Browsing by Subject "Phytoplankton"

Now showing 1 - 7 of 7
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    An Assessment of Phytoplankton Nutrient Deficiency in Northern Minnesota Acid-Sensitive Lakes
    (University of Minnesota Duluth, 1991) Axler, Richard P; Tikkanen, Craig A; Rose, Charles
    The Northern Lakes and Forests ecoregion of Minnesota contains thousands of lakes, characterized by their sensitivity to acid rain, and their typically low productivity. Four acid- sensitive lakes were studied for 1988-1991 to determine if phytoplankton were deficient in nitrogen, phosphorus, or both N and P, and if nutrient input via atmospheric deposition could increase primary production. The relative accuracy of predictions based on growth response bioassays, physiological assays, and nutrient deficiency indices was also evaluated. Our results show that: (1) N enrichment generally caused a greater biomass response than P, although N+P almost always yielded the greatest effect and co-limitation was likely in two of the lakes; (2) predictions based on DIN:TP ratios generally agreed with the growth bioassays, TN:TP and DIN:SRP were not useful and could be misleading; and (3) atmospheric deposition could satisfy most of the daily algal N demand and increase the fertility of these lakes. These results suggest that although water quality protection based solely upon phosphorus may not protect against this non-point source of nutrients, without these control strategies, P-inputs would be expected to have a disproportionally greater impact on phytoplankton growth.
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    Final Data Summary Report: Phytoplankton Monitoring in the Great Lakes: 2007-2012 Funding Years
    (University of Minnesota Duluth, 2013) Reavie, Euan D
    The Laurentian Great Lakes have a long record of adverse anthropogenic impacts on water quality and food webs. Tracking these impacts and their causes is critical so that remedial efforts can be directed where and how they are most needed. The EPA’s Great Lakes National Program Office (GLNPO) is now in its 30th year of comprehensive monitoring of the Great Lakes. Pelagic monitoring includes physical and chemical parameters, phytoplankton, zooplankton, benthic invertebrates and other measurements. These monitoring data have revealed significant changes in whole-lake conditions (e.g. Barbiero et al. 2009), thus justifying GLNPO’s mandate to track changes under the Great Lakes Water Quality Act of 1978. Specifically, phytoplankton collections provide important information on the primary food source at the bottom of the food web, and we aim to track long-term changes in the phytoplankton resulting from human influences, and so characterize causes of disturbance, their impacts, and remedial necessity. Phytoplankton are known to respond to stressors such as nutrient loading and invasive species, and ultimately integration with other program components (e.g., zooplankton, water quality) will allow the evaluation of interactions among trophic levels and provide a more holistic interpretation of causal factors in biological changes. The abbreviated objectives of the phytoplankton program are to: 1) collect phytoplankton from the Great Lakes in spring and summer excursions on board the R/V Lake Guardian; 2) identify and enumerate phytoplankton, maintaining quality assurance standards; 3) maintain and provide a database of phytoplankton data; 4) interpret phytoplankton data, including evaluation of long-term trends in phytoplankton and food web dynamics; and 5) dissemination of data and interpretations through reports, presentations and peer-reviewed journals so that results are available for aquatic management considerations. This report summarizes phytoplankton data collected under the USEPA’s Open Lake Water Quality Survey of the Great Lakes. Those unfamiliar with the project are directed to http://www.epa.gov/glnpo/monitoring/sop for a detailed background of the overall project goals, ideology and methods. Data and analyses in this report were generated by the Natural Resources Research Institute (NRRI), University of Minnesota Duluth (UMD) under the direction of Euan Reavie (Senior Research Associate -- NRRI), and this report fulfills the final task as agreed in cooperative agreement GL-00E23101-2.
