Using NDVI from MODIS to Monitor Duckweed Bloom in Lake Maracaibo, Venezuela

Four summer time-series (2003-2006) of Normalized Difference Vegetation Index (NDVI) derived from MODIS imagery were used to investigate duckweed blooms and other floating vegetation in Lake Maracaibo, Venezuela. Preliminary findings revealed the presence of duckweed and floating vegetation in the Lake during summer in varying amounts (0-11%) that appeared to be related to satellite-derived rainfall anomalies from the Special Sensor Microwave/Imager (SMM/I) during the previous month. The first appearance of duckweed in abundance in 2004 and its reappearance at similar levels in 2006 may indicate a response to increasing nutrient loading in the lake. The duckweed rafts may be an environmental warning of imminent ecological disaster that needs to be mitigated. MODIS data, with its daily repeat cycle and 250 m pixels showed great potential for monitoring floating vegetation in the lake.