Distribution Of Seaweeds Research Articles

Ecological responses of macroalgae vegetation to seasonal variations and environmental changes in the Suez Canal District

The noticeable lack in macroalgae number and their vegetation composition in the Suez Canal district may refer to the importance of studying and following the temporal and spatial patterns that are in change in space and time. Therefore, we have to follow regular biodiversity monitoring to elucidate the changes to seaweed vegetation in the Suez Canal area that might occur as seasonal variations or anthropogenic impacts. The present study extended from summer 2020 to spring 2021 along the Suez Canal district, including eight sites at Port Said on the Mediterranean Sea, Timsah Lake in Ismailia and Suez Bay in the Red Sea. Distribution of seaweeds is usually affected by environmental factors as temperature, salinity, pH, and water chemistry. Most of the chemical parameters recorded very high concentrations (high significant) at the sites in the Suez Bay area during all seasons, excluding nitrogen and phosphorus, which were elevated recordings in the Port Said area. El-Timsah Lake area recorded an increase in salinity which was considered as a brackish stratification type. The taxonomic groups of the recorded species showed a total of 39 macroalgal taxa (20 Chlorophyta, 16 Rhodophyta and 3 Phaeophyta). Port Said area recorded the highest significant number of Chlorophyta and Rhodophyta communities. The relative abundance of macroalgal divisions was Chlorophyta, which formed the main coverage. Enteromorpha-Ulva community was characterized during all the study seasons. Multivariate analysis showed the great relation between seaweed distribution, physicochemical parameters and seasonal variations.

Close but distant: Emersion promotes ecophysiological differentiation between two rhodophytes within an estuarine intertidal zone

Environmental factors associated with emersion determine, among others, the spatial distribution of intertidal seaweeds. This study investigates the emersion tolerance of Bostrychia scorpioides and Catenella caespitosa, in relation to their zonation pattern in a soft-bottom intertidal zone. The two species are vertically segregated, B. scorpioides occupying the uppermost horizon and C. caespitosa the lowest one, but they coexist at intermediate tidal parts. Three sets of laboratory-controlled experiments were carried out at ecologically meaningful conditions to achieve the following specific objectives: 1) to identify differences in their water loss and retention; 2) to assess the interactive effect of emersion and temperature (E × T) and emersion and salinity (E × S) on their growth, % DW and elemental composition; 3) to analyse the effect of short-term (3 h) and mid-term (1–6 d) desiccation periods on their photosynthetic performance and its recovery following reimmersion. Our main findings demonstrated that combination of high levels of emersion and temperature (8 h · d−1, 25 °C) had a synergistic negative effect on the growth of both species leading to growth imbalance, especially in C. caespitosa, the lowermost intertidal species. Both species could grow under continuous emersion if thalli do not completely dehydrate, but only B. scorpioides maintained similar growth rate and C:N ratio as under continuous submersion, evidencing its higher emersion tolerance. In contrast, the combination of emersion and salinity had an antagonistic outcome, since the influence of salinity decreased as daily emersion period increased. After 3 d of continuous air exposure, both species recuperated 50% of their net photosynthetic rate at saturating irradiance, but after 6 d B. scorpioides was able to photosynthetically recover to a greater extent than C. caespitosa (20% vs. 8% recovery), showing a better physiological performance of recovery following reimmersion. We demonstrated that the uppermost growing species (B. scorpioides) possessed higher emersion tolerance and recovery abilities of physiological performance following reimmersion. The different effect of emersion on species growth and mid-term abilities to recover their physiological fitness clearly supported the observed zonation pattern.

