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Background: Water resources are of fundamental importance to society, and are better managed by stakeholders who understand resource issues. Gaining such knowledge is a lifelong process best begun at an early age and best supported by educational approaches integrating across science, technology, engineering and mathematics (STEM). Research scientists can bring resource education to young audiences through children’s books and curricula that emphasise and integrate across STEM principals.Aims: To encourage empathy for the environment in younger students, researchers at the Niwot Ridge Long Term Ecological Research site have developed a children’s book series and methods for training teachers in water science education.Methods: Children’s books in the My Water series are paired with curricula, hands-on learning kits, teacher development training and dissemination of materials through school districts to further water science education.Results: Thousands of children and educators have received training thro...

Background: Nitrogen (N) deposition in the Front Range of the southern Rocky Mountains has been increasing for several decades, and has exceeded the critical load for several ecological metrics.Aims: Our objective was to predict potential future ecological changes in alpine zones in response to anthropogenic N deposition based on a review of research from Niwot Ridge, Colorado.Results: Empirical observations and experimental studies indicate that plant, algal and soil microbe species compositions are changing in response to N deposition, with nitrophilic species increasing in abundance. Biotic sequestration of N deposition is insufficient to compensate for greater nitrate production, leading to the potential for acidification and base cation loss.Conclusions: Changes in biotic composition in both terrestrial and aquatic ecosystems have important impacts on ecosystem functioning, including a lower capacity to take up and neutralise the acidifying effect of anthropogenic N, increasing phosphorus limitation ...

Background: Surface waters are the lowest points in the landscape, and therefore serve as excellent integrators and indicators of changes taking place in the surrounding terrestrial and atmospheric environment.Aims: Here we synthesise the findings of limnological studies conducted during the past 15 years in streams and lakes in the Green Lakes Valley, which is part of the Niwot Ridge Long Term Ecological Research (LTER) Site.Methods: The importance of these studies is discussed in the context of aquatic ecosystems as indicators, integrators, and regulators of environmental change. Specifically, investigations into climatic, hydrologic, and nutrient controls on present-day phytoplankton, and historical diatom, community composition in the alpine lake, Green Lake 4, are reviewed. In addition, studies of spatial and temporal patterns in dissolved organic matter (DOM) biogeochemistry and reactive transport modelling that have taken place in the Green Lakes Valley are highlighted.Results and conclusio...

Lakes may serve as sentinels for the impacts of changing climate in alpine areas. In the Rocky Mountain region, 2002 was a year with extremely low snowpack. We examined the summer phytoplankton community in Green Lake 4 for a 6-year period that included the summer of 2002. The phytoplankton community variation was examined in the context of the changes in physical and chemical properties of Green Lake 4. The physical changes associated with the 2002 drought included warmer surface water temperatures and greater hydraulic residence times; whereas the chemical changes included higher concentrations of acid neutralizing capacity (ANC) and major ions. During the summer of 2002 the phytoplankton community was dominated by Synedra sp. and Ankyra sp.; two previously rare species. The growth of Synedra sp. was sufficient to cause a decrease in silica concentrations, which has not been observed in other summers in the water quality monitoring record. The results of a redundancy analysis (RDA) indicated that concentrations of major ions and ANC were aligned with Synedra sp. and Ankyra sp. during the 2002 drought year. Following the 2002 drought year, Chrysococcus sp. and Chlorococcum sp., which became abundant, were aligned with nitrate in the RDA. These results indicate that the response of the phytoplankton community to the extreme drought was most strongly correlated with water quality changes that occurred, rather than temperature and hydraulic residence time. The dominant species in the post-drought phytoplankton community were found to be associated with nitrate, which is brought to the watershed by atmospheric deposition and may represent an anthropogenic driver of phytoplankton community composition.

Deposition of atmospheric nitrogen from urban and agricultural sources has caused surface water nitrate concentrations to increase in the Front Range of the Colorado Rocky Mountains. To investigate the effects of sustained increases in nitrate concentrations on phytoplankton dynamics in an alpine lake, we conducted nutrient enrichment experiments in mesocosms amended with nitrate, phosphate, and phosphate plus nitrate on four dates in July and August 2002. During this period, phytoplankton species composition shifted as diatoms decreased in abundance. Phytoplankton chlorophyll a increased in the phosphate and phosphate plus nitrate enrichments, but did not increase in the nitrate only enrichments. Analysis of the phytoplankton community using Principal Component Analysis showed that 34% of the variance was accounted for by the primary axis, which was associated with different time periods, and 21% of the variance was explained by the secondary axis, which was associated with treatments. The response to phosphorus enrichment was taxon-specific, and the two chlorophyte species which became more abundant, Chlamydomonas sp. and Scenedesmus sp., were strongly weighted on the secondary axis. These results indicate that the productivity of this phytoplankton community is phosphorus-limited throughout the summer. Therefore, additional inputs of nitrogen are not expected to directly alter the productivity of the phytoplankton community.

