INTRODUCTION

20.1.1 COASTAL ENVIRONMENT

Many countries have a long distance of coasts, such as India (Verlecar and Desai, 2004). This environment is usually a significant part, also or significant element, and this environment varies from one place to another, depending upon the extent to which it affects or is directly affected by coastal processes and the management issue. It includes three distinct areas, but they are interrelated: The coastal marine area, the active coastal zone, and the land backdrop (Jessim, 2009). Therefore, for diagnosis of the environment or assessment for the impacts of urban activities now is a general concern and also it gives a good evaluation to represent a real hard challenge. Through the last decades, the identification of indicators that represent stress upon phytoplankton population has been searched through intensive efforts. Generally, there are several signs that should be taken in consideration for health assessment of an aquatic ecosystem, for example, species diversity, biotic of community structure, length of the food chain, and stability of population (Gianesella et al., 1999). The term Phytoplankton is referring to the number of species, such as Diatoms, Dinoflagellates, Blue-green algae, Silicoflagellates, Cocolithophors, etc., representing about 59% from the primary products in the oceans and considered as first ring of the food chain. Then, secondaiy production Zooplankton depends on phytoplankton, then third production, such as fish, shellfish, mammals and other, depends on productions of marine (Verlecar and Desai, 2004).

The development of phytoplankton population depends upon certain micronutrients that are required in high enough concentration to support population growth of phytoplankton. In marine environment, nitrogen (n) generally is considered to be a limiting nutrient, although, phosphorus (p) and silicon (Si) also require in varying quantities from certain phytoplanktonic groups (Hydes et al., 2004), In addition, due to human activities, coastal areas were and are a real subject of eutrophication that comes from increasing the inputs of inorganic elements, like phosphorus (P), which is with another 16 elements are essential for growth of plant, also the organic compounds, such as Urea, which is available from dissolved organic nitrogen in the marine environment (Fouko et al., 2006). Increase of phosphorus at the surface of water comes from high-soil phosphorous, anthropogenic inputs (agricultural and industrial) in addition the conditions that can transport phosphorus to the surface of the water (Mullins, 2001). Then, Silicon (Si) is a control and effective element and most common that limits primary production at both coastal and freshwater ecosystem (Tallberg, 1999). Si found as a nutrient governing the total primary production, globally, of the world’s oceans and it has been emphasized that possibly Si drawdowns carbon dioxide (Tallberg, 2000). Lately, the studies now have gone intensively in the relationship and interactions between Si and the other elements, particularly P, at particle surfaces the effects have given a little attention (Tallberg, 2000). Later Morre et al. (2006) referred to iron (Fe) as a supplied by dust deposition has shown to be an important factor control dynamics of phytoplankton development at spring blooms. In addition to nutrients, physical factors can affect strongly phytoplankton development, like wind and temperature in coastal lagoons (Pilkaityte and Razinkovas, 2006). Blooms can occur and develop over a wide range of salinity but, actually, there is an optimal salinity for high cellular densities, significant and problematic growth of phytoplankton species that are able to synthesize a toxic bioactive compound to humans (Fauchot et al., 2005; Delia et al., 2015). In other studies, researchers found the growth of pulses of toxic species affected and are associated with high solar radiation, low speeds of wind, and shallow mixed layer (Bleiker and Schanz, 1988; Hader et al., 2015).

At coastal lagoons and coastal areas, eutrophication environments receiving high- nutrient inputs from anthropogenic sources and from autochthonous origin that keeps primary production high, for both as benthic and planktonic. The environmental features of lagoons shallow waters, a strong seasonal gradient of temperature, salinity, and wind or tidal effects, were studied well and found veiy high variable compared with short spatial and temporal scales (Nuccio et al., 2003; Bonilla-Gomez et al., 2013). In addition to above, there are also relation of the chemical and physical factors that can cause eutrophication of coastal waters, one of most important ecological consequences of aquatic pollution, which is a main reason of occurrence for massive growth of toxic algal blooms [harmful algal blooms (HABs)], often called red tides. This massive growth of phytoplankton mostly represents dinoflagellates and may produce highly toxic products that can cause illness and even death for aquatic organisms as well as humans (Andersone et al., 2002; Santi Delia et al., 2015).

