Part F | 33.5
794 Part F Marine Derived Metabolites
of sea-life and are increasingly responsible for human
intoxication.
However, no color is visible in other harmful
species, such as the chlorophyll-free dinoflagellate Pfiesteria piscicida, several Dinophysis species, and a
benthic one (Gambierdiscus) that grow on the surfaces
of larger macroalgae in tropical waters. Both Pfiesteria
and Dinophysis also impart toxicity at very low densities, generally less than 1000 cells L
1 [33.42, 43].
Unfortunately, a small number of species produce
potent neurotoxins that can be transferred through the
food web where they affect and even kill higher forms
of life such as zooplankton, shellfish, fish, birds, marine
mammals, and even humans that feed either directly
or indirectly on them. Algal bloom is due to toxinproducing species, so that the poison is concentrated via
the food chain and may reach humans.
Marine toxins can also affect local ecosystems by
poisoning animals. Health effects range from cell damage to organism mortality through such mechanisms
as toxin production and localized conditions of low
oxygen. Under some conditions, so much oxygen is
consumed to support the decomposition of dead algal
biomass that anoxic conditions develop. This can cause
severe stress or mortality in a wide range of organisms
that are intolerant to low-oxygen conditions.
Genera that are commonly associated with poisonous red tides are Alexandrium, Dinophysis, and
Ptychodiscus. The algal poisons can accumulate in
marine organisms that feed by filtering large volumes of water, for example, shellfish such as clams,
oysters, and mussels. If these shellfish are collected
while they are significantly contaminated by red tide
toxins, they can poison the human beings who eat
them. Some toxins, such as that from Ptychodiscus brevis, the organism that causes Florida red
tides, are airborne and can cause throat and nose
irritations.
33.5 Toxigenic Dinoflagellate-Associated Human Poisoning
The possible presence of natural toxins in fish and
shellfish has been known for a long time. The most
important marine phycotoxins are shellfish toxins and
finfish-ciguatoxins. Most of these toxins are produced
by species of naturally occurring marine dinoflagellates
(phytoplankton). A proportion of the toxic phytoplankton has a reddish-brown pigmentation, giving rise to
calling algal blooms red tides. Visible red tides may
contain from 20 000 to > 50 000 algal cells mL
1 concentrations, and as low as 200 cells mL
1 may produce
toxic shellfish. Some dinoflagellates produce toxins that
become concentrated in the bodies of organisms higher
in the food chain, such as fish and shellfish. Marine animals such as oysters, crustacea, and different types of
fish may eat the toxic dinoflagellates storing the toxins. The toxins are accumulated in the digestive gland
of the shellfish (hepatopancreas) and do not affect the
shellfish themselves. They often accumulate in shellfish or fish, and when these are eaten by humans they
cause diseases. People are exposed principally to the
toxins produced by harmful dinoflagellates through the
consumption of contaminated seafood products. During
dinoflagellate blooms humans eating seafood from infested areas can be poisoned. This can lead to serious
poisoning.
Based on contaminants of toxic dinoflagellates in
seafood there are two main types of human poisoning. The terms fish and shellfish are associated with
these illnesses because the toxins concentrate in the
fish and shellfish that ingest the harmful dinoflagellates. Fish and shellfish poisoning occur worldwide.
According to the species of toxigenic dinoflagellates
the poisoning syndromes have been given the names
paralytic, diarrhetic, neurotoxic, and azaspiracid shellfish poisoning. A fifth human illness, CFP is caused
by ciguatoxins produced by dinoflagellates that attach
to surfaces in many coral reef communities [33.1].
Broadly these can be classified as shown below (see
also Table 33.1).
Those caused by eating fish, namely: CFP. Those
caused by eating shellfish, until now, seven groups of
syndromes have been distinguished, namely:
1. Paralytic shellfish poisoning (PSP)
2. Neurotoxic shellfish poisoning (NSP)
3. Diarrheic shellfish poisoning (DSP)
4. Azaspiracid shellfish poisoning (AZP)
5. Palytoxins poisoning (PTX)
6. Yessotoxins poisoning (YTX).
Amnestic shellfish poisoning (ASP) is also a related
poisoning affecting humans, which was recently discovered but will not be discussed in this chapter because
it is caused by marine red algae and is tracked to certain
benthic diatoms (Bacillariophyceae) of the genus Chondria and diatoms of the Pseudonitzschia f. multiseries
but not by a dinoflagellate [33.44–47].
