Browsing by Subject "Prymnesium parvum"
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Item A Study on Biological Threats to Texas Freshwater Resources(2014-01-15) Neisch, MichaelThis thesis consists of two separate experiments on unique biological threats to Texas freshwater ecosystems. The first experiment sought to understand the interaction between the harmful alga Prymnesium parvum and the cyanobacteria, Anabaena sp. The second experiment sought to determine the effectiveness of triploid grass carp, Ctenopharyngodon idella, as a biological control for two species of invasive macrophytes, which were giant salvinia, Salvinia molesta, and hygrophila, Hygrophila polysperma. Prymnesium parvum blooms have become more frequent in the south-central United States, leading to significant ecological and economic impacts. Allelopathic effects from cyanobacteria were suggested as a mechanism that might limit the development of P. parvum blooms. This research focused on the effects of cultured cyanobacteria, Anabaena sp., on P. parvum. Over a 6-d period, daily additions of filtrate from the senescent Anabaena culture were made to P. parvum cultures growing in log phase. All treatments, including several types of controls, showed reductions in P. parvum biomass over the course of the experiment, but the treatments receiving Anabaena filtrate were reduced to a lesser degree, suggesting that filtrate from the senescent cyanobacteria culture was beneficial to P. parvum in some way. Aquatic vegetation is an important component of most freshwater systems and provides numerous valuable ecosystem services, providing food, habitat and refuge for a variety of organisms. A significant threat to beneficial aquatic vegetation abundant in many United States waterways is the introduction and spread of invasive macrophytes. Two of the newest invasive species, giant salvinia (Salvinia molesta) and hygrophila (Hygrophila polysperma), have quickly established in Texas waters. This research evaluated the potential use of triploid grass carp (Ctenopharyngodon idella) as a biological control agent for these two novel invasive species. Using a controlled mesocosm experiment, consumption rates and feeding preferences were measured. Giant salvinia and hygrophila were compared to six native and introduced species common in Texas and the Southern US. Grass carp were found to be potentially useful in controlling giant salvinia in the preliminary stages of an infestation but an overall poor control option for hygrophila.Item Beyond the Edge of a Niche: The Role of Grazing on Prymnesium parvum Bloom Formations in Two Texas Lakes(2014-03-25) Davis, Stephen LouisPrymnesium parvum (golden algae) is a harmful algal bloom species that has caused tens of millions of dollars in natural resource damages in Texas as a result of massive fish kills. This species is present in many Texas lakes, but does not form blooms in all of them. Previous literature has suggested that predation, specifically by rotifers, may be an important loss factor to P. parvum populations. This research is focused on investigating whether grazing by rotifers is a significant factor in the prevention of blooms in some lakes. Three-day in-lake mesocosm experiments were conducted during times of bloom initiation and bloom development in two Texas lakes (Whitney and Somerville) where the former experiences P. parvum blooms and the latter does not. Controls and treatments consisted of P. parvum cultures in log- and stationary-growth phases, natural phytoplankton assemblages, and natural rotifer assemblages from each lake. Monitored parameters included P. parvum population density and population growth rate, toxicity, chlorophyll-a, and zooplankton biovolume. Findings reveal that rotifers in Lake Somerville preferentially grazed P. parvum of all growth phases, while experiencing no negative effects from exposure. Some rotifers even exhibited trends of positive effects from exposure. The mesocosm experiments confirmed that rotifer assemblages in Lake Somerville effectively graze P. parvum with no observed negative effects. These findings support the theory that grazing of P. parvum by rotifers is an important contributing factor preventing blooms in Lake Somerville. On the other hand, rotifers from the winter Lake Whitney experiment appeared to preferentially graze P. parvum populations inoculated from log-growth phase culture while significant reductions in rotifer biovolume were observed. P. parvum inoculated from stationary-growth phase culture were not significantly grazed, nor were other phytoplankton within the treatment suggesting that sub-lethal toxic effects from ingestion