Thursday, November 14
8:30 am – 10:00 am

Agenda subject to change.
Updated 20 September 2019

★ Denotes that the lead author is a student.

 

H1: Monitoring I – Long Term

Moderator: A.J. Reyes
Northeast Aquatic Research, Putnam Valley, New York

8:35 Evaluating Synergistic Effects of Climate Change and Trophic Dynamics on Thermocline Depth (2000–2018)
Holly Waterfield and Daniel Stich
SUNY College at Oneonta Biological Field Station, Cooperstown, New York

Recent work has highlighted the potential influences of climate change on physical limnology in marine and freshwater systems at multiple scales, and through multiple pathways. However, many of these studies are conducted at the landscape scale to quantify regional or global changes, and often lack the resolution to assess fine-scale changes in physical limnology resulting from localized drivers. Local-scale changes in other biotic and abiotic conditions have the potential to interact with climate change to influence physical properties of lakes and reservoirs, potentially in synergistic ways. We analyzed a contemporary time series of data (2000–2018) from Otsego Lake, New York to investigate relationships between thermocline depression and several local drivers of interest (e.g., season, day of year, Secchi depth). Thermocline depth decreased from 9.1 m (95% CI = 7.2–11.6 m) prior to peak abundance of invasive alewife (Alosa pseudoharengus), to a mean of 6.7 m (5.3–8.5 m) following their eradication, and subsequently increased following expansion of invasive zebra mussels (Dreissena polymorpha) until present day (7.5 m, 95% CI = 5.9–9.6 m). These trends were reflected in a quadratic relationship between year and thermocline depth, as well as through an inverse relationship between alewife abundance and thermocline depth. Additionally, thermocline depth was directly proportional to heating degree days and inversely related to duration of ice cover from 2000 through 2018. Our results suggest that July thermocline depth has been influenced by abiotic and biotic changes in this system through combined effects of climate change and species introductions.

8:55 Increasing Productivity Amid Stable Nutrient Regimes in Rhode Island Lakes and Reservoirs
Jeffrey Hollister1, Dorothy Kellogg2, Betty Kreakie1, Stephen Shivers3, Elizabeth Herron2, Linda Green2, Bryan Milstead1, and Art Gold2
1US Environmental Protection Agency, Narragansett, Rhode Island; 2University of Rhode Island, Kingston, Rhode Island; 3US Environmental Protection Agency/ORISE, Narragansett, Rhode Island

Addressing anthropogenic impacts on aquatic ecosystems is a focus of lake management. Controlling phosphorus and nitrogen can mitigate these impacts but determining management effectiveness requires long-term datasets. Recent analysis of the LAke multi-scaled GeOSpatial and temporal database (LAGOSNE) found stable water quality in the Northeastern and Midwestern United States, however, sub-regional trends may be masked. We analyze a sub-regional trend with the University of Rhode Island’s Watershed Watch Volunteer Monitoring Program (URIWW) dataset. URIWW has collected water quality data on Rhode Island lakes and reservoirs for over 25 years. The LAGOSNE and URIWW datasets allow for comparison of water quality trends at regional and state extents, respectively. We assess regional (LAGOSNE) and state (URIWW) trends with yearly averaged z-scores (i.e., scaled anomalies) calculated on a per-station basis. In Rhode Island, temperature and chlorophyll a increased from 1993 to 2016. Total nitrogen shows a weak increase driven by low years in the early 1990s. Total phosphorus and the nitrogen:phosphorus ratio (N:P) were stable. At the regional scale, the LAGOSNE dataset shows similar trends to prior studies of the LAGOSNE with chlorophyll a, total nitrogen, total phosphorus, and N:P all stable over time. In short, productivity in Rhode Island lakes and reservoirs is increasing, in spite of stable nutrient regimes. Although not causal, this analysis suggests an association between lake temperature and productivity. Additionally, we demonstrate both the value of long-term monitoring programs, like URIWW, for identifying trends in environmental condition, and the utility of site-specific z-scores for analyzing for long-term trends.

