Effect of hydrodynamic disturbances on the biomass and architecture of the freshwater macroalga Chara globularis Thuill.

The effect of wave-induced disturbances in the shallow littoral zone on Chara globularis individuals was studied in three populations located in three different lakes in Poland. In addition, an experiment was performed to check if the observed responses were confirmed in vegetative offspring grown ex situ. Individuals from wave-exposed sites were lighter than those from sheltered ones; they had more ramets and lateral branches. The main axes, branches, internodes and branchlets were shorter. The shortening of the main axis was a statistically significant response in each population. The reduction of biomass of thalli and shortening of branchlets under wave-exposed conditions was statistically significant only in part of the populations. The differences in underground biomass, number of branches, length of internodes and presence of holdfasts among individuals from wave-exposed and sheltered sites in the populations showed inconsistent trends between populations. This suggests a location-specific nature of some of the morphological variations. The vegetative offspring (new ramets obtained ex situ) from the fragments of individuals growing at wave-exposed sites were lighter, smaller, had shorter axes in a statistically significant way in comparison with the offspring from sheltered sites. The observed growth trend was the same as in the case of parent individuals. Hence the response noted in the parent population was confirmed in vegetative offspring. For all the remaining features, differences were more pronounced between new ramets than between parent individuals. Hence, in situ, the phenotypic responses to other environmental factors overlapped with the disturbance-related responses.