Chemical, biological, and trophic status of temperate lakes can be strongly influenced by the presence of late-glacial marine sediments

Abstract

Norton SA, Amirbahman A, Bacon L, Ewing HA, Novak M, Nurse A, Retelle M, Stager JC, Yates M. 2019. Chemical, biological, and trophic status of temperate lakes can be strongly influenced by the presence of late-glacial marine sediments. Lake Reserv Manage. 36:14–30.

Lake Auburn, Maine, is a water supply for 60,000 people. Unusual silt/clay sediment, >4 m thick, occurs 15 cm below gyttja in deep water cores. We characterized cores taken in 2015 and 2016 (57 and 425 cm long, respectively), from 35 m. We determined ¹³⁷Cs, ²¹⁰Pb, and ²⁰⁶P/²⁰⁴Pb ratios to establish chronology for the cores and to link them stratigraphically. At least 1.1 m of sediment has accumulated since European settlement due to watershed erosion from land clearance and disturbance from about 1750 onward. The increased lake level from dams established in 1851 and the 1950–1960s has caused shoreline erosion. Extraction of sediment with HCl, scanning electron microscopy, and energy-dispersive spectroscopy analyses confirmed the presence of apatite (Ca₅(PO₄)₃(OH)) for at least the upper 3.5 m of sediment. The apatite is soluble because of the circumneutral pH and relatively low Ca²⁺ concentrations. This modern sediment is derived from postglacial marine silt/clay sediment and represents a rarely considered internal source of P that predisposes the lake’s water column to higher total P, rendering it more susceptible to episodic eutrophication from stresses including higher temperatures, more frequent high-intensity weather phenomena, and longer ice-free periods with stronger and longer stratification. This previously unrecognized source of P must be considered in water quality management, including chemical mitigation such as aluminum addition, lake level manipulation, and watershed erosion control. Similar situations likely exist in other coastal lakes in postglacial terrain that was inundated during deglaciation, and in inland lakes receiving sediment directly during deglaciation.

Keywords:

• Apatite
• isotopes
• Lake Auburn
• Maine
• phosphorus cycling
• sediment

Acknowledgments

The Auburn Water and Sewer District, Auburn, ME, provided funding. M. J. Dillingham, former Director of the Water Quality Laboratory at Lake Auburn, was a constant source of encouragement, enabled access to water-quality data and water sampling, and provided important logistical support for coring in 2015 and 2016. Sidney Hazelton, Director of the Auburn ME Water District, conducted a records search for human impacts on Lake Auburn water level. Scott Williams, Executive Director of the Lake Stewards of Maine, provided boat support, and assisted in the field. Professor C. T. Hess and J. A. Cummings, Department of Physics and Astronomy, University of Maine, analyzed ²¹⁰Pb and ¹³⁷Cs for both cores. G. McDonald, University of Maine, processed the Psenner extractions for both cores. The extractions were analyzed in the Soils Analytical Laboratory, University of Maine, B. Hoskins, Director. Stable Pb isotope determinations were by M. Handley, Sawyer Environmental Chemistry Laboratory, University of Maine. P. Dostie and W. Hilton, Bates College, helped construct the coring platform, and assisted with the coring and sediment processing. Hilton performed the laboratory determinations of percent water and percent LOI. G. L. Jacobson, University of Maine, kindly helped in the reorganization of the article. Three reviewers patiently provided very important and detailed comments and questions, critical to improvement of the article.

Authors’ participation

All authors participated in the preparation of the article and data interpretation. Responsibilities for individual research components were: Amirbahman (coring, sediment processing, and Psenner extractions); Bacon (field and laboratory activities, providing staff for the 2015 and 2016 coring, and core sectioning); Ewing (coring and sediment processing); Norton (project coordination, coring, dating, Pb isotopes); Novak (stable S isotope analysis); Nurse (pollen analysis); Retelle (coring leader, sediment processing, seismic studies); Stager (diatom analysis); and Yates (EDS chemical mapping of sediment and SEM imaging).