Ghana is a signatory to the 1982 United Nation’s Convention on The Law of the Sea (UNCLOS 82) and marks its Territorial waters 12NM out like any other coastal nation from the baseline along the coast. This is the region of the first-ever findings of algae bloom conducted by the Environmental Protection Agency (EPA) in 1995, though not conclusive as to the real cause, they were of the view that toxic waste chemicals dammed into the sea in Cote d’Ivoire one way or the other are the origin of the bloom (EPA, 1995; Myjoyonline.com, 2014). The problem has since been under monitoring.
2.1 Growth and Conditions of Growth of the Algae Species
Algae are an important life form in the ocean. Life in the ocean is maintained in balance by forces of nature and by predator-prey relationships unless some external pressures upset the balance. When a balance upset leads to conditions more favourable for the reproduction and growth of algae, an explosive increase in the number of algae cell density occurs. Such rapid increases in the algae population are called ‘algal blooms’. The most widely publicized type of algal bloom species is that associated with the production of toxin (chemical substance) harmful to animals that feed on them (and hence is known as a harmful algal bloom or HAB), and/or algae bloom that cause a tint in the water because of the photosynthetic pigments they contain. The latter commonly is known as a "red tide," and may or may not be harmful. They nonetheless affect life in the ocean and on land in both positive and negative manner (Castro and Huber, 1997; Wells, M. L., et al, 2015). Bulent S., et al, (2013) also indicated that “in very high densities (algal blooms), these algae may discolour the water and outcompete, poison, or asphyxiate other life forms.”
Algae are typically one of the few types of phytoplankton species that grow in freshwater as well as marine bodies. Algae need light and food in order to thrive and grow. Hence, Castro and Huber (1997); Wells, M. L., et al, (2015), lists air temperature, humidity, sunlight, and nutrients (food) as their growth factor to grow and reproduce. Its habitation is mostly within 60 to 90 meters (200 to 300 feet) of ocean water surface forming the epipelagic zone –rich in oxygen, easily penetrated by sunlight and warmer than water at lower levels. Some algae such as Naviculapennata have been recorded to a depth of 360 m (thus according to Bulent S., et al, 2013).
2.2 Types of Algae
On the basis of their habitat, algae can be categorized as aquatic (planktonic, benthic, marine, freshwater, lentic, lotic), terrestrial, aerial (subaerial), lithophytic, halophytic (or euryhaline), psammon, thermophilic, cryophilic, epibiont (epiphytic, epizoic), endosymbiont (endophytic, endozoic), parasitic, calcifilic or lichenic (phycobiont) (Bulent S., et al, 2013).
Although there are over 20,000 known varieties of algae, algae can be classified into two (2) main categories namely harmful or toxic algal blooms (HABs) and non-harmful or non-toxic algal blooms. These blooms occur due to an imbalance in the environment which causes algae to bloom in large numbers owing to the abundance of nutrients. However, they are not toxic and therefore pose no direct harm to aquatic or marine life as well as humans. However, the harmful/toxic algae blooms (HABs) is only 2% of all the 5000+ species of marine phytoplankton that exist worldwide. Blooms of harmful algae can have large and varied impacts on marine ecosystems, depending on the species involved, the environment where they are found, and the mechanism by which they exert negative effects. Due to their negative economic and health impacts, HABs are often carefully monitored. The “Red tide” is a term often used to describe HABs in marine coastal areas, as the dinoflagellate species involved in HABs are often red or brown, and tint the seawater to a reddish colour. The more correct and preferred term in use is harmful algal bloom, because: these blooms are not associated with tides, but causes reddish discolouration of water and are harmful.
2.3 Causes of HABs’ Migration
It is unclear what causes HABs; their occurrence in some locations appears to be entirely natural (Doucette and Kirkpatrick, 2003). While in others they appear to be a result of human activities. Furthermore, many different species of algae can form HABs, each with different environmental requirements for optimal growth. The frequency and severity of HABs in some parts of the world have been linked to increased nutrient loading from human activities. According to Bulent et al, (2013) “Algae can be used as indicator organisms to monitor pollution in various aquatic systems. In many cases, algal metabolism is sensitive to various pollutants. Due to this, the species composition of algal populations may shift in the presence of chemical pollutants.”
In other areas, HABs are a predictable seasonal occurrence resulting from coastal upwelling, a natural result of the movement of certain ocean currents. The growth of marine phytoplankton (both non-toxic and toxic) is generally limited by the availability of nitrates and phosphates, which can be abundant in coastal upwelling zones as well as in agricultural run-off. The type of nitrates and phosphates available in the system is also a factor since phytoplankton can grow at different rates depending on the relative abundance of these substances (e.g. ammonia, urea, nitrate ion). A variety of other nutrient sources can also play an important role in affecting algal bloom formation, including iron, silica or carbon.
