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
04:00 PM
A TRAIT-BASED DISTURBANCE FRAMEWORK FOR PHYTOPLANKTON PHENOLOGY ACROSS LAKE TROPHIC STATES (7803)
Tutorial/Invited: Invited
Primary Presenter: Ana Morales-Williams, University of Vermont (ana.morales@uvm.edu)
Phytoplankton are sentinels of ecosystem change that respond rapidly to disturbance and in turn influence ecosystem function. As environmental processes in freshwater systems become increasingly stochastic, understanding mechanistic drivers of phytoplankton community assembly is necessary to predict functional diversity and ecosystem feedbacks in response to current and future climate change scenarios. Here we describe a mechanistic, trait-based framework for algal taxa that are resilient to disturbance to predict algal community structure and function in response to stochastic extreme events. We identify three functional axes that confer resilience to disturbance across lake trophic state, including dormancy, morphology, and alternative carbon metabolism (mixotrophy and carbon concentrating mechanisms). We synthesize phytoplankton assemblage data spanning time (multi-annual to multi-decadal) and trophic state (oligotrophic, mesotrophic, dystrophic, eutrophic) to test the hypotheses that (1) the stability of functional traits conferring resilience to extreme events will be inversely related to the frequency of extreme events over time and (2) functional diversity of phytoplankton communities will be greatest at the interface of trophic categories. We then apply this theoretical framework to understand increases in phytoplankton blooms in unexpected conditions, including oligotrophic and cold-water lake ecosystems.
04:15 PM
Better understanding the persistence of HABs on Lake of the Woods through high-frequency monitoring (8246)
Primary Presenter: Adam Heathcote, Science Museum of Minnesota (adam.heathcote@gmail.com)
Lake of the Woods, one of the largest lakes in North America, has been designated as an impaired water due to elevated nutrients and the persistence of harmful algae blooms (HABs) in its shallow southern basin. These blooms continue to occur decades after major reductions in point-source phosphorus pollution and a watershed predominately composed of protected forest. Here, we draw on more than a decade of work on Lake of the Woods using paleo- and neo-limnological techniques that have documented the rise and fall of HABs prior to and following the Clean Water Act, and the recent resurgence of a new, potentially more toxic, community of nitrogen-fixing cyanobacteria in the lake that may be responding to shifts in nutrient stoichiometry and changing patterns in thermal stratification related to climate change. Understanding the trajectory of HABs in Lake of the Woods has required new monitoring techniques, including the deployment of high-frequency sensors and sediment traps, as well as dedicated partnerships between diverse stakeholders, including federal, tribal, and state resource managers. The continued dominance of the southern basin by Cyanobacteria blooms, despite major reductions in phosphorus inputs, demonstrates the complexity of predicting the response of lakes undergoing multiple global stressors and management strategies.
04:30 PM
USING THE THEORY OF ALTERNATE STATES IN ECOSYSTEMS TO PREDICT HARMFUL ALGAL BLOOMS IN THREE OHIO GLACIAL LAKES (8284)
Primary Presenter: Tamar Atwell, Kent State University (tatwell1@kent.edu)
The theory of alternate states of ecosystem predicts that ecosystems can exist in multiple configurations of biotic and abiotic conditions. Perturbations can cause ecosystems to shift from one state to another: in our example, no bloom versus algal bloom. This theory also indicates that statistical properties of state variables will change prior to a change in state (e.g. variance or autocorrelation of the time series). The Quickest Detection (QD) method can be used to detect this change in variance and provide an alarm to indicate that a state change may soon occur. We explored whether the QD method could be applied in three lakes to predict the onset of harmful algal blooms in any of those lakes. The state variables we examined were Chl. a and phycocyanin which were measured daily in East Twin, West Twin and Sandy Lakes (Ohio) from late May to mid-September, 2023. The QD method requires a baseline condition, and we examined each lake’s feasibility to serve as a baseline compared to the other two. East Twin Lake had the lowest concentration and variance of Chl. a and phycocyanin of the three lakes and did not exhibit an algal bloom. West Twin Lake developed two algal blooms and the quickest detection method generated alarms before the peak of each bloom when East Twin Lake was used as a baseline. Sandy Lake had higher concentrations and variance of Chl. a and phycocyanin than either of the Twin Lakes. Sandy Lake had numerous alarms throughout the summer that did not seem to correspond to changes in the algal biomass.
