Research Interests

limnology, aquatic ecology, landscape ecology, eutrophication, phytoplankton ecology, land-lake connection, climate change, aquatic modeling, statistcal modeling, Bayesian statistics, uncertainty anlysis, spatial patterns

Most of the earth’s freshwater is frozen. In fact, less than 1.5% is liquid and found on the surface, and this water is not distributed evenly around the globe. As the effects of climate change and human activity continue to degrade water quality, even less of that water is available for use by humans and many other organisms that rely on clean water for survival. Some of these threats include invasive species, toxic pollutants, nutrient pollution and eutrophication, harmful algal blooms, and restructured ecosystems. It is of vital importance that we protect and manage our freshwater resources for today and future generations.

Alhtough the threats listed above, and others not listed, are unique and important challenges, I am broadly interested in how climate and watershed infleunces impact freshwater quality. My work to date has primarily focused on how climate and watersheds shape phytoplankton dyanmics in lakes, with an emphasis on cyanobacterial blooms. I have tackled these questions using diverse approaches including field monitoring, experimental work, and computer modeling. I’ve done work on these topics in small inland lakes as well as Lake Superior. I am also interested the role of streams in lake water quality, how organic nutrients affects phtyoplankton community structure and function, and integrating field and laboratory data with new modeling techniques.

Current Work

HiTIDER

The aim of the History and Topography to Improve Decision-making for Estuary Restoration (HiTIDER) Project is detecting estuarine habitat loss and opportunities for future restoration in and around National Estuarine Research Reserves. This project is funded through the National Estuarine Research Reserve System Science Collaborative and employs historical and elevation-based mapping to describe the past, current, and future condition of major estuaries across the US.

Emerald Ash Borer Understory Planting

This work is focused on continuiing work conducted by Nicholas Bolton at Michigan Technological University in 2015-2017 which evaluated the survival of different tree sepcies that had potential for replacing ash trees being killed by the Emeral Ash Borer. This treatments in this project included herbivore repellants, elevation differences, varied planting techniqies, and other factors. We are returning to these sites in 2021 to evaluate survival of differences species and efficacy of dfferent treatments.

Cold-water Blooms

This project is a review paper developed from a the GLEON Cyanoabcteria Working Group. Phytoplankton blooms are on the rise globally and present significant challenges to managers and threaten ecological and public health. These blooms are typically associated with high temperatures (>20°C) and high nutrient concentrations. However, blooms are commonly observed outside of these conditions. We present documentation of blooms in cold-water conditions (<15°C), with an emphasis on green algae and cyanobacteria. There are three primary modes of cold-water bloom development: 1) those that were developed in preceding warmer conditions (e.g. >15°C), but observed during cold water temperatures (<15°C), 2) deep chlorophyll layers brought to the surface by mixing or upwelling events, and 3) blooms that truly developed in colder temperatures, possibly fueled by nutrients previously contained within the hypolimnia, or under ice. We also explore the antecedent conditions (e.g., biochemical and physical), ecological implications of cold-water blooms including carryover impacts to the summer/growing season, and how a changing climate may affect their occurrence. This work highlights an important aspect of cold-water bloom ecology that has been largely overlooked and demonstrates a need for new research on blooms that occur outside of conditions typically associated with phytoplankton blooms.

Cont Limno

This work is part of the larger LAGOS project which is “a research program for the interdisciplinary, continental-scale study of lakes through time.” My work will focus on leveraging this and other datasets to develop contenental scale models to predict water quality and investgate research questions regarding lakes characteristics at varying spatial scales.

Lake Superior Cyanobacteria Life Cycle Model

Recently emerging cyanobacterial blooms in oligotrophic Lake Superior have been primarily dominated by Dolichospermum lemmermannii with akinetes present. We developed a life cycle model that incorporates this potentially important life stage using field data for temperature and nutrients. We tested 4 sets of akinete germination conditions using combinations of photosynthetically active radiation, total dissolved phosphorus, and temperature, and employed 2 approaches to model growth (minimum and multiplicative) for a total of 8 model runs. We also tested 4 model scenarios including 2x river TDP inputs, increased temperature, no river loading of cyanobacteria, and 2x river loading with 2 growth formulas and 4 germination conditions for a total of 32 model runs.

Past Projects

Organic Nutrients

This project is a review paper developed from a the GLEON Cyanoabcteria Working Group. Macronutrients (C,N,P) are critical for the growth of algae and cyanobacteria; however, we don’t have a good understanding of how different nutrient forms are utilized, particularly organic forms. This knowledge is critical in understanding cyanobacterial growth, subsequent bloom formation, succession, collapse and associated metabolite form/type (associated toxins), especially where nutrient control measures are being implemented.

