SFS Annual Meeting

5/21/2018  |   09:00 - 09:15   |  420 B

BRIDGING THE GAP BETWEEN LAND MANAGEMENT AND LAKE RECOVERY A process-based model chain was used to quantify effectiveness of terrestrial nutrient control measures in controlling lake eutrophication and restoring lake DO concentrations in Lake Simcoe; the largest lake in Southern Ontario outside of the Great Lakes. Hydrochemical outputs from catchment models INCA-N and INCA-P drove the lake model PROTECH, which simulated water quality in the lake. Water quality responses to nutrient load reductions varied between deep and shallow lake basins. Reductions in terrestrial nutrient exports increased lake DO concentrations, however strategies which reduced tributary flow had a greater impact on lake recovery, associated with changes in water temperature and chemistry. When multiple strategies were implemented simultaneously, large flow reductions induced warming throughout the water column. Negative impacts of lake warming overwhelmed the positive effects of nutrient reduction on DO, and limited the effectiveness of restoration strategies. Lake recovery rates may be accelerated in Simcoe through coordinating management approaches, considering interactions between strategies, and the potential for physical and biological feedbacks associated with changes in lake temperature. Sensitivity of recovery rates to tributary flow and temperature has implications for management resilience under a changing climate.

Jill Crossman (Primary Presenter/Author), University of Windsor, jill.crossman@uwindsor.ca;


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5/21/2018  |   09:15 - 09:30   |  420 B

MICROCYSTINS AND SAXITOXINS IN THE WESTERN AND CENTRAL BASINS OF LAKE ERIE Western basin (WB) microcystin-producing Microcystis blooms have been well-studied for the past decade. Several years of field data have indicated that the ratio of microcystin concentration-to-Microcystis biomass declines throughout summer as nitrate concentration declines. Laboratory experiments with natural WB Microcystis have shown that increased concentrations of nitrate, ammonium, and urea increase microcystins, bloom biomass, up-regulates microcystin synthetase genes. The field and experimental data indicate that nitrogen has an essential role in constraining WB bloom toxicity. In contrast to microcystins, there is less known about saxitoxins in Lake Erie. Satellites have detected cyanobacterial blooms in the offshore waters of the central basin (CB) in several recent years. Field samples from the CB have determined that the dominant cyanobacterium was Dolichospermum – a known saxitoxin producer. A saxitoxin gene (sxtA) was present in 67% of samples collected during Julys of 2016 and 2017; however, the sxtA was not detected in August when Dolichospermum was not present. Additionally, saxitoxins were present at low concentrations (< 0.03 ppb) in surface samples collected in July 2017. In conclusion, researchers are building forecasts for microcystins, whereas saxitoxins are an emerging concern.

Timothy W. Davis (Co-Presenter/Co-Author), Bowling Green State University, timdavi@bgsu.edu;


Derek Smith (Co-Presenter/Co-Author), University of Michigan, smitdere@umich.edu;


Gregory Dick (Co-Presenter/Co-Author), University of Michigan, gdick@umich.edu;


Mikayla Baer (Co-Presenter/Co-Author), University of Michigan, mikbaer@umich.edu;


Sachi Mishra (Co-Presenter/Co-Author), National Centers for Coastal Ocean Science, sachi.mishra@noaa.gov;


Justin Chaffin (Primary Presenter/Author), Ohio State University, Stone Laboratory and Ohio Sea Grant, chaffin.46@osu.edu;


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5/21/2018  |   09:30 - 09:45   |  420 B

