Prymnesium parvum Population Dynamics During Bloom Development: A Role Assessment of Grazers and Virus1

Schwierzke, Leslie, Daniel L. Roelke, Bryan W. Brooks, James P. Grover, Theodore W. Valenti, Jr., Mieke Lahousse, Carrie J. Miller, and James L. Pinckney, 2010. Prymnesium parvum Population Dynamics During Bloom Development: A Role Assessment of Grazers and Virus. Journal of the American Water Resources Association (JAWRA) 46(1):63-75. DOI: 10.1111/j.1752-1688.2009.00391.x Abstract: The toxic haptophyte Prymnesium parvum is a harmful alga known to cause fish-killing blooms that occur worldwide. In Texas (United States), P. parvum blooms occur in inland brackish water bodies and have increased in frequency and magnitude in recent years. In this study we conducted three consecutive field experiments (Lake Whitney) to investigate the influence of zooplankton and viruses on P. parvum bloom dynamics during the time of year when blooms are still typically active in Texas (early spring). A localized P. parvum bloom developed during our study that involved increasing levels of toxicity (based on Pimephales promelas and Daphnia magna bioassays). Only in our last experiment, during later stages of bloom development and under highly toxic conditions, did the presence of grazers show a statistically significant, negative effect on P. parvum population dynamics. During this experiment, a rotifer-dominated zooplankton community emerged, composed mostly of Notholca laurentiae, suggesting that this species was less sensitive than other grazers to toxins produced by P. parvum. Microzooplankton may have also been important at this time. Similarly, only our final experiment demonstrated a statistically significant, negative effect of viruses on P. parvum. This exploratory study, resulting in observed impacts on P. parvum populations by both grazers and virus, enhances our understanding of P. parvum ecology and highlights direction for future studies on resistance of zooplankton to prymnesin toxins and algal-virus interactions.     

Mini Review: Probes for Detecting Prymnesium parvum and Preliminary Results From Gene Expression Studies1

Medlin, Linda K., Sonja Diercks, and Sara Beszteri, 2010. Mini Review: Probes for Detecting Prymnesium parvum and Preliminary Results From Gene Expression Studies. Journal of the American Water Resources Association (JAWRA) 46(1):144-152. DOI: 10.1111/j.1752-1688.2009.00398.x Abstract: Prymnesium parvum is common in brackish and marine coastal waters within temperate zones, world-wide. P. parvum forms recurrent blooms causing fish kills in many parts of the world. Harmful blooms are formed in nutrient rich, low salinity lakes, ponds, river systems, or estuaries. Probes made to this species and to the genus Prymnesium have been tested in dot blot and fluorescent in situ hybridization (FISH) and used with a solid-phase cytometer using a tyramide signal amplification (TSA) enhanced FISH hybridization to provide a means to identify the cells before blooms develop with automated counting. Field counts from light microscopy have been compared with solid-phase cytometer counts. Additional detection systems, such as biosensors and microarrays, have also been developed to identify rapidly this species without resorting to electron microscopy. Advantages and disadvantages of each detection system are discussed. A study of the genes expressed by P. parvum under environmental conditions that can induce blooms or stress was undertaken to try to understand the ecology behind toxic blooms.     

Global Genetic Relationships Among Isolates of Golden Alga (Prymnesium parvum)1

Lutz-Carrillo, Dijar J., Gregory M. Southard, and Loraine T. Fries, 2010. Global Genetic Relationships Among Isolates of Golden Alga (Prymnesium parvum). Journal of the American Water Resources Association (JAWRA) 46(1):24-32. DOI: 10.1111/j.1752-1688.2009.00388.x Abstract: Prymnesium parvum is considered among the most harmful algal species in the world for finfish and other gill breathing organisms. Although it is globally distributed, with the exception of Antarctica, P. parvum is usually associated with coastal and brackish waters. Historically, P. parvum incidents were recorded in the eastern hemisphere; however, in 1985 it was detected in inland Texas waters. We used DNA sequence variation of the first internal transcribed spacer in the nuclear ribosomal operon (ITS1) among multiple samples of P. parvum from Texas and other locales to address the possible origins of P. parvum in Texas and the United States (U.S.). With the exception of a sample from Diversion Lake, other samples from Texas, South Carolina, and Wyoming exhibited limited genetic variation and were similar in sequence to a sample from Scotland. The Diversion Lake sample was similar in sequence to samples from Denmark and Norway, and the Maine sample was highly similar to samples from England. These results suggest multiple independent introductions of P. parvum to the U.S.     

