RESUMO
Potable source-water reservoirs are the main water supplies in many urbanizing regions, yet their long-term responses to cultural eutrophication are poorly documented in comparison with natural lakes, creating major management uncertainties. Here, long-term discrete data (June 2006-June 2018) for classical eutrophication water quality indicators, continuous depth-profile data for dissolved oxygen (DO), and an enhanced hybrid statistical trend analysis model were used to evaluate the eutrophication status of a potable source-water reservoir. Based on classical indicators (nitrogen, N and phosphorus, P concentrations and ratios; phytoplankton biomass as chlorophyll a, chl a; and trophic state indices), the reservoir was eutrophic to hypereutrophic and stoichiometrically imbalanced. Anoxia/hypoxia occurred for 7-8 months annually systemwide, even throughout the water column for days to weeks in some years; and elevated total ammonia (up to ~900 µg tNH3 L-1 ) in surface waters from late summer/fall through late winter/early spring suggested substantial internal legacy nutrient loading. These surprising DO and tNH3 phenomena may characterize many reservoirs in urbanizing areas, and the associated cascade of negative impacts may increasingly affect them under global warming. Total organic carbon (TOC), seasonally influenced by phytoplankton biomass, commonly exceeded 6 mg L-1 , which is problematic for potable-water treatment, and significantly trended up over time. Wet-year inflow dilution influenced an apparent decreasing trend in nutrients within the hypereutrophic upper reservoir, which receives most tributary inputs. Nevertheless, significant reservoirwide trends (increasing total phosphorus [TP], phytoplankton chl a, TOC) and mid- and/or lower region trends (increasing total nitrogen [TN], tNH3 , decreasing TN:TP ratios) suggest that water quality degradation from eutrophication has worsened over time. These findings support broadly applicable recommendations to strengthen protection of potable source-water reservoirs in urbanizing watersheds: (1) protective numeric water quality criteria are needed for TOC as well as TN, TP, and chl a; (2) continuous diel data capture more realistic DO conditions than traditional sampling, and can provide important insights for water treatment managers; and (3) assessment of reservoir eutrophication status to track management progress over time should emphasize classic indicators equally as statistical trends, which are highly sensitive to short-term meteorological forcing.
Assuntos
Água Potável , China , Clorofila/análise , Clorofila A/análise , Água Potável/análise , Monitoramento Ambiental , Eutrofização , Lagos/análise , Nitrogênio/análise , Oxigênio , Fósforo/análise , FitoplânctonRESUMO
Pleurocapsales are one of the least understood groups of cyanobacteria in terms of molecular systematics and biochemistry. Considering the high number of cryptic taxa within the Synechococcales and Oscillatoriales, it is likely that such taxa also occur in the Pleurocapsales. The new genus described in our research is the first known pleurocapsalean cryptic taxon. It produces off-flavor and a large number of bioactive metabolites (n = 38) some of which can be toxic including four known microcystins. Using a polyphasic approach, we propose the establishment of the genus Odorella with the new species O. benthonica from material originally isolated from the California Aqueduct near Los Angeles.
Assuntos
Cianobactérias , Odorantes , California , DNA Bacteriano , Filogenia , RNA Ribossômico 16S , Análise de Sequência de DNARESUMO
Cultural eutrophication from excessive human-related nutrient (phosphorus, P, and nitrogen, N) inputs is a major concern for water quality. Because P historically was regarded as the critical nutrient in controlling noxious algal/plant growth, P became the focus of "capturing" techniques, with emphasis on removal performance rather than environmental impacts. Here, we synthesize a literature review of known environmental effects linked to use of metal-cation-based P-capturing materials under eutrophic conditions in freshwaters. P-capturing materials with functional cations based on aluminum (Al), calcium (Ca), iron (Fe), lanthanum (La), and magnesium (Mg) were reviewed in terms of their ecotoxicity, persistence, and bioaccumulation-standard criteria used to evaluate environmental risks of chemical substances. We found very few published studies on environmental impacts of metal-cation-based P-capturing materials under eutrophic conditions. Available reports indicated that environmental effects vary depending on the selected material, dose, target organism(s), and experimental conditions. The Al-based materials had the potential to negatively impact various biota; several Fe-based materials caused various levels of toxicity in a limited group of aquatic organisms; La-based materials can bioaccumulate and some were linked to various harmful effects on biota; and Mg-based materials also adversely affected various organisms. The limited number of published studies underscores the need for further research to characterize the environmental impacts of these materials. Results can be used to guide future work and can assist resource managers in sustainable management strategies. Among various research needs, future assessments should assess the impacts of chronic exposures on sensitive species under realistic field conditions in eutrophic waters.
