GB2468849A - Compositions and methods for treating or preventing harmful algal blooms - Google Patents

Abstract

The invention provides compositions and methods for treating or preventing harmful algal blooms such as red tides. Algicidal compositions comprising a preparation or extract of one or more plants selected from the group of Pimpinella anisum (aniseed), Myristica fragrans (nutmeg) and Syzygium aromaticum (cloves) are described as well as methods for treating harmful algal blooms which comprise applying to the affected or susceptible waters an algicidal composition according to the invention. The harmful algal bloom may be Cochlodinium polykrikoides. Also claimed is a method of disinfecting vessels and other marine tools, instruments and facilities contaminated with harmful algal bloom.

Description

METHODS AND COMPOSITIONS FOR THE CONTROL OF

HARMFUL ALGAL BLOOMS

This invention relates to methods and compositions for the control of harmful algal blooms.

Algae are generally microscopic organisms and may be thought of as simple aquatic plants which do not have roots, stems or leaves and have primitive methods of reproduction. Some algae display primitive animal features such as motility, while blue-green algae differ markedly from plants and all other algae in that they have a cellular structure and function that is more common to bacteria than to the plant kingdom.

Algae live in a wide range of aquatic environments and are a natural component of most aquatic ecosystems. Aquatic algae are found in both fresh and marine waters. They range in size from those visible only under a microscope to large kelps which may be metres in length.

Rapid reproduction of microscopic aquatic algae, caused by certain conditions such as high nutrients combined with warm temperatures and good light, can result in a dense population of algae called a bloom, which is visible to the naked eye. Algal blooms may occur in freshwater as well as marine environments. Many types of algae form blooms, some of which are harmless or even important to the health of the ecosystem. However, some blooming organisms contain toxins, other noxious chemicals or pathogens which can be harmful to aquatic life, fish stocks and to human health. These harmful algal blooms (HAB5) are sometimes referred to as "red tides" after the colour of the bloom in the water, although the colour of the bloom depends on the species present and not all HABs are red.

Red tides dominated by the harmful dinoflagellate Cochiodinium polykrikoides have caused annual losses of USD $5-60 million to the Korean aquaculture industry annually since 1995 and a loss of USD $3 million during a 1999 net-pen fish mortality event in Canada (Jeong et al. 2008). In Japan red tides mainly kill finfish and have frequently caused very severe fisheries damage of more than 100 million yen (about one million US$) (Fukuyo et al. 2002). The average economic loss associated with noxious red tides is around 1.5 billion yen per year; it is therefore important to predict occurrences of red tide containing noxious species which kill fish and bivalves in order to reduce the negative impact on the aquaculture industry (Imali et al. 2006).

Among the important red tide organisms, Cochiodinium antiqua, Heterocapsa circularisquama and Cochiodinium polykrikoides are rated as extremely harmful species that can easily reach the warning level of fishery damage by consuming only small amounts of nutrients (Imali et al. 2006).

Cochlodinium polykrikoides is an unarmoured, marine, planktonic dinoflagellate species with a distinctive spiral-shaped cingulum. It is a cosmopolitan species found in warm temperate and tropical waters (Steidinger and Tangen 1996). This species was first reported from the Caribbean Sea along the southern coast of Puerto Rico (Margalef 1961). It has since been reported in northern Atlantic waters along the American east coast: Barnegat Bay, New Jersey (Silva 1967), and the York River, Virginia (Ho and Zubkoff 1979; Zubkoff et al. 1979). It is widely distributed in northwestern Pacific waters along the coasts of Japan and Korea (Fukuyo et al. 1990; Kim 1998) associated with fish kills. The emergence of Cochiodinium polykrikoides blooms in the Peconic Estuary and Shinnecock Bay, NY, USA during 2002-2006 was reported.

Bioassay experiments demonstrated that after 24 h exposure to bloom waters at cell densities >5 x i04 cells m11 100% of multiple fish species were killed while fish survived for 48 h at cell densities below I x i03 cells m11 (Gobler et al. 2008).

