This is a really good article that explains the problem with bacteria and their ability to move up and down within the water column because their cysts remain in the sediment (at the bottom of the ocean). Detecting them and their toxins can be impossible so mitigating the risks is equally challenging. If your not testing the sediments then I don’t feel you are even trying to determine whether you have a problem. I have read cysts can be found in up to 15cm of sediment. Nobody who has had to deal with a toxic bloom has found answers that I am aware of including Toledo where 500,000 were told not to use their water in 2014 and water treatment managers have been forced to resign for doing a great job in my opinion. Learn more about cyanobacteria, blue green algae, harmful algal blooms, and cyanotoxins. Click here to read the full article or an excerpt below.
A harmful algae bloom (HAB), frequently also known as brown or red tide, is a rapid increase in the population of algae in the water.
There is a higher risk of algae contamination when there is no wind, when there are more solar radiations and higher water stratification.
El Nino, which contributed to increase temperatures in 2015-2016 has declined since last July .
The summer season in Chile, which goes from December to March, is generally characterized in southern regions by higher solar radiation, water temperatures and intervals of lower wind.
“Now we are entering a moment of higher risk. Until March we will be in a risky period, because the algae that have remained in the sediments under the form of cysts, could return to proliferate,” Adolfo Alvial, regional director of Production Development Corporation (Corfo), Adolfo Alvial, told Undercurrent.
“It could happen now or in the coming spring – summer seasons, we don’t know. But what we know is that these algae can remain as resistant spores and can proliferate again when the environmental conditions are favorable. This alga is very resistant and when it finds a good condition in the water column, returns to bloom. The point is that the recent big event expanded the area of distribution of these resistant cysts in the sediment towards the north in Los Lagos region,” Alvial also told Undercurrent.
“A new contagion is really unpredictable,” added an industry source.
Monitoring and mitigation and logistics to improve bloom management
Chilean firms are preparing to face another contagion in the coming months.
However, there are no definitive solutions to contain a bloom as powerful as the one that affected Chile in 2016.
The industry is implementing monitoring systems to forecast toxic proliferation, based on remote systems, satellite information and good dynamic models. Monitoring should help to understand the impact and mitigate the effect.
“Today it is key to improve monitoring systems, in order to detect and even forecast in the future the HAB and the areas of major risk,” Alvial said.
Firms are also currently testing and implementing a series of mitigation measures to contain the impact of a new bloom.
Those measures include logistic emergency plans, new sea cages design and setting, aeration and oxygenation and airlift systems, which move the water and create micro-bubbles to lower concentration of algae.
Plastic curtains and other sorts of barriers around production centers to keep algae away. A technology employing clay which bind algae causing sedimentation is also being explored.
Those technologies might not be sufficient to stop a contagion, but help to gain time to quickly harvest the fish or move it away from affected areas.
“We are working hand by hand with the Chilean authority, Sernapesca, in a complete mitigation plan for the industry, including talks with all the supply chain involved in the organic material disposal,” an executive at one of the largest Chilean producers told Undercurrent.
Medium-term engineering work to allow cages to move vertically deeper in the water, flooding them or moving cages to a deeper offshore waters, are also being developed, although it is still at a very initial stage.
Generally, algae bloom at 2-3 meter depth and move to 7m depth in the night, but there are still relatively high levels of concentration of algae both above and below the focus. With new engineering, cages could be moved below 15m.
“Having an adequate logistics to deal with the situation and move dead fish quickly is also necessary, because there weren’t sufficient boats, processing plants or places to put it last February,” Alvial said.
“Corfo has the tools to co-fund projects to improve tools to monitor, forecast and mitigate HAB impacts on the aquaculture,” Alvial added.
The risk that algae bloom contamination will repeat more frequently is high, because of the gradual increase in water temperatures observed during the last years, according to industry sources.
“Developing technologies that will help the industry to cope with this challenge is key. More oceanic aquaculture and centers of production that can be moved deeper in the water might be strategic in the future,” Alvial said.