.

Otoliths are an excellent tool in studies on ecological connectivity of fish species populations. Opsanus beta is an invasive species introduced on the Brazilian coast, but not native from the Gulf of Mexico. The present study aimed to compare the otolith contours of specimens collected in Mexico (Celestún, CEL) and in two Brazilian estuaries (Santos Bay, STB, and Paranaguá Estuarine Complex, PEC). In the laboratory, 99 otoliths were extracted, photographed and compared using wavelet analysis. The otolith contours varied between sites (39 from CEL, 26 from STB and 34 from PEC). The linear discriminant analysis correctly reclassified 87.9% of otoliths by sites, with the best reclassifications in the CEL (97.36%), followed by PEC (88.23%) and SBT (73.07%). MANOVA showed significant differences in otolith contours between sites (F = 5.37; P < 0.005). The otolith contour from CEL was significantly different from those from the PEC and SBT. However, the otolith contour of the two Brazilian estuaries did not significantly differ among them (MANOVA, P > 0.005). Our results indicate O. beta populations on the Brazilian coast are connected, and probably isolated from the Mexican population.

Deep-water shrimps are recognized as non-conventional culinary delicacies owing to the presence of high-quality polyunsaturated fatty acids, even though they remain one of the predominantly unexplored marine fishery resources. In this study, variation of fatty acid profiles of Aristeus alcocki, Solenocera choprai, Heterocarpus chani and Plesionika quasigrandis, caught along the south-west coast of India (Arabian Sea) during the months spanning from September 2018–April 2019, were compared. Among the deep-water shrimps studied, A. alcocki contained a greater amount of n-3 fatty acids, such as docosahexaenoic and eicosapentaenoic acid along with optimal n-3/n-6 polyunsaturated fatty acid ratios beneficial for human nutrition (up to 8 during the winter months) when compared with other shrimps. In general, fatty acid concentrations exhibited variations, particularly with regard to polyunsaturated fatty acids, such as eicosapentaenoic acid and docosahexaenoic acid. These n-3 fatty acids were predominant during December–February of the studied year, but concentrations were noticeably lower during March and April. Females had considerably higher (P < 0.05) C20–22 n-3 fatty acid concentrations along with nutritionally balanced polyunsaturated/saturated fatty acid ratio than males. Results of the two-way multivariate analysis of variance (MANOVA) revealed statistically significant differences in the fatty acid profiles between the species and months. The interaction effects of months with species were also highly significant (Wilk's lambda = 0.000001; F = 187.7, P < 0.0001). Lesser atherogenicity (<3) and thrombogenicity (<0.5) indices coupled with considerably greater n-3/n-6 fatty acid ratios recognized these deep-water species as a possible source of highly nutritional human food.

New in situ records of the sublittoral sea anemone Oulactis coliumensis (Riemann-Zürneck & Gallardo, 1990) are provided from different localities of northern Chile and Peru. Specimens were generally observed buried in shallow soft bottoms (3–25 m depth), near port cities and in areas with a high organic load. This is the first report of the species outside its type locality (off the Bay of Coliumo, Chile; ~36°S), extending its range of distribution to lower latitudes.

The spiny butterfly ray Gymnura altavela (Linnaeus 1758) is classified as Endangered by the International Union for Nature Conservation (IUCN) and considered Critically Endangered in the Mediterranean Sea and South-west Atlantic. Despite its status, few studies on the population biology and genetics for the species are available, undermining conservation efforts. In the present study, we evaluated the taxonomic status of Gymnura altavela along both sides of the Atlantic using COI sequences. Our genetic data support the existence of two genetically differentiated G. altavela lineages (West and East Atlantic) and further studies are required to evaluate the hypothesis that these lineages could, in fact, be cryptic species within this endangered batoid's genus.

