ΑΡΘΡΑ

Σταμάτης - Στυλιανός Βλάχος

MSc. Περιβαλλοντολόγος, διαχείριση ενέργειας & περιβάλλοντος, μέλος Οικολογικής Συνεργασίας Δήμου Παλαιού Φαλήρου ECO+  

Harmful Algal Blooms (HABs) & Red Tides

0 28 ΑΠΡΙΛΙΟΥ 2019, 20:29

«We do not inherit the earth from our ancestors. We borrow it from our children. »

Native American Proverb



ABSTRACT

Blooms of autotrophic algae and some heterotrophic protists (bacteria) are increasingly extremely frequent in coastal waters around the world and are collectively grouped as harmful algal blooms (HABs). Blooms of these organisms are attributed to two primary factors: natural processes such as circulation, upwelling relaxation, and river flow; and, anthropogenic loadings leading to eutrophication such as agricultural and urban runoff. Unfortunately, the latter is commonly assumed to be the primary cause of all harmful blooms, which is not the case in many instances. Moreover, although it is generally acknowledged that occurrences of these phenomena are increasing throughout the world’s oceans and cause serious economic damages to aquacultures, fisheries, marine mammals, seabirds and human health by producing dangerous biotoxins, the reasons for this apparent increase remain debated and include not only eutrophication but increased observation efforts and scientific research in coastal zones of the world.

Introduction

Phytoplankton is the autotrophic component of the plankton community. The name comes from the Greek words “φυτόν” (phyton), meaning "plant", and πλαγκτός (planktos), meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye. However, when present in high enough numbers, they may appear as a green discoloration of the water due to the presence of chlorophyll within their cells. There are many species of phytoplankton, each with a characteristic shape. Phytoplanktons grow abundantly in the world ocean and are the foundation of the marine food web. Also, a broad division of phytoplankton size is Microplankton from 20 to 200 micrometers, Nanoplankton from 2 to 20 micrometers and Picoplankton from 0.2 to 2 micrometers (Pagou, 2010; Amato, 2004). There are about 5000 phytoplankton species, divided in the following main groups of Diatoms, Dinoflagellates, Coccolithophores, Flagellates and Cyanobacteria or Blue-Green Algae. There are also procaryotic and eukaryotic phytoplankton cells (Pagou, 2010). Since phytoplankton depends upon certain conditions for growth, they are a good indicator of change in their environment, in which they occur. However, for these reasons, when waters enriched with nutrients in a very high degree, primarily Nitrogen and Phosphorus, under favorable physico-chemical conditions stimulate aquatic primary production and usually create the phenomenon of Eutrophication with most serious consequences the creation of Harmful Algal Blooms – HABs, Bacterial blooms and Algal Scum which affect the marine organisms (fish & marine mammals) and human health (Vollenweider, 1968; 1981).

1. What are Harmful Algal Blooms – HABs

Microalgae (also referred to as phytoplankton) are small, single celled organisms that grow in freshwaters, oceans and generally in marine ecosystems. When algae grow extremely rapidly in a confined area or grow to the point where you do not need a microscope to see it, it is referred to as an algal bloom. Blooms can be found within most bodies of water throughout the Great Lakes, but they thrive in shallow, warm, non-moving bodies of water like ponds and smaller lakes (Karydis, 2009; Amato, 2004). Most algal blooms are harmless, but certain types of algae may pose a risk to humans, animals and water quality. Algae and algal blooms are generally not considered harmful unless they are capable of producing toxins and you come in direct contact with them (Karydis, 2009; Amato, 2004). A Harmful Algal Bloom, or HAB, is a bloom of blue-green algae that potentially contains toxins. In other words, Harmful Algal Blooms occur when, under favorable conditions and circumstances phytoplankton suddenly increase in great numbers and can cause a variety of deleterious effects on aquatic and coastal ecosystems. HABs can cause massive fish kills, foul up nearby coastlines and produce conditions that are generally dangerous to aquatic life, as well as humans also. Blooms can range in color from red to bright neon green to more blue-green. A bloom can look like a scum, foam or mat on top of the water or like paint that has been spilled in the water. They are also sometimes accompanied by an earthy, pungent or musty smell. However, not all algal blooms give off an odor or affect the appearance of water and toxins can remain present in the water even when a bloom has dissipated (Pagou & Nastasi, 2010). Moreover, about taxonomic diversity, harmful algal species are now found in at least 5 groups of algae such as Dinophyceae, Prymnesiophyceae, Raphidophyceae, Bacillariophyceae and Cyanophyceae (Nastasi, 2010; Maso & Garces, 2006). HABs, especially in the Great Lakes region are made up of blue-green algae. While technically not an algae, blue-green algae are cyanobacteria that contain chlorophyll similar to true algae. They produce extremely rapidly, are typically found at or near the surface of the water and finally only few of them (about ¼) are known to produce toxins (Nastasi, 2010; Maso & Garces, 2006).

