Harmful algae cause several marine species to wash out on West Coast beaches

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Tons of crayfish crawl out of the sea at Elands Bay due to the red tide.
Tons of crayfish crawl out of the sea at Elands Bay due to the red tide.
Facebook/Cederberg Local Municipality
  • A harmful algae known as red tide has been causing marine life to wash up along the West Coast. 
  • The Department of Environment, Forestry and Fisheries has put a contingency plan in place and role players are on standby.
  • Some of the algal species are harmful because they contain toxins, which are poisonous to humans.

Rock lobsters, octopus, white mussel and some fish species have washed out on West Coast beaches as "red tides" buildup in the St Helena Bay region. 

According to the Department of Environment, Forestry and Fisheries (DEFF), a harmful algal bloom, called red tides, has been building up in Elands Bay on the West Coast and has caused the marine species to wash out.

DEFF spokesperson Zolile Nqayi said a northwesterly wind was keeping the algal bloom concentrated in the bay.

"Notwithstanding the red tides, West Coast rock lobster catches are still good and this indicates that oxygen levels are still high. The New Moon spring tide occurred two days ago, thus limiting the possibility of a mass stranding within the next 10 days," Nqayi said. 

The DEFF has activated its West Coast Rock Lobster Contingency Plan, issued a Situation Yellow alert and placed all government role players on standby.

In terms of the contingency plan, the DEFF is the lead department, supported by the following organs of state: the West Coast District Municipality, the Cederberg municipality, the South African Police Service, the South African National Defence Force and the Western Cape provincial administration.

"These role players are currently preparing for a Situation Red because beaching has taken place and there is a possibility that there may be beaching in excess of 10 tons at a single or multiple localities in the area," Nqayi said.

"As is often the case in summer and late summer, there has been a buildup of large red tides in the greater St Helena Bay region over the past few weeks. These blooms of phytoplankton presently extend 50km to 60km in the vicinity of Elands Bay, Lamberts Bay and Doring Bay."

What are red tides?

In a statement, the DAFF said red tides are a natural phenomenon in coastal waters, caused by a dense accumulation of microscopic algae. Some of the algal species are harmful because they contain toxins, which are poisonous to humans.

Poisoning may either take place through the consumption of seafood that is contaminated by toxic algae, or by toxic aerosols or water bound compounds that cause respiratory and skin irritation. Other red tides cause harm through the depletion of oxygen (anoxia), which affects all marine creatures and can lead to mass mortalities of entire marine communities or mass walkouts of rock lobsters that try to escape the anoxic conditions the statement read.

READ | Whales, dolphins and penguins among 75 marine species killed by ships - report

Red tide occurrences can therefore have major environmental, as well as societal implications, with knock-on effects on coastal economies. Fisheries and aquaculture industries suffer from the episodic mortalities of stocks caused by red tides, while poor water quality and foul smells associated with these occurrences affect coastal tourism.

Red tides are particularly common in the productive West Coast upwelling regions, such as the Benguela, California, Humboldt, Canary and Somali upwelling systems.

In the Benguela upwelling region off the West Coast of southern Africa, red tides have periodically led to rock lobster strandings. The most famous examples are the strandings of hundreds of tons of rock lobsters in Elands Bay in 1997 and 2000.

In 2014, an extensive and long-lasting red tide occurred for the first time along the South Coast, extending from Knysna to beyond Port Elizabeth, causing wide-scale mortalities of fish.

These blooms are dominated by a group of phytoplankton known as dinoflagellates and their inshore accumulation, particularly during periods of calm, often leads to their decay and the subsequent development of low oxygen conditions which cause marine mortalities.

Such mortalities were observed on the beaches of Elands Bay earlier on Sunday and with the prediction of light westerly winds over the next few days, the risk of further mortalities is high.

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