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Algal Blooms (algal + bloom)
Kinds of Algal Blooms Selected AbstractsPOSITIVE FEEDBACK AND THE DEVELOPMENT AND PERSISTENCE OF ECOSYSTEM DISRUPTIVE ALGAL BLOOMS,JOURNAL OF PHYCOLOGY, Issue 5 2006William G. Sunda Harmful algal blooms (HABs) have occurred with increasing frequency in recent years with eutrophication and other anthropogenic alterations of coastal ecosystems. Many of these blooms severely alter or degrade ecosystem function, and are referred to here as ecosystem disruptive algal blooms (EDABs). These blooms are often caused by toxic or unpalatable species that decrease grazing rates by planktonic and benthic herbivores, and thereby disrupt the transfer of nutrients and energy to higher trophic levels, and decrease nutrient recycling. Many factors, such as nutrient availability and herbivore grazing have been proposed to separately influence EDAB dynamics, but interactions among these factors have rarely been considered. Here we discuss positive feedback interactions among nutrient availability, herbivore grazing, and nutrient regeneration, which have the potential to substantially influence the dynamics of EDAB events. The positive feedbacks result from a reduction of grazing rates on EDAB species caused by toxicity or unpalatability of these algae, which promotes the proliferation of the EDAB species. The decreased rates also lower grazer-mediated recycling of nutrients and thereby decrease nutrient availability. Since many EDAB species are well-adapted to nutrient-stressed environments and many exhibit increased toxin production and toxicity under nutrient limitation, positive feedbacks are established which can greatly increase the rate of bloom development and the adverse effects on the ecosystem. An understanding of how these feedbacks interact with other regulating factors, such as benthic/pelagic nutrient coupling, physical forcing, and life cycles of EDAB species provides a substantial future challenge. [source] PRELIMINARY STUDIES OF SEASONALITY, ECOLOGY, AND SPECIES COMPOSITION OF ULVOID ALGAL BLOOMS IN WASHINGTON STATEJOURNAL OF PHYCOLOGY, Issue 2000T.A. Nelson Blooms of green macroalgae can devastate important finfish and shellfish habitats. Ulvaria obscura, a relatively unstudied green alga, is a major contributor to these blooms in the San Juan Islands, Washington State, USA. The biomass and productivity of this and other ulvoid algae were measured seasonally for two years. Experiments comparing the growth rates, responses to desiccation, photoacclimation, and grazer preference of U. obscura and Ulva fenestrata were conducted. Ulvaria blooms tended to occur in the subtidal while Ulva blooms were often intertidal. Both genera bloomed between late June and September. Despite their superficial similarity, Ulvaria and Ulva display markedly different physiological and ecological responses. Ulva was capable of faster growth, had higher rates of photosynthesis, and was more desiccation tolerant than Ulvaria. Ulvaria, however, appears to be more resistant to grazing than Ulva. [source] 147 Controlling Harmful Algal Blooms Through Clay FlocculationJOURNAL OF PHYCOLOGY, Issue 2003M. R. Sengco The potential use of clays to control harmful algal blooms (HABs) has been explored in East Asia, Australia, the United States, and Sweden. In Japan and South Korea, minerals such as montmorillonite, kaolinite, and yellow loess, have already been used in the field effectively, to protect fish mariculture from Cochlodinium spp. and other blooms. Cell removal occurs through the flocculation of algal and mineral particles, leading to the formation of larger aggregates (i.e. marine snow), which rapidly settle and further entrain cells during their descent. In the U.S., several clays and clay-rich sediments have shown high removal abilities (e.g. >80% cell removal efficiency) against Karenia brevis, Heterosigma akashiwo, Pfiesteria piscicida and Aureococcus anophagefferens. In some cases, the removal ability of certain clays was further enhanced with chemical flocculants, such as polyaluminum chloride (PAC), to increase their adhesiveness. However, cell removal was also affected by bloom concentration, salinity, and mixing. Cell mortality was observed after clay addition, and increased with increasing clay concentration, and prolonged exposure to clays in the settled layer. Mesocosm, field enclosure, and flume experiments were also conducted to address cell removal with increasing scale and flow, water-column impacts, and the possible benthic effects from clay addition. Results from these studies will be presented, especially those in regards to water quality, seawater chemistry, bottom erodibility and faunal impacts in the benthos. At this time, clay dispersal continues to be a promising method for controlling HABs and mitigating their impacts based on existing information and experimental data. [source] Linking the composition of bacterioplankton to rapid turnover of dissolved dimethylsulphoniopropionate in an algal bloom in the North SeaENVIRONMENTAL MICROBIOLOGY, Issue 5 2001Mikhail V. Zubkov The algal osmolyte, dimethylsulphoniopropionate (DMSP), is abundant in the surface oceans and is the major precursor of dimethyl sulphide (DMS), a gas involved in global climate regulation. Here, we report results from an in situ Lagrangian study that suggests a link between the microbially driven fluxes of dissolved DMSP (DMSPd) and specific members of the