Recently red tide was also found in the northwestern coast of the United Arab Emirates and has affected large areas of coastline. The bloom has killed fish and coral, causing huge environmental damage as well as financial losses.

Diving operators and hotels are suffering financially as are desalination plants because of the costs of changing water-intake filters (The National Newspaper, Abu Dhabi, 26 February 2009).

I

A-

The algae are an athecate species, i.e. without thecal plates. Cells are small, oval and slightly flattened dorso-ventrally. Cells range in size from 30-40 um in length to 20-30 urn in width (Silva 1967; Yuki and Yoshimatsu 1989; Fukuyo et al. 1990; Taylor et al. 1995; Steidinger and Tangen 1996).

It is a photosynthetic species with numerous yellowish-green to brown chloroplasts, rod-shaped or ellipsoid in shape. The nucleus is situated anteriorly in the epitheca. A red stigma is present dorsally in the epitheca (Silva 1967; Yuki and Yoshimatsu 1989; Fukuyo et al. 1990; Taylor et al. 1995).

The alga is a planktonic species. It is a common ichthyotoxic red water' bloom species in the northwestern Pacific. This species commonly forms cysts (Fukuyo et al. 1990; Taylor et al. 1995; Steidinger and Tangen 1996).

Cochlodinium polykrikoides is a known red tide species associated with extensive fish kills and great economic loss in Japanese and Korean waters (Yuki and Yoshimatsu 1989; Fukuyo et al. 1990; Kim 1998). However, the actual toxin principles have yet to be elucidated (Taylor et al. 1995). Ho and Zubkoff (1979) suggested that physical contact, not a released toxin, was the cause of oyster larvae (Crassostrea virginica) deformation and mortality during a C. polykrikoides red tide in the York River (Virginia, USA).

C. polykrikoides closely resembles two other Cochlodinium species: C. helix and C. helicoides. The degree of rotation of the cingulum and sulcus distinguish the former species from the latter two: a. the cingulum in C. polykrikoides makes 1.8-1.9 turns around the cell, while in C. helix it is two turns and in C. helicoides it is 1.5 turns; and b. the sulcus turns 0.8 times between the proximal and distal ends of the cingulum in C. polykrikoides, whereas it is I time in C. helix and 0.6 times in C. helicoides (Silva 1967).

Many countermeasures have been applied for harmful algal blooms (Fukuyo et al. 2002; Imali et al. 2006). The counteraction techniques are roughly divided into two categories, indirect and direct methods. Indirect methods are basically important as prevention of red tide occurrences on a long-term scale (Imali et al. 2006) and include the following measures: 1. Regulation 2. Laws for the regulation of water quality 3. Water pollution control law 4. Marine pollution prevention law 5. Regulation of agriculture chemicals 6. Remediation 7. Water quality: absorption of inorganic nutrients by algae 8. Bottom sediment quality: dredging, aeration, digging, applications of sand, clay, lime, purification by benthos (Capitella) 9. Fish culture technique 10. Using moist pellets as bait 11. Keeping the proper scale and density of fish 12. Emergency procedures 13.Transfer of net cages 14.Cessation of feeding In addition many methods for the direct control of red tides have previously been attempted (Shirota 1989; Song et al. 2005; Imali et al. 2006). These are: 1. Physical method 2. Physical shock: ultrasonic waves, electric current, air bubbling 3. Collection: suction, filtration, collection and centrifugation of surface red-tide water 4. Aggregation and sedimentation: clay, iron powder, macromolecular flocculant 5. Chemical method 6. Chemicals: hydrogen peroxide, organic acids, surfactants 7. Chemical reaction: ozone evolution 8. Biological method 9. Bivalves: oyster, etc 10. Zooplankton: copepods, ciliates, heterotrophic dinoflagellates, nanoflagellates 11.Algicidal bacteria 12.Algicidal viruses For environment-friendly mitigation strategies for red tides, biological controls using diatoms and algicidal bacteria and viruses are proposed (Fukuyo et al. 2002). A new finding of the abundant existence of algicidal bacteria on the surface of seaweed suggests that co-culturing fish and seaweed is a prevention strategy for harmful algal blooms by virtue of the continuous release of many algicidal bacteria to the surrounding seawater. The artificial development of seaweed beds would also be effective as a prevention strategy for red tides (rna et aL 2006). Recently the Strombidinopsis jeokjo (a naked ciliate) has been introduced to control C. polykrikoidesin and effectively reducing natural populations of C. polykrikoides from approximately 1000 cells mr1 to below 10 cells m11 within 2 days. The growth and ingestion rates of cultured S. jeokjo on natural populations of C. polykrikoides in the mesocosms for the first 30 h (0.72 day1 and 51 ng C grazer1 day1) were 84% and 44%, respectively, of those measured in the laboratory during bottle incubations with similar initial prey concentrations. The calculated grazing impact of S. jeokjo on natural populations of C. polykrikoides suggests that large-scale cultures of this ciliate could be used for controlling red tides by C. polykrikoides in small areas (Jeong et al. 2008).

