The combined effects of filter-feeding bivalves (Cristaria plicata) and submerged macrophytes (Hydrilla verticillate) on phytoplankton assemblages in nutrient-enriched freshwater mesocosms

Abstract

Freshwater ecosystems are threatened by eutrophication, which causes persistent and harmful algal blooms. Filter-feeding bivalve mollusks and submerged macrophytes (SMs) alleviate the eutrophication effects by inhibiting phytoplankton biomass blooms. However, very little is known about whether and how the combined manipulation of filter-feeding bivalves and SMs control eutrophication and influence phytoplankton assemblages. Here, we performed a nutrient-enriched freshwater mesocosm experiment to assess the combined effects of the filter-feeding bivalve Cristaria plicata, a cockscomb pearl mussel, and the macrophyte Hydrilla verticillate on the biomass and composition of phytoplankton assemblages. We found that addition of C. plicata and H. verticillate decreased the water nutrient concentrations and suppressed overall phytoplankton biomass. Further, distinct differences in taxa between restoration and control treatments were observed and noticeably competitive exclusion of cyanobacteria in the restoration treatments occurred. An antagonistic interaction between filter-feeding bivalves and SMs was only detected for total cyanobacteria biomass demonstrating that a larger magnitude of SM restoration may override the effect of filter-feeding bivalves. Our results suggest that manipulation, through the addition of bivalves as grazers, associated with the restoration of SMs, is an efficient approach for reducing cyanobacterial blooms and alleviating eutrophication.

Effect of extracellular polymeric substances on the colony size and morphological changes of Microcystis

“…Cells with low and high EPS concentrations first face the binding of TB-EPS to homologous EPS, then resulting in looser colonies. Besides, due to the larger physiological differences between different strains ( Zhang et al., 2007 ; Wu and Song, 2008 ; Du et al., 2023 ), adhesion of Microcystis occurs in the same morphological type relating to different EPS components ( Duan et al., 2022 ).…”

Phytoplankton in headwater streams: spatiotemporal patterns and underlying mechanisms

“…Within a favorable water temperature range, rising water temperatures correspond to higher rates of phytoplankton growth ( Baker and Geider, 2021 ). Changes in nutrient availability can significantly impact phytoplankton community structure, with growth rates being related to nutrient absorption rates under suitable water temperature and pH conditions ( Schulhof et al., 2019 ; Villanova et al., 2021 ; Du et al., 2023 ). Hydrodynamic conditions also play a role in shaping phytoplankton community, as many phytoplankton are prone to thrive under stagnant water conditions ( Li et al., 2013 ).…”