of occurrence” of HAB species, whereas the second is the
development of models that include “explicit” predictions
of HAB occurrence in time or space. The former is useful
for management in application of long-term actions to
reduce the likelihood of future occurrences, i.e., prevention. The latter requires more refinement to understand
the physics, biology, and chemistry of the environment,
but it can be of more value at the local community level.
Coupling the knowledge of the biology of the organisms
of interest with robust circulation models of the area of
interest has allowed real-time forecasts to be possible.
An excellent example of this developing skill is the model
that has been developed for Karenia brevis blooms off the
coast of Florida. This model uses satellite imagery
together with a regional circulation model, predicted wind
fields, and several biological parameters to forecast where
blooms may be found in a several-day period. Operational
forecasts are now provided to the public for Florida and
several other regions of the United States where similar
capabilities are advancing (http://tidesandcurrents.noaa.
gov/hab/).
Understanding and predicting algal blooms is important, but the ultimate goal is reducing their occurrence or
their impacts once they do occur. The most effective
strategy for reducing their likelihood is nutrient reduction.
The best cited example illustrating the effectiveness of
nutrient reduction is from the Seto Inland Sea in Japan.
Between 1965 and 1976, the number of “red tide” outbreaks (high biomass blooms) increased sevenfold, in
parallel with the increase in industrial production, but in
1973, Japanese authorities instituted the Seto Inland Sea
Law to reduce loadings to half of the 1974 levels over
a 3-year period. The number of red tides began to decrease
in 1977, eventually falling to less than 30 % of the peak
frequency, which had been in excess of 300 blooms per
year (reviewed by Imai et al., 2006).
Bloom control strategies may also take the form of
mechanical control, the use of filters or booms to remove
or exclude cells from certain areas and use of chemical
compounds to kill or inhibit bloom cells, or biological control, the use of organisms or pathogens that can lyse, kill, or
remove the HABs. Some efforts are finding success with
the use of clays that flocculate and remove the HAB cells
from the area. Use of clays is well advanced in Korean
waters where clay application is used to protect fish cages
when HABs develop (Kim, 2006). Overall, however, all
of these control measures may have uncertain or unknown
environmental impacts, and all such approaches are in early
stages of research and development.
Summary and conclusions
In sum, while some algal blooms, such as spring blooms,
are natural characteristics of many temperate and coastal
waters, and critically important for food webs of marine
and freshwater ecosystems, HABs are, in large part,
a consequence of anthropogenic activities. HABs are
increasing in frequency, magnitude, and ecological and
economic effects throughout the world. Understanding
of toxins, human health impacts, and the socioeconomic
consequences of these blooms – to fisheries and economies – is emerging, but many questions remain
unanswered, particularly as new toxins are discovered
or characterized. One of the most significant factors
contributing to their expansion – particularly in estuaries –
is increased nutrient loading from sewage effluent, agriculture, animal operations, and aquaculture. What is clear
is that the historic view of phytoplankton responses to
eutrophication – increased nutrients promotes increased
chlorophyll and high biomass blooms, leading to oxygen
deduction and losses in habitat (e.g., Cloern, 2001) – is
too simplistic for understanding how HABs respond to
the major changes in nutrient loads, forms, and stoichiometry that many systems are now sustaining. Nutrient form
and proportion matter and many HABs have physiological
mechanisms that enable them to thrive in these environments that are being dramatically altered by human
influence. Furthermore, the interplay of biology and
physics is only understood at a limited scale, with much
to be learned about local scales, microstructures, as well
as mesoscale features. Climate changes are adding additional factors that may enhance the likelihood for blooms,
and the complexity of ecosystem changes with climate
changes means that much is yet to be learned about
the direct and indirect effects of climate on HABs. New
technologies are advancing toward improved monitoring
and prediction, but many such technologies are sophisticated and expensive. Although considerable advances
have been made in understanding the biology of HABs,
and their interactions with other members of the community at all levels of the food web, there is still much to be
learned about how and why specific species respond to
specific conditions.
Bibliography
Adolf, J. E., Bachvaroff, T., and Place, A. R., 2008. Cryptophyte
abundance drives blooms of mixotrophic harmful algae:
a hypothesis based on Karlodinium veneficum as a model
system. Harmful Algae, 8, 119–128.
Alvarez-Salgado, X. A., Figueiras, F. G., Perez, F. F., Groom, S.,
Nogueira, E., Borges, A., Chou, L., Castro, C. G., Moncoiffe,
G., Rios, A. F., Miller, A. E. J., Frankignoulle, M., Savidge,
G., and Wollast, R., 2003. The Portugal coastal counter current
of NW Spain: new insights on its biogeochemical variability.
Progress in Oceanography, 56, 281–321.
Anderson, D. M., Glibert, P. M., and Burkholder, J. M., 2002.
Harmful algal blooms and eutrophication: nutrient sources,
composition and consequences. Estuaries, 25, 562–584.
Azanza, R., and Taylor, M., 2001. Are Pyrodinium blooms in the
southeast Asian region recurring and spreading? A view at the
end of the millennium. AMBIO: A Journal of the Human Environment, 30, 356–364.
Backer, L. C., and McGillicuddy, D. J., 2006. Harmful algal
blooms: at the interface between coastal oceanography and
human health. Oceanography, 19(2), 94–106.
Bargu, S., Goldstein, T., Roberts, K., Li, C., and Gulland, F., 2012.