Seaweeds of South Andaman: diversity, distribution, biochemical characterization and fatty acid profiling of some selected species

ABSTRACT The huge rise in seaweed-derived bioactive compounds demands immediate attention of under-explored seaweed species. The oceanic bio-resources in the tidal stretch of the Andaman Islands are relatively unknown. The present study explores seven intertidal regions of South Andaman Island to understand the species richness and existing seaweed biomass. Biochemical and fatty acid components were assessed for 15 seaweed species, commonly available in the study sites. A total of 67 species of seaweeds were collected during a one-year survey, most of which belonged to Chlorophyta, Rhodophyta and a few in Phaeophyta. The species richness was higher in sandy and coarse substrata, while highest species density was found on rocky shores. The P value for species richness at 5.05E-15 also validated the variation in seaweed distribution and diversity in the selected locations. The nutritional composition varied significantly among the species and was mostly characterized by higher levels of carbohydrate especially in Gracilaria spp. Carbohydrate content ranging from 3.52–48.22% accounted for most of the nutrient component. The overall protein ranged between 2.41–18.67%, whereas the total lipid varied from 2.16–11.90% and about 10% of total lipid content was available in most species. The significant outcome of this study was the detection of 6.34% EPA in Boergesenia forbesii and 2.40% of gamma linolenic acid in Acetabularia acetabulum which could be of significant importance in the food, bioenergy, pharmaceutical and cosmetic industries.

Physiological response to warming in intertidal macroalgae with different thermal affinity

Changes in the abundance and distribution of seaweeds have been reported worldwide. In Northwest Iberia, cold and warm affinity seaweeds have respectively decreased and increased their abundance. To improve our understanding of their vulnerability to future warming scenarios, the effects of warming on the photosynthetic and respiratory performance of seaweeds with cold-water (Fucus serratus and Vertebrata lanosa) and warm-water (Padina pavonica and Gigartina pistillata) affinities were compared in a highly resolved temperature gradient (7–31 °C) under controlled laboratory conditions. While neither the optimum temperature nor the photosynthetic rate at the optimum temperature showed consistent differences between water affinity groups, the temperature dependence of net photosynthesis was significantly higher in the warm-affinity group. Photosynthesis was less responsive than respiration to warming in cold-affinity seaweeds while both rates showed similar responsiveness in warm-affinity ones, suggesting that the relative responsiveness of respiration and photosynthesis to temperature may be indicative of warming susceptibility.

Species composition and distribution of seaweeds in Phu Yen province

Results of four field surveys, conducted from June 2017 to June 2018 found that in the Phu Yen coastal water, a total of 103 seaweed species have been recorded, increasing the total number of seaweed species in Phu Yen province to 133 species, with 81 newly recorded species for Phu Yen geographic area. Among 103 seaweed species, 4 species belong to Cyanobacteria, 38 species belong to Rhdophytes, 24 species belong to Phaeophytes, and 37 species belong to Chlorophytes. The number of species at surveyed sites V1 to V9 varies from 3 species/site (V3) to 83 species/site (V7) and on average 27 species/site. Sørensen’s similarity coefficient varies from 0.05 (between V3 and V7) to 0.86 (V3 and V4) and on average 0.25. 74/103 species were collected in the littoral zone, 67 species in sublittoral zone and most of them are distributed at 0-4 m water depth of subtidal zone. The marine algal flora is represented by mixing of subtropical and tropical characteristics as Cheney index was 3.

Value-chain distribution of seaweed production in Amal Coast, Tarakan Island

Seaweed has high economic potential which is can give a hope for coastal societies to improve their living standards. Since 2009, In Tarakan island, North Kalimantan especially In Amal’s Coast, the local communities started to developing seaweed cultivation and now seaweeds become one of Tarakan’s main commodity beside fish, shrimps and crabs. This study aims to analysis seaweed’s value chain distribution in Amal Coast, Tarakan. Data collection method is interview directly to farmers, collector traders and other marketing agents by using snowball sampling. The marketing Chains occurred trough 2 Value Chains Channel and the farmers get less profits than the factories or exporter. Therefore, it is indeed needs to improve the value chain distribution of seaweeds in Amal coast.

Japan's nationwide long‐term monitoring survey of seaweed communities known as the “Monitoring Sites 1000”: Ten‐year overview and future perspectives

