**13. Manifestation of climate change and HABs**

Climate change is negatively impacting health and leading to harmful transformation in aquatic ecosystems [70, 71]. Rising temperatures leading to acidification and oxygenation which alters basal metabolic functioning and species distributions along with the timing of essential biological activities [72, 73]. Due to acidification physiological stress found to increase among sensitive marine species along with growth inhibition of calcifying organisms. As ocean deoxygenation alters the distribution and survival of aquatic organisms [74, 75]. This further alters structure and functioning of marine and freshwater ecosystems. Temperatures rise have predictable impact on the occurrence and concentration of marine diseases, habitat loss, including ocean deoxygenation inviting various environmental contaminants [76, 77]. As increased level of carbon dioxide in atmosphere has generated decreased value of pH in surface waters, offshore, coastal and upwelling marine

regions, including freshwater environments [78, 79]. Decreased pH shifts the carbonate system to decrease bicarbonate concentrations and increases dissolved CO2, thereby increasing carbon availability for photosynthesis [80]. Now such process downgrades the value of metabolically costly carbon-concentrating-mechanisms so that many species of phytoplankton evolved change that may alter the competitive balance among the species [81]. Climate change is now shifting the occurrence and distribution of marine species of various organisms around the world. Therefore frequency and impact of algal blooms have considerably increased around the world in recent decades [82]. Human modifications of the environment such as port construction, release of contaminated water, enriching nutrient by recreation, tourism, fishery, aquaculture, impacts harmful algal contributions [83]. As the reason HABs are now migrating to new ecosystems, therefore considerable risk to aquatic ecosystems and the humans is also found to increase. There is no doubt that oceans are getting warm because of accumulation of CO2 in the atmosphere through various activities [78]. Elevated CO2 offers the potential to rebalance the distribution of primary producers that rely upon inorganic carbon for performing photosynthesis [84]. Hence co-occurrence of climate change stressors and their physiological impacts have been in continue study from the past decade, excessive level of biomass generated creates high levels of organic matter which, when respired, promotes hypoxia and acidification [85].

Coastal zones are host to a varied type of aquatic life and are known dynamic ecosystems [86]. Such locations found to be impacted by climate change as several coastal regions are getting warm hastily than the open-ocean [87]. It is also important to note that coastal areas are also prone to eutrophication, acting as stressors, as unnecessary nutrient loading promotes HABs [88]. As result of ecological changes spring diatom blooms within temperate latitudes, surface waters speedily warm and stratify, which isolates bottom waters from surface influxes of dissolved oxygen and lowers CO2 water, making the condition promoting concurrent hypoxia and acidification [89]. Various HABs flourish in stratified water columns, in late spring and early-summer time's stressor-sensitive, early-life stages of many aquatic genera/ species are present in coastal systems [90, 91]. Because of migrating of HABs to new ecosystems native species, experience selective pressures and consequently suffer the greatest population declines [92]. Generally Cyanobacterial HABs are associated with fresh to brackish water, even though blooms of *Trichodesmium* sp. and *Lyngbyaa* sp. in saline tropical and subtropical waters are considered as harmful mainly in Asian and South Pacific nations. Were Cyanobacterial HABs in the marine and freshwater bodies gets worsened due to elevated anthropogenic nutrients that can be the consequences of regional and local population density. Evidence shows that Cyanobacterial HABs are enhanced by elevated temperature [93], Likewise, elevated CO2 leads to increased growth rates of Cyanobacteria. But surplus inputs of N and P relative to Si shifts the conception from eukaryotic like diatom to Cyanobacteria creation. Noteworthy finding shows that internal loading of phosphorus together with decreasing N:P ratios able to enhance blooms of nitrogenfixing Cyanobacteria over the other phytoplankton at some area like Baltic Sea.

HABs species too have harmful effects solely on fish other invertebrates. Variety of planktonic algae forms HABs which are associated with killing of fish in nature [94–96]. Example algal blooms of planktonic fish killers haptophyte *Prymnesium parvum,* has caused fish killing blooms worldwide since the first recorded bloom in Danish waters in the 1930s. Some studies show that HABs effects physiology of fish indicating respiratory effect. Evidence shows that on exposure of fish to *P. parvum* reflects toxic effects related to fish gill damage. *P. parvum* exposure may effects fish health as increase in gill permeability found to cause sensitivity to subsequent secondary toxicity, as well as effects of hemolysis and anti-coagulant being

**47**

**14. Conclusion**

*Considering Harmful Algal Blooms*

generating Global HAB Status.