RESUMO
Cyanobacterial blooms have increased in frequency, distribution, and intensity due to climate change and anthropogenic nutrient input. The release of bioactive compounds accumulated in these blooms can affect the health of humans and the environment. The co-occurrence of bioactive metabolites is well-documented in bloom samples from marine and freshwater ecosystems, with fewer reports from unialgal isolates. Cyanobacteria also are important terrestrial ecosystem components, especially in drylands, but reports on bioactive molecules from terrestrial cyanobacteria are sparse. This study determined bioactive metabolite profiles for 71 genera of cyanobacteria from seven orders isolated from freshwater (12 genera), marine (15 genera), and terrestrial (44 genera) habitats originally. Cultures were harvested for bioactive metabolites when entering the late-exponential phase for all 157 strains, and 33 were sampled at both early and late exponential phases. Bioactive metabolites were analyzed using an ultra high performance/pressure liquid chromatography in-line with a time-of-flight mass spectrometer. Overall, 12 bioactive classes of the 28 identified were ubiquitous in all samples. On average, each freshwater genus produced â¼12 bioactive classes, whereas each marine genus contained > 4 bioactive classes, and each terrestrial genus contained â¼6 bioactive classes. While 10 of 12 freshwater genera produced at least 10 bioactive classes, only a single genus each from marine and terrestrial habitats had the same number of bioactive classed accumulated. Aeruginosin was found in 58 of 71 total genera, carmabin in 51 of 71 genera, and anabaenopeptin in 48 of 71 genera. Chemotaxonomic use of these secondary metabolites may help resolve higher-level genetic classification(s). An additional growth curve experiment showed that bioactive metabolites were produced at both early and late exponential growth phases. The bioactive metabolite accumulation pattern between early and late exponential phases differed by bioactive classes, genera, and habitats. This survey of 55 bioactive classes in cyanobacteria isolated from freshwater, marine, and terrestrial habitats (71 genera) provides as one of the first systematic bioactive metabolite profiles for cyanobacteria, which should be useful in environmental and drinking water management. Further, it offers novel insights about the toxin potential of selected terrestrial cyanobacteria.
Assuntos
Cianobactérias , Ecossistema , Cromatografia Líquida de Alta Pressão , Cianobactérias/metabolismo , Água Doce/microbiologiaRESUMO
A semi-defined, biphasic culture medium was developed that supported the axenic growth of three strains of the heterotrophic dinoflagellate Pfiesteria shumwayae. Maximum cell yields and division rates in the semi-defined medium ranged from 0.1 x 10(5) to 4.0 x 10(5) cells/ml and 0.5 to 1.7 divisions/day, respectively, and depended on the concentration of the major components in the medium as well as the P. shumwayae strain. The medium contained high concentrations of certain dissolved and particulate organic compounds, including amino acids and lipids. Pfiesteria shumwayae flagellated cells were attracted to insoluble lipids present in the medium and appeared to feed on the lipid particles, suggesting that phagocytosis may be required for growth in axenic culture. Development of a semi-defined medium represents significant progress toward a completely defined axenic culture medium and subsequent determination of the biochemical requirements of P. shumwayae, needed to advance understanding of the nutritional ecology of this species. Further, this medium provides an economical, simplified method for generating high cell densities of P. shumwayae in axenic culture that will facilitate controlled investigations on the physiology and biochemistry of this heterotrophic dinoflagellate.