of stationary phase cells caused a decrease in zooplankton metabolic rates. These lake-specific relationships between P. parvum and rotifers may have been due to microevolutionary adaptation. For example, variation in biovolume responses of rotifers to P. parvum exposure between lakes is a result of rapid microevolutionary adaptation from constant low-level toxin exposure in Lake Somerville as a function of salinity.Item Deep Water Mixing Prevents Harmful Algal Bloom Formation: Implications for Managed Fisheries Refugia(2012-10-19) Hayden, Natanya JeanneInflows affect water quality, food web dynamics, and even the incidence of harmful algal blooms. It may be that inflows can be manipulated to create refuge habitat for biota trying to escape poor environmental conditions, such as fish populations in lakes during times of toxic Prymnesium parvum blooms. Water availability sometimes can be an issue, especially in arid climates, which limits this approach to management. Utilizing source water from deeper depths to displace surface waters, however, might effectively mimic inflow events. I test this notion by conducting in-lake mesocosm experiments with natural plankton communities where I manipulate hydraulic flushing. Results show that P. parvum cell density is reduced by 69%, and ambient toxicity completely ameliorates during pre-bloom conditions in the lake. During conditions of bloom development, population density is reduced by 53%, toxicity by 57%, and bloom proportions are never reached. There is minimal effect of these inflows on total phytoplankton and zooplankton biomass, and little effect on water quality. Shifts toward more rapidly growing phytoplankton taxa are observed, as are enhanced copepod nauplii. In other words, while inflows using deep waters suppress P. parvum bloom initiation and development, they are benign to other aspects of the lower food web and environment. The results from using deep lake water to suppress harmful algal blooms indicate this may be a promising management approach and further studies are recommended to test whether this mitigating effect can translate to a large-scale in-lake treatment.Item Exploring a Chemical Approach for the Mitigation of Prymnesium parvum Blooms and Ecological Considerations(2012-11-01) Umphres, George 1987-Known as Golden Algae in popular media, Prymnesium parvum causes harmful algal blooms. When stressed, it secretes increased amounts of toxic chemicals called prymnesins, which have resulted in major fish kills in Texas. Although many options exist for mitigation of blooms, a feasible protocol for control of blooms on large-scale impoundments has yet to be identified. Chemical control of P. parvum using six different enzyme inhibiting aquatic herbicides was explored in laboratory experiments. Of the six chemicals screened, one (Flumioxazin) was selected for further study due to a significant decrease in P. parvum cell numbers with increasing chemical concentration. It was applied to natural plankton communities during in-situ experiments (Lake Granbury, Texas). The first experiment was conducted during a period of P. parvum bloom initiation (March) and the second experiment conducted during a post bloom period (April). Experiments were carried out in 20 L polycarbonate carboys covered in 30% shade cloth to simulate natural light, temperature and turbulence conditions. Flumioxazin was additionally screened in the laboratory on the common game/forage fish bluegill sunfish (Lepomis macrochirus) for six weeks with weekly re-application of flumioxazin to treatment tanks. Cell counts via light-microscopy, showed the chemical flumioxazin caused significant decreases in P. parvum, but no significant differences in zooplankton abundance during the period of bloom initiation. However, significant decreases in adult copepods were observed during the post bloom period, most likely due to decreased light penetration and inhibition of the photosensitive mode of action, but no significant decreases in P. parvum. No significant effects of flumioxazin were observed on growth, survival or feed conversion ratio for L. macrochirus.Item Inhibition and success of prymnesium parvum invasion on plankton communities in Texas, USA and prymnesium parvum pigment dynamics(Texas A&M University, 2007-09-17) Errera, Reagan MichellePrymnesium parvum Carter, a haptophyte species capable of forming harmful algal blooms (HABs), has been identified in fresh and brackish water habitats worldwide. In Texas, P. parvum blooms have diminished local community revenues from losses to tourism, fishing, and hatchery production. In this thesis, P. parvum dynamics were studied using in-situ microcosm experiments at Lake Possum Kingdom, Texas during three seasons (fall, winter, spring) in 2004-2005. Specifically, nutrient additions were used to test the hypothesis that increased nutrient levels would not enhance P. parvum's ability to invade phytoplankton communities. In addition to full nutrient additions to levels of f/2 media, other treatments included nutrient additions deficient in either nitrogen (N) or phosphorus (P). Additionally, barley straw extract was tested as a growth inhibitor to prevent P. parvum blooms. Furthermore, P. parvum initial population density was examined to test the hypothesis that increased initial populations could promote an increase in P. parvum population densities. Findings indicated that P. parvum populations in Lake Possum Kingdom would not likely gain a selective advantage over other species when inorganic nutrients (nitrogen and phosphorus) were not limiting. P. parvum did, however, gain an advantage during both N- and P-limited conditions as indicated by toxicity, cell concentrations, and bulk phytoplankton community shifts. Furthermore, P. parvum blooms in Lake Possum Kingdom would likely not be inhibited by barley straw extract application. Initial population densities affected the final population density, but only when initial populations were low. A method to quickly and accurately detect the presence of P. parvum is needed due to P. parvum's potential to cause toxic and lethal blooms. This thesis tested whether P. parvum photopigments are conservative regardless of growth conditions and could be used to quantify the relative abundance of P. parvum in mixed community samples. If biomarker pigments are conservative, then an optimized version of CHEMTAX could be employed as an alternative diagnostic tool to microscopy for enumeration of P. parvum. However, P. parvum pigments in the Texas strain were not conservative throughout the growth cycle and therefore may not be a reliable indicator of cell abundance.Item Molecular and phytochemical investigations of the harmful, bloom-forming alga, Prymnesium parvum Carter (Haptophyta)(2010-08) Manning, Schonna Rachelle; La Claire, John W., 1951-; Brand, Jerry J.; Herrin, David L.; Jansen, Robert K.; Kitto, George B.This dissertation includes molecular and phytochemical investigations of the harmful, bloom-forming alga, Prymnesium parvum, including analysis of known polyketide metabolites as a function of salinity and growth. Initially, the development of molecular and phytochemical tools was necessary for the detection and quantification of P. parvum and its associated toxins. Suites of oligonucleotides and molecular beacons were designed for conventional and quantitative multiplex PCR to amplify four species- and gene-specific products simultaneously that were used for the detection and quantitation of P. parvum. This built-in redundancy provided increased confidence in reactions with the positive confirmation of four discrete products. Techniques were also developed for the chemical enrichment of toxins produced by P. parvum. Until now, isolation of “prymnesins” has never been reproduced. Polyketide prymnesins possess unique spectral properties that were used to generate an LC-MS fingerprint that comprised 13 ion species. Preliminary investigations using chemifluorimetric methods were also capable of detecting prymnesins in the pico- and nano-molar range. Environmental samples were tested as an independent assessment of these methods. Lastly, the roles of polyketide prymnesins were analyzed with respect to total hemolytic activity (HA) as a function of culture age and salinity. Variation in HA of supernatants was statistically significant relative to both variables (p << 0.05). Salinity was inversely related to HA wherein cultures growing in 5-25 psu were 150-200% more hemolytic. Total HA was inversely related to culture age during the first three weeks, but positively related to it during the next three weeks. Interestingly, no hemolysis was detected in fractions containing prymnesins from culture supernatants and the majority of hemolysins remained in the aqueous phase. Prymnesins extracted from cells varied significantly over the 6-week observation period (p << 0.05); HA was positively correlated during the first half and inversely related during the last half of the study. Salinity was directly related to HA from cell extracts, but these effects were not significantly different until the last three weeks. These investigations suggest that polyketide prymnesins are present at much lower quantities than previously believed, and they may not be the key compounds associated with hemolysis due to P. parvum.