Monday, February 16, 2009

Florida Everglades and Tropical Blackwater systems

I finally got to see the famous Everglades of Florida, in the company of two botanists, Jack Fisher of the Fairchild Tropical Botanical Garden and David Lee of Florida International University.

It was a warm Sunday and the Everglades National Park had plenty of visitors. The most amazing sight was the large number of alligators sunning themselves on the side of the road. The Park Rangers warn visitors not to get closer than 10 feet of the alligators. It is a very serious offence to feed the animals.

I recognized a number of plants that are grown in Malaysia as ornamentals but which are native to the Everglades. These include the pond weed Pontederia cordata, the creeping palm Serenoa repens and the white-flowered sedge Dichromena sp.

I was intrigued that the water is black (actually tea-coloured)and the bed rock is limestone. In Malaysia blackwater is associated with sand, on the sandy plateaus of Gunong Tahan and the Maliau Basin and in the Kerangas forests of Borneo. Blackwater systems are reputed everywhere to be poor in nutrients. The colour is due to tannin leached out from decaying leaves. The question arises as to why ALL forested rivers systems are not blackwater systems. In Kuala Tahan in Malaysia's Taman Negara National Park, two great rivers meet. One is a blackwater river, the Sg Tahan, arising on a sandstone mountain and flowing over sand; the other is normal water from a granite mountain flowing over clay (derived from weathering of granite). This suggests that the reason for blackwater is the absence of clay to absorb tannins. Clay is also known to absorb and hold nutrients. In its absence, nutrients would flow out of the system. In Borneo 'kerangas' means 'land on which rice cannot be grown'. So the Everglades may be an American version of Kerangas.


Barry said...

I'm glad that you enjoyed your visit to Florida, and to our wonderful Everglades. Please don't feed the alligators!

Andrea said...

I envy your chance to see the Everglades. I have a long lost friend, whom i just saw on Facebook, who said her backyard is the Everglades, and i am so fascinated by her photos. The Everglades is a marvel of nature, i wish i can see it also in this lifetime.

By the way, i have long ago read that many tropical plants especially the palms at the Fairchild Botanical Garden is from our Mt Makiling in the Philippines.