Ferns
Water Fern
Ceratopteris thalictroides
Photo: Krzysztof Ziarnek (Kenraiz) (CC BY-SA 4.0)
The Water Fern is a small, fast-growing aquatic and semi-aquatic fern found in the freshwater margins of Trinidad's wetlands, drainage ditches, and slow-moving streams. One of the very few truly aquatic ferns, it is a pioneer of disturbed wet habitats and an ecologically telling indicator of freshwater quality. Its presence in and around Nariva Swamp connects it to one of the most important freshwater ecosystems in the southern Caribbean.
Description
A small to medium, soft-textured fern showing remarkable variation in form depending on whether it is floating freely or rooted in wet soil. Floating plants produce broad, simple to shallowly lobed fronds that lie flat on the water surface. Rooted plants growing in shallow water or mud produce more finely divided, almost carrot-like fertile fronds standing upright, 15 to 40 cm tall. This dramatic difference between forms of the same species led early botanists to describe them as separate species. Spores are produced along the margins of the upright fertile fronds, enclosed within the rolled frond edge.
Ecology
Ceratopteris thalictroides colonises open, disturbed freshwater habitats: pond margins, rice paddies, slow streams, drainage channels, and flooded ground. It can grow rooted in mud or floating freely on calm water. In T&T it is found at the margins of Nariva Swamp and in similar freshwater wetland habitats across the lowlands of Trinidad. It is a fast-growing annual or short-lived perennial, capable of completing its life cycle rapidly and producing abundant spores that allow it to recolonise suitable habitats quickly after disturbance. It is sensitive to pollution and is considered an indicator of relatively clean freshwater.
Uses
Water Fern is eaten as a vegetable across much of Southeast Asia, where the young fronds and stems are stir-fried or used in salads. This culinary use is not traditional in Trinidad and Tobago but the plant is edible. It is used in aquaria as an oxygenating plant and is popular among aquatic plant hobbyists globally. In traditional medicine across its range it has been used in poultices for skin conditions and burns.
Threats
- Freshwater wetland drainage
- Agricultural runoff pollution
- Invasive aquatic competition