Fieldwork stories Summer 2016 – Lava cave exploration and invertebrates' diversity
For five consecutive summers, a team led by Bjarni Kristjánsson, and Camille Leblanc have studied a small freshwater fish, Arctic charr, in lava caves around Lake Mývatn, North East Iceland.
Doriane Combot from France started a MSc project at Hólar University College in summer 2014 investigating aquatic invertebrates in these caves. As she had finished to collect and identify all cladocerans she initially collected for her project, Doriane got awarded a grant from Náttúruverndarsjóður Pálma Jónssonar, to conduct finer analyses. Doriane, helped by Anett Reilent (technician at HUC) and Gary Chevalier (a French intern), went back this summer to collect more samples from these peculiar caves.
The goal of this project was to look at invertebrates' diversity as one go deeper inside the caves therefore where less or no light go through. The traps designed by Doriane and Kári H. Árnason were assembled by three in a triangular shape for each station. Stations were spread from the shoreline (i.e. openings) into the caves at fixed distances.
"Since the traps were made to collect the epi-benthic fauna, i.e. the fauna living above the bottom substrate, it was important to try not to disturb the substrate when laying the traps" said Doriane. The crew used dry-suits in order to float at the surface avoiding disturbance of the bottom. "The water originates from groundwater and therefore is quite cold and constant all year around (approximately 6°C). Light intensity data was also collected at each station".
|View inside a large lava cave monitored in the project June 2016. Photo by Doriane Combot.|
|"It is both fascinating and frightening to go inside the caves. I always have in mind that some part of the roof might collapse at any time. Moreover some caves have small openings and get quite dark as you go further in, which makes it hard to see without a flash light. Some have wide and high openings whereas some have a very low ceiling. Time to time we encounter a fish coming to feed from the flies that fall at the surface of the water. Yes the flies! What would be Mývatn without the flies?! A simple task as changing lids of the containers when picking up the traps can become a real challenge: trying to avoid to fill up the containers with black flies! That’s also without saying that they crave for us. Even all geared up they always find their way to come in and eventually bite!"|
|Three crustacean traps assembled in a triangular shape to form a station. Photo by Doriane Combot.|
|Doriane filling up the containers before laying the traps. Photo by Anett Reilent|
|Doriane floating away into the darkness to lay traps at a specific distance from the shore. Dots in the front of the pictures are the (many) black flies at the opening of the cave. Photos by Anett Reilent.|
|Another lava cave studied in the project. Photo by Anett Reilent.|
|Words by Camille Leblanc and Doriane Combot.|