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Waldo Lake LimnologyContact InformationMark Sytsma IntroductionWaldo Lake is one of the most pristine lakes in the United States. It is extraordinarily clear and light penetrates deep into the water column, giving Waldo Lake an exceptional blue color. The watershed is very small; therefore, the nutrient input into the lake is very low, keeping primary productivity low and thus maintaining clear water conditions. The dilute waters of Waldo Lake support a unique and potentially fragile ecosystem.
Human activity in and around the lake was cited as a potential cause of changes described by authors in the 2000 Lake and Reservoir Management issue. The volunteer collected data provided a basis for evaluating the condition of Waldo Lake, however, because sampling was contingent on individual resources and time it was somewhat haphazard. For the most part, the sampling was conducted as a monitoring program, with post hoc development of hypotheses. The publication of a 1995 report on Waldo Lake (Larson and Salinas), and the 2000 Lake and Reservoir Management issue focused attention on U.S. Forest Service management of Waldo Lake and stimulated funding of more in-depth study. In 2003, funded by the U.S. Forest Service, the Center for Lakes and Reservoirs at Portland State University began a research effort to develop a more complete understanding of the physical, chemical, and biological characteristics that drive the ecological processes of Waldo Lake. Modern limnology recognizes the importance of watershed processes as well as in-lake processes in lake ecosystem functioning. Therefore, the approach included consideration of watershed hydrology and forcing functions that determine hydrodynamics of the system as well physical and chemical factors that may be important in regulating primary production in the lake.
Tasks
Project Member Contact InformationSytsma, Mark, sytsmam@pdx.edu, 503-725-3833 Phytoplankton photoinhibition of photosynthesisThe purpose of this portion of the work was to look for possible sources of variability in primary productivity. We hypothesized that exposure to high light, and in particular UV light, could cause photo-inhibition over the day. This could be even more important at Waldo Lake because of its high altitude and exceptional clarity. We examined the variation in photosynthetic efficiency throughout the day and between days with different weather. It was hypothesized that calm and clear days would have a higher photoinhibition of surface productivity than windy and cloudy days. Photosynthetic efficiency was measured using Pulse Amplitude Modulate (PAM) Fluorometery. PAM Fluorometery measures the minimum and maximum fluorescence of a sample containing algae, before and after a saturating pulse of light. The light energy that is absorbed by an alga has three fates (figure below); 1) the energy can be utilized in photosynthesis, 2) it can be given off as heat or 3) it can be re-emitted as longer wave light (fluorescence).
After cells have been kept in the dark for about 5 minutes, all
of the photosynthetic electron transport chain carriers are oxidized,
and the light processed with a characteristic efficiency and low fluorescence.
After that same cell is exposed to a flash of saturating light, all
the electron transport chain carriers are reduced, and a large fraction
of any subsequent pulse of usable light is given off as fluorescence.
The difference between the pre-pulse fluorescence (F0) and post-pulse
fluorescence (FM) is the variable fluorescence (Fv). Fv/Fm has been
shown to be a reliable proxy measurement for the photosynthetic efficiency
of algae under many conditions. The PAM fluorometer was used to take
rapid measurements of Fv/Fm over a time course.
Time course of photosynthetic efficiency of surface water samples collected over the day as measured by Fv/Fm. Duplicate samples were taken at each time point. Each sample was subsampled twice and at least five readings taken on each subsample. The figure above shows the mean of the twenty readings at each time. The bars indicate two standard deviations. Feeding behavior of mixotrophic dinoflagelletesThe phytoplankton community of Waldo Lake is distinct due to low diversity, with the dinoflagellate Glenodinium neglectum comprising more than 75% of the total population. Studies of other lakes have shown mixotrophs, such as G. neglectum migrate vertically over a 24-hour period, moving to the surface to photosynthesize during the day, and feeding on bacteria at lower depths at night. During the summer of 2004, both mixotrophs and bacteria were collected and enumerated to investigate both the vertical migration of mixotrophs and the interaction between mixotrophs and bacteria. Water samples were collected at 7 depths over a 24-hour period and divided into 2 parts: 200-mL phytoplankton and 5-mL bacteria samples. Phytoplankton samples were filtered onto 0.45-µm filters, mounted on slides, and species of mixotrophs were counted. Bacteria samples were filtered onto black 0.2-µm filters, stained with DAPI, and bacteria were enumerated using epifluorescence microscopy.
Diurnal vertical migration of planktonDuring the summer of 2004 the daily vertical migration of phytoplankton and zooplankton was studied. Typically, mobile plankton vertically migrate to an optimal depth in the water column in response to changes in light intensity and available food supply. In Waldo Lake, high elevation and remarkable lake clarity leads to the penetration of UV-light deep into the water column. High UV-light intensity in the upper portion of the water column can be very stressful to organisms. Response to UV radiation is one proposed cause of vertical migration at Waldo Lake. To track zooplankton migration, bioacoustics were used in tandem with a traditional Schindler trap. An underwater fluorometer (SCUFA) was used as a semi-quantitative tool to assess chlorophyll-a concentrations in the water column. Standard chlorophyll filtration methods and phytoplankton collection were also used to quantify chlorophyll concentration and phytoplankton species present.
Phytoplankton primary productionA review of prior data collected by the U.S. Forest Service’s long-term monitoring efforts of Waldo Lake suggests measurement of 14-C fixation will require special care in Waldo Lake. Toxicitiy issues:
Water chemistry issues:
Hydrology and global climate changeObjectives
Variation with El Niño- Southern Oscillation (ENSO)
Summer Maximum temperature
Water balance for Waldo Lake
Thermal mixing eventsIn July 2003, forty temperature loggers were placed in eight depths at five locations in the lake (locations shown below). These will record data at one-hour intervals all winter and thirty-minute intervals all summer, recorded data will be downloaded twice a year. Additionally, air temperature, rainfall wind speed and direction data have been collected by a USFS weather station at the lake. Temperature data will be used in determining thermal stability, seasonal and daily mixing patterns and in the development of a hydrodynamic model. Additionally, monitoring lake mixing events is important in understanding the vertical distribution of phytoplankton in the water column.
Benthic MappingData collected in 2003 will be reanalyzed with Biosonics Inc.’s Bottom Typing software to produce a map of substrate types. The benthos of Waldo Lake is interesting and unique in that there are large communities of stromatolites occupying waters 5 to 40-m deep and underwater bryophytes in deeps greater than 50-m. By collecting sediment samples using a gravity corer and an Eckman dredge in the fall of 2004, we will be able to ground-truth software inferences from the data collected during the summer of 2003. Water quality and hydrodynamic modeling
CE-QUAL-W2 Model http://www.ce.pdx.edu/w2/?projects_waldo_lake.html Portland State University, Water Quality Research Group is the center of the development of this multi-dimensional water quality and hydrodynamic model Why is Modeling Necessary?
Ecosystem Model’s Relationship to Project Elements
What is the Model? The model incorporates data to create a mathematical representation of the Waldo Lake Ecosystem. DATA UTILIZED:
What Management Questions Can Be Answered? Typical Management questions:
Model predictive ability:
What is the model development process?
Completed DocumentsThe following are documents currently available in Adobe pdf format:
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