Assuntos
Meios de Cultura/química , Dinoflagellida/crescimento & desenvolvimento , Vida Livre de Germes , Parasitologia/métodos , AnimaisRESUMO
The watershed of the Neuse River, a major tributary of the largest lagoonal estuary on the U.S. mainland, has sustained rapid growth of human and swine populations. This study integrated a decade of available land cover and water quality data to examine relationships between land use changes and surface water quality. Geographic Information Systems (GIS) analysis was used to characterize 26 subbasins throughout the watershed for changes in land use during 1992-2001, considering urban, agricultural (cropland, animal as pasture, and densities of confined animal feed operations [CAFOs]), forested, grassland, and wetland categories and numbers of wastewater treatment plants (WWTPs). GIS was also used together with longitudinal regression analysis to identify specific land use characteristics that influenced surface water quality. Total phosphorus concentrations were significantly higher during summer in subbasins with high densities of WWTPs and CAFOs. Nitrate was significantly higher during winter in subbasins with high numbers of WWTPs, and organic nitrogen was higher in subbasins with higher agricultural coverage, especially with high coverage of pastures fertilized with animal manure. Ammonium concentrations were elevated after high precipitation. Overall, wastewater discharges in the upper, increasingly urbanized Neuse basin and intensive swine agriculture in the lower basin have been the highest contributors of nitrogen and phosphorus to receiving surface waters. Although nonpoint sources have been emphasized in the eutrophication of rivers and estuaries such as the Neuse, point sources continue to be major nutrient contributors in watersheds sustaining increasing human population growth. The described correlation and regression analyses represent a rapid, reliable method to relate land use patterns to water quality, and they can be adapted to watersheds in any region.
Assuntos
Rios , Poluentes da Água/análise , Áreas Alagadas , Agricultura , Animais , Sistemas de Informação Geográfica , Nitrogênio/análise , North Carolina , Fósforo/análise , SuínosRESUMO
Coastal waters of the United States (U.S.) are subject to many of the major harmful algal bloom (HAB) poisoning syndromes and impacts. These include paralytic shellfish poisoning (PSP), neurotoxic shellfish poisoning (NSP), amnesic shellfish poisoning (ASP), ciguatera fish poisoning (CFP) and various other HAB phenomena such as fish kills, loss of submerged vegetation, shellfish mortalities, and widespread marine mammal mortalities. Here, the occurrences of selected HABs in a selected set of regions are described in terms of their relationship to eutrophication, illustrating a range of responses. Evidence suggestive of changes in the frequency, extent or magnitude of HABs in these areas is explored in the context of the nutrient sources underlying those blooms, both natural and anthropogenic. In some regions of the U.S., the linkages between HABs and eutrophication are clear and well documented, whereas in others, information is limited, thereby highlighting important areas for further research.
RESUMO
We investigated the effect of high power ultrasound, at a frequency of 19 kHz, on the survival of bacteria, phytoplankton and zooplankton, in order to obtain estimates of effective exposure times and energy densities that could be applied to design of ultrasonic treatment systems for ballast water. Efficacy of ultrasonic treatment varied with the size of the test organism. Zooplankton required only 3-9s of exposure time and 6-19 J/mL of ultrasonic energy to realize a 90% reduction in survival. In contrast, decimal reduction times for bacteria and phytoplankton ranged from 1 to 22 min, and decimal reduction energy densities from 31 to 1240 J/mL. Our results suggest that stand-alone ultrasonic treatment systems for ballast water, operating at 19-20 kHz, may be effective for planktonic organisms >100 microm in size, but smaller planktonic organisms such as phytoplankton and bacteria will require treatment by an additional or alternative system.
Assuntos
Bactérias , Fitoplâncton/fisiologia , Sonicação , Zooplâncton/fisiologia , Animais , NaviosRESUMO
The proposed plan for enrichment of the Sulu Sea, Philippines, a region of rich marine biodiversity, with thousands of tonnes of urea in order to stimulate algal blooms and sequester carbon is flawed for multiple reasons. Urea is preferentially used as a nitrogen source by some cyanobacteria and dinoflagellates, many of which are neutrally or positively buoyant. Biological pumps to the deep sea are classically leaky, and the inefficient burial of new biomass makes the estimation of a net loss of carbon from the atmosphere questionable at best. The potential for growth of toxic dinoflagellates is also high, as many grow well on urea and some even increase their toxicity when grown on urea. Many toxic dinoflagellates form cysts which can settle to the sediment and germinate in subsequent years, forming new blooms even without further fertilization. If large-scale blooms do occur, it is likely that they will contribute to hypoxia in the bottom waters upon decomposition. Lastly, urea production requires fossil fuel usage, further limiting the potential for net carbon sequestration. The environmental and economic impacts are potentially great and need to be rigorously assessed.
Assuntos
Carbono/química , Ecossistema , Fertilizantes/análise , Ureia/química , Ureia/farmacologia , Efeito Estufa , Oceanos e MaresRESUMO
Anthropogenic inputs of chemical environmental contaminants are frequently associated with developing harmful algal blooms, but little is known about how estuarine phytoplankton assemblages respond to multiple, co-occurring chemical stressors in chronically disturbed habitats. The goals of this research were to establish a robust protocol for testing the effects of atrazine on estuarine phytoplankton, and then to use that protocol to compare the effects of atrazine exposure with and without nutrient enrichment on a cosmopolitan estuarine/marine alga, Dunaliella tertiolecta (Chlorophyta). Atrazine sensitivity in nutrient-replete media (96-h growth inhibition [Formula: see text]) was 159.16 µg l-1, but sensitivity was influenced by exposure duration, and inhibitory effects of herbicide on algal growth decreased under imbalanced nutrient regimes and low nitrogen and phosphorus supplies. These findings advance knowledge about how nutrient regimes and herbicides interact to control estuarine phytoplankton population dynamics.
Assuntos
Atrazina/toxicidade , Clorofíceas/efeitos dos fármacos , Herbicidas/toxicidade , Poluentes Químicos da Água/toxicidade , Clorófitas/efeitos dos fármacos , Fitoplâncton/efeitos dos fármacos , Fitoplâncton/crescimento & desenvolvimentoRESUMO
The toxigenic haptophyte Prymnesium parvum is a mixotrophic phytoplankter with an extensive historic record of forming nearly monospecific, high-biomass, ecosystem-disrupting blooms, and it has been responsible for major fish kills in brackish waters and aquaculture facilities in many regions of the world. Little is known about how this species responds to commonly occurring environmental contaminants, or how nutrient (nitrogen, phosphorus) pollution may interact with environmentally relevant pesticide exposures to affect this harmful algal species. Here, standard algal toxicity bioassays from pesticide hazard assessments were used along with modified erythrocyte lysis assays to evaluate how atrazine exposures, imbalanced nutrient supplies, and salinity interact to influence the growth and toxicity in P. parvum isolates from three different regions. In nutrient-replete media, P. parvum 96â¯h IC50s ranged from 73.0 to 88.3⯵g atrazine L-1 at salinity 10 and from 118 to >200⯵g atrazine µgâ¯L-1 at salinity 20, and the response depended on the strain and the test duration. Relative hemolytic activity, used as an indication of toxicity, was a function of herbicide exposure, nutrient availability, salinity, geographic origin, and interactions among these factors. Highest levels of hemolytic activity were measured from a South Carolina strain in low-nitrogen media with high atrazine concentrations. Herbicide concentration was related to relative hemolytic activity, although a consistent relationship between growth phase and toxicity was not observed. Overall, these findings suggest that increasing chemical contamination is helping to promote ecosystem-disruptive, strongly mixotrophic algal blooms.
