New Initiative on Fish-Killing Algal Blooms
An Advanced International Colloquium
and Technical Workshop on Fish-Killing
HABs under the auspices of IOC-IPHAB
and GlobalHAB, and with the support of
the government of Chile through CORFO
and collaboration of CREAN-IFOP, was
held in Puerto Varas, Chile, 8 11 October 2019. Ten invited participants (D.M.
Anderson, A.D. Cembella (WG chair,
apologies), O. Espinoza, L. Guzman, G.M.
Hallegraeff, P.J. Hansen (acting chair),
H. Hegaret, T.O. Larsen, J. Mardones, M.
Iwataki, L. MacKenzie) reviewed the
state-of-knowledge on fish-killing algal
blooms (Fig. 1).
The socio-economic impacts from
fish-killing microalgal blooms are much
greater on a global scale than those from
HAB species causing seafood biotoxin accumulation and contamination. Examples
are the 1973 Chattonella marina bloom
in the Seto Inland Sea, Japan (estimated
US$71M loss to sea bream aquaculture),
the 1988 Prymnesium polylepis bloom
in the European Kattegat with widescale marine ecosystem impacts, and the
2015/16 Pseudochattonella verruculosa
bloom in Chile (US$800M loss to salmon
aquaculture). Highly potent fish-killers include the globally distributed, taxonomically unrelated flagellate groups Alexandrium, Margalefidinium (Cochlodinium),
Chattonella, Heterosigma, Pseudochattonella/Vicicitus, Karenia, Karlodinium,
Prymnesium/Chrysochromulina which all
produce lytic compounds that irreparably
damage the sensitive gill tissues of fish
which then die from suffocation. With
perhaps a single exception (Karenia brevis in Florida), none of these fish-killing
algal blooms have ever caused human
health problems from seafood consumption, which partially explains the limited
attention these HABs previously have attracted. Except for recent advances with
Prymnesium (prymnesins) and Karlodinium (karlotoxins), the precise mechanisms
of how such microalgae kill finfish remain
poorly understood. Pseudochattonella is
particularly poorly understood, with high
ichthyotoxicity in nature but limited potency observed in culture studies. While
some species are always ichthyotoxic, others such as Heterosigma and Alexandrium
catenella cause problems only under special environmental conditions. Progress
in this field has been hindered by the use
of widely different bioassay systems (Artemia, blood and fish gill RT1 cell lines,
embryos, juvenile and adult fish) and lack
of analytical chemical methods and reference materials to quantify and characterize so-called ichthyotoxins. Furthermore these compounds cause problems in
extremely low concentrations dissolved
in an aqueous medium, as opposed to the
well known toxins PST, DST, AST, NST
bioaccumulating in high concentrations in
seafood. Essentially similar ichthyotoxins
also adversely impact shellfish, shellfish
hatcheries and aquariums that draw in
water from bloom affected areas. Climate
change is adding to the unpredictability
of such rapid fish killing blooms and puts
further pressure on seafood security for an
ever increasing human population. Fishkilling HABs can be compared to disastrous forest fires, and not doing anything is
no longer deemed acceptable. Prevention,
prediction and monitoring are no longer
sufficient, and we actively need to pursue
strategies to stop the blooms, for example
by means of clay flocculation of algal biomass and/or mopping up of ichthyotoxins.
The working group reviewed our
knowledge of algal taxonomy, toxin
chemistry, modes of action, fish-killing
mechanisms, bioassays, broader ecosystem impacts, role of climate change,
and options for prevention, control and
mitigation. A well-attended open conference, accessible via webinar, and a
visit to a local salmon farm formed part
of the workshop. A follow-up session
on fish-killing HABs is next scheduled
for ICHA 2020 in Mexico, and a dedicated journal issue on this topic is being
planned.
Some of the presentations are available on the link below; https://www.
facebook.com/1871967802832922/videos/1254975338037553/.
Authors
Leonardo Guzmán, Centro de Estudios de Algas Nocivas (CREAN), Instituto de Fomento
Pesquero, Puerto Montt, Chile
Gustaaf Hallegraeff, Institute for Marine and
Antarctic Studies, University of Tasmania,
Hobart, Tasmania, Australia
Email: leonardo.guzman@ifop.cl
Invited speakers and hosts of the Advanced International Colloquium and Technical Workshop on Fish-Killing HABs. Puerto Varas, Chile October 8-11, 2019. Photo courtesy of Oscar Espinosa, IFOP.
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HARMFUL ALGAE NEWS NO. 63 / 2019
Harmful Algae News An IOC Newsletter on Toxic Algae and Algal Blooms No. 63 - December 2019 www.ioc-unesco.org/hab Harmful Algal Blooms in a Changing Climate In September 2019 the Intergovernmental Panel on Climate Change (IPCC) approved and accepted the Special Report on the Ocean and Cryosphere
New Initiative on Fish-Killing Algal Blooms An Advanced International Colloquium and Technical Workshop on Fish-Killing HABs under the auspices of IOC-IPHAB and GlobalHAB, and with the support of the government of Chile through CORFO and collaboration of CREAN-IFOP, was held in Puerto Varas, Chile,
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