Current Status of Mathematical Models for Population Dynamics of Prymnesium parvum in a Texas Reservoir1

Grover, James P., Jason W. Baker, Daniel L. Roelke, and Bryan W. Brooks, 2010. Current Status of Mathematical Models for Population Dynamics of Prymnesium parvum in a Texas Reservoir. Journal of the American Water Resources Association (JAWRA) 46(1):92-107. DOI: 10.1111/j.1752-1688.2009.00393.x Abstract: Blooms of the harmful alga Prymnesium parvum have apparently increased in frequency in inland waters of the United States, especially in western Texas. A suite of mathematical models was developed based on a chemostat (or continuously stirred tank reactor) framework, and calibrated with data from Lake Granbury, Texas. Inputs included data on flows, salinity, irradiance, temperature, zooplankton grazing, and nutrients. Parameterization incorporated recent laboratory studies relating the specific growth rate of P. parvum to such factors. Models differed in the number of algal populations competing with P. parvum, and whether competition occurred only by consumption of shared nutrients, or additionally through production of an allelopathic chemical by one of the populations, parameterized as cyanobacteria. Uncalibrated models did not reproduce the observed seasonal dynamics of P. parvum in Lake Granbury, which displayed a maximum population in late February during a prolonged bloom in cooler weather, and reduced abundance in summer. Sensitivity analyses suggested two modifications leading to predictions that better resembled observations. The first modification greatly reduces the optimal temperature for growth of P. parvum, an approach that disagrees with laboratory experiments indicating a strong potential for growth at temperatures above 20°C. The second modification increases the growth rate of P. parvum at all temperatures, in models including cyanobacterial allelopathy. Despite these adjustments, calibrated models did not faithfully simulate all features of the seasonal dynamics of P. parvum.     

Prymnesium parvum: The Norwegian Experience1

Johnsen, Torbjørn M., Wenche Eikrem, Christine D. Olseng, Knut E. Tollefsen, and Vilhelm Bjerknes, 2010. Prymnesium parvum: The Norwegian Experience. Journal of the American Water Resources Association (JAWRA) 46(1):6-13. DOI: 10.1111/j.1752-1688.2009.00386.x Abstract: In Norwegian waters, Prymnesium parvum has been reported from Oslofjorden in the south to Spitzbergen in the north. However, blooms of P. parvum have only been reported from the Sandsfjorden system in Ryfylke, Western Norway where the salinity of the permanent brackish layer (2-5 m) typically is in the range of 4-7 psu during the summer months. The first bloom on record occurred in 1989, and it killed 750 metric tons of caged salmon and trout which was a significant economic loss to the fish farming industry. Toxic blooms occurred as well in subsequent years and the number of fish farms in the area decreased considerably as did the occurrence of P. parvum. In 2005, fish farming was reintroduced to the area and again, in 2007 a toxic bloom of P. parvum killed 135 metric tons of caged fish. The Norwegian Institute for Water Research has, in collaboration with “Erfjord Stamfisk” fish farm, set up a monitoring program that includes light microscopy cell counts of Prymnesium, water quality measurements, and observation of the caged fish. A submergible fish net was mounted over the fish pens and during the toxic outbreak of P. parvum in July-August 2007, which was as previous years confined to the upper brackish water layer, the fish nets were lowered to 10 m depths below the surface and fish feeding was temporarily stopped. Despite substantial weight loss, the fish survived the toxic bloom and the economic loss was minimal. Monitoring of P. parvum bloom dynamics in 2007 revealed that populations were initially dominated by the nonmotile forms which were gradually replaced by the flagellated forms. Toxicity was observed when the flagellated cells dominated populations in the summer. Chrysochromulina, solitary small Chaetoceros species, and small centric diatoms co-existed with P. parvum during the monitoring period (June-October).     

