Distinctive morphological characteristics of Fucus guiryi (Fucales, Phaeophyceae) from Canary Islands, subtropical eastern Atlantic Ocean

The brown macroalgae in the order Fucales include foundation species on rocky habitats of temperate regions. This work focused on Fucus guiryi, a recently described species segregated from F. spiralis in a molecular basis. It inhabits the upper intertidal zone from the eastern North Atlantic to the subtropical Canary Islands, where is considered its southern limit. We examined morphology and anatomy of vegetative and reproductive structures of F. guiryi from the Canary Islands. Several distinctive characteristics in habit existed between F. guiryi and other species of the genus distributed northwards, such as length and width of stipe and branches, number of branches, and morphology and number of receptacles. Anatomical features reported here for the first time exhibited subtle differences with temperate F. vesiculosus, F. spiralis and F. serratus. The morphology and arrangement of medulla, cortex and meristoderm were also distinctive for F. guiryi. Mucilage in cellular interstitial spaces constitutes good evidence that explains the presence of F. guiryi at its warmest distribution limit in the Canary Islands.

Genome Size Dynamics in Marine Ribbon Worms (Nemertea, Spiralia)

Nemertea is a phylum consisting of 1300 mostly marine species. Nemertea is distinguished by an eversible muscular proboscis, and most of the species are venomous. Genomic resources for this phylum are scarce despite their value in understanding biodiversity. Here, we present genome size estimates of Nemertea based on flow cytometry and their relationship to different morphological and developmental traits. Ancestral genome size estimations were done across the nemertean phylogeny. The results increase the available genome size estimates for Nemertea three-fold. Our analyses show that Nemertea has a narrow genome size range (0.43–3.89 pg) compared to other phyla in Lophotrochozoa. A relationship between genome size and evolutionary rate, developmental modes, and habitat was found. Trait analyses show that the highest evolutionary rate of genome size is found in upper intertidal, viviparous species with direct development. Despite previous findings, body size in nemerteans was not correlated with genome size. A relatively small genome (1.18 pg) is assumed for the most recent common ancestor of all extant nemerteans. The results provide an important basis for future studies in nemertean genomics, which will be instrumental to understanding the evolution of this enigmatic and often neglected phylum.

Diversity and Distribution of Molluscs in the Intertidal Zone of Nglambor Beach, Gunung Kidul, Yogyakarta

The intertidal zone is the area between the highest and lowest tides, which represents the transition from ocean conditions to land conditions. This study aimed to determine the diversity and distribution of mollusks that exist along the intertidal zone of Nglambor Beach, between August and November 2020. Observations of all molluscs were carried out at two random stations using 10 plots measuring 1 x 1 m 2 with 5 meters. A total of two classes of Mollusca (Gastropod and Bivalvia) belonging to twelve families and 19 species were found from upper to lower an intertidal zone. The upper intertidal zone was recorded to have the highest diversity and an evenness index (Shannon-Wiener diversity index: H ’= 2.524 and Pielou evenness index: J’ = 0.932) compared to the middle and lower zones. It can be concluding that the diversity index in the study location is categorized as medium and its evenness is high. Thais hippocastanum is the most dominant species found in the upper and middle zones, while Thais tissoti dominates in the lower zone. This research contributed to a preliminary checklist on molluscs, which will support a baseline study on the intertidal in future.

Discovery of Wilsonosiphonia fujiae (Rhodomelaceae, Rhodophyta) from the Maldives Islands and transfer of Polysiphonia rhizoidea from Hawaiʻi to Wilsonosiphonia

Wilsonosiphonia is a newly described marine algal genus with three species. The genus was previously confused with the widely distributed taxon Polysiphonia, and because of this, the taxonomy and distribution of Wilsonosiphonia is likely underestimated. We report the discovery of a minute filamentous red alga, Wilsonosiphonia fujiae (Rhodophyta) in the Maldives Islands, a taxon which was considered endemic to Brazil. Specimens were collected at Fulhadoo, Goidhoo Atoll and Dhidhdhoo Islands, South Ari Atoll, which are ca. 160 km apart, during January and July, 2019, respectively. Thalli formed dense patches on the upper intertidal in regions of shaded rock. Both mitochondrial cox1 and plastid rbcL sequencing confirmed the occurrence of W. fujiae in the Maldives, which is also in agreement with morphological observations. Based on the low pairwise divergences of COI-5P and rbcL sequences between the Maldives and Brazil specimens, we suggest that W. fujiae is a recently introduced yet cryptogenic species in the Maldives. Additionally, as a result of our phylogenetic analyses, it became evident that sequences from the Hawaiian Islands, which were listed as members of the genus Polysiphonia, represent species-level diversity within the genus Wilsonosiphonia. Based on both morphological characteristics and the COI-5P phylogeny, we here reinstate Polysiphonia rhizoidea from Hawaiʻi and transfer it to Wilsonosiphonia, as W. rhizoidea comb. nov.

