Role of the propagule bank in reestablishing submerged macrophytes after removal of free-floating plants for recovery of a shallow lake in Southern Brazil

Abstract

At eutrophic shallow subtropical lakes, free-floating macrophytes can occupy the entire water surface. The removal of this vegetation favors the recolonization of submerged macrophytes from the propagule bank. Our study presents the response of the propagule bank of a shallow subtropical lake after management to reduce its hypertrophy. We sampled lake sediment in March 2016 at 15 points along three transects to investigate the richness and density of the propagule bank by emergence in the laboratory. We monitored water trophic conditions and restoration of vegetation in the field for 7 months. In the laboratory, 1382 seedlings of eight species emerged. Stuckenia pectinata and Chara zeylanica dominated the propagule bank. We identified the species S. pectinata, C. zeylanica and Ludwigia peploides in the field. The propagule bank was homogeneous, without difference (P>0.05) between lake regions and transects. Sørensen’s similarity was 36% between the field and laboratory. When the submerged macrophytes grew in the field, there was a reduction of chlorophylla, the water remained clear, and the trophic state index was reduced from hypereutrophic to eutrophic. We concluded that the bank of propagules in shallow lakes is essential for the rapid reestablishment of submerged macrophytes after recovery strategies. These organisms help improve water quality.

Keywords

• seed bank
• emergence of seedlings
• subtropical