Lyngbya wollei In Lake Wateree, South Carolina: Management Implications During Lake Drawdown. (30) Margaret A. Carson, Tryston Metz, Geoff I. Scott, John L. Ferry
University of South Carolina, Columbia, SC

Harmful algal blooms (HABs) are naturally occurring, excessive growths of algae that have the potential to produce toxins harmful to water and air quality, aquatic species, and humans. Key forcing factors for the development of HABs include climate change, nutrient enrichment, urbanization, and other anthropogenic activities. Many HAB species are invasive and/or opportunistic and take advantage of altered habitat conditions and Lake Wateree, SC is no exception. Researchers have observed extensive blooms of cyanobacterial algal mats, Lyngbya wollei (Microseira wollei) in Lake Wateree, SC since 2012. This study aimed to address the potential hazards posed by Lyngbya wollei toxins to aquatic species. Algae samples were collected from one site across 3 months on Lake Wateree and used in laboratory toxicity testing. Levels of Lyngbya wollei toxins were quantified, using high resolution mass spectrometry. Toxicity tests using fathead minnows (Pimephales promelas) were conducted using nominal concentrations of freeze-dried, live, and air-dried algae. A total of 3 replicates/treatment/site were used and the mortality over time for the test endpoint of each bioassay. Laboratory toxicity tests indicated that live algae were not toxic but both air dried algae and freeze-dried algae were acutely toxic to the fathead minnow. The mortality results varied based off concentration and month of algae collection. Results of field toxicity tests will be discussed. Laboratory toxicity tests indicated that mortality was lower in air dried algae tests than freeze dried tests. These findings are important as there are two drinking water intakes on Lake Wateree and people continually participating in contact recreation on Lake Wateree. Residents are concerned about the presence of HAB species and the potential for human exposure to the toxin when using the lake. Development of effective management strategies for Lyngbya wollei is important to mitigate potential health impacts, including management strategies during lake drawdowns.

Microseira wollei And Phormidium Algae More Than Doubles DBP Concentrations and Calculated Toxicity in Drinking Water. (27) Md. Tareq Aziz
University of South Carolina, Department of Chemistry and Biochemistry, Columbia, SC

Warm weather and excess nutrients from agricultural runoff trigger harmful algal blooms, which can affect drinking water safety due to the presence of algal toxins and the formation of disinfection by-products (DBPs) during drinking water treatment. In this study, 66 priority, unregulated and regulated DBPs were quantified in chlorinated controlled laboratory reactions of harmful algae Microseira wollei (formerly known as Lyngbya wollei) and Phormidium using gas chromatography (GC)-mass spectrometry (MS). Live algae samples collected from algae-impacted lakes in South Carolina were chlorinated in ultrapure water and real source waters containing NOM. DBPs were also measured in finished water from a drinking water plant impacted by a Microseira bloom. Results show that the presence of Microseira and Phormidium more than doubles total concentrations of DBPs formed by chlorination, with levels up to 587 µg/L formed in natural lake waters. Toxic N-DBPs also more than doubled in concentration, with levels up to 36.1, 3.6, and 37.9 µg/L for haloacetamides, halonitromethanes, and haloacetonitriles, respectively. In ultrapure water, DBPs also formed up to 314 µg/L, demonstrating the ability of algae to serve as direct precursors for these DBPs. When environmentally relevant levels of bromide and iodide were added to chlorination reactions, total DBPs increased 144, 51, and 24% for drinking water reservoir, Lake Marion and Lake Wateree Microseira respectively and 29% for Phormidium. Iodo-DBPs, bromochloroiodomethane, chloroiodoacetic acid, bromoiodoacetic acid, and diiodoacetic acid were observed in finished water from a drinking water plant impacted by Microseira, and bromochloroiodomethane and dibromoiodomethane were observed in chlorinated ultrapure water containing algae, bromide, and iodide. Notably, total calculated cytotoxicity tripled in Microseira–impacted waters and doubled for Phormidium-impacted waters. Calculated genotoxicity doubled for Microseira-impacted waters and more than doubled in Phormidium-impacted waters.

