Occurrence of saxitoxins and an anatoxin-a(s)-like anticholinesterase in a Brazilian drinking water supply

Blooms of toxic cyanobacteria are very common in Brazilian waterbodies, as a consequence of eutrophication processes. Our investigations were focused on the detection of neurotoxins during a cyanobacterial bloom in Tapacurá reservoir, which serves as a water supply for Recife city in northeastern Brazil. We also investigated the possible presence of neurotoxins in strains of Anabaena spiroides isolated from this environment. Samples were collected from March to May 2002 at the water surface and close to the dam. Limnological parameters (conductivity, pH, inorganic nutrients) and cyanobacterial abundance were measured. The samples were assayed for toxicity by mouse bioassay and acetylcholinesterase-inhibiting activity by a colorimetric method; saxitoxins (paralytic shellfish poisons) were quantified by a HPLC-FLD postcolumn derivatization method. The dominant cyanobacteria during the bloom were found to be A. spiroides, Pseudanabaena sp., Cylindrospermopsis raciborskii and Microcystis aeruginosa. The mouse bioassays showed the presence of neurotoxins during both A. spiroides and C. raciborskii dominance, whereas anticholinesterase activity was only observed during periods of A. spiroides dominance. The A. spiroides strains isolated during the study also exhibited an acetylcholinesterase inhibitor. HPLC-FLD chromatograms of bloom material extracts revealed the presence of saxitoxin, neosaxitoxin and dc-saxitoxin, probably produced by C. raciborskii.     

Abiotic factors influencing cyanobacterial bloom development in the Gulf of Finland (Baltic Sea)

Blooms of cyanobacteria are a recurrent phenomenon in the Baltic Sea, including the Gulf of Finland. The spatial extension, duration, intensity and species composition of these blooms varies widely between years. Alg@line data collected regularly from ferries as well as weather service and marine monitoring data from 1997 to 2005 are analysed to determine the main abiotic factors influencing the intensity and species composition of cyanobacterial blooms in the Gulf of Finland. It is demonstrated that the development of the Nodularia spumigena Mertens bloom is highly dependent on weather conditions such as photosynthetically active radiation and water temperature. Nutrient conditions, especially the surplus of phosphorus (according to Redfield ratio) related to the pre-bloom upwelling events in the Gulf, affect the intensity of Aphanizomenon sp. (L.) Ralfs blooms. Differences in bloom timing and duration indicate that, if the preconditions (like nutrient ratio/concentration and weather conditions) for bloom formation are favourable, then the Aphanizomenon bloom starts earlier, the overall bloom period is longer and the Nodularia peak might appear in a wider time window. Handling editor: K. Martens     

Blooms of benthic dinoflagellates of the genus Ostreopsis; an increasing and ecologically important phenomenon on temperate reefs in New Zealand and worldwide

Blooms of benthic dinoflagellates belonging to the tropical genus Ostreopsis are an increasingly common phenomenon in temperate regions worldwide. This is reflected in the rapid upsurge of publications on Ostreopsis from temperate regions since 2000. Relatively little is known about these blooms or their effects on other organisms. An unprecedented bloom of Ostreopsis siamensis occurred on shallow reefs in northern New Zealand in 2004 providing an opportunity to examine the dynamics of an O. siamensis bloom and its effect on community structuring sea urchins (Evechinus chloroticus). The bloom occurred following a period of calm sea conditions with warmer than average water temperatures. The cover of O. siamensis was highly ephemeral and strongly related to temporal and spatial variation in wave action. Blooms were most prevalent at sites protected from prevailing swells where O. siamensis covered 30–60% of the reef with the concentrations on macroalgae reaching 1.4 × 10⁶ cells g⁻¹ wet weight, some of the highest recorded worldwide. Surveys of the health of sea urchins in relation to the cover of O. siamensis suggested strong negative effects on this ecologically important herbivore and urchin densities declined by 56–60% at bloom sites over the study period. Further research is needed to examine the factors controlling the distribution and intensity of this new phenomenon, and into the ecological effects of such blooms on marine communities and the potential mechanisms responsible.     