bacterioplankton community in a North Sea coccolithophore bloom. The bacterial population in the bloom was dominated by a single species related to the genus Roseobacter, which accounted for 24% of the bacterioplankton numbers and up to 50% of the biomass. The abundance of the Roseobacter cells showed significant paired correlation with DMSPd consumption and bacterioplankton production, whereas abundances of other bacteria did not. Consumed DMSPd (28 nM day,1) contributed 95% of the sulphur and up to 15% of the carbon demand of the total bacterial populations, suggesting the importance of DMSP as a substrate for the Roseobacter -dominated bacterioplankton. In dominating DMSPd flux, the Roseobacter species may exert a major control on DMS production. DMSPd turnover rate was 10 times that of DMS (2.7 nM day,1), indicating that DMSPd was probably the major source of DMS, but that most of the DMSPd was metabolized without DMS production. Our study suggests that single species of bacterioplankton may at times be important in metabolizing DMSP and regulating the generation of DMS in the sea. [source] Anatoxin-a toxin in the cyanobacterium Planktothrix rubescens from a fishing pond in northern ItalyENVIRONMENTAL TOXICOLOGY, Issue 3 2004Emanuela Viaggiu Abstract A heavy algal bloom occurring in a fishing pond in northern Italy full of Salmo trutta was examined for algae taxonomy and toxic production. The dominant algal species (98%) was identified as the cyanobacterium Planktothrix rubescens (D.C. ex GOMONT) Komarek Anagnostidis, based on morphological examination, and it was revealed to be toxic in mouse and Vibrio fischeri bioassays. The toxin was identified as anatoxin-a using high-performance liquid chromatography and confirmed using liquid chromatography,mass spectrometry (LC-MS). The mouse bioassay gave signs of poisoning, as previously reported for anatoxin-a. The LC-MS confirmed the presence of an anatoxin-a peak at m/z 166 (M+H+). The content of toxin in the field population was estimated at 12.13 ,g/g of fresh cells. The bloom was sustained by the very high N/P ratio in the water. This is the first report in Italy of an anatoxin-a-producing Planktothrix rubescens population. © 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 191,197, 2004. [source] Temporal Coherence of Chlorophyll a during a Spring Phytoplankton Bloom in Xiangxi Bay of Three-Gorges Reservoir, ChinaINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 6 2009Yao-Yang Xu Abstract Algal bloom phenomenon was defined as "the rapid growth of one or more phytoplankton species which leads to a rapid increase in the biomass of phytoplankton", yet most estimates of temporal coherence are based on yearly or monthly sampling frequencies and little is known of how synchrony varies among phytoplankton or of the causes of temporal coherence during spring algal bloom. In this study, data of chlorophyll a and related environmental parameters were weekly gathered at 15 sampling sites in Xiangxi Bay of Three-Gorges Reservoir (TGR, China) to evaluate patterns of temporal coherence for phytoplankton during spring bloom and test if spatial heterogeneity of nutrient and inorganic suspended particles within a single ecosystem influences synchrony of spring phytoplankton dynamics. There is a clear spatial and temporal variation in chlorophyll a across Xiangxi Bay. The degree of temporal coherence for chlorophyll a between pairs of sites located in Xiangxi Bay ranged from ,0.367 to 0.952 with mean and median values of 0.349 and 0.321, respectively. Low levels of temporal coherence were often detected among the three stretches of the bay (Down reach, middle reach and upper reach), while high levels of temporal coherence were often found within the same reach of the bay. The relative difference of DIN between pair sites was the strong predictor of temporal coherence for chlorophyll a in down and middle reach of the bay, while the relative difference in Anorganic Suspended Solids was the important factor regulating temporal coherence in middle and upper reach. Contrary to many studies, these results illustrate that, in a small geographic area (a single reservoir bay of approximately 25 km), spatial heterogeneity influence synchrony of phytoplankton dynamics during spring bloom and local processes may override the effects of regional processes or dispersal. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The epidemiology of Argulus spp. (Crustacea: Branchiura) infections in stillwater trout fisheriesJOURNAL OF FISH DISEASES, Issue 4 2006N G H Taylor Abstract Problem infections caused by species of the crustacean ectoparasite, Argulus, in UK stillwater trout fisheries appear to have increased in recent years. A cross-sectional study of 77 such fisheries was conducted to establish the perceived problem and the extent and severity of this problem, and to identify associated risk factors. An interview-based study was conducted in 2001 using a standardized questionnaire based on the management and infection status of each fishery in the previous year. Logistic regression was used to identify potential risk factors. Argulus spp. were perceived to cause economic losses in infected fisheries through a reduction in the number of anglers due to reduced aesthetic appeal and catchability of fish. Of the sites studied, 29% experienced such a problem infection in 2000. Argulus foliaceus was identified in all but one case and was found to be widely distributed