The biology and physiology of alga-invertebrates symbioses. II. The density of symbiotic algal cells in a number of hermatypic hard corals and alcyonarians from various depths

Ten genera of hermatypic hard corals and two genera of soft corals were found to contain similar numbers of symbiotic algal cells per unit area irrespective of genus, depth of growth, growth form, or locality. An average of 1.45 cells/cm² (range 0.90–2.48) was found with some reduction in very shallow and very deep waters. The hard coral Plerogyra sp. contained substantially more algal cells per unit area of corallite, a feature correlated with its structure and habit, but its effective algal cell density during daylight approachs that of the other corals examined.     

What remains after 2 months of starvation? Analysis of sequestered algae in a photosynthetic slug, Plakobranchus ocellatus (Sacoglossa, Opisthobranchia), by barcoding

The sacoglossan sea slug, Plakobranchus ocellatus, is a so-called long-term retention form that incorporates chloroplasts for several months and thus is able to starve while maintaining photosynthetic activity. Little is known regarding the taxonomy and food sources of this sacoglossan, but it is suggested that P. ocellatus is a species complex and feeds on a broad variety of Ulvophyceae. In particular, we analysed specimens from the Philippines and starved them under various light conditions (high light, low light and darkness) and identified the species of algal food sources depending on starvation time and light treatment by means of DNA-barcoding using for the first time the combination of two algal chloroplast markers, rbcL and tufA. Comparison of available CO1 and 16S sequences of specimens from various localities indicate a species complex with likely four distinct clades, but food analyses do not indicate an ecological separation of the investigated clades into differing foraging strategies. The combined results from both algal markers suggest that, in general, P. ocellatus has a broad food spectrum, including members of the genera Halimeda, Caulerpa, Udotea, Acetabularia and further unidentified algae, with an emphasis on H. macroloba. Independent of the duration of starvation and light exposure, this algal species and a further unidentified Halimeda species seem to be the main food source of P. ocellatus from the Philippines. It is shown here that at least two (or possibly three) barcode markers are required to cover the entire food spectrum in future analyses of Sacoglossa.     

Identification of teratogenic polymethoxy-1-alkenes from Cylindrospermopsis raciborskii,and taxonomically diverse freshwater cyanobacteria and green algae

Cylindrospermopsis raciborskii is among the most commonly recognized toxigenic cyanobacteria associated with harmful algal blooms (HAB) in freshwater systems, and specifically associated with multiple water-soluble toxins. Lipophilic metabolites from C. raciborskii, however, were previously shown to exert teratogenicity (i.e. inhibition of vertebrate development) in the zebrafish (Danio rerio) embryo model, specifically suggesting the presence of additional bioactive compounds unrelated to the currently known toxins. In the present study, a series of known teratogenic polymethoxy-1-alkenes (PMA) were identified, purified and chemically characterized from an otherwise well-characterized strain of toxigenic C. raciborskii. Although PMA have been previously identified in other cyanobacteria, this is the first time they have been identified from this recognized HAB species. Following their identification from C. raciborskii, the taxonomic distribution of the PMA was additionally investigated by chemical screening of a freshwater algal (i.e. cyanobacteria, green algal) culture collection. Screening suggests that these compounds are distributed among phylogenetically diverse taxa. Furthermore, parallel screening of the algal culture collection, using the zebrafish embryo model of teratogenicity, the presence of PMA was found to closely correlate with developmental toxicity of these diverse algal isolates. Taken together, the data suggest PMA contribute to the toxicity of C. raciborskii, as well as apparently several other taxonomically disparate cyanobacterial and green algal genera, and may, accordingly, contribute to the toxicity of diverse freshwater HAB.     

