Spatial and temporal trends of Minnesota River phytoplankton and zooplankton

Abstract

Plankton communities have important roles in aquatic ecosystems, but studies of plankton in lotic systems are infrequent. We collected over 100 water, phytoplankton, and zooplankton samples during 2016–2018 to explore spatiotemporal trends in Minnesota River plankton communities and evaluate relationships with physico‐chemical factors. Phytoplankton and zooplankton community structure exhibited temporal patterns but only the zooplankton community differed spatially. Cyanobacteria (M ± SE; 11.27 ± 1.43 mm3/L) and diatoms (8.12 ± 1.08 mm3/L) dominated phytoplankton biovolume with seasonal peaks in Cyanobacteria occurring during July–September and peaks in diatoms occurring during May, August, and September. All phytoplankton taxa except Cryptophyta exhibited a negative relationship with relative discharge. Crustacean zooplankton biomass was greatest at two upstream sites (146.7 ± 32.6 μg/L) where cladocerans and copepods were likely exported from upstream of dams where water residence time is greater. Within the lower free‐flowing reach rotifers dominated the zooplankton community (207.9 ± 40.9 individuals/L and 6.5 ± 1.0 μg/L). Thus, spatial differences in zooplankton community structure were primarily attributed to the influence of dams. Seasonal patterns in zooplankton community structure included peaks in Chydoridae, cyclopoid, immature copepod, and rotifer biomass during May and Bosminidae biomass during October. Excluding the influence of dams on zooplankton, the cumulative effects of month and relative discharge were the most important for explaining variability in plankton community structure. Baseline understanding of plankton community dynamics provides the ability to quantify responses to future perturbations such as climate change and establishment of invasive planktivores.

Diversity of Rotifers in Small Rivers Affected by Human Activity

“…The planktonic animal organisms that constitute part of zooplankton (Cladocera, Copepoda, Rotifera) are indicators of anthropogenic changes in running aquatic environments [42,[50][51][52][53][54][55][56][57][58][59]. However, in both small lowland and highland rivers, the retention time that is required to develop planktonic organisms and to maintain a large abundance of planktonic organisms may be too short.…”

Seasonal and Spatial Distribution of Phytoplankton in Armenian Lotic Ecosystems: Case Study of the Debed River

“…Lotic ecosystems are characterized by flowing waters like rivers, streams, creeks, etc [1]. In comparison to lentic fresh waters (lakes and reservoirs), where phytoplankton have been thoroughly studied, the phytoplankton structure and dynamics in lotic systems are poorly understood [2][3][4]. The spatiotemporal pattern of a community provides information about ecosystem functioning and reflects major environmental changes.…”