*DOI: http://dx.doi.org/10.5772/intechopen.94771*

noted [97, 98]. Even mammals and birds exposed to Cyanobacterial toxins may become ill or sometimes die. Records show that when other bacteria in the water break-down dead Cyanobacteria, the dissolved oxygen may become depleted, which may responsible to kill fish. Also dense algal blooms in the water column blocks sunlight therefore other organisms cannot survive. Wildlife and pets can become more prone by drinking algal bloom water as very small amount of toxin can also cause illness to some of small animals if ingested. From past few decades, unexpected HAB phenomena have been recognized responsible for eutrophication and ballast water introductions, mean while climate is changing continuously. Changing atmospheric CO2 concentrations, with rise in global temperatures, melting of glaciers, changing of rainfall and stratification. Seeing that HABs are a global phenomenon requires international understanding, so need has been expressed for

From last some decade's algal blooms are considered with more importance because of their impact on health and economies around the world [82]. Human modifications of the environmental activities could alter the composition of the phytoplankton community, with varied occurrence and geographic spread of bloom-forming species, also timing of phytoplankton blooms found to changed with increased window each year when blooms can develop [99–102]. Considering example of *Karenia mikimotoi* blooms which are characteristically associated with high rainfall and following low-salinity, high-nutrient run off from land [102]. As temperatures of sea surface in the North Sea have found risen more than the global average over the past 50 years [103]. Practically temperature rise initiates with increase in phytoplankton in the North Sea and North-East Atlantic. Most notably diatoms like *Pseudo-nitzschia* spp. [104, 105]. Increased blooms of *K. mikimotoi* have been seen further in north around the British Isles as compared to past and most potentially linked to changes in duration of stratification [104, 105]. On the other hand, many Dinoflagellates like *Prorocentrum* spp. have decreased in abundance in the North Sea over the last decade, as outcome of increasing temperatures conditions [104–107]. Also shellfish found in Scottish waters have witnessed a decline in the toxins linked with paralytic shellfish poisoning in the last decade [104–107]. These examples show that different species are affected in different ways by changes in environmental conditions. By integrating knowledge of biogeography keen on impact of climate change will be fundamental key for better understanding the effects of change in environment on biodiversity with intention to predict the occurrence and location of an individual bloom event. Now it's time to consider the future directions for HABs and climate change research by bringing together physiologists, ecologists, oceanographers, modelers and climate change specialists to develop consent with priority research for future HABs and climate change effects. In spite how the intensity of HABs changes, the certainty of ecosystems and

their toxins creating serious physiological threat to aquatic.

The increasing incidences of toxic algal blooms have been reported at international level in the past decades. Which are contributed by various causes including eutrophication, climate changes, upwelling of oceans, including unhealthy coral reefs. All information presented here do recapitulate the current state of knowledge about HABs to better understand how change in climate affecting HABs and also coastal communities worldwide. This chapter highlights environmental factors like temperatures, nutrient and turbulence as scorable aspects for HABs. Also, it is essential to note that these type of change also have the potential ability to decrease

#### *Considering Harmful Algal Blooms DOI: http://dx.doi.org/10.5772/intechopen.94771*

*Environmental Issues and Sustainable Development*

respired, promotes hypoxia and acidification [85].

regions, including freshwater environments [78, 79]. Decreased pH shifts the carbonate system to decrease bicarbonate concentrations and increases dissolved CO2, thereby increasing carbon availability for photosynthesis [80]. Now such process downgrades the value of metabolically costly carbon-concentrating-mechanisms so that many species of phytoplankton evolved change that may alter the competitive balance among the species [81]. Climate change is now shifting the occurrence and distribution of marine species of various organisms around the world. Therefore frequency and impact of algal blooms have considerably increased around the world in recent decades [82]. Human modifications of the environment such as port construction, release of contaminated water, enriching nutrient by recreation, tourism, fishery, aquaculture, impacts harmful algal contributions [83]. As the reason HABs are now migrating to new ecosystems, therefore considerable risk to aquatic ecosystems and the humans is also found to increase. There is no doubt that oceans are getting warm because of accumulation of CO2 in the atmosphere through various activities [78]. Elevated CO2 offers the potential to rebalance the distribution of primary producers that rely upon inorganic carbon for performing photosynthesis [84]. Hence co-occurrence of climate change stressors and their physiological impacts have been in continue study from the past decade, excessive level of biomass generated creates high levels of organic matter which, when

