|Poconos||Canadian Rockies||Rocky Mountains||Lake Tahoe||IGERT|
Lakes as Sentinels- Using buoys and advanced sensors to study lakes
As the lowest point in the surrounding terrestrial catchment, lakes serve as indicators or sentinels of change in the landscape. To better understand the role of lakes as sentinels, scientists are identifying the key lake variables that respond to changes in the watershed both seasonally and over the long term.
GLEON (Global Lakes Ecological Observatory Network) engages limnologists and information scientists in a global network of lake sensors to document signals that lakes give as they respond to changes in the surrounding watershed and climate. In this spirit, the Global Change Limnology Laboratory has deployed buoys in several regions of North America, including the Rocky Mountains (Heart and Beartooth lakes in the Beartooth Mountains of Montana and Wyoming; Lake Oesa in Yoho National Park, Canada) and the Poconos (lakes Giles and Lacawac in eastern Pennsylvania), as well as in an Arctic lake in Greenland.
The remote location of many of our study lakes challenged lab members to think creatively about the design of the buoys as all of the equipment is carried in backpacks by only a few individuals (images left). With the help of Fondriest Environmental, graduate students in the IGERT-EARS program designed a buoy that was lightweight and able to sample 10 water and 6 weather parameters. This "mobile" buoy weighs a mere 30 lbs without sensors and is fairly inconspicuous (see Images of mobile buoy), an important consideration for an instrument deployed in a remote pristine landscapes.
A second, "profiling" buoy was designed to measure changes in lakes by sampling at different depths. A suite of sensors including CDOM, chlorophyll-a, phycocyanin, dissolved oxygen, pH, turbidity, and underwater PAR collected data at hourly intervals at the surface of the lake and performed automated profiles to the maximum depth of the lake every four hours. With the recent increase in extreme events such as episodic storm events or severe drought that strongly affect the vertical zonation of lakes, the profiling buoy will improve our understanding of the effects of climate change on aquatic ecosystems.
With the help of the sensors on these buoys, we hope to better understand how changes in the watershed affect variables such as lake transparency, dissolved organic carbon (DOC), and chlorophyll. With these data, we can track how lakes change seasonally as well as ask questions about the ecological consequences of these changes including the timing, causes, and consequences of harmful algal blooms and oxygen depletion (hypoxia, anoxia).
Below are data collected from the mobile buoy deployed in Heart Lake (2010) following ice-out. These data revealed that there was a spike in chlorophyll after the ice melted and then a drop in concentration to a level comparable to other lakes in the region. High resolution data from this buoy also enabled us to track the establishment of thermal stratification in Heart Lake as well as seasonal changes in CDOM (chromophoric dissolved organic matter).
The use of a portable buoy sensor system provides the unique opportunity to explore the idea of lakes as sentinels in remote locations, while a profiling buoy facilitates our understanding by collecting data throughout the water column. Integration and collaboration with programs such as IGERT-EARS and GLEON enable us to employ advanced sensor tools and compare our suite of lakes to changes observed across the continent and globe.
One of the major projects ongoing in the Global Change Limnology Lab is assessing the role of vertical temperature profiles in lakes as sentinels of both air temperature and precipitation components of climate change.
Pocono Lakes- Lacawac Sanctuary as a "Hub for EONS" (Ecological Observatory Networks)
This work is centered at the Lacawac Sanctuary where a new field laboratory is being built as one component of creating a "Hub for EONS" (ecological observatory networks) at Lake Lacawac. For over 25 years, we have collected limnological data from two lakes, Giles and Lacawac, in eastern Pennsylvania. During this time, the lab has compiled a large data set, including information about
- UV, temperature, and dissolved oxygen depth profiles,
- the quantity and quality of dissolved organic matter (DOM),
- phytoplankton community composition, and
- zooplankton community composition and vertical distribution.
Lake Giles and Lake Lacawac were the home of the UV Lakes project. From 2002-2009, 10 researchers from eight institutions worked to investigate the interactive effects of UV and temperature on pelagic food webs.