Evaluation of the Utility and Performance of an Autonomous Surface Vehicle for Mobile Monitoring of Waterborne Biochemical Agents. (21) Jessica S. Wolfe¹, Gary D. Chesser¹, John W. Lowe², Jane Moorhead², Gray Turnage³, Dash Padmanava², Robert Moorhead^2
1Mississippi State University, Mississippi State, MS
²Mississippi State Univeristy, Mississippi State, MS
³Mississippi State University, Starkville, MS

There is an increasing need for real-time monitoring and management of water quality in inland and coastal marine environments due to increases in land utilization which negatively impact aquatic ecosystems via surface water runoff. Contemporary monitoring techniques are laborious and expensive, requiring in-situ monitoring stations and/or specialized manned vessel sampling missions at fixed locations for water sample analysis. These techniques limit the ability to gather high resolution spatio-temporal data. Solar powered autonomous surface vehicles (ASV) may provide a long endurance solution to overcome spatio-temporal drawbacks of conventional sampling and data collection by providing a mobile powered platform for sensors/instrumentation. However, commercially available solar powered ASVs are limited, and ASV autopilot navigational accuracy may be affected by environmental conditions (wind, current, and waves) that can alter trajectories and negatively affect spatio-temporal resolution of water quality sampling efforts. The goal of this research was to evaluate the utility and navigational performance of a commercially available solar powered ASV (SeaTrac SP-48) equipped with a multi-sensor payload to operate autonomously under varying conditions of environmental forces. The specific objectives were to evaluate the ASV’s ability to: 1) accurately and repeatedly maintain route heading (measured as cross-track-error [XTE]) and 2) hold a fixed position (measured as time and distance off station) under varying environmental conditions. XTE increased as intensity of environmental forces increased. Time and distance off station were not affected by environmental forces but were affected by internal mission parameters (i.e., station size) as larger stations increased time and distance off station. This work serves to provide a conceptual framework for development of spatial and temporal resolution limitations of ASVs for real-time monitoring campaigns and future development of obstacle avoidance and adaptive sampling technologies. Future work will focus on integration of water quality sensors for in-situ data collection and monitoring.

Giant KelpeR: A Webapp for Exploratory Analysis of Macrocystis pyrifera Population Change in Southern-Central California. (22) Nathan Tennies, Filipe Alberto
University of Wisconsin-Milwaukee Biological Sciences, Milwaukee, WI

On the North American West Coast, giant kelp (Macrocystis pyrifera) population declines have been prevalent with increasing extreme heat waves in sea surface temperature (SST). Individuals typically persist below 22° C and past this quickly die off. Giant kelp is the foundational species of the California coast kelp forest ecosystem. The value of this ecosystem’s services has led to several kelp cover monitoring programs, most using remote imagery. Input data and output products are mostly formatted for academic use despite stakeholder value. To tackle this, we are developing an RShiny webapp to visualize time series of kelp biomass in Southern-Central California with SST changes and derived statistics (number of consecutive days with SST above 22° C and SST anomalies). Rshiny is a package for webapp development in the R language. RShiny users can program a webapp in R ran with HTML and CSS. In our webapp, users click a location on a map of kelp biomass and choose a radius around the selection. In this radius, the previous statistics are calculated from average kelp biomass and SST. Our webapp will help stakeholders and non-specialists explore kelp and SST time series data. Eventually we plan to add spatially explicit kelp genetic monitoring records from projects by our team censusing genetic diversity changes in California kelp beds. Currently we are deploying our webapp online and after will incorporate OpenStreetMap software to improve our map interface and interactivity.

Herbivory and Characteristics of Crested Floating Heart Infestations in the Southern United States. (28) Nathan E. Harms¹, Megann Harlow², Ian A. Knight^3
1United States Army Corps of Engineers – Engineering Research and Development Center, Lewisville, TX
²Oak Ridge Institute for Science and Education, Lewisville, TX
³United States Army Corps of Engineers – Engineering Research and Development Center, Vicksburg, MS

