Approximately there are from 4000 (Lin et al., 2016) to 5000 species of identified microalgae (Daranas et al., 2001; Santi Delia et al., 2015; Hallegraeff et al., 1995; Lindahl, 1998). Naturally, some bloom-forming species, basically harmless, cause water discolorations, on the other hand, another species can bloom densely, under exceptional conditions in sheltered water bodies, especially those used for fish farming; they indiscriminately kill fishes and invertebrates because of oxygen depletion. Other species of phytoplankton can be harmful to the fish and invertebrates especially in the intensive aquaculture systems due to damaging or clogging their gills. Moreover, there are microalgal species which have the ability to produce potent toxins, named phycotoxins which can find then way through levels of food chain, for example, Mollusks, Crustaceans, and finfish that are ultimately consumed by humans causing a variety of gastrointestinal and neurological illnesses (Al-Ghelani et al., 2005; Zaccaroni and Scaravelli, 2008; Berdalet et al., 2016).


There are three major groups depending on the problem they cause. The first group is formed by nontoxic species that discolor the water, includes Tiicliodes- mium thiebautii, Skeletonema costatum, Chaetoceros sociale, Thalasiossiara mala, Encampia zodiacus, Prorocentrum sigmoides, P. ltiicans, Dinophysis caudata, Noctiluca scintillans, Ceratium tn'pos, C. furca, C. fitsits, Gyrnno- dinium sanguineum, G. mikimotoi, Cochlodinium polybikoides, Lingulodinium polyedrum, Protoceratium reticulatum, Gonyaulax polygramma, Alexandrium affine, Peridinium quinquecome, Heterocapsa triquetra, Heterosigma akashiwo, Scrippsiella trochoidem, Heterocapsa circulasqiama, Fibrocapsa japonica, and Chattonella antiqua (Fukuyo, 2000).

However, under some conditions, growth is very high that it generates anoxic conditions which result in indiscriminate killing of both fish and invertebrates. Depletion of oxygen (O) can be due to high respiration by algae community at the night or in dim light during the day, with another cofactor which considered more commonly is resulting from the respiration of bacteria during the decay of the bloom.

Examples of microalgae that can cause these problems are some species of the dinoflagellates Gonyaulax, Noctoluca, and Scrppsiella (Daranas et al., 2001).

Recently, there is a second group recognized and has become apparent only as a result of our increasing interest in intensive aquaculture systems, some species of algae can damage gills of fish mechanically and seriously or due to production of hemolytic substances while wild fish stocks have the freedom and ability to avoid such areas of problem, and the caged fish are appearing to be vulnerable to HABs. Recently, studies refer to potent ichthyotoxins named Prmymnsin-1 and prymnesin-2 have been isolated from Prymnesium parvum cultures (Manning and La Claire, 2010), the Prmymnsin-1 has been known for the last three decades (Sasaki et al., 2006; La Claire et al., 2015). Due to extreme difficulty in purification, the chemical nature of the toxin was not known for a long time. Also, in this group, it can be considered hemolysin isolated from Amphidinium carterae cultures which structures are glyceroglycolipids. Other species within this group of HABs are diatoms, like Chaetoceros convolutes, dinoflagellates like Gymnodinium mikimotoi, prymnesiophytes—Chrysochromulina polyl- epis, Prymnesium patelliferum, and raphidophytes-T/eterasigwa carterae or Chatonella antiqua that they were impacted and killed caged yellowtail fish at the Seto Island Sea in 1972, causing losses estimated about 500 million US dollars (Daranas et al., 2001).

The third group, collect those species that produce potent toxins, which they can easily find their way to humans via the food chain, also these toxins impact humans and cause a variety of gastrointestinal and neurological illnesses after ingestion.