2. What causes HABs

Harmful algal blooms do naturally occur in specific regions, but have increased since the mid-1990s. Malfunctioning septic systems, products with phosphates like dishwasher detergent or phosphorus/nitrogen in lawn fertilizers, urban and agricultural runoff are thought to contribute to more frequent HABs. Some scientists also link the increase of harmful algal blooms to the invasion of zebra and quagga mussels especially in the Great Lakes and the ability of the mussels to filter feed. Essentially, they eat the good algae and phytoplankton but release organisms like blue-green algae back into the water intact. The harmful algal blooms often persist for several weeks to a few months, depending on air and water temperature, sunlight, water flow and naturally occurring bacteria levels (Sellner et al., 2003; Karydis, 2009).

3. The Phenomenon of the Red Tides

The “Red Tides” or algal blooms – as they generally called – are mass occurrences of a plankton species resulting from nutrient enrichment from intense upwellings, land runoff or other sources. About 300 species of algae are known to cause blooms, including dinoflagellates, diatoms, haptophytes and cyanobacteria, and some silicoflagellates. Algal blooms often occur in or adjacent to areas of upwelling, when prevailing winds blow surface water offshore, causing cold, deep, nutrient-rich waters to rise up, and bringing large quantities of phytoplankton with them that rapidly multiply due to favorable light and nutrient conditions (Sellner et al., 2003). The natural and seasonal phenomenon of the Red Tides is most common in Eastern Africa around November and at the beginning of the north-east monsoon. For instance, red tides were reported in Kenya (see case study), Zanzibar, Yemen, Oman and Mauritius in early 2002. Blooms tend to look like streaks of reddish-brown to greenish-yellow floating debris, depending on the species involved, and may extend for several miles. The term ‘Red Tide’ is a common name and often used, because of certain phytoplankton species, such as harmful dinoflagellate blooms in a very great numbers, which can seemingly color the water reddish or brownish red due to the carotenoid pigment in their cells. Moreover, there are in small scale ‘Brown, Green and Yellow – orange tides’ which can result from other phytoplankton species as we mentioned, such as harmful diatoms and cyanobacteria (Sellner et al., 2003). Many red tides are generally harmless, but about one quarter of the known species that cause blooms produce extraordinary dangerous toxins – biotoxins (Pagou & Nastasi, 2010).

4. Biotoxins that HABs produce

Unfortunately, a small number of species produce potent neurotoxins that can be transferred through the food web where they affect and even kill the higher forms of life such as zooplankton, shellfish, fish, birds, marine mammals, and even humans that feed either directly or indirectly on them. Marine biotoxins produce by phytoplankton usually during harmful algal blooms, are some of the most potent toxins in the world and extremely dangerous. For some toxins, doses at the microgram per kilogram level are more than sufficient to kill. When enough toxins are accumulated in fish or shellfish, small amounts of cooked or raw tissue can kill a human. For instance, recorded harmful algal blooms have produce enough paralytic shellfish poisoning (PSP) toxin in mussels that the consumption of one or two small mussels could have killed a normal, healthy adult human. While some toxins are very potent, requiring only small amounts to produce illness or death, other less potent toxins may accumulate to such high levels that they still can cause harm. For instance, the total dose of domoic acid to produce a minimal toxic effect is fairly high but it can accumulate in sufficient quantities in shellfish to produce deadly results –ranging from mild stomach distress to permanent brain damage and even death (Sellner et al., 2003; Maso & Garces, 2006). Also, it is known that from ~5000 phytoplankton species, only ~300 can cause HABs and only ~80 species of them are very dangerous and can produce biotoxins (Pagou, 2010). Generally, HABs that produce toxins is a very active area of research because first of all, it affects seriously human health, they cause regional economic impacts, especially in marine resources by causing mass mortality of fish, economic damages to aquacultures and to tourism and loss of environmental quality. Also, HABs are responsible for marine mammals’ deaths, effects of non-commercial species and finally, they are responsible for causing serious water quality degradation and discoloration (Nastasi, 2010; Maso & Garces, 2006).

5. Kinds of Biotoxins

The most significant public health problems caused by harmful algae are poisoning as a result of consuming contaminated fish or shellfish. Here are a few known examples of the types of poisoning that can occur from Harmful Algal Bloom – HAB toxin production.