Overall still the method suggested by Shirota (1989) represent one promising strategy that could be used to treat red tides with flocculants such as clay, which scavenge particles, including algal cells, from seawater and carry them to bottom sediments and implemented in Kyushu and Korea have been successful to some extent for the removal but not killing of C. polykrikoides red tides (Fukuyo et al. 2002). Thereafter, these chemical and physical control options have received little attention (Fukuyo et al. 2002). Accordingly, there are at present no wholly successful physical or chemical control methods (Imali et al. 2006).

Hence, there remains an urgent need for improved compositions and methods for the control of harmful algal blooms, said compositions and methods being safe and effective and without adverse effect on the environment.

Accordingly, the present invention provides a method for treating or preventing harmful algal bloom, which comprises applying to the affected or susceptible waters an effective amount of a composition comprising a preparation or extract of one or more plants selected from the group of Pimpinella anisum, Myristica fragrans and Syzygium aromaticum.

The present invention arises from the inventors' finding that simple, ground preparations of certain herbs exhibit a marked algicidal effect when tested against red tide seawater comprising the harmful algae Cochiodinium polykrikoides.

Pimpinella anisum (anise, aniseed) is a culinary herb whose fruit is used for flavouring cakes, breads, fish, meat and vegetable dishes, as well as alcoholic drinks and cordials. Anise is also used in traditional herbal remedies e.g. to aid digestion, ease trapped wind, cure hiccups, freshen breath, soothe coughs, aid sleep and relieve toothache. Anise oil, whose principal component is anethole, is used to treat lice and scabies and, mixed with other ingredients, against insects. It is also reported to have antifungal and antiviral activities suggesting its use in the treatment of colds and flu.

Myristica fragarns (nutmeg) is a culinary herb whose fruit gives us the spices: nutmeg (the seed kernel) and mace (the aril, or lacy covering on the kernel). Powdered or grated nutmeg is used to flavour savoury and sweet dishes in Asian, Middle Eastern and European cuisines. The essential oil is used as natural food flavouring in baked goods, syrups (e.g. Coca Cola), beverages, sweets etc. In traditional medicine nutmeg and nutmeg oil were used for illnesses related to the nervous and digestive systems. The essential oil, obtained by the steam distillation of ground nutmeg, is also used in the cosmetic and pharmaceutical industries e.g. in toothpaste and cough syrup. Myristicin and elemicin are believed to be the chemical constituents responsible for the subtle hallucinogenic properties of nutmeg oil. Other known chemical ingredients of the oil are a-pinene, sabinene, y-terpinene and safrole.

Syzygium aromaticum (syn. Eugenia aromaticum, Eugenia catyophyllata, Eugenia caryophyllus or Caryophyllus aromaticus) is a tropical tree, the immature, unopened flower buds of which provide, when dried, the spice known as cloves. Whole or ground cloves are a popular spice in North African, Middle Eastern and European dishes, both savoury and sweet. Cloves contain 15 to 20% essential oil which is mostly Eugenol, the principal flavour-giving volatile oil which is a very strong antiseptic. Clove oil is a strong stimulant and carminative and is traditionally used to treat nausea, indigestion and dyspepsia. It is also commonly used to treat toothache.

