Red Tide

Red tide is a curse when living on the West Coast. The water changes colour, sea creatures die and those who can escape litter the beaches. The beaches are sown with stinky, dead animals and everybody is too scared to eat seafood...

But red tide is actually a natural and seasonal phenomena which occurs widely off the coast of South Africa and Namibia as a result of nutrient enrichment from intense upwelling. (see the previous blogpost about water too cold to swim in). Most red tides actually helps the growth of plankton.  It is only certain red tide that is harmful. They are called HAB`s (Harmful Algal Blooms).  And these are the red tides we read about in the newspaper - HAB`s. It seems a more occurring occasion - these HAB`s.  Scientists cannot say why. Some say it is because of the pollution in our rivers by our farming activities - pollution from fertilizer and hormones which stimulates algae growth. Others blame the changing weather patterns or say that it isn't occurring more, it is just that we are more aware of it happening. Be it as it may, red tide can have catastrophic results.

There seems to be different causes and types of phytoplankton (dinoflagellates, diatoms and ciliates) which leads to red tide.  The most common one is where large phytoplankton blooms resulting from the upwelling of nutrient-rich water eventually die and sink to the ocean floor, where their decomposition by bacteria depletes oxygen in the water.  Red Tide  arises when this low oxygen water moves to the coast by upwelling. The water changes colour to red, yellow, orange, brown and even purple. This is when the invertebrates like rock lobsters walk out in the shallow water or on the beach.

In 1997 the largest ever stranding of rock lobster on the west coast followed the decay of a massive bloom of dinoflagellate, Ceratium furca, at Elands Bay.  The total loss was estimated to be 2000 ton.

Some types of red tides cause massive dying of abalone, white mussels and black mussels.  Other HAB`s are not harmful to mussels but are stored in mussels and are then poisonous to people eating them.  Mussels can store these toxins for up to four months.  Before eating shellfish contact the Red tide Hotline at 021 402 3368.  A recorded message will tell you whether it is safe to collect and eat shellfish.

Fish and crayfish die because of oxygen deprivation during red tide, or because their gills are clogged up by rotting organisms. After the aerobic bacteria used up all the oxygen in the water for the rotting process, the anaerobic bacteria takes over.  These bacteria get their energy by converting sulphur into toxic hydrogen sulphide gas, which smells like rotten eggs, changes the water to black and poison any other organisms still living in the water.  A black tide like this once hit St Helena Bay and destroyed 95% of all marine life.

Makes you think, doesn't it?  Red tide is supposed to be a natural process - is there a natural reason why it should be so destructive? Or is this just one more example of the creation groaning in the pain of sin as Romans 8 teaches us?