Algae blooms are increasingly reported in unexpected places, including remote and protected aquatic ecosystems. This session asks “What is behind these blooms and how can we better predict them in the future?” Emerging research has suggested a suite of potential drivers for these blooms, including climate change, atmospheric nutrient deposition, alkalization of soils, and the introduction of aquatic invasive species. Because the timing of these human-caused disturbances covary over the last half-century, disentangling the relative effects requires careful consideration. We welcome a wide variety of submissions, including event-based monitoring, experimentation, paleolimnology, and computational modelling, that discuss these or other drivers and help us better understand how they may be working independently or in concert to produce previously unexpected results.
Lead Organizer: Adam Heathcote, Science Museum of Minnesota (adam.heathcote@gmail.com)
Co-organizers:
Lienne Sethna, Science Museum of Minnesota (lsethna@smm.org)
Janice Brahney, Utah State University (janice.brahney@usu.edu)
Chris Filstrup, University of Minnesota Duluth (filstrup@d.umn.edu)
Presentations
02:00 PM
CYANOBACTERIAL SURPRISES: EXPLORING UNEXPECTED BLOOMS AND UNRAVELING THEIR CAUSES (7761)
Tutorial/Invited: Invited
Primary Presenter: Kaitlin Reinl, University of Wisconsin - Madison (kreinl@wisc.edu)
The current paradigm for drivers of cyanobacterial blooms is that high nutrients and high temperatures cause blooms. However, there is growing evidence that blooms are occurring under a wide range of environmental conditions, even in cold and low nutrient systems. In this talk, I will offer explanations for why we observe blooms under conditions that do not align with the current paradigm, including biological adaptions and abiotic conditions that support these unexpected blooms. The objective of this talk is not to suggest that high nutrient and temperature conditions do not drive blooms, but to encourage consideration of mechanisms that can support blooms outside of these often-observed conditions so that we may improve our collective understanding of bloom ecology and equip resource managers with knowledge and tools mitigate blooms in unexpected places and protect public health.
02:15 PM
THERMAL STRUCTURE AND OXYGEN DEPLETION PROVIDE MECHANISM FOR CYANOHABS IN LOW NUTRIENT LAKES: CHALLENGING THE EUTROPHICATION-HAB PARADIGM (8109)
Primary Presenter: Lienne Sethna, St. Croix Watershed Research Station (lsethna@smm.org)
The management of harmful blooms of cyanobacteria (cyanoHABs) has historically relied on watershed nutrient reduction strategies; however, cyanoHABs have been increasingly reported in remote and oligotrophic lakes whose catchments are relatively protected from human landscape modifications. This has prompted a paradigm shift in our understanding of the drivers of cyanoHABs and a need to study environmental factors beyond watershed nutrient inputs. In this study, we examined eight lakes within the Superior National Forest (Minnesota, USA). We paired high-resolution temperature and dissolved oxygen profiles with monthly measurements of nutrients, algal density, and cyanobacteria community composition to assess the relationship between thermal structure, oxygen depletion rates, and algae, including cyanobacteria. We found that cyanobacteria abundance was correlated to total phosphorus (P) concentrations, which in turn were related to how frequently the lakes experienced “anoximixis”. Anoximixis, which we define as lake turnover with anoxic bottom waters, facilitates the mixing of anaerobically released sediment P to the water column. Taken together, these results suggest that even in our most protected regions, shallow lakes experiencing polymictic thermal regimes may support cyanoHABs through increased internal P loading. As stratification regimes continue to be altered under warmer climate scenarios, improving our understanding of the linkages between cyanoHABs and internal P loading in these remote lakes will allow us to better focus management efforts in the future.
02:30 PM
Harmful algal blooms in high-elevation Western United States lakes (8263)
Primary Presenter: Sarah Collins, University of Wyoming (sarahmcollins@gmail.com)
Nutrient pollution and climate change can lead to eutrophication and harmful algal blooms (HABs) in lakes. While most research on eutrophication has been conducted in human-dominated watersheds, HABs have recently been reported in relatively undisturbed lakes in the Intermountain Western United States. In Wyoming, the number of HAB advisories has steadily increased from 3 water bodies in 2017 to >40 water bodies in 2023. Many blooms occur in remote lakes with forested watersheds, suggesting that controls on bloom formation may be different than in other regions where most studies have occurred. The increase in HAB advisories also contradicts recent remote-sensing based research suggesting that eutrophication is not widespread in the region. We investigated these trends and contradictions in water bodies in Wyoming through analysis of monthly monitoring data collected by our research group and by the State of Wyoming, and through high-frequency monitoring data generated from buoys equipped water quality sensors. Overall, data suggest that nutrient limitation may differ from other regions, with very low N:P ratios in some lakes that are susceptible to blooms. Productivity and algal biomass were variable across the surface of lakes, suggesting that spatial heterogeneity in primary production within individual lakes could explain the discrepancy between increasing HAB advisories and the lack of eutrophication trends from remote sensing data. Continued long-term lake monitoring in this region could elucidate key connections between climate change, lake water quality, and HABs.
