Land reclamations along coastal areas, and the occurrence of red tides are usually associated. Reclamations often result in red tides.
Reclamations change the direction of long-shore currents along coastal areas, and often create areas with relatively stagnant waters.
Conditions of high temperatures and sudden rainfall after a prolonged dry season are ripe for the development of red tides.
The flood of rainwater from land carries nutrients into the relatively stagnant, warm water, and results in blooms of dinoflagellate species of the genera Pyrodinium, Gymnodinium, Gambierdiscus and Alexandrium.
These species, which form part of the plankton, produce the toxins of red tides. Conditions that bring about development of algal blooms often occur during these days of climate change.
The toxins are magnified in the food chain when the dinoflagellates are fed upon by finfish and shellfish, which pass them on to man.
The toxins can make people very sick, causing gastrointestinal disorders and permanent neurological damage. Cases of death due to these toxins have been reported.
The news media have recently reported cases of red tides in Bacolod City (Negros Occidental), Tagbilaran (Bohol), and in shellfish areas of Capiz province.
Sometime ago, red tide was reported from Bais Bay (Negros Oriental).
Almost every year during the hot season, red tides occur in parts of Manila Bay and Samar, making shellfish and certain finfish poisonous to eat.
In these two areas, dinoflagellate species producing the red tide toxins are there permanently waiting for the right environmental conditions to bloom.
We visited Tagbilaran City early this month when the red tides were reported by the press. The specific area known to have red tide organisms was a portion of the area between Panglao Island and Bohol Island.
This area was enclosed by two reclaimed road systems connecting the two islands, with very small provisions for water to flow through, thus, making the area relatively-stagnant.
A Google map verified the very limited flow of marine waters in this red tide area.
It is clear that the roads should have been constructed on piles to allow the free flow of water, just like the conditions in the past.
The widespread occurrence of red tides in the Philippines has been documented by Dr. Rhodora Azanza and her colleagues at the University of the Philippines-Diliman. Because of its serious effects on the health and well being of human beings, they should be studied intensively.
Because one of the human activities that causes red tides is reclamation in coastal areas, our government departments (e.g. DPWH) responsible for constructing infrastructures along coastal areas should be very careful that the structures they build should not interfere with the natural processes of nature, such as water circulation and ocean currents.
There have been many cases of erosion due to land reclamations that have resulted in the occurrence of red tides.
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Author’s email: suakcrem@yahoo.com