The results disclosed herein show that preparations of P. anisum, M. fragrans and S. aromaticum each show effective algicidal activity in a test assay using red tide seawater comprising C. polykrikoides as the dominant organism.

The herb S. aromaticum appears to have the greatest activity in the test system.

Synergistic effects are observed with combinations of two or more herbs. The combination of P. anisum, M. fragrans and S. aromaticum provides particularly effective algicidal activity. In a preferred embodiment, the composition comprises Pimpinella anisum, Myristica fragrans and Syzygium aromaticum in a ratio of about 3:2:5.

As used herein, "algicidal" means the property of killing algae or arresting or retarding their normal growth and development such that a harmful algal bloom is prevented or ameliorated.

The ability of compositions as described herein to kill harmful algae is demonstrated in the following example in a test system using seawater affected by "red tide" harmful algal bloom in which Cochiodinium polykrikoides is the dominant species, however, there is no reason to suppose that the algicidal activity will be restricted to only this species of harmful algae or this type of harmful algal bloom. The methods and compositions of the invention are expected to have utility against any harmful algal bloom including, but not limited to, those caused by species of algae mentioned in the introduction and the

examples.

Because compositions as described herein comprise preparations of plant origin, said plants being herbs already consumed by man, there is a low risk of toxicity to man or the environment from the use of said compositions for the treatment or prevention of harmful algal blooms.

Conveniently, the preparation is powdered dried plant material e.g. the dry seed or kernel, or fruit or part thereof (e.g. aril), or bud, or flower, which has been ground to a powder. Suitable and readily available dry herb materials include: fruit of P. anisum (anise "seed" or aniseed), seeds (nutmeg) or arils (mace) of M. fragrans and dried flower buds (sometimes called pods) of S. aromaticum (cloves). The foregoing substances are readily obtainable owing to their culinary use as spices. The plant material is ground to a powder to allow easy dispersal of the preparation and promote diffusion of the algicidal agent.

The above mentioned plant parts have been identified by the inventors as having profound algicidal effects, however, other plant parts may be used in the compositions and methods of the invention. The observed algicidal effects will be brought about by one or more active agents produced by the respective plant.

These active agents may be found in other parts of the plant to those specifically mentioned above. Any plant part containing the active agent(s) is a candidate material for preparing an algicidal composition according to the invention. Plant parts containing the active agent(s) may be determined empirically by measuring algae killing or inhibitory activity in a test assay such as the one described herein.

Alternatively, once the active agent(s) has been identified, the concentration of the active molecule(s) in different tissues or organs of the plant can be measured directly. For practical purposes, preferred plant parts are those which accumulate the active ingredient in relatively large amounts. Ideally, the plant part is relatively easy to harvest and handle, such as a seed or fruit. However, other parts such as leaves, roots, stems or flowers or parts thereof may be suitable provided that the active agent(s) is present in sufficient quantities to give the desired algicidal effect. Conveniently, the herbs may be cultivated according to normal agricultural practices and the plant part containing the active agent(s) harvested and dried. The dried plant material can be used in the algicidal compositions and methods of the invention with minimal processing: typically, the plant material is cleaned (as necessary) and milled (ground) to a powder.

As an alternative to using the powdered herb directly in the algicidal composition, an extraction, e.g. with alcohol, water or organic solvent, or decoction of the powdered herb may be performed and the product of said process used in the algicidal composition.

It may be desirable to purify the algicidal fraction of the herb preparation to a lesser or greater extent, or even to isolate the algicidal factor, prior to use in a method or composition according to the invention.

The method of the invention may be applied to harmful algal blooms wherever they occur, including freshwater (e.g. rivers, lakes, ponds and reservoirs) and seawater (e.g. open sea, including coastal waters).

Compositions according to the invention are conveniently applied to the surface of the water as a powder. A rate of 750gm2 has been found to be effective in the control of HABs in the open sea.

In another embodiment, the invention provides the use of a composition comprising a preparation or extract of one or more plants selected from the group of Pimpinella anisum, Myristica fragrans and Syzygium aromaticum for the treatment or prevention of harmful algal bloom.