02:45 PM
QUANTIFICATION OF MICROCYSTINS AND OLIGOPEPTIDES IN AN ACIDIC TANNIN – STAINED LAKE EXPANDS THE ECOLOGICAL RANGE OF CYANOBACTERIAL HARMFUL ALGAL BLOOMS (8321)
Primary Presenter: Todd Miller, University of Wisconsin - Milwaukee (trexmiller@gmail.com)
Cyanobacterial harmful algal blooms (cyanoHABs) are a growing problem in aquatic environments. Tannins and specifically polyphenols have been shown to inhibit the growth of cyanoHAB species in laboratory cultures and have been used as an in-lake mitigation tool. Here we describe unusual toxic cyanoHABs caused by Microcystis and Dolichospermum species in a tannin - stained acidic lake in the northern highlands of Wisconsin, USA. CyanoHAB events were observed concomitantly with reductions in thermal stability and entrainment of soluble reactive phosphorus into surface waters during the open water season. The cyanotoxins microcystins (MC), anabaenopeptins (AP), cyanopeptolins (CP) and microginin-690 were measured by liquid chromatography tandem mass spectrometry. MCs occurred in all but two samples at an average concentration of 26.8 µg/L at the deep hole whereas nearshore scum samples contained a maximum of nearly 4000 µg/L with greater congener diversity. The MC congener MC-LA was most abundant followed by MC-LR > MC-LY > MC-LF > [Dha7]MC-LR. AP’s were detected at an average of 4.0 +/- 17.2 µg/L at the deep hole and exceeded 800 µg/L in nearshore scum samples. CP’s and microginin-690 were detected in several nearshore locations, although at lower concentrations. Total polyphenols averaged 12.54 +/- 0.56 mg/L gallic acid equivalents, which is higher than concentrations previously shown to inhibit the growth of Microcystis and Dolichospermum. These results extend the ecological range of lake habitats supporting highly toxic cyanoHABs.
03:00 PM
UHF: USING ULTRA-HIGH FREQUENCY SENSOR DATA PROVIDES A LEADING INDICATOR OF HARMFUL ALGAL BLOOMS IN AN OLIGOTROPHIC LAKE (7802)
Primary Presenter: Vincent Moriarty, Rensselaer Polytechnic Institute/ IBM Research (vincent.w.moriarty@ibm.com)
Harmful algal blooms (HABs) threaten the quality of many water bodies, even oligotrophic lakes once thought to be immune from algal blooms. Episodic HABs are best characterized as aggregations of cyanobacteria at the water surface and represent a rapid concentration of deep-water colonies previously dispersed throughout the water column. Predicting the onset and duration of HABs has proven challenging, as the dynamic nature of these events can be difficult to characterize using traditional high-frequency sensor technology. While dense surface aggregations may be easier to identify using traditional sensor methods, the same algal colonies can be much more difficult to detect when dispersed throughout the mid-water column. This is especially true in oligotrophic lakes where phytoplankton biomass is low to begin with. While monitoring mid-column phytoplankton can be challenging in oligotrophic lakes, identifying the sometimes-subtle dynamics of deep water cyanobacteria assemblages is essential to further understanding the development of HABs, and may provide a useful leading indicator of surface HABs. Here, we use advanced vertical profiling sensor platforms deployed in an oligotrophic lake (Lake George, NY, USA) to study HAB dynamics. Our results show that a novel use of ultra-high frequency (<1 second) data can be used to detect mid-column cyanobacterial dynamics that precede surface HABs. These approaches enable the possibility of characterizing mid-column cyanobacterial development and provide important insight for both ultimate and proximal drivers of surface HABs.
03:15 PM
ROLE OF TRIBUTARY NUTRIENT TRANSPORT AND SEDIMENT PHOSPHORUS PROCESSES ON NUTRIENT DYNAMICS IN NEARSHORE LAKE SUPERIOR (7737)
Primary Presenter: Rebecca Kreiling, UMESC - Laboratory/Office - #1 (rkreiling@usgs.gov)
Over the past decade, cyanobacterial blooms have occurred along the southwestern shore of oligotrophic Lake Superior. Previous studies indicate that watershed fluxes of sediment and nutrients, in particular phosphorus (P), may play an important role in driving these blooms. To understand how tributary loads of nutrients and sediment contribute to nearshore blooms, two key tributaries, Bois Brule and Siskiwit Rivers, were sampled in the vicinity of recurring cyanobacterial blooms in the nearshore. We monitored discharge and water quality to compute nutrient and sediment loads and collected suspended and streambed sediment to assess the capacity for the sediment to store and transport bioavailable P in the rivers. Strong positive relations between discharge and concentrations of suspended sediment, total P, and total nitrogen indicated storm flows drove export. A strong positive relation between total P and suspended sediment indicated that sediment may serve as a vector for P. Additionally, evaluation of equilibrium P concentrations revealed that suspended sediment sorbed P as it is moved through the stream network across sites and seasons and was a potential source of P to the nearshore. However, the streambed sediment in both watersheds were P sinks during the summer, which potentially delayed transport of dissolved P to the lake.
SS40A - Expect the Unexpected: Why Are Algae Blooms Increasing in Our Most “Pristine” Aquatic Ecosystems?
Description
Time: 2:00 PM
Date: 5/6/2024
Room: Hall of Ideas F