Riverine phytoplankton shifting along a lentic-lotic continuum under hydrological, physiochemical conditions and species dispersal

Abstract

The importance of phytoplankton-based bio-assessment has been recently recognized in lowland rivers which are affected by multi-environmental factors. However, some basic questions remain unclear to date, such as: (i) spatial and temporal variations of phytoplankton, (ii) the impact of upstream lakes on downstream community, (iii) the main drivers for species composition or (iv) the regional biodiversity along a lentic-lotic continuum. To answer these questions, we collected and analyzed the fluvial phytoplankton communities along a lentic-lotic continuum from a German lowland catchment, where a well-established ecohydrological modeling predicted long-term discharges at each sampling site. Our results revealed very high spatial and temporal variations of phytoplankton community. The changes of a lake on downstream phytoplankton assemblages were significant, especially the nearest reach after the lake. However, these influences varied along with seasons and limited in a relatively short distance to the lake. Redundancy analysis and Mantel tests showed that phytoplankton composition and dissimilarities along the lentic-lotic continuum attributed more to local hydrological and physicochemical variables than species dispersal, which confirmed the suitability of lowland phytoplankton-based bioassessment. In addition, our findings highlighted the importance of flow regime in shaping phytoplankton community composition and regional beta diversities. This study emphasized the necessity to include the hydrological variables and their relationship with phytoplankton community in future bio-monitoring investigations.

Hydrological and environmental variables outperform spatial factors in structuring species, trait composition, and beta diversity of pelagic algae

“…A previous study on the relations among 83 hydrological metrics and changes in algal communities of the United States was consistent with our study and demonstrated the importance of hydrological variables to the variance of specific algal community metrics (Steuer, Stensvold, & Gregory, ). Moreover, recent studies (Qu et al., ; Wu et al., ), which were in line with our finding, also found that hydrological conditions played an important role in temporal variations of pelagic algae communities. Skewness of flows was found to be one of the most consistently dominant indices across all stream types and may be a particularly important measure of flow condition for certain riverine taxa (Olden & Poff, ), for example, annual skewness of the flow has been linked to fish mobility and colonizing ability (Puckridge, Sheldon, Walker, & Boulton, ).…”

“…Our results in this study showed that the pelagic community in Treene catchment was more affected by local effects (e.g., local hydrological and environmental variables) than spatial effects as indicated by spatial variables (Figure ). These findings supported the recent studies (Qu et al., ; Wu et al., ) and further emphasized the suitability of lowland pelagic algae as bioindicator for local habitat changes. Nevertheless, factors such as interaction between organisms (niche competition), dispersal ability, and species evolution, which were not considered in this study, may have reduced the explainable variations.…”

“…Nevertheless, previous studies and biomonitoring campaigns focused mostly on local environmental variables such as nutrients (Kelly & Whitton, ; Lange, Liess, Piggott, Townsend, & Matthaei, ), pH, temperature (Çelekli, Öztürk, & Kapı, ; Wu, Schmalz, & Fohrer, ), and recently also spatial factors (Heino & MykrÄ, ; Rezende, Santos, Henke‐Oliveira, & Gonçalves, ; Tang, Niu, & Dudgeon, ; Tang, Wu, Li, Fu, & Cai, ; Wu, Cai, & Fohrer, ). By comparison, little attention has been paid to hydrological factors such as flow regime (Qu, Wu, Guse, & Fohrer, ), although many studies have shown that riverine algal communities are linked to flow velocity and discharge (Biggs, Smith, & Duncan, ; Jowett & Biggs, ; Munn, Frey, & Tesoriero, ; Riseng, Wiley, & Stevenson, ; Wu et al., ) and catchment wetness (Wu et al., ). Yet, a profound understanding on the interaction of hydrological variables and river organisms, specifically algae, is still missing.…”

When is a hydrological model sufficiently calibrated to depict flow preferences of riverine species?

“…In particular, macroinvertebrates have evolved distinct adaptations to flow conditions and hence are affected by their changes (Domisch et al, ). These dependencies on flow have been used frequently to assess the occurrence (Pyne & Poff, ) and diversity (Poff & Zimmerman, ) of riverine species, such as fish (O'Keeffe et al, ), benthic invertebrates (Armanini, Horrigan, Monk, Peters, & Baird, ), or phytoplankton (Qu, Wu, Guse, & Fohrer, ), using microcosm experiments (Ceola et al, ), statistical models (Kakouei et al, ), or process‐based models (Mondy & Schuwirth, ). In the absence of direct measurement data or for scenario assessments, modelled streamflow is often used as a data basis for such analysis.…”

Riverine phytoplankton functional groups response to multiple stressors variously depending on hydrological periods

“…TB were dominant in most of the study area, while their share varied in time and space (Qu et al, 2018b). The temporary intensive occurrence of Microcystis in dry season received high concerns from the local stakeholders (Qu et al, 2018a). Therefore, we are especially interested in these two functional groups TB and M, in addition to the phytoplankton community characteristics.…”