Physiological constraints on the global distribution of Trichodesmium – effect of temperature on diazotrophy

Breitbarth, E., Oschlies, A. and LaRoche, J. (2007) Physiological constraints on the global distribution of Trichodesmium – effect of temperature on diazotrophy. Biogeosciences, 4 (1), 53-61.

Abstract

The cyanobacterium Trichodesmium is an important
link in the global nitrogen cycle due to its significant
input of atmospheric nitrogen to the ocean. Attempts to incorporate
Trichodesmium in ocean biogeochemical circulation
models have, so far, relied on the observed correlation
between temperature and Trichodesmium abundance. This
correlation may result in part from a direct effect of temperature
on Trichodesmium growth rates through the control
of cellular biochemical processes, or indirectly through
temperature influence on mixed layer depth, light and nutrient
regimes. Here we present results indicating that the
observed correlation of Trichodesmium with temperature in
the field reflects primarily the direct physiological effects of
temperature on diazotrophic growth of Trichodesmium. Trichodesmium
IMS-101 (an isolate of T. erythraeum) could acclimate
and grow at temperatures ranging from 20 to 34C.
Maximum growth rates (?max=0.25 day?1) and maximum
nitrogen fixation rates (0.13 mmol N mol POC?1 h?1) were
measured within 24 to 30C. Combining this empirical relationship
with global warming scenarios derived from stateof-
the-art climate models sets a physiological constraint on
the future distribution of Trichodesmium that could significantly
affect the future nitrogen input into oligotrophic waters
by this diazotroph.

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