9:15 Markermeer: A Tell-Tale Story of the Wax and Wane of Ecological Quality in a Large Dutch Reservoir
Lisette de Senerpont Domis and Sven Teurlincx

Netherlands Institute of Ecology, Wageningen, The Netherlands

Markermeer is a large shallow reservoir (average depth 4m, 700 km2) in the Netherlands resulting from the damming of a large saltwater inlet (1932). It is a Ramsar site and historically provided home to a diverse community of bird and fish species. Over the past decades, Markermeer has undergone numerous restoration and biodiversity conservation measures to counteract the observed decline in Ramsar target species, such as the common tern, and crested ducks. Measures ranged from nutrient abatement programs and most recently, the creation of the Markenwadden wetlands to trap sediment and establish nursing grounds for bird species.

Feeding the ecosystem model Ecopath with long-term monitoring data we investigated the mechanisms behind the decline in target species, as well as simulated the effect of potential restoration measures on foodweb functioning. In my talk, apart from showing the wax and wane of ecological quality of Markermeer, I will guide the audience through the quirks and perks of European nature management legislation and will give examples on the engineering approach the Dutch have towards lake management.

9:35 The Value of Long-Term Watershed Research to Science and Society
Jamie Shanley

US Geological Survey, Montpelier, Vermont

Environmental monitoring provides core information to guide scientific research and formulate policy. Repeated measurement in the same place holds some variables constant to reveal underlying environmental processes and trends. As the record length grows from years into decades, one observes natural variability, trends, and the environmental response to a broad range of forcings. Synthesis of observations from multiple places along climatic and geologic gradients corroborates patterns and trends, while site-specific variations further constrain process interpretation. Experimental catchments using the small watershed approach are cornerstone sites for advancing knowledge on hydrological, biogeochemical, and ecological processes. Long-term institutional support of these sites connects shorter-cycle academic grants, together yielding discoveries that benefit society. I highlight examples from long-term research catchments including the US Geological Survey’s Sleepers River Research Watershed in Vermont.

 

H2: Water Quality

Moderator: Steve Lundt
Metro Wastewater Reclamation District, Denver, Colorado

8:35 Variation in Trophic State Parameters Within the Photic Zone of Reservoirs
John R. Jones, Rebecca L. North, and Daniel V. Obrecht
School of Natural Resources, University of Missouri, Columbia, Missouri

Reservoir water quality is highly variable. Quantifying variation, both spatial and temporal, informs processes, monitoring design, and trophic state classification. We assessed vertical variation in the photic zone, to determine if water quality at Secchi depth routinely differs from near-surface conditions. This dataset includes total nitrogen (TN), total phosphorus (TP), and chlorophyll (Chl) data from 8102 paired samples from 232 Missouri reservoirs. Values span the established trophic gradient, and individual Secchi readings ranged from < 0.1 to 8.6 m (median = 1.0 m). Among the surface-Secchi comparisons, 71% of TN, 66% of TP, and 59% of Chl measurements were within 10%. When differences in TP and Chl were > 10% it was common for Secchi sample to be 5-times larger than at the surface. These deviations (Secchi > Surface) occurred when temperature differed by > 0.5 °C, while TN deviations > 10% generally occurred when differences were > 2.0 °C. Dissimilarity between paired samples were not consistent across the range of water clarity. When Secchi depth was > 4.0 m (n = 299) absolute differences in TN, TP and Chl averaged 59, 4, and 2.5 µg/L, respectively. In contrast, when Secchi transparency was < 0.25 m (n = 241) average absolute differences were larger (TN = 123, TP = 16, and Chl = 7.0 µg/L), even though the samples were collected in close vertical proximity. While most differences were modest, substantial disparities between the collections occurred in about 3% of comparisons. Temporal variation, however, is greater in these systems than spatial variation.

