in stratification, vertical exchange, upwelling, precipitation, and related trends, all of which can also influence
the habitat for particular HABs (Moore et al., 2008).
Moreover, some HABs, especially CyanoHABs, such as
Microcystis spp., may become more toxic under higher
temperatures (Davis et al., 2009).
Climate change may influence HAB expansion, and
therefore, the frequency of some blooms may reflect the
major changes in ecosystem structure that occur in
response to interannual oscillations, such as those related
to the El Niño Southern Oscillation (ENSO), or longer
term cycles, such as North Atlantic Oscillation (NAO)
and the Pacific Decadal Oscillation (PDO). In the northern
Iberian Peninsula, for example, the abundance of the
harmful dinoflagellate Gymnodinium catenatum was high
during the mid-1980s when there was a transition from
downwelling-favorable conditions to upwelling-favorable
conditions following a shift in the NAO index (AlvarezSalgado et al., 2003). In California, there is circumstantial
evidence that a massive domoic acid event in Monterey
Bay in 1998 was triggered by post-El Niño runoff
(Scholin et al., 2000).
Estuaries: notable examples of sustained HABs
in retentive habitats
Estuaries throughout much of the world are sites of
frequent HABs (of all forms, including toxic, nuisance,
and ecosystem disruptive). Estuaries – whether they be
classic river-dominated systems, fjords, coastal embayments, or rias – have many unique features that may be
promotive of HABs. Many estuaries are experiencing
increasing nutrient loading from pressures of increasing
population and housing developments, intensive agriculture in the watershed, and increased aquaculture production. Estuaries may receive considerable riverine input or
may be highly retentive with minimal freshwater input
or oceanic exchange. The comparatively shallow nature
of estuaries (compared to open coasts and offshore
regions) means that benthic processes as well as water
column processes may be important in providing nutrients
for bloom development or maintenance. As a generality, in
estuaries and enclosed coastal embayments, exogenous
nutrients are often necessary for high biomass blooms to
be initiated, but due to long-term buildup of nutrients in
estuaries, leading to large sediment reserves of nutrients,
recycling and regeneration may sustain blooms at higher
densities and for longer periods of time than in years past.
Reinforcing feedbacks in estuaries can lead to an acceleration and/or maintenance of eutrophic conditions. For
example, increased algal productivity may lead to
depressed water column oxygen which, in turn, may result
in increased recycling of nitrogen and phosphorus by
changes in redox potential, or pH (Kemp et al., 2005;
Glibert et al., 2011; Gao et al., 2012). These fluxes will
then positively reinforce an ecosystems degradation
trajectory and may contribute to blooms being sustained
for long periods of time.
One such example is the bloom of Aureoumbra
lagunensis evident in Laguna Madre, Texas, that lasted
for approximately 8 years in the 1990s. Intense rains after
years of drought led to a sequence of blooms, and benthic
regeneration led to sustained suitable ecosystem conditions (e.g., Buskey et al., 2001). Similarly, a bloom of
Synechococcus was observed in eastern Florida Bay that
followed an injection of phosphorus from two apparent
sources: high freshwater discharge from Hurricanes
Katrina, Rita, and Wilma that impacted south Florida in
2005 and a very high organic loading from a unique
situation of road construction that required mulching of
significant amounts of mangroves (Madden, 2010).
Consequently, chlorophyll concentrations rose and were
sustained at levels roughly eightfold higher than
pre-bloom levels for up to 18 months, while such an
increase in phosphorus concentration was only observed
during the initiation stages of the bloom and then declined.
Detection, prediction, mitigation, and control
Rapid advances are being made in the ability to detect
HABs and, in some cases, predict their occurrence and
potentially reduce their impacts. Rapid detection capabilities have evolved from classic microscopic methods to
detection involving specific molecules and genomes. For
example, numerous methods have been developed
targeting antibodies against cell surface antigens that are
specific for a specific HAB or HAB group that can be
detected with a fluorescent signal (reviewed by Sellner
et al., 2003). Additionally, molecular probes have been
developed for many species, targeting the ribosomal
RNA genes and/or their transcriptional products. Many
taxon-species probes have been developed.
New methods have been advanced for detection of
toxins as well, and some are field based. Additionally,
much progress has been advanced in the use of remote
sensing capabilities, both remote imagery as well as
moored packages and arrays that can detect and provide
real-time information on species as well as associated
chemistry and physical parameters. Such packages
include both moored arrays and remotely operated
vehicles that can survey areas more efficiently than was
possible from classic shipboard approaches (Sellner
et al., 2003). A suite of over 50 such probes in the State
of Maryland is allowing managers and the public alike to
monitor trends in Chesapeake Bay and rapidly respond
when conditions warrant (www.eyesonthebay.net). In situ
nutrient sensors are also advancing, with capability developing for some organic forms of nutrients as well as
inorganic forms, so that relationships between pulses in
nutrient delivery and alterations in salinity due to rainfall,
for example, are now possible to establish (Glibert
et al., 2005b; Glibert et al., 2008).
Models and forecasting of blooms are advancing very
rapidly. There are two general types of HAB models that
are useful for management applications. The first is the
development of models that predict “general likelihood
ALGAL BLOOMS
13
the habitat for particular HABs (Moore et al., 2008).
