cpDNA-RFLP in Ceramium (Rhodophyta): Intraspecific polymorphism and species-level phylogeny

Restriction fragment length polymorphism (RFLP) analysis of chloroplast (cp) DNA is a powerful tool for the study of microevolutionary processes in land plants, yet has not previously been applied to seaweed populations. We used cpDNA-RFLP, detected on Southern blots using labeled total plastid DNA, to search for intraspecific and intrapopulational cpDNA RFLP polymorphism in two species of the common red algal genus Ceramium in Ireland and Britain. In C. botryocarpum one polymorphism was detected in one individual among 18 from two populations. Twenty-six individuals of C. virgatum from five populations at three locations exhibited a total of four haplotypes. One was frequent (80.8% of individuals); the others were rare (7.7, 7.7 and 4.2%) and were private to particular populations. Polymorphism was observed in two populations. The corrected mean was 2.26 +/- 0.36 haplotypes per population, which was within the typical range determined for higher plants using similar techniques. The spatial distribution of haplotypes was heterogeneous, with highly significant population differentiation (P = 0.00018; Fisher's exact test). Intraspecific polymorphism in C. virgatum had no impact on species-level phylogenetic reconstruction. This is the first unequivocal report of both intraspecific and intrapopulational cpDNA-RFLP polymorphism in algae.

Ca(2+) signals coordinate zygotic polarization and cell cycle progression in the brown alga Fucus serratus

Zygotes of the fucoid brown algae provide excellent models for addressing fundamental questions about zygotic symmetry breaking. Although the acquisition of polarity is tightly coordinated with the timing and orientation of the first asymmetric division-with zygotes having to pass through a G1/S-phase checkpoint before the polarization axis can be fixed -the mechanisms behind the interdependence of polarization and cell cycle progression remain unclear. In this study, we combine in vivo Ca(2+) imaging, single cell monitoring of S-phase progression and multivariate analysis of high-throughput intracellular Ca(2+) buffer loading to demonstrate that Ca(2+) signals coordinate polarization and cell cycle progression in the Fucus serratus zygote. Consistent with earlier studies on this organism, and in contrast to animal models, we observe no fast Ca(2+) wave following fertilization. Rather, we show distinct slow localized Ca(2+) elevations associated with both fertilization and S-phase progression, and we show that both S-phase and zygotic polarization are dependent on pre-S-phase Ca(2+) increases. Surprisingly, this Ca(2+) requirement cannot be explained by co-dependence on a single G1/ S-phase checkpoint, as S phase and zygotic polarization are differentially sensitive to pre-S-phase Ca(2+) elevations and can be uncoupled. Furthermore, subsequent cell cycle progression through M phase is independent of localized actin polymerization and zygotic polarization. This absence of a morphogenesis checkpoint, together with the observed Ca(2+)dependences of S phase and polarization, show that the regulation of zygotic division in the brown algae differs from that in other eukaryotic model systems, such as yeast and Drosophila.

delta C-13 and delta N-15 reveal significant differences in the coastal foodwebs of the seas surrounding Trinidad and Tobago

This study assessed nearshore, marine ecosystem function around Trinidad and Tobago (TT). The coastline of TT is highly complex, bordered by the Atlantic Ocean, the Caribbean Sea, the Gulf of Paria and the Columbus Channel, and subject to local terrestrial runoff and regional riverine inputs (e.g. the Orinoco and Amazon rivers). Coastal organisms can assimilate energy from allochthonous and autochthonous Sources, We assessed whether stable isotopes delta C-13 and delta N-15 Could be used to provide a rapid assessment of trophic interactions in primary consumers around the islands. Filter-feeding (bivalves and barnacles) and grazing organisms (gastropods and chitons) were collected from 40 marine sites during the wet season. The flesh of organisms was analysed for delta C-13 and delta N-15. Results indicate significant variation in primary consumers (by feeding guild and sampling zone). This variation was linked to different energy Sources being assimilated by consumers. Results suggest that offshore production is fuelling intertidal foodwebs; for example, a depleted delta C-13 signature in grazers from the Gulf of Paria, Columbus Channel and the Caribbean and Atlantic coastline of 9 Tobago indicates that carbon with an offshore origin (e.g. phytoplankton and dissolved organic matter) is more important than benthic or littoral algae (luring the wet season. Results also confirm findings from other studies indicating that much of the coastline is subject to Cultural eutrophication. This Study revealed that ecosystem function is spatially variable around the coastline of TT, This has clear implications for marine resource management, as a single management approach is unlikely to be successful at a national level.