throughout the UK. The remaining case was identified as Argulus coregoni. Three risk factors were associated with problem infections: the presence of an algal bloom, slow rates of stock turnover and whether water level dropped by <1 m during the summer months. [source] 162 Interactions Between Planktonic Microalgae and Protozoan GrazersJOURNAL OF PHYCOLOGY, Issue 2003U. Tillmann For an algal bloom to develop, the growth rate of the bloom-forming species must exceed the sum of all loss processes. Among these loss processes, grazing is generally believed to be one of the more important factors. Based on numerous field studies it is now recognised that microzooplankton are dominant consumers of phytoplankton in both open ocean and coastal waters. Heterotrophic protists, a major component of microzooplankton communities, constitute a vast complex of diverse feeding strategies and behaviour which allow them access to even the larger phytoplankton species. A number of laboratory studies have shown the capability of different protistan species to feed and grow on bloom forming algal species. Because of short generation times, their ability for fast reaction to short-term variation in food conditions enables phagotrophic protists to fulfil the function of a heterotrophic buffer, which might balances the flow of matter in case of phytoplankton blooms. The importance of grazing as control of microalgae becomes most apparent by its failure; if community grazing controls initial stages of bloom development, there simply is no bloom. However, if a certain algal species is difficult to graze, e.g. due to specific defence mechanisms, a reduced grazing pressure will certainly favour bloom development. The present contribution will provide a general overview on the interactions between planktonic microalgae and protozoan grazers with special emphasis on species-specific interactions and algal defence strategies against protozoan grazers. [source] Impact of Copper Sulfate on Plankton in Channel Catfish Nursery PondsJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 1 2009Charles C. Mischke Many fish culturists are interested in applying copper sulfate pentahydrate (CSP) to channel catfish, Ictalurus punctatus, nursery ponds as a prophylactic treatment for trematode infection and proliferative gill disease by killing snails and Dero sp., respectively, before stocking fry. However, copper is an algaecide and may adversely affect phytoplankton and zooplankton populations. We evaluated the effects of prophylactic use of copper sulfate in catfish nursery ponds on water quality and phytoplankton and zooplankton populations. In 2006, treatments of 0 mg/L CSP, 3 mg/L CSP (0.77 mg/L Cu), and 6 mg/L CSP (1.54 mg/L Cu) were randomly assigned to 0.04-ha ponds. In 2007, only treatments of 0 and 3 mg/L CSP were randomly assigned to the 16 ponds. Ponds treated with CSP had significantly higher pH and significantly lower total ammonia concentrations. Treatment of both CSP rates increased total algal concentrations but reduced desirable zooplankton groups for catfish culture. CSP has been shown to be effective in reducing snail populations at the rate used in this study. CSP treatment also appears to be beneficial to the algal bloom, shifting the algal population to green algae and increasing total algal biomass within 1 wk after CSP treatment. Although zooplankton populations were adversely affected, populations of important zooplankton to catfish fry began rebounding 6,12 d after CSP treatment. Therefore, if CSP is used to treat catfish fry ponds of similar water composition used in this study, fry should not be stocked for about 2 wk after CSP application to allow time for the desirable zooplankton densities to begin increasing. [source] Detection of bacteria associated with harmful algal blooms from coastal and microcosm environments using electronic microarraysENVIRONMENTAL MICROBIOLOGY, Issue 3 2007Edward A. Barlaan Summary With the global expansion of harmful algal blooms (HABs), several measures, including molecular approaches, have been undertaken to monitor its occurrence. Many reports have indicated the significant roles of bacteria in controlling algal bloom dynamics. Attempts have been made to utilize the bacteria/harmful algae relationship in HAB monitoring. In this study, bacterial assemblages monitored during coastal HABs and bacterial communities in induced microcosm blooms were investigated. Samples were analysed using denaturing gradient gel electrophoresis (DGGE) of the 16S rRNA gene. DGGE bands with peculiar patterns before, during, and after algal blooms were isolated and identified. Probes for six ribotypes representing organisms associated with Chatonella spp., Heterocapsa circularisquama, or Heterosigma akashiwo were used for analysis on NanoChip electronic microarray. In addition, a new approach using cultured bacteria species was developed to detect longer (533 bp) polymerase chain reaction-amplified products on the electronic microarray. The use of fluorescently labelled primers allowed the detection of individual species in single or mixed DNA conditions. The developed approach enabled the detection of the presence or absence and relative abundance of the HAB-related ribotypes in coastal and microcosm blooms. This study indicates the ability of electronic microarray platform to detect or monitor bacteria in natural and induced environments. [source] Sources and transport of algae and nutrients in a Californian river in a semi-arid climateFRESHWATER BIOLOGY, Issue 12 2007NOBUHITO OHTE Summary 1. To elucidate factors contributing to dissolved oxygen (DO) depletion in the Stockton Deep Water Ship Channel in the lower San Joaquin River, spatial and temporal changes in algae and nutrient concentrations were investigated in relation to flow regime under the semiarid climate conditions. 