T102 Lacustrine Systems across Space and Time I

Monday, 23 October 2017
8:00 AM - 12:00 PM
Room 307/308

MECHANISMS FOR INCREASED PHOSPHORUS INPUTS AND CONSEQUENT ENHANCED LACUSTRINE PRODUCTIVITY DURING THE YOUNGER DRYAS CHRONOZONE IN THE LOCH, ROCKY MOUNTAIN NATIONAL PARK, COLORADO, USA

Paper number: T102-15
Program: Technical Sessions
Time: 11:30 AM – 11:45 AM

Authors

Abstract

Despite being located in remote wilderness, The Loch, a lake located at the outlet of the glacial Loch Vale watershed (LVW) of Colorado, USA, is experiencing increases in algal biomass. The LVW is also undergoing cryospheric melting as climate warms. Increased atmospheric nitrogen deposition from anthropogenic activities in the region is partially responsible for the enhanced within-lake production. Dissolved phosphorus also facilitates production of algal biomass, and has been investigated both since the last glacial maximum from a sediment core recovered from The Loch, and in present-day stream water. Maximum adsorbed P5+ concentrations in the sediment core occurred during the Younger Dryas Chronozone (YDC) 13.2 to 11.1 ka when alpine glaciers advanced at higher elevations in response to climatic cooling. Consequent bedrock comminution facilitated dissolution of the phosphate minerals apatite [Ca5(PO4)3(Cl,F,OH)] and concomitantly monazite (REE(PO4)). Despite cooling, lacustrine organic matter content in the lake increased during the YDC, a trend not observed elsewhere in the Rocky Mountains of Colorado. The increase in organic matter is believed to reflect elevated PO43- concentrations in surface waters as the alpine glaciers advanced. Present-day increases in lacustrine biomass occur twice annually; during the winter when ice formation concentrates PO43- in lakes, and during the summer when the PO43- flux is at its maximum following seasonal freeze-thawing. Such processes would have been enhanced during the cooler YDC. This study also demonstrates that the most sensitive elemental paleoclimatic proxy data in lacustrine sediments originates from highly soluble, potentially radiation-damaged, minerals.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-305380

© Copyright 2017 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.