Non-calcified warm-water marine macroalgae from the Ordovician strata of Spiti,Tethys Himalaya,India

The calcareous siltstones within the Ordovician section of the Takche Formation near Takche, Spiti region of Tethyan Himalaya, India, contain numerous specimens of non-calcified marine macroalgae in association with brachiopods, gastropods, tentaculitoids, and few trace fossils. The algal remains, representing five genera, are preserved as black or dark brown carbonaceous compression fossils, interpreted as warm-water marine macroalgae, namely, Inocladus sp., Callisphenus? sp., Algites sp. (siphonous algae), Fisherites sp., and Mastopora sp. (non-siphonous). Callisphenus is characterised by a radially symmetrical short pyriform thallus, with a central axis surrounded by short laterals whereas Inocladus sp. is characterised by an unsegmented simple thallus with internal parallel medullary siphons and cortical tubes. These algal remains, probably transported from a more near-shore living niche, co-occur with Cyclocrinitids, Tentaculitoids tube worms, trace fossils and brachiopods, suggesting that deposition of the studied units took place in low energy hydrodynamic conditions influenced by intermittent storm events. The study represents the first diversified macroalgal records from the Ordovician strata in the Tethyan realm of Indian subcontinent.     

Tracking paleoenvironmental changes in coralline algal-dominated carbonates of the Lower Oligocene Calcareniti di Castelgomberto formation (Monti Berici, Italy)

Lower Oligocene, shallow-water carbonates of the Calcareniti di Castelgomberto formation (Monti Berici, Italy, Southern Alps) are studied in detail with respect to fabric and component distributions in order to trace paleoecological changes along a monotonous sedimentary stacking pattern. The carbonates are dominated by coralline algal rudstones with a packstone to wackestone matrix. Non-geniculate coralline algae include six genera: Lithoporella melobesioides, Mesophyllum, Neogoniolithon, Spongites, Sporolithon, and Subterraniphyllum. The algae are found in the form of encrusting thalli, rhodoliths, and coralline debris. Non-algal components include larger, small benthic, and planktonic foraminifera associated with bryozoans, zooxanthellate corals, and echinoderms. Four carbonate facies are distinguished: (1) coralline algal facies, (2) coralline algal-coral facies, (3) coralline algal-larger foraminiferal facies, and (4) coralline algal debris facies. Marly horizons also occur in the section. The facies and coralline algal content are interpreted with respect to light intensity, hydrodynamic energy, biotic interactions, and substrate stability. Facies development along the studied section shows systematic variations, suggesting asymmetric sea-level changes with rapid regressions and gradual transgressions.     

Responses of foraminiferal assemblages to ENSO climate patterns on bank reefs of northern Bahia,Brazil: A 17-year record

Benthic Foraminifera were assessed in Rose Bengal-stained sediment samples collected annually from 1995 to 2011 at four shallow bank reefs in Northern Bahia (Brazil). The assemblage was represented by 284 species and 88 genera, the most diverse genera being Quinqueloculina (46 spp.), Triloculina (24 spp.), Articulina (13 spp.), Textularia (11 spp.), and Elphidium (10 spp.). Significant differences in densities of live foraminifers in the sediments were observed among years, though not between reefs. Mean densities and diversities declined by ∼90% during the 1997–8 El Niño event compared with the two previous years, then rebounded during the strong La Niña years of 1999–2000, with rapid recovery of populations of small, heterotrophic foraminifers in the assemblage. After 2000, mean densities and diversities fluctuated, with lows following both the 2006–7 and 2009–10 weak El Niño events, but not so pronounced as during the 1997–8 event. Multivariate analysis clearly formed four separate groupings representing strong (hot, dry) and weak El Niño (dry) years, “normal” years, and strong La Niña (high rainfall) years. The FoRAM Index (FI), which is a single-metric index for water quality associated with reef accretion, provided additional insights into assemblage responses. The FI compares relative abundances of three functional groups of benthic foraminifers: characteristic reef-dwelling larger foraminifers that host algal endosymbionts, the ubiquitous heterotrophic smaller taxa, and specifically stress-tolerant heterotrophic taxa. The striking decline in overall densities during El Niño years likely reflects reduced food supply for the heterotrophic taxa, associated with higher temperatures and reduced runoff. Decline in the taxa that host algal symbionts is consistent with reports of extensive coral bleaching, likely related to photo-oxidative stress caused by higher temperatures and increased water transparency. The significant changes in assemblage structure and composition recorded during this 17-year study demonstrate the major influence of climatic variability associated with the El Niño/La Niña-Southern Oscillation.     