Effects of winds, tides and river water runoff on the formation and disappearance of the Alexandrium tamarense bloom in Hiroshima Bay, Japan

Effects of winds, tides and river water runoff on the formation and disappearance of Alexandrium tamarense blooms in Hiroshima Bay, Japan were investigated using data from March to June of 1992–1998. The north wind at the initial growth phase of A. tamarense appeared to have prevented bloom formation by dispersing the organism offshore and/or through turbulent mixing. The decrease in the cell density at the end of the blooms was significantly affected by tidal mixing, indicating that the turbulent mixing induced by tidal excursions may be one of the factors terminating the bloom. Box model analyses applied to the data collected from the observations in 1996 and 1997 showed that river water runoff apparently dispersed the bloom, implying that stratification of the water column due to river water runoff is not necessary for the bloom formation. In conclusion, calm conditions with less wind and tidal mixing along with less river water runoff are considered to be important for the formation of the A. tamarense bloom in Hiroshima Bay, Japan.     

Temporal evolution and vertical stratification of Microcystis toxic potential during a first bloom event

In order to study the setup of a Microcystis bloom and the evolution of its toxic potential, we studied the temporal and vertical variations in Microcystis aeruginosa abundance, microcystins (MC) concentrations (intracellular and extracellular), and the relative proportion of potentially microcystin-producing cells (MC-producing cells) in relation to physicochemical parameters in the recently setup Moroccan reservoir “Yaacoub Al Mansour.” The Microcystis bloom appeared relatively late in the season and was associated with a low proportion of MC-producing cells in the water surface layer, probably related to non-limiting nutrient concentrations. Interestingly, the setup of the bloom leads to a vertical gradient, showing a decrease in Microcystis cell abundance inversely coupled with an increase in the proportion of MC-producing cells. Thus, this can be the result of the growth where non-MC-producing cells remain in the lighted water layer easier than MC-producing ones. Nevertheless, parameters other than light intensity may influence the toxic potential of bloom as no vertical pattern was observed concerning microcystins cellular quotas. The high microcystins concentrations measured in the deep water layer have also proved the importance of considering the deep part of aquatic ecosystem in the management of health risks associated with cyanobacterial proliferations.     

A Catastrophe Model for Water Bloom Prediction: A Case Study of China's Lake Chaohu

Using a case study of Lake Chaohu, the fifth largest lake in China, we constructed a cusp model for water bloom prediction that used TP (total phosphorus), T (temperature), Chla (chlorophyll-a), and DO (dissolved oxygen). These four parameters were assumed to be the most important factors in eutrophication and water bloom of the lake. The model was found to be accurate, because its relative error was around 10%. What is more convincing, according to the catastrophe discriminant of the cusp model, it could be judged that a discontinuous jump of the aquatic ecosystem occurred in July 2004, in Lake Chaohu. This conclusion is consistent with the fact that water blooms arose in August 2004. The cusp model also showed satisfactory precision when applied to forecast the eutrophication trend and prediction of water bloom in Lake Chaohu in 2005. The case study found that water bloom brought on by eutrophication can be fit and predicted by a catastrophe model. We suggest that catastrophe models would be a constructive approach to forecast and judge the outbreak of water bloom in lakes. In addition, by constructing and studying such catastrophe models, lake managers would be able to simulate the effects of different protection and mitigation projects and enrich the scientific basis for the optimization of these projects as well.     

Occurrence of cyanobacterial blooms in the baltic sea in relation to environmental conditions

Cyanobacterial blooms occur regularly in summer in central parts of the Baltic Sea. They are mainly composed of Aphanizomenon sp. and Nodularia spumigena. Both species have almost similar ecological requirements and can roughly be considered a uniform functional group. In order to identify factors that might favour bloom development, water quality data from monitoring programmes were compared with bloom distribution. A salinity from 3.8 to 11.5 PSU proved important for the spatial distribution of the bloom development. The bloom's onset was triggered by temperatures approximating 16°C provided that global radiation was > 120 W/m² (daily mean) and wind speed was < 6 m/s. Nutrient concentrations decreased immediately before the bloom. The bloom's development ceased with poor weather conditions characterized by low irradiation or high wind speed.     