Coastal water pollution produced by humans and systematic increase in seawater temperature has also been suggested as possible contributing factors in HABs. Other factors such as iron-rich dust influx from large desert areas such as the Sahara are thought to play a role in causing HABs. Some algal blooms on the Pacific coast have also been linked to natural occurrences of large-scale climatic oscillations such as El Niño events. While HABs in the Gulf of Mexico have been occurring since the time of early explorers such as Cabeza de Vaca, it is unclear what initiates these blooms and how large a role anthropogenic and natural factors play in their development. It is also unclear whether the apparent increase in frequency and severity of HABs in various parts of the world is a real increase or is due to increased observation effort and advances in species identification technology.
2.4 Possible Causes of the Increase in HABs
The frequency, duration, and intensity of algal blooms are related to many biological, chemical, and physical factors, although, many of these complex relationships have not yet been identified. Four possible reasons have been advanced for the increased frequency and expanding geographic occurrence of HABs. First are improved methods of detection and greater monitoring efforts. These increase the probability that a HAB species will be recorded. Second is the introduction of exotic species via ballast water exchange or aquaculture practices (Hallegraeff, 1993; Damak, 2017). A third possibility is that blooms result when grazers fail to control the algae species' growth (Smayda, T. J., 1997). Fourth, blooms may result from climate changes, as well as human activities, such as increased pollution and nutrient inputs, habitat degradation including dredging, resource harvesting, and the regulation of water flows (reference). All of these reasons are possible explanations for increasing HABs, and one or any combination of them may apply to a particular species.
2.5 Effects of Algal Bloom
Algal blooms provide large concentrations of algae that produce organic compounds needed by higher organisms, ranging from oysters, clams, and mussels to human beings. For this reason, productivity increases in areas where algal blooms occur. More algae in the water mean that more carbon dioxide is used from the atmosphere and that more oxygen is released into the atmosphere. Oxygen is necessary for many living things, including humans. The production of dimethyl sulphide gas helps protect algae from harmful ultraviolet rays so they remain healthy and thus can continue the cycle of sustaining life on Earth. Even in the coldest parts of the ocean, algae provide the primary source of organic material to animals at the bottom of the food chain. Organic materials are moved up the food chain as higher organisms feed on those lower down the chain. For example, algae have been found in Antarctic sea ice. As seawater freezes, algae living in the water are frozen in the ice, where they later can be released during a thaw. These algae are a vital source of food for krill, the shrimp-like organisms eaten by penguins, seals, seabirds, and whales. However, the negative effects or disadvantages of algal blooms will be considered under the following classifications:
- Human Health and Environmental Effects of Harmful Algal Blooms: The detrimental effects range from cell and tissue damage to organism mortality, and can be caused by several mechanisms, thus toxin production, predation, particle irritation, induced starvation, and localized anoxic conditions. As a result, their impact is on living organisms of the coastal ecosystem, from zooplankton, fish larvae to humans.
- The Social and Economic impacts of Algal Bloom: can lead to disruption of recreational use of the waterway – impeding modes of transport and beaches thereby posing serious threats to tourism. This is buttress by Turgeon et al.’s (1998); US Commission on Ocean Policy (2004) assertion that expansion of harmful algal blooms over 25 years along the US coast was responsible for economic losses amounting to US$100 million per each year by the United State federal government. To this effect, Murkute and Chavan (2018) in their finding observed that the mass of fish kill studied occurred in the Lendra Pond with a heavy load of algal blooms, of which its decaying resulted in the depletion of Dissolved Oxygen and subsequently the release of toxins. Again, a single outbreak of paralytic shellfish poisoning in the North-eastern United States was estimated to cost six million US dollars (the US $6 million) (Shumway, 1988; Bulent, et al, (2013)). Even the non-toxic harmful algal bloom can also have devastating effects on a natural bio-diverse community (LaPointe, 1997; Littler, 2006). Such sea-grass beds are important nursery habitat for pink shrimp, spiny lobster, and finfish.
2.6 Management of Algal Bloom
Notable Occurrences: a red tide in 1972 was caused in New England by a toxic dinoflagellate Alexandrium. February 2002, also saw massive die-off and decay of algae from a nearshore HAB, causing a rapid reduction in dissolved oxygen concentration, driving tens of thousands of rock lobsters to "walk out of the sea" near the Elands Bay in South Africa's West Cape province.