Pseudo-nitzschia blooms, domoic acid, and related
California sea lion strandings in Monterey Bay, California
14
ALGAL BLOOMS
development of models that include “explicit” predictions
of HAB occurrence in time or space. The former is useful
for management in application of long-term actions to
reduce the likelihood of future occurrences, i.e., prevention. The latter requires more refinement to understand
the physics, biology, and chemistry of the environment,
but it can be of more value at the local community level.
Coupling the knowledge of the biology of the organisms
of interest with robust circulation models of the area of
interest has allowed real-time forecasts to be possible.
An excellent example of this developing skill is the model
that has been developed for Karenia brevis blooms off the
coast of Florida. This model uses satellite imagery
together with a regional circulation model, predicted wind
fields, and several biological parameters to forecast where
blooms may be found in a several-day period. Operational
forecasts are now provided to the public for Florida and
several other regions of the United States where similar
capabilities are advancing (http://tidesandcurrents.noaa.
gov/hab/).
Understanding and predicting algal blooms is important, but the ultimate goal is reducing their occurrence or
their impacts once they do occur. The most effective
strategy for reducing their likelihood is nutrient reduction.
The best cited example illustrating the effectiveness of
nutrient reduction is from the Seto Inland Sea in Japan.
Between 1965 and 1976, the number of “red tide” outbreaks (high biomass blooms) increased sevenfold, in
parallel with the increase in industrial production, but in
1973, Japanese authorities instituted the Seto Inland Sea
Law to reduce loadings to half of the 1974 levels over
a 3-year period. The number of red tides began to decrease
in 1977, eventually falling to less than 30 % of the peak
frequency, which had been in excess of 300 blooms per
year (reviewed by Imai et al., 2006).
Bloom control strategies may also take the form of
mechanical control, the use of filters or booms to remove
or exclude cells from certain areas and use of chemical
compounds to kill or inhibit bloom cells, or biological control, the use of organisms or pathogens that can lyse, kill, or
remove the HABs. Some efforts are finding success with
the use of clays that flocculate and remove the HAB cells
from the area. Use of clays is well advanced in Korean
waters where clay application is used to protect fish cages
when HABs develop (Kim, 2006). Overall, however, all
of these control measures may have uncertain or unknown
environmental impacts, and all such approaches are in early
stages of research and development.
Summary and conclusions
In sum, while some algal blooms, such as spring blooms,
are natural characteristics of many temperate and coastal
waters, and critically important for food webs of marine
and freshwater ecosystems, HABs are, in large part,
a consequence of anthropogenic activities. HABs are
increasing in frequency, magnitude, and ecological and
economic effects throughout the world. Understanding
of toxins, human health impacts, and the socioeconomic
consequences of these blooms – to fisheries and economies – is emerging, but many questions remain
unanswered, particularly as new toxins are discovered
or characterized. One of the most significant factors
contributing to their expansion – particularly in estuaries –
is increased nutrient loading from sewage effluent, agriculture, animal operations, and aquaculture. What is clear
is that the historic view of phytoplankton responses to
eutrophication – increased nutrients promotes increased
chlorophyll and high biomass blooms, leading to oxygen
deduction and losses in habitat (e.g., Cloern, 2001) – is
too simplistic for understanding how HABs respond to
the major changes in nutrient loads, forms, and stoichiometry that many systems are now sustaining. Nutrient form
and proportion matter and many HABs have physiological
mechanisms that enable them to thrive in these environments that are being dramatically altered by human
influence. Furthermore, the interplay of biology and
physics is only understood at a limited scale, with much
to be learned about local scales, microstructures, as well
as mesoscale features. Climate changes are adding additional factors that may enhance the likelihood for blooms,
and the complexity of ecosystem changes with climate
changes means that much is yet to be learned about
the direct and indirect effects of climate on HABs. New
technologies are advancing toward improved monitoring
and prediction, but many such technologies are sophisticated and expensive. Although considerable advances
have been made in understanding the biology of HABs,
and their interactions with other members of the community at all levels of the food web, there is still much to be
learned about how and why specific species respond to
specific conditions.
Bibliography
Adolf, J. E., Bachvaroff, T., and Place, A. R., 2008. Cryptophyte
abundance drives blooms of mixotrophic harmful algae:
a hypothesis based on Karlodinium veneficum as a model
system. Harmful Algae, 8, 119–128.
Alvarez-Salgado, X. A., Figueiras, F. G., Perez, F. F., Groom, S.,
Nogueira, E., Borges, A., Chou, L., Castro, C. G., Moncoiffe,
G., Rios, A. F., Miller, A. E. J., Frankignoulle, M., Savidge,
G., and Wollast, R., 2003. The Portugal coastal counter current
of NW Spain: new insights on its biogeochemical variability.
Progress in Oceanography, 56, 281–321.
Anderson, D. M., Glibert, P. M., and Burkholder, J. M., 2002.
Harmful algal blooms and eutrophication: nutrient sources,
composition and consequences. Estuaries, 25, 562–584.
Azanza, R., and Taylor, M., 2001. Are Pyrodinium blooms in the
southeast Asian region recurring and spreading? A view at the
end of the millennium. AMBIO: A Journal of the Human Environment, 30, 356–364.
Backer, L. C., and McGillicuddy, D. J., 2006. Harmful algal
blooms: at the interface between coastal oceanography and
human health. Oceanography, 19(2), 94–106.
Bargu, S., Goldstein, T., Roberts, K., Li, C., and Gulland, F., 2012.
Pseudo-nitzschia blooms, domoic acid, and related
California sea lion strandings in Monterey Bay, California
14
ALGAL BLOOMS