In fact, among all the existing marine algal species, there are 75 diagnosed as phycotoxins producers and responsible for blooms (Ade et al., 2003; IOC- UNESCO, 2009). Besides the numbers of dinoflagellates, the diatoms are also responsible of toxicity, and toxic threats of diatoms should not be neglected, because diatoms form the major individuals of the phytoplankton community, and they tend to dominate under neutral high nutrient concentration. The diatoms are the main biochemical cycles of macronutrients N, P, Si, and Fe, also tend to dominate export production (Sarthou et al., 2005). There are several toxic species of diatoms have been recorded and classified as a toxic species, like Amphora coffeaeformis. Nitzschia navis-varingica, Pseudo- nitzschia australis, P. calliantha, P. cuspidata, P. delicatissima, P. frandn- lenta, P. galaxiae, P. multiseries, P. multistriata, P. pungens, P. seriata, and P. turgidula (IOC-UNESCO, 2009). The toxic species of Pseudo-nitzschia bloom may occur and become a recurring phenomenon, it is very important to determine if there is any seasonal or spatial predictability that is what has been reported by Congestri et al. (2006, 2008) and Villac et al. (1993). There are important factors, like climate change and warming of oceans, helped a lot in spreading affected coastal zones with neurotoxins of domoic acid (DA), which is produced by Pseudo-nitzschia (McKibben et al., 2017). High cell numbers up to 4><104 cell L"1 of toxic species P delicatissima, P delicatissima, and P. pseudodelicatissima that have been recorded in the gulf Naples and along with Latium coasts (Congestri et al., 2006; Montresor et al., 2000). Due to many studies, some algal species are recorded as toxin producers at a low abundance of several or some hundreds of cells L'1, while other species must occur in some millions of cells L"1 to cause any harm. The taxonomic diversity of HABs species was suggesting that each species is adapted to some of the environmental conditions or in ecological terms, for a defining niche. Once ecological requirements for each species separately are known, it may or easy to predict its occurrence (Zingone and Enevoldsen, 2000; Wells et al., 2015). Actually, most of the harmful algal species have restricted distribution pattern but some harmful species have a worldwide distribution (Hallegraeff, 2010; Fu et al., 2012). However, the impacts of HABs depends upon the concentration to appear harmful effects, but in fact, the most harmful species are widespread also become hazardous only when their concentration exceeds a certain threshold for sufficiently high toxic dose (Berdalet et al., 2016; Zingone and Enevoldsen, 2000). Toxins that produced by phytoplankton can harm Invertebrates too and developed higher trophic level organisms such as fish, marine birds, and mammals because of the accumulation of toxins and/or due to varying degrees of physiological damage. Different accumulated types of potent toxins are produced during the bloom’s development of several HABs species in suspension-feeding shellfish and also affect human consumers and is resulting in outbreaks of paralytic, neurotoxic, amnesic, azaspiracid, and diarrheic shellfish poisoning (DSP) as reported in (Table 20.1). Direct effects on suspension-feeding bivalves include the valve (Archambalut et al., 2002).

There are many toxic algal species, such as dinoflagellates, were recorded internationally via IOC-UNESCO in 2009, and cited by Jessim (2009) (Table 20.2).

Some of these species were mentioned to them by Kaladharan et al. (2011) along the Karnataka coast, for example, Gymnodiniales, Peridinales, and Prorocentrales.


There are several toxic species dinoflagellates diagnosed as toxic, which is mentioned in this chapter depending on (FAO, 2004) as in follow. PARALYTIC SHELLFISH TOXIN PRODUCERS

The first recorded group of species of phytoplankton as producer of paralytic shellfish toxin, which cause paralytic shellfish poisoning syndrome (PSP), are Alexandrium, which was named formerly Gonyaulax or Protogonyaulax, and identified as contaminators in shellfish. These species are Alexandrium tamarensis, A. minutum (syn. A. excavata), A. catenella, A. fraterculus, A. fimdyense, A. cohorticula, Gymnodinium catenatum, and Pyrodinium bahamense. DIARRHEIC SHELLFISH TOXIN PRODUCERS

The second group was recorded as diarrheic Shellfish toxin can cause DSP syndrome, production of DSP toxins has been identified and confirmed in seven identified species of Dinophysis species D. fortii, D. acuminata,

