Microalgae productivity measured during three hydrological phases of a temporarily open/closed estuary

• Main Authors: Anandraj, A, Perissinotto, R, Nozais, C
• Format: Conference Proceeding
• Language: English
• Published: College, Laguna (Philippines) APCAB 2006
• Subjects: AFRIQUE DU SUD; AGUA DULCE; AMBIENTE PELAGICO; BENTHOS; BENTOS; EAU DOUCE; ESTUAIRE; ESTUARIES; ESTUARIOS; FITOPLANCTON; FRESHWATER; http://www.fao.org/aos/agrovoc#c_13344; http://www.fao.org/aos/agrovoc#c_2673; http://www.fao.org/aos/agrovoc#c_3102; http://www.fao.org/aos/agrovoc#c_5658; http://www.fao.org/aos/agrovoc#c_6210; http://www.fao.org/aos/agrovoc#c_7252; http://www.fao.org/aos/agrovoc#c_878; MILIEU PELAGIQUE; PELAGIC ENVIRONMENT; PHYTOPLANCTON; PHYTOPLANKTON; PRODUCTIVIDAD; PRODUCTIVITE; PRODUCTIVITY; SOUTH AFRICA; SUDAFRICA

Phytoplankton and microphytobenthic primary production was measured during the closed, open and recovery phase of the temporarily open/closed Maloti estuary (South Africa). The aim of the investigation was to measure variations in microalgal productivity in response to the freshwater input and state of the estuarine mouth. The results showed a significant decrease in phytoplankton and microphytobenthic biomass during the open phase. Integrated pelagic primary production was significantly higher during the closed than the open phase, ranging from 21 to 527 mg C/sq m/h (closed phase) and from 0.8 to 341 mg C/sq m/h (open phase). For the recovery period, productivity varied between 5 and 115 mg C/sq m/h. Pelagic P sup B was significantly higher during the closed and open phase, compared to the recovery phase. Pelagic P sup B ranged from 0.8 to 15, and from 0.3 to 25 mg C mg chl a/h during the closed and open phase, respectively. For the recovery period, P sup B ranged from 0.2 to 1.5 mg C mg chl a/h. Benthic productivity normalized to chlorophyll a was significantly higher during the open phase than during the closed and recovery phase. From the PCA analysis, it can be concluded that major variations in pelagic primary production are mainly controlled by temperature, DIN: DIP molar ratios (water column and pore water), the hydrological state of the estuary at the mouth, and K sub d. Benthic P sup B appears to be stimulated by the prevailing conditions of the open phase, while pelagic P sup B is optimized during both the open and the closed phases.