8:55 Lake Photic Zone Temperature Across the Conterminous United States
Stephen D. Shivers1, Betty J. Kreakie2, W. Bryan Milstead2, and Jeffrey W. Hollister2
1ORISE EPA Atlantic Ecology Division, Narragansett, Rhode Island; 2EPA Atlantic Ecology Division, Narragansett, Rhode Island

As global air temperatures increase, lake surface water temperatures also increase. These increases will cause ecosystem changes that will impact all aspects of lake management, particularly related to harmful algal blooms (HABs). Increasing surface water temperatures can cause an increase in the frequency, duration, and severity (i.e., toxicity) of HABs, which affect both human and environmental health. Our ability to predict and manage HABs is dependent on our ability to accurately predict temperature; thus, the goal of this project was to develop a simple, robust photic zone temperature model for all lakes in the conterminous United States. Data from the 2007 and 2012 US EPA National Lake Assessment was used for model development. Random forest, a machine learning approach based on an aggregation of 10,000 regression trees, was used to develop our final predictive model. The final model had a mean square error of 2.17 °C and adjusted R2 of 0.89. Sample date, average daily ambient air temperature, longitude, and the 30-day average ambient air temperature were the most important variables to overall model accuracy. We are currently backcasting temperature over the past thirty years for all lakes in the NHDPlus database to look for trends at regional and continental scales.

9:15 Horizontal Variability in Oligotrophic Lake Metabolism to Prioritize Watershed Locations for Nutrient Runoff Reduction
Nicole K. Ward1, Jennifer A. Brentrup2, David C. Richardson3, Kathleen C. Weathers4, and Cayelan C. Carey1
1Department of Biological Sciences, Virginia Tech, Blacksburg, Virginia; 2Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire; 3Biology Department, SUNY New Paltz, New Paltz, New York; 4Cary Institute of Ecosystem Studies, Millbrook, New York

Robust water quality indicators are needed to inform oligotrophic lake management. Lake metabolism, the balance of carbon production and respiration, is an integrated ecosystem metric, however, little is known about the relationship between lake metabolism estimates at near-shore sites and nutrient loading from the nearest inflow tributary (hereafter ‘localized nutrient loading’). In this study, we asked: How do summer lake metabolism estimates at three near-shore sites (4–7 m deep) compare to a single deep site (13 m deep) estimate? We addressed this question in oligotrophic Lake Sunapee, New Hampshire (USA), a lake with 12 inflow streams that vary three-fold in their nutrient load to the lake. We used high-frequency measurements of dissolved oxygen, water temperature, and light to estimate metabolism at each site and measured stream discharge and nutrient concentrations in the closest inflow streams to estimate localized nutrient loading.

All sites averaged near-zero net ecosystem production (range = -0.36 – 1.45 mg-O2/L/day). The magnitude of variability in diel dissolved oxygen concentrations was greater at the near-shore sites (~0.5 mg-O2/L/day) than at the deep site (~0.15 mg-O2/L/day). The highest localized nutrient loading and maximum gross primary production (2.8 mg-O2/L/day) and respiration rates (2.6 mg-O2/L/day) occurred at the same site. Our work suggests that near-shore metabolism can be used as an indicator of ecosystem trophic state change due to localized nutrient loading. Developing a relationship between more easily measured ecosystem metabolism metrics compared to time-intensive nutrient sampling may help managers target high-priority areas of the watershed for lake nutrient load reductions.

9:35 A Preview of Results From the 2017 US National Lakes Assessment
Amina Pollard

Office of Water, US Environmental Protection Agency, Washington, District of Columbia

The National Lakes Assessment (NLA) is a partnership project led by US Environmental Protection Agency, state agencies, and Tribal Nations to assess the condition of freshwater lakes and ponds in the conterminous United States. This assessment is intended to provide a snapshot of national and regional estimates of the biological, chemical, physical and human use conditions of lakes. Consistent sampling and analytical methods ensure that results can be compared across the country. Owing to the statistical design, results from this assessment are presented in terms of national and regional-scale populations. I will share a preview of assessment results from the 2017 NLA and discuss the anticipated report package. I will highlight condition results for water column nutrients, algal toxins (microcystin and cylindrospermopsin), and trophic state. I will highlight changes lake conditions among the 2007, 2012, and 2017 assessments. For example, preliminary exploration indicates that a lower proportion of lakes sampled had microcystin concentrations above the WHO benchmarks in 2017 compared to the 2012 assessment. In addition to discussing the condition estimates, I will present results of an analysis that ranks stressors based on their relative associations between indicators of condition and indicators of stress. Finally, I will show the updated NLA context tool, which harnesses this broad data set and facilitates connection to local knowledge about lakes.