794 Part F Marine Derived Metabolites
of sea-life and are increasingly responsible for human
intoxication.
However, no color is visible in other harmful
species, such as the chlorophyll-free dinoflagellate Pfiesteria piscicida, several Dinophysis species, and a
benthic one (Gambierdiscus) that grow on the surfaces
of larger macroalgae in tropical waters. Both Pfiesteria
and Dinophysis also impart toxicity at very low densities, generally less than 1000 cells L
1 [33.42, 43].
Unfortunately, a small number of species produce
potent neurotoxins that can be transferred through the
food web where they affect and even kill higher forms
of life such as zooplankton, shellfish, fish, birds, marine
mammals, and even humans that feed either directly
or indirectly on them. Algal bloom is due to toxinproducing species, so that the poison is concentrated via
the food chain and may reach humans.
Marine toxins can also affect local ecosystems by
poisoning animals. Health effects range from cell damage to organism mortality through such mechanisms
as toxin production and localized conditions of low
oxygen. Under some conditions, so much oxygen is
consumed to support the decomposition of dead algal
biomass that anoxic conditions develop. This can cause
severe stress or mortality in a wide range of organisms
that are intolerant to low-oxygen conditions.
Genera that are commonly associated with poisonous red tides are Alexandrium, Dinophysis, and
Ptychodiscus. The algal poisons can accumulate in
marine organisms that feed by filtering large volumes of water, for example, shellfish such as clams,
oysters, and mussels. If these shellfish are collected
while they are significantly contaminated by red tide
toxins, they can poison the human beings who eat
them. Some toxins, such as that from Ptychodiscus brevis, the organism that causes Florida red
tides, are airborne and can cause throat and nose
irritations.
33.5 Toxigenic Dinoflagellate-Associated Human Poisoning
The possible presence of natural toxins in fish and
shellfish has been known for a long time. The most
important marine phycotoxins are shellfish toxins and
finfish-ciguatoxins. Most of these toxins are produced
by species of naturally occurring marine dinoflagellates
(phytoplankton). A proportion of the toxic phytoplankton has a reddish-brown pigmentation, giving rise to
calling algal blooms red tides. Visible red tides may
contain from 20 000 to > 50 000 algal cells mL
1 concentrations, and as low as 200 cells mL
1 may produce
toxic shellfish. Some dinoflagellates produce toxins that
become concentrated in the bodies of organisms higher
in the food chain, such as fish and shellfish. Marine animals such as oysters, crustacea, and different types of
fish may eat the toxic dinoflagellates storing the toxins. The toxins are accumulated in the digestive gland
of the shellfish (hepatopancreas) and do not affect the
shellfish themselves. They often accumulate in shellfish or fish, and when these are eaten by humans they
cause diseases. People are exposed principally to the
toxins produced by harmful dinoflagellates through the
consumption of contaminated seafood products. During
dinoflagellate blooms humans eating seafood from infested areas can be poisoned. This can lead to serious
poisoning.
Based on contaminants of toxic dinoflagellates in
seafood there are two main types of human poisoning. The terms fish and shellfish are associated with
these illnesses because the toxins concentrate in the
fish and shellfish that ingest the harmful dinoflagellates. Fish and shellfish poisoning occur worldwide.
According to the species of toxigenic dinoflagellates
the poisoning syndromes have been given the names
paralytic, diarrhetic, neurotoxic, and azaspiracid shellfish poisoning. A fifth human illness, CFP is caused
by ciguatoxins produced by dinoflagellates that attach
to surfaces in many coral reef communities [33.1].
Broadly these can be classified as shown below (see
also Table 33.1).
Those caused by eating fish, namely: CFP. Those
caused by eating shellfish, until now, seven groups of
syndromes have been distinguished, namely:
1. Paralytic shellfish poisoning (PSP)
2. Neurotoxic shellfish poisoning (NSP)
3. Diarrheic shellfish poisoning (DSP)
4. Azaspiracid shellfish poisoning (AZP)
5. Palytoxins poisoning (PTX)
6. Yessotoxins poisoning (YTX).
Amnestic shellfish poisoning (ASP) is also a related
poisoning affecting humans, which was recently discovered but will not be discussed in this chapter because
it is caused by marine red algae and is tracked to certain
benthic diatoms (Bacillariophyceae) of the genus Chondria and diatoms of the Pseudonitzschia f. multiseries
but not by a dinoflagellate [33.44–47].