Chemical, and Biological Interactions in Rivers,
Estuaries, Lakes, and Coastal Environment
The invasion of invasive dreissenid mussels (Zebra mussels and Quagga mussels, see Figure left below) and their ever-growing population have raised new questions of how they can interact with the transport of contaminated sediments, and whether they have significantly changed the pathways of contaminants in the ecosystem through filtration of suspended solids. Despite recent progresses in understanding the impacts of both contaminated sediments and invasive species on the ecosystem of the coastal Great Lakes, the interactions between them and the implications for the fate of contaminants are largely unknown. There is a need to quantify the mechanisms of the coupling of hydrodynamic and biogeochemical processes, especially those obtained through in situ measurements during resuspension events and subsequent redistribution of sediments in estuaries. Figure middle below depicts possible mechanisms of interactions in a typical estuary system. We raise several questions: (i) What are major forcing terms that cause resuspension of sediment in the river-estuary-nearshore system and what is their relative importance of time scales (short-term episodic or seasonal effects and long-term variations such as the change of climate)? (ii) How do dreissenid mussels respond to the resuspended sediment? Are they able to intercept sediment load through filtration? (iii) What is the subsequent fate of filtered sediment and the associated contaminants in both short-term and long-term time scales? (iv) How would the overall interactions affect associated contaminants redistribution over different spatial scales of river-estuary-nearshore systesms. We are currently examining the interactions between mussels in the coastal water near a harbor and the river plume resulting from resuspension due to physical forcing and human disturbance (during and after dredging). State-of-the-art field instruments are developed to map mussel densities (see Figure right below), and quantify the transport of contaminated sediment plume after resuspension. The exchange rate of suspended sediment particles between the water column and the benthic community colonized by Dreissenid mussels are measured. Data will be used to validate a coupled hydrodynamic-biogeochemical numerical models to facilitate the assessment of ongoing and future remediation efforts.
The turbidity of eutrophic shallow lakes can be affected by sediment resuspension due to wind or benthivorous fish (e.g., carp) feeding (see Figure left below). Previous studies have found that carp can play an important link between the pelagic and the benthic parts of the ecosystem. In general benthic feeding stirs up bottom sediments and uproots macrophytes, causing resuspension of sediments and release of nutrients from these sediments into the water column, leading to the turbid water phases. As nutrients are transported into the lake system, increasing phosphorus fluxes can promote eutrophic waters and provide growth of algae. The phosphorus cycle can further undergo transformations of inorganic phosphorus to organic phosphorus or vice versa. This change in chemical composition describes the production of the system and is responsible for shifts in phytoplankton production versus clear water phases. While we have gained tremendous understanding of the role of carp in shallow lakes (e.g., Lake Wingra), the complex physical-chemical processes caused by carp feeding in a freshwater river-lake estuary (e.g., Cherokee Marsh) have yet been clear. In collaboration with WDNR, our research team employs a telemetry tracking system (see Figure middle below) to register the distribution, seasonal movement, and relative density of carp. Furthermore a real-time acoustic imaging monitoring system (AIMS, see Figure right below) is developed to monitor carp moving in and out of the estuary. Controlled experiments are designed to quantify the effects of carp/wind in disturbing bottom sediment. We invent an in-situ SEdiement Resuspension Oscillation Device (SED-ROD) that could characterize turbulence caused by carp feeding. Our overall goal is to determine when and where carp might be vulnerable to removal efforts to reduce/control carp densities in the estuary as an estuary restoration project.
Issues of rainbow smelt, one of several invasive species, have caused extraordinary ecological and economic damage in several inland lakes of Wisconsinís Northwood. Rainbow smelt compete with native fish for food sources and also prey on juvenile game fishes. As a result populations of several native fish species, such as walleye, yellow perch, and ciscos often decline. To resolve this, an innovative new management technique for removing an entire population of rainbow smelt is to mix water column using our recent developed GELIs (Gradual Entrainment Lake Inverter) device (see Figure left below). By sending warm water to the bottom of the lake and bringing up cold bottom waters to the surface to be warmed by the sun, we can eliminate the cold waters which rainbow smelt need to survive. This mixing would gradually push rainbow smelt beyond their thermal tolerance (see Figure middle below). Ongoing research progress and outcome can be found at the CLAM site (click figure right below). Using GELIs, another on-going NSF project aims to study the composition of bacterial communities in humic lakes, as well as how those communities respond to various natural and human-driven changes.
Sponsor : Dane County Land and Water Resources Department
National Science Foundation (LTER)
NOAA, University of Wisconsin Sea Grant Institute
Wisconsin Department of Natural Resources
Wisconsin Alumni Research Foundation
Status : Active
Nathan Wells (MS), Nathan Gerald (MS), ? (MS or PhD)
Katie Nagel (Undergraduate)
Graduated: Jordan Read (PhD), Hoi-Lai Tseng (MS), Lauren Seabury (MS)
Professor Qian Liao, Unviersity of Wisconsin-Milwaukee
Professor Trina McMahon, CEE/Bacteriology, UW-Madison
Mr. Kurt Welke, Dane County Fisheries Manager, WDNR
Professor Jake Vander Zanden, Center of Limnology, UW-Madison