The invasive floating-leaved plant, Nymphoides cristata (crested floating heart; CFH) is increasingly problematic in the southeastern US and requires effective management to prevent negative ecological and economic impacts to aquatic systems. Although biological control is under investigation, preliminary surveys in the invaded range serve to assess existing herbivory and identify any potential agents already present in the US. In 2019, we surveyed 15 CFH populations in Florida, Texas, Louisiana, and South Carolina, and quantified plant-level characteristics (leaf toughness, leaf chemistry, dry mass content (DMC), specific leaf area (SLA)), herbivory (percent leaf area consumed, leaf-feeding insect taxa present) and, in a subset of populations, population-level characteristics (11 sites; flowering, dominance index). Dominance of CFH ranged from 0.87 – 1.0 at surveyed sites and flower production was high (up to 618 / m²). The amount of leaf area consumed by herbivores ranged from 0% to 42% and we detected six herbivorous insect taxa, all generalist species such as the aquatic moths Parapoynx sp. and Elophila (=Synclita) obliteralis, and the leaf beetle Donacia sp. We did not find strong correlations between mean leaf characteristics and percent leaf damage. However, leaf toughness was strongly correlated with %N (r= -0.66), C:N ratio (r= 0.75), and DMC (r= 0.85), and weakly correlated with SLA (r= -0.54). This is the first report of baseline herbivory and infestation characteristics for CFH in its invaded range, and this information can be used in the future to assess potential benefits and possible interactions from biological control, should it be pursued. Additionally, a hybrid N. cristata x N. aquatica population was recently identified in South Carolina, so the ways in which herbivore taxa vary among populations of N. cristata and its hybrid may be important for determining the role of biological control in the future management of the species in the US.

How Many Clips to Kill a Hydrilla Tuber? (29) Taylor L. Darnell¹, Benjamin P. Sperry², Candice M. Prince^3
1University of Florida/ Center for Aquatic Invasive Plants, Gainesville, FL
²US Army Corps of Engineers, Gainesville, FL
³University of Florida, Gainesville, FL

Hydrilla (Hydrilla verticillata) is one of the most problematic aquatic weeds, and one of the most expensive to manage. Hydrilla produces subterranean turions (i.e., tubers) that facilitate regrowth of the population following herbicide application. However, little is known about tuber physiology, sprouting mechanisms, longevity of the tuber bank, or tuber response to adverse environmental conditions. Here, we evaluated the effect of repeated shoot biomass removal on dioecious hydrilla tubers. Shoot biomass was clipped five times over the study period (Dec. 2021 – May 2022), following one of four clipping schemes (900 tubers per experimental run): 1) no clipping (control), 2) removal of all sprouted biomass, 3) removal of the apical tip(s) and 3 or 4 whorls of leaves, and 4) removal of biomass above the third whorl of leaves. This experiment was replicated in space. We recorded the initial tuber weight, as well as length and weight of removed biomass for each clipping time (every 35 days for clipping #1-3, and every 45 days for clipping #4 and #5). For control tubers, we recorded shoot and tuber biomass. Data were regressed over initial tuber starting weights to evaluate the depletion of carbohydrate reserves. The number of clipping events significantly reduced tuber and shoot biomass. The removal of the apical meristem and several whorls of leaves had stimulated biomass production (1.03 g [ shoot and tuber weight], compared to 0.83 g for non-clipped tubers), while removal of all sprouted biomass as well as biomass above the third whorl of leaves decreased biomass production over time. Results suggest that total removal of sprouted biomass may be more effective at exhausting a tuber’s starch reserves than other biomass removal techniques. The removal of all biomass led to secondary node sprouting in several replicates, suggesting that secondary or tertiary node spouting is possible.

Intact Endothall Translocates to the Roots of Aquatic Plants: Providing Evidence of Systemic Activity. Mirella F. Ortiz¹, Scott J. Nissen², Franck E. Dayan^1
1Colorado State University, Fort Collins, CO
²Colorado State University, Ft Collins, CO

