If you are interested in chairing a contributed session, please contact meetings@aslo.org with your name, institution, email address and experience with the sessions’ topic.
Lead Organizer: ASLO Meetings, Association for the Sciences of Limnology and Oceanography (meetings@aslo.org)
Presentations
09:00 AM
Visitor perception of lake water quality in highly-managed urban lakes (8051)
Primary Presenter: Gaston Small, University of St. Thomas (gaston.small@stthomas.edu)
Urban lakes provide an important opportunity for humans to interact with nature. Managing water quality in urban lakes is challenging and often requires large investments. While data on water quality are typically collected by management organizations, we know less about how these management activities affect user perception of lake water quality. We collected user perception data from two highly-visited urban lakes in Saint Paul, Minnesota, using an SMS-based chatbot. Signs posted at three high-traffic locations around each lake invited visitors to text a response to a “hook question”, which initiated the survey. We collected data from Como Lake, a 27-ha lake that has recently been the focus of an intensive phosphorus and macrophyte management effort, in 2022 and 2023. In 2023, we also collected data from Lake Phalen, an 80-ha lake with a less-urbanized watershed. Visitor perception of lake water quality showed seasonal patterns that generally tracked chlorophyll and water clarity. Water quality perceptions in Como Lake also reflected a large inter-annual difference between late summers of the two study years. However, a large difference in water clarity and chlorophyll between Lake Phalen and Como Lake was not reflected in water quality perception scores. Perceived changes in lake water quality over time reflect water quality conditions at the time of the response more than multi-year trends in chlorophyll or transparency. These results suggest that visitor perception of water quality is likely influenced by a variety of lake-specific factors, potentially including messaging from management organizations.
09:15 AM
A paleolimnological approach to assessing water quality through time in three distinct urban lakes (8251)
Primary Presenter: savanna wooten, Auburn University (slw0093@auburn.edu)
Paleolimnology utilizes sediment records as a tool to assess the magnitude and onset of water quality shifts in urban aquatic systems, especially where monitoring data fail to precede anthropogenic impacts. Here, we assess the impacts of urbanization on water quality using sediment core data from three lakes: Lake Parker (Florida, USA) in a primarily industrial watershed, Lake Howard (Florida, USA) in a primarily residential watershed, and Lake Coba (Yucatan, MEX) in a watershed considered urban during Prehistoric Maya occupation. Using proxies such as photosynthetic pigments, nutrients, heavy metals and organic matter, we assessed how alterations in urban land use affect sediment biogeochemistry, pollution storage, and whole-lake eutrophication in urban systems. The two modern urban lakes (Parker, Howard) differ in concentrations of nutrients and heavy metals and differ somewhat in algal community composition. However, the timing of substantial biogeochemical shifts in these systems is comparable, revealing synchronous increases in urban-associated elements accelerating around 1940 CE. Early data from Lake Coba show persistent and corresponding upticks in nutrients (e.g., potassium, phosphorus) and heavy metals (e.g., iron, aluminum, copper, etc.) during Prehistoric occupation that ultimately return to baseline conditions, indicating potential for lake recovery after dense human presence.
09:30 AM
Physical and Environmental Controls of Urban Pond Hydrodynamics and Impacts on Dissolved Oxygen and Phosphorus (8364)
Primary Presenter: Benjamin Janke, University of Minnesota (janke024@umn.edu)
Small water bodies such as ponds and wetlands are highly abundant in urban landscapes. These systems are widely used to protect urban lakes and streams and as such, are often subject to intense inputs of runoff and pollutants, and are found across a vast range of age, land use, and topographic setting. Interactions between physical and biogeochemical processes are less studied in ponds and yet, as in lakes, oxygen dynamics and mixing processes have strong influences over nutrient cycles. We studied over 20 urban ponds in the Minneapolis-St. Paul metropolitan area (MN) to better understand the physical and biological factors that influence their water quality and phosphorus dynamics, and ultimately their function for stormwater management. Using continuous monitoring of drivers including water temperature, stormwater runoff, and wind speed, we studied patterns of sub-daily mixing across a gradient of pond size, depth and sheltering, and related to key water quality parameters like phosphorus concentration and dissolved oxygen. Causes of mixing and stratification were explored and found to relate to weather, wind sheltering, macrophyte coverage, and pond geometry. We found that anoxia was associated with higher phosphorus, enhanced by free-floating plant cover, and reduced by mixing frequency. Larger ponds with less surrounding canopy were mixed more frequently by wind or heat exchange, while smaller ponds with heavy vegetation cover were mixed more often by runoff. These results have implications for pond management, especially under warmer and wetter future climate.