End-Permian mass extinction of calcareous algae and microproblematica from Liangfengya,South China

A new assemblage of calcareous algae and microproblematica is reported from the Changxing Formation at the Liangfengya section in Chongqing, South China. This assemblage comprises eighteen species of seven genera, including three genera of gymnocodiaceaens (Gymnocodium, Permocalculus, and Tauridium), three genera of dasycladaleans (Epimastopora, Macroporella, and Mizzia), and one genus of microproblematica (Pseudovermiporella). A new algal species, Tauridium elongatum nov. sp., is described. Quantitative analysis indicates that the last occurrences of 22% of the species (4 out of 18) fall into a 52 cm thick interval of the uppermost Changhsingian. No calcareous algae are found in the Permian-Triassic boundary (P-T boundary) beds and the overlying Feixianguan Formation. Four out of 10 species have a stratigraphic abundance greater than 10% and all vanished in the uppermost Changhsingian. An abrupt extinction for calcareous algae occurred in the Clarkina yini conodont Zone.     

Lysis of a red-tide causing alga,Alexandrium tamarense,caused by bacteria from its phycosphere

There are bacteria coexisting in xenic cultures of Alexandrium tamarense, a red-tide causing alga. However little is known concerning the interactions between the alga and the bacteria in its phycosphere. The objective of the current study was to determine the effect of the bacteria in its phycosphere on the growth of the alga. We added one percent (v/v) Zobell 2216E medium to A. tamarense culture to alter bacterial growth and the results showed that algal cells were all lysed within 14 h. After adding the medium, both the abundance and the extracellular enzyme activity of the bacteria increased by 50–100 times from the 4th to the 10th hour which resulted in lysis of the algae. The 16S rRNA gene fragments of the bacteria were amplified from the DNA extracted from A. tamarense cultures and analyzed by denaturing gradient gel electrophoresis and sequencing. The structure of the bacterial community in phycosphere changed significantly during algal lysis. Two bacterial genera, Alteromonas sp. and Thalassobius aestuarii sp. are key factors that caused the lysis, and the β-glucosidase and chitinase produced by the bacteria in the phycosphere could directly cause the lysis. These experiments provide evidence that bacteria in its phycosphere play a key role in the culture of A. tamarense, and may provide insights into the future biocontrol of red-tides.     

Decomposition of Blue-Green Algal (Cyanobacterial) Blooms in Lake Mendota, Wisconsin

Decomposition of natural populations of Lake Mendota phytoplankton dominated by blue-green algae (cyanobacteria) was monitored by using oxygen uptake and disappearance of chlorophyll, algal volume (fluorescence microscopy), particulate protein, particulate organic carbon, and photosynthetic ability (¹⁴CO₂ up-take). In some experiments, decomposition of ¹⁴C-labeled axenic cultures of Anabaena sp. was also measured. In addition to decomposition, mineralization of inorganic nitrogen and phosphorus were followed in some experiments. Decomposition could be described as a first-order process, and the rate of decomposition was similar to that found by others using pure cultures of eucaryotic algae. Nitrogen and phosphorus never limited the decomposition process, even when the lake water was severely limited in soluble forms of these nutrients. This suggests that the bacteria responsible for decomposition can obtain all of their key nutrients for growth from the blue-green algal cells. Filtration of lake water through plankton netting that removed up to 90% of the algal biomass usually did not cause a similar decrease in oxygen demand, suggesting that most of the particulate organic matter used for respiration of the decomposing bacteria was in a small-particle fraction. Short-term oxygen demand correlated well with the particulate chlorophyll concentration of the sample, and a relationship was derived that could be used to predict community respiration of the lake from chlorophyll concentration. Kinetic analysis showed that not all analyzed components disappeared at the same rate during the decomposition process. The relative rates of decrease of the measured parameters were as follows: photosynthetic ability > algal volume > particulate chlorophyll > particulate protein. Decomposition of ¹⁴C-labeled Anabaena occurred at similar rates with aerobic epilimnetic water and with anaerobic sediment, but was considerably slower with anaerobic hypolimnetic water. Of the various genera present in the lake, Aphanizomenon and Anabaena were more sensitive to decomposition than was Microcystis. In addition to providing a general picture of the decomposition process, the present work relates to other work on sedimentation to provide a detailed picture of the fate of blue-green algal biomass in a eutrophic lake ecosystem.     

