Abstract Title: Abstract 1: Changes in Chromophoric Dissolved Organic Mater in the Blackstone River Watershed: Drivers and Implications for Climate Change. Abstract 2: Bacterial Monitoring of Tributaries to Lake Quinsigamond.

Abstract Submitted to: HYDROLOGY

Abstract Text:

Abstract 1:
Land use change and associated pollution, along with climate change,
threaten the health of the Blackstone River Watershed (BRW) in
Worcester County, Massachusetts. While water quality metrics are
measured in the BRW, minimal biogeochemical data are available,
making it difficult to assess climate change impacts. Chromophoric
dissolved organic matter (CDOM) can be used as a proxy for dissolved
organic matter (DOM) concentration, reactivity, and quality, as well as
dissolved organic carbon (DOC) concentration and source. Thus, CDOM
measurements over time can demonstrate seasonal and interannual
organic matter profile changes and uncover carbon cycling influences.
This study investigates CDOM absorbance and metrics in July-November
2022 and March-November 2023, aiming to determine drivers of CDOM
variability in the BRW and their implications for future climate change.
CDOM sampling occurred weekly at eight sites, including two mainstems
and six tributaries, across an urbanization gradient. Sampling for
chlorophyll-a was added in 2023 to provide further insights into carbon
sources. CDOM samples were filtered on-site, analyzed on a UV-visible
spectrophotometer, and post-processed to determine absorbance and
associated metrics. Chlorophyll-a samples were concurrently sampled and
analyzed on a fluorometer. We also analyzed satellite-derived normalized
difference vegetation index (NDVI) data, as well as drought, temperature,
precipitation, and discharge data, to identify drivers of seasonal change
and their relationship to CDOM shifts. Findings revealed that river
discharge is the strongest driver of CDOM variability. In particular, we
found a statistically significant positive relationship between discharge
and CDOM absorbance, with peaks in discharge corresponding to peaks in
absorbance at all sampling sites. With the addition of 2023 data, we aim to
solidify this relationship and its applications to past and present climate
change-related hydrological scenarios.

Abstract 2:
Located in Worcester County, Massachusetts, Lake Quinsigamond is a historically recreational body of water bordered by Worcester and Shrewsbury. In summer months where aquatic recreation is perhaps most in demand, however, inflows from tributaries present challenges with water quality due to stormwater runoff in the largely urbanized bordering towns, as well as other point and nonpoint source pollution, resulting in beach closures and a lack of access to aquatic recreation for many people, some of whom have few other options available. The Lake Quinsigamond Watershed Association aims to bring attention to the issue. Since its commencement in 2020, this monitoring project has utilized bi-weekly sampling from late spring to early fall at several strategic locations in and around the lake in order to monitor E. Coli levels in the watershed, with minor annual changes to site locations based on new information concerning upstream conditions. Specifically, sites are selected based on geography, proximity to storm water outflow, tributary-transport status, and historical bacterial impairments and events. Samples are analyzed by an external laboratory, and results are compared with Massachusetts Surface Water Quality Standards and shared with other local organizations that perform bacteria sampling, including The Massachusetts Department of Environmental Protection, the City of Worcester, the Town of Shrewsbury, and the Lake Quinsigamond Commission. Findings are included in the Integrated List of Waters, where if a water body is use impaired or is not expected to meet water quality standards following treatment, it will be assessed for total maximum daily load derivation and development of alternative restoration plans. In sum, this project aims to identify the past, current, and future drivers of water quality issues in and around Lake Quinsigamond, especially in terms of anthropogenic change to climate, land use, and infrastructure, in order to improve watershed health and usability.