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Growth limitation of submerged aquatic macrophytes by inorganic carbon
Author(s) -
VADSTRUP METTE,
MADSEN TOM VINDBÆK
Publication year - 1995
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/j.1365-2427.1995.tb00899.x
Subject(s) - elodea canadensis , macrophyte , alkalinity , aquatic plant , environmental chemistry , total inorganic carbon , ecology , botany , biology , chemistry , carbon dioxide , organic chemistry
SUMMARY 1. This study determined the effects of CO 2 and HCO 3 ‐ enrichment on in situ growth of two submerged macrophytes, Elodea canadensis and Callitriche cophocarpa , in two Danish lakes: Lake Hampen and Lake Væng. Lake Hampen is an oligotrophic low‐alkaline lake (0.4 meq −1 ) and Lake Væng is mesotrophic with an alkalinity of 1.1 meq 1‐ −1 . In Lake Hampen experiments were carried out throughout the growth season, whereas experiments in Lake Væng were restricted to late summer. The CO 2 and HCO 3 ‐enrichment procedures used increased the concentration of free‐CO 2 by 500–1000 μM and the concentration of HCO 3 ‐ by about 80 μM. 2. The concentration of free‐CO 2 in Lake Hampen was about five times atmospheric equilibrium concentration (55 μM) in early summer declining to virtually zero at the end of summer. 3. Under ambient conditions Callitriche , which is restricted to CO 2 use, was unable to grow and survive in both lakes. In contrast, Elodea , which has the potential to use HCO 3 ‐ in photosynthesis, grew at rates varying from 0.046 to 0.080 day −1 over the season. 4. Under CO 2 enrichment the growth rate of Callitriche varied from 0.089 to 0.124 day −1 and for Elodea from 0.076 to 0.117 day −1 over the season. Enrichment with HCO 3 ‐affected Elodea only and only to a limited extent. This may be a result of insufficient increase in [HCO 3 ‐] upon enrichment or to a limited capacity of the plants to take up HCO 3 ‐. 5. The substantial stimulation of in situ growth of Elodea and Callitriche by enhanced concentrations of free‐CO 2 shows that inorganic carbon is an important determinant of growth of submerged macrophytes and that inorganic carbon limitation of in situ growth may be a common phenomenon in nature, even in lakes with an alkalinity as high a 1 meq 1‐ −1 . Inorganic carbon, however, is only one of many parameters important for growth, and the growth rates of Elodea at both ambient and high free‐CO 2 were closely coupled to day length and photon irradiance, indicating that light had an ultimate control on growth.