Comparative Toxicity of Prymnesium parvum in Inland Waters1

Brooks, Bryan W., Susan V. James, Theodore W. Valenti, Jr., Fabiola Urena-Boeck, Carlos Serrano, Jason P. Berninger, Leslie Schwierzke, Laura D. Mydlarz, James P. Grover, and Daniel L. Roelke, 2010. Comparative Toxicity of Prymnesium parvum in Inland Waters. Journal of the American Water Resources Association (JAWRA) 46(1):45-62. DOI: 10.1111/j.1752-1688.2009.00390.x Abstract: Numerous studies have examined the impacts of Prymnesium parvum to aquatic life, but the majority of information available is from experiments or field studies performed at salinities of marine and coastal ecosystems. Ambient toxicity of P. parvum has been characterized with in vitro and in vivo models because reliable quantitation of P. parvum toxins in environmental matrices is often precluded by a lack of available analytical standards. Hemolytic activity and fish mortality assays have been used most frequently to characterize toxic conditions; however, relatively few in vivo studies employed standardized methods. Because the relative sensitivities of different taxa to P. parvum toxins in inland waters were undefined, we assessed the comparative toxicity of P. parvum filtrate from a laboratory study (20°C, 12:12 light:dark cycle, f/8 media, 2.4 psu) to several common standardized in vitro and in vivo models. After exposure to cell-free filtrate hemolytic activity (1 h EC₅₀ = 13,712 cells/ml) and juvenile fish (Pimephales promelas) survival (48 h LC₅₀ = 21,754 cells/ml) were the most sensitive assay responses examined, followed by rotifer (Brachionus calyciflorus) population growth rate [48 h no observable adverse effect levels (NOAEL) = 19,072 cells/ml] and cladoceran (Daphnia magna) reproduction (10-day NOAEL = 47,680 cells/ml). Green algae (Pseudokirchneriella subcapitata) growth (96 h) was not adversely affected but was instead significantly stimulated by P. parvum toxins. We further propose an initial species sensitivity distribution approach for P. parvum, which may be used to support future environmental management decisions. Our findings from these laboratory studies indicate that although fish kills are increasingly associated with P. parvum blooms occurring in inland waters, further study is required to define the influences of toxin sensitivities of phytoplankton, zooplankton, and fish communities on P. parvum bloom initiation and termination.     

Potential Methods for Managing Prymnesium parvum Blooms and Toxicity,With Emphasis on Clay and Barley Straw: A Review1

Hagström, Johannes A., Mario R. Sengco, and Tracy A. Villareal, 2010. Potential Methods for Managing Prymnesium parvum Blooms and Toxicity, With Emphasis on Clay and Barley Straw: A Review. Journal of the American Water Resources Association (JAWRA) 46(1):187-198. DOI: 10.1111/j.1752-1688.2009.00402.x Abstract: Harmful algal bloom (HAB) control and mitigation is a complex problem in ecosystem management. Phytoplankton play an important role in aquatic ecosystems as primary producers and food sources for many commercially important shellfish and there are limited options for targeting just a single species within the community. Chemical treatments (e.g., algaecides), rotting barley straw, nitrogen and phosphorus manipulation, and clay and/or flocculants are but a few techniques tested or used to reduce fish kills or shellfish contamination during a HAB event. Prymnesium parvum control has focused on the use of chemicals, nutrient manipulation, and clay flocculation. However, many HAB control methods have been rejected due to their effects on ecosystems, high costs, or limited effects on target organisms. For example, rotting barley straw (Hordeum vulgare) is considered to be an environmentally friendly alternative, but has been found to have very different results on the phytoplankton community depending on the dominating taxa and is ineffective against P. parvum and dinoflagellate blooms. Clay flocculation is a useful control/mitigation technique during fish kills in marine aquaculture sites in South Korea and can be effective in freshwater if the correct combination of clay and flocculent is used. Toxins produced by P. parvum and Karenia brevis also bind to phosphatic clay, thereby removing and/or neutralizing the toxins, but there is concern that the clay will have a negative effect on sessile organisms. Some shellfish suffer high mortalities and significant impacts on somatic and reproductive tissue growth at high clay loads; however, benthic communities appear to be unchanged after five years of clay treatment in South Korea. There are likely site-specific and ecosystem-specific characteristics that make generalizations about control options difficult and require careful assessment of options at each location.     

