Landscape Influence on the Browning of a Lake Watershed in the Adirondack Region of New York, USA

Abstract

Watershed recovery from long-term acidification in the northeastern U.S. has been characterized by an increase in the influx of dissolved organic matter (DOM) into surface waters. Increases in carbon quantity and shifts to more aromatic and “colored” OM has impacted downstream lakes by altering thermal stratification, nutrient cycling and food web dynamics. Here, we used fluorescence spectroscopy coupled with parallel factor analysis (PARAFAC) to model predominant carbon quality fractions and their seasonal changes within surface waters along landscape positions of Arbutus Lake watershed in the Adirondack region of NY, USA. All DOM components were terrestrial in origin, however their relative fractions varied throughout the watershed. DOM in headwater streams contained high fractions of recalcitrant (~43%) and microbial reprocessed humic-like OM (~33%), sourced from upland forest soils. Wetlands above the lake inlet contributed higher fractions of high molecular weight, plant-like organic matter (~30%), increasing dissolved organic carbon (DOC) concentrations observed at the lake inlet (492.5 mg L−1). At the lake outlet, these terrestrial fractions decreased significantly during summer months leading to a subsequent increase in reprocessed OM likely through increased microbial metabolism and photolysis. Comparisons of specific ultraviolet absorbance between this study and previous studies at Arbutus Lake show that OM draining upland streams (3.1 L·mg C−1 m−1) and wetland (4.1 L·mg C−1 m−1) is now more aromatic and thus more highly colored than conditions a decade ago. These findings provide insight into the emerging role that watersheds recovering from acidification play on downstream water quality.

Dissolved Organic Matter Dynamics in Reference and Calcium Silicate‐Treated Watersheds at Hubbard Brook Experimental Forest, NH, USA

“…These patterns are consistent with shallow groundwater chemistry where eluvial soil forming processes dominate (Bailey et al, 2019). Additionally, these results were mirrored in stream water, albeit not surprising, given previous work connecting surface water chemistry to surrounding soil type in stream catchments (LoRusso et al, 2020;Zimmer et al, 2013). Repeated wetting and drying cycles in these soils has also been shown to drive OM mobilization and mineralization (Patel et al, 2021), through shifts toward aluminum dominated interactions (Possinger et al, 2020), as well as through the connection of connect labile carbon to microbial communities within soil pore systems leading to further processing (Bailey et al, 2017;Kravchenko et al, 2021).…”

Browning of boreal lakes: Do public perceptions and governance align with the biological foundations?

“…Browning affects lakes in their entirety, but along watercourses the impacts of external Fe and DOC are attenuated downstream due to self‐purification processes, including dilution, filtering by organisms, chemical transformation, the degradation of substances, and sedimentation (Kalinkina et al, 2020). Photobleaching, degradation of DOM by sunlight, is largely limited to summer (Lorusso et al, 2020; Pace & Cole, 2002) and can have an important priming effect on further microbial degradation of DOM. Humic water results in a strong thermal stratification of water layers during summer due to the increased absorption of solar radiance in humic versus clear lakes (Mazumder & Taylor, 1994; Pilla et al, 2018).…”

Recovery Processes of Acidic Soils Experiencing Decreased Acidic Deposition

“…In LoRusso et al [14], sources and processing of dissolved organic matter (DOM) are investigated in a watershed-lake system. Like many other surface waters in regions where acidic deposition is decreasing, dissolved organic carbon concentrations have been increasing in the study lake, largely through changes in soil and wetland-related processes.…”