Current microalgal health food R & D activities in China

The major microalgal genera presently cultivated in China are Spirulina and Chlorella. They are initially manufactured in the form of algal biomass or extracts by the food industry. The biomass is then used for producing a variety of health products such as tablets, capsules, powder or for extracting bioactive ingredients such as beta-carotene, and phycocyanin. The algal biomass is supplemented to noodles, breads, biscuits, candies, ice cream, bean curd and other common foods as food additives so as to enhance their nutritive and health values. The extracts are mainly used to enrich liquid foods such as health drink, soft drink, tea, beer or spirits.     

Role of algae in the diet of Chironomus plumosus F. semireductus from the Bay of Quinte,Lake Ontario

The importance of algae and different algal species to the chironomid diet was investigated through examination of the guts of chironomids taken from 5 locations in Big Bay (Bay of Quinte, Lake Ontario) at 6 times during the ice-free period. A comparison of the density and condition of algal cells at the two ends of the gut provided information on the digestibility of each algal species and the algal biomass assimilated by the chironomids. Diatoms and two species of green algae were assimilated over much of the summer, but the blue green algae were digested only late in the season when their populations were aged and/or dying. In terms of energy contribution, diatoms, especially Stephanodiscus spp. and Melosira spp., were most important in May (99% of all algal biomass assimilated), August (98%), and Octobr (92%), while the blue green species, Microcystis aeruginosa, was predominant in September (76%). Only a few small greens were assimilated in June and July. The contribution of algae as a food source to chironomid energetics was small, and reached a maximum in August and September (15%–34%). It is postulated that bacteria are a more important food source.     

Evaluation of early feed access and algal extract on growth performance,organ development,gut microbiota and vaccine-induced antibody responses in broiler chickens

Hatching concepts such as on-farm hatching provide an opportunity to supply newly hatched chickens with optimal nutrition that support growth and development of a healthy gut. Brown algae contain bioactive compounds, especially laminarin and fucoidan that may improve intestinal health and immune responses. This study aimed to examine the effects of early access to feed and water posthatch and feed supplementation with algal extract rich in laminarin from Laminaria digitata, on growth performance, organ and microbiota development and antibody production. A total of 432 Ross 308 chicks were allotted to 36 rearing pens in a 2 × 3 factorial design with two hatching treatments and three dietary treatments. During chick placement, half of the pens were directly provided access to feed and water (Early) while half of the pens were deprived of feed and water for 38 h (Late). The chicks were fed three different starter diets until day 6; a wheat-soybean meal-based control diet, a diet with low inclusion of algal extract (0.057%) and a diet with high inclusion of algal extract (0.114%). Feed intake and BW were registered on pen basis at placement, days 1, 6, 12, 19, 26, 33 and 40. To induce antibody responses, all chicks were vaccinated against avian pneumovirus on day 10. Three chicks per pen were selected as focal animals and used for blood sampling on days 10 and 39. On days 6, 19, and 40, two birds per pen were killed and used for organ measurement and caecal digesta sampling for gut microbiota analysis using the Illumina Miseq PE 250 sequencing platform. Results showed that algal extract did not influence gut microbiota, gut development or vaccine-induced antibody responses. However, during the first 38 h, early-fed chicks consumed on average 19.6 g of feed and gained 27% in BW, while late-fed chicks lost 9.1% in BW which lowered BW and feed intake throughout the study (P < 0.05). Late chicks also had longer relative intestine, higher relative (g/kg BW) weight of gizzard and proventriculus but lower relative bursa weight on day 6 (P < 0.05). No effects of hatching treatment on microbiota or antibody response were detected. The microbiota was affected by age, where alpha diversity increased with age. In conclusion, this study showed that early access to feed but not algal extract improved the growth performance throughout the 40-day growing period, and stimulated early bursa development.     