20.1.2 HARMFUL ALGAL BLOOMS

HABs is a term that refers to a heterogeneous development of events that share two characteristics caused by microalgae and they have a negative impact on human health and activities. Algal blooms occur when phytoplankton grows at a rate that is harmful and detrimental to the other living forms.

Ecophysiological requirements for the most harmful species need more studies to be known well and need further laboratory studies to learn more about this field. Unfortunately, results from laboratory studies are not sufficient to predict the succession of phytoplankton species and blooms of specific harmful organisms in the sea. Indeed, the net growth performance of the species is affected by complex interactions with other organisms, which are scarcely reproducible in laboratory experiments. These include a negative interaction, such as grazing competition, viral infections, and positive feedback from predator excretions, bacterial nutrients regeneration, and viral lysis. In fact, the evidence of phytoplankton life strategies and their interactions with surrounding environment has increased and may reach a degree of unexpected complexity for unicellular organisms. The capability of the species to adapt with an environmental condition apparently not matching their optimal range is notably expanded and its occurrence is more difficult to predict (Zingone and Enevoldsen, 2000).

The term “Bloom” has been defined as “the rapid growth of one or more species in the same area of water that leads to a nuisance increase in tire biomass of the species” (Smayda, 1997; Richardson, 1997; Arroyo and Bonsdorff, 2016).

