Coccolithophores have had an effect on global climate change for a few million years. The marine phytoplankton group is responsible for approximately 20% of the total carbon fixation in marine systems. They can form blooms spreading hundreds of thousands of square kilometers, are recognized by elegant coccolith structures formed from calcium carbonate exoskeletons, and are visible from space. Although carbon is transferred to the sediments in organic matter and calcite form by coccolithophores, carbon dioxide (CO2) is released by the calcification process. Therefore, they have a complex effect on the carbon cycle due to their activity regarding CO2 production and consumption. This review represents the first attempt to present temporal and vertical distributions of Emiliania huxleyi (Lohmann) Hay & Mohler, 1967 (Ehux), which is one of the most important species of the coccolithophores in the bloom periods and the interaction of this species with other phytoplankton groups in the Sea of Marmara. This study may also indicate the advance of this species from the Black Sea region through the Sea of Marmara and the Dardanelles under favorable conditions.
- Emiliania huxleyi
- bloom dynamics
- Sea of Marmara
The Sea of Marmara is a very important water passage between the Aegean Sea and the Black Sea via the Dardanelles and the Bosphorus. It has two current systems that run in opposite directions. Deep water high in density (38.0 ppt) coming from the Aegean Sea flows into the Black Sea. Surface water low in density (18.0 ppt) coming from the Black Sea flows into the Aegean Sea. Therefore, Marmara is affected by both neighbor systems [1–3].
Coccolithophores are marine haptophyte phytoplankton. They are one of the most important groups of phytoplankton in today’s oceans and contain about 300 species.
The main phytoplankton groups in the Sea of Marmara are dinoflagellates, diatoms, coccolithophores, and cyanobacteria. Although there are many different phytoplankton species—more than 150 in the Sea of Marmara—the blooms tend to be extremely rich in a single, or only a few, predominant species such as
This study looks at
The methodology adopted by this review study on the bloom dynamics of the coccolithophore
Emiliania huxleyi(Lohmann) Hay & Mohler, 1967
3.1. General characters
3.2. Global distribution and abundance
3.3. Climate change and harmful algal blooms
It is predicted that climate change will seriously impact aquatic ecosystems, both freshwater and marine. Together with nutrient pollution, these climatic impacts might bring about increases in the densities and field effects of harmful algal blooms (HABs). Climate change might affect HABs in many ways as a result of increased water temperature, higher CO2 values, changes in rainfall and salinity, coastal upwelling, rise in sea levels.
As waters warms more than usual due to climate change, HABs will increase both in number and area. HABs usually occur in warm summer periods. Warm waters favor the formation of HABs in a number of ways. For example, nanoplankton and picoplankton species such as the more toxic cyanobacteria and coccolithophores prefer warmer waters. High temperature levels at the surface prevent mixing of the water column, which allows HABs to become thicker and grow faster. It is generally accepted that warm waters favor the proliferation of tiny phytopkankton bloom species and allow them to survive much easier in the surface waters. It is known that algal blooms absorb solar radiation, which makes the water even warmer than usual and facilitates more algal blooms. On the other hand, climate change might lead to more drought seasons, making freshwater saltier. So, marine algal bloom species could spread to freshwater and brackish water ecosystems.
Phytoplankton species need dissolved CO2 to proliferate. Higher CO2 levels—first in the air and then water—might lead to rapid phytoplankton increase, particularly picoplanktonic species that float on the surface layer of the water. Moreover, climate change might affect precipitation dynamics, leading to alternating periods of drought and intense storms. The main source of nutrients is rain and river water discharge into aquatic ecosystems, supporting more algal blooms.
In view of current sea level rise, more scientists predict that sea levels will rise by as much as 1 m by 2100. Rising sea levels would create an increase in shallow and coastal waters—perfect conditions for the growth of phytoplankton and other algae. Another important factor is the increase in coastal upwelling events due to climate change. Coastal upwelling is a transport process from ocean deep-layer waters rich in nutrients to surface-layer waters of coastal zones due to the drifting of surface waters by offshore winds. Waters rich in nutrients delivered by upwelling lead to more algal blooms.
On the other hand, it is important to remember that this is a two-way process in which climate change affects HABs and HABs affect climate change. Looked at from the perspective of global excessive
4. Bloom dynamics of
Emiliania huxleyiin the Sea of Marmara
4.1. Effect of temperature, salinity, and CO2 in the Sea of Marmara
Average annual air temperature anomalies between 1981 and 2014 in Turkey (Fig. 3) confirm increased annual average temperature. For example, looking at temperature changes in the last 5 years the average temperature in 2014 (14.9°C) exceeds the average between 1971 and 2010 (13.5°C) (Figs. 3
The increase in average air temperature also causes an increase in surface water temperature in the Sea of Marmara and Black Sea—as is the case in other Turkish seas (Fig. 5). Due to the similar climatic behavior coupled with the effect of Black Sea surface waters via the Bosphorus, sea surface temperature variations in the Sea of Marmara are largely similar to the time series of basin mean winter anomalies of sea surface temperature (SSTA), surface atmosphere temperature (SATA), and the meridional component of surface wind (WA, m/s, dashed lines) for the Black Sea .
