Nutrient availability correlates with bicarbonate accumulation in marine and freshwater sediments – Empirical evidence from pore water analyses

In the last decades, eutrophication has become a major cause for concern in aquatic ecosystems worldwide. Apart from external nutrient loading, release of dissolved nutrients from sediment pore water into the water layer contributes importantly to eutrophication. Theory implies that pore water HCO 3 - and nutrient mobility are linked, because anaerobic organic matter breakdown stimulates release of HCO 3 - and nutrients, while HCO 3 - stimulates decay rates by increasing buffer capacity and pH. An investigation was performed on how HCO 3 - relates to commonly measured eutrophication-related variables in freshwater and marine sediments, by analyzing a database of 71 marine and 206 freshwater samples, using linear and non-linear regression. Results demonstrate that HCO 3 - is indeed strongly related with NH 4 + and PO 4 3 - in both freshwater and marine pore waters. Moreover, HCO 3 - also correlated with sulfide levels in marine sediments. Contrastingly, no relationship was found with variables describing total nutrient content (i.e. organic matter, total P and N), suggesting that these do not reveal information on nutrient availability in aquatic sediments.