Amnesic Shellfish Poisoning (ASP): ASP was first recognized in 1987 on Prince Edward Island, Canada after locals consumed blue mussels. There were over 100 acute cases and 4 deaths. One of the organisms causing ASP is the Diatom Nitzschia pungens f. multiseries, which produces the neurotoxin, domoic acid. A severe case of ASP includes symptoms of gastroenteritis, dizziness, headache, seizures, disorientation, short-term memory loss, and respiratory difficulty (Sellner et al., 2003; Maso & Garces, 2006).

Ciguatera Fish Poisoning (CFP): CFP was first recognized in the 1550s in the Caribbean; however, the causative organism was not identified until more recently. CFP has a pan tropical distribution and is known from the Caribbean basin, Florida, the Hawaiian Islands, French Polynesia, and Australia. Higher trophic-level carnivores, such as fish, accumulate high levels of the toxin by feeding on herbivorous fish. The herbivorous fish feed on macro algae, which serve as substrate for an assemblage of benthic dinoflagellates including Gambierdiscus toxicus, which is responsible for ciguatoxin production. These fish may be toxic for up to two years after becoming contaminated. In extreme cases, death from respiratory paralysis may occur. There is no antidote for CFP, which is now considered a major health and economic problem in many tropical islands, for locals and for uninformed tourists (Dickey, 2009; Gomez, 2003).

Neurotoxic Shellfish Poisoning (NSP): NSP is similar to CFP in that it also produces gastrointestinal and neurological symptoms. The dinoflagellate Karenia brevis is responsible for NSP. Blooms of Karenia brevis are marked by large patches of discoloured water and massive fish kills. Karenia brevis is an unarmored dinoflagellate and can be ruptured easily by wave action, causing its toxins to become aerosolized and produce asthma-like symptoms. K. brevis blooms were first recognized in the 1880s. K. brevis blooms are known through much of the Gulf of Mexico and are most common off the western Florida continental shelf; however, in the fall and winter of 1987–88, there was a large K. brevis bloom in the coastal waters of North Carolina. The local economy lost $24 million dollars when many shellfish harvesting areas were closed for the entire season, during which 48 cases of NSP were reported (Sellner et al., 2003; Maso & Garces, 2006).

Diarrhetic Shellfish Poisoning (DSP): DSP was first reported in Japan in 1976. The causative organisms are several species of the dinoflagellate, Dinophysis, which produces okadaic acid. DSP produces symptoms such as nausea and diarrhea, which are often mistaken for a bacterial infection. DSP is not fatal and recovery is generally within three days, even without medical treatment. DSP has been reported in Spain, Chile, Thailand, Japan, and New Zealand. DSP has also been reported in northeast U.S. waters. Some consider DSP to be the most serious and globally widespread phycotoxin-caused seafood illness (Sellner et al., 2003; Maso & Garces, 2006).

Paralytic Shellfish Poisoning (PSP): PSP was recognized by Native Americans before the arrival of European explorers. PSP is caused by saxitoxin, which was first characterized in 1957 and is recognized in 21 different forms. These saxitoxins contaminate fish and shellfish. Food chain concentrations of saxitoxin in mackerel have resulted in marine mammal deaths. Saxitoxins act on the peripheral nervous system and the central nervous system by inhibiting nerve transmission to muscles. If contamination is severe enough, death may occur through respiratory failure. Other symptoms include gastrointestinal distress, tingling, numbness, and ataxia. These are symptoms common to most other algal toxinrelated illness. Organisms containing saxitoxins include dinoflagellates especially of Alexandrium catenella and Alexandrium tamarense (Sellner et al., 2003; Maso & Garces, 2006).

Cyanobacteria: Just as there are many saltwater species that cause HABs, there are also freshwater species called cyanobacteria (blue-green algae) that cause similar problems to marine organisms (marine mammals, fishes) and humans. These can be recognized as green pond scum or algal mats. Common species are Microcystis and Oscillatoria. These freshwater HAB-causing organisms have the following characteristics, such as worldwide distributions, especially in fresh water, respond to nutrient enrichment with rapid growth, cyanotoxins bio-accumulate in the food chain and finally produce extremely dangerous neurotoxins and cause acute liver toxicity and gastrointestinal effects (Mankiewicz et al., 2003; Charmichael, 1994).

References

1. Sellner, Kevin G., Doucette, Gregory J., Harmful algal blooms: causes, impacts and detection, J/Ind Microbiol Biotechnol (2003) 30:383-406, DOI 10.1007/s10295-0030074-9, viewed at http://aquaticpath.umd.edu/mybay/sellnerhabcauses.pdf.