HABs are an increasing phenomenon because of the massive growth of phytoplankton throughout coastal waters worldwide (Gastrich, 2000; Piuz et al., 2008). Globally, concern over an apparent increase of HABs, especially toward blooms occurring near the shores and affecting important fisheries and marine culture operations, has prompted research to control HABs and mitigation in an effort to reduce the ecological and economic impacts that they cause (Archambalut et al., 2002; France and mozetic, 2006). There are many questions about toxic phytoplankton when they bloom and become HABs. What is a harmful bloom? How abundant do a harmful species have to be harmful? Are its harmful effects density-dependent? Blooms have been regarded as a significant massive increase in the number of individuals of the phytoplankton population without concern over magnitude or impacts. Recognition that harmful species can represent a broad spectrum of antagonistic properties relative to the blooms of other species that has been stimulated efforts and distinguished formally between such different bloom types while this has broadened insights into the nature of phytoplankton blooms, also it has revealed widespread confusion concerning (What is a bloom) also how it is to be defined, this becomes even more problematic when efforts to defined a bloom in the terms of abundance are linked to a descriptor, such as an exceptional bloom (Smayda, 1997; Maso and Garce, 2006). HABs pose a serious threat and impact negatively the commercial fisheries and aquaculture, human health, and coastal aesthetics because of the water discoloration and accumulation of foam and mucilage on the coast producing unpleasant odors (Anderson, 1997; Anderson et al., 2001; Boesch et al., 1997; Beaulieu et al., 2005). HABs include a microscopic species, which is usually single cell, eukaryotes that live in estuarine and marine waters. Among 5000 marine phytoplankton recorded species, approximately 300 can occur in such high numbers (blooming) which obviously discolor the surface of the sea, the so-called “red tides” (Hallegraeff et al., 1995; Lindahl, 1998). Visible red tides may contain phytoplankton individuals from 20,000 to >50,000 cell mL'1 of seawater; however, concentrations as low as 200 cell mL'1 may produce toxic shellfish (Connell, 2007; Smith, 1992). When the conditions of temperature, light, nutrients, and salinity of water are appropriate, the cysts of dinoflagellates, which is one of red tide members, for example, germinate and causes swimming cells, then reproduces by simple division within few days. If the conditions remain optimal, cells will continue growing exponentially, so from one cell up to 6000-8000 cells can be produced in a week. When the appropriate environmental conditions are no longer available, growth rates are gradually reduced and the gametes are foimed, two gametes join to form a cell that develops into a zygote and then into a new cyst that falls to the ocean bottom, ready to germinate when conditions pennit (Daranas et al., 2001), HABs’ increase worldwide has been related to increase in aquatic nutrient concentrations from human activities (Tango et al., 2003; Sengco and Anderson, 2004). The data indicate that these phenomena are on the rise worldwide, hence estuarine and near coastal researchers have begun to invest an increasing amount of time and other resources in efforts to characterize this phenomenon and understand what causes them (Scatasta et al., 2001). All world sites including Middle and South Tyrrhenian Sea waters, Australasian Region, Danish waters, the North Sea, South Africa, northeast American coasts, northwest American coasts, and Vietnam with detailed lists of harmful algal species have been published. Despite notable differences in size among the areas considered, the total numbers of harmful species are comparatively high. Harmful microflora is varying among these sites obviously, more than nontoxic species are concerned. Furthermore, in these types of studies, the diversity of harmful microflora parallels the pattern generally observed for the whole phytoplankton diversity at single site and also with the micro floral diversity where a significant number of cosmopolitan species found in addition to species which are more restricted. As already postulated by earlier authors, they proved that there are many species of phytoplankton are cosmopolitan but not all of them are identified or diagnosed at many places yet, which resulted in nonactive local microflora (Zingone et al., 2006; Congestri et al., 2006). In the Arabian area, the countries located near waters bodies and Arabian sea, have experienced massive marine mortality that caused as natural phenomenon or by manmade due to anthropogenic inputs like domestic and industrial wastes. HABs have been associated with some of the frequent episodes of seafood contamination, sometimes with very serious consequences for human health and associated with economic losses, such as in Kuwait and Iran at the period of 1999-2001, Oman in 1999-2002, Saudi Arabia in 2003, and Qatar during 2008. Particularly, in Qatari waters, benthic HABs events have been recorded due to the development of Coolia monotis, C. tropicalis, Gambierdiscus toxicus, Lingulodinium polyedrum, Ostreopsis lenticularis, Prorocentrum balticum, P. convacum, and P emarginatum. At same waters, Dinophysis miles and D. catidata, were described as dominant species together with Ceratium furca, Prorocentrum sigmoides, and P. micans, but the Trichodesmium erythraeum was found usually to persist for a long period and Perodinium bahamenes, also V. compresum, was found in a large number of samples (Al-Muftah, 2008). During September-October, blooms of Karenia sp. were implicated in the mortality of 30 tons from wild mullets and 150 tons from caged sea bream fish at a cost of $7 million (Subba Rao et al., 2003), during the year 2000 A.D. Two red-water episodes have occurred that were ephemeral and massive, about two billion cells L'1 with patches were extending from 50 nr to 15x104 m2. Here, the dominant species differed each time, for example, Prorocentrum spp., Pseudo-nitzschia seriata, Nitzschia longissimi, Leptocylindrus sp., and Trichodesmium erythraeum. Experimental growth studies, an eoliak dust rich in essential micronutrients for the growth of phytoplankton had a positive effect on summer growth of phytoplankton, which is similar to the red tied proportions (Subba Rao et al., 2003). Researchers described and isolated into culture new species of potentially harmful algae from HABs in United Arab Emirates area, as Ostreopsis labens, Prorocentrum norrisianum, P faustioe, P. arabianium, P. reniformis, Pfiesteria shwmvoyiae, Protoperidiniwnponticum, and Ostreopsis tholus (Morton et al., 2002). Omani waters had shown a wide range of two HABs groups of phytoplankton, diatoms, and dinoflagellates. The diatom group included Coscinodiscns marginatus, C. ocidus irids, Biddulphia aiirita, Asteromphalus cleceanus, A.flsbeUatus, Melosira radiate, M. coronate, Planktoniella sol, Thalasssiosira decipiena, Nitzschia ap., Pleurosignia directum, Chaetoceros ap., Rhizosolenia sp.. R. imbricate, R. alata, Guinardia flaccida, Fragilaria oceanica, and Bcteriastrum hyalinum, and dinoflageUate group including Noctiluca scintoUans, Ceratium furca, C. fustts, C. massiliense var. protuberans, C. niassiliense var. massiliense, C. falcatiforme, C. tripos, C. belone, C. trichoceros, Amphisolenia bidentate, Gymnodinium sp., Prorocentrum micans, Pyrophacus horologicum, Dinophvsis caudata, D. cuneus, and Gonyaulax diegensis (Thangaraja et al., 2007).

 
Source
< Prev   CONTENTS   Source   Next >