Prymnesium parvum Control Treatments For Fish Hatcheries1

Barkoh, Aaron, Dennis G. Smith, and Gregory M. Southard, 2010. Prymnesium parvum Control Treatments for Fish Hatcheries. Journal of the American Water Resources Association (JAWRA) 46(1):161-169. DOI: 10.1111/j.1752-1688.2009.00400.x Abstract: In 2001, the ichthyotoxic microalga Prymnesium parvum caused massive fish kills and adversely affected fish production at the Texas Parks and Wildlife Department (TPWD) Dundee State Fish Hatchery. Since then, we have investigated several P. parvum bloom and ichthyotoxicity control treatments to develop management strategies that allow fish production and prevent the spread of the alga into unaffected hatcheries and impoundments. Current control successes include treatments for ponds, water supply, and a hazard analysis and critical control point program. For pond treatment, ammonium sulfate (as 0.14-0.25 mg/l un-ionized ammonia nitrogen for temperatures above 15°C), copper sulfate (2 mg/l), Cutrine^®-Plus (0.2-0.4 mg/l as copper), or potassium permanganate (3 mg/l above the potassium permanganate demand) controls P. parvum blooms. Copper sulfate at 1 mg/l controls P. parvum but is unable to eliminate ichthyotoxicity whereas potassium permanganate at 2 mg/l above the potassium permanganate demand controls ichthyotoxicity. For water treatment, ultraviolet (UV) light at 193-220 mJ/cm² doses or ozone at 0.4-1.2 mg/l for 6 min destroy P. parvum cells and reduce or eliminate ichthyotoxicity. A combination UV and ozone treatment appears to provide the best results; however, successful treatments depend on dosage relative to cell density and toxin concentration. To prevent the spread of the alga, hatchery fish delivery units and equipment are cleaned with household bleach (10% solution for 15 minutes) or hydrogen peroxide (62.5-12,500 mg/l for 0.25-24 hours). These treatments are tailored to water quality conditions and the fish species cultured at affected TPWD hatcheries. We recommend that other users test these treatments before applying them to ponds or other impoundments containing fish or other aquatic life.     

Comparison of Three Algaecides for Controlling the Density of Prymnesium parvum1

Rodgers, John H., Jr., Brenda M. Johnson, and West M. Bishop, 2010. Comparison of Three Algaecides for Controlling the Density of Prymnesium parvum. Journal of the American Water Resources Association (JAWRA) 46(1):153-160. DOI: 10.1111/j.1752-1688.2009.00399.x Abstract: Prymnesium parvum has become more prevalent in water resources of the southern United States. As the potential impacts of P. parvum are relatively well known, especially its capability to severely affect fish, managers have sought efficacious, environmentally sound, and socially acceptable strategies for mitigating this noxious species. Laboratory testing was used to identify an effective algaecide for control of P. parvum from Texas, Arizona, Florida, North Carolina, and South Carolina. Cutrine^®-Plus at 0.2 mg Cu/l significantly decreased the density of P. parvum in samples from all of these locations. Both copper sulfate and Phycomycin^® were less effective for controlling the population growth of P. parvum. The predicted response from the laboratory study was confirmed in the field at the Arizona site. Strategic use of Cutrine^®-Plus in larger water resources could provide toxin-free refugia to allow some fish to survive and repopulate the water resource when the golden alga infestation abates.     

