Publication Date:
2016-02-26
Description:
Global climate change involves an increase in oceanic CO2 concentrations as well as
thermal stratification of the water column, thereby reducing nutrient supply from deep to surface
waters. Changes in inorganic carbon (C) or nitrogen (N) availability have been shown to affect
marine primary production, yet little is known about their interactive effects. To test for these
effects, we conducted continuous culture experiments under N limitation and exposed the bloomforming
dinoflagellate species Scrippsiella trochoidea and Alexandrium fundyense (formerly A.
tamarense) to CO2 partial pressures (pCO2) ranging between 250 and 1000 μatm. Ratios of particulate
organic carbon (POC) to organic nitrogen (PON) were elevated under N limitation, but also
showed a decreasing trend with increasing pCO2. PON production rates were highest and affinities
for dissolved inorganic N were lowest under elevated pCO2, and our data thus demonstrate a
CO2-dependent trade-off in N assimilation. In A. fundyense, quotas of paralytic shellfish poisoning
toxins were lowered under N limitation, but the offset to those obtained under N-replete conditions
became smaller with increasing pCO2. Consequently, cellular toxicity under N limitation
was highest under elevated pCO2. All in all, our observations imply reduced N stress under elevated
pCO2, which we attribute to a reallocation of energy from C to N assimilation as a consequence
of lowered costs in C acquisition. Such interactive effects of ocean acidification and nutrient
limitation may favor species with adjustable carbon concentrating mechanisms and have
consequences for their competitive success in a future ocean.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Article
,
isiRev
Format:
application/pdf
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