Phytoplankton as a monitoring tool in a tropical urban shallow reservoir (Garças Pond): the assemblage index application

• Published in: Hydrobiologia Vol. 610; no. 1; pp. 161 - 173
• Main Authors: Crossetti, Luciane O, de M. Bicudo, Carlos E
• Format: Journal Article
• Language: English
• Published: Dordrecht Dordrecht : Springer Netherlands 01.09.2008; Springer Netherlands; Springer; Springer Nature B.V
• Subjects: Alkalinity; Animal and plant ecology; Animal, plant and microbial ecology; Aquatic plants; Barriers; Biological and medical sciences; Biomedical and Life Sciences; Carbon dioxide; Dissolved inorganic carbon; Ecology; Eutrophication; Floating plants; Fresh water ecosystems; Freshwater & Marine Ecology; Freshwater ecology; Fundamental and applied biological sciences. Psychology; General aspects; Life Sciences; Light penetration; Nutrient dynamics; Phytoplankton; Plankton; Ponds; Primary Research Paper; Reservoirs; Synecology; Urban areas; Variance analysis; Water column; Water quality; Water quality assessments; Water temperature; Zoology; Assemblage index; Cyanobacteria; Water quality; Tropical shallow lake; Phytoplankton; Functional groups; Eutrophication; Tropical zone; Eichhomia crassipes; Reservoir; Urban area; Shallow water; Aquatic environment; Pond; Hydrobiology; Lakes; Bacteria; Community; Functional group
• ISSN: 0018-8158; 1573-5117
• DOI: 10.1007/s10750-008-9431-z

This study aimed at evaluating phytoplankton as a monitoring tool for water quality assessment in an urban shallow eutrophic reservoir considering temporal and vertical scales. Garças Reservoir is located in the Parque Estadual das Fontes do Ipiranga Biological Reserve (23°38'08"S and 23°40'18"S; 46°36'48"W and 46°38'00"W) that lies in the southeastern part of the Municipality of São Paulo, southeast Brazil. Samplings were carried out monthly during 8 consecutive years (1997-2004) following the water column vertical profile (5 depths: subsurface, 1, 2, 3 m and ~20 cm from the bottom). Abiotic variables analyzed were: water temperature, electric conductivity, DO, pH, total alkalinity, free CO₂, dissolved inorganic carbon, N series, P series and SiO₄H₄. Biological variables studied were: total density, total biomass and chlorophyll a, which were integrated arithmetically. At the beginning of the 8 year series, Garças Reservoir was an eutrophic ecosystem with 20% of its surface covered by Eichhornia crassipes (phase I: January 1997-March 1998). Water hyacinth reached 70% of pond surface coverage (phase II: April 1998-August 1999), and then it was mechanically removed (phase III: September 1999-December 2004). After this intervention, drastic alteration in the limnological features was detected, leading to the conclusion that removal of the aquatic macrophyte modified nutrient dynamics drastically reduced water transparency and led to photosynthetic productivity and phytoplankton biomass increase, the latter becoming a physical barrier to light penetration. Twenty one functional groups 'sensu' Reynolds were identified. Cyanobacteria contribution played the main role during the drastic alterations that occurred after water hyacinth removal. Results of ecological status of reservoir using Q index showed statistical difference among the 3 limnological phases (one way ANOVA; F = 119.4; P = 0.000). Regarding Q index classification, Garças Reservoir limnological phases were characterized as follows: (1) phase I: 0 >= Q <= 2.9, medium to bad; (2) phase II: 1.4 >= Q <= 3, tolerable to medium; and (3) phase III: 0 >= Q <= 1.5, bad to tolerable ecological states.