BALANCING AT THE TIPPING POINT: LAGUNA DEL DIARIO AND THE MECHANICAL HARVESTING OF SUBMERGED PLANTS

MAZZEO N, IGLESIAS C, INDA H, GARCÍA-RODRÍGUEZ F, LOTTER AF, GOYENOLA G, TEIXIERA DE MELLO F, VANDERSTUKKEN M, GARAY A, PACHECO JP, VIANNA M, FOSALBA C, GARCÍA S, LOPES FIGUEIRA R, MICHAELOVITCH DE MAHIQUES M, BRACCO R, STUTZ S & E JEPPESEN

Wuxi, China

Congreso; VII Shallow Lakes Conference; 2011

Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences Government of Wuxi, Jiangsu Province

BALANCING AT THE TIPPING POINT: LAGUNA DEL DIARIO AND THE MECHANICAL HARVESTING OF SUBMERGED PLANTS   Mazzeo N, Iglesias C, Inda H, García-Rodríguez F, Lotter A, Goyenola G, Teixiera de Mello F, Vanderstukken M, Garay A, Pacheco JP, Vianna M, Fosalba C, García S, Lopes Figueira R, Michaelovitch de Mahiques M, Bracco R, Stutz S  & E Jeppesen   Shallow lakes are one of the most analyzed examples of systems with alternatives states, consequently the causal and buffer mechanisms involved are very well understood. The proliferation of submerged plants (as a consequence of  the eutrophication) has positive but also negative effects to the water quality and ecosystem services, the last ones particularly notorious when the entire water surface is completely covered by plant biomass. Removing plants can be desirable in such cases. However, in order to prevent a critical transition to a turbid state (dominated by cyanobacteria)  it is crucial a careful design of biomass removal strategies.   The study presents the design of mechanical harvesting program for submerged plants in a shallow Laguna del Diario located in Uruguay based on information from limnological and paleolimnological studies of the lakes as well as from lab and mesocosms experiments. Since 2006 the harvest programme, conducted between November and March, has been following an adaptative scheme based on the observed plant community succession and the main associated limnological effects. The lake showed a considerable resilience to the mechanical harvesting (no transition to turbid state). This was achieved by considering carefully the areas harvested and its spatial distribution, the plant community succession, implication of the seed banks; the biological control of phytoplankton by the submerged plants; the  trophic web structure; and through close collaboration between stakeholders, policymarkers and scientists. The main difficulties and windows of opportunities will be discussed.