In a further embodiment, the invention provides method for killing Coch/odinium spp., which comprises treating the organism with a composition comprising a preparation or extract of one or more plants selected from the group of Pim pine/Ia anisum, Myristica fragrans and Syzygium aromaticum. Preferably the Coch/odinium sp. is Coch/odinium po/ykrikoides.

In a still further embodiment, the invention provides a method for disinfecting/decontaminating vessels, such as ships and boats, and other marine tools, instruments and facilities (offshore or onshore) contaminated with harmful algal bloom, which comprises applying to the vessels, tools, instruments or facilities a composition comprising a preparation or extract of one or more plants selected from the group of Pim pine/Ia anisum, Myristica fragrans and Syzygium aroma ticum.

In yet another embodiment, the invention provides an algicidal formulation comprising a preparation or extract of one or more plants selected from the group of Pim pine/Ia anisum, Myristica fragrans and Syzygium aromaticum, and one or more vehicles, carriers, binders or excipients. The algicidal formulation is useful for the treatment and prevention of harmful algal blooms, e.g. red tides, in the open sea, including coastal waters. The algicidal formulation has further utility for the disinfection/decontamination of vessels and other marine tools, instruments and facilities contaminated with harmful algal bloom.

Preferred features of different embodiments of the invention are as to each other mutatIs mutandis.

The invention will now be illustrated by the following non-limiting

examples.

EXAMPLE I

MATERIALS AND METHODS

Preparation of a Homogenized Suspension of Red Tide Seawater was collected from different locations with "red tide" of algae that is devastating the waters off the coast of Fujairah. Samples of 500 Litres of the red tide seawater were equally distributed into transparent plastic fish tanks attached with oxygen distributors.

The microscope examination method has shown the presence of eight different algae species that are found in the north western coast of the United Arab Emirates seawaters; these are Cochlodinium polykrikoides, Karenia mikimoto Prorocentrum micans, Dinophysis caudate, Pyrodinium bahamense, Gymnodinium catenatum, Ceratium furca and Ceratium fusus. In average the seawater contained approximately >7 x 10 cells mr1 of the red tide in which the Cochlodinium polykrikoides is the most dominant species.

Herbal preparation Dried clove pods Syzygium aromaticum, Pimpinella anisum L. seed, and Myristica fragrans seed were purchased from a local Dubai herbal market. All herbal materials were cleaned from dust by being air-dried for 15 mm in metallic strainers and were then powdered individually in a grinder.

Anti-Red Tides Assays Different concentrations (WN) of herbal formulas compositions comprised from Pim pine/Ia anisum, Myristica fragrans and Syzygium aromaticum were prepared in 500 Litres seawater and 500 Litres control sample (herbal material not added) as follows: Formula one: Pimpine/la anisum 0.3%; and Myristica fragrans 0.2 % Formula two: Syzygium aromaticum 0.5%, Pimpinella anisum 0.3% and 0.2% of Myristica fragrans.

After incubation for lh at 25°C the numbers of red tides cells were checked microscopically and recorded for each sample.

RESULTS

The tests of seawater have shown the presence of eight different algae species that cause red tide these are Cochlodinium polykrikoides, Karenia mikimoto Prorocentrum micans, Dinophysis caudate, Pyrodinium bahamense, Gymnodinium catenatum, Ceratium furca, Ceratium fusus. The red tide of Coch/odinium polykrikoides is the most dominant species on the rest, and continues to spread in the waters of the northwestern coast of the United Arab Emirates.

The results set out in Table I indicates that each aqueous solution of 0.3% of Pimpinella anisum seed, Myristica fragrans seed and clove pods Syzygium aromaticum, powder has red tidecidal activity alone in comparisons to untreated control sample.

The combination of Pimpinella anisum 0.3% and Myristica fragrans 0.2% showed a profound synergy against red tide harmful algal bloom (Table 1).

Moreover, the addition of clove pods at concentration 0.5% to the combination 0.3% Pimpinella anisum and 0.2% Myristica fragrans appears to have a significant beneficial effect on the percentage killing of the red tides algae (Table 1). Furthermore, the aqueous solutions �=0.5% clove pods has specific anti-red tides activity in the sample under treatment.