SUMMARY“Monitoring Sites 1000” – Japan's long‐term monitoring survey was established in 2003, based on the Japanese Government policy for the conservation of biodiversity. Ecological surveys have been conducted on various types of ecosystems at approximately 1000 sites in Japan for 15 years now and are planned to be carried out for 100 years. Since 2008, seaweed communities had been monitored at six sites, featuring the kelp (e.g. Saccharina and Ecklonia; Laminariales) and Sargassum (Fucales) communities in the subarctic and temperate regions of Japan. Annual surveys were carried out during the season when these canopy‐forming seaweeds are most abundant. A non‐destructive quadrat sampling method, with permanent quadrats placed along transects perpendicular to the shoreline, was used to determine species composition, coverage, and vertical distribution of seaweeds at these sites; while destructive sampling was done every 5 years to determine biomass. The occurrence of canopy‐forming species Saccharina japonica (var. japonica) and Ecklonia cava have appeared to be stable at the Muroran (southwestern part of Hokkaido Island) and Shimoda (Pacific coast of middle Honshu Island) sites, respectively; whereas the coverage of Ecklonia radicosa (= Eckloniopsis radicosa) at the Satsuma‐Nagashima site in southern part of Kyushu Island was highly variable until its sudden disappearance from the habitat in 2016. Thalli of E. radicosa lost most of their blades through browsing by herbivorous fish, and thus, this may be one of the causes of the decline. A shift in the community structure related to environmental changes had also been observed at some other sites. Pre‐ and post‐disaster data revealed the impact of the 2011 earthquake and tsunami disasters, including a shift in the vertical distribution of Ecklonia bicyclis (= Eisenia bicyclis) to shallower depths at the Shizugawa site in the Pacific coast of northern Honshu Island, due to seafloor subsidence.

Yield losses and electron transport rate as indicators of thermal stress in Fucus serratus (Ochrophyta)

Global warming is driving shifts in the geographical distribution of seaweeds, such as the contraction of the Southern limit of cold-temperate Atlantic macroalgae, including the foundation intertidal fucoid Fucus serratus. However, the ecophysiological mechanisms explaining the decline of seaweeds is not fully understood. In vivo chlorophyll a fluorescence is used as an estimator of photosynthetic activity and physiological state of seaweeds. Collected at its southern distribution limit, Fucus serratus was cultured for two weeks in different temperatures (from 8 to 30 °C with increase of 2 °C). Growth rate, reproductive stage and fluorescence parameters were measured as maximal quantum yield (Fv/Fm), Electron transport rate (ETR), non-photochemical quenching (NPQ) and the yield losses (YNO and YNPQ).At high temperature, the photosynthetic responses mimic the pattern of shade adapted plants, i.e., increase of photosynthetic efficiency (αETR) and decrease of irradiance for saturation of photosynthetic rate (EkETR). At low irradiances (<66 μmol m−2 s−1) and mainly at extreme temperatures (high and low), yield loss is dominated by YNO, suggesting heat dissipation due to closure of PSII reaction centers. However, at high irradiances (1150–1500 μmol m−2 s−1) and in a wide range of temperatures (8–28 °C), yield loss is mainly due to Y(NPQ), related to the energy dissipation as heat throughout regulated photoprotective NPQ mechanisms such as the xanthophyll cycle. The optimal temperature for growth was 14–20 °C as ETRmax, whereas Fv/Fm maintains high values in a wider range of temperatures compared to ETRmax and Yield losses, indicating that Fv/Fm is not a good parameter to discriminate the effect of temperature on algal production. We discuss the use of ETR and yield losses to relate photosynthesis with growth, survival or reproduction under stress conditions. Our study shows that warming can increase photoprotection through yield loss and decrease the photosynthetic activity in macroalgae.

Species composition and quantitative distribution of seaweeds in the sublittoral zone and on the continental slope in the northwestern Japan Sea

Species composition and quantitative distribution of seaweeds on the shelf and continental slope of Primorye in the northwestern Japan Sea (depth 20–750 m) are considered on the data of trawl surveys conducted in 2015–2016. In total, 26 seaweed species were found: 16 Rhodophyta, 7 Phaeophyta, 1 Chlorophyta, and 2 species of sea grass. Most of the species were found on the depth &lt; 60 m where the biomass of seaweeds varied from 44 to 569 kg/km2. On the depth about 100 m, the biomass decreased signifcantly to the value &lt; 36.4 kg/km2, and only single seaweeds were found on the depth &gt; 700 m. There is supposed that the lowest limit of the phytal zone in the northwestern Japan Sea is located at the depth 50–100 m.

