Analysis of common water sampling techniques used to assess lake trophic state
Sat, 12/05/2015 - 00:21
Abstract: Volunteer lake management programs (VLMPs) across the country employ different surface water sampling techniques to establish long-term trends in nutrient availability and trophic state. The three most common techniques are a surface grab (SG), 2m integrated tube sampler (IT), and a discrete sampler, such as a Van Dorn or Kemmerer bottle deployed to a depth of 1.5m (DD). These various sampling techniques vary not only in depth, but also in cost and ease of use. The objectives of my study are to 1) determine if there is a statistical difference in chlorophyll-a (chl-a) and total phosphorus (TP) concentration obtained between the three different sampling techniques, 2) determine if the treatment effect (sampling device) varies over time, 3) determine which method has the least amount of variability, and 4) determine if sampling technique ultimately influences trophic state classification. The study was conducted on Upper St. Regis Lake, Paul Smiths, New York. I collected 10 samples from the lake using the three different techniques during the months of June – August, 2015. I found a significant difference in chlorophyll-a concentration between sampling techniques during June and July, and during the month of July for TP. The three sampling techniques yielded similar variability for chlorophyll-a but significantly different variability for TP. Ultimately, the trophic status rating for Upper St. Regis was not effected by sampling technique. My study suggests that VLMP should utilize a SG or IT rather than a costly DD sampler.
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Major: Environmental Sciences
Changes in aquatic communities resulting from interactions between climate change and invasive aquatic plants in the Adirondacks.
Thu, 02/09/2012 - 11:26
Abstract: Global climate change can act synergistically with invasive species leading to shifts in ecosystem structure and function. We assessed how a rise in water temperature influenced the potential competitive advantage of an invasive aquatic plant, Eurasian watermilfoil, (Myriophyllum spicatum) over a co-occurring native species northern watermilfoil (M. sibiricum). We also examined the interrelationship between water temperature, watermilfoil, and the aquatic ecosystem including periphyton growth and zooplankton abundance. The study was conducted using replicated mesocosms (3785-liter), with water heaters used to provide a range of temperatures. We found that increasing water temperature promoted the likely competitive advantage of the invasive species, M. spicatum: Survival of M. sibiricum plants was lower than that of M. spicatum across all temperature treatments with a mean survival rate of 24% and 96% respectively. M. sibiricum also showed significantly slower rates of plant growth (mean growth of 3.3 cm compared to 7.6 cm for M. spicatum) and reduced vigor compared to M. spicatum, with an average of less than half the number of growing meristems. Zooplankton densities averaged over 20 times higher in mesocosms with M. sibiricum compared to those with the invasive M. spicatum. Periphyton biomass was best explained by water temperature with an increase in growth in warmer water. Our study confirms that in the face of global climate change, the invasive M. spicatum will continue to exert dominance over its native counterpart. Our results also provide compelling evidence that the combined effects of climate change and invasive aquatic plants can dramatically alter aquatic ecosystems.
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Major: Environmental Sciences, Fisheries and Wildlife Science, Forestry, Natural Resources Management and Policy
File Attachments: Climate change and milfoil draft FINAL.doc