The abundance of polyphenolic compounds in four temporary ponds in Donana National Park (south-western
Spain) was examined during three years of varying hydrology (1989-92). During flooding in 1989-90, the
ponds received large amounts of allochthonous organic matter, as indicated by the relative increases in
dissolved organic carbon (70-120 mg C L-1), dissolved polyphenolic compounds (7.6-12.2 mg L-1) and
water colour (17-33 m-1, A440). As the ponds dried out, the concentration of dissolved polyphenols
decreased rapidly in ponds with abundant submerged macrophytes, whereas the concentrations increased in
unvegetated ponds. Very low concentrations of dissolved polyphenols (1.0-2.8 mg L-1) were measured in
all ponds when they refilled again after drought in October 1991. A large percentage of the initial amount of
polyphenols (80%) and of soil organic matter (71%) disappeared from surface sediments after four months
of drought. The temporary nature of these ponds enhanced the disappearance of allochthonous organic
matter. It is suggested that sunlight and aerobic conditions promote the decrease of organic matter in pond
sediments during drought.
Permanent and temporary ponds in Doñana National Park (SW Spain) are threatened by desiccation