An algal bloom off the Long Beach coast.
An algal bloom off the Long Beach coast. (Brittany Murray / Press Telegram)

LONG BEACH - It's a common seasonal feature, but swimmers and fishermen should use caution.

That's the advice by health officials on the annual appearance of a bright green algal bloom, surfacing along the city's shoreline.

Swimmers should attempt to avoid direct contact with the floating film, but if they do touch it, they should shower the matter off, according to Long Beach Health Department environmental health specialist Nelson Kerr.

Fishermen should also use caution when seeking mussels, since toxins can increase with the warmer weather, Kerr added. Only commercially harvested mussels, he added, are considered safe during the algal bloom season - between May and October.

"Most are not harmful, but some are," Kerr said, when advising that only commercially harvested shellfish should be used.

Fish are not contaminated by the algal blooms, Kerr said.

Algal blooms occur in marine and freshwater environments.

Kerr said the blooms are the reult of increased temperatures.

Algal bloom concentrations may reach millions of cells per milliliter, according to website details.

Colors observed are green, yellowish-brown, or red.

Bright green blooms may also occur.

Some algal blooms are the result of an excess of nutrients, particularly phosphorus and nitrogen, into waters and higher concentrations of these nutrients in water cause increased growth of algae and green plants.

As more algae and plants grow, others die.

This dead organic matter becomes food for bacteria that decompose it.

With more food available, the bacteria increase in number and use up the dissolved oxygen in the water.

When the oxygen decreases, many fish and aquatic insects cannot survive.

At the high cell concentrations reached during some blooms, the toxins may have severe biological impacts on wildlife.

Algal blooms composed of phytoplankters known to naturally produce biotoxins are often called Harmful Algal Blooms, or HABs..

For more information about the topic Algal bloom, read the full article at Wikipedia.org.