Marine bacteria antagonistic to the harmful algal bloom species Alexandrium tamarense (Dinophyceae)

As part of efforts to enhance the strategies employed to manage and mitigate algal blooms and their adverse effects, algicidal bacteria have shown promise as potential suppressors of these events. Nine strains of bacteria algicidal against the toxic dinoflagellate, Alexandrium tamarense, were isolated from the East Sea area, China. Sequence analysis of 16S rDNA showed that all the algicidal bacteria belonged to the γ-proteobacteria subclass and the genera Pseudoalteromonas (strain SP31 and SP44), Alteromonas (strain DH12 and DH46), Idiomarina (strain SP96), Vibrio (strain DH47 and DH51) and Halomonas (strain DH74 and DH77). To assess the algicidal mode of these algicidal bacteria, bacterial cells and the filtrate from bacterial cultures were inoculated into A. tamarense cultures, and fluorescein diacetate vital stain was applied to monitor the growth of the algal cells. The results showed that all the algicidal bacteria exhibited algicidal activity through an indirect attack since algicidal activity was only detected in cell free supernatants but not the bacterial cells. This is the first report of bacteria from the genus Idiomarina showing algicidal activity to the toxic dinoflagellate A. tamarense and these findings would increase our knowledge of bacterial–algal interactions and the role of bacteria during the population dynamics of HABs.     

Structure and development of the style base in Abildgaardia, Bulbostylis, and Fimbristylis (Cyperaceae,Cyperoideae, Abildgaardieae)

The Abildgaardieae tribe within the family Cyperaceae comprises six or seven genera, among which Abildgaardia, Bulbostylis and Fimbristylis pose a challenge regarding their morphological delimitation. Molecular phylogenetic analyses including species of Abildgaardieae are rare, but in most of those studies, Abildgaardia and Fimbristylis appear as more closely related to each other than to the Bulbostylis genus. Duration of the style base has been one of the most widely used characters for delimiting these three genera. The style base is a persistent structure in most species of Bulbostylis and deciduous in Abildgaardia and Fimbristylis. The reasons why the style base may persist or fall off have been scarcely discussed. The assumption that abscission layers are present in the style base of all three genera and the fact that tracheids have been observed in the style base of Bulbostylis suggest that this structure might have histological complexity. In view of this, a complete ontogenetic and anatomical study of the gynoecium has been carried out for all these three genera. It turned out that the style base is histologically simple in Abildgaardia, Bulbostylis and Fimbristylis and shows similar structure and development in all three genera. The fact that the style base has a shorter duration in Abildgaardia and Fimbristylis than in Bulbostylis might be related to the lower number of sclerotised cells that make up such structures in the mature fruit of the former two genera. Abscission of the style and style base may be the result of much simpler reasons than the differentiation of an abscission layer, resulting merely from mechanical shear force effects. Differences among genera have been observed in the shape of the style base and the development of the style. The histological simplicity of the style base is consistent with the homoplastic appearance of this structure in genera that are not closely related (e.g. Rhynchospora). Because of this, while the presence of the thickened style base seems to be a synapomorphy in species of Abildgaardieae, its persistence on or detachment from the fruit might have emerged repeatedly during this clade evolution and might not be a suitable character for genera delimitation.     

