Dissimilarity of phytoplankton assemblages in two connected tropical reservoirs: effects of water transportation and environmental filtering

Abstract

To evaluate the importance of dispersal by water transportation in structuring phytoplankton community, we compared phytoplankton composition and succession between two connected tropical reservoirs: a large reservoir with a bottom outlet that periodically feeds a small reservoir via a 40 km open channel. Multivariate analysis was carried out on datasets of phytoplankton for exploring the relationship between phytoplankton and environmental variables. Differential survival of phytoplankton taxa during long channel transportation contributed to high dissimilarity of phytoplankton community between the two reservoirs. Local ecological filtering was mainly responsible for structuring the phytoplankton community with a few dominant functional groups in the large reservoir. Phytoplankton community succession in the large reservoir also showed a clear seasonal pattern. The community in the small reservoir had a more diverse functional group composition and did not show a clear seasonal succession because of strong hydrodynamic disturbance and phytoplankton inoculation with periodic water transportation. In conclusion, periodical transportation and mass effect by dispersal disturb succession and seasonal dynamics, and phytoplankton community assemblage depends on both environmental filtering (habitat selection) and dispersal in the small (receiving) reservoir. In addition, the dissimilarity of phytoplankton community between the connected waters was caused by both habitat difference and differential survival of phytoplankton taxa during transportation.

Phytoplankton assemblages in a complex system of interconnected reservoirs: the role of water transport in dispersal

“…Moreover, these species are continuously inoculated from the river water flowing into the system as suggested by the computed RDA where the inoculum rate contributes to explain a large percentage of the variance observed in the composition of functional groups. Conversely, as observed by Xiao et al (2016), other groups, according to their sensitivity to turbulence and low light, are progressively eliminated from the inoculum as the transportation distance increases. In spite of a direct water connection among water bodies, similarity is thus decreasing when the distance that phytoplankton has to travel in the pipeline is increasing.…”

“…In these systems, dispersal is mediated by water movements (hydrochory), which tend to have a strong homogenizing effect on local communities. However, as shown by Xiao et al (2016) in artificial systems, the connection among reservoirs occurs through pipelines where phytoplankton may be not sufficiently exposed to light to survive transport. In these systems, deterministic factors could have a more important role in shaping the local phytoplankton in different waterbodies.…”

Seasonal Succession of Phytoplankton Functional Groups and Driving Factors of Cyanobacterial Blooms in a Subtropical Reservoir in South China

“…This region has a subtropical climate. The reservoir has a canyon shape, with a storage capacity of 1.15 × 10 9 cubic meters and a catchment area of 1022 km 2 [34]. The water retention time (WRT) in the Gaozhou reservoir was about 451 days [34].…”

“…The reservoir has a canyon shape, with a storage capacity of 1.15 × 10 9 cubic meters and a catchment area of 1022 km 2 [34]. The water retention time (WRT) in the Gaozhou reservoir was about 451 days [34]. Three rivers (the Shenzhen River, the Pengqing River, and the Guding River) feed into the rain collection area of the two sub-areas of the reservoir: the Liangde and Shigu areas (Figure 1).…”

“…S4 site was around by the shoreside of the reservoir and closer to the dam, while S3 site might be affected by S4 site, due to the short distance between the two sites. Hence, the areas with cyanobacterial bloom were relatively closed, with lower flow velocity and less water exchange when compared to other areas of the reservoir [34]. These conditions may result in higher concentrations of phosphorus at these sites, which may induce cyanobacterial blooms.…”