Congratulations to INTERFACES fellow, Viktor Baranov, who published his paper ‘Effects of bioirrigation of non-biting midges (Diptera: Chironomidae)on lake sediment respiration’ in Scientific Reports this week. To give you a taster of his work Viktor has written a summary of his work below.
Bloodworms make lakes take a deeper breath
Despite occupying less than 2% of the land-surface, lakes are extremely important for ecosystem services and society alike. They represent important sites of carbon sequestration, thus contributing to the global CO2 cycle, and regulating greenhouse gas concentration in the atmosphere. Lakes are supporting an astonishing amount of biodiversity, sustaining commercial and recreational fisheries, water transport and water supply for cities, towns and villages.
Lake sediment respiration is an important proxy of lake greenhouse gas emission. Lake sediments are affected by the dwelling of numerous animals – insect larvae, worms, molluscs, shrimps that are building burrows in a process of sediment reworking, called “bioturbation”. When animals are pumping water through the burrow in order to provide oxygen or food particles, they cause complex movement of the liquid within the burrow and through it walls, called “bioirrigation”. Bioirrigation is introducing oxygen-and nutrient rich water into the sediment, which is leading to increased growth and metabolic activity of bacteria, and consequentially, higher sediment respiration. While we suspect for a long time that bioirrigation could drastically enhance sediment respiration, actually measuring and quantifying this process in-situ has not been possible so far.
In order to tackle this long standing problem, the international team of INTERFACES researcher from the Leibniz-Institute of Freshwater Ecology (IGB: Berlin) and University of Birmingham (School of Geography, Earth and Environmental Sciences) investigated in a unique experimental setup the impact of the bioirrigation by bloodworms (Chironomus plumosus), a common benthic invertebrate species, on sediment respiration. To access the impact we have used an array of the cutting-edge ecohydrological and biochemical techniques. They applied the resazurin-resorufin smart tracer system – a bioactive colour dye to measure the amount of respiration in the environment. They established that resazurin transformation is not affected by the bloodworms respiration, due to the specific anatomy of their respiration system, allowing to decouple animal respiration from the respiration of sediment.
The study revealed that sediment is in fact respiring (breathing) more intensely in the presence of bloodworms, and this intensity is proportional to the animal’s density. For example, sediment with 2112 animals per m2 consuming 2.6 time more oxygen than sediment without animals, and all this additional respiration can be attributed to respiration by sediment bacteria, benefiting from animal activities.
These results can help us better understand the lake’s role in greenhouse gases emission where they currently represent carbon sinks. Building on this success, the team is now utilizing the newly established method, to identify a link between bioirrigation, respiration and CO2 emission from lakes in the rapidly warming world.
Paper: Baranov, V. et al. Effects of bioirrigation of non-biting midges (Diptera: Chironomidae) on lake sediment respiration. Sci. Rep. 6, 27329; doi: 10.1038/srep27329 (2016).
Fig.1 (A) Bloodworms has diverse and important functions in the lakes: Role of chironomids (Diptera, Chironomidae) in biogeochemical processes in lake sediments. At the different stages of their life cycle, Chironomus plumosus are engaged in the cycling of various chemical elements in aquatic and terrestrial ecosystems: 1. Larvae of chironomids (bloodworms) are promoting sediment respiration. 2. Flying adults (non-biting, or “blind” midges) are relocating organics and various elements from lakes to the terrestrial habitats. 3. Parts of the dead insects returning to the lake, brining nutrients yet back to the water. (B) Model of resazurin transformation in the populated sediment. (Source of picture: Baranov et. al., 2016, doi:10.1038/srep27329).
Fig.2 Reduction n of resazurin, caused by the respiration.