Lake Giles (above, left) is a transparent, low DOM lake. In contrast, Lake Lacawac (above, right), which is part of the Lacawac Field Station, is characterized by higher DOM. Because DOM is one of the main factors controlling UV transparency, these striking differences provide a unique opportunity to investigate the effects of UV on the aquatic community. Nearby Lake Waynewood, a more productive lake very similar in size to Lacawac, completes an interesting set of lakes that vary in their trophic status from oligotrophic, blue-water Lake Giles to mesotrophic/dystrophic, brown-water Lake Lacawac, to more eutrophic, green-water Lake Waynewood. Numerous experiments have been conducted at these sites by collaborating researchers, as well as graduate and undergraduate students through the years.
Our collaborative research in these two study lakes has shown substantial increases in DOM associated with decreases in UV transparency, depth of the thermocline, and increases in oxygen depletion. These changes in UV are important because UV drives the vertical migration of some zooplankton species in transparent lakes. Yellow perch spawn their egg masses at deeper depths in the more transparent Lake Giles. Experiments have shown that if perch spawned at shallower depths their eggs would perish due to the high UV levels. Dramatic changes in UV transparency have been observed in Lake Giles during the summer. UV used to penetrate to depths of over 15 m in July, but now the 1% attenuation (of 320nm UV surface irradiance) depths are closer to 2-4 m. This decrease in transparency in Lake Giles is likely due largely to increases in precipitation in the region and hence greater terrestrial DOM inputs. Recovery from acid deposition related to the Clean Air Act Amendments may also be involved. Research continues in these lakes, and with the building of a new laboratory, hiring of a new Director of Research and Education, new collaborations, and development of the programs at the Field Station, exciting opportunities exist.
Canadian Rocky Mountain Lakes
Climate Change and Zooplankton Species Shifts in the Canadian Rockies
In the Canadian Rockies we are working in collaboration with Janet Fischer and Mark Olson from Franklin and Marshall College on fishless lakes where the lack of visual predators provides an excellent system for exploring the effects of UV radiation on the vertical distribution and invasion potential of zooplankton with climate change. Both visual predators and UV may cause downward avoidance migrations of zooplankton during the day, so the lack of visual predators permits us to focus on UV effects. Variation in visual predation and UV exposure can lead to strong differences in the size, pigmentation, and species distribution of zooplankton (right). We are also collaborating with Rolf Vinebrooke from the University of Alberta, who is continuing some of the pioneering work of David Schindler in the Canadian Rockies. Rapid climate change and reductions in snow pack have been observed in the Canadian Rockies in recent years. Our collaborating group is exploring what impact these changes have on the large, highly pigmented crustaceans that are present in the highest elevation alpine lakes. One of the central concerns is that warming temperatures will allow the elevation of the treeline to increase, reducing the UV transparency of lakes due to increasing chromophoric dissolved organic matter (CDOM) concentrations, permitting the invasion of low elevation zooplankton species and endangering the more unique large, pigmented alpine zooplankton that have historically inhabited the lakes.
United States Rocky Mountain Lakes
Since 2001 we have been working in the Rocky Mountains of Montana and Wyoming in collaboration with Jasmine Saros at University of Maine to examine the interactive effects of two global change stressors: nitrogen deposition and climate change on a series of alpine and subalpine lakes. Such high elevation lakes are notoriously nutrient limited by N availability as well as P. Paleolimnological records indicate that there have been rapid changes in diatom community structure in these lakes in recent years. Our research is exploring the role of ecosystem subsidies in the form of N deposition and climate-mediated changes in dissolved organic matter (DOM) in regulating transparency to ultraviolet (UV) and photosynthetically active radiation (PAR). Nitrogen deposition and changes in transparency influence the vertical structure of the ecosystem by modifying the distribution of phytoplankton (deep chlorophyll maximum) and zooplankton grazers. We also are interested in the role of trophic forcing by zooplankton grazers versus abiotic forcing (temperature, UV and PAR transparency) in regulating the recently observed changes in diatom community structure.