Predatory fish loss affects the structure and functioning of a model marine food web

The rate of species loss is increasing on a global scale and predators are most at risk from human-induced extinction. The effects of losing predators are difficult to predict, even with experimental single species removals, because different combinations of species interact in unpredictable ways. We tested the effects of the loss of groups of common predators on herbivore and algal assemblages in a model benthic marine system. The predator groups were fish, shrimp and crabs. Each group was represented by at least two characteristic species based on data collected at local field sites. We examined the effects of the loss of predators while controlling for the loss of predator biomass. The identity, not the number of predator groups, affected herbivore abundance and assemblage structure. Removing fish led to a large increase in the abundance of dominant herbivores, such as Ampithoids and Caprellids. Predator identity also affected algal assemblage structure. It did not, however, affect total algal mass. Removing fish led to an increase in the final biomass of the least common taxa (red algae) and reduced the mass of the dominant taxa (brown algae). This compensatory shift in the algal assemblage appeared to facilitate the maintenance of a constant total algal biomass. In the absence of fish, shrimp at higher than ambient densities had a similar effect on herbivore abundance, showing that other groups could partially compensate for the loss of dominant predators. Crabs had no effect on herbivore or algal populations, possibly because they were not at carrying capacity in our experimental system. These findings show that contrary to the assumptions of many food web models, predators cannot be classified into a single functional group and their role in food webs depends on their identity and density in 'real' systems and carrying capacities.

Data mining approach identifies research priorities and data requirements for resolving the red algal tree of life

Background. The assembly of the tree of life has seen significant progress in recent years but algae and protists have been largely overlooked in this effort. Many groups of algae and protists have ancient roots and it is unclear how much data will be required to resolve their phylogenetic relationships for incorporation in the tree of life. The red algae, a group of primary photosynthetic eukaryotes of more than a billion years old, provide the earliest fossil evidence for eukaryotic multicellularity and sexual reproduction. Despite this evolutionary significance, their phylogenetic relationships are understudied. This study aims to infer a comprehensive red algal tree of life at the family level from a supermatrix containing data mined from GenBank. We aim to locate remaining regions of low support in the topology, evaluate their causes and estimate the amount of data required to resolve them. Results. Phylogenetic analysis of a supermatrix of 14 loci and 98 red algal families yielded the most complete red algal tree of life to date. Visualization of statistical support showed the presence of five poorly supported regions. Causes for low support were identified with statistics about the age of the region, data availability and node density, showing that poor support has different origins in different parts of the tree. Parametric simulation experiments yielded optimistic estimates of how much data will be needed to resolve the poorly supported regions (ca. 103 to ca. 104 nucleotides for the different regions). Nonparametric simulations gave a markedly more pessimistic image, some regions requiring more than 2.8 105 nucleotides or not achieving the desired level of support at all. The discrepancies between parametric and nonparametric simulations are discussed in light of our dataset and known attributes of both approaches. Conclusions. Our study takes the red algae one step closer to meaningful inclusion in the tree of life. In addition to the recovery of stable relationships, the recognition of five regions in need of further study is a significant outcome of this work. Based on our analyses of current availability and future requirements of data, we make clear recommendations for forthcoming research.

Intertidal molluscan and algal species richness around the UK coast

Geographically referenced databases of species records are becoming increasingly available. Doubts over the heterogeneous quality of the underlying data may restrict analyses of such collated databases. We partitioned the spatial variation in species richness of littoral algae and molluscs from the UK National Biodiversity Network database into a smoothed mesoscale component and a local component. Trend surface analysis (TSA) was used to define the mesoscale patterns of species richness, leaving a local residual component that lacked spatial autocorrelation. The analysis was based on 10 km grid squares with 115035 records of littoral algae (729 species) and 66879 records of littoral molluscs (569 species). The TSA identified variation in algal and molluscan species richness with a characteristic length scale of approximately 120 km. Locations of the most species-rich grid squares were consistent with the southern and western bias of species richness in the UK marine flora and fauna. The TSA also identified areas which showed significant changes in the spatial pattern of species richness: breakpoints, which correspond to major headlands along the south coast of England. Patterns of algal and molluscan species richness were broadly congruent. Residual variability was strongly influenced by proxies of collection effort, but local environmental variables including length of the coastline and variability in wave exposure were also important. Relative to the underlying trend, local species richness hotspots occurred on all coasts. While there is some justification for scepticism in analyses of heterogeneous datasets, our results indicate that the analysis of collated datasets can be informative.

