Bloom. It doesn’t sound that bad. The word may conjure up the image of spring crocuses popping up out of the ground. But start talking about harmful algal blooms, Pseudo-nitzschia, and domoic acid poisoning and people begin to realize that something more threatening is happening. Last week during the annual American Geophysical Union Fall Meeting (AGU 2015), researchers warned that abnormally warm Pacific waters, commonly referred to as the “blob,” were linked to a record-setting harmful algal bloom outbreak along the west coast of the United States. To make matters worse, this outbreak could be exacerbated by the current El Niño event.
“We could be going into the third year in a row of very toxic conditions because of this El Niño event,” said Nate Mantua of the NOAA Southwest Fisheries Science Center.
The blob emerges
In late 2013 and early 2014, Nick Bond at the University of Washington discovered the “blob,” an area of water with sea surface temperatures ~3°C above normal hovering in the North Pacific Ocean. The blob can be traced to an atmosphere high-pressure system, or ridge, that lingered over the Pacific from July 2011 to June 2013. The ridge slowed down mixing of the ocean waters and produced fewer and weaker storms, which eventually led to the rise of the blob and is linked to the California drought.
In the six to nine months that followed, the ridge shifted to the east and landed along the west coast of the U.S., right in time for a seasonal upwelling event. Upwelling events bring cold, nutrient-rich waters to the surface along coastlines and create rich ecosystems, essential for productive fisheries. In 2015, however, some researchers contend that the upwelling event along the West Coast was weak and the cool waters could not compete with the massive warm blob. Yet it still could have pulsed nutrients to the surface, adding to anthropogenic nutrients available, and created an environment with just the right conditions to set off a massive algae bloom.
The blob’s offspring
As early as May 2015, fisheries along the West Coast started to close because of an outbreak of the toxic Pseudo-nitzschia, a marine diatom that exploded to record levels. Economically important species, such as razor clams, Dungeness crabs, and anchovies all tested above the regulatory limit for the toxin domoic acid, which can trigger amnesic shellfish poisoning. According to the Centers for Disease Control (CDC), amnesic shellfish poisoning can cause a range of symptoms, including gastrointestinal distress, memory loss, and death.
Harmful algal blooms are not uncommon, but they are hard to predict. Pseudo-nitzschia likes warm water, prefers excess nutrients like urea, and can be found below the surface water layers. As coastal ecosystems have come under pressure from human population growth and development — leading to increased anthropogenic nutrients, runoff, and other stresses on the marine environment — the likelihood a harmful algal bloom increases. Layer on top a warming climate and rare events like the warm blob, and the system could be under enough pressure to knock it off its balance. And stumbling is what many species along the West Coast are doing.
The impacts of the recent harmful algal bloom have been felt from Alaska to California. In unpublished research, Raphael Kudela from the University of California Santa Cruz (UCSC) found anchovies, a commercially important species, with toxin in their heads, guts, and surprisingly in their bodies. The filet concentration reached 35 parts per million, which is over the regulatory limit of 20 parts per million for safe human consumption. Anchovies are a common feeder fish, and once other species eat them, the domoic acid moves up the food web. During his survey Kudela found contamination in all fish samples, including mussels, anchovies, razor clams, rock crabs, and Dungeness crabs, to name a few. “It has gotten so far in the food web that marine mammals are facing long-term consequences, and may actually be getting brain damage,” said Kudela during a press conference at AGU 2015.
How long domoic acid remains in the environment, including in sediments, is a curiosity for ecologists. The research Kudela presented at the AGU Fall Meeting showed that toxin levels in Dungeness crabs increased even after the bloom subsided in October. Because the toxin can persistent in sediments, invertebrates often see higher levels of toxin, often ten times more than what is found the sediment itself, according to Kudela.
Mass mortality events have been attributed to harmful algal blooms in the past. In 2011, marine ecologist and PLOS ONE author Dr. Laura Jurgens found that populations of purple urchins and six-armed sea stars were decimated along 100 km of California’s coastline in 2011. The researchers could not ascribe the mass die-off to one specific cause, but deduced it was probably a set of non-exclusive processes, including the “most likely” driver of a harmful algal bloom.
In addition to spawning a colossal harmful algal bloom outbreak, the warm blob has caused much turmoil in the ecosystem. For example, ocean sunfish, which look like giant heads squeezed through iron bars, were found in the Gulf of Alaska although they more commonly reside around Hawai’i. Large populations of Cassin’s Auklets, a stubby, dark seabird, were found dead or starving on Pacific Northwest beaches. Moreover, juvenile salmon migration was impacted, threatening their survival rates.
The blob’s legacy
Left in the wake of the warm blob and harmful algal bloom outbreak, sea lions, seabirds, and other marine species have faced death and starvation. The impacts on the West Coast ecosystem are unlikely to be alleviated anytime soon. One of the largest El Niño events on record is currently underway and is anticipated to remain strong through the winter before weakening in late spring to early summer. El Niño events shift extremely warm tropical Pacific waters eastward, and then currents move this water up the West Coast. Considering the warm blob is lingering, these elevated temperatures in the coastal waters could be exacerbated by El Niño; thus creating ripe conditions for another, possibly sustained or larger, harmful algal bloom outbreak in the coming year.
“El Niño is an important part of the story, not for how we got here, but where we are headed in the next few months,” said Mantua.
Bond, N. (2014): The Blob: Warm Water off the Coast of the PNW and What it May Mean for Our Summer Weather. OWSC Newsletter, Vol. VIII, Issue 6, http://www.climate.washington.edu/newsletter/2014Jun.pdf.
Bond, N., M. F. Cronin, H. Freeland, and N. Manua (2015): Causes and impacts of the 2014 warm anomaly in the NE Pacific. Geophysical Research Letters, doi:10.1002/2015GL063306.
Food and Drug Administration (2011): Fish and Fishery Products Hazards and Controls Guidance – Fourth Edition, Chapter 6: Natural Toxins, http://www.fda.gov/Food/GuidanceRegulation/GuidanceDocumentsRegulatoryInformation/Seafood/ucm2018426.htm.
Jurgens, L. J., L. Rogers-Bennett, P. T. Raimondi, L. M. Schiebelhut, M. N. Dawson, R. K. Grosberg, and B. Gaylond (2015): Patterns of Mass Mortality among Rocky Shore Invertebrates across 100 km of Northeastern Pacific Coastline. PLOS One, doi:10.1371/journal.pone.0126280.
Kudela, R. (2015): Spread of algal toxin through marine food web broke records in 2015. American Geophysical Union Fall Meeting, https://fallmeeting.agu.org/2015/press-item/spread-of-algal-toxin-through-marine-food-web-broke-records-in-2015/.