Wetland water chemistry, i.e. the concentrations of macro ions in the water, encompasses an important component of the ecological character of a wetland. Of these ions, nutrients play a very active role because they are exchanged between living organisms and the environment via cycling processes involving plants, animals and microbes in the ecosystem. Because many wetlands in agricultural or densely populated parts of the earth are subject to enlarged nutrient inputs, their ecological character may be affected. At the same time, nutrients are processed and retained from the through-flowing water. The present article summarises these aspects of water quality in wetlands and reflects on the development of guidance for managers of wetlands listed as internationally important under the Ramsar Convention. Protection of the water-chemistry characteristics as part of the ecological character of the wetland, consequences of nutrient loading and opportunities for nutrient retention and their limitations are critically evaluated.