El papel del banco de propágulos en el restablecimiento de macrófitos después de la gestión para la recuperación de un lago somero en el sur de Brasil

Taiane H G Duarte,Thaís S Almeida,Cleber Palma-Silva,Edélti F Albertoni

doi:10.25260/ea.20.30.2.0.1014

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.

Highlights

Aquatic macrophytes play an important role in the functioning and maintenance of aquatic ecosystems (Chambers et al 2008; Hilt et al 2017)
The major value in March classified Lake Biguás as hypereutrophic, and during the study period the lake showed mesotrophic (April to June) and eutrophic (July to September) water conditions. These values reflected the total phosphorus (TP) and chlorophyll-a concentration during the monitoring period, where the increased TP was not followed by an increase in phytoplankton (Figure 3)
Our results showed that even with the increase of the phosphorus values, the reestablishment of the submerged macrophytes kept the phytoplankton biomass at low levels and favored the maintenance of the clear water state in this small subtropical lake

Summary

Introduction

Aquatic macrophytes play an important role in the functioning and maintenance of aquatic ecosystems (Chambers et al 2008; Hilt et al 2017). In shallow lakes, ecosystem structure and water quality vary at different nutrient concentrations and water turbidity conditions (Scheffer et al 1993). The development and dominance of submerged macrophytes in these ecosystems promotes clear waters, helps maintain mesotrophic and oligotrophic conditions, and causes the ecosystem to often reach a state of equilibrium (van Nes et al 2003) typically described for temperate climates (Blindow et al 1993; Scheffer et al 2003, 2007). Increase in nutrient loading causes changes in primary producers and alters the state of clear water, with submerged vegetation, to a turbid one, with intense growth of phytoplankton (Blindow et al 2016). It creates unfavorable conditions for the establishment of submerged macrophytes and inhibits their growth (Van den Berg et al 1998). For tropical and subtropical regions, a further alternative state may occur, represented by the excessive proliferation of free-floating aquatic macrophytes that are favored by high nutrient concentrations and water stability (Meerhoff and Jeppesen 2009)

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