Endothall and 2,4-D have been used to control aquatic weeds for more than 60 years, and still there is very little information available about the in planta behavior of these herbicides in aquatic weed species. 2,4-D is purportedly a systemic in aquatic plants based almost entirely on its behavior in terrestrial plants. Several recent studies, using radiolabeled 2,4-D and endothall, demonstrated that plants can translocate the radioactivity from shoots to root systems; however, these values were generated by biological sample oxidation and therefore there was no way to determine if the radioactivity in the roots was parent herbicide or a metabolite(s), and the question of the true systemic behavior for 2,4-D or endothall has not been definitively answered. Therefore, the objective of this research was to use multiple analytical methods to answer the question if 2,4-D and endothall are truly systemic in aquatic plants. By using radiolabeled herbicides, it was possible to determine that 68% and 57% of 2,4-D was extractable from shoots and roots, respectively, while 61.7% and 86.0% endothall was extractable from shoots and roots, respectively. About 17% of extracted ¹⁴C-2,4-D from the shoots metabolized into one single unidentified metabolite, while 41% of extracted ¹⁴C-endothall from the shoots was metabolized also into one single unidentified metabolite. The quantities of intact 2,4-D and endothall present in the roots were about 10 times less than the amount of herbicide in the shoots. The intact 2,4-D detected in the shoots was 1.31 µg g^-1 dry weight (DW) and 0.11 µg g^-1 DW was detected in the roots. For endothall, 1.08 and 0.12 µg g^-1 DW was detected in the shoots and roots, respectively. In conclusion, using a combination of ¹⁴C-labeled studies and analysis of unlabeled herbicides by LC-MS/MS, we can conclude that both 2,4-D and endothall have similar in planta behavior, with about 8-10% of absorbed intact active ingredient translocating to the roots of these aquatic plants.

Integrating Invasive Plant Management Research and Practice: Aquatic Ecosystem Restoration in the Texas Western Gulf Coast Plain/Lower Rio Grande Alluvial Floodplain. (31) Aaron N. Schad
U.S. Army Corps of Engineers, Lewisville, TX

As part of the U.S. Army Corps of Engineers (USACE) environmental mission, aquatic ecosystem restoration (AER) projects focus on restoring aquatic habitats for the benefit of fish and other wildlife. Since 2017, USACE Engineer Research and Development Center researchers in the Aquatic Ecology and Invasive Species Branch have collaborated with USACE Galveston District, The Nature Conservancy, U.S. Fish and Wildlife Service, National Park Service, and local non-Federal sponsors to study restoration methods on former, naturally cut-off, channels of the Lower Rio Grande River, TX, USA. Locally termed “resacas”, these aquatic ecosystems which are home to endemic species, have been degraded by disconnection, urbanization, and invasive species—primarily Brazilian peppertree (Schinus terebinthifolia). This presentation will document the research, planning, design, construction, monitoring, and adaptive management activities throughout the multiagency restoration and research projects. In particular, new research, funded by the USACE Aquatic Plant Control Research Program (APCRP), focusing on a new biological control agent for Brazilian peppertree—the Brazilian peppertree thrips (Pseudophilothrips ichini)—and the benefits of integrating invasive weed biological control into USACE AER projects are highlighted. Methods and results for invasive species management and aquatic and riparian vegetation establishment in endemic Texas ebony resaca forest, subtropical Texas palmetto woodland, and Texas ebony/snake-eyes shrubland habitats are also discussed.

Invasive Aquatic and Native Marine Vegetation on the Mississippi Barrier Islands. (20) Gray Turnage, Andrew Sample
Mississippi State University, Starkville, MS

Seagrass beds serve as feeding and spawning habitat for many species of marine fauna. Barrier island lagoons may act as refugia for seagrass species that are vital components of marine ecosystems in the Gulf of Mexico and the Mississippi Sound. Lagoons may also be invaded by aquatic invasive plant species (AIS) capable of surviving brackish environments. Loss of ecosystem function due to AIS has been documented in many brackish and saline habitats, suggesting that AIS invasion could further reduce seagrass abundance in island lagoons such that these sites no longer function as nursery populations that replenish seagrass beds in the Mississippi Sound. The goal of this project was to survey the aquatic and marine vegetation in select lagoons on the four major barrier islands (Petit Bois, Horn, Ship, and Cat) of Mississippi to 1) determine the aquatic/marine plant community of each lagoon and 2) determine if AIS were present in these systems. Twelve lagoons and six reference sites in the MS Sound were identified and surveyed in 2020 using the point intercept method to generate baseline density of seagrasses. All lagoons had vegetation present with Shoal grass (native) and torpedograss (AIS) being the most prevalent species. Seagrass was recorded in 58% of lagoons with 70% of those populations potentially serving as nursery populations for offshore sites adjacent to each island and approximately 40% serving as nursery sites across the Mississippi Sound. However, AIS were present in 66% of lagoons and co-occurred with seagrass populations in 25% of lagoons. To our knowledge, this is the first work to document AIS co-occurring with seagrasses on the Mississippi Barrier islands. Future reduction of AIS in lagoons may allow for subsequent colonization by seagrasses which could further increase the abundance of nursery seagrass populations in the Mississippi Sound.

