Intra-Annual Variation Of Chlorophyll-A And Nutrients In A Hydraulically Perturbed River-Floodplain System In The Grijalva River Basin

Background: The lateral connectivity in the Maluco river-floodplain system was partially reduced by the highway built on a natural barrier. Goal: To determine if the concentrations of chlorophyll-a (Chl-a) and nutrients contrast in different water levels (WL) during a hydrologic year in the Maluco river-floodplain system. Methods: The WL, Chl-a, and nutrients (NO2-, NO3-, NH(4)(+)and TP) were simultaneously measured six times in two sites during two years. The expected differences of Chl-a and nutrients concentrations, related to the intra-annual fluctuation of the WL, were tested through multivariate techniques. The hypothesis holds that there will be no intra-annual differences of Chl-a and nutrients due to the reduction of lateral interconnection by the physical effect of the embankment. Results: No variable was discarded during PCA. The intra-annual distribution of samples was similar according to the similarity profile routine. Furthermore: 1) more than 54% of the Chl-a and TP values indicated hypereutrophic conditions throughout the year, and 2) none of the values of WL surpassed the height of the bankfull (4.5 mast). The maximum concentrations of Chl-a were registered at the minimum WL values. Conclusions: The intra-annual similarity of Chl-a and inorganic nutrients can be linked to the disconnection between the floodplain and the Grijalva river since the bankfull was not overflowed throughout the sampling time. The intra-annual trend independent at the time of persistence of the high Chl-a and TP concentrations ill the river-floodplain system opens up the opportunity to estimate the minimum input flow required to biogeochemical processes in a long-term study.