Paleolimnology Report

this page last updated on 13 Feb 2019

 

Two paleolimnology studies have been undertaken on Chandos Lake.

The first, is a 3-core top/bottom analysis for 2 sites in South Bay, and one site in Gilmour Bay. The field work was undertaken in 2014, and the report by Kelly Hollingshead was published on this site in 2017.  It can be found here.

The second study, undertaken in 2017/18 by Dr Katrina Moser of Western University for the CLPOA is a more comprehensive analysis of the 2014 Gilmour Bay core.      It has just been completed (February 2019) and can be found here. (with permission).

The purpose of these studies is to attempt to determine how the water quality of our lake has changed over time. The sediment is laid down year over year, and as conditions change, so do the diatoms that can be found in the sediment.  Assemblages of diatoms are proxies for various lake environments and conditions, and so determining the changes in diatoms can tell us something about the lake. Other data were collected  and analyzed as well, and can be found in the reports.

A brief report on the first study was given at the NORKLA meeting on June 24,2017 in Apsley. A summary of that presentation can be found here.

As discussed in the above Norkla presentation,  there is a suspicion of  climate change affecting the diatom assemblages.  If you  are interested in a  serious scientific look at this possibility, please see:  ruhlandetal2015

What follows is a bit of a backgrounder on the first paleo study at Chandos.

 

Diatom Stephanodiscus.niagarae

stephanodiscus-niagarae-2-v1

Diatoms are a group of photosynthesizing algae, both planktonic and benthic.  They have a siliceous cell wall called a frustule.  As these algae die, their frustules collect in the sediment.  Because algae are highly sensitive to their lake environment, changes in algae populations can be indicators of changes in lake conditions.

dsc_0385king-christine-kelly-penny-blake

our intrepid coring team with the first core – August, 2014.

Chandos Lake was formed after the last ice age, some 10,000 years ago.  In spite of what we might like to think, the landscape is in constant change, albeit, on a scale much longer than humans relate to.  However, there have been several anthropogenic (ie created by humans) events in recent times that could precipitate rapid change in the lake status:  settlement of the surrounding area for mining, logging and farming (affects runoff); the arrival of cottagers; and acid rain.  (and now, climate change)

And so we wonder what the effect of these man-made events has been on the lake.

Limnology is the science concerned with the characteristics of inland waters: their chemical, physical, biological, and geographical attributes.  In the case of Chandos, we are particularly interested in the clarity, chemistry, dissolved oxygen, phosphorous levels, and things like that.

Paleolimnology is the science concerned with inferring the past conditions of a body of water from studying its sediments, obtained by extracting cores from the bottom.  Each year another level of sediment is laid down, typically 2-3 mm or so.  Thus a core sample 60 cm long would hopefully cover the last 200 years, which covers the  main anthropogenic period that we are interested in.  Now a sediment core can be analyzed in a number of  different ways.  We are limiting our analysis to looking at how the diatom populations have changed.  A comparison of the diatoms in the top layer to the bottom layer might indicate what kinds of changes the lake has experienced.

Some studies actually date the core by slicing it into many segments and testing for the radioactive element  Pb-210 in each segment.  See:  Pb-210 primer(This is one of the main differences between the first and second study – The second one dated the Gilmour core).  This would allow segments in the core to be chronologically dated and might help determine the cause of whatever change is being observed.  We are not performing Pb-210 dating (ie in the first study), because we are just interested in the overall change, and thus assume the bottom of the core is old enough to predate anthropogenic effects, and that the top represents the present condition.

In August of 2014, we undertook investigations on Chandos lake, at three sampling sites:

  • Site 1 in the 100 foot deep trough just east of Belle Island in South Bay. (44.794°N, 77.965°W)
  • Site 2 in the deepest “hole” in Gilmour Bay at about 70’. (44.788°N, 77.953°W)
  • Site3 in the deepest part of South Bay, at about 110’.(44.786°N, 77.985°W)

The South Bay sites were selected as being of special interest to the author, with the Gilmour Bay site also being chosen because of the anoxic (no dissolved oxygen at depth) conditions occurring there.  The Main Basin and West Bay most likely would yield results similar to South Bay, but certainty will have to await the interest and resources of others.

The investigations included:

  1. Secchi depths (to measure water clarity as part of the determination of trophic status)
  2. Dissolved Oxygen(DO); Temperature; pH; Oxidation Reduction Potential (ORP); Specific Conductivity – all as a function of depth
  3. Chemistry of the surface waters
  4. Chemistry of the bottom waters
  5. Core sampling for diatom investigation, from the top and bottom sections of each core.