by Dallas Korell
Collaboration efforts between the Centre for Earth Observation Science (CEOS) and the Lake Winnipeg Research Consortium (LWRC) have begun in an attempt to expand freshwater research in Lake Winnipeg. The research done during the 2018 survey season will be a trial run with Dr. Tim Papakyriakou, focusing largely on examining the carbon system in Lake Winnipeg. Using a pCO2 box hooked up to an automated algal sampling machine, continuous samples will be collected as the ship travels between stations. Additionally, whole water samples (both surface and bottom) will be taken and sent to the Freshwater Institute for analysis of carbon (suspended, dissolved, organic and inorganic), total chlorophyll, alkalinity, conductivity and pH. Algae samples will also be collected at specified stations in the lake.
Sample Day 1
On June 12, 2018, the first survey of Lake Winnipeg began. The Fylgja, a 42-foot touring boat, and a total group of 7 (5 research staff and 2 crew) departed at approximately 7:30 am from Hnausa for station 57B in the south basin. The ride to station 57B was fairly rough due to high wind velocities which made for choppy waters with waves approaching 2 meters in height. Once we arrived at station 57B, a Van Dorn sampler was used to collect the water sample from a predetermined depth. A 500mL plastic sample bottle was cleaned out three times using the water collected from the Van Dorn sampler and then filled to 1/4 from the top to ensure enough space to properly mix the sample. Immediately after filling the sample bottle, the temperature of the water sample was taken and noted and a subsample for algae was placed into a small Lugols filled vial. Additional samples for Dissolved Organic Carbon (DOC), 13C-DOC, Total Alkalinity (TA) and Methane (CH4) were taken from the pCO2 tubing. A CTD (Idronaut) profile should be taken at each station to measure conductivity, temperature, and depth. During this stage of the survey, the captain of the boat advised us that we would need to turn back and dock due to increasing wind velocities, and so no CTD profile was captured for station 57B. In ideal conditions, the CTD device is first turned on and calibrated by holding it over the railing so the sensors are above the surface of the water. Once calibrated, the CTD device is lowered into the water and held at the surface for one minute. Afterward, it is lowered at approximately one meter per second to the bottom based on station depth. Once the bottom has been reached, the device is pulled back up at the same speed and turned off once back on the boat. A CTD profile is required at each station even if a whole water sample is not collected.
The filtering process is done on the boat while it is docked at Hnausa. All required equipment is set up in the boat on a table covered with tin foil which we clean using ethanol to decrease the chance of contamination. Before proceeding with the filtering of the water sample, blank filters must be processed once a day while in the field. This is done by placing one GF/C filter paper onto the bottom of a magnetic filter unit and pouring 100mL of distilled water through it into a glass vase. This filter paper is then placed in a petri dish. An additional filter paper is placed in another petri dish with no water having been filtered through it and both of these are put aside and labeled as blanks. Next, we begin filtering the water sample by placing a filter paper into the filter unit. The sample water is shaken in the plastic sample bottle and 100mL is poured into a graduated cylinder which is then poured onto the filter paper. For filtering in the field, we set up an air pump to create a vacuum and turned it on right before the water is poured onto the filter paper and turned it off right after the water is done filtering through. When no more water is visibly filtering through the paper, the filter paper is removed using flat-headed tweezers and placed into a separate petri dish labelled for suspended C/N (100mL). The filtrate is dumped and the process is repeated for chlorophyll, this time using 200mL of distilled water instead of 100mL. Additionally, the filtrate for this portion of the filtering process is poured into an anion bottle and labeled correctly to be sent off to the Freshwater Institute for analysis. When staying in the field for days at a time, the filter papers are left out to dry and then placed in a desiccator (with the top of the petri dish left open) overnight. Since I was traveling back to Winnipeg the same day, the samples were taken back with me and placed in appropriate storage overnight and taken to the Freshwater Institute.