Modelling the impact of benthic filter‐feeders on the composition and biomass of river plankton

Abstract

SUMMARY 1. The POTAMON model [Everbecq E. et al. (2001) Water Research, 35, 901] has been used to simulate the effect of benthic bivalves (mainly Dreissena polymorpha) on the phytoplankton and zooplankton in a lowland Western European river (the Moselle). Here we use a modified version of the POTAMON model with five categories of phytoplankton (Stephanodiscus, Cyclotella‐like, large diatoms, Skeletonema and non‐siliceous algae) to model filter‐feeding effects of benthic bivalves in the Moselle. Zooplankton has been represented in the model by two categories, Brachionus‐like and Keratella‐like rotifers. 2. According to density estimates from field surveys (Bachmann V. et al. (1995) Hydroécologie Appliquée, 7, 185, Bachmann V. & Usseglio‐Polatera P. (1999) Hydrobiologia, 410, 39), zebra mussel density varied among river stretches, and increased through the year to a maximum in summer. Dreissena filtration rates from the literature were used, and mussels have been assumed to feed on different phytoplankton categories (but less on large and filamentous diatoms) as well as on rotifers. 3. The simulations suggest a significant impact of benthic filter‐feeders on potamoplankton and water quality in those stretches where the mussels are abundant, their impact being maximal in summer. Consequently, different plankton groups were not affected to the same extent, depending on their period of development and on indirect effects, such as predation by mussels on herbivorous zooplankton. 4. A daily carbon balance for a typical summer shows the effect of benthic filter‐feeders on planktonic and benthic processes: the flux of organic matter to the bottom is greatly enhanced at high mussel density; conversely, production and breakdown of organic carbon in the water column are reduced. Mussel removal would drive the carbon balance of the river toward autotrophy only in the downstream stretches.

Effects of agricultural land use on fluvial carbon dioxide, methane and nitrous oxide concentrations in a large European river, the Meuse (Belgium)

“…These changes most probably reflect the effect of population growth of invasive benthic filter-feeders such as the zebra mussel (Dreissena polymorpha), the quagga mussel (Dreissena rostriformis) and the Asian clam (Corbicula spp.) (Descy et al, 2003;Pigneur et al, 2014;Marescaux et al, 2015). Surface waters were close to saturation regarding dissolved oxygen in the forested Colonster stream (average %O 2 = 92%) and in the Ourthe (average %O 2 = 101%), distinctly under-saturated in the Geer river (average %O 2 = 29%) and the Meuse (average %O 2 = 86%) ( Table 2).…”

Why are diverse relationships observed between phytoplankton biomass and transport time?

“…For example, in the South San Francisco Bay (Thompson et al 2008) and the Moselle River (Descy et al 2003 Table 1 and Web Appendix 1 for calculation details and data sources). Alpine and Cloern (1992) recognized that in northern San Francisco Bay there was one negative Chl aflow relationship (analogous to a positive P-T relationship) when grazers were scarce, but a different regime, characterized by consistently low Chl a, following the invasion of the clam Corbula amurensis.…”

Modeling metal bioaccumulation in the invasive mussels Dreissena polymorpha and Dreissena rostriformis bugensis in the rivers Rhine and Meuse

“…2). The saturation constant 0.04 g/L was derived from the value of 20 mg C/L determined by Descy et al [19] by using the conversion factor of 2 between organic carbon content and phytoplankton biomass suggested by Roditi et al [20]. The filtration rate is mainly measured per individual (e.g., L/mussel/h) and depends on the mussel size, or dry weight, according to the power function a.W b with various values of a and b reported [21,22].…”