Sedimentation may have large negative effects on aquatic vegetation as burial of propagules can reduce emergence. Burial changes the redox potential around the propagules and this might be the mechanism that causes the observed burial effects.
We conducted a laboratory experiment to evaluate the effect of redox potential on the emergence of three aquatic macrophytes from their propagules. Different redox potential treatments were applied by burying propagules of Potamogeton pusillus and Chara cf. contraria at three different depths and with two different sediments (loamy mud and sand). Propagules of Zannichellia palustris were also buried at three depths, but only with sand.
Emergence of P. pusillus and Z. palustris decreased with increasing burial depth, while burial up to 5 cm depth had almost no effect on Chara cf. contraria. Burial with sand reduced emergence of P. pusillus more than burial with loamy mud, while composition of the burial sediment did not affect Chara cf. contraria. The redox potential treatments explained emergence of P. pusillus better than burial depth or composition of the burial sediment separately. There was a strong relationship between mean emergence of P. pusillus per treatment and redox potential of the treatment. Burial caused high mortality of the non-emerged propagules of P. pusillus and Z. palustris within a relatively short period of time.
Our results show that redox potential could be an important factor in causing the effect of burial on emergence. On longer time scale, sedimentation has species-specific consequences potentially leading to changes in vegetation species composition.
