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Return to the flooded forests of Amazonia...

Tannin Aquatics

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As we get more and more into the botanical-style aquarium concept, it's interesting to study some of the niche environments that exist in nature, which are heavy influenced by terrestrial life. A prime example of this are the South American forests and swamp forests, which are seasonally inundated with freshwater. These forests are perhaps nature's finest example of the interaction between land and water, and how diverse and surprisiingly productive aquatic environments arise in these habitats. The two types of inundated forest areas are blackwater systems known as igapó, and the counterpart "whitewater" systems called várzea.

The igapó is characterized by seasonal inundation caused by a large amount of rainfall, and thus, in some areas, trees can be submerged for up to 6 months of the year. We've touched on the idea of replicating this habitat in "The Tint" some time ago. These forests have sandy, rather acidic soils with a very low nutrient content. The rainwater combines with the humic substances and tannins contained in the soils and the forest floor materials that are found on them. The acidity from the water corresponds to the acidic soils of these forests. They are the more nutrient poor than a comparable várzea forest, carrying less inorganic elements, yet higher concentrations of dissolved organics, like humic and fulvic acids. (click to read more)