The extent of grazing release from epiphytism for Sargassum muticum (Phaeophyceae) within the invaded range

The overall biotic pressure on a newly introduced species may be less than that experienced within its native range, facilitating invasion. The brown alga Sargassum muticum (Yendo) Fensholt is a conspicuous and successful invasive species originally from Japan and China. We compared S. muticum and native macroalgae with respect to the biotic pressures of mesoherbivore grazing and ectocarpoid fouling. In Strangford Lough, Northern Ireland, S. muticum thalli were as heavily overgrown with seasonal blooms of epiphytic algae as native macroalgal species were. The herbivorous amphipod Dexamine spinosa was much more abundant on S. muticum than on any native macroalga. When cultured with this amphipod, S. muticum lost more tissue than three native macroalgae, Saccharina latissima (Linnaeus) Lane et al., Halidrys siliquosa (Linnaeus) Lyngbye and Fucus serratus Linnaeus. Sargassum muticum cultured with both ectocarpoid fouling and amphipods showed a severe impact, consistent with our previous findings of large declines in the density of S. muticum observed in the field during the peak of fouling. Despite being a recent introduction into the macroalgal community in Strangford Lough, S. muticum appears to be under biotic pressure at least equal to that on native species, suggesting that release from grazing and epiphytism does not contribute to the invasiveness of this species in Strangford Lough.

Like a rolling stone: the mobility of maerl (Corallinaceae) and the neutrality of the associated assemblages

Beds of nonattached coralline algae (maerl or rhodoliths) are widespread and considered relatively species rich. This habitat is generally found in areas where there is chronic physical disturbance such that maerl thalli are frequently moved. Little is known, however, about how natural disturbance regimes affect the species associated with maerl. This study compared the richness, animal abundance, and algal biomass of maerl-associated species over a two-year period in a wave-disturbed bed and a sheltered maerl bed. Changes in associated species over time were assessed for departures from a neutral model in which the dissimilarity between samples reflects random sampling from a common species pool. Algal biomass and species richness at the wave-exposed site and on stabilized maerl at the sheltered site were reduced at times of higher wind speeds. The changes in species richness were not distinguishable from a neutral model, implying that algal species were added at random to the assemblage as the level of disturbance lessened. Results for animal species were more mixed. Although mobile species were less abundant during windy periods at the exposed site, both neutral and non-neutral patterns were evident in the assemblages. Artificial stabilization of maerl had inconsistent effects on the richness of animals but always resulted in more attached algal species. While the results show that the response of a community to disturbance can be neutral, the domain of neutral changes in communities may be relatively small. Alongside non-neutral responses to natural disturbance, artificial stabilization always resulted in an assemblage that was more distinct than would be expected under random sampling from a common pool. Community responses to stabilization treatments did not consistently follow the predictions of the dynamic equilibrium model, the intermediate disturbance model, or a facilitation model. These inconsistencies may reflect site-specific variation in both the disturbance regime and the adjacent habitats that provide source populations for many of the species found associated with maerl.

Proteomics Identification of Azaspiracid Toxin Biomarkers in Blue Mussels, Mytilus edulis

Azaspiracids are a class of recently discovered algae-derived shellfish toxins. Their distribution globally is on the increase with mussels being most widely implicated in azaspiracid-related food poisoning events. Evidence that these toxins were bound to proteins in contaminated mussels has been shown recently. In the present study characterization of these proteins in blue mussels, Mytilus edulis, was achieved using a range of advanced proteomics tools. Four proteins present only in the hepatopancreas of toxin-contaminated mussels sharing identity or homology with cathepsin D, superoxide dismutase, glutathione S-transferase Pi, and a bacterial flagellar protein have been characterized. Several of the proteins are known to be involved in self-defense mechanisms against xenobiotics or up-regulated in the presence of carcinogenic agents. These findings would suggest that azaspiracids should now be considered and evaluated as potential tumorigenic compounds. The presence of a bacterial protein only in contaminated mussels was an unexpected finding and requires further investigation. The proteins identified in this study should assist with development of urgently required processes for the rapid depuration of azaspiracid-contaminated shellfish. Moreover they may serve as early warning indicators of shellfish exposed to this family of toxins. Molecular & Cellular Proteomics 8: 1811-1822, 2009.