04:45 PM
A 40,000-YEAR PALEOLIMNOLOGICAL RECORD OF BIOGEOCHEMICAL AND AQUATIC COMMUNITY CHANGES FROM SHALLOW LAKE WACCAMAW, NORTH CAROLINA, USA (8123)
Primary Presenter: Savvas Paradeisis-Stathis, Auburn University (szp0156@auburn.edu)
Lake Waccamaw is an aquatic ecosystem known for being the largest inundated Carolina Bay and for having high ecological significance for its endemic and endangered species. The Carolina Bays have been previously studied with paleolimnological tools and have produced sediment records from these ice-free areas spanning well into the last glacial period. Here, we analyzed a sediment core spanning the last 40,000 years to reconstruct cyanobacteria changes in response to multiple periods of climate change. We measured nutrients, photosynthetic pigments, cyanotoxins and stable isotopes. The d13C, C/N and the elemental profile of the sediment core indicate non-limnologic conditions from ~30 to 40ka BP. We observed an early prolonged period of high primary producer abundance with a diverse aquatic community composed of cyanobacteria, diatoms, and algae at ~26ka BP and a second after the Younger Dryas at ~11ka BP. These periods coincided with summer insolation maxima, anoxia inferred from purple-sulfur bacteria proxies, changes in nutrient stoichiometry and cyanotoxin production. A less pronounced period with cyanobacteria dominance occurred at a winter insolation maximum during the last glacial maximum at ~23ka BP. During the middle Holocene, the organic matter content and nutrients in the sediments increased, which sustained the community dynamics but favored colonial cyanobacteria. Our data demonstrate a strong linkage between climate and cyanobacteria, suggesting that insolation maxima and wetter conditions could be triggers for cyanobacteria dominance.
05:00 PM
EARTH, FIRE, AND WATER: USING PALEOLIMNOLOGY TO IDENTIFY DRIVERS OF CYANOBACTERIA ONSET IN SUBTROPICAL AND TROPICAL LAKES PRIOR TO THE ANTHROPOCENE (7901)
Primary Presenter: Matthew Waters, Auburn University (mwaters@auburn.edu)
Cyanobacteria dominance in lake systems can occur in response to the modern impacts from humans and climate. While substantial understanding of harmful algal bloom (HAB) dynamics has been accomplished through modern limnological investigations, historic data are needed to document the drivers and triggers linked to the beginning of cyanobacteria dominance, which frequently precede scientific study. Here, we measured proxies linked to HABs (nutrients, pigments, cyanotoxins) on dated sediment cores from 6 lakes with a focus on the drivers triggering the onset of cyanobacteria dominance. Results show that factors altering biogeochemical processes in lakes were as important as total nutrient concentrations. For Lake Amatitlan, Guatemala and Lake Santa Julia, Mexico, erosional dynamics from ancient societies were the drivers of nutrient inputs and cyanobacteria onset, which also showed rapid recovery once human populations decreased. However, for Ditch Pond Alabama, fire was the trigger causing excessive P inputs and HAB formation called “pyroeutrophication”. Finally, for Lakes Apopka and Harris, Florida and Lake Mattamuskeet, NC, USA, alterations to hydrology was the primary trigger beginning cyanobacteria dominance. For each system, cyanobacteria onset was linked to environmental change with most systems providing unique and novel scenarios. Given that each of these systems represent “pristine” conditions prior to HAB formation and human impacts, these data show that HAB onset can be linked to specific environmental perturbations still occurring in the modern era.
05:15 PM
SEDIMENTARY DNA AND PIGMENT RECORDS FROM TWO LAKES IN WASHINGTON STATE PARKS (8287)
Primary Presenter: William Hobbs, Washington State Department of Ecology (whob461@ecy.wa.gov)
Washington State, USA has had an opportunistic monitoring program for lake cyanotoxins since 2007. Two lakes, situated in state parks within the Puget Sound Region, have annual cyanobacteria blooms that cause the closure of public access to these lakes. Toxin concentrations in both lakes have been sufficient to cause wildlife and pet deaths. The hydrology of both lakes is dominated by groundwater inputs and both lakes have experienced some human impacts during the establishment of the parks. Here, we present sediment core records describing the algal pigment remains over the last ~150 years. In both lakes, carotenoids indicative of cyanobacteria were present throughout the sediment record, demonstrating that the natural geomorphic setting predisposes limnological conditions that support cyanobacteria. However, DNA analyses of the sediment record (qPCR and shotgun metagenome) revealed that the producers of the harmful levels of toxins currently in the lakes may be a more recent phenomenon. Possible climatic and fisheries management strategies are explored.
SS40B - Expect the Unexpected: Why Are Algae Blooms Increasing in Our Most “Pristine” Aquatic Ecosystems?
Description
Time: 4:00 PM
Date: 5/6/2024
Room: Hall of Ideas F