D. acuta, D. non’egica, D. mitra, D. rotundata D. tripos, and Pltalacrotna



Short-term health consequences

Long-term consequences of toxin


Reef fish

Ciguatera fish poisoning:

Abdominal pain, nausea, vomiting, diarrhea; paresthesias, temperature dysesthesia, pain, weakness, bradycardia, hypotension

Long duration (months to years) of symptoms, Chronic

Okadaic acid and its derivatives


Diarrhetic shellfish poisoning:

Nausea, vomiting, diarrhea, vomiting, diarrhea, abdominal pain accompanied by chills, headache, fever

Gastrointestinal tumor promoter in laboratory annuals




Not documented as toxic in humans, but co-occur with DSP and are highly toxic to mice




Azaspiracid shellfish poisoning:

nausea, vomiting, severe diarrhea, stomach cramps




Neurotoxic shellfish poisoning:

Numbness of lips, tongue, and throat, muscular aches and pains, fever, chills, abdominal cramping, nausea, diarrhea, vomiting, headache, reduced heart rate, pupil dilation



Acute eye irritation, respiratory distress, asthma exacerbation


Saxi toxins


Paralytic shellfish poisoning:

Tingling, burning, numbness, drowsiness, incoherent speech, respiratory paralysis leading to death


Puffer Fish

Saxitoxin puffer fish poisoning

tingling, burning, numbness, drowsiness, incoherent speech, respiratory paralysis leading to death


Source: Reprinted from Archambault. et al., 2002.


Dinophysis acuminata


D. acuta

О A. Dinophysis toxin-1

D. caudata

OA. Pectenotoxin-2

D. fortii

О A. DTX-1. PTX-2

D. miles

О A. DTX-1

D. mitra


D. non’egica

О A. DTX-1

D. тара


D. rotundata


D. sacculus


D. tripos



Alexandhum catenella

Paralytic Shellfish Poisoning toxins

A. Andersonii

PSP toxin


Fish mass mortality

A. catenella

PSP toxin and fish mass mortality


PSP toxins

A. hiranoi

Producer of antifungal substance

A. minutum

PSP t and fish mass mortality

A. monilatum

Fish mortality-causing, haemolytic

A. ostenfeldii


A. tamarense

PSP toxin, macrocyclic inline, a neurotoxin

A. tamiyavanichii

PSP toxin

Coolia monotis

PSP toxin

Gambierdiscus ausbales


G. paciflcus

Ciguatoxin. maitotoxin-like toxins

G. toxicus

Ciguatoxin. maitotoxin-like toxins

G. yasumotoi

Cigiiatoxins 4A. 4B and 3C and maitotoxins-1, -2 and -3

Ostreopsis lenticularis

Maitoxin-like compound, lethal to mice

O. mascarenensis

Neurotoxins. ostreotoxin-1 and -3

O. ovata

Palytoxin analogues. mascarenotoxin-A and -B

O. siamensis

Toxic butanol-soluble compound



Ostreocin D Yessotoxin

Pyiodinium bahamense

PSP toxin


Prorocentrum arenarium


P. belizeanum


P. cassubicum

Diarrhetic Shellfish Poisoning (DSP)

P. emarginatum


p. faustiae


p. hoffmannianum

О A. Fast Acting Toxins (FAT)

p. minimum

О A. Prorocentrolide B. FAT

p. lima


p. arabianum

Cytotoxic compounds

p. brobonicum

Probably neurotoxic lethal to mice

p. rhathymum

Toxic to mice, ingested cells can cause detrimental effects in molluscs. Some strains excrete substances toxic to Ailemia nauplii. Water soluble acetone precipitate is toxic to mice


Amphidinium carterae


A. operculatum

Compounds with haemolytic and antifungal properties (amphidinols), may be toxic to fish

Cochlodinium polyknkoides

Serious fish killer. PSP toxin

Gymnodinium catenatum

Fish killer

Gyrodinium corsicum

Produces brevetoxin in culture. Marine animal mortalities, Neurologic Shellfish Poisoning (NSP), respiratory irritation.