RESPONSES OF LAKE ERIE PHYTOPLANKTON COMMUNITIES TO PHOSPHORUS, NITROGEN, AND SILICA LOADING FROM THE MAUMEE RIVER Phytoplankton dynamics in the Western Basin of Lake Erie are strongly associated with phosphorus (P) loading. Yet, we have a limited understanding of how climate and nutrient loading interact to shape intra-annual phytoplankton dynamics, particularly for non-cyanobacteria taxa. Here, we present analyses of a 20-year phytoplankton biomass time series (1995-2015) from a site in the Western Basin of Lake Erie. We asked how P, nitrogen, and silica loading from the Maumee River shapes inter- and intra-annual phytoplankton community dynamics. Multivariate ordination separated phytoplankton communities into two axes: one associated with the relative biomass of cyanobacteria and another associated with diatoms and Cryptophytes. Cyanobacterial biomass, which increased between 1995 and 2015, exhibited strong seasonality and was positively related to the ratios of bioreactive P to total P and nitrate to bioreactive P. The relationship among cyanobacterial biomass, day of year, and nutrient loading changed between the first and second decade of this time series, indicating the potential for a regime shift. Our results suggest that the influence of nutrient loading on phytoplankton community dynamics is complex, temporally variable, and dependent upon the stoichiometry of multiple chemical species.

Lienne Sethna (Co-Presenter/Co-Author), St. Croix Watershed Research Station, lsethna@smm.org;


Todd V. Royer (Co-Presenter/Co-Author), Indiana University Bloomington, troyer@iu.edu;


James Hood (Primary Presenter/Author), The Ohio State University, hood.211@osu.edu;


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5/21/2018  |   09:45 - 10:00   |  420 B

WESTERN LAKE ERIE WATER COLUMN AMMONIUM: INTERNAL CYCLING, SEASONAL DYNAMICS, AND HARMFUL CYANOBACTERIAL BLOOMS Cyanobacterial harmful algal blooms (HABs) in western Lake Erie are largely driven by agricultural nitrogen (N) and phosphorus from the Maumee River watershed. Cyanobacterial dominance and HAB development may be co-dependent on ammonium availability, and increased ammonium has been linked to toxin production. In 2015, 2016, and 2017, 15N tracers were used to quantify rates of ammonium regeneration and potential uptake, ammonia oxidation to nitrite (the first step of nitrification), and total nitrification along a transect in the western basin of Lake Erie. Ammonia oxidation and total nitrification rates were comparable to coastal ocean rates. However, nitrification rates were several orders of magnitude lower than total community ammonium uptake rates, indicating that ammonia oxidation and nitrification are not the dominant uptake pathways. During non-bloom months, regeneration rates could account for an average of 80% of potential community uptake, but during the height of the bloom, when community ammonium demand was much greater, regeneration could only support 40% of potential uptake. These results suggest that management of external total N loads, which are readily converted to ammonium, may be necessary to reduce bloom biomass and toxin concentration.

Mark McCarthy (Co-Presenter/Co-Author), Wright State University, mjm.kingston@gmail.com;


Timothy W. Davis (Co-Presenter/Co-Author), Bowling Green State University, timdavi@bgsu.edu;


Duane Gossiaux (Co-Presenter/Co-Author), NOAA Great Lakes Environmental Research Laboratory, duane.gossiaux@noaa.gov;


Ashley Burtner (Co-Presenter/Co-Author), Cooperative Institute for Great Lakes Research, aburtner@umich.edu;


Tom Johengen (Co-Presenter/Co-Author), Cooperative Institute for Great Lakes Research, tom.johengen@noaa.gov;


Danna Palladino (Co-Presenter/Co-Author), Cooperative Institute for Great Lakes Research, danna.palladino@noaa.gov;


Wayne S. Gardner (Co-Presenter/Co-Author), The University of Texas Marine Science Institute, wayne.gardner@utexas.edu;


Justin A. Myers (Co-Presenter/Co-Author), Wright State University, justin.meyers@wright.edu;


Silvia E. Newell (Co-Presenter/Co-Author), Wright State University, silvia.newell@wright.edu;


Daniel K. Hoffman (Primary Presenter/Author), Wright State University, dprhoffman@gmail.com;


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5/21/2018  |   10:00 - 10:15   |  420 B

