Assessment of the temporal retention of mercury and nutrient records within the mangrove sediments of a highly impacted estuary

Mangrove ecosystems are dynamic and biodiverse environments with the capacity to sequester more organic carbon per unit area, per time, than terrestrial forests, yet are among one of the most heavily degraded ecosystems on Earth. Here, we quantify trace metal, nutrient and carbon accumulation rates in a tropical mangrove environment in northeast Brazil, a region that has been rapidly developed over the past seven decades. Carbon accumulation rate results show modest or no increase since the 1950's, when major development occurred in the region. Organic carbon isotope (delta C-13) and C:N molar ratios indicate that the OM is primarily derived from autochthonous C-3 plant sources. However, the most recent sediments revealed changes from terrestrial to alga-derived source of OM, which is consistent with the increase of total nitrogen, delta N-15 and total phosphorous content in the last seven decades, suggesting anthmpogenic impact. Furthermore, the Hg enrichment factor (EF) in mangrove sediments is shown to have increased 13-fold since the 1960's, highlighting the ability of tropical mangrove systems in trap filtering pollutants from proximal urban development.

Automated summary

Research in northeast Brazil indicates that carbon accumulation rates in tropical mangrove environments have not increased in the past seven decades, while mercury content has increased 13-fold, suggesting anthropogenic impact and changes in organic matter sources.