 

H3: Harmful Algal Blooms V

Moderator: Michelle Balmer
Iowa Department of Natural Resources, Des Moines, Iowa

8:35 ★ Going Beneath the Surface: The Ecology of Metalimnetic Cyanobacteria Layers in Three New Hampshire Lakes
Sabina Perkins1 and Jeff Schloss
2
1University of New Hampshire, Durham, New Hampshire; 2University of New Hampshire Cooperative Extension, Durham, New Hampshire

Cyanobacteria blooms take different forms: surface scums, subsurface epilimnetic blooms, mats on the lake bottom, and in some lakes, metalimnetic layers. These layers have the potential to produce cyanobacterial toxins and understanding the ecology of these layers is important from a management, monitoring and public health perspective. Current field research on the seasonal behavior of these layers and the contribution of layer-produced cyanotoxins to the overall toxin profile of lakes, where layers exist, is limited. We monitored three lakes in New Hampshire monthly in 2018 tracking the formation and persistence of deep-water cyanobacteria layers in each and the physical/chemical/light environments where they were found. Cyanobacteria biomass and dominance were quantified through cell counts using an Imaging Flow Cytobot (IFCB) and with phycocyanin fluorescence estimates We also analyzed the levels of microcystin toxin in both the surface and cyanobacteria layer in these lakes. Very low levels of microcystin were found in all three of the lakes despite the presence of dense accumulations of cyanobacteria in the metalimnion. Microcystin levels appear to be more related to toxin producing species of cyanobacteria other than the Planktothrix isothrix found dominating the layer samples in all the lakes monitored. This raises the possibility that the dominant strain found in all three of the lake metalimnions may not produce microcystin or did not experience conditions in the 2018 growing season that favored the production of microcystin. Potential ecological explanations for this non-microcystin-producing layer phenomenon will be discussed.

8:55 Potential for Cyanotoxin Occurrence in the Nation’s Large Rivers
Jennifer L. Graham1, Neil M. Dubrovsky2, Guy M. Foster1, Lindsey R. King3, Keith A. Loftin3, Barry H. Rosen4, and Erin A. Stelzer5
1US Geological Survey, Troy, New York; 2US Geological Survey, Sacramento, California; 3US Geological Survey, Lawrence, Kansas; 4US Geological Survey, Orlando, Florida; 5US Geological Survey, Columbus, Ohio

Cyanobacterial blooms are increasingly a global concern because of threats posed to human, ecosystem, and economic health. Toxins produced by some species of cyanobacteria (cyanotoxins) can cause acute and chronic illnesses in humans. Recent national and regional assessments have shown that cyanotoxins are commonly detected in the Nation’s lakes, reservoirs, small streams, and wetlands. However, studies conducted on large rivers have been in response to cyanobacterial events, and there has not been an assessment of cyanotoxin occurrence in the Nation’s large rivers. A pilot study to assess potential cyanotoxin occurrence at eleven large river sites in the US Geological Survey National Water Quality Network was conducted during summer 2017. About 48 unique cyanobacterial taxa were identified from the 11 sites over a three-month period, including one that has not previously been identified in the US (Uzmekia, pending verification). In addition, live samples were re-checked monthly for 3 months to ensure organisms below the detection limits of the traditional counting approach were identified. Cyanobacteria occurred at all 11 study sites, but only dominated phytoplankton community composition at one study site. Cyanobacterial abundance and overall algal biomass (as indicated by chlorophyll) were highest in rivers located in the central US. Microcystin was the only cyanotoxin (anatoxin, cylindrospermopsin, and saxitoxin also were measured) detected during summer 2017. Microcystin was detected at low concentrations (less than 0.5 micrograms per liter) in two central US rivers. By comparison, the genetic potential for cyanotoxin production (anatoxin, cylidrospermopsin, microcystin, and/or saxitoxin) was detected at all study sites except one (in the northeastern US). Genetic potential varied by site and with time, and generally reflected cyanobacterial community composition. Combined, these data contribute to our understanding of the potential for cyanotoxin occurrence in a small subset of the Nation’s large rivers. Including multiple approaches in ongoing data collection efforts will help identify the best tools for future studies to assess occurrence throughout the Nation, leading to better information for early warning, management, and mitigation strategies.

