Using core samples from lakes to understand past ecological changes and the impacts of land use: manoomin project

Transcription

1 Using core samples from lakes to understand past ecological changes and the impacts of land use: manoomin project Amy Myrbo LacCore/Limnological Research Center University of Minnesota, Minneapolis

2 Lakes as recorders of their environments

3 Lakes as recorders of their environments core Younger (newer) mud at top Older mud at bottom

4 Logo by Charlie Nahganub manoomin: the past, present, and future of wild rice lakes on the Fond du Lac Reservation NSF-funded collaboration Fond du Lac Resource Management Division, U of MN, FDL Tribal and Community College Five years ( 09-14) Students do research projects Long-term history of wild rice lakes

5 Photo courtesy of Thomas Howes

6 Slide about manoomin #2

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9 Coring at winter science camps Lake Teams

10 Initial core description (ICD) Multisensor logger Core splitter Digital core imager Description of lithology and sedimentary components

11 Summer intern projects Work closely with science mentors 1 week college-age students in small groups 3 days younger students in Lake Teams

12 Core composition (LOI)

13 Pollen What trees made up the forest around the lakes in the past? Pine Ragweed Oak Grass Birch

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15 Wild rice and other plant remains fossil What other plants were living in the lake when wild rice was (or was not) present? Aquatic moss fresh Najas

16 Phytoliths silica particles from plants Where was wild rice present in each lake at different times in history?

17 Diatoms algae with a silica cell wall amyrbo@umn.edu What were the environmental conditions (nutrient levels, ph, lake depth) at times in the past?

18 Magnetics How is landscape change (erosion, lake level) recorded in lake sediments?

19 Ostracodes microscopic crustaceans Photos by Andy Leaf Where was groundwater flowing into the lakes in the past? What was the water chemistry like?

20 Ostracodes microscopic crustaceans Photos by Andy Leaf Where was groundwater flowing into the lakes in the past? What was the water chemistry like?

21 XRF (x-ray fluorescence elemental analysis) and x-radiography How do density and chemical changes reflect landscape and lake changes?

22 XRF (x-ray fluorescence elemental analysis) and x-radiography How do density and chemical changes reflect landscape and lake changes? Si:Ti~ BSi Spikes in biogenic silica (diatom) abundance Ti+K+Ca~clay

23 Other initial results Dead Fish Lake currently has high nutrient levels; abundance of phosphorus mineral vivianite throughout >10m core is evidence of persistent high nutrient levels in the past Source? Local geology, relatively large watershed, waterfowl?

24 Why do ecology from the mud? Longer time scales Research studies (years) Instrumental records (decades) Oral and written histories (centuries) Mud (millennia) Possibility of 5-10 year resolution (In special cases, annual resolution)

25 Looking in all directions The past is the key to the present (and the future) Conservation paleoecology: what are the baseline conditions of the lake? Climate change in the past and potential for future ecological responses to climate change

26 National Lacustrine Core Facility Department of Geology and Geophysics, University of Minnesota-Minneapolis Assistant Curator Kristina Brady Lab Manager Amy Myrbo Curator Anders Noren

27 Figure by Billy D Andrea

28 Other applications of lake core analysis for understanding past conditions Nutrient conditions, ph Sedimentation rates, lake depth Plant communities & ecology Forest composition Erosion Water chemistry Drought Fire frequency Climate

29 Cost of a project Field work collecting cores Initial processing Dating/aging/chronology Analyses

30 Field work collecting cores Pro coring person ($150 per day) and your team Travel, meals, and lodging Equipment rental ($ per week or buy coring equipment ($ ) Supplies ($10-20 per meter of core) Core transport to our lab (by vehicle or FedEx)

31 Initial processing Multisensor logger $15/meter Core splitter Data and metadata management Curation Digital core imager Description of lithology and sedimentary components

32 CORE Dating and chronology How long is long? How long a record do you need? Natural state (baseline) vs. current conditions Lead-210 dating About 150 years $2500/core gets you all dates in last 150 yr Radiocarbon dating Up to 40,000 years $500/sample gets you one date

33 $2500 CORE Dating and chronology How long is long? How long a record do you need? Natural state (baseline) vs. current conditions Lead-210 dating About 150 years $2500/core gets you all dates in last 150 yr Radiocarbon dating Up to 40,000 years $500/sample gets you one date

34 $2500 CORE Dating and chronology How long is long? How long a record do you need? Natural state (baseline) vs. current conditions Lead-210 dating About 150 years $2500/core gets you all dates in last 150 yr Radiocarbon dating Up to 40,000 years $500/sample gets you one date

35 $1500 CORE Dating and chronology How long is long? How long a record do you need? Natural state (baseline) vs. current conditions Lead-210 dating About 150 years $2500/core gets you all dates in last 150 yr Radiocarbon dating Up to 40,000 years $500/sample gets you one date ,000 years ago- 5,000 years ago- 10,000 years ago-

36 CORE Dating and chronology How long is long? How long a record do you need? Natural state (baseline) vs. current conditions Lead-210 dating About 150 years $2500/core gets you all dates in last 150 yr Radiocarbon dating Up to 40,000 years $500/sample gets you one date ,000 years ago- 5,000 years ago- 10,000 years ago-

37 Specialized analyses Sediment composition % organic matter vs. mineral Diatoms Past ph, nutrient conditions, habitats Aquatic & terrestrial plant fossils Nutrient levels Pollutants, heavy metals Sediment chemistry Stable isotopes

38 Suggestions Ask specific questions Choose lakes carefully Chronology/dating is absolutely essential Student research opportunities: placebased learning Community interest and involvement Talk to us about your needs!

39 Miigwech!