The Sea of Marmara has two current systems that flow in opposite directions: upper-layer water that originates from less salty Black Sea surface water (18.0 ppt) and lower-layer water that originates from very salty Mediterranean water (39.0 ppt). Therefore, there is stratification in terms of both temperature and salinity during the year. However, the stratification in temperature in summer and winter in the Sea of Marmara is reversed, but the stratification in salinity is not. Hence, surface waters are consistently cold in winter (8–12°C) and hot in summer (20–25°C) irrespective of temperature during the year. When it comes to minimum and maximum temperature variations the Sea of Marmara provides the most favorable conditions for massive
In the summer
4.2. Effect of nutrient and nutrient ratios on
Emiliania huxleyiblooms in the Sea of Marmara
There is experimental and natural evidence for the exceptional competitive ability of
However, another examination of mesocosm experiments over several years showed that
Turkoglu [9, 10] demonstrated that N:P ratios are significantly lower than the assimilatory optimal of the Redfield ratio (16:1) in the Sea of Marmara during
On the other hand, vertical profiles of inorganic nutrients in bloom periods show that both nitrogen and phosphate concentrations in the Sea of Marmara are higher (Figs. 10
In actuality, what triggers
Merico et al.  showed low N:P ratios in the southeastern Bering Sea during the
On the other hand, inorganic N:P ratios may not be good indicators of phosphorus stress if organic forms of nitrogen and phosphorus are available to phytoplankton. Organic forms of nitrogen and phosphorus are used by many phytoplankton and may be important in their nutrition, but data on organic nutrient forms, bioavailability, and species-specific abilities to use them are still limited [47, 48].
4.3. Phytoplankton chlorophyll
alevels in the Sea of Marmara
Turkoglu (2008) revealed that, in the summer
SeaWiFS (Sea-Viewing Wide Field-of-View Sensor) satellite images for chlorophyll
Emiliania huxleyibloom characters of the Sea of Marmara
5.1. Interactions of
Emiliania huxleyiand other phytoplankton
Various scientists studying phytoplankton taxonomy have listed over 150 different types of phytoplankton in the Sea of Marmara [1, 52]. However, the blooms tend to be extremely rich in a single, or only a few, predominant species. This sea has a three-phase phytoplankton bloom sequence. Diatoms tend to predominate in March, dinoflagellates in April, and the dramatically colorful blooms of
The Moderate Resolution Imaging Spectroradiometer (SeaWiFS/MODIS) produced true-color images of the extensive bloom events of
The abundance of
MODIS images (Figs. 15
The sea level in these bodies of water is in equilibrium—were it not the surface of these seas would be rising or falling. The flow of water into one is counterbalanced by an approximately equal flow of water out of another. The flow of surface water out of the Black Sea and the Sea of Marmara into the Aegean Sea is approximately 600 km3 y-1. The water flow is balanced by annual freshwater discharge of about 300 km3 from rivers, especially from the Danube River, which discharges into the Black Sea, and by annual saline water input of about 300 km3 coming from the Mediterranean Sea via the Bosphorus. Black Sea surface-layer water is substantially less saline than Mediterranean water due to the freshwater discharge of rivers [28, 56, 57]. Input of less saline water from the Black Sea and the Sea of Marmara, accompanied by the clouds of coccoliths, is very important to the physicochemical oceanography of the Aegean Sea. The movement of the turquoise water, which stays in the surface layer due to its lower density, can be tracked through the Aegean Sea (Figs. 15
During both the
6. Management of HABs and
HABs can be managed in three ways: (1) prevention, (2) mitigation, and (3) control efforts. Prevention involves reducing the incidence and extent of HABs by controlling or decreasing the input of anthropogenic waste water, rich in nutrients and other pollutants, and ballast water, rich in invasive species, before HAB onset. HAB mitigation generally involves monitoring for blooms and their toxins, public communication programs, and the transfer/removal of fish cages from critical areas to less critical regions. HAB control involves a number of methods: biological, chemical, ultrasonic, ozonation, chemical and clay flocculation.
Nature dictates that all organisms are controlled by other organisms. There are many host-specific viruses, predators, parasites, and pathogens involved in the biological control of many HAB species. To date, the control mechanisms on the distribution of
Recently, amplified segments of the major capsid protein (MCP) gene from viruses that infect
The overutilization of nutrients by summer and winter diatom blooms immediately before
Because of their potential impact on global carbon and sulfur cycles ,
However, there is general agreement that—in light of the high levels of nutrients, changing nutrient ratios, chlorophyll