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Consequences of riverine flooding for seston and theperiphyton of floating meadows in an Amazon floodplain lake
Author(s) -
Engle Diana L.,
Melack John M.
Publication year - 1993
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1993.38.7.1500
Subject(s) - seston , floodplain , environmental science , periphyton , phytoplankton , tributary , hydrology (agriculture) , benthic zone , biomass (ecology) , nutrient , ecology , geology , biology , cartography , geotechnical engineering , geography
Algal biomass and the chemical composition of seston and floating meadow periphyton were measured in an Amazon floodplain lake during a period of channelized river inflow and a period of overbank flow. During both periods, sedimentation of riverine particulates and loss of dissolved nutrients created strong spatial chemical gradients from the river onto the floodplain which were stable for months at a time. The molar : P of dissolved inorganic nutrients supplied by river water was very low (NO 3 − + NH 4 + : SRP < 5) and decreased further as water entered the floodplain. Initial loss of sediment in surface waters increased the organic content of seston and periphyton and decreased the C : N of seston within 2 km of the river. More gradual loss of finer P‐rich particles caused 2−4‐fold increases in N : P and C : P ratios inside the floodplain. During channelized river inflow, epiphytic algal biomass peaked where inorganic turbidity was high (>50 mg liter −1 ) and phytoplankton biomass was low. Later in the year, overbank flow elevated dissolved nutrient levels inside the lake and disrupted thermal stratification. This transition from lentic to lotic conditions coincided with the seasonal high for epiphytic algal biomass and the seasonal low for phytoplankton biomass. Overall, epiphytic algal biomass was 4–10 times higher than phytoplankton biomass on a per unit area basis. In situ bag experiments revealed that inorganic turbidity regulates the ability of attached algae to utilize nutrients supplied by river water. Epiphytic algal biomass decreased after contact with undiluted river water. Epiphytic algal biomass increased 5‐fold in river water diluted by 90%.