“Sedimentary, my dear Watson.” Scientists using core clues to solve the mystery of Didymo

August 4, 2013

They say that history repeats itself. If that’s true, then a team of researchers from Queen’s University just may be the ones to solve the mystery behind a serious ecological problem threatening rivers in the Gaspé and in northern New Brunswick.

The problem: an invasive alga called Didymo. About six years ago anglers and scientists noticed its occurrence was on the rise inthe Matapédia-Restigouche watershed. “Why?” they asked. “And how will Didymo affect the survival of the regions’ already vulnerable wild Atlantic salmon stocks?”

Those questions were pressing enough to merit funding from the Atlantic Salmon Conservation Foundation (ASCF) for a number of studies that commenced in 2008. These included habitat assessment of the Matapédia River and an examination of how the presence of Didymo in the area might influence juvenile salmons’ choice of habitat, feeding habits and growth.

As for what had caused the sudden increase in the presence of Didymo in the first place, that’s the mystery. Suggestions range from recreational activities to climate change to shifts in water chemistry.

Enter the Paleoecological Environmental Assessment and Research Lab (PEARL) at Queen’s University.

Words starting with “paleo” conjure up images of an early, archaic or ancient time or condition. As the name suggests, paleolimnology is the study of aquatic ecosystems and their watersheds using the biological, chemical, and physical information stored in sediments that accumulate over many years. By collecting core samples of the sediments from the bottoms of lakes and rivers, paleolimnologists can determine the timing and extent of environmental change, often with strong chronological certainty.

“We believe that the past is the key to understanding the present Didymo situation,” says Dr. Joshua Kurek, a postdoctoral fellow with PEARL. The Board of the ASCF agrees and has provided the PEARL scientists with an $18,000 grant to support their work from May, 2012 through to December, 2013.

The team’s plan was to study the Restigouche River watershed by dovetailing paleolimnological techniques with modern habitat surveys. Core samples collected from the sediment of lakes and rivers would reveal changes in Didymo presence and historic environmental conditions while the  modern habitat surveys provide evidence of what algae are currently distributed throughout local rivers.

The PEARL team identified several promising coring locations and survey sites. Lac au Saumon and Lac Humqui (near the headwaters of the Matapédia River) were cored to identify historic Didymo blooms and other environmental shifts and “determine what watershed changes have led to these blooms,” recounts Dr. Kurek. “Once dated, we anticipate these cores will reflect about 200 years of ecosystem history.”

For the modern habitat survey, samples were collected from 23 sites on the Patapedia, 20 sites on the Upsalquitch, and two sites on the Restigouche.

With all the samples collected, it was then time to start solving the mystery. Lab analyses got underway in September 2012, with some 60 samples from Lac Humqui and Lac au Saumon being processed. These cores have now been dated and measurement of their contents is taking place this winter. Samples collected for the modern habitat survey have been measured for environmental indicators such as pH, water depth, substrate, flow, and percentage of Didymo. Lab analysis of the algae from the modern survey will begin in 2013.

So, what have these Sherlock Holmeses of aquatic ecology turned up? Well, since the lab work and data analysis is ongoing, like many a good mystery, this one is going leave us wondering until next season!

To be continued . . .tune in next year!