Harmful Algae Blooms and Aquaculture - Presentation References - Jennie Korus AQUACULTURE SCIENTIST | INNOVASEA
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Harmful Algae Blooms and Aquaculture – Presentation References Jennie Korus AQUACULTURE SCIENTIST | INNOVASEA
Thank you for tuning in to the discussion of harmful algae blooms and salmon aquaculture.
This handout offers additional resources and links to research articles that this presentation
was based on. I hope you enjoyed the presentation. Please feel free to reach out if you have
any questions or need additional information.
-Jennie Korus
Aquaculture Scientist
jennie.korus@innovasea.com
As our planet reaches a population of 7.7 billion people, which we expect to grow by
more than 25% to 9.7 billion by 2050 (UN, 2019), it becomes increasingly critical to invest in
solutions that enable us to feed the planet sustainably.
When we take stock of our global marine fisheries, the trends we observe are
extremely concerning. The
percentage of overfished and fully
fished stocks are increasing, and
the number of available, non-
exploited stocks are decreasing
(FAO, 2014).
Our wild fisheries have been
at maximum capacity for the last
couple decades and to meet the
increasing demand – aquaculture
production has rapidly increased.
Since 1995, overall fish production Figure 1: Contribution of aquaculture in total production of aquatic
animals (FAO, 2020)
has grown by 75% (101.8 million tons
in 1995 to 178.5 million tons in 2018).
In 1995, aquaculture made up 14% of this production (14.9 million tons) compared to 2018,
where aquaculture made up 46% (82.1 million tons). (FAO, 2020). It’s key to invest in
sustainable fish production now as our current wild fisheries cannot support continued
Figure 2: Production of Atlantic Salmon (Salmo salar) in millions of tons from 1980 to 2015. (Cultured Aquatic Species
Information Program, 2020)
The Ongoing Challenge of Plankton Monitoring and Mitigation | 1
growth as we look ahead to managing food production for exponential population increase.
(Bostock, 2011).
If we look at the salmon industry specifically, there has been significant and sustained
growth since the 1990s, see figure 2 (Cultured Aquatic Species Information Program, 2020).
Not only has its production increased but the demand has increased due to the expansion of
the seafood-consuming middle-class. Urbanization and improved disposable income have
been fueling demand in this market (FAO, 2020).
The Threat of Algae Blooms
One of the challenges salmon aquaculture farmers are facing are harmful algae
blooms (HABs). HABs are natural phenomenon that occur each spring and fall, typically in
coastal regions. Algae or phytoplankton are restricted to the surface layer – often referred to
as the mixed layer - and they bloom when certain conditions occur simultaneously.
First, in the spring there is an increase in solar irradiance (power) from the sun. With
increased sunlight, more photosynthesis can occur and more phytoplankton can grow. The
second reason is the mixed layer
(where phytoplankton exist)
becomes shallower and the algae
is restricted to an area with more
light. At the same time, upwelling
events are occurring which pull up
nutrient rich waters from depth to
the surface which phytoplankton
require for growth. Increased
sunlight leads to increased sea
surface temperatures which Figure 3: Changes in the mixed layer depth from Winter to Spring
enables faster phytoplankton which is one of the factors contributing to algae blooms.
growth rates.
Many factors can lead to an algae bloom which is why they are so complex to monitor,
especially on a global scale. Despite being the base of the ocean’s food web, when they
bloom, algae can cause many issues for the surrounding organisms, especially on an
aquaculture farm. During a bloom, algae can completely deplete the oxygen in an area and
even more so as the bloom dies off and bacteria decomposes the dead organic matter.
In addition, some species produce neurotoxins that can harm and even kill fish
directly. Other species have mechanical barbs that can irritate and damage fish gills which
can hamper their ability to uptake oxygen from the water. As most salmon farms are situated
in coastal environments, farmers invest many resources into plankton monitoring and
mitigation efforts to protect their livestock.
Different species of phytoplankton impact farms at different threshold levels
depending on how they harm fish (Table1). Technically all plankton can become harmful in
The Ongoing Challenge of Plankton Monitoring and Mitigation | 2
large concentrations, however most species that are a concern to farmers are those that
produce toxins or have mechanically harmful structures. Table1 is a non-exhaustive list of
some harmful species and the concentrations at which they will cause problems if detected in
water samples.
