Variable Production by Different Pelagic Energy Mobilizers in Boreal Lakes
- 342 Downloads
We studied production by three key pelagic energy mobilizer communities, phytoplankton (PP), heterotrophic bacteria (HB), and methanotrophic bacteria (MOB), in five boreal lakes of varying size and concentration of dissolved organic carbon (DOC). Production by PP was responsible for most (>55%) of the total pelagic energy mobilization in all five lakes. Production by HB and PP estimated for the whole water column during the ice-free period were positively correlated, but with the exception of the clearest and most eutrophic lake PP apparently could not support the total carbon demand of bacteria. However, the DOC concentration did not explain the variability of heterotrophic bacterial production (HBP) within or between the lakes. Thus, our results provide circumstantial evidence for the “priming effect” whereby labile organic matter from autochthonous production enhances decomposition of allochthonous DOC. However, HBP was only 10–23% of the total pelagic energy mobilization in the lakes, suggesting that only a minor fraction of allochthonous DOC became available for higher trophic levels. High MOB activity was detected in the water columns of the stratified lakes when the molar ratio of CH4:O2 varied between 0.5 and 12. In the small stratified lakes (area < 0.01 km2), MOB production contributed 13–52% of the total pelagic energy mobilization, being greatest during the autumn mixing period. Our results indicate that in small stratified lakes (area < 0.01 km2) bacteria, especially MOB, are potentially quantitatively important supplementary food resources for zooplankton. However, in larger lakes primary producers are the most important (>70%) potential food source for zooplankton.
Keywordsprimary production bacterial production methane oxidation pelagic food web priming effect dissolved organic carbon
This study was partly supported by Academy of Finland Grant 114604 to RIJ, Grant 139786 to PK, and Grant 201623 to AO. AO was also supported by Nordic Centre of Excellence for Studies of Ecosystem Carbon Exchange (NECC). We thank two anonymous reviewers for their suggestions to improve an earlier version of the manuscript.
- Huotari J, Ojala A, Peltomaa E, Pumpanen J, Hari P, Vesala T. 2009. Temporal variations in surface water CO2 concentration in a boreal humic lake based on high-frequency measurements. Boreal Environment Research 14(suppl. A):48–60.Google Scholar
- Keskitalo J, Salonen K. 1994. Manual for integrated monitoring, subprogramme hydrobiology of lakes. Water and Environment Administration B 16:1–41.Google Scholar
- Maanoja S. 2008. Bakteerituotantomittauksissa käytettävän hiilen muunnoskertoimen määritys kahdelle humusjärvelle. (Determination of carbon conversion factor for measuring bacterial production in two humic lakes). Thesis (in Finnish with English summary), Pirkanmaa University of Applied Sciences, Degree Programme in Laboratory Sciences.Google Scholar
- Read JS, Hamilton DP, Desai AR, Rose KC, MacIntyre S, Lenters JD, Smyth RL, Hanson PC, Cole JJ, Staehr PA, Rusak JA, Pierson DC, Brookes JD, Laas A, Wu CH. 2012. Lake-size dependency of wind shear and convection as controls of gas exchange. Geophysical Research Letters 39:L09405. doi: 10.1029/2012GL051886.CrossRefGoogle Scholar
- Salonen K, Arvola L, Rask M. 1984a. Autumnal and vernal circulation of small forest lakes in southern Finland. Verhandlungen der Internationalen Vereinigung für theoretische und angewandte Limnologie 22:103–7.Google Scholar
- Van Gemerden H, Mas J. 1995. Ecology of phototrophic sulfur bacteria. In: Blankenship RE, Madigan MT, Bauer CE, Eds. Anoxygenic photosynthetic bacteria. Dordrecht: Kluwer. Google Scholar
- Weisse T. 2004. Pelagic microbes—protozoa and the microbial food web. In: O’Sullivan PE, Reynolds CS, Eds. The lakes handbook. Volume 1. Limnology and limnetic ecology. Malden, MA: Blackwell Science Ltd. p 417–60.Google Scholar
- Xenopoulos MA, Lodge DM, Frentress J, Kreps TA, Bridgham SD, Grossman E, Jackson CJ. 2003. Regional comparisons of watershed determinants of dissolved organic carbon in temperate lakes from the Upper Great Lakes region and selected regions globally. Limnology and Oceanography 48:2321–34.CrossRefGoogle Scholar