The hydrologic system of the coastal McMurdo Dry Valleys, Antarctica, is defined by snow accumulation, glacier melt, stream flow, and retention in closed-basin, ice-covered lakes. During the austral summers from 1993–1996 and 1999–2000 to 2002–2003, fresh snow, snow pits, glacier ice, stream water, and lake waters were sampled for the stable isotopes deuterium (D) and 18O in order to resolve sources of meltwater and the interactions among the various hydrologic reservoirs in the dry valleys. This data set provides a survey of the distribution of natural water isotope abundances within the well-defined dry valley hydrologic system in Taylor Valley, which extends 20 km inland from McMurdo Sound. The three major Taylor Valley lakes are not connected to one another hydrologically, and their levels are maintained by glacial meltwater inflow and perennial ice-cover sublimation. At the valley scale, glacial ice, snow, stream, and lake waters become more depleted in δD with increasing distance from McMur...

Active layer thickness was monitored along three ephemeral streams in the Taylor Dry Valley of Antarctica during the 1997–1998 summer season. Five to seven cross sections were established on each stream, and the thickness of the active layer was measured every 1.5 m over intervals ranging from 2 to 30 days. Active layer depths ranged from a minimum of 3 cm in early November to a maximum of 60 cm in late January, and the depth of the active layer increased rapidly as summer temperatures climbed above freezing. While there were significant differences in the thickness of the active layer among the three streams, the timing of rapid thaw was similar for all cross sections. Changes in active layer thickness were responsive to both daily and seasonal changes in air temperature. There was more rapid thaw under the areas with flowing water, suggesting a transfer of heat from meltwater into the underlying sediments, and some evidence of an insulating effect during cold periods. Active layer thickness was...

The McMurdo Dry Valleys Long‐Term Ecological Research (MCM‐LTER) site represents the highest‐latitude location of the 24 LTER sites supported by the U.S. National Science Foundation. Although the perennial ice‐covered lakes in the dry valleys have been investigated since IGY, detailed, ecosystem‐based studies have been conducted on these lakes since 1993 by LTER investigators. A review of recent findings on the biogeochemistry and food‐ chain dynamics of these lakes is summarized within. The lakes are much more complicated and more dynamic than previously thought. The importance of collecting long‐term data is imperative if an understanding of how these sensitive systems respond to climate change is to be gained.

In 1984 and 1985 seasonal changes in phytoplankton were studied in a system of three lakes in Loch Vale, Rocky Mountain National Park, Colorado. Three periods were evident: (1) A spring bloom, during snowmelt, of the planktonic diatom Asterionellaformosa, (2) a midsummer period of minimal algal abundance, and (3) a fall bloom of the blue-green alga Oscillatoria limnetica. Seasonal phytoplankton dynamics in these lakes are controlled partially by the rapid flushing rate during snowmelt and the transport of phytoplankton from the highest lake to the lower lakes by the stream, Icy Brook. During snowmelt, the A. formosa population in the most downstream lake has a net rate of increase of 0.34 d-l, which is calculated from the flushing rate and from the A. formosa abundance in the inflow from the upstream lake and in the downstream lake. Measurement of photosynthetic rates at different depths during the three periods confirmed the rapid growth of A. formosa during the spring. The decline in A. formosa after snowmelt may be related to grazing by developing zooplankton populations. The possible importance of the seasonal variations in nitrate concentrations were evaluated in situ enrichment experiments. For A. formosa and 0. limnetica populations, growth stimulation resulted from 8- or 16-micromolar amendments of calcium nitrate and sulfuric acid, but the reason for this stimulation could not be determined from these experiments.

In the Snake River, an acidic mountain stream in the Colorado Rocky Mountains, the concentration of dissolved iron is apparently unrelated to seasonal changes in hydrologic regime, which strongly influence the concentrations of most other dissolved constituents. Hourly sampling indicated that short-term fluctuations in iron chemistry occur, whereas the concentrations of most other dissolved constituents, including other trace metals, remain stable. During the day, greater concentrations of dissolved total and ferrous iron generally occurred during periods of full sunlight. Photoreduction of hydrous iron oxides, which are abundant in the fine sediment and as coatings on the rocks, may be responsible for these observations. Iron chemistry also varied at night, decreasing in dissolved total and ferrous iron until about midnight and increasing until dawn. Oxidation of ferrous iron, and several microbial processes, may contribute to these nighttime changes. In an on-site batch experiment using rocks and streamwater, an increase in dissolved total and ferrous iron occurred on exposure to sunlight, and ferrous oxidation occurred on return to darkness. Short-term fluctuations in iron chemistry are consistent with the lack of correlation between iron and other constituents in the long-term data, and illustrate the potential importance of complex in-stream processes in such stream systems.