Anthropogenic and climatic influences over the past three centuries on characteristics of an Adirondack lake, Eastern North America. Issue 2 (19th June 2013)

• Record Type: Journal Article
• Authors: Kanfoush, Sharon L.
• Is Part Of: Lakes & reservoirs. Volume 18:Issue 2(2013)
• Page Start: 99
• Page End: 113
• Publication Date: 2013-06-19
• Subjects: climate change -- diatoms -- grain size -- lake sediment; Lakes -- Periodicals; Reservoirs -- Periodicals; Gestion de l'environnement; Gestion écologique; Lac; Lac de barrage; Périodique électronique (Descripteur de forme); Ressource Internet (Descripteur de forme); 333.9163
• DOI: 10.1111/lre.12023
• Languages: English
• ISSNs: 1320-5331

Abstract

Abstract: Fourth Lake is a drainage lake at 43°N, 74°W, from which a 37‐cm long mud‐water interface core was recovered. 210 Pb dating indicates the core spans ≈340 years, from the Little Ice Age through modern global warming. Diatom accumulation responds to anthropogenic watershed disturbances, declining slightly up‐core until a peak in the late‐1800s attributable to sediment and nutrient influx from logging and enlargement of the outlet dam. A dramatic decrease occurs ≈1900 as logging and lake filling ceased, and a smaller peak ≈1960 accompanies residential development. Similar changes occur in organic carbon accumulation, which ranges from 0.0038–0.024 mg cm −2 year −1, with generally decreasing values up‐core, punctuated by maximum values in the late‐1800s. Expressing diatoms as concentration, however, reveals a doubling up‐core that positively correlates with changes extending beyond the watershed, including Northern Hemisphere temperature, atmospheric CO2 concentration and solar irradiance ( R = 0.627, 0.675 and 0.400, respectively). A >50% increase in % organic carbon, from 3.8% to 5.9%, also positively correlates with these larger‐scale environmental conditions ( R = 0.828, 0.830 and 0.832), while negative correlations with the extrabasinal records are exhibited by magnetic susceptibility ( R = −0.654, −0.496, and −0.660) and clay ( R = −0.770, −0.762, and −0.737). These changes are consistent with decreased sediment influx and reduced dilution of biogenous sedimentary components. In contrast to total diatoms, the accumulation of planktonic genus Asterionella displays a long‐term increase up‐core. Potential explanations include increasing duration of the ice‐free season or a shift in the timing of the spring bloom and a mismatch with abundance of predator(s). Asterionella also increases as a percentage of total diatoms, being positively correlated with extrabasinal conditions ( R = 0.827, 0.774 and 0.674). This change occurs at the expense of many benthic genera and, over the past century, at the expense of tychoplanktonic genus, Aulacosiera . Heavily silicified, Aulacosiera requires strong mixing to remain within the epilimnion. Thus, its decline might result from increasing stratification caused by warming.