Live Oral Presentation in person as part of National Virtual Conference AFSS Conference 2020

Tropical macrophytes promote phytoplankton community shifts in lake mesocosms: relevance for lake restoration in warm climates (#16)

Darren Sim 1 , Simon Mitrovic 2 , Maxine Mowe 1 , Hugh Tan 1 , Daniel Roelke 3 , Darren Yeo 1
  1. National University of Singapore, Singapore
  2. University of Technology, Sydney, Broadway, NSW, Australia
  3. Texas A+M University, Texas, USA

Macrophytes are crucial for maintaining clear water conditions in temperate shallow lakes. However, the role of macrophytes in regulating phytoplankton in tropical lakes, which experience distinct ecological processes, and their restorative potential remains uncertain. We investigated the effects of emergent (Ludwigia adscendens and Persicaria barbata) and submerged (Vallisneria spiralis) macrophytes on the phytoplankton community of a turbid tropical reservoir. Through two in-situ, four-week, mesocosm experiments, we (1) determined the effects of macrophyte density on phytoplankton biomass and composition, and (2) compared these effects between emergent and submerged macrophytes. In Experiment 1, macrophyte treatments reduced phytoplankton biomass and increased water clarity in a density-dependent manner. Only the higher density treatment (300/650 g fresh biomass) altered the taxonomic composition, favoring green algae and cryptophytes while suppressing cyanobacteria. In Experiment 2, emergent and submerged macrophytes both incrementally reduced phytoplankton biomass but shifted phytoplankton compositions away from cyanobacterial dominance in a turbid tropical reservoir. Our results indicate the potential for different macrophyte growth-forms to reduce phytoplankton biomass and influence phytoplankton community composition away from cyanobacterial dominance in a turbid tropical reservoir. This has potential applications for managing other lakes and reservoirs in tropical climates.