Peter Leavitt

Permanent URI for this collectionhttps://hdl.handle.net/10294/15874

Browse

Browsing Peter Leavitt by Subject "cyanobacteria"

Filter results by typing the first few letters
Now showing 1 - 3 of 3
  • Thumbnail Image
    ItemOpen Access
    Marked blue discoloration of late winter ice and water due to autumn blooms of cyanobacteria
    (Taylor and Francis Group, 2021-11-17) Haig, Heather A.; Chegoonian, Amir M.; Davies, John-Mark; Bateson, Deirdre; Leavitt, Peter R.
    Continued eutrophication of inland waters by nutrient pollution can combine with unprecedented atmospheric and lake warming to create emergent environmental surprises. Here we report the first known occurrence of marked blue discoloration of ice and water in highly eutrophic prairie lakes during late winter 2021. Intense blue staining was reported first to governmental agencies by ice fishers in early March 2021, then communicated widely through social media, resulting in First Nations and public concern over potential septic field release, toxic spills, urban pollution, and agricultural mismanagement. Analysis of water from stained and reference sites using ultraviolet (UV)–visible spectrophotometry and high-performance liquid chromatography demonstrated that the blue color arose from high concentrations (∼14 mg/L) of the cyanobacterial pigment C-phycocyanin that was released after an unexpected bloom of Aphanizomenon flos-aquae in late October 2020 was frozen into littoral ice. Remote sensing using the Sentinel 3 A/B OLCI and Sentinel 2 A/B MSI satellite platforms suggested that blue staining encompassed 0.68 ± 0.24 km2 (4.25 ± 1.5% of lake surface area), persisted over 4 weeks, and was located within 50 m of the lakeshore in regions where fall blooms of cyanobacteria had been particularly dense. Although toxin levels were low (∼0.2 μg microcystin/L), high concentrations of C-phycocyanin raised public concern over eutrophication, pollution, and climate change, and resulted in rapid governmental and academic response. Given that climate change and nutrient pollution are increasing the magnitude and duration of cyanobacterial blooms, blue staining of lake ice may become widespread in eutrophic lakes subject to ice cover.
  • Thumbnail Image
    ItemOpen Access
    Seasonal variation in effects of urea and phosphorus on phytoplankton abundance and community composition in a hypereutrophic hardwater lake
    (Wiley, 2020-08-17) Swarbrick, Vanessa J.; Quiñones-Rivera, Zoraida J.; Leavitt, Peter R.
    1. Urea accounts for half of global agricultural fertiliser applications, yet little is known of its role in eutrophication of freshwater ecosystems, nor how it interacts with phosphorus (P) in regulating phytoplankton composition, especially during spring and autumn. 2. To identify when and how urea and P inputs interact across the ice-free period, we conducted seven monthly fertilisation experiments in 3,240-L mesocosms from ice-off to ice-formation in a hypereutrophic lake. In addition, we ran bioassays with ammonium (NH 4 +) to compare the effects of urea with those of NH 4 +, the immediate product of chemical decomposition of urea. 3. Analysis of water-column chlorophyll a and biomarker pigments by high-perfor- mance liquid chromatography revealed that addition of inorganic P alone (100 μg P L–1 week–1) had no significant impact on either algal abundance or community composition in hypereutrophic Wascana Lake. Instead, fertilisation with urea (4 mg N L−1 week–1) alone, or in concert with P, significantly (p < 0.05) increased algal abundance in spring and much of summer, but not prior to ice formation in October. In particular, urea amendment enhanced abundance of cryptophytes, chlorophytes, and non-diazotrophic cyanobacteria during April and May, while fertilisation in summer and early autumn (September) increased only chlorophytes and non-diazotrophic cyanobacteria. 4. Comparison of urea mesocosms with NH 4 + bioassays demonstrated that urea lacked the inherent toxicity of NH 4 + in cool waters, but that both compounds stimulated production during summer experiments. 5. This study showed that urea pollution can degrade water quality in P-rich lakes across a variety of seasonal conditions, including spring, and underscores the im- portance of quantifying the timing and form of N inputs when managing P-rich freshwaters.
  • Thumbnail Image
    ItemOpen Access
    Sedimentary DNA and pigments show increasing abundance and toxicity of cyanoHABs during the Anthropocene
    (Wiley, 2023-02-17) Heathcote, Adam J.; Taranu, Zofia E.; Tromas, Nicolas; MacIntyre-Newell, Meaghan; Leavitt, Peter R.; Pick, Frances R.
    1. Cyanobacterial harmful algal blooms (cyanoHABs) are assumed to be increasing in abundance and toxicity, but comprehensive analysis of change through time is limited, in part, because some key taxa (e.g., Microcystis) leave ambiguous evi- dence of historical abundance and toxicity. Sedimentary DNA (sedDNA) can allow the reconstruction of the cyanobacteria community as well as the frequency of genes specific to cyanotoxin production, enabling us to determine which taxa are present and their potential for toxin-production. 2. Using a combination of droplet digital polymerase chain reaction (ddPCR) and high-throughput sequencing (HTS), we quantified the abundance of cyanobacte- rial genes of known function and changes in cyanobacteria taxa from sedDNA over the last century in nine lakes along a gradient of lake size, depth and trophic state in Minnesota, U.S.A. Using ddPCR, we quantified genes associated with mi- crocystin toxin-producing potential (mcyE), total cyanobacteria (CYA, 16S rRNA) and the genus Microcystis (MICR, 16S rRNA). Using HTS on a subset of lakes, we investigated how the abundance of this toxin-producing gene covaried with the cyanobacteria community composition. We also compared ddPCR and HTS data to fossil pigments, a well-established palaeolimnological method used to track changes in primary producers over time. 3. Our results showed a significant correlation between MICR and the quantity of mcyE gene and cyanobacterial taxa with known toxin- production potential. The abundance of both genes likewise increased concomitantly through time. 4. Community analyses of HTS data showed significant change in cyanobacte- rial communities commencing c. 1950 when major land-use change in this re- gion led to increased lake productivity, and c. 1990 when Dolichospermum and Microcystis genera increased in abundance, and the subtropical exotic cyanobac- teria Raphidiopsis raciborskii and Sphaerospermopsis aphanizomenoides became abundant. Cyanobacteria pigment data reflected these changes only in deeper lakes, suggesting issues related to benthic production or biomarker preservation in shallower systems.