Influence of Prey and Nutritional Status on the Rate of Nitrogen Uptake by Prymnesium parvum (haptophyte)1

Lindehoff, Elin, Edna Granéli, and Patricia M. Glibert, 2010. Influence of Prey and Nutritional Status on the Rate of Nitrogen Uptake by Prymnesium parvum (Haptophyte). Journal of the American Water Resources Association (JAWRA) 46(1):121-132. DOI: 10.1111/j.1752-1688.2009.00396.x Abstract: We studied how the specific nitrogen (N) uptake rates of nitrate (NO₃⁻), urea, and the amino acids, glutamic acid and glycine, by Prymnesium parvum were affected by (1) the change from N-deficient status to N-sufficient status of the P. parvum cells, (2) presence of prey from a natural Baltic Sea plankton community, and (3) the composition of prey as affected by additions of terrestrial originated dissolved organic matter (DOM) or inorganic nutrients. Nitrogen-deficient P. parvum (16 μM NO₃⁻ and 4 μM PO₄⁻, molar N:P ratio of 4:1) were mixed with a natural Baltic plankton community and given PO₄³⁻ and (1) NO₃⁻ (control) or (2) high molecular weight DOM, >1 kDa concentrated from sewage effluent (+DOM), in a molar N:P ratio of 9-10:1. With additions of ¹⁵N-enriched substrates, rates of N uptake from NO₃⁻, urea, and the amino acids glycine and glutamic acid were measured every 24 h for 72 h. Initial N-deficient P. parvum were highly toxic (3.7 ± 0.9 × 10⁻⁴ mg Sap equiv/cell) and toxic allelochemicals were released into the medium causing the natural plankton community to lyse. Rates of N uptake differed between the “control” and the “+DOM” treatments over time; total (sum of the N substrates measured) absolute uptake rates (ρ_cell, fmol N/cell/h) at ambient culture conditions were significantly higher (ANOVA, p < 0.05) in the more toxic “control” treatments compared with the “+DOM” treatments after 48 h. In the “control” treatment, the total ρ_cell increased significantly (ANOVA, p < 0.01) from time 0 to 48 h, while in the “+DOM” treatment there was no significant increase. Released organic nutrients from the lysed plankton cells may have increased uptake rates of amino acids and urea by P. parvum. All uptake rates declined in all treatments by 72 h. Total dissolved N uptake rates at ambient culture conditions were estimated to make up about 10% of the N P. parvum are potentially capable of ingesting from particulate prey.     

Combining Flow Cytometry and Real-Time PCR Methodology to Demonstrate Consumption by Prymnesium parvum1

Bowers, Holly A., Andreas Brutemark, Wanderson F. Carvalho, and Edna Granéli, 2010. Combining Flow Cytometry and Real-Time PCR Methodology to Demonstrate Consumption by Prymnesium parvum. Journal of the American Water Resources Association (JAWRA) 46(1):133-143. DOI: 10.1111/j.1752-1688.2009.00397.x Abstract: Harmful algal bloom species can persist in the environment, impacting aquatic life and human health. One of the mechanisms by which some harmful algal bloom species are able to persist is by consumption of organic particles. Methods to demonstrate and measure consumption can yield insight into how populations thrive. Here, we combine flow cytometry and real-time PCR to demonstrate consumption of a cryptophyte species (Rhodomonas sp.) by a toxic mixotrophic haptophyte (Prymnesium parvum). Using flow cytometry, the feeding frequency of a population of P. parvum cells was calculated using the phycoerythrin (PE) fluorescence signal from Rhodomonas sp. and the fluorescence of an acidotropic probe labeling the food vacuoles. Feeding frequency increased in the beginning of the experiment and then began to decline, reaching a maximum of 47.5% of the whole P. parvum population after 212 min. The maximum number of consumed Rhodomonas sp. cells was 0.8 per P. parvum cell, and occurred after 114 min corresponding to an ingestion rate of 0.4 Rhodomonas sp. cells/P. parvum/h. Cells from the feeding P. parvum population were sorted, washed, and subjected to a real-time PCR assay targeting the cryptophyte 18S locus. There was a correlation between cycle threshold (Ct) values and number of consumed prey cells calculated by fluorescence. Overall, this study shows that flow cytometric analysis, of the acidotropic probe and prey pigments, is an efficient and rapid tool in enumerating food vacuoles and the number of prey cells consumed. Furthermore, we suggest that real-time PCR can be applied to cells sorted by flow cytometry, thus allowing for the detection and potential quantification of the targeted prey cells.     