Life cycles of the rhizocephalan Boschmaella japonica Deichmann & Høeg, 1990 (Cirripedia: Chthamalophilidae) and its host barnacle Chthamalus challengeri Hoek, 1883 (Cirripedia: Chthamalidae)

Although parasitic castration is widespread among rhizocephalan barnacles, Boschmaella japonica Deichmann & Høeg, 1990 does not completely sterilise the host barnacle Chthamalus challengeri Hoek, 1883. As little information is available on the relationships with the host in “barnacle-infesting parasitic barnacles” (family Chthamalophilidae), we studied the life cycles of both B. japonica and C. challengeri and the effects of the parasite on the host reproduction. Specimens of C. challengeri were collected from an upper intertidal shore at Shirahama, Wakayama, western Japan from April 2017 to September 2018 at 1–3 mo intervals. We recorded the body size, number of eggs, egg volume, and the presence of the parasite for each host. Moreover, settlement and growth of C. challengeri were followed in two fixed quadrats. Chthamalus challengeri brooded from February to June. The prevalence of B. japonica was high (often exceeded 10%) from April to July, and was rarely observed from September to next spring. The life cycle of the parasite matched well with that of the host. The parasite reduced the host’s brooding rate and brood size, to the extent that no hosts brooded in 2018.

Longshore variation in coastal foredune growth on a megatidal beach from UAV measurements

<p>Coastal dunes are both a vital natural coastal defence and a key ecological habitat; therefore, understanding their evolution is important to inform coastal management. Megatidal environments are the world largest tidal ranges and hence provide a unique endmember of the tidal range continuum. A study site at Crymlyn Burrows, Swansea Bay, UK is monitored here; the area was originally of applied interest due to its identification as a key receptor of the Swansea Bay Tidal Lagoon project. The study site comprises of 2km of dune frontage bounded to the west by hard sea defences and to the east by the River Neath estuary. The intertidal is characterized by a shallow slope and crescentic intertidal bars. Mean spring tidal range at the nearby Mumbles tide gauge is 8.46m; mean wave heights at a wave buoy offshore of the site (depth 9m LAT) are 0.66m and storm wave heights exceed 3m; predominant wind direction is in an alongshore – onshore direction.</p><p>A Sensefly Ebee-RTK drone with a Sony RGB camera has been used to map the dune system and the mid to upper intertidal beach on a monthly – bimonthly frequency since October 2018. Initial post-processing was conducted in the Sensefly Emotion3 software; Pix4D was then used to generate a point cloud from the georeferenced images. RTK-GPS surveyed ground control points distributed over the study area were used to improve the accuracy of the solution. Point clouds were cleaned to remove noise using Cloud Compare, an open source point cloud editor, before being interpolated onto a gridded surface. Comparison of the gridded surface against RTK-GPS surveyed points gave a vertical mean absolute error (MAE) of 0.05m over the beach area. Comparison in the dune area is more complex since the raw point cloud includes the vegetation and hence over-estimates height compared to the bare earth. Based on the raw point cloud, MAE over the dune area was 0.22m; however, when vegetation points were removed using artificial neural network based colour discrimination, the MAE was 0.05m.</p><p>Longshore variation in dune evolution is clearly evident. At the eastern and western ends of the dune system, dune progradation can be observed whereas in the central portion the frontal dune is cliffed and the dune foot position is static or eroding landward. Pressure transducers have been deployed in a longshore array at the neap high tide level to assess variation in wave energy reaching the upper intertidal over the study area.</p><p>This presentation will explore whether this variation in behavior is due to longshore variation in wave energy (erosion potential), variation in sediment availability (accretion potential) or the persistence of antecedent morphology.</p>

The sabkhas of Qatar: modern analogues for studying early life on Earth and on Mars