Farmers engage in regular sampling
Table 1: Examples of harmful algae species that create
problems on salmon aquaculture farms protocol to keep track of what species are in
Species Name Harmful Level (Cells/ml) the water and at what concentration. These
Chattonella 5+ sampling methods employ the use of netted
Chaetoceros concavicorne 10+ tows, discrete water samples at various depths,
Chaetoceros convolutus 40+ flow cytometers and LiDAR to scan larger
Pseudochattonella 40+
regions. All methods require a significant
Corethron 150+
amount of time and resources that are invested
Dictyocha 150+
into getting accurate counts and estimates of
Heterosigma 150+
Pseudopedinella 250+ phytoplankton populations both on the farm
Gymnodinium 500+ and the surrounding area.
Chrysochromulina 750+
If we assume a farm during grow-out has
Cochlodinium 750+
8 cages with 50,00 fish per pen at 3kg each
Alexandrium 1000+
Pseudo-Nitzschia 3000+
(average harvest weight is 4.5kg). Market price
Rhizosolenia 3000+ per salmon is about $7 USD/kg so the value of
the biomass on the farm well before harvest is
over $8 million dollars. (Salmon Farming Industry Handbook, 2020). Farmers inherently want
to protect their fish, keep them healthy and be able to complete the most efficient production
cycle which requires minimizing fish mortality.
Disaster in Chile
The Chilean salmon aquaculture industry began in the early 1980s and since its
introduction has faced numerous encounters with algae blooms. While its warmer waters
favor a shorter grow-out cycle compared to regions like Canada and Norway, they face
extensive challenges from toxic phytoplankton.
A combination of factors led the region to experience one of the most destructive
algae blooms to date in 2016. Two blooms back to back plagued the area with
Pseudochatonella verruculosa and Alexandrium cantennella between February and April. The
region saw massive economic losses due to mass mortality equal to 15% of their yearly
salmon production. Over 200 shellfish farms were affected and benthic fisheries in the region
had to close for 4 months. These losses led to protests from the coastal communities that
lasted up to three weeks. (Trainer et al., 2020).
Exceptional water conditions in the region caused this catastrophic bloom. Over the
last few decades, the range of both species has increased. A southern expansion of
Pseudochatonella verruculosa and a Northern expansion of Alexandrium cantennella has led
The Ongoing Challenge of Plankton Monitoring and Mitigation | 3to blooms in new regions with an increasing frequency over the last few decades (Trainer at
al. 2020).
The range extension coupled with the simultaneous El Niño and positive phase of the
Southern Annular Mode (SAM) allowed the perfect mix of water conditions that led to this
super bloom.
El Niño is a climate driver that impacts rainfall, water and air temperatures in the
Southern Hemisphere. During an El Niño the westerly trade winds in the Southern
hemisphere weaken and reverse direction which leads to warmer waters on the Western
shores of South America.
The SAM is a
secondary climate driver
that impacts the westerly
winds found in the
subtropics below the
subtropical ridge. There
is an increasing trend of
more positive phases of
the SAM that are a result
of anthropogenic
climate change (Gillett et
al., 2013).
Typically, an El
Niño forces the negative
phase of the SAM,
however the fact that the
strongest positive phase
of the SAM aligned with
the El Niño suggests that
climate change is
influencing the SAM
enough to overcome the
El Nino forcing (Wang
Figure 4: Excerpt from Trainer et al., 2020 showing the range expansion of P.
verruculosa and A. cantennella over the last few years. The bottom graph is showing
and Cai, 2013).
the oscillation of the Southern Annular Mode (SAM) and the El Niño as well as
highlighting blooms of both species in Chile from 1972 to 2016.
The combination
of these two climate
drivers led to record low rainfall, reduced freshwater discharge, increased stratification from
high sea-surface temperatures (SST) and nutrient rich waters in the fjords (Trainer et al.,
2020). Although this was an extreme event, these extremes are demonstrating potential
future climate conditions and help us understand how the future climate state will impact the
severity and frequency of algae blooms (Trainer et al., 2020).
The Ongoing Challenge of Plankton Monitoring and Mitigation | 4The Impact of Climate Change
Algae bloom dynamics, location, frequency and severity have been greatly affected
by climate change. Climate change impacts the surface layers of the ocean most heavily and
this is the habitat for phytoplankton.