Detection of <Emphasis Type="Italic">Planktothrix rubescens</Emphasis> (Cyanobacteria) associated with microcystin production in a freshwater reservoir

So far, the presence of microcystins in Portuguese freshwater resources has always been attributed to the bloom-forming cyanobacteria Microcystis aeruginosa. In 2005, however, microcystins were detected at the Beliche reservoir (Algarve, South Portugal), following the development of a bloom dominated by Planktothrix rubescens. The identity of the causative organism was confirmed by combining both morphological and 16S rRNA gene sequence analysis. Its ability to produce microcystins was confirmed by HPLC and MALDI-TOF MS. Unlike M. aeruginosa that usually accumulates near the water surface, P. rubescens found at the Beliche reservoir accumulated only at deep water levels. Being invisible from the surface, the occurrence of toxic P. rubescens in freshwater resources requires special attention when designing site inspection and sampling procedures for the correct risk assessment and management of cyanobacterial blooms in the field. Handling editor: D. Hamilton     

Modelling of autumn plankton bloom dynamics

A simple system of parametrically forced ordinary differentialequations is used to model autumn phytoplankton blooms in temperateoceans by a mechanism involving deepening of the upper mixedlayer. Blooms are triggered provided the increase in nutrientsin the mixed layer is rapid within the first few days of deepeningand provided light-limited phytoplankton growth rate is relativelyhigh. Blooms exist as transient trajectories between quasi-equilibriumstates, rather than as bifurcations of steady states; thereforevery gradual deepening cannot trigger blooms. Very rapid deepeningalso prevents blooms due to the deleterious effect on phytoplanktongrowth rate. The mechanisms identified by this simple modelare vindicated by considering alternative grazing and deepeningregimes and by comparison with a more ecologically complex model(Fasham, 1993, in The Global Carbon Cycle, Springer-Verlag).Modelled estimates of primary productivity from both the simplemodel and the complex model parameterized for Ocean WeatherStation ‘India’ are around 0.5 g C m^–2 day^–1during the autumn bloom, therefore comprising a significantcomponent of annual production in temperate areas.     

A Phytoplankton Bloom in Shallow Divor Reservoir (Portugal)—The Importance of Internal Nutrient Loading

The development of a heavy phytoplankton bloom (chl. a = 360 mg/m³), which occurred in the summer 1983 in a shallow reservoir, Divor, is described. The study shows that remobilization of phosphate from the sediment was initiating the phytoplankton bloom. This was confirmed not only by calculations of the change in iron-phosphate pool, but also supported by sorption experiments carried out with the sediment. It is discussed that turbidity of the water due to suspended matter caused the reduction in standing stock of phytoplankton to approx. 50 mg chl. a/m³ in late summer.     

The effects of the flood cycle on the diversity and composition of the phytoplankton community of a seasonally flooded Ramsar wetland in Bangladesh

Freshwater wetlands in Bangladesh are strongly influenced by the monsoons and the annual flood cycle has measurable impacts on the abiotic and biotic components of these ecosystems. The northeastern Haor Basin of Bangladesh is particularly rich in seasonally flooded freshwater wetlands that support a wide diversity of flora and fauna. These wetlands are of great importance to the local economy due to the abundance of rich floodplain fisheries. Little is known about the phytoplankton communities of these wetlands that are known to be linked with zooplankton and fish productivity. We investigated the seasonal variation in the diversity and abundance of phytoplankton assemblages in Tanguar Haor, a Ramsar wetland in northeastern Bangladesh during the period of inundation (June–December). A total of 107 genera of phytoplankton representing five classes were recorded. Blooms of Microcystis dominated the phytoplankton community throughout the study period but were particularly acute during the early part of the high water period. Among the Bacillariophyceae, Melosira was the most dominant, reaching bloom proportions early in the high water period. Factor analysis of physicochemical variables separated the flood cycle into four distinct periods: early high water, mid high water, late high water and low water periods. Phase of the flood cycle, nutrient availability, the physicochemical variables combined with the dominance of Microcystis seemed to be important in controlling the abundance, diversity and dynamics of the phytoplankton genera. The abundance of genera of desmids and some Bacillariophyceae is indicative of the relatively unpolluted conditions of Tanguar Haor.     