Assuntos
Eutrofização/efeitos dos fármacos , Haptófitas/efeitos dos fármacos , Resistência a Herbicidas/fisiologia , Herbicidas/metabolismo , Poluentes Químicos da Água/metabolismo , Haptófitas/crescimento & desenvolvimento , Nitrogênio/metabolismo , Nutrientes/metabolismo , Fósforo/metabolismoRESUMO
The potential for toxic contaminants and nutrient pollution to alter natural cycles of estuarine phytoplankton blooms is well known, yet few studies have examined how these combined stressors affect harmful algal species. Here, a robust testing protocol was developed to enable an ecotoxicological assessment of responses to commonly co-occurring estuarine contaminants by harmful algal bloom species. The population growth and toxicity (as cell density and hemolytic activity, respectively) of a cultured strain of the toxigenic raphidiophycean, Chattonella subsalsa, were assessed in two experiments (duration 10â¯days and 28â¯days) across a gradient of atrazine concentrations and N:P ratios simulating nutrient-rich versus nutrient-depleted regimes. The response of this large-celled, slowly growing alga to atrazineâ¯×â¯nutrients depended on growth phase; atrazine was most inhibitory during early exponential population growth (day 10), whereas nutrient regime was a more important influence during later phases of growth (day 28). Without atrazine, toxicity toward fish was highest in low-P cultures. At atrazine levels >25⯵gâ¯L-1, hemolytic activity was highest in low-N cultures, and increased with increasing atrazine concentration in all nutrient-limited cultures. Hemolytic activity varied inversely with atrazine concentration in N,P-replete conditions. Overall, atrazine inhibitory effects on population growth of this C. subsalsa strain depended on the growth phase and the nutrient regime; hemolytic activity was higher and further enhanced by atrazine in low N-P regimes; and atrazine inhibited hemolytic activity in nutrient-replete conditions. The data suggest that, depending on the growth phase and nutrient regime, atrazine can help promote toxic C. subsalsa blooms.
Assuntos
Proliferação Nociva de Algas/fisiologia , Fitoplâncton/fisiologia , Estramenópilas/fisiologia , Poluentes Químicos da Água/análise , Animais , Atrazina/análise , Estuários , Peixes/sangue , Hemólise , Nitrogênio/análise , Nutrientes/análise , Fósforo/análise , Fitoplâncton/crescimento & desenvolvimento , Estramenópilas/crescimento & desenvolvimento , Fatores de TempoRESUMO
Waste from agricultural livestock operations has been a long-standing concern with respect to contamination of water resources, particularly in terms of nutrient pollution. However, the recent growth of concentrated animal feeding operations (CAFOs) presents a greater risk to water quality because of both the increased volume of waste and to contaminants that may be present (e.g., antibiotics and other veterinary drugs) that may have both environmental and public health importance. Based on available data, generally accepted livestock waste management practices do not adequately or effectively protect water resources from contamination with excessive nutrients, microbial pathogens, and pharmaceuticals present in the waste. Impacts on surface water sources and wildlife have been documented in many agricultural areas in the United States. Potential impacts on human and environmental health from long-term inadvertent exposure to water contaminated with pharmaceuticals and other compounds are a growing public concern. This work-group, which is part of the Conference on Environmental Health Impacts of Concentrated Animal Feeding Operations: Anticipating Hazards--Searching for Solutions, identified needs for rigorous ecosystem monitoring in the vicinity of CAFOs and for improved characterization of major toxicants affecting the environment and human health. Last, there is a need to promote and enforce best practices to minimize inputs of nutrients and toxicants from CAFOs into freshwater and marine ecosystems.
Assuntos
Ração Animal , Resíduos , Poluentes Químicos da Água/análise , Água/química , Criação de Animais Domésticos/normas , Animais , Exposição Ambiental/prevenção & controle , Monitoramento Ambiental , Abrigo para Animais/normas , HumanosRESUMO
Historically, phosphorus (P) has been considered the primary limiting nutrient for phytoplankton assemblages in freshwater ecosystems. This review, supported by new findings from Lake Erie, highlights recent molecular, laboratory, and field evidence that the growth and toxicity of some non-diazotrophic blooms of cyanobacteria can be controlled by nitrogen (N). Cyanobacteria such as Microcystis possess physiological adaptations that allow them to dominate low-P surface waters, and in temperate lakes, cyanobacterial densities can be controlled by N availability. Beyond total cyanobacterial biomass, N loading has been shown to selectively promote the abundance of Microcystis and Planktothrix strains capable of synthesizing microcystins over strains that do not possess this ability. Among strains of cyanobacteria capable of synthesizing the N-rich microcystins, cellular toxin quotas have been found to depend upon exogenous N supplies. Herein, multi-year observations from western Lake Erie are presented demonstrating that microcystin concentrations peak in parallel with inorganic N, but not orthophosphate, concentrations and are significantly lower (p<0.01) during years of reduced inorganic nitrogen loading and concentrations. Collectively, this information underscores the importance of N as well as P in controlling toxic cyanobacteria blooms. Furthermore, it supports the premise that management actions to reduce P in the absence of concurrent restrictions on N loading may not effectively control the growth and/or toxicity of non-diazotrophic toxic cyanobacteria such as the cosmopolitan, toxin-producing genus, Microcystis.
