Algae is a fundamental contributor to ecosystems across the world; it sustains food webs in all aquatic environments in which it is found, and around 70% of atmospheric oxygen can be attributed to photosynthesizing algae. Still, there are key properties of algae that can prove dangerous when it is present in excess, and they can threaten to reverse the same benefits to ocean life that they usually provide. 

Santa Barbara County has experienced a series of harmful algal blooms increasing in frequency and intensity over recent years, culminating to be the most critical this summer for ocean life. 

Harmful algal blooms (HABs) are the result of the explosive growth of phytoplankton, or microalgae. Two types of phytoplankton — dinoflagellates and diatoms — are responsible for most of the algal blooms that are ecologically and environmentally harmful when they are allowed to accumulate to certain levels. These blooms cause the ocean surface to adopt a red color, which has given the saltwater blooms the name “red tides.”

HABs’ threat to ocean life derives from the algal emission of the neurotoxin domoic acid. When ingested, this compound primarily targets the hippocampus in the brain, inhibiting long-term memory and spatial navigation. Direct consumption of algae-producing domoic acid by filter feeders is generally inconsequential, as the level of toxin intake is too low to incur any danger. 

However, greater consumption of filter feeders by large organisms such as sea lions and dolphins can result in detrimental bioaccumulation, ultimately leading to domoic acid poisoning. The intensity of poisoning increases with the amount consumed, ranging in consequence from nausea and lethargy to seizures, paralysis and death. In humans, poisoning is most often attributed to shellfish consumption and results in similar concentration-based symptoms.

Regional organizations, such as the Channel Islands Marine & Wildlife Institute (CIMWI), have been engaging in record numbers of domoic acid-related rehabilitations since the bloom’s emergence in June. “The highest number of patients CIMWI has ever had in care at one time is 60,” a CIMWI Instagram post from July stated. “That was in 2019 when we rescued a total of 182 seals and sea lions. In only 6 months of this year, we have already rescued 172!”

The California coastline has experienced HABs for decades, but worsening environmental conditions have resulted in increasingly dire consequences for more recent blooms. “Climate change and rise of nutrient pollution are environmental circumstances that are potentially causing HABs to occur more often and in locations not previously affected,” CIMWI’s website stated.

Particularly noteworthy in the 2023 algal bloom is its increased concentration farther offshore from the California shoreline, the National Oceanic and Atmospheric Administration (NOAA) said. This primarily affects the species of ocean life impacted most by domoic acid poisoning, as increased numbers of dolphins have joined the large number of sea lions that normally constitute the annual casualties. 

Current research into the causes of algal blooms finds that warmer temperatures characterizing the summer season lead to increased water temperature which is beneficial to HABs. However, the extent of individual factors working in tandem to generate blooms is still being determined. “While we know of many factors that may contribute to HABs, how these factors come together to create a bloom of algae is not well understood,” the NOAA said in an article on why harmful algal blooms occur.

One widely agreed upon contributor to HABs perpetuation is nutrient pollution, in which fertilizer, sewage and industrial runoff from the mainland flow into the ocean, increasing nitrogen and phosphorus levels. Microalgae benefit from these chemicals that they use as fertilizer, resulting in bursts of accelerated algal growth. Other factors under consideration include water circulation and extreme weather events.

As summer begins to wind down, it is hoped that this year’s HABs will subside with minimal additional losses to marine life in the Santa Barbara area, as well as relief for conservation organizations, including the CIMWI. 

Research towards mitigation of HABs is forthcoming and especially necessary as global climates exacerbate. The NOAA is at the forefront of these efforts: “NOAA scientists continue to monitor and study HABs to determine how to detect and forecast the location of the blooms,” according to NOAA’s website. “The goal is to give coastal communities advance warning, so they can adequately plan and deal with the adverse environmental and health effects associated with a harmful bloom.”