The role of microcystins in heavy cyanobacterial bloom formation

The presence of high microcystin concentrations in cyanobacterialblooms additionally affects species diversity. Blooms with hightoxin contents can reach higher cell densities, which is alsodemonstrated by microcystin cell contents. In vitro experimentsshow that microcystins influence phytoplankton proliferation.The action is strongly dependent on the phytoplankton speciestested and light conditions. We propose that the environmentalimpact of different microcystins depends on their enzymaticinhibition activity and thus could not be measured merely onthe basis of their toxicity to vertebrate species. Their rolein heavy cyanobacterial bloom and scum formation is discussed,as well as their impact on the massive proliferation of otherspecies following toxic cyanobacterial bloom degradation.     

An unusual bloom of the dinoflagellate Akashiwo sanguinea off the central Oregon, USA, coast in autumn 2009

An algal bloom caused by the dinoflagellate Akashiwo sanguinea was observed in October–November 2009 along the central Oregon coast (44.6°N), off Newport, Oregon, U.S.A. In this paper, the conditions are described which led to the development and demise of this bloom. The bloom was observed for 1 month from 5-October until 4-November with the peak of abundance on 19-October (347,615 cells L⁻¹). The A. sanguinea bloom followed September blooms of the diatoms Pseudo-nitzschia spp, Chaetoceros debilis, and the dinoflagellate Prorocentrum gracile. The bloom occurred when nitrate and silicate concentrations were <2 μM and <8 μM, respectively, and when the water column was stratified. This A. sanguinea dinoflagellate bloom event was closely related to the anomalous upwelling conditions in 2009: upwelling ceased early, at the end of August, whereas a normal upwelling continues into early October. This relaxation extended to near the end of September as a prolonged downwelling event, but then active upwelling reappeared in October and November. The explanation for the occurrence of the A. sanguinea bloom in October may be related to a combination of a prior diatom bloom, a stratified water column with low nutrient concentration in September, and an active upwelling event in October. As for the ultimate source of the cells, the hypothesis is that the seed stock for the A sanguinea bloom off Oregon was southward transport of cells from the Washington coast where a massive bloom of A. sanguinea was first observed in September 2009.     

Development of Anabaena blooms in a small reservoir with dense sediment akinete population, with special reference to temperature and irradiance

The development of Anabaena ucrainica blooms in a small agriculturalreservoir was monitored in 1998 and 1999. In the reservoir,numerous Anabaena akinetes were found in all regions of thesediment analyzed, with an average cell density in the uppermostlayer (0–2 cm) of 1.5 x 10⁴ cm^-3. Anabaena ucrainica filamentnumbers began to increase exponentially in mid-May 1998 andin late April 1999, when the water temperature exceeded 15°C.The average in situ net growth rate was 0.18 day^-1 as measuredby filament numbers. The effect of temperature on germinationof the akinetes was investigated using Anabaena akinetes takenfrom the reservoir sediment. High germination percentages wereobserved at temperatures between 14 and 23°C; however, theAnabaena akinetes did not germinate without irradiance. Growthexperiments using an axenic culture of A. ucrainica isolatedfrom the reservoir showed that an increase in incubation temperatureto 26°C resulted in a rise in the specific growth rate.Consequently, it was hypothesized that temperature increasescould similarly enhance the growth rate of A. ucrainica duringbloom development. Furthermore, judging from the in situ growthrate of A. ucrainica, initial inocula arising from dense akinetepopulations in the sediment would advance bloom formation andcould enhance the relative probability of Anabaena bloom formation.     