Assuntos
Cianobactérias/fisiologia , Água Doce , Nitrogênio/metabolismo , Cianobactérias/metabolismo , Água Doce/química , Água Doce/microbiologia , Microcistinas/metabolismo , Microcistinas/toxicidade , Fósforo/metabolismoRESUMO
Arranging organisms into functional groups aids ecological research by grouping organisms (irrespective of phylogenetic origin) that interact with environmental factors in similar ways. Planktonic protists traditionally have been split between photoautotrophic "phytoplankton" and phagotrophic "microzooplankton". However, there is a growing recognition of the importance of mixotrophy in euphotic aquatic systems, where many protists often combine photoautotrophic and phagotrophic modes of nutrition. Such organisms do not align with the traditional dichotomy of phytoplankton and microzooplankton. To reflect this understanding, we propose a new functional grouping of planktonic protists in an eco-physiological context: (i) phagoheterotrophs lacking phototrophic capacity, (ii) photoautotrophs lacking phagotrophic capacity, (iii) constitutive mixotrophs (CMs) as phagotrophs with an inherent capacity for phototrophy, and (iv) non-constitutive mixotrophs (NCMs) that acquire their phototrophic capacity by ingesting specific (SNCM) or general non-specific (GNCM) prey. For the first time, we incorporate these functional groups within a foodweb structure and show, using model outputs, that there is scope for significant changes in trophic dynamics depending on the protist functional type description. Accordingly, to better reflect the role of mixotrophy, we recommend that as important tools for explanatory and predictive research, aquatic food-web and biogeochemical models need to redefine the protist groups within their frameworks.
Assuntos
Eucariotos/classificação , Cadeia Alimentar , Fitoplâncton/classificação , Zooplâncton/classificação , Animais , Metabolismo Energético/fisiologia , Eucariotos/metabolismo , Eucariotos/fisiologia , Processos Fototróficos , Filogenia , Fitoplâncton/metabolismo , Fitoplâncton/fisiologia , Zooplâncton/metabolismo , Zooplâncton/fisiologiaRESUMO
Several dinoflagellate strains of the genus Pfiesteria were isolated by culturing techniques from sediment samples taken in the Oslofjord region of Norway. Pfiesteria piscicida, well known as a fish killer from the Atlantic coast of America, was identified by genetic methods and light microscopy. The related species Pfiesteria shumwayae was attracted from the sediment by the presence of fish, and has proved toxic. This present survey demonstrates the wide distribution of these potentially harmful species, but so far they have not been connected with fish kills in Europe.
Assuntos
Dinoflagellida/isolamento & purificação , Pfiesteria piscicida/isolamento & purificação , Água do Mar/parasitologia , Animais , Oceano Atlântico , DNA de Protozoário/análise , DNA Ribossômico/análise , Dinoflagellida/classificação , Dinoflagellida/genética , Europa (Continente) , Noruega , Pfiesteria piscicida/classificação , Pfiesteria piscicida/genética , Filogenia , RNA Ribossômico 18S/análiseRESUMO
Pfiesteria piscicida, an estuarine dinoflagellate, which has been shown to kill fish, has also been associated with neurocognitive deficits in humans. With a rat model, we have demonstrated the cause-and-effect relationship between Pfiesteria exposure and learning impairment. In several studies, we have replicated the finding in Sprague-Dawley rats that exposure to fixed acute doses of Pfiesteria cells or filtrates caused radial-arm maze learning impairment. Recently, this finding of Pfiesteria-induced learning impairment in rats has been independently replicated in another laboratory as well. We have demonstrated significant Pfiesteria-induced learning impairment in both the win-shift and repeated-acquisition tasks in the radial-arm maze and in reversal learning in a visual operant signal detection task. These learning impairments have been seen as long as 10 weeks after a single acute exposure to Pfiesteria. In the current study, we used a hydrophilic toxin isolated from clonal P. piscicida cultures (PfTx) and tested its effect when applied locally to the ventral hippocampus on repeated acquisition of rats in the radial-arm maze. Toxin exposure impaired choice accuracy in the radial-arm maze repeated acquisition procedure. The PfTx-induced impairment was seen at the beginning of the session and the early learning deficit was persistent across 6 weeks of testing after a single administration of the toxin. Eventually, with enough practice, in each session, the PfTx-exposed rats did learn that session's problem as did control rats. This model has demonstrated the cause-and-effect relationship between exposure to a hydrophilic toxin produced by P. piscicida and learning impairment, and specifically that the ventral hippocampus was critically involved.