Moreover, some HABs, especially CyanoHABs, such as
Microcystis spp., may become more toxic under higher
temperatures (Davis et al., 2009).
Climate change may influence HAB expansion, and
therefore, the frequency of some blooms may reflect the
major changes in ecosystem structure that occur in
response to interannual oscillations, such as those related
to the El Niño Southern Oscillation (ENSO), or longer
term cycles, such as North Atlantic Oscillation (NAO)
and the Pacific Decadal Oscillation (PDO). In the northern
Iberian Peninsula, for example, the abundance of the
harmful dinoflagellate Gymnodinium catenatum was high
during the mid-1980s when there was a transition from
downwelling-favorable conditions to upwelling-favorable
conditions following a shift in the NAO index (AlvarezSalgado et al., 2003). In California, there is circumstantial
evidence that a massive domoic acid event in Monterey
Bay in 1998 was triggered by post-El Niño runoff
(Scholin et al., 2000).
Estuaries: notable examples of sustained HABs
in retentive habitats
Estuaries throughout much of the world are sites of
frequent HABs (of all forms, including toxic, nuisance,
and ecosystem disruptive). Estuaries – whether they be
classic river-dominated systems, fjords, coastal embayments, or rias – have many unique features that may be
promotive of HABs. Many estuaries are experiencing
increasing nutrient loading from pressures of increasing
population and housing developments, intensive agriculture in the watershed, and increased aquaculture production. Estuaries may receive considerable riverine input or
may be highly retentive with minimal freshwater input
or oceanic exchange. The comparatively shallow nature
of estuaries (compared to open coasts and offshore
regions) means that benthic processes as well as water
column processes may be important in providing nutrients
for bloom development or maintenance. As a generality, in
estuaries and enclosed coastal embayments, exogenous
nutrients are often necessary for high biomass blooms to
be initiated, but due to long-term buildup of nutrients in
estuaries, leading to large sediment reserves of nutrients,
recycling and regeneration may sustain blooms at higher
densities and for longer periods of time than in years past.
Reinforcing feedbacks in estuaries can lead to an acceleration and/or maintenance of eutrophic conditions. For
example, increased algal productivity may lead to
depressed water column oxygen which, in turn, may result
in increased recycling of nitrogen and phosphorus by
changes in redox potential, or pH (Kemp et al., 2005;
Glibert et al., 2011; Gao et al., 2012). These fluxes will
then positively reinforce an ecosystems degradation
trajectory and may contribute to blooms being sustained
for long periods of time.
One such example is the bloom of Aureoumbra
lagunensis evident in Laguna Madre, Texas, that lasted
for approximately 8 years in the 1990s. Intense rains after
years of drought led to a sequence of blooms, and benthic
regeneration led to sustained suitable ecosystem conditions (e.g., Buskey et al., 2001). Similarly, a bloom of
Synechococcus was observed in eastern Florida Bay that
followed an injection of phosphorus from two apparent
sources: high freshwater discharge from Hurricanes
Katrina, Rita, and Wilma that impacted south Florida in
2005 and a very high organic loading from a unique
situation of road construction that required mulching of
significant amounts of mangroves (Madden, 2010).
Consequently, chlorophyll concentrations rose and were
sustained at levels roughly eightfold higher than
pre-bloom levels for up to 18 months, while such an
increase in phosphorus concentration was only observed
during the initiation stages of the bloom and then declined.
Detection, prediction, mitigation, and control
Rapid advances are being made in the ability to detect
HABs and, in some cases, predict their occurrence and
potentially reduce their impacts. Rapid detection capabilities have evolved from classic microscopic methods to
detection involving specific molecules and genomes. For
example, numerous methods have been developed
targeting antibodies against cell surface antigens that are
specific for a specific HAB or HAB group that can be
detected with a fluorescent signal (reviewed by Sellner
et al., 2003). Additionally, molecular probes have been
developed for many species, targeting the ribosomal
RNA genes and/or their transcriptional products. Many
taxon-species probes have been developed.
New methods have been advanced for detection of
toxins as well, and some are field based. Additionally,
much progress has been advanced in the use of remote
sensing capabilities, both remote imagery as well as
moored packages and arrays that can detect and provide
real-time information on species as well as associated
chemistry and physical parameters. Such packages
include both moored arrays and remotely operated
vehicles that can survey areas more efficiently than was
possible from classic shipboard approaches (Sellner
et al., 2003). A suite of over 50 such probes in the State
of Maryland is allowing managers and the public alike to
monitor trends in Chesapeake Bay and rapidly respond
when conditions warrant (www.eyesonthebay.net). In situ
nutrient sensors are also advancing, with capability developing for some organic forms of nutrients as well as
inorganic forms, so that relationships between pulses in
nutrient delivery and alterations in salinity due to rainfall,
for example, are now possible to establish (Glibert
et al., 2005b; Glibert et al., 2008).
Models and forecasting of blooms are advancing very
rapidly. There are two general types of HAB models that
are useful for management applications. The first is the
development of models that predict “general likelihood
ALGAL BLOOMS
13