The role of the clove pods in interaction with both Pimpinella anisum and Myristica fragrans seed needs further investigation.

Table 1. The percentage of killing (number of non-motile lysed cell per 100 counted cells) of Cochlodinium polykrikoides and other red tides algae in aqueous solutions prepared in seawater of different herbal compositions measured at various intervals of incubation at 25°C.

Percentageofaqueous 1mm 5mm 15mm 30mm 60mm solutions of herbal materials ________ ________ ________ ________ _________ Control 0.00 0.00 0.00 0.00 0.00 Pimpinella anisum 0.3% 5% 30% 80% 100% 100% Myristica fragrans 0.3 % 5% 30% 78% 100% 100% Syzygium aromaticum 0.3% 50% 80% 100% 100% 100% Formula One: 15% 50% 85% 100% 100% Pimpinella anisum 0.3%; and Myristica fragrans 0.2 % ________ ________ ________ ________ _________ Formula Two: 60% 90% 100% 100% 100% Syzygium aromaticum 0.5%, Myristica fragrans 0.2% and Pimpinella anisum 0.3%

EXAMPLE 2

MATERIALS AND METHODS

Direct treatment of HABs in an open sea A location of seawater devastated with HABs has been identified on the coast of Fujairah. A twenty square meter area was marked by 4 small boats. The microscope examination method was carried-out to identify the algae species on the surface of seawater and at depth of I and 2 meters. Seawater temperature was recorded.

Anti-Red Tides Assays Formula 2, comprised from Syzygium aromaticum 0.5%, Myristica fragrans 0.2% and Pimpinella anisum 0.3%, showed the greatest activity against red tides algae in the 500 Litre tank test (Example 1). Accordingly, for the experiments in open sea, a dry herbal mixture was prepared in which the component herbs were present in the same ratio as in formula 2. Dried, powdered herbs as previously described were mixed together in the following amounts: 10 kg S. aromaticum, 4 kg M. fragrans and 6 kg P. anisum. Preliminary experiments were performed to determine an appropriate rate of application. For the experiment reported here, the dry herbal mixture was evenly scattered as a powder on a surface of seawater at rate of 750 g per I square meter. After allowing the powdered herbal mixture to be distributed in the seawater for one minute, samples of 10 ml of the seawater were examined and numbers of red tides cells were checked microscopically and recorded.

RESULTS

The microscope examination method has shown the presence of eight different algae species in the 20 square meters of seawater these are Cochiodinium polykrikoides, Karenia mikimoto Prorocent rum micans, Dinophysis caudate, Pyrodinium bahamense, Gymnodinium catenatum, Ceratium furca and Ceratium fusus in average of approximately >7 x i05 cells m11 in which the Cochiodinium polykrikoides is the dominant species and it was found at I i05 cells m11. However, the number of algae species on the surface of seawater was approximately >7 x i05 cells mr1, meanwhile, the number of algae was reduced gradually to I x iQ3 cells m11 and I x 102 cells m11 at depths 1 and 2 meters, respectively. The seawater temperature was 26.8°C � 2.

The results set out in Table 2 indicate that there is 3 log reduction of HABs obtained after 2 mm on surface of the seawater after the addition of herbal mixture formula 2 comprised from Syzygium aromaticum 0.5%, Myristica fragrans 0.2% and Pimpinella anisum 0.3%. Whilst there are only 2 and I log reduction in cells of HABs at 20 and 50 cm, respectively. This was probably due to normally water flux from the bottom. The results suggest that the higher death occurred at seawater surface.

Furthermore, it was noticed after the addition of powdered herbal mixture the clarity of seawater had increased for few seconds. On the other hand, some floated herbal mixture drifted for 100 meter from the treated area; this was probably due to normally water flow, however, the number of HABs reduced by 95%.

Table 2. Survival (cells mr1) of Cochiodinium polykrikoides and other red tides algae in open seawater treated with 750g of formula 2 (Syzygium aromaticum 0.5%, Myristica fragrans 0.2% and PimpInella anisum 0.3%) per I square meter.

