TITLE:
River Flows Influence on Nutrients (Si, N and P) and Fecal Coliforms (E. coli) in Two Tributaries of the Estuarine Channel of Bertioga (Santos Estuary, São Paulo, Brazil)
AUTHORS:
Bruno Otero Sutti, Luciana Lopes Guimarães, Roberto Pereira Borges, Elisabete de Santis Braga
KEYWORDS:
Eutrophication, Domestic Sewage, Water Quality, Seasonal Period, Estuary
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.10 No.6,
June
22,
2022
ABSTRACT: Sewage introduction into rivers has altered the
physical and chemical properties of waters and also the microbial metabolism.
This study aimed to evaluate the Escherichia
coli and nutrient concentrations in the Maratuã and Crumaú rivers (Santos Estuary, Brazil) during two periods with distinct
magnitudes of freshwater runoff, verifying possible relation of abiotic changes with
the microbial metabolism. Water sampling was performed in October/2012 (dry season) and January/2013 (rainy
season) at two points in the Crumaú river (upstream and downstream zone) and
one in the Maratuã river (downstream zone). The water subsamples were obtained
for E. coli and nutrient analyses
while the velocity of water flow, water level, temperature, salinity, and
dissolved oxygen were measured in situ.
The E. coli concentrations were under
the detection limit in the Maratuã downstream during the dry season reaching a
maximum value (1.47 × 104 CFU/100mL) in the Crumaú upstream during the rainy season. E. coli presented strong positive correlation with nutrients (ammoniacal-N
and phosphate), evidencing the sewage source in the Crumaú upstream shown by this association. In both periods, the low
oxygen saturation
(100 μmol·L-1)
indicated considerable predominance of heterotrophic metabolism in the Crumaú
upstream. The low dissolved oxygen values in Crumaú River are corroborated to show a low self-depuration capacity
in the rainy period due to maintenance of high nutrient and E. coli at two points in the Crumaú
river (upstream and downstream zone) and one in the Maratuã river (downstream
zone). Besides, these results evidenced that the tendency of the metabolism
changed from autotrophic to heterotrophic under high river flow events at this
studied estuarine sector located at Santos estuarine complex.