Karenin bicuneifomis

Annual and plant mortalities, human respiratory distress, eye and skin irritations

K. brews

Believed to cause NSP and respiration distress in humans

K. brevisulcata

Found to produce brevetoxin in culture

K. concordia

Killing offish, and cultured seaweed

K. chstata

(Poiphyra tenera) also affected

K. digitata

A cytotoxic polyether. Gyumocin-A from a Japanese culture

K. papihonace

Spiroimine gymnodimine producer in culture

K. sellifonnis

Fish kills in Tasmania, killing rainbow trout and salmon Fish mortality

K. umbrella

Fish kills, killing rainbow trout and salmon.

Karlodinium anniger

Fish mortality

K. eneficum

Toxic to a range of mar ine invertebrates and fish, karlotoxins producer that exhibits a broad-spectrum of lytic effect on membranes from very diverse cell types

Takayama cladochroma

Mortality of fish and invertebrate

Source: Reprinted from IOC-UNESCO, 2009.

rotm/daturn. Diarrheic shellfish toxin can be found in benthic dinoflagellates which are Prorocentrum lima, P. concavum, or (P maculosum), and P redfieldi that were also recorded as producers of DSP toxins, also the isolated benthic species P arenarium from the reef ecosystem of Europa Island (Mozambic channel, France) and isolated/! belizeanum from Belizean coral reef ecosystem also were found produce OA. Other studies reported suspected three other dinophysis species that are D. candata, D. hastate, and

D. sacculus and also suspected as producers of OA. (Hallegraeff et al., 1995). According to (Jessim, 2009) D. sacculus one of OA. producers. (Giacobbe et al., 2000) reported that/), saccilus contained OA. and DTX1 with maximum (DSP) toxins (OA. + DTX1 = 455 fg/cell) were found at early spring blooms. On the other hand, the detection of DSP toxins presence in the heterotrophic dinoflagellates Protoperidinium oceanicum and P pellucidiun may reflect their feeding on Dinophysis (Hallegraeff et al., 1995). DOMOIC ACID PRODUCERS

Third group is collect diatoms, these diatoms are the main resource of DA that are responsible about amnesic shellfish poisoning syndrome, this group contain several species of Diatoms, and they are Amphora coffeaefonnis, Pseudo-nitzschia pungens f. multiseries, P. pseudodelicatissima, P delicatis- sima (syn. Nitzschia actydrophila), P. seriata, P. fraudulenta, P. turgidula, and Nitzschia navis-varingia. NEUROLOGIC SHELLFISH TOXINS PROD UCERS

The fourth group is containing the species who produce Neurologic Shellfish Toxins that cause neurologic shellfish poisoning (NSP) syndrome; this group collects G. breve also named Ptychodiscus breve, since 2000 called Karenia brevis, which executed as a producer of several neurotoxins, they are Chattonella anti qua, Fibrocapsa japonica, and Heterosigma akaslmvo. AZASPIRACID SHELLFISH TOXIN PROD UCERS

The fifth group suggests that Protoceratum crassipes is the Azaspiracid Shellfish toxin producer producing Dinoflagellates. There is other reported that an organism belonging to the genus Protoperidinium suggests as the source organism. MARINE TOXINS THE WATER-SOLUBLE MAITOTOXINS AND THE FATE-SOLUBLE CIGUATOXINS

The sixth group contains Gambierdiscus toxicus that is reported as a responsible organism for about 2 types of marine toxins, water-soluble maitotoxins, and fat-soluble ciguatoxins, researches have reported a benthic dinoflagellates Ostreopsis lenticularis was shown to be a vector of Ciguatera fish poisoning, mentioned that other dinoflagellates, which may play a role in the production of toxins associated with ciguatera poisoning, like rorocentrum concavum, P. meicanum,P rhothytum, Gymnodimum sanguineum, and Gonyaidaxpolyedra.

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