9:15 Microcystin Accumulation in Recreational Beach Sediments and Porewater
Ellen Preece1, William Hobbes2, Joan Hardy3, and Lenford O’Garro4
1Robertson Bryan Inc. Elk Grove, California; 2Washington Department of Ecology, Seattle, Washington; 3Emeritus Washington Department of Health, Olympia, Washington; 4Washington Department of Health, Olympia, Washington

Many Washington State lakes experience cyanobacteria blooms that necessitate advisories about cyanotoxin presence such as the liver toxin microcystin (MC). Although littoral surface waters may contain MC concentrations that pose potential public health risks, little is known about MC contamination of nearshore sediments. Based on growing evidence showing lake sediments can accumulate MCs, we hypothesized nearshore sediments (i.e., recreational beaches) may also accumulate MCs and thereby pose a potential health risk to recreational users even if people stay out of contaminated water. We sampled sediments, porewaters, and nearshore surface waters from recreational beaches from seven Washington lakes and reservoirs for MCs during or immediately following cyanobacteria blooms. We found MCs in recreational beach sediments at all seven lakes and reservoirs. Even after surface waters tested near analytical reporting limits MC concentrations in sediments and pore waters remained high, exceeding surface water concentrations, for the next 20 days. For the first time we demonstrate beaches where people recreate accumulate MCs from nearshore surface waters. However, a human health assessment, based on MC exposure through incidental ingestion of beach porewaters and sediments, indicates even when high MC concentrations occur in surface waters (i.e., >11,000 µg/L) estimated ingestion doses for children and adults were below the WHO Tolerable Daily Intake and the USEPA’s Reference Dose. While our findings suggest Washington recreational beaches in 2018 did not present a significant MC exposure pathway to humans, if higher MCs concentrations accumulate in beach sediments then there may be future human health risks.

9:35 New York State Harmful Algal Bloom Initiative: An Initial Summary of Mitigation Pilot Outcomes
Stephanie June

New York State Department of Environmental Conservation, Albany, New York

In 2018, New York State (NYS) Governor Cuomo announced a four-point initiative to address harmful algal blooms (HABs) in Upstate New York. As part of Governor Cuomo’s 2018 HABs Initiative, innovative mitigation pilot projects were initiated to evaluate strategies that prevent or lessen the impact of HABs. The NYS Department of Environmental Conservation (DEC) began the pilots in the summer of 2018 on waterbodies representative of a range of waters commonly associated with HABs in NYS. Waterbodies were selected due to their history of HABs, elevated nutrients, relatively small size, and supported recreational uses. The pilot strategies implemented included application of an algaecide, hydrogen peroxide, and installation of an ultrasonic device, both with little in-state application history. In addition, nutrient inactivation was utilized in two waterbodies to evaluate efficacy of binding excess phosphorus in bottom sediments. A summary will be presented of field reports, water quality data, and biological data from sampling events preceding, during, and following the in-lake treatments. Hydrogen peroxide was found to be most effective where phytoplankton diversity was greatest and species richness significantly increased over the course of treatment (p = 0.0019 and p = 0.037; respectively), and where the zooplankton community was dominated by rotifers (p = 0.001). The ultrasonic device had no significant impact. The first of two years of post-nutrient inactivant treatment monitoring will be assessed for detectable changes in bioavailable nutrients and potential negative biological impacts. Project outcomes will help provide recommendations for future work needed to continue assessing innovative treatments to reduce the occurrence of HABs.

 

H4: Oxygenation II

Moderator: Chris Holdren
Environmental Consultant, Littleton, Colorado

8:35 Changes to the Culver Lake Aeration System: Why, How and Results
Stephen J. Souza1, Christopher Mikolajczyk2, and Evan Kwityn2
1Clean Waters Consulting, LLC, Ringoes, New Jersey; 2Princeton Hydro, LLC, Ringoes, New Jersey

Culver Lake is a 500-acre, 65 ft deep kettle-hole lake located in Sussex County, New Jersey. This presentation reviews and discusses the statistical findings of Culver Lake’s long-term water quality dataset; 1989 through 2018, focusing on the lake’s thermal, dissolved oxygen, nutrient and cyanobacteria data. Through the management efforts of the Normanoch Association the lake’s water quality has substantially improved over the past three decades, with the primary reason for these improvements being the lake’s aeration system. The hybrid conventional hypolimnetic aeration and destratification system, maintains the lake in multiple thermal layers, consisting of a segregated, deep cold-water layer and warmer, intermediate and shallow water depth layers. Proper operation of the system limits internal phosphorus loading and controls cyanobacteria blooms.

