Trait shift history: Do grazing induced trait shifts in phytoplankton determine the sensitivity to nutrients and sinking?


ACRONYM
TraitHits
Title
Trait shift history: Do grazing induced trait shifts in phytoplankton determine the sensitivity to nutrients and sinking?
General information
It shall be tested whether shifts in phytoplankton size structure caused by zooplankton grazing determines the responsiveness of phytoplankton to nutrient depletion, nutrient enrichment and sinking. Phytoplankton from the Baltic Sea will be subject to zooplankton grazing in mesocosms. The effect of two types of zooplankton will be contrasted. Copepods which are expected to shift phytoplankton size distribution towards a dominance of smaller cell and the rotifer Brachionus plicatilis which is expected to shift the size distribution towards dominance of larger cells. After conditioning by grazing, phytoplankton communities from the copepod mesocosms, the Brachionus mesocosm and the control mesocosms will be subject to nutrient starvation and nutrient enrichment. Sinking rates will be measured at the end of the conditioning phase and in response to the nutrient treatments. The working hypotheses are: 1) Copepod grazing will shift protist size distributions to a dominance of small cells. 2) Brachionus grazing will shift protist size distributions to a dominance of large cells. 3) Copepod-conditioned protist plankton will a) respond with faster growth to nutrient additions. b) better cope with prolonged nutrient shortage. c) be less vulnerable to sinking losses. 4) Brachionus-conditioned protist plankton will a) sustain growth after nutrient addition for a longer period. b) initially maintain growth longer after the transition to nutrient shortage. c) be more vulnerable to sinking losses. 5) Sinking rates will also be influenced by nutritional state, as expressed by the C : limiting nutrient ratio in biomass.
Start October, 2014 End September, 2017
Funding (total) - Funding (GEOMAR) 191 T€
Funding body DFG Programme Priority Programme (SPP)
Contact Ulrich Sommer

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