Spatial distribution shifts in two temperate fish species associated to a newly-introduced tropical seaweed invasion

The establishment of non-native habitat-forming seaweeds into new areas may trigger important changes in ecosystem functioning, yet their community and ecosystem-level effects remain largely understudied. Here we studied the spatial distribution of two common fish species (Xyrichtys novacula and Bothus podas) which are key components of communities in unconsolidated bottoms of temperate areas regarding the colonization of the newly-introduced tropical seaweed Halimeda incrassata in the Mediterranean Sea. We used a spatially-explicit before-after-control-impact model and a unique data-set formed by 6 years of fine-scale spatial information of fish and seaweed distribution and abundance. We demonstrate a long-term alteration on the spatial distribution of X. novacula characterized by a shift towards non-native H. incrassata beds, while no effect on B. podas. The introduction of the tropical seaweed H. incrassata has led to the re-distribution of X. novacula, potentially by harbouring a greater biodiversity of species at the base of the food-web through adding biogenic structure to an otherwise bare sediment. Our work demonstrates that non-native tropical habitat-forming species have the potential to maintain or even enhance fish abundance in unconsolidated bottoms in temperate areas potentially altering the functioning of native habitats.

Macroalgas exoticas en la costa de Chile: patrones espaciales y temporales en el proceso de invasion

In this paper we propose a checklist of 14 species of exotic seaweeds on the Chilean coast, and three species which, being native to the Chilean coast, have been introduced in areas outside their natural range. This list was compiled from previously published checklist, debugged the misidentified records, and incorporating new ones. The distribution of exotic seaweeds is not homogeneous along the coast, but it is concentrated in areas near ports and aquaculture centers. Most species display a fairly bounded distribution, and only four tend to invade ( i.e ., increase its range of distribution over time). However, considering that most introductions are recent (the last 60 years) and the positive relationship between amplitude of the distribution range and residence time of species on the Chilean coast, we suggest that some of these species may be in an expansion phase, which would explain its restricted distribution. This work not only updates the information related to exotic seaweed on the Chilean coast, but also allows us to understand the invasion process, through the analysis of the patterns described in these systems.

Species Compositiom and Distribution of Seaweeds at Thi Nai Lagoon, Binh Dinh Province

This paper presents results on species composition and distribution of seaweeds at Nai lagoon, Ninh Thua province from 2013 until 2014 at 12 sites was showed that, at Nai lagoon area we was recording&#x0D; 43 species of marine seaweeds, they are belonging to four divisions, as: Cyanophytes, Rhodophytes, Phaeophytes and Chlorophytes. Among them, eight species are classified in Cyanophytes (comprising 18.6% of total species); eleven species in Rhodophytes (25.6%); four species in Phaeophytes (9.3%) and twenty two species in Chlorophytes (46,5%). The species composition of marine seaweeds from Thi Nai lagoon show significant differences in the species composition as follows: 8 species (side number 4, 13 and 18) to 21 (side number 10) and average value is 12.2 species per side. The number species at dry season is 40 and rainy season is 30 (there are 30 species in of boots dry and rainy seasons) Coefficient homogeneous is oscillating from 0.10 (side number 4 and 5) to 0.66 (5 and 7). The current investigations show that 39 species of 43 species were collected in the littoral zone and 35 species in sub-littoral zone (31 species are distributing in both the tide and the sub tide). Marine algal flora in Thi Nai lagoon is represented by tropical elements as defined by Cheney.

Expression profile of desiccation tolerance factors in intertidal seaweed species during the tidal cycle.