However, although it remains the “corner stone” element of the lake’s management, data show that over the past 6–8 years the existing configuration and operation of the aeration system needed to be modified in order to increase system efficiency and effectiveness. Most importantly, the data show that at times the creation and maintenance of the intermediate thermal layers exacerbate the upwelling of phosphorus rich water into the epilimnion, resulting in mid-to late-summer and early fall cyanobacteria blooms. This presentation details the data pertaining to system performance and benefits, discusses the recent data-driven changes made to the design and operation of the system, and presents the initial findings that these changes had on the lake’s water quality.

8:55 Hypolimnetic Oxygenation and Aeration in Two Midwestern USA Reservoirs
David Austin1, Roger Scharf1, Che-Fei Chen2, and Jim Bode2
1Jacobs Engineering Group, Saint Paul, Minnesota; 2Saint Paul Regional Water Services, Saint Paul, Minnesota

This study (published LRM 2019) compares performance of hypolimnetic aeration (HA) with hypolimnetic oxygenation (HO) from 1988 to 2018, over multiple project phases and a baseline period 1984 to 1986. Saint Paul Regional Water Services, Minnesota, pumps 170 MLD (45 MGD) from the Mississippi River through a chain of 4 lakes before treatment. Two, Pleasant Lake and Vadnais Lake, were equipped with partial-lift HA later replaced by linear diffuser HO. Ferric chloride was injected into inflows and into Vadnais at the HA or HO system. HA failed to relieve hypolimnetic hypoxia in Pleasant (median DO 1.7 mg/L) or Vadnais (median DO 2.7 mg/L). Median HO values were aerobic (Pleasant 4.2 mg/L, Vadnais 8.5 mg/L). Both HA and HO raised hypolimnetic oxidation reduction potential to high positive values from negative values associated with Mn and Fe solubilization. Compared to HA, HO reduced median hypolimnetic total Mn concentrations by 75% in Pleasant and in 93% in Vadnais, and hypolimnetic total Fe by 84% in Pleasant and 81% in Vadnais. HA significantly lowered median hypolimnetic TP from baseline, 0.552 mg/L to 0.146 mg/L in Pleasant, and 0.533 mg/L to 0.045 mg/L in Vadnais. HO median hypolimnetic TP was significantly lower at 0.053 mg/L in Pleasant, 0.030 mg/L in Vadnais. Superior performance of HO occurred at similar oxygen delivery rates: 1775 kg/d in Pleasant and 970 kg/d in Vadnais, versus HA of 1200 kg/d in each lake. Performance differences are likely due to lower induced currents at the sediment surface by HO compared to HA.

9:15 Hypolimnetic Oxygenation of Water Supply Reservoirs Using Bubble Plume Diffusers
Mark Mobley1, Paul Gantzer2, Pam Benskin3, Imad Hannoun4, Susan McMahon5, David Austin6, and Roger Scharf6
1Mobley Engineering, Inc., Norris, Tennessee; 2Gantzer Water Resource Engineering, Livingston, Texas; 3Aurora Water, Aurora, Colorado; 4Water Quality Solutions Inc., McGaheysville, Virginia; 5Casitas Municipal Water District, Oak View, California; 6Jacobs, Mendota Heights, Minnesota

Hypolimnetic oxygenation of water supply reservoirs is used to improve raw water quality by preventing anoxia. This paper summarizes the operational results using linear bubble plume diffuser hypolimnetic oxygenation systems installed in water supply reservoirs. The results obtained for eight study sites demonstrate that diffuser technology was effective at increasing hypolimnetic dissolved oxygen (DO) and spreading it to blanket sediments with oxygen. The diffuser systems maintained increased DO in the hypolimnion during successive years of operation at every site. Improved oxygen levels in the reservoir reduced anoxic products and nutrients to mitigate the causes of taste and odor in the source water supplied to water treatment facilities. This resulted in additional treatment capacity, reduced treatment costs and provided an attractive alternative to water treatment plant modifications.