Pseudo‐nitzschia blooms,domoic acid,and related California sea lion strandings in Monterey Bay,California

Blooms of the toxin‐producing diatom Pseudo‐nitzschia commonly occur in Monterey Bay, California, resulting in sea lion mortality events. The links between strandings of California sea lions suffering from domoic acid (DA) toxicity, toxic cell numbers, and their associated DA concentration in Monterey Bay and in sea lion feces were examined from 2004 to 2007. While Pseudo‐nitzschia toxic cells and DA concentrations were detectable in the water column most of the time, they were often at low levels. A total of 82 California sea lions were found stranded in the Bay between 2004 and 2007 with acute or chronic signs associated with DA poisoning. The highest number with detectable DA in feces occurred in April 2007 and corresponded with the presence of a highly toxic bloom in the Bay. Higher DA levels occurred in feces from sea lions stranding with acute toxicosis and lower concentrations in feces of sea lions exhibiting signs of chronic DA poisoning or not exhibiting any neurologic signs. Results indicated that sea lions are likely exposed to varying levels of DA through their prey throughout the year, often at sublethal doses that may contribute to a continued increase in the development of chronic neurologic sequelae.     

Harmful algal blooms: causes,impacts and detection

Blooms of autotrophic algae and some heterotrophic protists are increasingly frequent in coastal waters around the world and are collectively grouped as harmful algal blooms (HABs). Blooms of these organisms are attributed to two primary factors: natural processes such as circulation, upwelling relaxation, and river flow; and, anthropogenic loadings leading to eutrophication. Unfortunately, the latter is commonly assumed to be the primary cause of all blooms, which is not the case in many instances. Moreover, although it is generally acknowledged that occurrences of these phenomena are increasing throughout the world's oceans, the reasons for this apparent increase remain debated and include not only eutrophication but increased observation efforts in coastal zones of the world. There is a rapidly advancing monitoring effort resulting from the perception of increased impacts from these HABs, manifested as expanding routine coastal monitoring programs, rapid development and deployment of new detection methods for individual species, toxins, and toxicities, and expansion of coastal modeling activities towards observational forecasts of bloom landfall and eventually bloom prediction. Together, these many efforts will provide resource managers with the tools needed to develop effective strategies for the management and mitigation of HABs and their frequently devastating impacts on the coastal environment.     

Quantified distribution of diatoms during the stratified [2pt] period of Boadella reservoir

We collected data and samples, from June to November of 1999 and 2000, to in situ quantify the abundance of phytoplankton in Boadella reservoir. Samples were taken at different stations along the reservoir and diatoms were persistent in the epilimnion and were the main phytoplankton component, with a peak of abundance up to 5 10⁵ particles ml^–1. The diatom growth during the initiation of the summer bloom was high in the reservoir upstream concurrent with maximum Chlorophyll a concentrations. A delay in the onset of the diatom bloom, together with lower values of the volume concentration, was found in 1999 compared to the results in 2000 and was attributed to the different stratification of the reservoir as a result of meteorological conditions. The diatom population sank from the epilimnion by sedimentation and formed aggregates that accumulated at the bottom of the epilimnion. Sedimentation to the hypolimnion occurred at the end of the bloom, where peaks of Chlorophyll a were found.     

Blooms of benthic dinoflagellates of the genus Ostreopsis; an increasing and ecologically important phenomenon on temperate reefs in New Zealand and worldwide

Blooms of benthic dinoflagellates belonging to the tropical genus Ostreopsis are an increasingly common phenomenon in temperate regions worldwide. This is reflected in the rapid upsurge of publications on Ostreopsis from temperate regions since 2000. Relatively little is known about these blooms or their effects on other organisms. An unprecedented bloom of Ostreopsis siamensis occurred on shallow reefs in northern New Zealand in 2004 providing an opportunity to examine the dynamics of an O. siamensis bloom and its effect on community structuring sea urchins (Evechinus chloroticus). The bloom occurred following a period of calm sea conditions with warmer than average water temperatures. The cover of O. siamensis was highly ephemeral and strongly related to temporal and spatial variation in wave action. Blooms were most prevalent at sites protected from prevailing swells where O. siamensis covered 30–60% of the reef with the concentrations on macroalgae reaching 1.4 × 10⁶ cells g⁻¹ wet weight, some of the highest recorded worldwide. Surveys of the health of sea urchins in relation to the cover of O. siamensis suggested strong negative effects on this ecologically important herbivore and urchin densities declined by 56–60% at bloom sites over the study period. Further research is needed to examine the factors controlling the distribution and intensity of this new phenomenon, and into the ecological effects of such blooms on marine communities and the potential mechanisms responsible.     