Meet the New Arrival: Ribbonweed (Vallisneria australis) in the Sacramento-San Joaquin River Delta. (23) John D. Madsen¹, John Miskella¹, Patricia Gilbert^2
1USDA-ARS, Davis, CA
²California Division of Boating and Waterways, Sacramento, CA

Ribbonweed (Vallisneria australis S.W.L. Jacobs and Les). Ribbonweed is native to eastern Australia. Common names used for this species also include Australian watercelery and Australian eelgrass. Although native to Australia, it is a common nuisance weed to Australian irrigation canals and rivers. It is an introduced weed to western Australia, New Zealand, Japan, Europe, and now norther California. In northern California, it has been found in the northern portion of the Delta. It was found in parcel shipments to California for sale in the aquarium trade. In the aquarium trade, it is often referred to (erroneously) as V. gigantea. In Europe, New Zealand, and now California, it has been rated as a noxious weed, with the regulatory consequences that suggests. Ribbonweed is a submersed plant that forms numerous strap-like leaves from a rosette, up to 3 m long and up to 35 mm wide. The leaves have 5-6 longitudinal veins. The plant is dioecious, forming pistillate and staminate flowers from separate plants; not unlike other species of Vallisneria. When introduced to a new range, it is easily confused with other species of Vallisneria, but the leaves are much larger. The plants spread new rosettes from stolons. In Australia and New Zealand, the plant is controlled using diquat and both formulations of endothall. Further studies on the distribution and management of V. australis in the Delta are anticipated.

Release and Chemical Fate of Lyngbya wollei Toxins from Microseira wollei-Dominated Microbial Mats. (26) Tryston Metz, Samuel P. Putnam, Geoffrey I. Scott, John L. Ferry
University of South Carolina, Columbia, SC

Microseira wollei is a benthic cyanobacteria that is widespread in hydroelectric reservoirs in the Southeastern US. This cyanobacteria forms dense, filamentous mats with biomass that can exceed 10 kg per square meter. Additionally, M. wollei is known to produce analogues of the paralytic shellfish toxin saxitoxin. These analogues, LWTs, are not as toxic as saxitoxin but can occur in high concentrations in the organism. The role of these mats as reservoirs of neurotoxins is therefore concerning for environmental and human health. M. wollei mats typically grow along the shoreline and in hydroelectric reservoirs, where water levels can fluctuate quickly, are often subjected to sudden exposure and re-wetting cycles. This work explores the stability of the LWTs in drying biomass, their role of drying and re-wetting as factors in the release of the LWT reservoir, and the chemical fate of LWTs in the water column once released. Work presented here explores the environmental fate of the LWTs in natural lake waters over the wide range of temperatures and pHs observed in the field adjacent to M. wollei-dominated microbial mats in Lake Wateree, SC. M. wollei samples were collected from multiple points in the reservoir and processed in the laboratory to quantify and qualify the LWTs present in each sample. Leaching studies were performed to determine the possibility that toxins could be released from live or dessicated algal samples into surrounding waters. Leaching from dessicated algae was observed to be a facile process, but the LWTs were not persistent in the water column. The role of pH (6-10) and temperature (10^oC-40^oC) in their degradation was assayed through a quantitative multifactorial experiment, and a numerical model predicting hydrolysis rate and by-product formation is presented. A model of net hazard in the water (expressed as saxitoxin equivalents) is presented.