2. Chlorophyll- a (chl- a) concentration and loads indicated that most algal biomass was generated by in-stream growth in the main stem of the river. The addition of algae from tributaries and drains was small (c.15% of total chl- a load), even though high concentrations of chl- a were measured in some source waters. 3. Nitrate and soluble-reactive phosphorus (SRP) were available in excess as a nutrient source for algae. Although nitrate and SRP from upstream tributaries contributed (16.9% of total nitrate load and 10.8% of total SRP load), nutrients derived from agriculture and other sources in the middle and lower river reaches were mostly responsible (20.2% for nitrate and 48.0% for SRP) for maintaining high nitrate and SRP concentrations in the main stem. 4. A reduction in nutrient discharge would attenuate the algal blooms that accelerate DO depletion in the Stockton Deep Water Ship Channel. The N : P ratio, in the main stem suggests that SRP reduction would be a more viable option for algae reduction than nitrogen reduction. 5. Very high algal growth rates in the main stem suggest that reducing the algal seed source in upstream areas would also be an effective strategy. [source] Small-scale fluid motion mediates growth and nutrient uptake of Selenastrum capricornutumFRESHWATER BIOLOGY, Issue 6 2006T. A. WARNAARS Summary 1. A fluid-flow reactor using submersible speakers was constructed to generate small-scale fluid motion similar to conditions measured in open water environments; flow was quantified by particle image velocimetry. Additionally a Couette-type rotating cylinder was used to generate shear flows; flow was quantified using an optical hotwire probe and torque measurements. Growth rates of the green alga Selenastrum capricornutum were determined from changes in cell counts and viability was tested using the fluorogenic probe fluoresceine diacetate. 2. Evidence that fluid motion directly affects growth rates was obtained as a significant difference between growth in a moving versus non-moving fluid. A near 2-fold increase in growth rate was achieved for an energy dissipation rate of , = 10,7 m2 s,3; a rate common in lakes and oceans. The onset of the viability equilibrium, identified as the day of the test period when the number of active cells equalled non-active cells, was delayed by 2 days for moving fluid conditions as compared with a non-moving fluid. 3. Nutrient uptake was determined by a decrease in the bulk fluid concentration and cellular phosphorus concentration was also estimated. The thickness of the diffusive sublayer surrounding a cell, a zone dominated by molecular diffusion, was estimated. Increasing fluid motion was found to decrease the thickness of this layer. The Sherwood number (ratio of total mass flux to molecular mass flux) showed that advective flux surrounding cells dominated molecular diffusion flux with regard to Péclet numbers (ratio of advective transport to molecular diffusion transport). Fluid motion facilitated uptake rates and resulted in increased growth rates, compared with no-flow conditions. The rate-of-rotation and the rate-of-strain in a moving fluid equally mediated the diffusive sublayer thickness surrounding the cells. Our study demonstrates that small-scale fluid motion mediates algal growth kinetics and therefore should be included in predictive models for algal blooms. [source] Effects of experimentally induced cyanobacterial blooms on crustacean zooplankton communitiesFRESHWATER BIOLOGY, Issue 2 2003Anas Ghadouani SUMMARY 1.,Large in situ enclosures were used to study the effects of experimentally induced cyanobacterial blooms on zooplankton communities. A combination of N and P was added to shallow (2 m) and deep enclosures (5 m) with the goal of reducing the TN : TP ratio to a low level (,5 : 1) to promote cyanobacterial growth. After nutrient additions, high biomass of cyanobacteria developed rapidly in shallow enclosures reaching levels only observed during bloom events in eutrophic lakes. 2.,In the shallow enclosures, particulate phosphorus (PP) was on average 35% higher in comparison with deep enclosures, suggesting that depth plays a key role in P uptake by algae. Phytoplankton communities in both deep and shallow enclosures were dominated by three cyanobacteria species ,Aphanizomenon flos-aquae, Anabaena flos-aquae and Microcystis aeruginosa, which accounted for up to 70% of total phytoplankton biomass. However, the absolute biomass of the three species was much higher in shallow enclosures, especially Aphanizomenon flos-aquae. The three cyanobacteria species responded in contrasting ways to nutrient manipulation because of their different physiology. 3.,Standardised concentrations of the hepatotoxic microcystin-LR increased as a result of nutrient manipulations by a factor of four in the treated enclosures. Increased biomass of inedible and toxin producing cyanobacteria was associated with a decline in Daphnia pulicaria biomass caused by a reduction in the number of individuals with a body length of >1 mm. Zooplankton biomass did not decline at moderate cyanobacteria biomass, but when cyanobacteria reached high biomass large cladocerans were reduced. 