Assuntos
Hipocampo/microbiologia , Deficiências da Aprendizagem/etiologia , Neurotoxinas/toxicidade , Pfiesteria piscicida/metabolismo , Infecções Protozoárias em Animais/fisiopatologia , Animais , Comportamento Animal/efeitos dos fármacos , Feminino , Hipocampo/efeitos dos fármacos , Aprendizagem em Labirinto/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Tempo de Reação , Fatores de TempoAssuntos
Cianobactérias/patogenicidade , Eutrofização , Toxinas Bacterianas/química , Toxinas Bacterianas/toxicidade , Cianobactérias/classificação , Cianobactérias/isolamento & purificação , Toxinas de Cianobactérias , Ecossistema , Água Doce/microbiologia , Humanos , Toxinas Marinhas/química , Toxinas Marinhas/toxicidade , Microcistinas/química , Microcistinas/toxicidade , Saúde Pública , Água do Mar/microbiologia , Estados UnidosRESUMO
Pfiesteria shumwayae Glasgow et J. M. Burkh. [=Pseudopfiesteria shumwayae (Glasgow et J. M. Burkh.) Litaker, Steid., P. L. Mason, Shields et P. A. Tester] is a heterotrophic dinoflagellate commonly found in temperate, estuarine waters. P. shumwayae can feed on other protists, fish, and invertebrates, but research on the biochemical requirements of this species has been restricted by the lack of axenic cultures. An undefined, biphasic culture medium was formulated that supported the axenic growth of two of three strains of P. shumwayae. The medium contained chicken egg yolk as a major component. Successful growth depended on the method used to sterilize the medium, and maximum cell yields (10(4) · mL(-1) ) were similar to those attained in previous research when P. shumwayae was cultured with living fish or microalgae. Additionally, P. shumwayae flagellate cells ingested particles present in the biphasic medium, allowing detailed observations of feeding behavior. This research is an initial step toward a chemically defined axenic culture medium and determination of P. shumwayae metabolic requirements.
RESUMO
Toxicity and its detection in the dinoflagellate fish predators Pfiesteria piscicida and Pfiesteria shumwayae depend on the strain and the use of reliable assays. Two assays, standardized fish bioassays (SFBs) with juvenile fish and fish microassays (FMAs) with larval fish, were compared for their utility to detect toxic Pfiesteria. The comparison included strains with confirmed toxicity, negative controls (noninducible Pfiesteria strains and a related nontoxic cryptoperidiniopsoid dinoflagellate), and P. shumwayae strain CCMP2089, which previously had been reported as nontoxic. SFBs, standardized by using toxic Pfiesteria (coupled with tests confirming Pfiesteria toxin) and conditions conducive to toxicity expression, reliably detected actively toxic Pfiesteria, but FMAs did not. Pfiesteria toxin was found in fish- and algae-fed clonal Pfiesteria cultures, including CCMP2089, but not in controls. In contrast, noninducible Pfiesteria and cryptoperidiniopsoids caused no juvenile fish mortality in SFBs even at high densities, and low larval fish mortality by physical attack in FMAs. Filtrate from toxic strains of Pfiesteria spp. in bacteria-free media was cytotoxic. Toxicity was enhanced by bacteria and other prey, especially live fish. Purified Pfiesteria toxin extract adversely affected mammalian cells as well as fish, and it caused fish death at environmentally relevant cell densities. These data show the importance of testing multiple strains when assessing the potential for toxicity at the genus or species level, using appropriate culturing techniques and assays.