Field and Laboratory Studies on Nile Phytoplankton in Egypt IV. Phytoplankton of Aswan High Dam Lake (Lake Nasser)

Seasonal, local and monthly vertical variations in chlorophyll a concentration and in qualitative and quantitative counts in Aswan High Dam Lake (AHDL) phytoplankton were followed from March 1982 to February 1984. The chlorophyll a values correlated more or less with the total phytoplankton counts. Total algal counts exhibited considerable local variations in the different seasons and tended to decrease in the most southern part of AHDL, especially during the flood period. The temporal course of algal development showed an almost inverse trend to that of dissolved nitrate-nitrogen. The possibility of nitrogen limitation of algal growth was verified. Diatoms and blue-green algae alternated in the dominance of the phytoplankton community. The genera Cyclotella and Anabaenopsis respectively were the most predominant genera among the diatoms and blue-greens and consequently in the phytoplankton community.     

Abundance,dynamics and succession of planktonic rotifers in Lake Biel,Switzerland

Twenty species of planktonic rotifers were important in Lake Biel during 1978. Eight species were present throughout the year, four species occurred only in spring and eight species in summer or autumn. Rotifer numbers attained two major maxima, one in May (19.3 10⁶ ind. m^?2) and one in August (16.5 10⁶ ind. m^?2). Predominant genera were Synchaeta, Polyarthra, Conochilus, Asplanchna and Keratella. Within the genus Synchaeta a succession of different species was observed.     

Algal assemblages associated with Stegastes sp. territories on Indo-Pacific coral reefs: Characterization of diversity and controls on growth

Herbivorous fish occupy an important niche in coral reef ecosystems. Specifically, damselfish of the genus Stegastes have been shown to have a significant impact on coral community structure and algal assemblages. This study investigated the algal communities associated with Stegastes territories of the Indo-Pacific (Fiji, Solomon Islands, and Tonga), while concurrently examining the effects of nutrient enrichment and herbivore exclusion (alone and in unison) on these communities. Results evidenced differences in species composition, percent cover, and algal growth rate between Stegastes territories and non-Stegastes sites and between control sites and treatment sites. Stegastes territories consistently displayed a greater abundance of turf algae than non-Stegastes sites; the two main genera of turf algae observed at all sites were Polysiphonia and Ceramium. Although non-Stegastes sites in Fiji, the Solomon Islands, and Tonga showed a greater percent coverage of macroalgae, they contained fewer algal species compared to Stegastes territories. In Fiji, red macroalgae decreased in the herbivore exclusion treatments, while brown macroalgae increased significantly in the herbivore exclusion and nutrient treatments. The combined effect of the herbivore exclusion and nutrient treatment at this location yielded a significantly increased turf algae growth rate compared to control sites. Growth rates of turf algae in the Solomon Islands and Tonga increased significantly in caged treatments, suggesting that damselfish of the genus Stegastes can play an important role in maintaining cropped algal beds. In summation, the results demonstrated that Stegastes sustains distinct algal assemblages which may be disrupted by reduced grazing and/or eutrophication.     

Pollen stratigraphy of coal-bearing deposits in the Neogene Jidong Basin,Heilongjiang Province,NE China: New insights on palaeoenvironment and age

The palaeoenvironment and age of coal-bearing lacustrine deposits in the Jidong Basin, Heilongjiang Province, is poorly understood. New pollen data from the Yongqing Formation and the overlying lower part of the Daqingshan Formation recovered in borehole 91-205 revealed a rich and diverse palynoflora representing approximately 70 taxa at the genus/family level. Of these taxa, Ulmus, Quercus, Carya, Liquidambar, Pinus, Tilia, Fagus, and Alnus are the main woody elements; these occur together with numerous pteridophytes, subordinate herbs, and rare algae and acritarchs. Abundant woody taxa suggest a mixed deciduous/conifer forest in the region in association with local shrubs, herbs and algal communities. Some of the pollen types, especially those of climate sensitive genera such as Ulmus, Carya, Liquidambar and Fagus, vary considerably in relative abundances, suggesting climate variability. The reflected climate shows an overall trend towards cooling or deterioration which is largely in agreement with global climate change during the Neogene.Comparisons of the pollen record with representative datasets from neighbouring areas, together with the appearance of the highly-evolved genus Artemisia, suggest that the Yongqing Formation and the lower part of the Daqingshan Formation are of Miocene age.     

