Understanding the Science Behind Algal Blooms

The foundation of this issue lies in a natural process called upwelling. Along the western coasts of continents, winds and currents drive surface waters offshore, allowing nutrient-rich deep-sea water to rise and replace them. This influx of nitrogen and phosphorus acts as a fertilizer for phytoplankton – microscopic plants that form the base of the marine food web. While a moderate supply of these nutrients is essential for a healthy ecosystem, an overabundance can trigger explosive algal growth, leading to blooms.

These blooms aren’t always harmful. However, when they become excessive, they can deplete oxygen levels in the water, creating “dead zones” where marine life cannot survive. This process, known as hypoxia, results in the grim spectacle of mass fish die-offs, coating shorelines with decaying organisms. But the danger doesn’t end there. Certain species of algae produce powerful toxins that can accumulate in shellfish, fish, and even become aerosolized in sea spray.

The Threat of Neurotoxins: Domoic Acid and Beyond

One of the most concerning toxins is domoic acid, produced by the algae Pseudo-nitzschia australis. This neurotoxin causes amnesic shellfish poisoning (ASP) in humans, a condition that can lead to short-term memory loss, neurological damage, and, in severe cases, even death. ASP is notoriously difficult to detect, making it a particularly insidious threat.

Other algal toxins, like brevetoxins, can cause respiratory irritation and neurological effects. These toxins can become airborne through sea spray, posing a direct risk to beachgoers and surfers.

Impact on Surfers: A Direct Line of Exposure

Surfers, who spend extended periods immersed in coastal waters, are particularly vulnerable to the effects of HABs. Grace Adams, Executive Director at Roundhouse Aquarium in Manhattan Beach, explains, “Prolonged exposure to harmful algal blooms can pose several risks. While hypoxia primarily stresses marine life, the greater concern for people is exposure to algal neurotoxins which can become aerosolized in sea spray or enter the body through inhalation, ingestion, or contact with contaminated water.”

Even without consuming contaminated seafood, surfers can experience respiratory irritation, eye discomfort, headaches, dizziness, and short-term memory disruption from repeated exposure to these toxins. The cumulative effect of these exposures, especially downwind of affected breaks, can be significant.

What does this mean for the surfing community? It means being informed, vigilant, and proactive in protecting their health. Are we adequately prepared to monitor and mitigate these risks as HABs become more frequent and widespread?

The increasing frequency of these events is prompting a global response. One of the United Nations’ “Decade of Ocean Science for Sustainable Development” initiatives focuses on leveraging satellite data to better track and understand these challenges, aiming for a “clean, safe, and accessible ocean” by 2030.

Recent advancements, such as EUMETSAT’s Copernicus Sentinel-3 and its Ocean and Land Colour Instrument (OLCI), are providing valuable insights into the dynamics of algal blooms, helping scientists pinpoint where and why they occur.

Related: 110 Million Pounds Of Plastics Collected From World’s Oceans

Learn more about Harmful Algal Blooms from NOAA

Read about the rise of HABs from the Woods Hole Oceanographic Institution

Frequently Asked Questions About Harmful Algal Blooms

• What are harmful algal blooms?

  Harmful algal blooms (HABs) are overgrowths of algae that can produce toxins harmful to humans, marine life, and the environment. They occur when specific conditions, like excess nutrients and warm temperatures, promote rapid algal growth.

• How do algal blooms affect marine life?

  Algal blooms can deplete oxygen in the water, suffocating fish and other marine organisms. Toxic blooms can directly poison marine animals, leading to mass die-offs and disrupting the food chain.

• Can humans get sick from algal blooms?

  Yes, humans can become ill from consuming contaminated seafood, such as shellfish containing domoic acid. Exposure to airborne toxins can also cause respiratory irritation and neurological symptoms.

• What causes an increase in harmful algal blooms?

  Several factors contribute to the increasing frequency and intensity of HABs, including nutrient pollution from agricultural runoff, climate change, and altered ocean currents.

• How can surfers protect themselves from algal bloom toxins?

  Surfers can minimize their risk by checking local health advisories, avoiding surfing in areas with visible blooms, and wearing protective gear like a rash guard to reduce skin contact with the water.