Depth of Cells m11 of HABs in seawater seawater After 2 mm from the Control untreated I square from surface addition of formula 2 meter of seawater (cm) At the surface >1 x I 2 cells mr1 >7 x I Qb cells m11 cm >1 x 10 cells mr1 >7 x lOb cells m11 cm >7 I O cells mr1 >7 x I Qb cells m11

CONCLUSION

The results confirm that the Pimpinella anisum, Myristica fragrans and Syzygium aromaticum anti-harmful algal bloom agent is an environmentally safe, target-specific product for controlling red tides in wildlife mortalities among marine and coastal species of fish, birds, marine mammals and other organisms.

None of the herbs Pim pine/Ia anisum, Myristica fragrans and Syzygium aromaticum, nor any other herbal material, has been investigated previously in the literatures as anti-red tides. It appears that all herbs used in this invention have shown as effective anti-red tides in which Syzygium aromaticum has shown strong anti-red tides activity.

The red tideicide activity of Pimpine/la anisum, Myristica fragrans and Syzygium aromaticum has been further studied in the open sea and shows to be an effective, fast-acting method to be used to treat HABs. The maximum reduction of HABs has occurred at the seawater surface despite the presence of normal water flow and surface wind speed. Because these algae are phytoplankton, i.e. autotrophic, they require light for photosynthesis and therefore live near the water's surface which is where blooms form. The algicidal compositions of the invention can therefore be effective in the control of HABs when applied to the water's surface.

Algae-toxic compounds of the Pimpine/la anisum, Myristica fragrans and Syzygium aromaticum plants will be investigated. We are assuming that the modes of action of these compounds are complex, and a number of mechanisms in relation to red tides management are yet to be fully explored.

References Fukuyo, Y., H. Takano, M. Chihara and K. Matsuoka 1990. Red Tide Organisms in Japan. An Illustrated Taxonomic Guide. Uchida Rokakuho, Co., Ltd., Tokyo. 407 pp. Fukuyo Y, Imai I, Kodama M, Tamai K (2002) Red tides and other harmful algal blooms in Japan. In: Harmful Algal Blooms in the PICES Region of the North Pacific, PICES Scientific Report No. 23 (eds Max-Taylor FJR, Trainer VL).

Institute of Ocean Sciences, Sidney, Canada, pp. 7-20.

Gobler C.J.,.Berry, D.L., Anderson, O.R., Burson, A, Koch, F., . Rodgers, B.S., Moore, L.K., Goleski, J.A., Allam, B., Bowser, P., Tang, Y. and Nuzzi, R. 2008. Characterization, dynamics, and ecological impacts of harmful Cochiodinium polykrikoides blooms on eastern Long Island, NY, USA.

Harmful Algae. 7:293-307.

Ho, M.-S. and P.L. Zubkoff 1979. The effects of a Cochiodinium heterolobatum bloom on the survival and calcium uptake by larvae of the American oyster, Crassostrea virginica. In: D.L. Taylor and H.H. Selinger (eds), Toxic Dinoflagellate Blooms, Elsevier I North-Holland, New York: 409-412.

Imali, I., Yamaguchi, M and Hori, Y. 2006. Eutrophication and occurrences of harmful algal blooms in the Seto Inland Sea, Japan. Plankton Benthos Res 1:71-84.

Jeong, H.J., Kim, J.S., Yoo, Y.D., Kim, S.T., Song, J.Y., Kim, T.H., Seong, K.A., Kang, N.S., Kim, M.S., Kim, J.H., Kim, S., Ryu, J., Lee, H.M. and Yih, W.H.

2008. Control of the harmful alga Cochiodinium polykrikoides by the naked ciliate Strombidinopsisjeokjo in mesocosm enclosures. Harmful Algae. 7:368-377.

Kim, H.G. 1998. Cochlodinium polykrikoides blooms in Korean coastal waters and their mitigation. In: B. Reguera, J. Blanco, Ma L. Fernandez and T. Wyatt (eds.), Harmful Algae, Xunta de Galicia and Intergovernmental Oceanographic Commission of UNESCO, Spain: 227-228.