4.,Our results demonstrate that zooplankton communities can be negatively affected by cyanobacterial blooms and therefore the potential to use herbivory to reduce algal blooms in such eutrophic lakes appears limited. [source] Temporal variability of phytoplankton in a salt wedge estuary, the Swan,Canning Estuary, Western AustraliaHYDROLOGICAL PROCESSES, Issue 13 2001Peter A. Thompson Abstract The temporal cycles of variation in salinity, temperature and river flow in the Swan,Canning Estuary plus rainfall in the vicinity are examined. A ,normal' pattern is defined for rainfall and river flow based on long-term median monthly values from available historical data. Long-term monthly median rainfall and median monthly river flow were highly correlated. Deviations from the ,normal' patterns of rainfall and river flow are documented. Three years of detailed data on the temporal distribution of the algal biomass and phytoplankton community composition from the Swan,Canning Estuary are presented and discussed. Significant interannual variability in the phytoplankton biomass was observed with 1996 having a significantly lower median chlorophyll a concentration than 1995 or 1997. Different years also had pronounced differences in the timing, persistence and occurrence of algal blooms. Links with, and between, rainfall, river flow, nutrient concentrations and phytoplankton biomass are made by careful examination of the temporal patterns. Deviations from the proposed ,normal' temporal pattern of physical and chemical environmental factors relevant to the growth of phytoplankton biomass are assessed. Deviations from ,normal' rainfall and river flow, depending upon their timing and intensity, appear to be associated with occurrence of algal blooms. For example, the lack of a dinoflagellate bloom in December 1996 or January 1997 appears to be associated with a wetter than normal spring. Based upon the observed data, published reports and basic principles of algal ecology a set of predicted responses to variation in the major environmental variables (rainfall and river flow) are tabulated. The tabulated predictions are proposed as a useful tool for resource managers. Copyright © 2001 John Wiley & Sons, Ltd. [source] Post-Impoundment Biomass and Composition of Phytoplankton in the Yangtze RiverINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 3 2007Hui Zeng Abstract Damming, and thus alteration of stream flow, promotes higher phytoplankton populations and encourages algal blooms (density >106 cells L,1) in the Three Gorges Reservoir (TGR). Phytoplankton composition and biomass were studied in the Yangtze River from March 2004 to May 2005. 107 taxa were identified. Diatoms were the dominant group, followed by Chlorophyta and Cyanobacteria. In the Yangtze River, algal abundance varied from 3.13 × 103 to 3.83 × 106 cells L,1, and algal biomass was in the range of 0.06 to 659 mg C m,3. Levels of nitrogen, phosphorus and silica did not show consistent longitudinal changes along the river and were not correlated with phytoplankton parameters. Phytoplankton abundance was negatively correlated with main channel discharge (Spearman r = ,1.000, P < 0.01). Phytoplankton abundance and biomass in the Yangtze River are mainly determined by the hydrological conditions rather than by nutrient concentrations. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Did ciguatera prompt the late Holocene Polynesian voyages of discovery?JOURNAL OF BIOGEOGRAPHY, Issue 8 2009Teina Rongo Abstract The famous Polynesian voyages characterized an intensive network of cultural exchange and colonization that was particularly active from ad 1000 to 1450. But, why would large groups of people leave their homelands to voyage into the unknown? Oceanic voyages are risky, albeit less so today than in the past. Landfalls were not guaranteed improvements over ports of departure. Taking the Cook Islands as an example, we ask whether harmful algal blooms that result in ciguatera fish poisoning in humans prompted past and present emigration pulses of peoples from within Polynesia. We take a multipronged approach to examine our hypothesis, involving: (1) archaeological evidence, (2) ciguatera fish poisoning reports since the 1940s, and (3) climate and temperature oscillations using palaeodatasets. The archaeological records of fish bones and hooks show abrupt changes in fishing practices in post- ad 1450 records. Sudden dietary shifts are not linked to overfishing, but may be a sign of ciguatera fish poisoning and adjustment of fishing preference. While fishes form the staple diet of Polynesians, such poisoning renders fishes unusable. We show that ciguatera fish poisoning events coincide with Pacific Decadal Oscillations and suggest that the celebrated Polynesian voyages across the Pacific Ocean may not have been random episodes of discovery to colonize new lands, but rather voyages of necessity. A modern analogue (in the 1990s) was the shift towards processed foods in the Cook Islands during ciguatera fish poisoning events, and mass emigration of islanders to New Zealand and Australia. [source] POSITIVE FEEDBACK AND THE DEVELOPMENT AND PERSISTENCE OF ECOSYSTEM DISRUPTIVE ALGAL BLOOMS,JOURNAL OF PHYCOLOGY, Issue 5 2006William G. Sunda Harmful algal blooms (HABs) have occurred with increasing frequency in recent years with eutrophication and other anthropogenic