Results of International Natural Enemy Surveys for Biological Control of Yellow Floating Heart in the US. (24) Nathan E. Harms¹, Matthew Purcell², Megann Harlow³, Patrick Häfliger⁴, Hong Sun-hee⁵, Jialiang Zhang⁶, Sonja Stutz⁴, Ian A. Knight⁷, Chenxi Liu^8
1United States Army Corps of Engineers – Engineering Research and Development Center, Lewisville, TX
²USDA ARS Australian Biocontrol Laboratory, Brisbane, Australia
³Oak Ridge Institute for Science and Education, Lewisville, TX
⁴CABI, Delémont, Switzerland
⁵Hankyong University, Anseong, South Korea
⁶Huanggang Normal University, Huanggang, China
⁷United States Army Corps of Engineers – Engineering Research and Development Center, Vicksburg, MS
⁸USDA ARS Sino-American Biological Control Laboratory, Beijing, China

Yellow floating heart (YFH; Nymphoides peltata) is a widespread floating-leaved aquatic invasive plant in the US. To provide a long-lasting sustainable method of control, biological control of YFH is under development. The first step in biological control development is native range surveys to locate host-specific and damaging agents (natural enemies). From 2018-2021, we conducted YFH surveys in Europe (16 locations) and Asia (80 locations) to create a list of candidate agents and collect baseline infestation data for comparison between introduced and native ranges. Previous genetic work found that YFH in the US was most-closely related to populations in Europe but we found no promising agents in Europe except for two fungal pathogens previously reported in the literature. In Asia, 11 arthropod species were identified as potential biocontrol agents based on observed damage in situ and literature reports about host-specificity. Of particular interest are three species of Bagous weevils, one of which may be Bagous charbenensi, and a leaf-mining Hydrellia fly species, yet to be identified. During domestic surveys in the US, generalist leaf-cutting caterpillars were common. A major discovery was the damaging fungal pathogen, Septoria villarsiae isolated from plants in a private pond in Maine- a first record in the Western hemisphere. Pathogen host-specificity testing is underway now. Next steps for this program should include initial host-specificity and impact assessments of the fruit-feeding Bagous spp. in China, and the leaf-mining Hydrellia sp. fly from South Korea.

Sprouting Characteristics of Flowering Rush (Butomus umbellatus) Propagules. (25) Bradley T. Sartain¹, Nathan E. Harms², Ashton B. DeRossette¹, Sandor G. Dibble^3
1US Army Corps of Engineers Engineer Research and Development Center, Vicksburg, MS
²United States Army Corps of Engineers – Engineering Research and Development Center, Lewisville, TX
³Oak Ridge Institute for Science and Education, Vicksburg, MS

Flowering rush (Butomus umbellatus) is an invasive Eurasian aquatic weed in the US, with several diploid and at least one triploid genotypes in the US and Canada. Spread of flowering rush is primary clonal in the US, but the factors that promote sprouting of propagules, and whether those factors vary by genotype are unknown. We conducted a series of growth chamber experiments using four flowering rush genotypes (one triploid, three diploid) to investigate the role of shade or temperature for rhizome (triploid) or bulbil (diploid) sprouting. For the first shade study, bulbils and rhizome segments with a single bud were harvested from parent plants in October 2021 and placed into petri dishes under five shade treatments. Bulbil and rhizome segments were monitored for sprouting over a four-week period. In the second shade study, the experiment was repeated except diploid bulbils were cold-stratified at 4°C for 5 weeks beforehand. In both experiments, shade had a minimal effect on sprouting. The proportion of sprouted triploid rhizome segments ranged from 0.90 to 0.99 whereas diploid bulbils ranged from 0.00 to 0.18 without cold-stratification. After holding at 4?, the proportion of sprouted bulbils increased to =0.93 across diploid genotypes. To assess the role of temperature in propagule sprouting, we harvested rhizomes and bulbils in November 2021, then held them at 4°C until April 2022, at which point we placed them in growth chambers at 5, 10, 20, 25, 30, and 35°C and monitored sprouting for six weeks. After six weeks we confirmed viability of low temperature treatments by moving those propagules to 25°C for an additional two weeks. Maximum sprouting occurred at 20°C and 25°C for triploid populations and 25C° and 30°C for diploid populations, although bulbil sprouting was significantly lower than rhizomes, which often had more than one sprout per segment.