Cooperative Science and Monitoring Initiative (CSMI) - Lake Superior 2021

The Cooperative Science and Monitoring Initiative (CSMI) is an initiative of the Science Annex of the Great Lakes Restoration Initiative. CSMI focuses on one of the Great Lakes each year with priorities set under LAMPs (Lake-wide Action Management Plans) for each lake. Every 5 years is an intensive sampling year, with the other 4 years having their own specific objective including data analysis, reporting out, setting priorities, and planning for the next field year.

As part of the broader effort I have co-led the coordination of CSMI funded and non-CSMI funded work in the nearshore of Lake Superior for the 2021 field sampling year which includes EPA, USGS, WI DNR, NPS-Apostle Islands, UMD-NRRI, UMD-LLO, LS-NERR, Northland College, and others. Part of my work has included developing interactive maps and an ArcGIS Online website that have been used as planning tools to coordinate efforts to develop a comprehensive sampling effort for Lake Superior and to communicate with the public. I am also working with others to develop a metadata repository for CSMI data and assisstig in coordinating an end of season data meeting to discuss insights from the field season and identify manuscript opportunities.

Cyanobacterial Blooms in Oligotrophic Systems

This project is a review paper developed from a the GLEON. Cyanoabcteria Working Group.Cyanobacterial blooms are a globally significant challenge in marine and freshwater systems. A central theme to this body of work is that blooms are caused by anthropogenic eutrophication. While there is a wealth of evidence that high nutrient loads promote cyanobacterial blooms, there is also widespread evidence that blooms occur in oligotrophic systems, and that they are not a recent phenomenon. Some metalimnetic bloom-forming cyanobacteria, such as Planktothrix rubescens in Lake Bourget France, Switzerland, even appeared in a context of strong re-oligotrophication because of increased light availability in the metalimnion. Moreover, despite a worldwide trend towards eutrophication, there is a substantial number of lakes where successful restoration programmes have reduced nutrient levels to mesotrophic or oligotrophic conditions, yet blooms persist.

Fluvial Seeding of Cyanobacterial Blooms in Lake Superior

Lake Superior has recently begun experiencing cyanobacterial blooms comprised of Dolichospermum lemmermannii near the Apostle Islands and along the southern shore of the western arm. Little is known about the origin of these blooms. Experiments were conducted during the summers of 2017 and 2018 to identify sources of propagules and characteristics of sites that were potential sources. The 2017 experiments were conducted using a factorial design with three source zones (‘River’, ‘Lake’, and ‘Harbor’), two nutrient conditions (high and low N:P), and three temperatures (15, 20, and 25°C). At the end of the experiment, cyanobacteria were most abundant from the ‘River’ and ‘Harbor’ zones at low N:P and 20 and 25°C, with D. lemmermannii most abundant at 20°C. Subsequently, in 2018 we evaluated 26 specific inland locations from three waterbody types (‘River’, ‘Lake/Pond’, and ‘Coastal’) and explored similarities among those sites that produced cyanobacteria in high abundance when samples were incubated under optimal conditions (low N:P and 25°C). Under these growing conditions, we found high cyanobacteria abundance developed in samples from river sites with low ambient temperatures and high conductivity. Field monitoring showed that Lake Superior nearshore temperatures were higher than rivers. These observations suggest that blooms of D. lemmermannii in Lake Superior are initiated by fluvial seeding of propagules and highlight the importance of warmer temperatures and favorable nutrient and light conditions for subsequent extensive cyanobacterial growth. We argue that the watershed is an important source of biological loading of D. lemmermannii to Lake Superior and that when those cells reach the nearshore where there are warmer water temperatures and increased light, they can grow in abundance to produce blooms.

Seasonality and physical drivers of deep chlorophyll layers in Lake Superior, with implications for a rapidly warming lake

A deep chlorophyll layer (DCL) is a common feature of many deep, oligotrophic lakes including Lake Superior. Mechanisms generating and maintaining DCLs are variable across lakes, and seasonal patterns and relationships of DCL structure to physical variables are not well described. Using vertical profile data for physical and biological variables from western and central Lake Superior, we described seasonal patterns in DCL structure and other physical and biological parameters and applied linear mixed-effects models to determine how different physical factors (surface temperature, thermocline depth, and 1% photosynthetically active radiation (PAR) depth) affect the depth, thickness, maximum concentration, and integrated chlorophyll of the DCL. We observed clear seasonal patterns in the development and degradation of the DCL that coincide with seasonal changes in light and temperature. Modeling analysis using linear mixed-effects models showed that the DCL thickness was best predicted by surface temperature (R2 = 0.51) followed by thermocline depth (R2 = 0.36), and the deep chlorophyll maximum (DCM) concentration was best predicted by surface temperature (R2 = 0.26). The 1% PAR depth was not implicated as an important predictor, but observations from seasonal data suggest that it plays a role in the depth of the DCM. While no relationship was found between surface temperature and DCL-integrated chlorophyll, DCL thickness decreased and DCM concentration increased with increasing surface temperature, which could have implications for productivity in the DCL as the lake continues to warm.