Remote, subsurface detection of the algal toxin domoic acid onboard the Environmental Sample Processor: Assay development and field trials

The ability to detect harmful algal bloom (HAB) species and their toxins in real- or near real-time is a critical need for researchers studying HAB/toxin dynamics, as well as for coastal resource managers charged with monitoring bloom populations in order to mitigate their wide ranging impacts. The Environmental Sample Processor (ESP), a robotic electromechanical/fluidic system, was developed for the autonomous, subsurface application of molecular diagnostic tests and has successfully detected several HAB species using DNA probe arrays during field deployments. Since toxin production and thus the potential for public health and ecosystem effects varies considerably in natural phytoplankton populations, the concurrent detection of HAB species and their toxins onboard the ESP is essential. We describe herein the development of methods for extracting the algal toxin domoic acid (DA) from Pseudonitzschia cells (extraction efficiency >90%) and testing of samples using a competitive ELISA onboard the ESP. The assay detection limit is in the low ng/mL range (in extract), which corresponds to low ng/L levels of DA in seawater for a 0.5 L sample volume acquired by the ESP. We also report the first in situ detection of both a HAB organism (i.e., Pseudo-nitzschia) and its toxin, domoic acid, via the sequential (within 2-3 h) conduct of species- and toxin-specific assays during ESP deployments in Monterey Bay, CA, USA. Efforts are now underway to further refine the assay and conduct additional calibration exercises with the aim of obtaining more reliable, accurate estimates of bloom toxicity and thus their potential impacts. Published by Elsevier B.V.

Late Holocene climate change in central Sweden inferred from lacustrine stable isotope data

Stable isotopes (delta O-18 and delta C-13) of lacustrine carbonates (Chara spp. algae and Pisidium spp. molluscs) from a lake sedimentary sequence in central Sweden were analysed to infer changes in lake hydrology and climate during the late Holocene. Results from analysis of lake water isotopes (delta O-18 and delta H-2) show that Lake Blektjarnen water isotope composition is responsive to the balance between evaporation and input water (E/l ratio). A high E/l ratio results from a dry and probably warmer climate, decreasing the relative importance of precipitation input. Under such conditions evaporation and atmospheric equilibration probably enrich lake water in O-18 and C-13, respectively, which is reflected in the isotopic composition of the carbonates in the lake. From the relatively positive Chara delta O-18 values we infer that conditions were dry and warm between 4400 and 4000 cal. a BP, whereas more negative values indicate that conditions were wetter and probably cooler between 4000 and 3000 cal. a BP. A drier climate is inferred from more positive values between 2500 and 1000 cal. a BP. However, a successive depletion after ca. 1750 cal. a BP, also detected in several other delta O-18 records (carbonate and diatom), suggest increasingly wetter conditions in Scandinavia after that time, which is probably related to increased strength of the zonal flow.

Importance of consumers on exposed and sheltered rocky shores.

It is often suggested that the relative importance of biotic processes, such as recruitment, competition and predation of marine benthic species, varies predictably along a gradient of exposure to wave action. Several established models of community dynamics on rocky shores predict that top-down processes are more important for structuring communities on sheltered than on exposed shores. To test the relative dominance of top-down processes, we first measured the establishment of key benthic species (mussels, barnacles and algae) on 3 sheltered and 3 exposed rocky shores in southwest Ireland over two 6 mo periods. We then manipulated the presence of consumers (e.g. grazing gastropods, crabs, whelks), using caged exclosures, on 2 sheltered and 2 exposed shores to test for an interaction between effects of consumers and shore exposure on the establishment of benthic species. In contrast to predictions, we found that consumers strongly affected establishment of all species regardless of shore exposure. We also found that shore exposure was not a reliable predictor for spatial and temporal variation in rates of establishment of sessile benthic species. Our findings provide experimental evidence which demonstrates the importance of consumers in early post-settlement stages of benthic species-essential for the development of benthic-pelagic models. © 2011 Inter-Research.