alterations of coastal ecosystems. Many of these blooms severely alter or degrade ecosystem function, and are referred to here as ecosystem disruptive algal blooms (EDABs). These blooms are often caused by toxic or unpalatable species that decrease grazing rates by planktonic and benthic herbivores, and thereby disrupt the transfer of nutrients and energy to higher trophic levels, and decrease nutrient recycling. Many factors, such as nutrient availability and herbivore grazing have been proposed to separately influence EDAB dynamics, but interactions among these factors have rarely been considered. Here we discuss positive feedback interactions among nutrient availability, herbivore grazing, and nutrient regeneration, which have the potential to substantially influence the dynamics of EDAB events. The positive feedbacks result from a reduction of grazing rates on EDAB species caused by toxicity or unpalatability of these algae, which promotes the proliferation of the EDAB species. The decreased rates also lower grazer-mediated recycling of nutrients and thereby decrease nutrient availability. Since many EDAB species are well-adapted to nutrient-stressed environments and many exhibit increased toxin production and toxicity under nutrient limitation, positive feedbacks are established which can greatly increase the rate of bloom development and the adverse effects on the ecosystem. An understanding of how these feedbacks interact with other regulating factors, such as benthic/pelagic nutrient coupling, physical forcing, and life cycles of EDAB species provides a substantial future challenge. [source] 41 Incidence of paralytic shellfish toxin in bivalve mollusc tissue from the oregon coastJOURNAL OF PHYCOLOGY, Issue 2003R. C. Everroad Saxitoxin and domoic acid sequestration by bivalve molluscs occurs periodically along the Oregon coast, presumably as a result of harmful algal blooms (HABs). Since 1958 and more continuously since 1979, the Oregon Shellfish Program (OSP) has assayed toxin levels in these molluscs as part of a monitoring program for paralytic (PSP) and amnesic (ASP) shellfish poisoning. We have created a working data base for all PSP sampling by the OSP between 1958 and 2001 and have examined the data for spatial and temporal trends in the appearance of toxin in shellfish, amount of toxin, and apparent duration of toxic events. In this report, we examine the data from the five stations with the longest record of continuous sampling (1979,2000) for evidence of correlation with El Niño events, upwelling, and/or a pattern of increasing frequency or intensity of toxic events. We also compare the pattern of appearance of toxin at open coast stations with the timing of first appearance of toxin in shellfish at adjacent estuarine stations. This is an important analysis because, in Oregon, shellfish closures due to PSP occur frequently in mussel beds on the open coast and the source of toxin-producing organisms is unknown. [source] 147 Controlling Harmful Algal Blooms Through Clay FlocculationJOURNAL OF PHYCOLOGY, Issue 2003M. R. Sengco The potential use of clays to control harmful algal blooms (HABs) has been explored in East Asia, Australia, the United States, and Sweden. In Japan and South Korea, minerals such as montmorillonite, kaolinite, and yellow loess, have already been used in the field effectively, to protect fish mariculture from Cochlodinium spp. and other blooms. Cell removal occurs through the flocculation of algal and mineral particles, leading to the formation of larger aggregates (i.e. marine snow), which rapidly settle and further entrain cells during their descent. In the U.S., several clays and clay-rich sediments have shown high removal abilities (e.g. >80% cell removal efficiency) against Karenia brevis, Heterosigma akashiwo, Pfiesteria piscicida and Aureococcus anophagefferens. In some cases, the removal ability of certain clays was further enhanced with chemical flocculants, such as polyaluminum chloride (PAC), to increase their adhesiveness. However, cell removal was also affected by bloom concentration, salinity, and mixing. Cell mortality was observed after clay addition, and increased with increasing clay concentration, and prolonged exposure to clays in the settled layer. Mesocosm, field enclosure, and flume experiments were also conducted to address cell removal with increasing scale and flow, water-column impacts, and the possible benthic effects from clay addition. Results from these studies will be presented, especially those in regards to water quality, seawater chemistry, bottom erodibility and faunal impacts in the benthos. At this time, clay dispersal continues to be a promising method for controlling HABs and mitigating their impacts based on existing information and experimental data. [source] THE CYANOTOXINS-BIOACTIVE METABOLITES OF CYANOBACTERIA: OCCURRENCE, ECOLOGICAL ROLE, TAXONOMIC CONCERNS AND EFFECTS ON HUMANSJOURNAL OF PHYCOLOGY, Issue 2001Article first published online: 24 SEP 200 Carmichael, W. W. Department of Biological Sciences, Wright State University, Dayton, Ohio 45435 USA Cyanobacteria toxins (cyanotoxins) include cytotoxins and biotoxins with cytotoxins including about 60 compounds ranging from phytoalexins to animicrobials to enzyme inhibitors to compounds that can reverse multidrug resistance. Producer organisms include marine/brackish water Cystoseira, Hormothamnin, Lyngbya, Nodularia and Synechocystis, and the freshwater/terrestrial