<p>The study of early life on Earth and the search for life on Mars often includes investigations of modern analogues: natural environments that share similarities to what we hypothesize may have existed on the early Earth and early Mars. The study of modern analogues provides key information on how biosignatures are formed and preserved, which is essential for interpreting the geological record. Research conducted in recent years in various modern sabkhas located along the coast of Qatar have demonstrated that these extreme evaporitic environments represent an inspirational gold mine for the field of geobiology and astrobiology.</p><p>The intertidal zones of the Qatari sabkhas are typically colonized by microbial mats. Their presence leads to the formation of Microbially Influenced Sedimentary Structures (MISS). Examples of studied MISS include polygonal, domical, blistered, tufted and crinkled microbial mats. We discuss biological vs. physiochemical factors responsible for their formation, as well as their fossilization potential. These MISS often occur in a precise sequence along a transect from the lower to the upper intertidal zone. We propose that a MISS sequence represents a stronger morphological biosignature than a single MISS. The community composition of some of the studied mats revealed an uppermost layer dominated by anoxygenic phototrophs. We propose that such mats represent a particularly good analogue for studying life in the Early Archean, a time when the cyanobacteria that usually dominate the uppermost photo-oxic layer of most modern mats probably did not exist.</p><p>Besides influencing sediment morphology, the extracellular polymeric substances (EPS) constituting the mats serve as nucleation sites for the precipitation of authigenic minerals. Among these possible precipitates, our research focused on microbially influenced Mg-rich carbonates and Mg-rich silicates. Linking these minerals to a microbial process is of particular interest in view of the forthcoming rover missions to Mars (i.e., ExoMars and Mars 2020). Indeed, orbital spectral analyses revealed the presence of Mg-rich clays and Mg-rich carbonates in the surroundings of the proposed landing sites. It will be exciting to test the hypothesis that, on Mars, some of these minerals may have formed at low temperatures from liquid water and may, therefore, represent a target phase for the investigation of biosignatures.</p>

Linking decay of microbial mats and dolomite formation in the sabkhas of Qatar

<p>The sabkhas of Qatar are excellent environments to examine the mechanisms of low-temperature dolomite precipitation. The detailed microbial and geochemical analysis of the dynamics in environmental conditions in two microbial mats over two years provide a unique opportunity to gain insights in low-temperature dolomite formation in modern time. The compositions of extracted exopolymeric substances (EPS)  in two microbial mats, one within the lower intertidal zone and one within the upper intertidal zone exhibit an increase in the concentration of carboxylic functional groups during periods of elevated salinity. We interpret it as an indicator for dolomite formation since carboxylic functional groups are suggested to be the primary drivers for low-temperature dolomite as nucleation sites and inhibitors of Mg complexes. Notably, the increase in the concentration of the carboxylic group is associated with an increase in salinity in sabkha which happened periodically.</p><p>These fluctuations have been accompanied by the changes in the community from cyanobacterial dominated mat to one dominated by heterotrophs. During these periodical events, when a growing microbial mat turned into degrading microbial mat, we observed low-temperature dolomite formation. Such events occur in other modern dolomite forming environments and possibly in ancient sequences. Our work observed dynamical changes both in microbial mats, exopolymeric substances composition, geochemical gradients and accompanied low-temperature dolomite formation over several seasons. Our findings proving evidence that EPS degradation within microbial mats is a key mechanism in the formation of modern and most probable, ancient low-temperature dolomite with implications for those formed in ancient sequences.</p>

Differential responses to salt concentrations of lichen photobiont strains isolated from lichens occurring in different littoral zones

An interesting biota of lichen-forming fungi occurs along rocky seashores of cold and warm-temperate regions in both hemispheres. Most of the species belong to the family Verrucariaceae and form symbioses with an extraordinarily diverse group of photobionts. We isolated the photobionts of three species: Hydropunctaria maura and H. amphibia from the supralittoral zone, and Wahlenbergiella striatula from the upper intertidal zone. We characterized the isolated strains structurally by means of transmission electron microscopy, and molecularly using the nrSSU and nrITS and chloroplast RPL10A regions. Additionally, we studied the response of the strains to different salt concentrations, analyzed the concentration of osmoregulatory solutes, and measured photosynthesis performance by chlorophyll fluorescence and CO2 assimilation techniques. All strains belong to the recently described species Halofilum ramosum, although we found differences in the ITS and RPL10A regions among the strains shared by H. maura and H. amphibia and the strain isolated from W. striatula. Differences were also found in the main osmoregulatory response of the strains growing under high salt concentrations: W. striatula accumulated glycerol, while H. maura and H. amphibia synthetized sucrose. Analyses of photosynthesis performance also indicated differences in physiological behavior between supralittoral-dwelling and intertidal-dwelling species, W. striatula showing lower photosynthetic activity under high irradiance. Our results highlight the role of photobionts in determining lichen zonation on rocky seashores.