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Advisor(s)
Abstract(s)
Natural swimming pools are small constructed lakes for recreational proposes. They are
composed by a swimming area merging with an area planted with emergent and submerged
macrophytes, which function as biological filters. Fish are absent, however a wide diversity of
phytoplankton, zooplankton and macroinvertebrate species colonize these pools. Therefore,
pools can be regarded as the ideal systems to extrapolate the implications of macrophyte
abundance management on algal growth control. The present study was taken in three pools (A,
B and C) located in Minho Region (Northern Portugal) In early summer the macrophyte area had
a 30% of cover in Pool A, in B 40% and in C 60%. Phytoplankton, zooplankton and filamentous
algae abundance as well as conductivity, pH, dissolved oxygen, hardness, nitrates, nitrites,
ammonia, phosphates were recorded in February, April and June. The lowest densities of
phytoplankton were observed in pool C. Besides, filamentous algae were abundant in the pool A,
whereas in B and C they were recorded only in summer. In Pool A, zooplankton assemblage was
always dominated specialists on small particle feeding, which food preference are detritus and
bacteria. Conversely, in the Pool C herbivorous zooplankton was predominant. The low algal
densities observed in the Pool C are explained by the presence of a well established macrophyte
assemblage. These plants contribute to the reduction of algal densities by (1) creating of areas of
shade; (2) removing nutrients from water column and (3) provide refuges for herbivorous
zooplankton. Therefore, the present study stresses the pertinence of take in account the key role
of aquatic macrophytes when management practices for algal growth control are developed.
Description
Keywords
Algal growth management Macrophytes Natural swimming pools
Citation
Geraldes, A.M.; Schwarzer, C.; Schwarzer, U. (2011). Implication of macrophyte abundance on algal management: the case of three natural swimming pools with distinct macrophyte abundance. In 2nd IWA Symposium on lake and reservoir management:Sustainable approaches to enhance water quality. Granada