AMMONIUM REGENERATION DRIVES SUMMER BLOOMS OF PLANKTOTHRIX IN SANDUSKY BAY Sandusky Bay (SB; Lake Erie) receives high nutrient loads (N and P) from an agricultural watershed. Eutrophication and cyanobacterial blooms (cyanoHABs) persist throughout summer in SB, dominated by Planktothrix agardhii, also the main producer of microcystin in SB. Non-N2 fixing cyanobacteria (e.g., Microcystis and Planktothrix), thrive on chemically reduced N forms (e.g., NH4+ and urea). Monitoring NH4+ turnover rates improves our understanding of cyanoHABs and NH4+ contributions to sustaining blooms. We quantified NH4+ regeneration and potential uptake using 15N isotopes in SB throughout the summer bloom and compared NH4+ uptake kinetics during a Planktothrix bloom in SB and a Microcystis bloom in Maumee Bay. NH4+ uptake rates in SB increased with bloom progression from June to August, with dark rates achieving parity with light rates in August. Regeneration rates were also significantly higher in August than June. Half-saturation constants (Km) in SB decreased throughout the bloom but increased in Maumee Bay, suggesting differing competitive dynamics. In late summer, N concentrations are low, and cyanoHABs rely on regenerated NH4+ for biomass and toxin production. We also hypothesize a community shift and increasing heterotrophic contribution to NH4+ uptake in the phycosphere.

Justyna J. Hampel (Primary Presenter/Author), Wright State University, hampel.4@wright.edu;


Mark J. McCarthy (Co-Presenter/Co-Author), Wright State University, mark.mccarthy@wright.edu;


George S. Bullerjahn (Co-Presenter/Co-Author), Bowling Green State University, bullerj@bgsu.edu;


Robert M. McKay (Co-Presenter/Co-Author), Bowling Green State University, rmmckay@bgsu.edu;


Michelle Neudeck (Co-Presenter/Co-Author), Bowling Green State University, mneudec@bgsu.edu;


Katelyn McKindles (Co-Presenter/Co-Author), Bowling Green State University, kmckind@bgsu.edu;


Silvia E. Newell (Co-Presenter/Co-Author), Wright State University, silvia.newell@wright.edu;


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5/21/2018  |   10:15 - 10:30   |  420 B

NUTRIENT AND TRACE METAL CO-LIMITATION OF ALGAL BLOOMS IN THE GREAT LAKES Efforts to reduce the frequency and extent of harmful algal blooms (HABs) require knowledge about factors that control algal growth and toxin production. While labile N and P fuel primary production, micronutrients (Fe, Zn, Ni, Mo) form the enzymatic engines that promote rapid and efficient growth and toxin production. In summer 2017, we completed in-situ nutrient enrichment experiments with both single and combinations of elements using diffusing substrates. Enrichment experiments were replicated at 10 locations near rivermouths in Lakes Michigan and Erie that encompassed sites with little algal biomass and those with active HABs. Preliminary analysis suggests significant inter-site variation in nutrient limitation of biomass; no nutrient limitation was most common (6 sites), and biomass at both active bloom and oligotrophic sites was not nutrient limited. Co-limitation of N and P (2 of 10 sites) and co-limitation with trace metals (2 of 10 sites) were equally common. Preliminary data suggest that microcystin concentrations in algae are decoupled from biomass response to enrichment. These data demonstrate that a multi-nutrient view of elemental requirements is needed to understand the drivers of HABs in the Great Lakes.

David Costello (Primary Presenter/Author), Kent State University, dcostel3@kent.edu;


Jordyn Stoll (Co-Presenter/Co-Author), Kent State University, jstoll7@kent.edu;


Andrea Fitzgibbon (Co-Presenter/Co-Author), Kent State University , afitzgib@kent.edu;


James Larson (Co-Presenter/Co-Author), U.S. Geological Survey, jhlarson@usgs.gov;


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