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    The integral role of phytoplankton stoichiometry in ocean biogeochemical dynamics
    (2019-11) Tanioka, Tatsuro
    Photosynthesis by ocean algae (phytoplankton) contributes roughly half of the earth's net carbon production. Organic matter produced using carbon dioxide in the atmosphere not only supports marine food webs, but also acts as a climate stabilizer, because carbon is subsequently transported to the deep ocean and stored there for thousands of years. Attempts to model global marine biological production and its impacts on global biogeochemical cycles often assume a constant elemental stoichiometry of carbon, nitrogen, and phosphorus in phytoplankton biomass. This ratio, known as the Redfield ratio, was determined on the basis of an analysis of many samples of marine plankton collected over 70 years ago. This notion is well established in the oceanographic community but there is no clear physiological justification for why the C:N:P ratios in phytoplankton should strictly follow the Redfield ratio. Many recent studies revealed that C:N:P ratio of particulate organic matter can deviate significantly from the Redfield Ratio with some noticeable spatial and temporal variability. Studies suggest that factors such as nutrient availability, light, and temperature play a crucial role in modifying C:N:P ratio of phytoplankton. In this dissertation, I investigate the roles of marine phytoplankton stoichiometry in the global marine biogeochemical dynamics by combining meta-analysis, numerical modeling, and remote sensing. I propose a mechanistic framework for predicting C:N:P in phytoplankton under different environmental conditions and I incorporate this framework into an Earth System Model to show their effects on global carbon cycle. I also present results on how the change in elemental composition of phytoplankton could affect the feeding behavior of zooplankton as well the ecosystem stoichiometry. Finally, I show that C:N:P is closely tied to the rate at which oxygen is consumed during organic matter remineralization and I propose that the change in phytoplankton stoichiometry could ameliorate the rate of marine deoxygenation. In summary, C:N:P of phytoplankton is flexible and will play key roles in future global ocean biogeochemical dynamics.
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    The intersection of climate change, watershed influence, and phytoplankton dynamics in Lake Superior
    (2021-06) Reinl, Kaitlin
    Climate change is leading to ecological shifts in lakes including altered thermal regimes, nutrient cycles, and food web structure. I explore how climate change is impacting phytoplankton dynamics in Lake Superior. I show that there are clear seasonal patterns in the development and degradation of the deep chlorophyll layer (DCL) and that as water temperatures warm there is a restructuring of the DCL, with a smaller thickness and greater maximum concentration at warmer temperatures. My research also shows that biological loading from rivers to Lake Superior may be an important source of seed populations for cyanobacterial blooms, particularly those characterized by low water temperature and high conductivity. Finally, I present a life cycle model to predict cyanobacterial blooms that integrates monitoring data and cyanobacteria life cycle stages. The model highlights the importance of phosphorus loading in promoting blooms and shows that akinete production may result in a decrease in peak summer vegetative biomass. This work lays the critical groundwork for understanding the impact of climate change on phytoplankton dynamics and their ecological implications.
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    Mid-project Data Report: Phytoplankton Monitoring in the Great Lakes
    (University of Minnesota Duluth, 2009) Reavie, Euan D
    This report is intended for audiences who are familiar with the USEPA’s Open Lake Water Quality Survey of the Great Lakes. Those unfamiliar with the project are directed to http://www.epa.gov/glnpo/monitoring/sop for a detailed background of the overall project goals, ideology and methods. This report fulfils the task of “Preliminary Report” (due July 28, 2009) as agreed in contract GL-00E23101-2. Results herein focus on 2007 phytoplankton data from GLNPO’s Great Lakes open water biological monitoring program. The main objectives of this report are to (1) present general characteristics of the 2007 phytoplankton assemblages, (2) reconstruct long-term phytoplankton trends in the context of phytoplankton data collected prior to 2000, and (3) use various observational and statistical techniques to confirm that data quality objectives, mainly taxonomic consistency, have been met. Since the initiation of the University of Minnesota Duluth’s (UMD) involvement in the monitoring program, significant efforts have been allocated to taxonomic assurance. Following the transition of the project to a new contractor in 2001, several data quality issues related to inconsistencies in taxonomic identifications arose resulting in temporary termination of the phytoplankton program in 2004. Part of UMD’s agreement was to ensure that the new phytoplankton data collected in 2007 meet specific taxonomic criteria. In other words, taxonomy for 2007 needed to match that from pre-2000 samples so that long-term analyses were reliable. It is our opinion that we have met taxonomic criteria and that, with continued taxonomic workshops, we are building a reliable long-term phytoplankton database that will be a valuable tool to track ecological shifts in the lakes.
