Algal blooms: How aquaculture can fight back against these harmful & unwelcome intruders
By 2050, the planet's population is expected to grow by 2 billion. That means an increased demand for protein, and that presents an enormous opportunity for aquaculture because it can be both sustainable and scalable.
According to the United Nations, aquaculture is the world's fastest growing food sector, currently accounting for more than 50 percent of the fish consumed by humans. Global fish consumption increased at an average annual rate of 3.1 percent between 1961 and 2017. That's almost double the rate of population growth from that same period and is higher than the growth of any other animal protein.
Unfortunately, climate change is threatening the future of the fish farming industry, particularly ocean-based farming and the cultivation of any species that relies on wild fisheries for feed. The effects of climate change are likely to bring more intense and frequent flash floods, tropical cyclones, and extreme heatwaves, but the warming that much of the planet is already experiencing is by far the biggest threat to the industry.
This is due to the:
• Effects of warming on the farmed species.
• Effects on areas that are suitable for fish farming.
• Impacts on wild species that are currently used to produce feed.
But perhaps the most complex threat from climate change is how it's fuelling the frequency and intensity of harmful algal blooms. Algae – or phytoplankton – are microscopic species that support the oceans food web.
However, under the right conditions, their populations can grow exponentially in a short period of time. This can have negative consequences on surrounding organisms because algae blooms can deplete oxygen levels, produce neurotoxins that can harm or kill fish directly, or damage the gills of fish as they pass over them.
An unprecedented bloom
Blooms occur primarily in coastal regions where most farms are situated, so farmers often invest in significant monitoring and mitigation techniques to protect their stocks. But this is becoming increasingly difficult. What was once a small, seasonal issue is rapidly becoming a full-time monitoring effort that is costly and resource intensive.
For example, in 2015 an unprecedented bloom of Pseudo-nitzschia australis, known for producing the neurotoxin domoic acid, occurred along the West Coast of Canada and the United States. This bloom was fuelled by a large warm water anomaly, colloquially named 'the blob,' that produced ideal growing conditions.
This was the first time a Pseudo-nitzschia bloom caused harmful effect to both shellfish and finfish operations in the region – and affected marine mammals. Super blooms such as this one, demonstrate the potential severity of toxic plankton events that could become more common in the future.
So, what can farmers do about worsening plankton issues? The first step is simply monitoring water conditions. Today's environmental monitoring technology allows for fine-scale monitoring of oxygen, temperature, turbidity, chlorophyll and other factors in every pen. Research has shown that these conditions can vary across a single farm.
With significant impacts from climate change happening in real time and expected to worsen, it's critical that farmers monitor water quality to collect baseline data and observe changing conditions to determine the impact on their production cycles.
Harmful algal blooms are directly linked to environmental conditions, so collecting consistent and reliable environmental data will provide valuable insights into how changes in water quality are impacting when and where blooms form.
Better understanding the issues
Plankton data management is also proving necessary for any farmer who wants to better understand the issues they're experiencing on their farm. Knowing what happened last year is no longer enough. Looking back over the last five or even 10 years – and being able to see how multi-year patterns are emerging – is critical to managing algae blooms in the short term.
In the long-term, these data sets are unique and extremely valuable, and they can be used to develop machine learning algorithms that can help with forecasting and prediction models. But a better understanding of a problem doesn't actually solve it.
For that, mitigation technology is required, and more farmers are implementing aeration and oxygenation systems that can be highly effective when used correctly. In addition, there's an ongoing shift in the industry toward semi-enclosed sites, and these systems require oxygen injection in order to provide a suitable habitat for fish.
Producers are quickly realising that aeration and oxygenation systems allow them to not only control the environment when problems arise, but by super saturating the environment with oxygen they can shorten grow-out cycles, which has major benefits in terms of environmental impact and production costs.
Protecting against unknown threats
Oxygen injection and aeration systems are a significant investment and can be costly to work – in particular against harmful phytoplankton where systems are often left running around the clock to protect against unknown threats.
Automated and data-controlled mitigation systems like Innovasea's aquaControl are the future of this technology and ensure that systems are operating at the highest efficiency level and only when necessary.
Armed with a first-of-its-kind digital control panel, aquaControl's air-flow valves can now be automatically adjusted via software control instead of requiring someone on-site to manually open and close mechanical valves.
In addition, aquaControl will use environmental data and incoming plankton information collected on the farm to automate the aeration system and determine how much air or oxygen to bring into each pen and when to turn diffusers on and off.
There's no question that climate change is impacting water quality around the globe and creating challenges for ocean-based fish farming. The increase in harmful algae blooms is not only a problem for ocean farmers, but poses a threat to freshwater systems, wild shellfish, fish, and marine mammals that often occupy the coastal regions most heavily impacted by HABS.
Woods Hole Oceanographic Institution released a special report earlier this year outlining the complicated nature of HABs. It highlighted the importance of environmental monitoring and capturing data sets that directly identify species and their concentrations – the exact data sets many farmers are already collecting for their operations.
These data sets are extremely valuable and collaboration between industry and research groups is a natural path to better understand these complex phenomena.
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Article contributed by Jennie Korus, Aquaculture Scientist, Innovasea, Canada