9:35 Decreased Oxygenation Demand Following Hypolimnetic Oxygenation Operation
Paul Gantzer1, Ellen Preece2, Brett Nine3, and Jamie Morris4
1Gantzer Water, Livingston, Texas; 2Robertson and Bryan, Elk Grove, California; 3Colville Tribes Fish and Wildlife, Omak, Washington; 4Western Virginia Water Authority, Roanoke, Virginia

We analyzed long-term oxygenation dynamics in three waterbodies: Spring Hollow Reservoir (SHR), Carvins Cove Reservoir (CCR), both water-supply reservoirs and North Twin Lake (NTL), a natural lake. Long-term line-diffuser hypolimnetic oxygenation system (HOS) operation was 13, 10, and 7 years for SHR, CCR, and NTL respectively. Water column profiles were collected in all three waterbodies using a SeaBird Electronics high-resolution profiler. Additionally, remotely deployed sensors were used to monitor DO in NTL year-round, specifically to capture winter conditions during ice cover. Hypolimnetic oxygen demand (HOD) was observed to decrease after several years of HOS operation in all three waterbodies. Annual HOD decreased more for HOS operated year-round compared to recovery-based operation where HOS was started after dissolved oxygen (DO) decreased. Additionally, HOD throughout the summer stratified period was lower following maintenance of higher DO levels during spring prior to onset of stratification. An analogous result was observed during winter ice over periods relative to DO conditions post stratification. Prior work showed increased HOD during HOS operation compared to pre-HOS. The increased HOD during HOS operation was termed diffuser-induced oxygen demand and implied the HOS was inducing oxygen demand. However, the current work we show HOS operation is not actually inducing oxygen demand, rather it is exposing the existing oxygen demand already in the sediments. Our data suggests a HOS is an effective tool to maintain hypolimnion DO in stratified lakes and reservoirs, and when operated year-round or before DO is observed to decrease, they can decrease HOD, reducing operational costs.

 

H5: Aquatic Invasive Species VI – Herbicide Use

Moderator: Mark Heilman
SePRO Corporation, Carmel, Indiana

8:35 Successful Eradication of Hydrilla verticillata From Seven Waterbodies Within the Great Lakes Basin
Carter L. Bailey1 and Mark J. Warman2
1AQUA DOC Lake & Pond Management Inc., Chardon, Ohio; 2Cleveland Metroparks, Cleveland, Ohio

This 2011–2019 case study reveals the overall effectiveness of low dose (6 ppb) fluoridone applications on Hydrilla verticillata in an eradication capacity over a variety of different freshwater environments. Hydrilla was first discovered in the Cleveland Metroparks system in the Summer of 2011. After its initial identification and subsequent regional search response, the park district determined that the plant was established in seven different park waterbodies, including a quarry lake, pond, two marshlands, and three constructed wetland systems. All of these waterbodies are within the Lake Erie drainage basin, and at the time posed a significant risk of infestation to the Great Lakes.

Low dose fluoridone applications were chosen as the preferred treatment method in order to not harm non-target plant species. A variety of fluoridone formulations and application methods were employed as a part of this eradication effort. Habitat quality was found to play a key role in the selectiveness of the herbicide treatments. Fluoridone applications had little to no impact on native plant species at wetland sites, however maintaining appropriate water levels played a crucial role in hitting target fluoridone concentrations. Overall the program has been very successful, in the summer of 2018 only one hydrilla tuber was found in the annual sampling events. All involved parties are hopeful that no tubers will be found this coming year (2019).

8:55 Developing an Operational Control Plan for Hybrid Milfoil
Terry McNabb1, Kurt Getsinger2, S. Hoyle3, E. Haug3, R. Richardson3, and R. Thum4
1Aquatechnex, LLC, Bellingham, Washington; 2USAERDC, Vicksburg Mississippi; 3North Carolina State University, Raleigh, North Carolina; 4Montana State University, Bozeman, Montana

Eurasian Milfoil is one of the most prolific invasive aquatic species in the northern tier of the United States. Operational control programs targeting this plant have been ongoing for decades in many parts of the plants current range. Many of these programs rely on the use of US EPA Approved herbicides to selectively target this plant and protect native aquatic vegetation.