The transcriptional modulation of desiccation tolerance factors in P. orbicularis explains its successful recuperation after water deficit. Differential responses to air exposure clarify seaweed distribution along intertidal rocky zones. Desiccation-tolerant seaweed species, such as Pyropia orbicularis, can tolerate near 96% water loss during air exposure. To understand the phenotypic plasticity of P. orbicularis to desiccation, several tolerance factors were assessed by RT-qPCR, Western-blot analysis, and enzymatic assays during the natural desiccation-rehydration cycle. Comparative enzymatic analyses were used to evidence differential responses between P. orbicularis and desiccation-sensitive species. The results showed that during desiccation, the relative mRNA levels of genes associated with basal metabolism [trehalose phosphate synthase (tps) and pyruvate dehydrogenase (pdh)] were overexpressed in P. orbicularis. Transcript levels related to antioxidant metabolism [peroxiredoxin (prx); thioredoxin (trx); catalase (cat); lipoxygenase (lox); ferredoxin (fnr); glutathione S-transferase (gst)], cellular detoxification [ABC transporter (abc) and ubiquitin (ubq)], and signal transduction [calmodulin (cam)] increased approximately 15- to 20-fold, with the majority returning to basal levels during the final hours of rehydration. In contrast, actin (act) and transcription factor 1 (tf1) transcripts were down-regulated. ABC transporter protein levels increased in P. orbicularis during desiccation, whereas PRX transcripts decreased. The antioxidant enzymes showed higher specific activity in P. orbicularis under desiccation, and sensitive species exhibited enzymatic inactivation and scarce ABC and PRX protein detection following prolonged desiccation. In conclusion, the reported findings contribute towards understanding the ecological distribution of intertidal seaweeds at the molecular and functional levels.

Diversity and spatial distribution of seaweeds in the South Shetland Islands, Antarctica: an updated database for environmental monitoring under climate change scenarios

The present study characterizes the spatial distribution of seaweed diversity on eight islands from the South Shetlands based on an updated taxonomic survey, discussing the higher number of species compared with previous studies and the possible relationships with environmental parameters. Seaweeds were sampled in Deception, Livingston, Halfmoon, Robert, Nelson, King George, Penguin, and Elephant Islands during the austral summer between 2010 and 2013 in intertidal and shallow subtidal zones. The taxonomic analyses evaluated morphological characteristics, reproductive structures, and molecular features. Physicochemical parameters of seawater were also monitored using standard analytical methods. A total of 104 species of benthic marine algae were identified (28 Phaeophyceae, 24 Chlorophyta, and 52 Rhodophyta), ~82% of all seaweeds taxa described to Antarctica, including six new records previously recorded only at lower latitudes, four confirmed taxa, and two putative new species. Spatial variation in species diversity was observed among the collecting sites, and Livingston and King George Islands showed the highest diversity among the islands. Deception, an area with geothermal activity and intense tourism, was dominated by opportunistic and broadly distributed filamentous green algae. Antarctic macroalgae diversity was higher than in previous studies, most likely due to more efficient techniques of sampling, and combined taxonomical methods. However, changes in the biogeographical distribution or introduction of some taxa, resulting from anthropogenic activities and/or climate changes, should be considered. Therefore, the higher number of taxa and the new records reported in this study suggest the need for long-term monitoring in the area for conservation purposes.

Hidden diversity and phylogeographic history provide conservation insights for the edible seaweed Sargassum fusiforme in the Northwest Pacific

Understanding the evolutionary processes that have created diversity and the genetic potential of species to adapt to environmental change is an important premise for biodiversity conservation. Herein, we used mitochondrial trnW‐L and cox3 and plastid rbcL‐S data sets to analyze population genetic variation and phylogeographic history of the brown alga Sargassum fusiforme, whose natural resource has been largely exterminated in the Asia–Northwest Pacific in the past decades. Phylogenetic trees and network analysis consistently revealed three major haplotype groups (A, B, and C) in S. fusiforme, with A and B distributed in the Japan‐Pacific coast. Group C consisted of three subgroups (C1, C2, and C3) which were distributed in the Sea of Japan, the Yellow–Bohai Sea, and East China Sea, respectively. Isolation‐with‐migration (IM a) analysis revealed that the three groups diverged approximately during the mid‐Pleistocene (c. 756–1,224 ka). Extended Bayesian skyline plots (EBSP) showed that groups A and B underwent relatively long‐term stable population size despite a subsequent rapid demographic expansion, while subgroups C2 and C3 underwent a sudden expansion at c. 260 ka. FST and AMOVA detected low population‐level genetic variation and high degrees of divergence between groups. The cryptic diversity and phylogeographic patterns found in S. fusiforme not only are essential to understand how environmental shifts and evolutionary processes shaped diversity and distribution of coastal seaweeds but also provide additional insights for conserving and managing seaweed resources and facilitate predictions of their responses to future climate change and habitat loss.