genera Anabaena, Dichotrix, Fischerella, Hapalosiphon, Lyngbya, Microcystis, Nostoc, Oscillatoria, Planktothrix, Phormidium, Schizothrix, Scytonema, Spirulina, Stigonema and Symploca. Since many of these compounds have been identified, not during ecological studies, but during drug discovery investigations, their ecological role is only speculative. Biotoxins are responsible for acute lethal, acute, chronic and sub-chronic poisonings of wild/domestic animals and humans. They include the neurotoxins; anatoxin-a, anatoxin-a(s) and saxitoxins plus the hepatotoxins; microcystins, nodularins and cylindrospermopsin. These compounds are included when referencing harmful algal blooms (HAB's) such as the more predominate marine PSP (paralytic shellfish poisoning), DSP (diarrhetic shellfish poisoning), NSP (neurotoxic shellfish poisoning), ASP (amnesic shellfish poisoning) and EAS (estuary associated syndrome). The CTP (cyanobacteria toxin poisoning) organisms occur in freshwater lakes, ponds, rivers and reservoirs throughout the world. Organisms responsible for CTP's are Anabaena, Aphanizomenon, Cylindrosperm- opsis, Microcystis, Nodularia, Nostoc Oscillatoria (Planktothrix), Trichodesmium and certain picoplanktic genera. Concern for animal and human health impairments arises from animal poisonings, associated with cyanobacteria waterblooms, beginning with the later part of the 1800's. It was not until the 1950's that we began to understand that cyanobacteria could indeed produce highly toxic compounds. A recent 1998 compilation of all available information on toxic cyanobacteria was published by the World Health Organization. This increasing focus on the role of cyanobacteria metabolites in chemical ecology, drug discovery and toxinology has placed new importance on using correct taxonomy for communication of responsible organisms. [source] rRNA PROBES FOR IDENTIFICATION AND CHARACTERIZATION OF MARINE PHYTOPLANKTON: THEIR POTENTIAL APPLICATION FOR DNA MICROCHIPSJOURNAL OF PHYCOLOGY, Issue 2001Article first published online: 24 SEP 200 Groben R., Lange, M. & Medlin, L. K. Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, D-27570 Bremerhaven, Germany A fast and reliable identification of nano- and picoplankton by light microscopy is often difficult because of the lack of usable morphological characteristics, whereas electron microscopy and biochemical methods are very time consuming. Identification of toxic algae also requires a great deal of taxonomic experrtise so that false positives are not recorded. One solution is to use taxon specific rRNA probes. For this purpose we designed probes for phytoplankton taxa, including toxic algae. These probes were either labelled with Digoxigenin (DIG) and used in DNA dot blot experiments, or labelled with fluorochromes and used in whole-cell hybridisations with fluorescence microscopy or flow cytometric detection. Specific probes could be used over a broad taxonomic range from higher groups (i.e. the class of dinoflagellates) to species level (i.e. Prorocentrum lima). These probes were be used in the EU MAST project AIMS for the development of an automated identification system for marine phytoplankton in combination with flow cytometry and artificial neural networks (ANNs), in the EU MAST DETAL and in the German national project (TEPS) for the development of an early warning system for harmful algal blooms. Results using Digoxigenin (DIG)-labelled probes on picoplankton samples taken from several water bodies indicate that hierarchial re-probing of spotted samples can be achieved and this suggests that probes can be adapted to DNA microchips. Preliminary field results for a hand-held DNA microchip reader are presented. This work was supported by the German BMBF TEPS 03F0161 and the EU AIMS MAS3-CT97-0080 and EU DETAL Q5RS-2000-30778 projects. [source] DO PHYSICAL FACTORS REGULATE PHYTOPLANKTON DISTRIBUTION PATTERNS IN LARGE, SHALLOW LAKES?JOURNAL OF PHYCOLOGY, Issue 2000H.J. Carrick Factors that regulate phytoplankton dynamics in shallow, productive lakes are poorly understood, due to their predisposition for frequent algal blooms and sediment resuspension events. In Lake Apopka, greatest phytoplankton biomass reflects wind-induced resuspension of algae (meroplankton) that exists on the aphotic lake bottom in a layer approximately 5 cm thick; this assemblage is dominated by diatoms (>60% of total biomass) that can occur in resting stages. Once exposed to moderate light, meroplankton are capable of growth and photosynthetic rates comparable with surface populations. In Lake Okeechobee, remote sensing was used to assess the basin-wide distribution of suspended particles. Satellite reflectance values agreed well with in situ particle densities at 20 in-lake stations (average r2; LANDSAT = 0.81, AVHRR = 0.53), and maps of algal blooms (r2 = 0.79, p , 0.01). The greatest chlorophyll concentrations occurred in the vicinity of tributary nutrient inputs at the lake's perimeter, while turbidity increased towards the center of the lake reflecting predominant water circulation patterns. These results underscore the importance of physical-biological interactions in lakes. [source] Effects of chlorpyrifos in freshwater model ecosystems: the influence of experimental conditions on ecotoxicological thresholdsPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 10 2005René PA van Wijngaarden Abstract Three experiments were conducted to determine the impact of the insecticide