Seagrass beds are high productive ecosystems which occur in
the sea, in lagoons and in estuaries. They are prominent features
of many sand and reef flats in the coastal waters of Sri Lanka,
Although well represented throughout the island, there is little
information on their distribution and ecology. Salm in 1981 has
indicated the locations of the seagrass beds in the Kokkilai
lagoon, Puttalam and Dutch Bays, Jaffna and Mannar Districts as
well as in the Negombo Lagoon. Some information is also available
on the taxonomy of seagrasses, but there appears to be some
confusion even with respect to the genera that have been recorded
for Sri Lanka. Abeywickrema (pers. comm.) records 12 species
divided among 9 genera for Sri Lanka based on previous records.
}The genera Halodule. Zostera and Thalassiodendron recorded for its Sri Lanka by Samarakoon in 1986 in a draft Technical Report of a
Workshop on Critical Habitats in the Coastal Zone (CCD/USAID/URI)
if they are truely present, have not been included in
Abeywickrema's records.
The present investigation has indicated the presence of
extensive beds of seagrasses in the Negombo Lagoon. In areal
extent the cover by seagrass beds exceed that of the mangroves of
the Negombo Lagoon at least by three times. It is possible that
the highly productive seagrass beds in the Negombo Lagoon play a
major and a more important role in the fisheries productivity
than the mangroves. Further research need to be geared to
determining the the contribution of the seagrass beds to • *
particularly the productive prawn fishery of the Negombo Lagoon.
The following seagrasses were recorded in the lagoon during
the present investigation;
i) Halophila ovalis
ii) Halophila beccarii
iii) Halophila sp.
iv) Ruppia sp.
v) Syringodium isoetifolium
vi) Halodule ?
Further, during the investigation, several activities that
could stress the seagrass beds were observed. Among them were;
(i) The use of drag nets for fishing.
(ii) The disturbance to seagrass beds by the
collection of polychaete worms to be used as a
feed in the shrimp hatcheries that have developed
recently in the Negombo area.