Chile Algae Bloom Disaster
Kim Tran
Intrafish
Published: 30.03.2016 15:15 Updated: 30.03.2016 16:06

Experts weigh in on potential mitigation measures, and how the salmon industry can prepare for the next outbreak.

With the numbers stacking up higher in Chilean salmon losses, salmon farmers in British Columbia feel the pain.

In the late 1980s and 1990s, salmon farms in BC and Washington state lost more than $35 million (€31.2 million) in fish due to algae blooms specifically Heterosigma akashiwo and Chaetoceros blooms, according to a North Pacific Marine Science Organization (PICES) scientific report.

The first recorded Cochlodinium sp. algal bloom led to losses of about $1.5 million (€1.4 million) in just 1999. That year, BC formed the Harmful Algae Monitoring Program (HAMP), which regularly monitors selected sites near salmon farms, tracks fishkilling blooms and educates salmon farm workers on sampling and identification of relevant marine phytoplankton, according to marine phytoplankton consultancy Microthalassia.

Canadian fish farms have dealt with several different types of algae blooms, including Chattonella, which experts are saying is the main culprit for the millions of salmon deaths Chile.

“The issue with Chile at the moment is that they have ideal conditions (El Nino) for certain algae to explode in numbers and this has impacted fish held in netpens,” Jim Powell, from the BC Centre for Aquatic Health Sciences (BC CAHS), told IntraFish. “The warm water, high salinity and good nutrients is an ideal growing condition for blooms.”

Algae blooms are naturally occurring, and with the right conditions, can become incredibly fastmoving and widespread Chile being a prime example of the speed at which the devastation can occur.

“Generally it takes less than 24 hours” to kill fish, said Raphael Kudela, a professor at the University of Southern California Ocean Sciences Department.

The spread of this algal bloom has exceeded all expectations and companies were not ready to tackle an event of such magnitude, several Chilean CEOs said.

SalmonChile, the trade association representing Chilean salmon firms, said mortalities caused by the algal bloom totaled 27 million fish, equivalent to 106,000 metric tons of fish at harvesting weight.

Chilean salmon companies are reporting multimillion dollar losses. Losses due to toxic algal blooms are reported to be in excess of $82 million (€73.5 million) to all associated marine industries, according to Bill McGraw, an aquaculture and environmental scientist and founder of New Aqua Tech Panama.

Powell said there are many factors that influence algal blooms and how quickly they spread, such as strong winds and currents.

Another factor that may cause algal blooms is what is called “anthropomorphic nutrient input” a source of nutrients for the algae likely from flows emptying out of rivers or open ocean upwelling.

Though light is the fuel for algae’s growth, the night is when it does its most damage.

“During the day, the [algae] plants grow like any other plant,” Powell said. “They consume CO2 for photosynthesis and produce oxygen. When nighttime comes, they go into nighttime photosynthesis and consume O2 from surrounding water.”

The loser, of course, is any animal requiring oxygen to survive.

Rita Horner, a research scientist with the Biological Oceanography department at the University of Washington, told IntraFish research is still a long way from fully understanding how the algae does its damage. “The actual mechanism for killing the fish is not well known,” she said. “The cells may clog the fish gills and oxygen radicals produced by the cells may strip the gills of mucus, thus causing osmoregulatory problems.”

But what the tipping point is for the concentration of algae cells to initiate a dieoff is still an unknown, and depends on a huge range of factors.

Any options?

Algae will die on its own when “it has exhausted the resources,” Powell said, but to mitigate the situation, there are a few options for salmon farmers, although nothing is a 100 percent guarantee as algal blooms are naturally occuring.

One option is to drop tarps around the pens and implement an upwelling system, which uses pipes to pump air below the net system to airlift clean, cool water into the pens and displace plankton on the surface.

The water forced into the pens will be cooler and have more oxygen to help lessen environmental factors that are favorable to algae growth.

Since algae are plants that need sunlight, Powell told IntraFish another mitigation technique is dropping a skirt that goes to the bottom of the photic zone to “form a physical barrier to keep plankton from flowing through but that stops the current too,” so companies can also airlift water or use aeration equipment to make up for lost water flow.

Bloom mitigation measures in BC are mostly limited to barrier curtains, pumping of deep water into cages and water oxygenation and aeration. The cost of maintaining equipment and fuel is estimated to be about CAD 1 million to CAD 2 million ($767,400 $ 1.5 million/€683,700 € 1.4 million) annually per company, according to the PICES report.

Other costs to aquaculture from harmful algae are lost production and bloom mitigation equipment, which cost BC salmon aquaculture companies about CAD 4 million to CAD 8 million ($3.1 million $ 6.1 million/€2.7 million € 5.5 million) annually.

As far as moving fish away from algae blooms, this “is difficult because the farms are quite large, blooms are widespread,” said Powell. Kudela told IntraFish that relocating fish is “the most effective” mitigation method “but that is only possible for the smaller fish pens (or to move the fish themselves).”

He added that other mitigation strategies include using copper sulfate, which can kill the organisms, but then leads to copper contamination. University of Washington’s Horner said one method used in Korea is to spray clay on the bloom, which flocculates the cells and causes them to sink to the bottom of the site.

Horner added that in Japan, fish growers dealt with Heterosigma blooms and moved “pens to areas where there is no bloom, but this is costly and there is always the possibility of pens being damaged and fish escaping.” Kudela said there is ongoing, active research on these blooms, how they occur, how it kills fish and mitigation options.

“Within the aquaculture industry there has also been a lot of work on minimizing impacts by using, for example, bubble curtains of air to keep the blooms from drifting into the fish pens,” said Kudela. In the end Powell stressed algal blooms are naturally occurring and will only change or worsen in the future due to climate change.

“A key point is that salmon farms do not cause blooms, they are caught up in it when it happens. Another victim of climate change,” he told IntraFish. “Harmful plankton blooms happen all over the world in freshwater and saltwater and are not new. There is an increase in the frequency of blooms and a change in the occurrence of species blooming in areas they had not been previously seen. Climate change may be contributing to these changes.”

Kudela agreed saying that fish farms need to adapt to these ocean changes brought on by “global warming and increased nutrient loading.” However, although algae growth will expand with warming ocean temperatures, there are other factors and “it’s not always clear whether global warming will favor a particular species.”
Kudela recommended companies be careful with fish pen locations.

“The best strategy is to site the fish pens in a region that is either well flushed, or not conducive to blooms,” said Kudela. “The blooms respond to warm temperatures, runoff, and nutrients, so longer term strategies are to manage nutrient loads, for example.”

Keeping a watchful eye Powell emphasized closed monitoring as the “biggest tool” to prepare for and mitigate algal blooms. “Salmon farms can send in samples to labs, look at the phytoplanton, if it’s out of whack, then you know something may happen, such as an algae bloom,” Powell said.

“These blooms are seasonal so farms and areas around the farm are monitored to give time to set up plankton mitigation. Most farm sites have the ability to look at water samples on site to allow for constant monitoring and planning.”

Horner said with proper monitoring, salmon farms can be more prepared sooner, and warned that even when the coast seems clear, farmers need to be ready to battle the next outbreak. “Some of these organisms produce cysts that sink to the sea floor and germinate later when conditions are adequate to cause a new bloom,” she said.