1) Institute of Earth Sciences, The Hebrew University of Jerusalem, Israel, 2) Kinneret Limnological Laboratory, Israel Oceanographic and Limnological Research, Migdal, Israel, 3) Plankton Ecology and Limnology Laboratory, Program in Ecology and Evolutionary Biology, Department of Biology, University of Oklahoma, USA Inland Waters (2016), V6 (2), pp211-233, doi: 10.5268/IW-6.2.936 Species-specific imprint of the phytoplankton assemblage on carbon isotopes and the carbon cycle in Lake Kinneret, Israel Aram Goodwin (1,2), Jonathan Erez 1), Karl David Hambright 3), Nir Koren (2), Eugeni Barkan (1) and Tamar Zohary (2) Lakes undergoing major changes in phytoplankton species composition are likely to undergo changes in carbon (C) cycling. In this study we used stable C isotopes to understand how the C cycle of Lake Kinneret, Israel, responded to documented changes in phytoplankton species composition. We compared the annual δ13C cycle of particulate organic matter from surface water (POMsurf) between (1) years in which a massive spring bloom of the dinoflagellate Peridinium gatunense occurred (“Peridinium years”) and (2) years in which it did not (“non-Peridinium years”). In non-Peridinium years, the spring δ13C–POMsurf maxima were lower by 3.3‰. These spring δ13C maxima were even lower in POM sinking into sediment traps and in zooplankton (lower by 6.8 and 6.9‰, respectively). These differences in the isotopic composition of the major organic C components in the lake represent ecosystem-level responses to the presence or absence of the key blooming species P. gatunense .