Planktonic bacterial community composition of an extremely shallow soda pond during a phytoplankton bloom revealed by cultivation and molecular cloning

Böddi-szék is one of the shallow soda ponds located in the Kiskunság National Park, Hungary. In June 2008, immediately prior to drying out, an extensive algal bloom dominated by a green alga (Oocystis submarina Lagerheim) was observed in the extremely saline and alkaline water of the pond. The aim of the present study was to reveal the phylogenetic diversity of the bacterial communities inhabiting the water of Böddi-szék during the blooming event. Using two different selective media, altogether 110 aerobic bacterial strains were cultivated. According to the sequence analysis of the 16S rRNA gene, most of the strains belonged to alkaliphilic or alkalitolerant and moderately halophilic species of the genera Bacillus and Gracilibacillus (Firmicutes), Algoriphagus and Aquiflexum (Bacteroidetes), Alkalimonas and Halomonas (Gammaproteobacteria). Other strains were closely related to alkaliphilic and phototrophic purple non-sulfur bacteria of the genera Erythrobacter and Rhodobaca (Alphaproteobacteria). Analysis of the 16S rRNA gene-based clone library indicated that most of the total of 157 clone sequences affiliated with the anoxic phototrophic bacterial genera of Rhodobaca and Rhodobacter (Alphaproteobacteria), Ectothiorhodospira (Gammaproteobacteria) and Heliorestis (Firmicutes). Phylotypes related to the phylum Bacteroidetes formed the second most abundant group. Clones related to the mainly anaerobic and alkaliphilic bacterial genera of Anoxynatronum (Firmicutes), Spirochaeta (Spirochaetes) and Desulfonatronum (Deltaproteobacteria) were also abundant. Further clone sequences showed less than 95 % similarity values to cultivated species of the phyla Actinobacteria, Cyanobacteria, Deinococcus-Thermus, Fibrobacteres, Gemmatimonadetes and Lentisphaerae.     

A shift in the dominant toxin-producing algal species in central California alters phycotoxins in food webs

In California, the toxic algal species of primary concern are the dinoflagellate Alexandrium catenella and members of the pennate diatom genus Pseudo-nitzschia, both producers of potent neurotoxins that are capable of sickening and killing marine life and humans. During the summer of 2004 in Monterey Bay, we observed a change in the taxonomic structure of the phytoplankton community—the typically diatom-dominated community shifted to a red tide, dinoflagellate-dominated community. Here we use a 6-year time series (2000–2006) to show how the abundance of the dominant harmful algal bloom (HAB) species in the Bay up to that point, Pseudo-nitzschia, significantly declined during the dinoflagellate-dominated interval, while two genera of toxic dinoflagellates, Alexandrium and Dinophysis, became the predominant toxin producers. This change represents a shift from a genus of toxin producers that typically dominates the community during a toxic bloom, to HAB taxa that are generally only minor components of the community in a toxic event. This change in the local HAB species was also reflected in the toxins present in higher trophic levels. Despite the small contribution of A. catenella to the overall phytoplankton community, the increase in the presence of this species in Monterey Bay was associated with an increase in the presence of paralytic shellfish poisoning (PSP) toxins in sentinel shellfish and clupeoid fish. This report provides the first evidence that PSP toxins are present in California's pelagic food web, as PSP toxins were detected in both northern anchovies (Engraulis mordax) and Pacific sardines (Sardinops sagax). Another interesting observation from our data is the co-occurrence of DA and PSP toxins in both planktivorous fish and sentinel shellfish. We also provide evidence, based on the statewide biotoxin monitoring program, that this increase in the frequency and abundance of PSP events related to A. catenella occurred not just in Monterey Bay, but also in other coastal regions of California. Our results demonstrate that changes in the taxonomic structure of the phytoplankton community influences the nature of the algal toxins that move through local food webs and also emphasizes the importance of monitoring for the full suite of toxic algae, rather than just one genus or species.