SPECIES COMPOSITION AND DISTRIBUTION OF SEAWEEDS AT NAI LAGOON, NINH THUAN PROVINCE

This paper presents the status of species composition and distribution of seaweeds at Nai lagoon, Ninh Thuan province. From 2013 to 2014, seaweed samples from 12 sites at Nai lagoon were collected. The result shows that, there are 47 species of marine seaweeds, belonging to four phyla: Cyanophytes (Cyanophyta), Rhodophytes (Rhodophyta), Phaeophytes (Phaeophyta) and Chlorophytes (Chlorophyta). Among them, five species were classified in Cyanophyta (comprising 10.6% of total species); fifteen species in Rhodophyta (31.9%); five species in Phaeophytea (10.6%) and twenty two species in Chlorophyta (46.9%). The number of species at each site is significantly different, ranges from 3 species (site number 17) to 20 (site number 6) and average value is 11.3 species per site. The number of species in dry season is 38 and in rainy season is 39, and 32 species appear in both seasons. The coefficient index fluctuates from 0.10 (site number 11 and 17) to 0.82 (14 and 17). Among 47 species, 31 species distribute in the littoral zone and 32 species distribute in sub-littoral zone. Marine algal flora in Nai lagoon is represented by tropical characteristics.

Multivariate analyses of Antarctic and sub-Antarctic seaweed distribution patterns: An evaluation of the role of the Antarctic Circumpolar Current

Biogeographic barriers and ecological corridors are fundamental in defining macroecological and evolutionary processes. Ocean circulation, considering present and past patterns of continental drift, can isolate or connect many groups of marine organisms, including seaweeds. These benthic organisms present spores and propagules as planktonic stages that drift with currents and or tides, and have been a sensible indicator of changes to biogeographical distribution patterns. Phycological studies have been exhaustive in the sub-Antarctic and Antarctic seaweed communities. However, the role of the Antarctic Circumpolar Current (ACC) in shaping marine phytogeographic diversity has been poorly investigated. The ACC connects the major world oceans and redistributes oceanic properties, such as heat, salt, and nutrients, consisting of three major circumpolar fronts (in order of north to southward): the Sub-Antarctic Front (SAF), the Antarctic Polar Front (PF), and the Southern Antarctic Circumpolar Front (SACF). This paper's aim is to understand the role of the ACC fronts as a constraint on seaweed distribution patterns in different taxonomic levels, in relation to the southern Sub-Tropical areas, as well as to compare sections connected with South America (1: north), influenced by the Ross Sea Gyre (2: Western Antarctica Peninsula) and by the Weddell Sea Gyre (3: Eastern Antarctica Peninsula). nMDS showed differences in the distributional patterns of species and genera in relation to the zones and sections. The predicted latitudinal gradient of species richness was observed, and by comparing biogeographic zones, two main clusters were observed: Sub-tropical and Sub-Antarctica; and Polar Front (Antarctic Peninsula) and SACF (areas surrounding continental Antarctica), suggesting, for this sort of macroscale analysis, that ACC still has a role of “watershed barrier”. However, a lower dissimilarity (higher similarity) was observed between the 2nd (Eastern Antarctica Peninsula – EAP – or under influence of the Weddell Sea Gyre, and some sub-Antarctic islands as South Orcadas, South Georgia and Crozet Archipelago) and the 1st sectors (Chilean and Argentinean Patagonia and surrounding islands, Falklands, South Shetlands and including Antarctic Peninsula). When considering recently reported changes in diversity patterns of these locations, this result could demonstrate the existence of a clear species distributional flux, despite evidence of the ACC being a limit to dispersal. Therefore, this contribution has used previously published data to provide a tool for monitoring future biogeographical changes to the flora and fauna of this region of the Antarctic and sub-Antarctic areas due to changes in biogeographical distribution, resulting either from natural dispersion due to global meteoceanographic changes, and or biological invasions related to anthropogenic activities. We could be witness to a period of changes in Antarctic diversity, suggesting that Antarctica may not be as isolated as was once thought.

