The Life Cycle of the Giant Amazon Water Lily, Victoria amazonica

Robert Stallard: Telephone: +1-303-541-3022; FAX: +1-303-447-2505
e-mail: stallard@colorado.edu

Bob Stallard next to giant water lilies, restinga site near Silves, Amazona, Brasil

(5) The life cycle of the giant Amazon water lily:

In this project, I collaborate with Dr. Robert Meade and others. This research studies the life cycle the giant Amazon Water Lily, Victoria amazonica, (formerly Vitoria regia) as a charismatic-plant metaphor for the understanding of natural and human processes affecting the Amazon River floodplain (várzea). Biogeochemically, it is a study of the groundwater hydrology várzea. Floodplains are the setting for the storage of vast quantities of sediment and carbon worldwide. The storage of sediments in today's floodplains, such as those in the Mississippi River Valley, must be assessed with reference to pre-technological conditions. This is virtually impossible in the case of rivers in temperate climates. The Amazon River has one of the most intact natural floodplains of any large river in the world. Fieldwork is designed to map the floodplain and to characterize springs, seeps, and groundwater fed ponds with the goal of developing a hydrological model of the floodplain and to assess how this groundwater movement affects the storage of nutrients and carbon in the floodplain.

The Amazon River floodplain is tens of km wide, bounded by uplands called terra firme. At low water, the main channel is confined by a complex floodplain that is annually inundated. At low water, the várzea has within it many lakes, and is traversed anastomosing large and small channels - paranas and furos, respectively. Some of the lakes are large, between várzea islands or the várzea and the terra firme, while others from in oxbows, channel cutoffs, and meander scrolls. The limnological view of the várzea treats the lakes as great mixing systems between nutrient-rich decanted Amazon River water and nutrient-poor terra firme river water. The várzea is also constantly being remade by the Amazon. Islands grow downstream and erode upstream, and lateral movements of the channel chew across the landscape.

The annual flood deposits of the várzea form the most fertile soils in Amazonia, and people have exploited this for thousands of years, perhaps before the Andes were populated. Before European diseases wiped out much of the population, corn and cotton was being grown on these soils and population densities were quite high. Now, fishing, ranching, farming, lumbering, and trading are important activities.

We work out of the town of Silves, which is a 350 km boat, bus, or taxi ride from Manaus, the only real city in the central Amazon (a free port with 1.8 million people). Silves is a town of 4000 inhabitants on a unique terra firme island within the flooded region. We stay at the "Aldeia dos Lagos" Ecotourism Hotel, funded by the Austrian government and the World Wildlife Fund. Silves was chosen as a site for this ecotourism hotel, because since 1981, the local government has been actively protecting various aspects of the environment within the municipality of Silves. This includes a number of lakes which are closed to commercial fishing and several tracts of forest.

Remarkably little is know about full the life-cycle natural history of V. amazonica. The leaves can exceed 2 m in diameter, and the stems reach 6 m, and can grow with the rising flood. White female flowers on day one turn into pink male flowers on day two, pollinated by several species of beetle. Apparently, if the seeds dry out at all, they die. It is unclear how V. amazonica survives the dry season. The seeds that are deposited on the várzea surface dry out and die. Seeds that fall in lakes are eaten by fish. Moreover, V. regia appears to grow not from the deepest water areas but from slightly shallower sites about 3 or 4 meters about lowest water, or about 6 meters below highest water. Plants sprout from seeds and keep up with water that can rise as rapidly as 10 cm per day, eventually to produce 5 to 10 leaves a month 1.5 m to 2 m in diameter.

During low water in 1999 and 2000, we observed that the main lily seed bed are pools on the várzea called springs (poços). These pools were about 3-4 m above lowest water and were arrayed across a grassy piece of rather flat várzea. The pools range from 5 m to >100m inn diameter. Many have outlets from which water flowed. The grassland was incredibly marshy and spongy, and people and cows sink up to 1 m into the muck. Apparently, each pool has a spring that feeds water into the pool. The middle-sized and large pools all have lilies. The presence of perennial spring-fed pools on the várzea circumvents several issues. Seeds that end up in the pools do not dry out. The pools did not have any fish that we could see, so no herbivory. Thus, the link between groundwater and ecology became obvious, pointing to an incredible need to understand groundwater hydrology of the Amazon várzea. During low water, most of the V. amazonica colonies are populated by seedlings, which are not at all impressive. One special location which had adult lilies. This was the only area where people were not grazing cattle, goats, or pigs, and I believe that these animals have much affected the life cycle of the plants.

During high water in 2002, we returned. Between June 2001, when Bob Meade observed many lilies, and April 2002, a development bank decided to fund the replacement of cattle by water buffaloes. These buffaloes will go anywhere and they completely destroyed all the giant water lily seed beds. Places that had hundreds of plants a year ago had nothing. In all our searching, we only found one lonely plant.

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