title: Porewater methane transport within the gas vesicles of diurnally migrating Chaoborus spp.: An energetic advantage.
abstract: Diurnally-migrating Chaoborus spp. reach populations of up to 130,000 individuals m-2in lakes up to 70 meters deep on all continents except Antarctica. Linked to eutrophication, migrating Chaoborus spp. dwell in the anoxic sediment during daytime and feed in the oxic surface layer at night. Our experiments show that by burrowing into the sediment, Chaoborus spp. utilize the high dissolved gas partial pressure of sediment methane to inflate their tracheal sacs. This mechanism provides a significant energetic advantage that allows the larvae to migrate via passive buoyancy rather than more energy-costly swimming. The Chaoborus spp. larvae, in addition to potentially releasing sediment methane bubbles twice a day by entering and leaving the sediment, also transport porewater methane within their gas vesicles into the water column, resulting in a flux of 0.01-2 mol m-2yr-1depending on population density and water depth. Chaoborus spp. emerging annually as flies also result in 0.1-6 mol m-2yr-1of carbon export from the system. Finding the tipping point in lake eutrophication enabling this methane-powered migration mechanism is crucial for ultimately reconstructing the geographical expansion of Chaoborus spp., and the corresponding shifts in the lake's biogeochemistry, carbon cycling and food web structure.
authors.affiliation: Aquatic Physics Group, Department F.-A. Forel for Environmental and Aquatic Sciences (DEFSE), Section of Earth and Environmental Sciences, Faculty of Sciences, University of Geneva, Uni Carl Vogt, 66 boulevard Carl-Vogt, CH-1211 Geneva, Switzerland.|Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Mueggelseedamm 310, 12587 Berlin, Germany.
authors.forename: Daniel F
authors.initials: DF
authors.lastname: McGinnis
authors.affiliation: Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Mueggelseedamm 310, 12587 Berlin, Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: Flury
authors.affiliation: Department of Biosciences, Swansea University, Wallace Building 104, SA2 8PP Swansea, UK.
authors.forename: Kam W
authors.initials: KW
authors.lastname: Tang
authors.affiliation: Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Mueggelseedamm 310, 12587 Berlin, Germany.|Potsdam University, Institute of Biochemistry and Biology, Maulbeerallee 2, 14469 Potsdam, Germany.
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Grossart
mesh_terms: D000818:Animals; D000864:Antarctic Regions; D001692:Biological Transport; D002244:Carbon / Q000737:chemistry / Q000378:metabolism*; D000073563:Culicomorpha / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D005068:Eutrophication; D019015:Geologic Sediments / Q000737:chemistry; D060106:Lakes; D007814:Larva / Q000737:chemistry / Q000378:metabolism; D008697:Methane / Q000737:chemistry / Q000378:metabolism*; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water; D002244:Carbon; D008697:Methane