Algal Blooms in the Bay Area

Stella Wettan: Co-Founder

What is an Algal Bloom?

An algal bloom is the exponential growth of algae in a marine environment. Nutrient pollution, or the introduction of limiting factors such as nitrogen or phosphorous into an ecosystem, causes this phenomenon. Excessive algal growth can become problematic in multiple ways. Firstly, certain types of algae such as blue-green algae or cyanobacteria, can produce harmful toxins in the water. These types of algal blooms are characterized as harmful algal blooms, despite the fact that all types of algal blooms can have detrimental impacts on aquatic ecosystems. When algae accumulates to the point where it becomes dense enough to block sunlight from penetrating far enough into the water to reach photosynthetic organisms it lowers the oxygen levels in the water, which can create dead-zones where the marine environment no longer has the capacity to sustain most organisms.

Recently, algal blooms in the San Francisco Bay have led to unsafe concentrations of algal toxins within species that lie in bay waters such as mussels and shellfish. Four types of Algal toxins occurred most frequently. Domoic acid, often found in the Dungeness Crab, is a neurotoxin that can cause Amnesic shellfish poisoning in humans. Paralytic shellfish toxins are also found alongside Dinophysis shellfish toxins and Microcystins which are produced by cyanobacteria. UC Santa Cruz researchers found that 99 percent of the mussels that they collected were contaminated with at least one algal toxin; while 37 percent contained all four of the distinct toxins listed above.

Consuming species contaminated with algal toxins is extremely harmful to the health and safety of humans and wildlife. Generally these mussel samples exceeded the recommended concentrations of Microcystins and Dinophysis shellfish toxins for safe human consumption, Additionally, while concentrations of domoic acid and paralytic shellfish toxins were under the regulatory limits, studies have shown that chronic exposure to these toxins can lead to health concerns such as neurological damage. Because these biotoxins occur within algae, an autotrophic organism that lies on the bottom of the food web in most marine ecosystems, algal blooms usually lead to the accumulation of high levels of biotoxins in certain aquatic organisms over time until the algal bloom subsides. Until then, harmful levels of toxins can exist within the tissues of the shellfish or other aquatic organisms for long periods of time providing more opportunity for human exposure.

How will this impact the individual?

The individual person is affected if they consume contaminated mussels or shellfish from the San Francisco Bay where algal toxins are most highly concentrated. Humans might ingest these substances through the consumption of aquatic species that feed on algae. Domoic acid exposure can result in Amnesic shellfish poisoning. Symptoms within 24 hours of ingestion include diarrhea, nausea, vomiting, and abdominal cramps. In more severe cases, neurological symptoms such as dizziness, disorientation, motor weakness, headache, short-term memory loss, seizures, profuse respiratory secretions, cardiac arrhythmias, coma, and possible death, can occur. Secondly, Paralytic Shellfish poison can lead to Paralytic Shellfish Poisoning in humans. Symptoms can include tingling of the lips and tongue, tingling of the fingers and toes, loss of control of arms and legs, breathing difficulties, nausea, paralyzation of the muscles in the chest and abdomen, suffocation, and death. Thirdly, Diarrhetic shellfish poisoning results from exposure to biotoxins produced by Dinphysis, another naturally occurring type of microscopic algae. Diarrhea is the most commonly reported symptom, while nausea, abdominal pain, and vomiting can also occur. This type of poisoning is non-lethal to humans. Finally, microcystins are hepatotoxins that derive from microcystis. They are liver carcinogens with the ability to inflict immediate liver damage and fatality upon animals and liver damage among humans after prolonged low level exposure.

How will this impact the community?

Because commercial harvesting operations are not drawn to the San Francisco Bay, the sale of contaminated mussels or shellfish is less of a concern; especially considering that these operations undergo regular testing for toxins. Neither microcystins nor Dinophysis shellfish toxins, however, are regularly monitored poisons. This produces a potential threat to the safety of those who consume shellfish and mussels from the few commercial harvesters that do operate in the bay. Additionally, communities of individuals who recreationally extract aquatic organisms from the bay are at risk of ingestion of algal toxins. Finally, communities of aquatic organisms that lie higher on the food chain such as sea lions, are threatened by algal toxins that could magnify up the food chain.

How will this affect the economy?

Again, because commercial harvesting in the bay is less common, loss of sales of shellfish and other marine products is not a significant concern. Lost marine recreational opportunities, however, are a potential economic loss in this situation.

How must we take action?

Increased efforts are being made to discover the source or agency responsible for increased algal blooms. In 2011, Raphael Kudela, a researcher at UC Santa Cruz, conducted a study to monitor toxins in the San Francisco Bay. The discovery of algal toxins led to the testing of shellfish and other marine organisms used for human consumption more regularly. The Study also revealed that drought could have amplified the effects of the algal blooms. Nutrient pollution is typically caused by agricultural operations that use fertilizers, which contain these nutrients, and allow them to leak into surrounding bodies of water. Implementing regulations that require agricultural operations to be more mindful about the contamination of their fertilizers into local streams, or groundwater is most likely an effective preventative measure.