Intracellular and extracellular ammonium (NH4+) uptake and its toxic effects on the aquatic biomonitor Fontinalis antipyretica
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- Vieira, A.R., Gonzalez, C., Martins-Loução, M.A. et al. Ecotoxicology (2009) 18: 1087. doi:10.1007/s10646-009-0374-6
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The objective of this work is to validate the use of the aquatic moss Fontinalis antipyretica as biomonitor of NH4+ aquatic pollution. In order to achieve this objective we needed to understand the pattern of uptake of NH4+ by the moss and evaluate the impact of high concentrations on its physiological performance. The cellular location of NH4+ in the moss is crucial for understanding its monitoring capacity. We were able to show that a sequential elution technique, based on the use of NiCl2 as an efficient displacing agent, allowed the quantification of the cellular location of NH4+. This was done along a concentration gradient and time of exposure. The extracellular and intracellular NH4+ concentrations that caused significant physiological impact in membrane permeability of F. antipyretica were the same that caused significant decreasing in the photosynthetic capacity of the same moss. The former NH4+ concentration thresholds were shown to decrease with increasing exposure time. These results are important since under natural conditions lower concentration of NH4+ are present in waters but for very long periods of time. The importance of applying this knowledge in biomonitoring studies to fulfil the requirements of the Water Framework Directive is discussed.