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Stoichiometric and growth responses of a freshwater filamentous green alga to varying nutrient supplies: slow and steady wins the race
Author(s) -
Middleton Colleen M.,
Frost Paul C.
Publication year - 2014
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1111/fwb.12425
Subject(s) - ecological stoichiometry , nutrient , algae , zoology , phosphorus , nitrogen , stoichiometry , chlorophyll a , relative growth rate , biology , growth rate , chlorophyll , botany , photosynthesis , environmental chemistry , chemistry , ecology , geometry , mathematics , organic chemistry
Summary We examined how the nutrient stoichiometry of the filamentous green alga, M ougeotia sp., is affected by the relative availability of dissolved nitrogen ( N ) and phosphorus ( P ). Using a bioassay experiment, we grew M ougeotia in medium having a range of dissolved N and P concentrations and N : P ratios (0.62 to 411 by mol). After growing M ougeotia in an environmental chamber for 17 days, we measured its carbon ( C ), N and P content (% of dry mass), molar C : N : P ratios, mass‐specific growth rate ( MSGR , day −1 ), chlorophyll a concentration ( C hl, μg L −1 ) and carbon:chlorophyll a ( C : C hl) ratios. Due largely to variation in cellular % N and % P , M ougeotia C : N : P ratios varied considerably at the end of the experiment, with C : N ratios ranging from 6 to 41, C : P ratios ranging from 85 to 999 and N : P ratios ranging from 4 to 118. We found M ougeotia to be weakly homeostatic with respect to N : P content, with non‐homeostatic tendencies found for N content and P content. Despite the wide range of N and P concentrations in the medium at the start of the experiment, M ougeotia MSGR was relatively invariant. Nevertheless, high C : C hl ratios observed for N ‐ and P ‐limited M ougeotia largely matched those expected for algae experiencing nutrient‐limited growth. We further compared our experimental results with stoichiometric data for M ougeotia collected from the K awartha L akes in southern O ntario. The high C : P and N : P ratios found in field samples matched those of laboratory M ougeotia experiencing intense and sustained P limitation and are suggestive of severe P limitation of M ougeotia in K awartha L akes throughout the summer. The slow growth rates and flexible stoichiometry of this alga would enable it to continue growing even during periods of acute nutrient stress. Hence, future management and control of this nuisance alga may prove difficult if it is unlikely to respond strongly to reductions in external P loading and lower water column P concentrations.