Margalef, R. 1961. Hidrografia y fitoplancton de un area marina de Ia costa meridional de Puerto Rico. mv. Pesq. 18: 76, 78.

Shirota, A. 1989. Red tide problem and countermeasures (2). mt. J. Aq. Fish.

Technol. 1: 195-223.

Silva, E.S. 1967. Cochlodinium heterolabatum n.sp.: Structure and some cytophysiological aspects. J. Protozool. 14: 745-754.

Song, W.; Teshiba 1., Rein K., and O'Shea K. E. 2005. "Ultrasonically induced degradation and detoxification of microcystin-LR (cyanobacterial toxin)".

Environ. Sd. Technol 39 (16): 6300-6305.

Steidinger, K.A. and K. Tangen 1996. Dinoflagellates. In: C.R. Tomas (ed.), Identifying Marine Diatoms and Dinoflagellates, Academic Press, New York: 387-598.

Taylor, F.J.R., Y. Fukuyo and J. Larsen 1995. Taxonomy of harmful dinoflagellates. In: G.M. Hallegraeff, D.M. Anderson and A.D. Cembella (eds.), Manual on Harmful Marine Microalgae, IOC Manuals and Guides No. 33. UNESCO, France: 283-31 7.

Yuki, K. and S. Yoshimatsu. 1989. Two fish-killing species of Cochlodinium from Harima-Nada, Seto.

Zubkoff, P.L., J.C. Munday, Jr., R.G. Rhodes and J.E. Warinner, III 1979.

Mesoscale features of summer (1975-1 977) dinoflagellate blooms in the York River, Virginia (Chesapeake Bay Estuary). In: D.L. Taylor and H.H. Seliger (eds.), Toxic Dinoflagellate Blooms, Elsevier/North-Holland, New York: 279-286.

Claims (14)

1. Claims 1. A method for treating or preventing harmful algal bloom, which comprises applying to the affected or susceptible waters a composition comprising a preparation or extract of one or more plants selected from the group of Pim pine/la anisum, Myristica fragrans and Syzygium aromaticum.
2. 2. A method according to claim 1, wherein the composition comprises a preparation or extract of Syzygium aromaticum.
3. 3. A method according to claim 2, wherein the composition further comprises a preparation or extract of Pim pine/Ia anisum or Myristica fragrans.
4. 4. A method according to claim 1, wherein the composition comprises a preparation or extract of each of Pimpine/la anisum, Myristica fragrans and Syzygium aroma ticum.
5. 5. A method according to any preceding claim, wherein the or each preparation is powdered dried plant material.
6. 6. A method according to claim 5, wherein the plant material is flower, fruit or seed.
7. 7. A method according to any of claims I to 6, wherein the composition is applied to seawater.
8. 8. A method according to any of claims I to 7, wherein the harmful algal bloom comprises Coch/odinium po/ykrikoides.
9. 9. A method for killing Coch/odinium spp., which comprises treating the organism with a composition comprising a preparation or extract of one or more plants selected from the group of Pimpinella anisum, Myristica fragrans and Syzygium aromaticum.
10. 10. A method according to claim 9, wherein the Cochiodinium sp. is Cochlodinium polykrikoides.
11. 11. A method for disinfecting vessels and other marine tools, instruments and facilities contaminated with harmful algal bloom, which comprises applying to the vessels, tools, instruments or facilities a composition comprising a preparation or extract of one or more plants selected from the group of Pim pine/la anisum, Myristica fragrans and Syzygium aromaticum.
12. 12. An algicidal formulation comprising a preparation or extract of one or more plants selected from the group of Pimpinella anisum, Myristica fragrans and Syzygium aromaticum, and one or more vehicles, carriers, binders or excipients.
13. 13. Use of an algicidal formulation according to claim 12 for the treatment or prevention of red tides in open seawater.
14. 14. Use of an algicidal formulation according to claim 12 for the disinfection of vessels and other marine tools, instruments and facilities contaminated with harmful algal bloom.