Australia is known as climate change hotspot and one of the changes that has been
documented is the expansion of the East Australian Current (EAC). Over the last few decades,
the EAC has become warmer and saltier, strengthening the current and therefore expanding
southward to Tasmania. A consequence of this is it has carried a toxic algae species with it, a
red-tide dinoflagellate Noctiluca scintillans (Figure 5).
Once a rare and ephemeral species, Noctiluca is now present year-long in Tasmania,
with the largest blooms in the summer. This has presented issues for both finfish and shellfish
aquaculture operations as well as nearby fisheries. (McLeod et al. 2012).
In 2015, an unprecedented bloom
of Pseudo-nitzschia australis,
known for producing the
neurotoxin domoic acid, occurred
along the West Coast of the United
States. The magnitude of this
bloom was driven by the fact that a
large warm water anomaly,
colloquially named “the blob,”
extended across the coastal waters
of the west coast of the U.S and
Canada.
This species of phytoplankton is
able to capitalize and grow much
faster under warmer temperatures Figure 5: Noctiluca red tides in Australian waters. a. Clovelly Beach,
Sydney, Nov 2012, Daily Telegraph; b, c, e. Tasman Peninsula, March 2002;
and increased nutrient photos G. Hallegraeff and J. Marshall; d. Freycinet Peninsula, Feb 2004,
concentrations from seasonal photo: E. Watson. (Hallegraeff et al. 2020)
upwelling.
This was the first time a Pseudo-nitzschia bloom caused harmful effect to both shellfish, and
finfish operations as well as marine mammal health along the west coast of the U.S and
Canada. It is possible that there will continue to be severely toxic blooms in this area due to
general warming of ocean temperatures, in particular during El Niño periods. Super blooms
such as this one are demonstrating the potential future of algae bloom severity and
unfortunately what is currently a rare occurrence could become more regular. (McCabe et al.
2016)
The Ongoing Challenge of Plankton Monitoring and Mitigation | 5How to Fight Algae Blooms
As we look ahead to the future of plankton monitoring and mitigation, we have to invest in
solutions now that will help farmers deal with these complex and dynamic problems. The first
step is to actually monitor and record the necessary data that influence bloom dynamics.
Having access to this data in real time is beneficial for farmers but historical data will be key to
inform baseline conditions.
Advancements in technology and data management allows for multiple data streams to be
captured and merged into a single database to analyze all relevant data simultaneously.
Mitigation strategies currently exist to manage a bloom once its occurring. Aeration and
oxygenation systems can provide fish with safe refuge when used correctly. Offshore farm
development is another potential mitigation strategy to avoid plankton blooms. Farms have
the capability to submerge themselves and avoid layers that may be plagued with plankton.
These are solutions to deal with algae bloom once they’ve formed but as we look to the
future how can we prepare for more frequent and severe blooms? At PICES-2019, a multi-day
workshop with over 48 international experts on the economics and science of HABS,
scientists discussed numerous case studies that highlighted the economic impact of HABs.
While the impact of HABs is known to be large it is poorly quantified and many countries
have not conducted an economic analysis of the impact of HABs (PICES, 2020). There should
be a push to quantify these losses, firstly so that we have baseline data to compare to in the
future but also if we quantify the impacts it will provide the evidence to push for more
research into HAB dynamics and prediction analysis.
Machine learning is going to play a big role in the future of HAB research. As we
inquire further into all the variables that lead to bloom formation, duration, frequency and
severity, the more data the better.
Technological advancements are allowing for in situ observation of a growing number
of parameters that are key to HAB dynamics. These sensors can provide continuous
measurements that can inform complex algorithms and provide insights into the conditions
that lead to bloom formation. Aquaculture farms are poised to collect this kind of data and
provide it to key stakeholders and scientist for analysis. They’re situated in coastal regions
and many already collect continuous data for operations. Data is extremely powerful and
individual efforts are needed but collaboration between farms, scientists and other
stakeholders is necessary for future HAB research.