Spatiotemporal Associations of Reservoir Nutrient Characteristics and the Invasive,Harmful Alga Prymnesium parvum in West Texas

Golden alga (Prymnesium parvum) is a harmful alga that has caused ecological and economic harm in freshwater and marine systems worldwide. In inland systems of North America, toxic blooms have nearly eliminated fish populations in some systems. Modifying nutrient profiles through alterations to land or water use may be a viable alternative for golden alga control in reservoirs. The main objective of this study was to improve our understanding of the nutrient dynamics that influence golden alga bloom formation and toxicity in west Texas reservoirs. We examined eight sites in the Upper Colorado River basin, Texas: three impacted reservoirs that have experienced repeated golden alga blooms; two reference reservoirs where golden alga is present but nontoxic; and three confluence sites downstream of the impacted and reference sites. Total, inorganic, and organic nitrogen and phosphorus and their ratios were quantified monthly along with golden alga abundance and ichthyotoxicity between December 2010 and July 2011. Blooms persisted for several months at the impacted sites, which were characterized by high organic nitrogen and low inorganic nitrogen. At impacted sites, abundance was positively associated with inorganic phosphorus and bloom termination coincided with increases in inorganic nitrogen and decreases in inorganic phosphorus in late spring. Management of both inorganic and organic forms of nutrients may create conditions in reservoirs unfavorable to golden alga.     

Associations between Water Physicochemistry and Prymnesium parvum Presence,Abundance, and Toxicity in West Texas Reservoirs

Toxic blooms of golden alga (Prymnesium parvum) have caused substantial ecological and economic harm in freshwater and marine systems throughout the world. In North America, toxic blooms have impacted freshwater systems including large reservoirs. Management of water chemistry is one proposed option for golden alga control in these systems. The main objective of this study was to assess physicochemical characteristics of water that influence golden alga presence, abundance, and toxicity in the Upper Colorado River basin (UCR) in Texas. The UCR contains reservoirs that have experienced repeated blooms and other reservoirs where golden alga is present but has not been toxic. We quantified golden alga abundance (hemocytometer counts), ichthyotoxicity (bioassay), and water chemistry (surface grab samples) at three impacted reservoirs on the Colorado River; two reference reservoirs on the Concho River; and three sites at the confluence of these rivers. Sampling occurred monthly from January 2010 to July 2011. Impacted sites were characterized by higher specific conductance, calcium and magnesium hardness, and fluoride than reference and confluence sites. At impacted sites, golden alga abundance and toxicity were positively associated with salinity‐related variables and blooms peaked at ~10°C and generally did not occur above 20°C. Overall, these findings suggest management of land and water use to reduce hardness or salinity could produce unfavorable conditions for golden alga.     

Aspects of The Origins,Ecology, And Control Of Golden Alga Prymnesium parvum: Introduction To The Featured Collection1

Barkoh, Aaron and Loraine T. Fries, 2010. Aspects of the Origins, Ecology, and Control of Golden Alga Prymnesium parvum: Introduction to the Featured Collection. Journal of the American Water Resources Association (JAWRA) 46(1):1-5. DOI: 10.1111/j.1752-1688.2009.00394.x     

Potential Impacts of Stormwater Runoff on Water Quality in Urban Sand Pits and Adjacent Groundwater1

Whittemore, Donald O., 2012. Potential Impacts of Stormwater Runoff on Water Quality in Urban Sand Pits and Adjacent Groundwater. Journal of the American Water Resources Association (JAWRA) 48(3): 584-602. DOI: 10.1111/j.1752-1688.2011.00637.x Abstract: Entrance of stormwater runoff into water-filled pits and adjacent aquifers is a contamination concern. The water and sediment quality in several sand pits and surrounding groundwater in Wichita, Kansas, were studied to comprehensively address stormwater runoff impact. The pits are used for residential development after sand and gravel mining. Water samples were analyzed for inorganic constituents, bacteria, and 252 organic compounds, and pit sediments for inorganic components and 32 organic chemicals. Although many pesticide and degradate compounds were found in the pit and well waters, none of these chemicals exceeded existing health levels. Other organic contaminants were detected in the waters, with those exceeding health levels at one site attributed to an undiscovered groundwater contamination plume and not to stormwater runoff. Persistent insecticides and polychlorinated biphenyls detected in sediment of two pits are related to the age of residential development. The concentration distributions of pesticides and other organics at most of the sites, as well as iron, manganese, and ammonia patterns in downgradient well waters relative to upgradient well and pit waters, indicate that groundwater quality at the sites is affected by contaminants entering the pit surface waters. Thus, although current stormwater runoff does not appear to have contaminated sand-pit water and adjacent groundwater above health levels, the data show that the potential exists if stormwater became polluted.     

