Author(s)

MARIZA A. ABRAMETO, MERCEDES TORRES, GILDA RUFFINI

Abstract

We performed a discrete sampling that was programmed to research the axial distribution of dissolved nutrients in surface waters of the Negro river estuary in Argentina. The total dissolved nitrogen (TDN) was composed mainly of NO₃^- and NH₄⁺; but NO₂^- was not detected. Total dissolved phosphorus (TDP) was in PO₄^-3 and organic species. We obtained spatial and seasonal comparisons from data collected during 2013 and 2016. Both nutrients showed, by analysis of variance (ANOVA), significant differences among the seasons of the year (TDN p<0.0001 and TDP p<0.001). In the internal estuary, the lowest winter levels were 19.4 μM TDN/L, showing that there is a significant difference with autumn levels of 245.6 μM TDN/L by LSD Fischer test (p=0.05); however, the TDN levels in spring were lower than winter at the beginning of the external estuary, and these differences were not significant and could possibly be an indicator of atmospheric removal or re-sedimentation processes in the area. Average TDP values moved in the range between 1.82 μM/L in autumn at the highest, to the lowest values in winter of 0.93 μM/L. The Pearson correlation of N-NO₃ and P-PO₄ in mg/L to the environmental properties showed a negative correlation with salinity, with a range of 0 to 8% pH, and positive correlations with dissolved oxygen. These eutrophication conditions, as with other rivers of the world, could be generating biodiversity imbalances.

Keywords

ammonium, Argentina, estuary, nitrates, nitrites, nitrogen, nutrients, oxygen, phosphate, Rio Negro