Publication Date:
2021-04-23
Description:
Concentrations of heme b were determined in a mesocosm experiment situated in Gullmar
Fjord off Sweden. The mesocosm experiment lasted for ca. one hundred days and was
characterised by the growth of a primary nutrient replete and a secondary nutrient deplete
phytoplankton bloom. Heme b varied between 40 ± 10 pmol L-1 in the prebloom period up to
a maximum of 700 ± 400 pmol L-1 just prior to the time of the primary chlorophyll a maximum.
Thereafter, heme b concentrations decreased again to an average of 120 ± 60 pmol L-1.
When normalised to total particulate carbon, heme b was most abundant during the initiation
of the nutrient replete spring bloom, when ratios reached 52 ± 24 μmol mol-1; ten times
higher than values observed both pre and post the primary bloom. Concentrations of heme
b correlated with those of chlorophyll a. Nevertheless, differences were observed in the relative
concentrations of the two parameters, with heme b concentrations increasing relative to
chlorophyll a during the growth of the primary bloom, decreasing over the period of the secondary
bloom and increasing again through the latter period of the experiment. Heme b
abundance was therefore influenced by nutrient concentrations and also likely by changing
community composition. In half of the mesocosms, pCO2 was elevated and maintained at
ca.1000 μatm, however we observed no significant differences between heme b in plus or
ambient pCO2 mesocosms, either in absolute terms, or relative to total particulate carbon
and chlorophyll a. The results obtained in this study contribute to our understanding of the
distribution of this significant component of the biogenic iron pool, and provide an iron
replete coastal water end member that aids the interpretation of the distributions of heme b
in more iron deplete open ocean waters.
Type:
Article
,
PeerReviewed
Format:
text
DOI:
10.1371/journal.pone.0176268
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