Abundance,population structure and vertical distribution of dominant calanoid copepods on the eastern Weddell Sea shelf during a spring phytoplankton bloom

The main emphasis of this study was to analyse the short-term development of abundance, population structure and vertical distribution of the dominant calanoid copepods during a phytoplankton bloom in the coastal area of the eastern Weddell Sea in December 2003. Microcalanus pygmaeus was by far the most abundant calanoid species. Metridia gerlachei, Ctenocalanus citer, Calanoides acutus, Calanus propinquus and the ice-associated Stephos longipes were also present in considerable proportions. The observed changes in the population characteristics and parameters of these species are described in detail and discussed in the context of the spring phytoplankton bloom. A conspicuous event occurring during the final stage of the study was the development of a strong storm. While the results suggest that this storm did not have any considerable influence on the populations of all other investigated copepod species, it very likely caused pronounced changes in the S. longipes population present in the water column. Before the storm, S. longipes was found primarily in the upper 100 m of the water column, and its population was dominated by adults (mean proportion = 41%) and the copepodite stage I (mean proportion = 30%). After the storm, the abundance increased considerably, and the copepodite stage I contributed by far the largest proportion (53%) of the total population indicating that the early copepodite stages probably had been released from the sea ice into the under ice water layer due to ice break-up and ice melt processes caused by the storm.     

A comparison of N and C uptake during brown tide (Aureococcus anophagefferens) blooms from two coastal bays on the east coast of the USA

Blooms of the brown tide pelagophyte, Aureococcus anophagefferens, have been reported in coastal bays along the east coast of the USA for nearly two decades. Blooms appear to be constrained to shallow bays that have low flushing rates, little riverine input and high salinities (e.g., >28). Nutrient enrichment and coastal eutrophication has been most frequently implicated as the cause of A. anophagefferens and other blooms in coastal bays. We compare N and C dynamics during two brown tide blooms, one in Quantuck Bay, on Long Island, NY in 2000, and the other in Chincoteague Bay, at Public Landing, MD in 2002, with a physically similar site in Chincoteague Bay that did not experience a bloom. We found that the primary forms of nitrogen (N) taken up during the bloom in Quantuck Bay were ammonium and dissolved free amino acids (DFAA) while the primary form of N fueling production at both sites in Chincoteague Bay was urea. At both Chincoteague sites, amino acid carbon (C) was taken up while urea C was not. Even though A. anophagefferens has the ability to take up organic C, during the bloom at Chincoteague Bay, photosynthetic uptake of bicarbonate was the dominant pathway of C acquisition by the >1.2 μm size fraction during the day. C uptake by cells <5.0 μm was insufficient to meet cellular C demand based on the measured N uptake rates and the C:N ratio of particulate material. While cells >1.2 μm did not take up much organic C during the day, smaller cells (>0.2 μm) did. Peptide hydrolysis appeared to play an important role in mobilizing organic matter in Quantuck Bay, where amino acids contributed substantially to N and C uptake, but not in Chincoteague Bay. Dissolved organic N (DON), dissolved organic C (DOC) concentrations and the DOC/DON ratio were higher and total dissolved inorganic N (DIN) concentrations were lower at the bloom site in Chincoteague Bay than at the nonbloom site in the same bay. We conclude that A. anophagefferens is capable of using a wide variety of N and C compounds, and that nutrient inputs, biotic interactions and the dominant recycling pathways determine which compounds are available and which metabolic pathways are active at a particular site.