Factors Influencing Allelopathy and Toxicity in Prymnesium parvum1

Granéli, Edna and Paulo S. Salomon, 2010. Factors Influencing Allelopathy and Toxicity in Prymnesium parvum. Journal of the American Water Resources Association (JAWRA) 46(1):108-120. Abstract: Some microalgae are able to kill or inhibit nutrient-competing microalgae, a process called allelopathy. Inhibiting or killing competitors enable these species to monopolize limiting resources, such as nitrogen and phosphorus. Prymnesium parvum is known to produce such allelopathic compounds, substances that seem identical to the ichthyotoxins identified from this species. Biotic and abiotic environmental factors influence not only growth rates but also toxin/allelopathic compounds production by P. parvum cells. Toxin production, as well as allelopathy, including grazer deterrence, increases dramatically in light, temperature, or nutrient stressed P. parvum cells. Correspondingly, toxicity and allelopathy may decrease, or cease completely, if cells are grown with high amounts of N and P in balanced proportions. However, even under nutrient (N and P) sufficient conditions, P. parvum is able to produce toxins/allelopathic compounds, with negative effects on other phytoplankton species or grazers, if cells densities of P. parvum are high relative to other species. This negative effect might shift the plankton community to more toxin resistant species. Filtrates from nutrient-deficient P. parvum cultures have almost the same strong negative effect on grazers and other phytoplankton species as when Prymnesium cells are grown together with the target organisms. Eutrophication, the increased input of N and P to aquatic ecosystems, besides increasing nutrient concentrations, is usually provoking unbalanced N:P condition for the optimal growth of phytoplankton, deviating from the Redfield ratio, i.e., the phytoplankton cellular nitrogen to phosphorus ratio, N:P = 16:1 (by atoms) or 7.2:1 (by weight). Eutrophication thus both enhances P. parvum growth and increases production of toxins and allelopathic compounds. Supplying N-deficient or P-deficient P. parvum cells with the deficient nutrient reduces toxicity to less than half within 24 h after additions. As P. parvum is mixotrophic, uptake of dissolved or particulate organic N (DON or PON) can also reduce toxicity and allelopathy in the same manner as addition of inorganic N to N-starved cells. In conclusion, P. parvum, by increasing its toxicity and allelopathic ability under poor environmental conditions, outcompetes the co-occurring phytoplankton species.     

Prymnesium parvum: The Texas Experience1

Southard, Gregory M., Loraine T. Fries, and Aaron Barkoh, 2010. Prymnesium parvum: The Texas Experience. Journal of the American Water Resources Association (JAWRA) 46(1):14-23. DOI: 10.1111/j.1752-1688.2009.00387.x Abstract: Golden alga Prymnesium parvum was first identified in Texas during a fish kill investigation on the Pecos River in 1985. Since then golden alga kills occurred sporadically in a variety of waters in the western part of the state until 2001 when the alga became endemic in the Brazos, Canadian, Colorado, Red, and Rio Grande river systems, including the water supplies of two public fish hatcheries, the Possum Kingdom and Dundee state fish hatcheries. The increasing area adversely affected by the alga and frequent massive fish kills heightened public and political awareness and concerns regarding the ecological and economic impacts of P. parvum blooms. The Texas Parks and Wildlife Department (TPWD), the wildlife conservation agency of the state, responded to these concerns with a program to assess the ecological and economic impacts and to develop management options. To date 33 water bodies have been affected and losses are conservatively estimated at 34 million fish valued at US$13 million. Several sport fisheries, including smallmouth bass Micropterus dolomieu, striped bass Morone saxatilis, channel catfish Ictalurus punctatus, and blue catfish Ictalurus furcatus, have been severely affected. Additionally, 26 imperiled fish species occur in the affected water basins and some have been adversely affected. Economic losses associated with reduced fishing and other water-based recreational activities appear considerable. The combined economic losses to three counties (Palo Pinto, Stephens, and Young) surrounding Possum Kingdom reservoir for 2001 and 2003 were estimated at US$2.8 million and US$1.1 million, respectively. This paper describes how the TPWD responded to public and political concerns relative to the emergence of golden alga, its harmful effects to fisheries, and its historic and current statewide distribution.     

