Avainsana-arkisto: Chironomus

Work outside the lab – field work in lakes

It was time for a field trip, once again. In my project, I have been sampling lake waters, sediments and benthic organisms for several times. I’ll go to the field either during late winter (April) or in autumn (October). Surprisingly enough, it is easier to work in winter, when you have a solid ground – meaning half a meter of ice. In winter, you just saw a hole and start working. It is much easier to get to the lake with a snowmobile than with a large boat trailer.

No rain, barely any wind... is this even possible? Perfect autumn weather in Lake Parkkimanjärvi.
No rain, barely any wind… is this even possible? Perfect autumn weather in Lake Parkkimanjärvi.

For a researcher working mostly in office or lab, it is always fun to go outside. In lab, it often takes months and months to get any results. In field, it’s easier to feel you have accomplished something. It is also a good reminder that our lab conditions are far away from ”real life” in nature. Each time in field, we face surprises: the weather is impossible, benthic organisms have disappeared, fisher’s nets are exactly in the planned sampling point or the equipment break in the middle of nothing. A perfect opportunity to develop your problem-solving skills!

The lakes are mostly located 200-300 km from our university, meaning that you have to prepare everything carefully. If you leave something behind, too bad! This time we got everything we needed. Our goal was to collect chironomids (larvae stage of a non-biting midge) from lake bottoms. We are happy to have a technician with creative mind: He has built us a pump to collect the bottom sediment.  The sediment is taken to a boat (120 l at the time) and sieved in buckets on board. This is repeated as long as we have enough chironomids – most often meaning 1200-1500 l of sediment going through our hands. The work is hard and muddy, the daylight hours are short.

Left: the little red one is our catch, right: Researchers are warm and happy with their seven layers of clothing.
Left: the little red one is our catch, right: Researchers are warm and happy with their seven layers of clothing.

Happily enough, the weather was great. No rain, no ice cover. In picture below, you see the nice surprise we had one autumn: We arrived to the lakes and they were frozen. It is not an easy task to break even a thin ice layer for several hundred meters.

Surprise, it is winter! Good luck with getting the boat to the lake.
Surprise, it is winter! Good luck with getting the boat to the lake.

First three lakes were rather easy. We had a larger boat and there were lots of chironomids to be collected. For the last two lakes, the situation was getting trickier: the lakes were small and shallow, so we needed to change to a smaller boat. Firstly, the roads to the lakes were almost non-existent. And secondly, it was almost impossible to get the boat to our final lake. Yup, the picture below is from a lake. We wore wading boots, because we sunk to our knees in the mud. And since the water was really low, we had to push the boat for more than hundred meters. It is also much more difficult to work in such a small boat.

Left side: hard work with shallow waters and muddy bottom, right side: a Finnish road and our equipment.
Left side: hard work with shallow waters and muddy bottom, right side: a Finnish road and our equipment.

Thank you Kari, Jenny and Nina for your hard work! Without you, I would still be standing next to our first lake, probably crying.

Text by Kristiina Väänänen, photos by Kristiina Väänänen, Jenny Makkonen and Jarkko Akkanen.

Hands-on research with Chironomus riparius

Sitting in the lab in front of a sewing machine was not exactly what I imagined of doing when I started my PhD in the group of aquatic ecotoxicology. However, sewing two hundred miniature mosquito nets was required before I finished my thesis.

Inna and Greta sewing mosquito nets. Photo by Inna Nybom
Inna and Greta sewing mosquito nets. Photo by Inna Nybom

My PhD relates to activated carbon, porous carbon material, which has been studied as a new remediation method for contaminated water ecosystems. Due to its wide surface area, activated carbon can bind numerous contaminants efficiently and lock them in the bottom sediments in a way that they are now longer available for organisms living in the area. Reduced bioavailability of the contaminants for benthic organisms reduces also their transport in the food chain and in time this can reduce the contaminant load to humans from fish consumption. However, both old and new remediation methods, where something is removed or added to the natural ecosystem, can disturb the balance in the field, at least temporarily. Therefore, in this study also direct adverse effects of activated carbon to the benthic organisms were followed.

In our resent work the effects of activated carbon were studied on midge Chironomus riparius. Chironomus riparius is a nonbiting midge, with a four-stage life cycle: egg, larva, pupa and adult midge. Larvae is living in the sediment, and they were grown in activated carbon containing contaminated sediment. After few weeks the larvae develops to flying adult stage, and this is where the mosquito nets come in handy. In order to follow the effects of different exposures to the adult stages, 180 small beakers were sorted on the table and covered with individual mosquito nets, food was provided three times a week and all beakers were monitored daily. All the effort payed off when we finally got the results! We observed that adding activated carbon to the sediment reduces the contamination level not only in the larvae stages but also in the flying adult stages exposed during the larvae stage. We know that the aquatic insects going through metamorphosis can transport the contaminants buried in the bottom sediments to the terrestrial food webs, and our result indicates that adding activated carbon to the sediment may reduce this transport of contaminants! Amongst this we discovered many other cool things, which are published in details in Environmental Science and Technology (2016, 50[10] 5252–5260, DOI: 10.1021/acs.est.6b00991). Check it out, if you are interested in finding out more!

A life cycle of Chironomus riparius
A life cycle of Chironomus riparius. Photo by Inna Nybom

I had a great time working in the croup of aquatic ecotoxicology, but now new adventures are ahead. My PhD project came to an end on December last year when I defended my thesis. The most I am going to miss all the great people I got to work with. A great group of excellent scientist with a catching enthusiasm, innovative to come up with the ideas of 200 miniature mosquito nets, and crazy enough to actually sew them with you!