24 JUNE 2022 • WORLD AQUACULTURE • WWW.WA S .ORG finfish species in aquaculture. This program aims to provide aquaculture facility operators with a minimum of two weeks advanced warning of dangerous levels of toxic phytoplankton. The AQPMN is partnered with the East Coast Shellfish Growers Association and The Nature Conservancy’s Shellfish Growers Climate Coalition on this initiative. This partnership will allow rapid expansion of the program into aquaculture farms already dealing with environmental and water quality issues. Additionally, NCCOS has multiple HAB Forecasting Systems that offer short-term (hourly to weekly) forecasts to identify potentially harmful blooms, their location, size, trajectory and respiratory risk, as well as longer-term seasonal forecasts that predict the severity of HABs for the bloom season in a particular region. These forecasting systems are currently available for Texas, Florida, the Gulf of Maine and Lake Erie. The systems incorporate satellite and/or field collected data to monitor conditions daily and issue regular forecasts of blooms. Forecasting systems are currently under development for Chesapeake Bay, Alaska and Lake Okeechobee regions. C-Harm (California Harmful Algae Risk Mapping) HAB Forecasts are part of the Integrated Ocean Observing System (IOOS) and generate nowcasts and forecasts up to three days in advance of a HAB caused specifically by the species Pseudonitzschia in California and southern Oregon. Satellite observations of ocean color, surface salinity, temperature and currents are used to measure phycotoxins, specifically domoic acid, to predict the likelihood of a bloom in these regions. Blue Lion Labs, a Canadian-based startup, in collaboration with the marine technology group OTAQ, located in the UK, is developing artificial intelligence technology that will be used to create a fully-automated EWS for detecting HABs using imaging technology to identify individual phytoplankton to the species level. These data will then be analyzed using a variety of ML methods to deliver real-time data on the species composition of the bloom. This level of detail will help operators implement the most efficient mitigation techniques. This partnership hopes to achieve commercialization of their product in the near future. Innovasea’s cloud-based software can deliver real-time data on harmful plankton concentrations. This software uses data from a suite of aquaMeasure sensors to track spatial and temporal trends, providing a better idea of which plankton species are likely to appear, and how species distributions and concentrations change over time. In the future, these data can be used to predict the size and location of blooms. Although this technology is not yet predictive, an EWS is currently under development. Mitigation Strategies After receiving an alert regarding an onset of a HAB, there are operational procedures that facility managers can implement to protect living assets. As is always the case, mitigation methods are extremely site- and facility-specific and can vary based on location, equipment used and specific characteristics of the HAB itself — size, shape, depth and toxin levels. In some cases, facility managers alerted to a potential HAB threat may react by harvesting stock earlier, taking stock from an unaffected area or, when feasible, towing net pens to a refuge area, a common mitigation strategy practiced worldwide. Towing net pens is challenging and stock can be lost as a result of ripped nets and loss of cages fromwave or towing forces beyond the design tolerance of pens. Employing boats with sufficient towing capacity to move larger net pens can also be very costly. Additionally, identifying suitable refuge areas that do not interfere with marine navigation or present unmitigable risk to infrastructure or stock can prove challenging (Anderson et al. 2001). Depending on the net-pen technology used, pens could also be lowered and raised in the water column to avoid contact with the HAB using airlift pumping technology. For example, Innovasea’s Evolution pens and SeaStation pens (Fig. 5) can float on the surface when there are no environmental threats such as rough seas, storm surge or large algal blooms but then can be submerged to a pre-determined depth to avoid these threats. The ability of these net pens to sink to a regulated depth allows them to potentially avoid impacts to stock caused by HABs. Such net-pen technology allows operators to avoid the bloom, reducing the risk of physical injury to fish or to avoid algae-related hypoxia. Less technologically advanced net pens often deploy perimeter skirts or tarps that are suspended vertically around the outside perimeter of the net pen to create a barrier between the sea and the stock inside in the pens. This method is typically practiced in tandemwith other mitigation methods such as pump aeration to attempt to reduce fish kills. Aeration and oxygenation systems can also be used to mitigate HABs. Aeration of net pens can help thin out and disperse large masses of algae when a bloom is detected. Aeration also improves water quality and increases water circulation, which adds oxygen and can help reduce dead zones inside of net pens. Examples of aeration systems currently in use to mitigate HABs include aquaControl technology from Innovasea, bubble tubing technology fromCanadianpond, which can be used to create bubble curtains to deflect incoming HABs, as well as diffusers such as SalmoAir that create constant circulation of water and air inside net pens. Additionally, nanobubble technology from Moleaer provides multiple operational benefits for aquaculture facilities including HABmitigation. Using nanobubbles, which are 2,500 times smaller than a grain of salt, as opposed to conventional aeration methods, allows for more efficient gas transfer and oxygenating areas more efficiently by allowing bubbles to stay in the water column for weeks without off gassing at the surface. FIGURE 5. The Evolution pen (left) and the SeaStation pen (right) from Innovasea that can be submerged to a pre-determined depth to potentially avoid physical injury to the stock or algae-related hypoxia from a HAB.
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