Study Progress in Riverine Phytoplankton and its Use as Bio-Indicator - a Review

The value of algae as bio-indicators has already been recognized in the mid of 19th century, however, little attention has been paid to the application of phytoplankton in ecological evaluation of rivers. In this review, we found that studies of phytoplankton showed a long-term increasing trend from 1961 to 2014. However, most of these studies were carried out in oceans, coastal areas, gulfs, lakes and reservoirs, while very few of them (14%) focused on riverine phytoplankton. As well as modeling studies, the utilizations of riverine phytoplankton as bio-indicator are still poorly investigated and the available few studies were those mainly published after the year of 2000. Therefore, we describe 28 algal indices of riverine phytoplankton potentially used for bio-assessment, which belong to community index, growth form, diversity index and biotic index. We also elucidate the calculation and classification methods of 5 common indices proposed in 1950s (Shannon's diversity index, saprobity index) and nowadays (trophic diatom index, Q index and phytoplankton index). Finally, four future directions and applications of riverine phytoplankton research were discussed and proposed: 1) standardization of sampling methods, 2) relations with environmental factors, 3) bio-indication and 4) modeling and predicting dynamics of riverine phytoplankton.