Paleolimnology in Roosevelt: Learning from the Past Proposal - - PowerPoint PPT Presentation

Paleolimnology in Roosevelt: Learning from the Past

Proposal Submitted to State of Arizona Water, Economic Development and Sustainability Fund

• Principal Investigators:

– Owen K. Davis, UA – Susan Fitch, ADEQ – Paul Gremillion, NAU – Vicente Lopes, UA – Peter Van Metre, USGS – David Walker, UA

Problem Statement

• In waters without historical water

quality data, it is difficult to predict trends in trophic state.

• It is impossible to quantify detrimental

effects of land-use activities or natural disturbances unless data has been collected prior to each disturbance or activity.

Paleolimnology as a Tool

• Paleolimnological techniques are often

used to assess water quality trends in lakes over time.

• Incorporated in reservoir sediments is a

record of the organisms that lived in and around the lake, as well as proxy data related to processes occurring in the lake.

• Previous studies have examined the

accumulation of watershed-derived pollutants in sediment cores of reservoirs with rapidly urbanizing watersheds.

• These studies often fail to address the

consequences of these pollutants on aquatic biota or overall ecosystem processes.

Specifically we propose to;

• We propose to use paleolimnological

techniques to obtain, date, and analyze sediment cores from Roosevelt.

• These cores will then be age dated

using Pb210 and/or Cs137 radionuclides.

Objectives

• To quantify long-term water quality

trends in Roosevelt and the Salt River watershed

• Determine how these watershed

determinants define water quality within the reservoir

• How aquatic biota have responded to

these water quality changes

Objectives (cont.)

• Determine watershed vegetation

changes over time and how this has affected, and been affected by, fire cycle frequency and intensity.

• Determine the effect of

anthropogenic activities in the watershed on water quality in the reservoir.

• The focus of this work will be pre-

impoundment, however, local geography indicates a pre- impoundment playa or wetland may have existed (i.e., “Tonto Basin”).

• We anticipate the cores being long

enough to capture pre-impoundment conditions.

Analytes and the reason for their analysis.

• Fossilized pollen grains (palynology)

– To determine watershed vegetative changes which will vary due to climate, wildfire regimen, or human removal. – Decreases in vegetation can reduce transpiration and soil moisture storage which may increase runoff and material transported to the reservoir. – The rate of this transport, in turn, can strongly influence biogeochemical processes within the reservoir.

• Fossilized diatom frustules

– Siliceous diatom valves are well-preserved in lake sediments and are a direct reflection of environmental conditions at the time of deposition. – Diatoms contain many species with relatively limited ecological tolerances. – Short life cycles mean they respond rapidly to environmental change. – Have been used to infer changes in pH, salinity, temperature, and nutrient availability.

• Fossilized chironomid (midge fly) head

capsules

– Excellent indicators of water quality condition especially of hypolimnetic anoxia. – Chironomids highly sclerotized head capsules are usually well-preserved in sediments. – Chironomid taxa exhibit marked differences in individual responses to water quality degradation leading to anoxia such as nutrient accumulation.

• Charcoal Analysis

– To determine past fire cycle, frequency, and intensity. – The consequences of fire on Roosevelt water chemistry is a timely and important issue considering current drought conditions.

• Nutrients and heavy metals

– We will obtain samples at select locations of the core for nutrients related to eutrophication and metals associated with wither anthropogenic activities or atmospheric input.

Questions?