Aquatic macrophytes as bioindicators of carbon dioxide in groundwater fed rivers
2009
Demars, Benoît O.L. | Trémolières, Michèle
Aquatic plants have been used as hydrological tracers in groundwater fed river systems. In nature, patterns in plant distribution have been attributed to ammonium (NH₄) toxicity and phosphate (PO₄) limitation, while some laboratory studies have focused on the role of the partial pressure of CO₂ (pCO₂). The aims of this study were (i) to test whether plant distribution was more related to pCO₂ than NH₄ and PO₄ in nature, (ii) to develop and test the predictive power of new plant indices for pCO₂, NH₄ and PO₄, and (iii) to test the potential causality of the relationships using species eco-physiological traits. These tests were carried out with field data from the Rhine, Rhône and Danube river basins. Species composition was best related to the effect of pCO₂. The pCO₂ plant index was well calibrated (r ² =0.73) and had the best predictive power (r ² =0.47) of the three indices tested on independent datasets. The plant-pCO₂ relationship was supported by a biological mechanism: the ability of strictly submerged species of aquatic vascular plants to use HCO₃ under low pCO₂. This was not the whole story: the effects of pCO₂, NH₄ and PO₄ on plant distribution were partially confounded and interacted all together with temperature. However, neither NH₄ toxicity nor P limitation could be asserted using species eco-physiological traits. Moreover, the predictive power of the NH₄ and PO₄ plant indices was not as strong as pCO₂, at r ² =0.24 and r ² =0.27, respectively. Other potentially confounding variables such as spatial structure, biotic and physical factors were unlikely to confound the findings of this study.
Show more [+] Less [-]AGROVOC Keywords
Bibliographic information
This bibliographic record has been provided by National Agricultural Library