Refining Nitrogen and Phosphorus Fertilization Strategies for Controlling the Toxigenic Alga Prymnesium parvum1

Kurten, Gerald L., Aaron Barkoh, Drew C. Begley, and Loraine T. Fries, 2010. Refining Nitrogen and Phosphorus Fertilization Strategies for Controlling the Toxigenic Alga Prymnesium parvum. Journal of the American Water Resources Association (JAWRA) 46(1):170-186. DOI: 10.1111/j.1752-1688.2009.00401.x Abstract: Previous studies have shown that three times weekly applications of phosphorus (30 μg P/l) and nitrogen (300 μg N/l) were effective at reducing the density and toxicity of the alga Prymnesium parvum in limnocorrals simulating a 40-day moronid (e.g., striped bass, Morone saxatilis, and palmetto bass, M. saxatilis ×Morone chrysops) fingerling culture period. However, this fertilization regime produced high pH and unionized ammonia-N concentrations that are detrimental to the survival of moronid fry and fingerlings. In two follow-up experiments we changed the source of N from ammonia to nitrate, reduced fertilization rates, and examined the effect of N-only or P-only fertilization. In the first experiment P fertilization rates were reduced by one-half to 15 μg P/l and NO₃-N was substituted for NH₃-N at the previously used rate of 300 μg N/l. In the second experiment, N fertilization rates were reduced to 150 μg N/l and the frequency of fertilization was determined by pH and P. parvum responses. Nitrate appeared to be as effective as ammonia as a source of N and when used in combination with P reduced P. parvum cell density and ichthyotoxicity. However, reduced N and P application rates and lower pond water temperatures during the study appeared to have decreased the speed at which fertilization produced these effects. While lower fertilization rates reduced algal productivity, high pH remained a concern for fish culture although pH was reduced to levels that might be acceptable with careful management of fish culture activities. Neither N-only nor P-only fertilization had a measurable effect on algal productivity or eliminated P. parvum and its toxicity. Furthermore, P-only fertilization may have increased P. parvum density and toxicity. For controlling P. parvum density and ichthyotoxicity we recommend a fertilization rate of 212 μg NO₃-N/l plus 30 μg PO₄-P/l applied three times weekly for aquaculture ponds where high pH is not a concern. Where high pH is a concern we recommend a fertilization rate of 117 μg NO₃-N/l plus 16 μg PO₄-P/l applied three times weekly with careful attention to afternoon pond pH.     

STORM AND SEASONAL DISTRIBUTIONS OF FECAL COLIFORMS AND CRYPTOSPORIDIUM IN A SPRING1

ABSTRACT: The transmission of disease in ground water is a topic of great concern to government agencies, ground water specialists, and the general public. The purpose of this study was to compare the temporal variability in storm flow of fecal coliform bacteria densities and Cryptosporidium parvum oocyst densities in agriculturally impacted karst ground water. Cryptosporidium parvum oocyst densities ranged from 0 to 1,050 oocysts/1, and mean storm densities ranged from 3.5 to 156.8 oocysts/1. Fecal coliform densities ranged from less than 1 CFU/100ml to more than 40,000 CFU/100ml, and geometric mean storm densities ranged from 1.7 CFU/100ml to more than 7,000 CFU/100ml. Fecal coliform densities correlated well with flow during storms, but Cryptosporidium oocyst densities exhibited a great deal of sample to sample variability and were not correlated with flow. Fecal coliform densities did not correlate positively with Cryptosporidium oocyst densities. Fecal coliform densities were greatest at storm peaks, when sediment loads were also greatest. Multiple transport mechanisms for fecal coliform bacteria and C. parvum oocysts may necessitate various agricultural land management and livestock health maintenance practices to control movement of pathogens to karst ground water.