Control Measures: the most direct way of control algal blooms is to reduce the availability of nutrients. Water management organizations across the world are actively pursuing a variety of nutrient control strategies. However, for some aquatic ecosystems nutrient control, is impractical, ineffective or is simply too costly. In other cases, chemical or biological treatments are helpful alternatives when administered properly.
(i) Chemical Treatment: involves the administering of chemicals (algaecides include sodium carbonate proxyhydrate products, Green Clean™ and Pak 27™, etc.) to affected water bodies. Some have proven to be effective while others have posed a danger to marine life. Therefore, each chemical has its restrictions and toxicity to animals. Before using these chemicals, it is expected that the manufacturer’s directions are adhered to carefully hence a consulting professional advice is crucial.
(ii) Biological Treatment: is the use of various carp fish species to control submerged and floating algae. Grass carp (Ctenopharyngodon Idella) is mainly used for aquatic weeds and attached submerged algae, such as Nitella sp. and Chara sp. Where they do not prefer filamentous algae to eat, grass carp will eat Lyngbya. The silver carp (Hypophthalmichthys molitrix) is an effective treatment for controlling filamentous algae, including blue-green algae. However, both species are non-native species and have several regulatory restrictions to employing them as a means of weed control. When they are allowed, they are restricted to triploid carp. Triploid carp has an extra set of chromosomes that render the fish sterile, therefore prohibiting a population explosion if the fish escapes into an uncontrolled area. These fishes are an economical choice and thus have proven their effectiveness in controlling the growth and spread of algae. However, there is a mixed outcome (e.g. grass carp tend to consume non-nuisance vegetation— leaving the noxious algae as the second choice) when using carp for blooms control. It is not clear why preferences change between lakes over time.
(iii) Physical Treatments in ponds include aeration and airlifts. While aeration does not kill or remove algae from the water, it oxygenates and stirs the water column, creating the conditional shift from toxic and smelly blue-green algae to preferred green algae species. The resultant algal population is usually not dense or toxic to other organisms within the ponds.
(iv) Mechanical Treatments: Harvesters are sometimes used to skim dense mats of blue-green lyngbya algae from the surface of lakes and rivers. Lyngbya normally grows in dense mats at the bottoms of nutrient-enriched lakes and spring-fed systems. These mats produce gasses during photosynthesis that often cause the mats to rise to the surface. At the surface, the winds pile the algal mats against shorelines or in navigation channels. These mats can be several acres in size. Managers have developed a process called "grubbing" whereby harvesting machines lift the mats off submerged plants such as native eelgrass, without cutting the eelgrass. By removing the blanket of lyngbya from the eelgrass, the plants grow and expand.
(v) Alternative Control Measures: Phosphorus inactivation products (aluminium sulphate, sodium aluminates, and calcium hydroxide/carbon dioxide) generally limits the growth of freshwater algae in most lakes. A direct relationship exists between the amount of phosphorus in a lake and the quantum of algae bloom site growing in the lake. As phosphorus levels increase, the amount of algae increases too. Long-term management of algae requires the removal of phosphorus sources to the water body. External sources of phosphorus are storm-water runoff, septic system effluents, fertilizers, pet wastes, waterfowl, agriculture, and even rainfall. Removing or modifying the phosphorus sources as possible is even not enough. Phosphorus-enriched sediments can simply release phosphorus into the water through a process known as ‘internal loading.’ In this situation, lake managers can use nutrient inactivation techniques to remove the phosphorus from the water column (called precipitation) and to retard its release from the sediments (called inactivation). Lake managers introduce either aluminium, iron, or calcium salts for phosphorus inactivation of lake sediments. However, Aluminium sulphate (alum) is the most commonly used nutrient inactivation chemical for lake projects. When applied, alum forms a fluffy aluminium hydroxide precipitate called a floc. As the floc settles, it removes phosphorus and particulates (including algae) from the water column (precipitation). The floc settles on the sediment where it forms a layer that acts as a barrier to phosphorus. As sediments release phosphorus, it combines with the alum and is not released into the water to fuel algal blooms (inactivation). Nutrient inactivation is only appropriate where internal loading is a significant phosphorus source. For appropriate nutrient inactivation projects, the length of treatment effectiveness varies with the amount of alum applied and the depth of the lake. Thus, for the shallow lake, the amount of alum required for phosphorous inactivation per a lake’s depth if applied adequately should last for a period of eight to ten years or more respectively (E. B. Welch, and G. D. Cooke, 1999).