In addition, routine data are collected each year to grow the UV and zooplankton databases for 8 core lakes in the Beartooth Mountains: Glacier, Emerald, Beauty, Kersey, Fossil, Island, Beartooth and Heart. These core lakes include both alpine and subalpine lakes, allowing our lab to ask questions about DOC source and quality in these two environments, factors that may be altered by climate change. In addition, large and small scale experiments have been carried out in these lakes to investigate the effects of photobleaching on DOC and zooplankton migration. In this system, we have also explored the usefulness of deuterium, a stable hydrogen isotope, in determining whether the source of organic material in alpine and subalpine lakes was terrestrially derived or produced within the lake.
Undergraduates have received funds from the Undergraduate Summer Scholar (USS) program through Miami University as well as the Research Experience for Undergraduates (REU) program through the National Science Foundation to conduct independent research projects at these Rocky Mountain field sites. Graduate students can use these lakes as part of a larger data set from lakes around the world, or focus their efforts on specific questions related to this region.
UV Transparency in Lake Tahoe
In 2006 we began monitoring UV transparency of Lake Tahoe, the largest subalpine lake in the U.S. While we have studied a variety of highly transparent systems around the world, Lake Tahoe is an interesting addition because of its size and depth (2nd deepest lake in U.S.). Recent work is focusing on the effects of climate teleconnections and wildfire on incident and underwater UV in Tahoe and nearby lakes, especially as related to the Rim Fire - the 2013 wildfire that was the third largest in California's history. Although overall Lake Tahoe is known for its highly transparent waters, transparency ranges from very high to very low around the periphery of the lake depending on the site. With the help of TERC researchers stationed at Lake Tahoe, we have been collecting monthly UV and temperature data since 2006 at two sites, Charles Goldman's Index Site and a mid-lake site. These routine measurements enable us to look at seasonal changes in transparency in this unique system as well as long-term changes resulting from human disturbance. In an effort to learn more about how the zooplankton community protects itself from this high UV environment, cultures of Leptodiaptomus tyrrelli are being maintained at Miami University for experimental use.
Invasion Ecology of Warmwater Fish in Lake Tahoe
Changes in UV transparency and warming trends in the surface waters of Lake Tahoe may be altering the susceptibility of this lake to invasion by warmwater fish species. Water transparency to visible light in Lake Tahoe has declined substantially since the 1960's and climate change is driving warming of the surface waters. This creates a potential refuge for invasive warmwater fish. There are no long-term records of changes in UV transparency in Lake Tahoe, but our data from the past few years demonstrate much stronger gradients in UV than in visible transparency along inshore-offshore, along-shore, as well as seasonal gradients. Warmwater fish have invaded many of the areas of the lake where lower transparency related to influx of DOM or nutrients have created a refuge from damaging UV radiation. In collaboration with researchers at University of Nevada-Reno, the Tahoe Environmental Research Center (TERC), and Jim Oris (also at Miami University), we investigated the effects of transparency on invasive species such as bluegill sunfish and largemouth bass.
IGERT: Environmental Aquatic Resource Sensing (2009-2013)
The National Science Foundation's IGERT (Integrated Graduate Education and Research Traineeship) program offered an interdisciplinary approach to train the scientists and engineers of tomorrow. In collaboration with Kent State University, the Global Change Limnology Laboratory IGERT focused on Environmental Aquatic Resource Sensing (EARS). Threats to aquatic systems are diverse and understanding these changes and their effects requires new tactics and technologies. To address these concerns, there is increasing use of automated sensors to collect environmental data creating an urgent need for training of a new cohort of environmental scientists. The EARS IGERT merged the use of advanced sensors and cyberinfrastructure with traditional aquatic environmental science disciplines to develop science professionals equipped for positions in academia, the government or the private sector. Students in the Global Change Limnology lab had the opportunity to become involved through sensor design and development, creation of sensor networks, and management/analysis of the resulting large, complex data sets as outlined in the other Current Research sections on the Global Change Limnology website.