09:45 AM
Barriers to the spread of invasive scud (Apocorophium lacustre) in the Chicago Area Waterway System (7858)
Primary Presenter: John Bieber, Loyola University Chicago (jbieber@luc.edu)
Scud (Apocorophium lacustre) is a high-risk invasive species that threatens to spread into the Great Lakes Basin from the Mississippi River Basin. It was discovered in the Illinois River in 2005 but has not spread from there into the Chicago Area Waterway System (CAWS) that connects the Mississippi River to the Great Lakes. Understanding the current limits to scud spread, and identifying ways to reduce future spread, is critical for managers. We conducted three experiments to determine how scud respond to potential barriers for invasion including water quality in the CAWS, an electric barrier, and ranges of CO2 enriched water that is a proposed barrier in the CAWS. We found that water from the CAWS led to a 20% reduction in scud survival over 96 h compared to Illinois River and Lake Michigan, although overall survival remained high (~65%). Second, we found that the presence of electric and CO2 barriers at high strength and concentration significantly reduced movement in scud. Specifically, we found that field-strengths 3 times greater than the operating limit of 2.3 V·in and CO2 concentrations at the EPA limit and higher (>150 mg/L) caused greater scud immobility compared to lower and permissible levels. We conclude that scud has potential to spread within the CAWS to the Great Lakes despite water quality and electric barriers currently in place. Carbon dioxide barriers are unlikely to be effective. Our findings highlight the need for additional management and investigation into strategies which can prevent the spread of scud into the Great Lakes.
10:00 AM
DISTRIBUTION OF METALS AND PAHS IN SEDIMENTS OF MULTIPLE URBAN STORMWATER CONTROL PONDS (8140)
Primary Presenter: Michael Mallin, University of North Carolina - Wilmington (mallinm@uncw.edu)
Sediments of 20 urban and suburban costal wet detention ponds in urbanized New Hanover County, N.C. were surveyed for primary pollutant metals, polycyclic aromatic hydrocarbons (PAHs) and phosphorus (P) in summer and fall 2022. These stormwater control devices drain into the upper reaches of estuarine tidal creeks. The sampling program was undertaken because the public is often exposed to such ponds, and uses them for fishing and pet play, with unknown chemical dangers. A variety of drainage basin types sent stormwater into these ponds, which included three golf course ponds, three fire department ponds, several residential area ponds and ponds representing commercial, recreational, and waste runoff areas; a natural control pond was sampled within a nearby state park. Two types of P were analyzed for; water soluble and more tightly bound fractions extracted by the Melich 3 reagent. Analytical results were compared to various pond physical and drainage basin attributes. Total watershed size or pond age was not related to chemical contamination, but both total impervious area and percent impervious coverage were correlated with several PAHs, Cr and soluble P. Grain size was inversely related only to Cr and TP concentrations. However, organic composition of sediments was a very significant factor controlling the concentrations (i.e. retention) of TP, metals and PAHs in the detention ponds; a factor that can be controlled by pond construction, restoration and management.
10:15 AM
URBAN STREET TREE LITTER IS A KEY DRIVER OF STORMWATER NUTRIENT CONCENTRATIONS AND YIELDS THROUGHOUT THE YEAR (8366)
Primary Presenter: Erin Mittag, University of Minnesota (mitta062@umn.edu)
Street trees in urban environments can be important conduits for nutrients to stormwater; they take up nitrogen (N) and phosphorus (P) from soils and deposit them onto streets in the form of litterfall. These nutrients can rapidly enter stormwater in dissolved and particulate forms, contributing to eutrophication of receiving waters. Our goal was to quantify the contribution of street tree litterfall to stormwater nutrient concentrations and yields. Using data from high-frequency street sweeping programs in the Twin Cities Metro Area (TCMA), we modeled the relationship between percent canopy cover over streets and the mass of litter N and P swept across seasons. We used these relationships to estimate litter-associated N and P deposited onto streets based on average tree canopy cover over streets, then compared these estimates to observed nutrient yields and concentrations from 12 TCMA watersheds. We predicted that litterfall contributes an average of 76% and 67% of stormwater N and P yields during the snow-free season, with the greatest contributions in the spring and fall. Predicted contributions from litterfall ranged greatly between watersheds (36–140% for N and 7–115% for P) likely due to factors influencing stormwater runoff volume and nutrient retention. Estimated litterfall-associated nutrients were a significant predictor of stormwater N and P concentrations across all seasons. These findings suggest that street sweeping and street tree management can be tools to address excess nutrients in urban freshwaters.
CS23 - Urban Ecosystems
Description
Time: 9:00 AM
Date: 5/6/2024
Room: Lecture Hall