chlorpyrifos (single applications of 0.01 to 10 µg AI litre,1) in plankton-dominated nutrient-rich microcosms. The microcosms (water volume approximately 14 litres) were established in the laboratory under temperature, light regimes and nutrient levels that simulated cool ,temperate' and warm ,Mediterranean' environmental conditions. The fate of chlorpyrifos in the water column was monitored and the effects on zooplankton, phytoplankton and community metabolism were followed for 4 or 5 weeks. The mean half-life (t1/2) of chlorpyrifos in the water of the test systems was 45 h under ,temperate' conditions and about 30 h under ,Mediterranean' environmental conditions. Microcrustaceans (cladocerans and copepod nauplii) were amongst the most sensitive organisms. All three experiments yielded community NOEC (no observed effect concentrations) of 0.1 µg AI litre,1, similar to those derived from more complex outdoor studies. Above this threshold level, responses and effect chains, and time spans for recovery, differed between the experiments. For example, algal blooms as an indirect effect from the impact of exposure on grazing organisms were only observed under the ,Mediterranean' experimental conditions. The relatively simple indoor test system seems to be sufficient to provide estimates of safe threshold levels for the acute insecticidal effects of low-persistence compounds such as chlorpyrifos. The robustness of the community NOEC indicates that this threshold level is likely to be representative for many freshwater systems. Copyright © 2005 Society of Chemical Industry [source] Microzooplankton grazing on harmful dinoflagellate blooms: Are ciliates or heterotrophic dinoflagellates important?THE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 2 2005DIANE K. STOECKER Microzooplankton grazing can be important in regulating growth of dinoflagellate populations, including species responsible for harmful algal blooms. In the Chesapeake Bay region, microzooplankton community grazing coefficients on small cell-size dinoflagellates are often greater than potential gross growth coefficients of dinoflagellates, and thus grazing may prevent bloom formation. Who are the major microzooplankton grazers on small dinoflagellates? Ciliates or other dinoflagellates? Data from Chesapeake Bay and its tributaries indicate both; sometimes ciliates and sometimes dinoflagellates are the major grazers. The importance of ciliates and heterotrophic dinoflagellates varies with season and location, but often one group dominates the microzooplankton assemblage. Specific clearance and division rates of ciliates are higher than that of heterotrophic dinoflagellates, thus it could be expected that ciliates would be the dominant microzooplankton grazers. However, during summer, small heterotrophic dinoflagellates are often the dominant grazers on small dinoflagelllates in the mesohaline Bay. Differential predation by copepods on ciliates may be responsible for this pattern. When microzooplankton community grazing is less than dinoflagellate cell division, red tides may result. Thus, it is important to understand the factors controlling both ciliate and heterotrophic dinoflagellate populations and their grazing impacts. [source] Estuarine eutrophication in the UK: current incidence and future trendsAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 1 2009Gerald Maier Abstract 1.Increased inputs of nutrients to estuaries can lead to undesirable effects associated with eutrophication, including algal blooms, changes in species composition and bottom anoxia. Several estuaries and coastal areas around the UK have increased nitrogen (N) and phosphorus (P) concentrations, elevated concentrations of chlorophyll a and changes in algal community composition and abundance. This paper reviews the pressures that lead to high nutrient concentrations in estuaries and considers the likely effectiveness of current and proposed regulatory actions. 2.The main sources of nutrients to estuaries are river runoff, sewage discharges, atmospheric inputs and possibly submarine groundwater discharges, although little is known about the latter. Significant reductions in N and P inputs have been realized following application of the EU's Urban Waste Water Treatment Directive. Atmospheric NOx and NHx emissions have also decreased and are expected to decrease further in the next decade as implementation of existing legislation continues, and new controls are introduced for activities such as shipping. 3.Agricultural inputs reach estuaries principally through diffuse sources, either in surface water (and in some areas possibly groundwater) or, for N, via the atmosphere. Over 10 years ago the Nitrates Directive was introduced to tackle the problem of N discharges from agriculture but little change in N loads to estuaries has been recorded. 4.To meet the aims of the EU Water Framework Directive, for at least ,good' ecological status, more rigorous application and implementation of the Nitrates Directive, together with changes in the Common Agriculture Policy and farming practice are likely to be needed. Even then, the slow response of the natural environment to change and the inherent variability of estuaries means that their responses may not be as predicted. Research is needed into the relationship between policy drivers and environmental responses to ensure actions taken will achieve the planned results. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||||||||