Longitudinal development of chlorophyll and phytoplankton assemblages in a regulated large river (the Ebro River).
The distribution of chlorophyll and phytoplankton communities were compared to nutrient concentrations and hydrological parameters along the main stretch of the river Ebro. A progressive increase in planktonic chlorophyll was observed from the upper reaches to the middle section of the river. Chlorophyll reached a maximum (60-80 microg L(-1)) in the meandering section (downstream of the city of Zaragoza), where nutrient inputs (both N and P) and the residence time of the water are very high. In this meandering section phytoplankton assemblages consisted of large centric diatoms and Scenedesmus sp.pl. These longitudinal patterns were interrupted by the presence of three large reservoirs in the lower section of the river. In the section below the reservoirs, the shorter residence water time, the presence of the invasive zebra mussel, and the massive macrophyte development may explain the historical decrease in chlorophyll-a (from 20-45 microg L(-1) in the 1990s to the present 2-5 microg L(-1)). Phytoplankton densities were extremely poor in this section of the river, where large colonial Coelastrum sp.pl. and Pediastrum sp.pl. were the most characteristic taxa.
Sabater
Sergi
S
Institute of Aquatic Ecology. University of Girona, Spain; Catalan Institute for Water Research (ICRA), E-17003 Girona, Spain. sergi.sabater@udg.es
Artigas
Joan
J
Durán
Concha
C
Pardos
Miriam
M
Romaní
Anna M
AM
Tornés
Elisabet
E
Ylla
Irene
I
D000818:Animals; D002734:Chlorophyll / Q000032:analysis / Q000378:metabolism*; D000077194:Chlorophyll A; D017377:Diatoms / Q000737:chemistry / Q000378:metabolism*; D004784:Environmental Monitoring / Q000379:methods; D005618:Fresh Water / Q000737:chemistry; D010839:Phytoplankton / Q000737:chemistry / Q000502:physiology*; D044444:Scenedesmus / Q000737:chemistry / Q000378:metabolism*; D013030:Spain
D002734:Chlorophyll; D000077194:Chlorophyll A