Intra-annual variation of chlorophyll-a and nutrients in a hydraulically perturbed river-floodplain system in the Grijalva River basin

Abstract

Allometric growth and reduced pectoral fin regeneration rate in terrestrialized Polypterus senegalus Crecimiento alométrico y disminución de la capacidad de regeneración de la aleta pectoral en Polypterus senegalus terrestrizados

Water Quality Indicators in Three Surface Hydraulic Connection Conditions in Tropical Floodplain Lakes

“…In the study area, TLCs showed the greatest variation in the concentrations of the three indicators, Chl-a, SD, and TP (Table 1), which was reflected in their proportionality overlap with PCL and IL. This amplitude in the variation of indicators in TCL has been related to seasonal flooding water that induces changes in the physicochemistry of water in temporary lakes in the Grijalva basin, the Amazon River, and the Poyang Lake floodplain [11,12,28]. However, the restricted temporal effect of flooding in the study area by the embankments reduced the expected seasonal variation of the water levels.…”

“…All samples were collected from 8:00 a.m. to 01:00 p.m. The four sampling times were established considering the expected water level changes in the Grijalva River [28,47].…”

“…However, the internal TP enrichment is generated through autochthonous organic matter and the exchange with the sediment in conditions of reduced intra-annual fluctuations in water levels [13,29]. Furthermore, the phosphorus enrichment generated by allochthonous matter provided by runoff can be attributed to persistent inputs of urban and agricultural wastewater [16,24,27,28,46,61,66]. In addition, increased TP from sediment resuspension and nutrient assimilation changes the composition of the phytoplankton community, and favors cyanobacterial blooms, which can cause light limitation conditions, as analyzed in a shallow lake in the central part of Jutland, Denmark [67].…”

“…Thus, the nutrient enrichment in the studied lakes with limited or non-existent interconnections was independent of the conditions of SHC. In this context, the hypereutrophication condition has been recorded in other tropical lakes altered by hydraulic infrastructure, resulting in a loss of lateral flooding, restricted water level variation, and an increased water residence time, which affect the dynamics of bioavailable organic phosphorus [28,29,78,79]. The increase of TP concentrations and hypereutrophication in the sampled lakes may be related to autochthonous and allochthonous organic matter, sediment resuspension, and runoff of wastewater from the MAV and from agricultural areas in the rural zone, which was recorded in this and other study areas [8,27,46,68,80,81].…”

“…Aside from the spatial scales, the restricted intra-annual fluctuation in water levels [23,24] is linked with hydrological modifications, causing a loss of lateral flooding and an increase in water residence time [4,[24][25][26]. The loss of lateral flooding, together with the increase in water residence time, help explain the almost permanent eutrophication conditions established by the temporally limited hydraulic interconnection or the isolation of the TCL and IL lakes in the drainage area under study [27,28], as has been recorded for other basins [12,13,25,29]. Along this gradient of surface connectivity, the temporally connected floodplain lakes are intra-annually isolated or interconnected, which can mean that they share the SHC of both lakes, PCL, and IL.…”