Phylogeographic surveys and apomictic genetic connectivity in the North Atlantic red seaweed Mastocarpus stellatus

The North Atlantic red alga Mastocarpus stellatus is characterized by two life histories (sexual-type and direct-type), which correspond to two geographically isolated breeding groups. These features enable M. stellatus to be an interesting model to investigate how environmental shift and apomictic propagation have influenced its population genetic structure, historical demography and distribution dynamic. To test these ideas, we obtained 456 specimens from 15 locations on both sides of the North Atlantic and sequenced portion of the nuclear internal transcribed spacer (ITS), mitochondrial cox2–3 region (COX) and plastid RuBisCo spacer (RLS). Median-joining networks and ML trees inferred from COX and RLS consistently revealed two gene lineages (mtDNA: CN, CS; cpDNA: RN, RS). The concatenated COX and RLS markers yielded three cytotypes: a northern CN–RN, a southern CS–RS and a mixed cytotype CS–RN, which enabled us to roughly separate samples into D (direct-type life-cycle) and S (sexual-type life-cycle) groups (northern CN–RN and mixed cytotype CS–RN=D; southern CS–RS=S). Pairwise FST analysis of the D group revealed a high level of genetic differentiation both along European coasts and across the Atlantic basin. Bayesian skyline plots (BSPs) and IMa analyses indicated that M. stellatus underwent slight demographic expansion at the late-Pleistocene, with the beginning of divergence between lineages dating to c. 0.189Ma (95%HPD: 0.083–0.385Ma). IMa analyses also revealed asymmetric genetic exchange among European populations and a predominant postglacial trans-Atlantic migration from Norway and Galway Bay to North America. Our study highlights the importance of phylogeographic approaches to discover the imprints of climate change, life histories and gene flow in driving population genetic connectivity and biogeographic distribution of intertidal seaweeds in the North Atlantic.

한국 남서해안 진도군 금갑의 해조상 및 군집구조의 계절 변화

Seasonal variation in marine macroalgal community structure was examined at the intertidal zones of Geumgap, Jindo, Korea, from October 2013 to August 2014. In total, 56 macroalgal species were identified, including 9 green, 12 brown, and 35 red algae. Annual seaweed biomass was 548.96 g wet wt. /<TEX>$m^2$</TEX> with seasonal range between 371.08 g wet wt. /<TEX>$m^2$</TEX> at summer and 32.91 g wet wt. /<TEX>$m^2$</TEX> at winter. The dominant seaweed in terms of biomass was Sargassum thunbergii and subdominant species were Gelidium elegans, Sargassum fusiforme, and Ishige okamurae. The vertical distribution of seaweeds from the upper to lower intertidal zones was Gloiopeltis spp., Ulva spp.- S. thunbergii, S. fusiforme, Ishige okamurae - S. thunbergii, S. fusiforme, G. elegans. Annual seaweed coverage, richness index (R), evenness index (J'), and diversity index (H') values were 27.95%, 6.10, 0.38, and 1.38, respectively. Coarsely branched form was the most dominant functional group in terms of species number and biomass among benthic macroalgal species.

The distribution and environmental requirements of large brown seaweeds in the British Isles

Kelps, fucoids and other large brown seaweeds are common and important features of temperate coastal zones. The British Isles is a centre for seaweed diversity in the NE Atlantic, but, despite numerous surveys, an incomplete picture of the distribution remains. Survey data and herbarium specimens were used to examine the environmental preference of 15 species of large brown seaweeds, covering the orders Laminariales (kelps), Fucales (wracks) and one species of Tilopteridales. Habitat suitability models were developed to estimate broad-scale distribution and area of habitat created by these species around the British Isles. Topographic parameters were important factors limiting distributions. Generally, temperature did not appear to be a limiting factor, probably because the British Isles lies in the centre of the NE Atlantic distribution for most species, and not at climatic tolerance limits. However, for the recent migrant Laminaria ochroleuca, temperature was found to be important for the model, thus range expansion could continue northwards provided dispersal is possible. In contrast, the widespread Alaria esculenta showed a negative association with warmer summer temperatures. The total potential habitat around the British and Irish coastline is more than 19,000 km2 for kelps and 11,000 km2 for wracks, which represents a significant habitat area similar in scale to British broadleaf forest. We conclude that large brown algal species need to be managed and conserved in a manner that reflects their scale and importance.