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    Report of the Land-Based Freshwater Testing by the Great Ships Initiative of the Siemens SiCURE(TM) Ballast Water Management System for Type Approval According to Regulation D-2 and the Relevant IMO Guidelines
    (University of Minnesota Duluth, 2010) Cangelosi, Allegra
    The Great Ships Initiative (GSI) provides independent no-cost performance verification testing services to developers of ballast treatment systems and processes at a purpose-built, land-based ballast treatment test facility located in the Duluth-Superior Harbor of Lake Superior. GSI test protocols are consistent with the requirements of the International Convention for the Control and Management of Ships Ballast Water and Sediments (International Maritime Organization, 2004). GSI procedures, methods materials and findings are publicly accessible on the GSI website (www.greatshipsinitiave.org). In August through October 2009, the GSI conducted land-based tests on the SiCURETM Ballast Water Management System in cooperation with German Bundesamt für Seeschifffahrt und Hydrographie (BSH), i.e., the German Federal Maritime and Hydrographic Agency. During the series of five consecutive valid trials, the SiCURETM Ballast Water Management System was evaluated for its ability to: (a) successfully treat ballast water without interruption, (b) meet IMO D-2 discharge standards after a five-day holding time, and (c) discharge water after the five day retention period that is environmentally benign (i.e., no residual toxicity) pursuant to United States Environmental Protection Agency water quality criteria. It should be noted that because freshwater zooplankton are in general smaller than their salt and brackish water counterparts, the larger regulated size category (greater than 50 μm in minimum dimension) did not incorporate all live zooplankton that were present in the source water assemblage. The Siemens SiCURETM Ballast Water Management System functioned properly during the five consecutive trials, and was highly effective at reducing live organism densities in the fresh water ambient conditions of Duluth-Superior Harbor, as amended in these tests to achieve IMOconsistent challenge conditions. Live organisms in the regulated size classes were discharged in densities below the IMO D-2 standard. Microbial analyses showed system performance in keeping with IMO requirements for bacteria. Chemistry data generated across trials indicated the post-retention discharge to have well less than 0.1 mg/L total residual chlorine (TRC) under ambient conditions. Ambient water collected immediately after treatment and held in a cold environment had TRC and total residual oxidant (TRO) levels which slightly exceeded this level. However, in a real world application, the intake water would also be cold, and developers claim that the test system is designed to respond to this circumstance (reflected in oxidation-reduction potential, or ORP) with a reduction in chlorine generated and injected into the intake stream. There were no acute toxic effects of treated discharge on any test species across assays and trials. Chronic toxicity effects in 100 % effluent were detected in one out of two trials for test species of zooplankton and phytoplankton. There were no chronic toxicity effects across organisms and trials in 50 % or lower effluent dilutions.
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    A taxon for every treatment: Influence of nutrient and temperature shifts on Great Lakes phytoplankton community composition
    (2024-09) Loiselle, Reane
    The Laurentian Great Lakes hold over 20% of our global freshwater. Cyanobacterial harmful algal blooms (CHABs) have been some of the most significant environmental issues to threaten the health of the Great Lakes in recent decades, causing an estimated $65-71 million dollars per year in economic losses for Lake Erie alone (Bingham et al. 2015). The impact of increased temperature and nutrients on HABs has been extensively studied in recent decades. But still, little is known about how changes in temperature, nitrogen and phosphorus impact the relative abundance of specific bloom forming taxa in the Great Lakes or elsewhere. To better understand these shifts, I analyzed identical 28-day nutrient addition bioassays at ambient and plus 3 ℃ temperatures in Mawikwe Bay, Lake Superior and Sandusky Bay, Lake Erie during the summers of 2022 and 2023. This length of experiment was selected to allow for competition to take place over realistic ecological time scales to elucidate the impact of nutrients and temperature on phytoplankton competition. A FluoroProbe was used to track broad changes in phytoplankton groups every 3 days and microscopy was used to obtain detailed community information on days 0, 14, and 28. Further microscopy analyses were used to determine changes in relative abundance of dominant bloom forming species, shifts in major phytoplankton groups, and implications for associated traits.Lowering Lake Superior N:P ratios resulted in shifts from diatom dominance to increased green algae and cyanobacteria abundance, including the main bloom forming cyanobacterium Dolichospermum. This outcome indicated that the normally diatom-dominated phytoplankton community in Lake Superior is a result of intense competition for P, while P additions promote Dolichospermum abundance. In Lake Erie, Microcystis was significantly more abundant in treatments with higher N:P ratios while Dolichospermum was more abundant in treatments with lower N:P ratios. Low N:P favoring Dolichospermum in both lakes might be explained by the ability of Dolichospermum to fix nitrogen. It also suggests that P-only nutrient management in Lake Erie would likely shift the species composition of HABs from non-diazotrophic species to diazotrophic species, but not eliminate them. In contrast, P-only management in Lake Superior is likely to be effective. A several degree warming was not found to be a prominent factor in steering phytoplankton community composition in either lake, suggesting weak temperature effects on competitive outcomes over expected amounts of warming.