In recent years applicators have noted a trend towards lower efficacy when using traditional herbicide technologies. This has led researchers to observe that in many lakes, hybrid crosses of Eurasian and native milfoils have occurred, and these species can be more tolerant to conventional treatment approaches.

In 2016 our firm found hybrid strains of milfoil to be present in one of the lakes we manage. This discovery occurred when a conventional and well know treatment technology resulted in less than adequate control. We suspected hybridization, sampled plants from a number of sites and submitted them for DNA analysis. All samples returned as a hybrid strain.

We then submitted a grant application to the Washington Department of Ecology’s Freshwater Aquatic Plant Management Program to develop an operational control strategy for hybrid milfoils and it was funded in 2017.

This program included extensive documentation of milfoil plant communities in Loon Lake (WA), submittal of plant samples for DNA analysis, collection of plant samples for herbicide concentration exposure time studies, contracting for that study, development of chemical responses to various dose rates and herbicides, and scaling lab results up for field application work.

This paper will discuss the problem posed by hybrid milfoil, the steps to develop a lake specific control plan, and operational experiences implementing those plans.

9:15 Integrated Controls for Recalcitrant Aquatic Invasive Plants
G. Douglas Pullman and Bill Rataczyk

Applied Biochemists, Alpharetta, Georgia

Aquatic plants demonstrate a variety of ways to resist the impacts of all forms of and means of management or suppression. Algaecide pretreatments, as adjuvants have helped to minimize microbial plant-surface interference and enhance the effectiveness species targeted species control. Adjuvants are described as additives to herbicide mixtures and dilutions that enhance the activity and performance of the herbicide. Today, the line has become blurred between applications that include adjuvants or applications of herbicide/algaecide combinations where different chemistries play complicated roles in bringing about acceptable outcomes. Enhanced aquatic biocide combinations improve performance outcomes in a variety of ways from modifying water chemistry to stimulating a target plant to make it more susceptible to the herbicidal impacts. AMP is classified as a biological adjuvant because it is a mixture of microbes, proteins, and enzymes. It also represents a new class of adjuvants that seem to stimulate physiological responses to the herbicidal effect of auxinic herbicides to improve treatment outcomes. Field studies will help to elucidate our understanding of these important types of adjuvants and improve the performance of invasive species management programs in the future.

9:35 Empirical Analyses of Long-Term Water Quality, Fish and Aquatic Plant Data in Relation to Aquatic Plant Management Actions
Mark Hoyer

University of Florida, Gainesville, Florida

Based on vocal stakeholder concerns about aquatic plant management (primarily herbicide usage), Florida Fish and Wildlife Conservation Commission (FWC) paused all aquatic plant herbicide treatments while public meetings were held to collected comments on Florida’s aquatic plant management program. Multiple long-term data sets available in Florida can be used to examine relations among water quality, aquatic plant, and fish population metrics in relation to aquatic plant management activities. The Invasive Plant Management section (IPM) of FWC conducts an annual plant survey, which has been continued since 1982. The data base contains aquatic plants surveyed on 397 lakes from 53 Florida counties and includes information on over 200 species of aquatic plants. Since 2010, IPM has maintained Plant Management and Accounting Retrieval System (PMARS) data, which records all aquatic plant herbicide management activities. Florida LAKEWATCH, a volunteer water quality monitoring program, was initiated in 1986 yielding over three decades of water quality data. In 1999, Florida LAKEWATCH in cooperation with FWC started a long-term fish monitoring program, that was standardized by FWC in 2006 yielding consistent fisheries data on approximately 30 public lakes for the last decade. This paper uses the long-term data bases to addresses two of the many concerns FWC receive from stakeholders during the public meetings:

    • Glyphosate is a synthetic phosphonate herbicide and Cyanobacteria can use the phosphorus portion of the glyphosate molecule for growth thus causing harmful algal blooms.
    • Herbicides are toxic to fish and when used in lakes herbicides hurt largemouth bass populations.