2. Amato I., ‘Plankton planet’, Discover, vol. 25, 2004, viewed at http://discovermagazine.com/2004/aug/plankton-planet.

3. Charmichael W.W., ‘The toxins of Cyanobacteria’, Scientific American, vol. 270, pp. 78 – 86, 1994, viewed at http://www.cyanotech.com/pdfs/spirulina/spbul58.pdf.

4. Pagou K., Harmful Algal Blooms, 2010, (PowerPoint presentation), viewed at http://www.solon.org.gr/downloads/PAGOU_Stylida_June_2009_MIN.pdf.

5. Nastasi A., Algal Blooms in the Mediterranean and Black Sea: a brief review, 2010, (PowerPoint presentation), viewed at http://151.1.154.86/gfcmwebsite/SAC/2010/SCMEE_Algal_Jelly/ppt/Nastasi_AlgalRe v.

6. Dickey Robert W., Plakas Steven M., Ciguatera: A public health perspective, Toxicon xxx (2009) 1 – 14, viewed at http://www.ncf-net.org/library/CiguateraToxicon.pdf.

7. Maso M., Garces E., Harmful microalgae blooms (HAB); problematic and conditions that induce them, Marine Pollution Bulletin 53 (2006) 620 – 630, viewed at http://www.aseanbiodiversity.info/Abstract/51006408.pdf.

8. Gomez F., The toxic dinoflagellate Gymnodinium catenatum: an invader in the Mediterranean Sea, Acta Bot. Croat. 62 (2), 65 – 72, 2003, CODEN: ABCRA 25 ISSN 0365–0588, viewed at http://www.rac-spa.org/node/341.

9. Karydis M., Eutrophication assessment of coastal waters based on indicators: A literature review, Global NEST Journal, Vol 11, No 4, pp 373-390, 2009, viewed at http://www.gnest.org/journal/vol11_no 4/373-390_626_karydis_11-4.pdf.

10. Mankiewicz J., Walter Z., Zalewski M., Tarczynska M., Natural Toxins from Cyanobacteria, ACTA BIOLOGICA CRACOVIENSIA Series Botanica 45/2: 9-20, 2003, viewed at http:// www.ib.uj.edu.pl/abc/pdf/45_2/01_manki.pdf.

Glossary 

Aerosolized — in the form of ultramicroscopic solid or liquid particles dispersed or suspended in air or gas.

Ataxia — loss of the ability to coordinate muscular movement.

Bioaccumulation — the increase in concentration of a substance in an organism over time.

Coccolithophores — kind of phytoplankton. They surround themselves with plates made of calcite. Known as coccoliths, these plates have a variety of shapes. They are smaller than 20 micrometers and are often enclosed by over 30 plates.

Cyanobacteria — the smallest kind of phytoplankton, they exist as small single cells (less than 1 micrometer in diameter) but some forms clump together, to form ‘bundles’ that can be seen by eye.

Diatoms — kind of phytoplankton. These algae occur as single cells, chains and colonies. Cell sizes range from 5 to 1000 micrometers. Some of them may have spines or other projections and some are toxic.

Dinoflagellates — any of numerous minute, chiefly marine protozoans of the order Dinoflagellata, characteristically having two flagella and a cellulose covering of theca. Cell sizes range smaller than 10 micrometers.

Gastroenteritis — an irritation and inflammation of the digestive tract.

Microalgae — small, single celled plants that grow in freshwater and oceans.

Pantropical — found and/or distributed in tropical regions around the world.

Phycotoxin — toxin produced by algae.

Phytoflagellates — they are motile organisms, so small that they must be identified using powerful microscopes or biochemical techniques. They are very abundant and often dominate the phytoplankton when larger forms.

Primary Production — is defined as the uptake of inorganic carbon into particulate matter as: Primary production = mg carbon / m3 / day.

Trophic — pertaining to nutrition or to a position in a food web, food chain, or food pyramid.
4
 

Σχόλια Αναγνωστών

0 Προσθήκη σχολίου

Δεν υπάρχουν ακόμα σχόλια για αυτό το άρθρο.

ΠΡΟΣΘΕΣΤΕ ΤΟ ΣΧΟΛΙΟ ΣΑΣ!
Απάντηση σε x
* Υποχρεωτικά πεδία* Το vimaonline σέβεται όλες τις απόψεις, αλλά διατηρεί το δικαίωμά του να μην αναρτά υβριστικά και άσχετα με το περιοχόμενο του άρθρου σχόλια. Είναι αυτονόητο πως η ομάδα διαχείρισης φέρει ευθύνη μόνο για τα επώνυμα άρθρα των συντακτών και των συνεργατών της.

Σας ευχαριστούμε για την συμμετοχή σας.