Characterization of phytoplankton community in a river ecosystem using pigment composition: a feasibility study

CHEMTAX is a mathematical software for phytoplankton composition evaluation using pigment composition. Although this method has been previously applied in the ocean environment, we firstly utilized the combination of matrix factorization program CHEMTAX and high-performance liquid chromatography (HPLC) to characterize the phytoplankton community from a river system (western part of Weihe River Basin). The obtained results were compared with those from microscopic examination. Based on the comparison, it is suggested that after increasing the ratio of characteristic pigment to chlorophyll a of diatoms and euglena, the diatoms calculated by the CHEMTAX method accounted for 80% of the total biomass, and the results were consistent with microscopic examination, but diatoms obtained from F2, C1 and W5 sample sites were significantly overestimated 33%~60%. The comparison also showed that the model always underestimated cyanobacteria (sample sites F2, C1 were underestimated 25%) and euglena were overestimated (sample sites W3, Q1 were respectively overestimated 33%, 23%), but for chlorophytes, both overestimation and underestimation could occur. When the relevant results from previous applications in the ocean phytoplankton community evaluation were taken into consideration, it can be concluded that CHEMTAX-HPLC method was not accurate enough to characterize the phytoplankton communities in the freshwater (river/lake) ecosystem.