Scomberomorus koreanus was originally described from a single specimen from the west coast of Korea. In 1964 the species was synonymized with S. guttatus during the systematic review of the scombroid fishes of India. Subsequently, S. koreanus was discovered in Palk Bay in 1976, confirming its first record from India and the Indian Ocean. Since then, no such detailed taxonomic studies have been undertaken for the species along the Indian coast. Although the species is distributed in the Indo-West Pacific region and forms a commercially important fishery in part of its range, S. koreanus is poorly known and very limited taxonomic studies have been carried out in detail which usually results in misidentifications at field level. The present morpho-genetic investigation and previous molecular study by the authors confirmed the occurrence of the species in the coastal waters of both the Bay of Bengal and the Arabian Sea. The exact characteristics of S. koreanus are detailed here, and their comparison was made here with the related species S. guttatus found in the northern part of the east coast of India, based on a thorough morphological study, including the radiographs of 13 fresh specimens (334–588 mm FL), colour photographs of S. koreanus collected in 2019–2021 and DNA barcoding.

Since 2017, a sea anemone species has been registered in central Portugal with a morphology comparable to Phymactis papillosa, from the Pacific shore of south and central America. In this paper, we have collected two individuals from Cascais, Portugal, extracted their DNA and amplified and sequenced the internal transcribed spacers I and II, markers frequently used in Cnidaria barcoding. The sequences obtained were compared with the ones available on GenBank, using the Basic Local Alignment Search Tool (BLAST) on the NCBI website. This procedure allowed the identification of P. papillosa. This is the first confirmed record of P. papillosa in European coasts. Citizen science data suggest occurrences in the Alentejo coast (south-west Portugal) and Mediterranean coast around Murcia, although no genetic or morphological confirmations of these records have been made. The potential effects of this species introduction are discussed.

The New York Bight is undergoing rapid anthropogenic change amidst an apparent increase in baleen whale sightings. Though survey efforts have increased in recent years, the lack of published knowledge on baleen whale occurrence prior to these efforts impedes effective assessments of distributional or behavioural shifts due to increasing human activities. Here we synthesize opportunistic sightings of baleen whales from 1998–2017, which represent the majority of sightings data prior to recent survey efforts, and which are largely unpublished. Humpback and fin whales were the most commonly sighted species, followed by North Atlantic right whales and North Atlantic minke whales. Important behaviours such as feeding and nursing were observed, and most species (including North Atlantic right whales) were seen during all seasons. Baleen whales overlapped with multiple anthropogenic use areas, and all species, but of particular importance North Atlantic right whales, were sighted outside the spatial and temporal bounds of the Seasonal Management Areas for North Atlantic right whales. These opportunistic data are vital for providing a baseline and context of baleen whales in the New York Bight prior to broad-scale efforts and facilitate interpretation of current and future observations and trends, which can more accurately inform effective management and mitigation efforts.

The paper describes the first report of Kandelia candel (Rhizophoraceae), a rare mangrove from Bhavanapadu, a coastal village in Srikakulam district in Andhra Pradesh, India. This species is relatively less abundant along the east coast of India. During our study covering all the 41 mangrove patches in the state of Andhra Pradesh, 16 mangrove species were observed throughout the state and the Kandelia candel was seen only in Bhavanapadu (patch 2). The plant sighted was identified using taxonomic keys and confirmed using DNA barcoding. The identified specimen is deposited in the museum repository at ICAR-Central Marine Fisheries Research Institute (CMFRI), Kochi (accession no. MB.1.1.1.1) and its gene sequence is deposited in National Center for Biotechnological Information (NCBI) (accession no. MH243746). Patch 2 where K. candel was observed is separated away from the other clusters in the principal component one, with the patch showing an average dissimilarity of about 71.79% from the other patches. K. candel is a mangrove highly sensitive to changes in salinity. The presence of a lone member of a rare species in the state at the sampling location raises questions on its endurance in the region. The study underlines the relevance of monitoring the mangroves and advocate adequate conservation measures for proper protection, proliferation and management of this globally dwindling resource.