The goal of sustainable aquaculture is to help feed our growing planet – if we continue
to suffer losses of these magnitudes in increased frequencies – it’s going to be hard to
expand the industry beyond what it is today. Minimizing the impacts of harmful algae blooms
is critical for aquaculture farmers and even more so as events are predicted to increase in
frequency and severity. As our population races to almost 10 billion people in the next thirty
years, we must invest in sustainable food production now and that involves managing any
potential barriers to growth.
The Ongoing Challenge of Plankton Monitoring and Mitigation | 6About the Author Jennie Korus is an aquaculture scientist at Innovasea and part of the Aquaculture Intelligence team in Halifax, Nova Scotia. Jennie holds an honors degree in Marine Biology and Statistics from Dalhousie University and an advanced diploma in Ocean Technology from NSCC. She is currently working towards her master’s in Oceanography at Dalhousie with a focus on fish stress and environmental monitoring on aquaculture farms. About Innovasea Fueled by leading-edge technology and a passion for research and development, Innovasea is revolutionizing aquaculture and advancing the science of fish tracking to make our oceans and freshwater ecosystems sustainable for future generations. With 250 employees worldwide, we provide full end-to-end solutions for fish farming and aquatic species research – including quality equipment that’s efficient and built to last, expert consulting services, and innovative platforms and products that deliver unrivaled data, information and insights. The Ongoing Challenge of Plankton Monitoring and Mitigation | 7
References: Bostock, J. (2011). The application of science and technology development in shaping current and future aquaculture production systems. The Journal of Agricultural Science, 149(S1), 133–141. https://doi.org/10.1017/S0021859610001127 Cultured Aquatic Species Information Programme. Salmo salar. Cultured Aquatic Species Information Programme. Text by Jones, M. In: FAO Fisheries Division [online]. Rome. Updated 1 January 2004. [Cited 25 August 2020]. Department of Health, Tasmania Government. (2018, February 20). Collecting and eating wild shellfish can cause illness. Retrieved August 26, 2020, from https://www.health.tas.gov.au/publichealth/alerts/standing_health_alerts/do_not_eat_wild_shellfish/co llecting_and_eating_wild_shellfish_can_cause_illness FAO. 2014. FAOSTAT. Food and Agriculture Organization of the United Nations, Rome, Italy FAO. 2020. The State of World Fisheries and Aquaculture 2020. Sustainability in action. Rome. https://doi.org/10.4060/ca9229en Gillett, N. P., Fyfe, J. C., & Parker, D. E. (2013). Attribution of observed sea level pressure trends to greenhouse gas, aerosol, and ozone changes. Geophysical Research Letters, 40(10), 2302–2306. https://doi.org/10.1002/grl.50500 McCabe, R. M., Hickey, B. M., Kudela, R. M., Lefebvre, K. A., Adams, N. G., Bill, B. D., Gulland, F. M. D., Thomson, R. E., Cochlan, W. P., & Trainer, V. L. (2016). An unprecedented coastwide toxic algal bloom linked to anomalous ocean conditions. Geophysical Research Letters, 43(19), 10,366-10,376. https://doi.org/10.1002/2016GL070023 McLeod, D. J., Hallegraeff, G. M., Hosie, G. W., & Richardson, A. J. (2012). Climate-driven range expansion of the red-tide dinoflagellate Noctiluca scintillans into the Southern Ocean. Journal of Plankton Research, 34(4), 332–337. https://doi.org/10.1093/plankt/fbr112 PICES Secretariat. (2020). Newsletter of the North Pacific Marine Science Organization. PICES Press. Vol 28(1). ISSN: 1195-2512. Trainer, V. L., Moore, S. K., Hallegraeff, G., Kudela, R. M., Clement, A., Mardones, J. I., & Cochlan, W. P. (2020). Pelagic harmful algal blooms and climate change: Lessons from nature’s experiments with extremes. Harmful Algae, 91, 101591. https://doi.org/10.1016/j.hal.2019.03.009 United Nations, Department of Economic and Social Affairs, Population Division (2019). World Population Prospects 2019: Highlights (ST/ESA/SER.A/423). Wang, G., & Cai, W. (2013). Climate-change impact on the 20th-century relationship between the Southern Annular Mode and global mean temperature. Scientific Reports, 3(1), 2039. https://doi.org/10.1038/srep02039. The Ongoing Challenge of Plankton Monitoring and Mitigation | 8
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