Coastal zones are host to a varied type of aquatic life and are known dynamic ecosystems [86]. Such locations found to be impacted by climate change as several coastal regions are getting warm hastily than the open-ocean [87]. It is also important to note that coastal areas are also prone to eutrophication, acting as stressors, as unnecessary nutrient loading promotes HABs [88]. As result of ecological changes spring diatom blooms within temperate latitudes, surface waters speedily warm and stratify, which isolates bottom waters from surface influxes of dissolved oxygen and lowers CO2 water, making the condition promoting concurrent hypoxia and acidification [89]. Various HABs flourish in stratified water columns, in late spring and early-summer time's stressor-sensitive, early-life stages of many aquatic genera/ species are present in coastal systems [90, 91]. Because of migrating of HABs to new ecosystems native species, experience selective pressures and consequently suffer the greatest population declines [92]. Generally Cyanobacterial HABs are associated with fresh to brackish water, even though blooms of *Trichodesmium* sp. and *Lyngbyaa* sp. in saline tropical and subtropical waters are considered as harmful mainly in Asian and South Pacific nations. Were Cyanobacterial HABs in the marine and freshwater bodies gets worsened due to elevated anthropogenic nutrients that can be the consequences of regional and local population density. Evidence shows that Cyanobacterial HABs are enhanced by elevated temperature [93], Likewise, elevated CO2 leads to increased growth rates of Cyanobacteria. But surplus inputs of N and P relative to Si shifts the conception from eukaryotic like diatom to Cyanobacteria creation. Noteworthy finding shows that internal loading of phosphorus together with decreasing N:P ratios able to enhance blooms of nitrogenfixing Cyanobacteria over the other phytoplankton at some area like Baltic Sea.

HABs species too have harmful effects solely on fish other invertebrates. Variety of planktonic algae forms HABs which are associated with killing of fish in nature [94–96]. Example algal blooms of planktonic fish killers haptophyte *Prymnesium parvum,* has caused fish killing blooms worldwide since the first recorded bloom in Danish waters in the 1930s. Some studies show that HABs effects physiology of fish indicating respiratory effect. Evidence shows that on exposure of fish to *P. parvum* reflects toxic effects related to fish gill damage. *P. parvum* exposure may effects fish health as increase in gill permeability found to cause sensitivity to subsequent secondary toxicity, as well as effects of hemolysis and anti-coagulant being

**46**

noted [97, 98]. Even mammals and birds exposed to Cyanobacterial toxins may become ill or sometimes die. Records show that when other bacteria in the water break-down dead Cyanobacteria, the dissolved oxygen may become depleted, which may responsible to kill fish. Also dense algal blooms in the water column blocks sunlight therefore other organisms cannot survive. Wildlife and pets can become more prone by drinking algal bloom water as very small amount of toxin can also cause illness to some of small animals if ingested. From past few decades, unexpected HAB phenomena have been recognized responsible for eutrophication and ballast water introductions, mean while climate is changing continuously. Changing atmospheric CO2 concentrations, with rise in global temperatures, melting of glaciers, changing of rainfall and stratification. Seeing that HABs are a global phenomenon requires international understanding, so need has been expressed for generating Global HAB Status.

From last some decade's algal blooms are considered with more importance because of their impact on health and economies around the world [82]. Human modifications of the environmental activities could alter the composition of the phytoplankton community, with varied occurrence and geographic spread of bloom-forming species, also timing of phytoplankton blooms found to changed with increased window each year when blooms can develop [99–102]. Considering example of *Karenia mikimotoi* blooms which are characteristically associated with high rainfall and following low-salinity, high-nutrient run off from land [102]. As temperatures of sea surface in the North Sea have found risen more than the global average over the past 50 years [103]. Practically temperature rise initiates with increase in phytoplankton in the North Sea and North-East Atlantic. Most notably diatoms like *Pseudo-nitzschia* spp. [104, 105]. Increased blooms of *K. mikimotoi* have been seen further in north around the British Isles as compared to past and most potentially linked to changes in duration of stratification [104, 105]. On the other hand, many Dinoflagellates like *Prorocentrum* spp. have decreased in abundance in the North Sea over the last decade, as outcome of increasing temperatures conditions [104–107]. Also shellfish found in Scottish waters have witnessed a decline in the toxins linked with paralytic shellfish poisoning in the last decade [104–107]. These examples show that different species are affected in different ways by changes in environmental conditions. By integrating knowledge of biogeography keen on impact of climate change will be fundamental key for better understanding the effects of change in environment on biodiversity with intention to predict the occurrence and location of an individual bloom event. Now it's time to consider the future directions for HABs and climate change research by bringing together physiologists, ecologists, oceanographers, modelers and climate change specialists to develop consent with priority research for future HABs and climate change effects. In spite how the intensity of HABs changes, the certainty of ecosystems and their toxins creating serious physiological threat to aquatic.
