Understanding Streams/Waterways

During the summer of 2016, the ongoing New England drought reduced flows

Jacob
Hosen
Kroon G01
2:45pm
During the summer of 2016, the ongoing New England drought reduced flows in many streams and rivers to their lowest levels in more than 50 years. Drought conditions cause a myriad of environmental changes in rivers and streams including increased temperature, decreased oxygen levels, and increased concentration of many solutes due to evaporation. Surprisingly, how extremely low flows impact ecosystem function in river networks is not well understood. To address this knowledge gap, we deployed a network of in situ water quality sondes to measure ecosystem metabolism. Ecosystem metabolism is a measure of oxygen consumption by heterotrophic metabolism and gross primary production is oxygen produced by autotrophic processes within a river reach. We hypothesized that the extreme drought conditions would have a negative impact on aquatic biota in streams and rivers, resulting in decreased respiration and primary production rates. Data were collected from May 2015 through January 2017 using probes deployed in channels across the Connecticut River watershed including sites in the Farmington River (Connecticut; n=8) and Passumpsic River (Vermont; n=8) watersheds. Contrary to our hypothesis, in smaller streams and rivers metabolic rates did not increase or decrease significantly in response to drought. By contrast, in the main stem of the Connecticut River both primary production and respiration rates increased greatly as drought conditions deepened. Increased residence time in the Connecticut River during low-flow conditions allowed a robust planktonic microbial community to develop. This microbial community was responsible for high primary production rates that produced large amounts of organic carbon. This organic carbon was then released to the river environment, stimulating high levels of microbial heterotrophy. Metabolic rates in the Connecticut River main stem were generally elevated, but also highly variable, indicating that extreme drought conditions can drive ecosystem instability in large river systems.

Over the past two decades there has been a growing concern

Max
Lambert
Kroon G01
2:45pm
Over the past two decades there has been a growing concern about chemicals that interfere with sex hormone pathways and cause sexual deformities. These contaminants can include diverse chemicals like pesticides, pharmaceuticals such as oral contraceptives, and even chemicals produced by living plants. Wild frog populations in Connecticut suburban ponds regularly show sexual deformities where male testes contain ovary-like characteristics such as egg cells. Furthermore, offspring frog sex ratios in suburban frog populations are feminized relative to populations in undeveloped, forested landscapes. Both sexual deformities and skewed sex ratios suggest that frogs in the suburbs may be sex reversing, where their genetic sex is opposite of their expressed sex. Furthermore, suburban frog ponds are contaminated by a diversity of feminizing contaminants that are entirely absent from forested frog ponds. Using novel genetic markers of sex, I have begun understanding whether sex reversal in occurring in wild frog populations and whether it is a relatively natural process or whether it is caused by suburban pollution. Suburban land use is one of the fastest growing forms of land cover in the United States. Sex reversal caused by reproductive contaminants from suburban neighborhoods may pose a widespread threat to the viability of aquatic wildlife populations.

Closing the Water Budget in an Experimental Urban Watershed

Leana
Weissberg
Kroon G01
2:45pm
Closing the Water Budget in an Experimental Urban Watershed: A Comparative Assessment of Methods for Measuring Evapotranspiration. Three methods for the measurement of evapotranspiration (ET) were tested for quantitative agreement and ease of implementation at the Yale Experimental Watershed (YEW) on the Yale University campus. This methods analysis had two goals: first, it aimed to 'close' the water budget at the YEW and second, to recommend to urban resource managers a relatively easy and cost-effective means of measuring ET. Though rarely studied or quantified in urban environments, ET is a major term in these, and indeed most, water budgets. Accurately quantifying this term in cities could incentivize land use that either reduces runoff or increases storage on the landscape, depending on the requirements of the climate in question. Measurement of ET at the YEW took place over the course of the 2016 growing season (July ' October, 2016). Tested methods included a micrometeorological heat budget (Penman FAO 24 model), pan evaporation, and soil moisture profiles. Quantitative agreement was assessed using simple linear regression models, indicating the strongest relationship between the micrometeorological heat budget and pan evaporation. Furthermore, the micrometeorological heat budget was the most cost-effective and feasible method of those tested. ET was also estimated by difference by constructing a water budget utilizing data on surface and subsurface flows.

Title: Examining the Role of the Connecticut River Watershed

Rachel
Lowenthal
Kroon G01
2:45pm
Title: Examining the Role of the Connecticut River Watershed in Nutrient Loading to Long Island Sound. Abstract: The relationship between nutrient loading and summer hypoxic conditions in Long Island Sound is highly studied. The Connecticut River contributes 70% of the fresh water to Long Island Sound, carrying a significant amount of total nutrients. The goal of this study was to capture nutrient export from tributaries throughout the Connecticut River watershed under a variety of flow regimes, targeting unique watershed sizes with varying land cover. The approach allowed us to constrain the relative importance of different regions across the watershed, and assess their nutrient contribution to Long Island Sound. Over two years, twenty subbasins across the watershed from Vermont and New Hampshire to Massachusetts and Connecticut were sampled over a range of seasons and flow conditions for total nitrogen (TN), total dissolved nitrogen (TDN), total phosphorus (TP), and total dissolved phosphorus (TDP). Both TN and TDN yields follow a tight linear relationship with discharge across most of the subbasins. For TP and TDP, a strong positive linear correlation was observed between the area of developed land in each watershed and that watershed's TDP yield and discharge relationship. This finding highlighted the role of urban and developed lands along the Connecticut River and their importance contributing nutrients to Long Island Sound. We also quantified nitrogen and phosphorus fluxes from tributaries in the urban areas flanking the mainstem of the river from Springfield to Hartford. The extensive sampling of the Connecticut watershed's tributaries, in addition to the analysis of water quality records provided by the United States Geological Survey across the watershed's urban areas, will help to further inform discussions about the role of the Connecticut River watershed in the water quality dynamics of Long Island Sound.

Light limits primary production rates in many streams

Elizabeth
Creech
Kroon G01
2:45pm
Light limits primary production rates in many streams, yet there are knowledge gaps in our ability to model stream surface light availability. One reason for this is the large variability among streams, with streams of different orders having different amounts of light capable of traveling through riparian vegetation to the actual stream surface. Both stream order and riparian vegetation type largely affect stream surface light availability. The goal of this research was to model stream surface light availability across first through fifth order streams and within four riparian land cover types: urban, agricultural, early-growth forest, and mature-growth forest. Stream surface light data was collected across 80 stream sites during the summer of 2016 in the Farmington River Watershed (southern New England) and the Passumpsic River Watershed (northern New England). A subset of these sites were sampled for leaf-off conditions during the winter and early spring of 2017. Two devices were used for collecting canopy light data: a Solar Pathfinder'a tool generally used in the renewable energy field'and a less novel Kodak PixPro SP360 fisheye lens. Solar Pathfinder images were analyzed using Solar Pathfinder Assistant Base Software, and Kodak PixPro SP360 images were analyzed using Gap Light Analyzer software. Findings suggest a predictable relationship between stream order, riparian land cover type, and surface light availability. Though user-friendly, the Solar Pathfinder did not yield consistently reproducible results. This was particularly true for first and second order streams with heavy canopy cover.