Chapter 2
Coral Reef Ecosystem
Abstract Coral polyps are the building blocks of coral reefs. Coral reef ecosystem
consists of a high diversity of marine species yet is among the world’s most fragile
and endangered ecosystem. A highly complex mutualistic symbiosis exists between
the coral polyp and the single celled algae (zooxanthellae) Symbiodinium spp, thus
forming the trophic and structural foundation of coral reef ecosystem. Being photosynthetic organisms, zooxanthellae capture sunlight and turn it into energy-rich
compounds, which is transferred to the cells of the polyp. In return, the zooxanthellae
are nourished with nutrients such as nitrogen and phosphates and gets shelter. Corals
get stressed when environmental conditions are altered and this leads to the expulsion
of the symbiotic zooxanthellae. Coral reefs are beneficial as they provide a source
of livelihood for people; stabilize coastlines and provide nursery homes for juvenile
fish and shelter mangroves and wetlands from oceanic waves. Coral reefs degrade
naturally as well as anthropogenically. Corals excrete dimethylsulponiopropionate
(DMSP), which may have a profound impact on the climate system.
Keywords Coral polyps · Zooxanthallae · Mutualistic symbiosis · Oceanic
acidification · DMSP
2.1 Coral Reefs—An Overview
Corals are either hermatypic (reef building) or ahermatypic (non-reef-building).
Hermatypic (scleractinian or stony or hard) corals thrive in shallow water habitats and contain millions of zooxanthellae, and create the primary reef framework.
Ahermatypic corals lack zooxanthellae but secrete complex aragonite exoskeletons,
and usually do not contribute significantly to reef formation.
Coral reefs are ecologically complex ecosystems engineered primarily by stony
corals that support hundreds of thousands of species and valuable structural habitats
(Fisher et al. 2015; Madin et al. 2016; Putnam et al. 2017); are amongst the world’s
most fragile and endangered ecosystems (Howard and Brown 1984; Bielmyer-Fraser
et al. 2018); and yet consist of an enormous cultural, ecological and economic value
(Mollica et al. 2018). Coral reef ecosystems thrive in low nutrient (such as inorganic
phosphate, nitrate, nitrite and ammonia) waters and are extremely productive.
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
S. B. Shah, Heavy Metals in Scleractinian Corals, SpringerBriefs in Earth Sciences,
https://doi.org/10.1007/978-3-030-73613-2_2
27
Coral Reef Ecosystem
Abstract Coral polyps are the building blocks of coral reefs. Coral reef ecosystem
consists of a high diversity of marine species yet is among the world’s most fragile
and endangered ecosystem. A highly complex mutualistic symbiosis exists between
the coral polyp and the single celled algae (zooxanthellae) Symbiodinium spp, thus
forming the trophic and structural foundation of coral reef ecosystem. Being photosynthetic organisms, zooxanthellae capture sunlight and turn it into energy-rich
compounds, which is transferred to the cells of the polyp. In return, the zooxanthellae
are nourished with nutrients such as nitrogen and phosphates and gets shelter. Corals
get stressed when environmental conditions are altered and this leads to the expulsion
of the symbiotic zooxanthellae. Coral reefs are beneficial as they provide a source
of livelihood for people; stabilize coastlines and provide nursery homes for juvenile
fish and shelter mangroves and wetlands from oceanic waves. Coral reefs degrade
naturally as well as anthropogenically. Corals excrete dimethylsulponiopropionate
(DMSP), which may have a profound impact on the climate system.
Keywords Coral polyps · Zooxanthallae · Mutualistic symbiosis · Oceanic
acidification · DMSP
2.1 Coral Reefs—An Overview
Corals are either hermatypic (reef building) or ahermatypic (non-reef-building).
Hermatypic (scleractinian or stony or hard) corals thrive in shallow water habitats and contain millions of zooxanthellae, and create the primary reef framework.
Ahermatypic corals lack zooxanthellae but secrete complex aragonite exoskeletons,
and usually do not contribute significantly to reef formation.
Coral reefs are ecologically complex ecosystems engineered primarily by stony
corals that support hundreds of thousands of species and valuable structural habitats
(Fisher et al. 2015; Madin et al. 2016; Putnam et al. 2017); are amongst the world’s
most fragile and endangered ecosystems (Howard and Brown 1984; Bielmyer-Fraser
et al. 2018); and yet consist of an enormous cultural, ecological and economic value
(Mollica et al. 2018). Coral reef ecosystems thrive in low nutrient (such as inorganic
phosphate, nitrate, nitrite and ammonia) waters and are extremely productive.
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
S. B. Shah, Heavy Metals in Scleractinian Corals, SpringerBriefs in Earth Sciences,
https://doi.org/10.1007/978-3-030-73613-2_2
27