--------------------------------------------------------------------------------

Reaxys Database Information|

Physical and immunoaffinity extraction of paralytic shellfish poisoning toxins from cultures of the dinoflagellate Alexandrium tamarense

In the present study the extraction of paralytic shellfish poisoning (PSP) toxins from a toxic strain of the marine dinoflagellate Alexandrium tamarense CCMP-1493 using various mechanical and/or physical procedures was investigated. PBS buffer was investigated as the extraction solvent in order for these procedures to be used directly with immuno-magnetic Ferrospheres-N. The extraction was performed following the determination of when toxin content by the algae was at its highest during batch culture. The methods used for cell lysis and toxin extraction included freeze-thawing, freeze-boiling, steel ball bearing beating, glass bead beating, and sonication. The steel ball bearing beating was determined to release a similar amount of toxin when compared to a modified standard extraction method which was reported to release 100% of toxins from the algal cells and was therefore used in the next phase of the study. This next phase was to determine the feasibility of utilising an antibody coupled to novel magnetic microspheres (Ferrospheres-N) as a simple, rapid immune-capture procedure for PSP toxins extracted from the algae. The effects of increasing mass of Ferrospheres-N on the immuno-capture of the PSP toxins from the toxic algal strain extracts were investigated. Toxin recovery was found to increase when an increasing mass of Ferrospheres-N was used until 96.2% (+/- 1.3 SD) of the toxin extracted from the cells was captured and eluted. Toxin recovery was determined by comparison to an appropriate PSP toxin standard curve following analysis by the AOAC HPLC method. (C) 2011 Elsevier B.V. All rights reserved.

An in vitro Study to Assess the Potential of a Unique Micro porous Algal Derived Cap Bone Void Filler in Comparison with Clinically-Used Bone Void Fillers

Macroporosity(>100µm) in bone void fillers is a known prerequisite for tissue regeneration, but recent literature has highlighted the added benefit of microporosity(0.5 - 10µm). The aim of this study was to compare the in vitro performances of a novel interconnective microporous hydroxyapatite (HA) derived from red algae to four clinically available macroporous calcium phosphate (CaP) bone void fillers. The use of algae as a starting material for this novel void filler overcomes the issue of sustainability, which overshadows continued use of scleractinian coral in the production of some commercially available materials, namely Pro-OsteonTM and Bio-Coral®. This study investigated the physicochemical properties of each bone voidfiller material using x-ray diffraction, fourier transform infrared spectroscopy, inductive coupled plasma, and nitrogen gas absorption and mercury porosimetry. Biochemical analysis, XTT, picogreen and alkaline phosphatase assays were used to evaluate the biological performances of the five materials. Results showed that algal HA is non-toxic to human foetal osteoblast (hFOB) cells and supports cell proliferation and differentiation. The preliminary in vitro testing of microporous algal-HA suggests that it is comparable to the four clinically approved macroporous bone void fillers tested. The results demonstrate that microporous algal HA has good potential for use in vivo and in new tissue engineered strategies for hard tissue repair.

Reappraisal of the type species of Polysiphonia (Rhodomelaceae, Rhodophyta)

The genus Polysiphonia Greville, nom. cons., has had a long and confused nomenclatural history. At present, Polysiphonia has a wide circumscription, including at least 200 species, but it is heterogeneous in many vegetative and reproductive developmental features. Central to any re-evaluation of the genus is a detailed examination of the type species of Polysiphonia, P. urceolata (Lightfoot ex Dillwyn) Greville, which is conspecific with P. stricta (Dillwyn) Greville. We here report on the vegetative and reproductive morphology of P. stricta, including P, urceolata, based on type and other material from the British Isles. Thalli consist of prostrate and erect ecorticate axes with four pericentral cells, attached by unicellular rhizoids remaining in open connection with pericentral cells. Prostrate axes lack vegetative trichoblasts; trichoblasts occur seasonally on erect axes. Branch initials are cut off from the subapical cell at intervals of four or five segments in dichotomous and alternating pairs rather than being formed horn each axial cell in the spiral pattern typical of most species of Polysiphonia. Spermatangial branch initials, which are trichoblast homologues, are produced directly from each axial cell at the tips of erect branches, not subtended by trichoblasts, and have two- to five-celled sterile tips when mature. The mature carpogonial branch is four-celled with a two-celled first sterile group and a one-celled second sterile group. Following presumed fertilization, direct fusion apparently takes place between carpogonium and auxiliary tell; mature cystocarps are usually urceolate. Tetrasporangia are formed from the third pericentral cell, in straight series, and have two pre-sporangial cover cells. Previous accounts of a third, post-sporangial cover cell could not be substantiated. P. stricta and a small group of other Polysiphonia species differ in several important respects from most members of the genus, which have rhizoids cut off from pericentral cells by a cell division, abundant trichoblasts, spirally arranged tetrasporangia and a post-sporangial cover cell. The branching pattern of P. stricta highlights the difficulties of distinguishing between the tribes Polysiphonieae and Pterosiphonieae.