Coral Bleaching Dinoflagellates

Coral reefs are found in shallow tropical waters along the shores of islands and continents. Coral bleaching is a topic that gets left in the dust. Not many people really pay attention or show much interest in it. Widespread bleaching, involving major coral reef regions and resulting in mass coral mortality has raised concerns about linkage of the events to global phenomenons including global warming or climate change and increased UV radiation from ozone depletion. Corals provide a lot not just for us humans but for marine life as well. Marine Biology provides information about how bleaching happens and how it affects the coral. Buchheims’ article is full of logos and a few pathos while the other source is full of ethos. In The Nature Conservancy’s director Stephanie Wear provides us with lots of professional opinions

Coral reefs exist all over the world and are generally known as being one of the most diverse, intricate and beautiful of all existing marine habitats. They have many varying structures which are developed by algae and are symbiotic with various reef building corals which are referred to as, zooxanthellae (algae). There are many other factors such as, coralline algae, sponges and other various organisms that are combined with a number of cementation processes which also contribute to reef growth, (CORAL REEFS, 2015).

Coral reefs are the most biodiverse ecosystem on the planet. There are more than 25,000 known species of organisms and countless others that have yet to be identified (Helvarg, 2000). Reefs thrive on the shallow edge of tropical seas, most often on the eastern edge of continents along warm water currents that brush the coasts. Reefs cannot live in cold waters and are limited by ocean depth and available sunlight. Coral is the foundation of the reef community, providing a three-dimensional structure where thousands of species of vertebrates and invertebrates live and feed. Some species of coral are hard, while others soft. Some are branched, yet others are compact and rounded. Coral is made up of large

Consisting of less than 1% of the world oceans, the coral reefs are ancient animals comprising of thin calcium carbonate deposits within the photic layer. Aside from its biologically diverse ecosystems, coral reefs are major source of food for millions and provides habitats and nursery areas for many marine organisms. Coral reefs also act as a physical buffer to protect the coastlines from tropical storms and erosion. In addition, many local communities rely on coral reefs to generate an income through activities such as fishing and diving. However, 75% of the coral reefs are under threat from induced impacts of humans and climate change (Burke, et al., 2011). This essay looks at the human impacts constantly being inflicted on coral reefs.

Coral bleaching usually occurs when the surface of a sea with coral in it becomes too warm for the coral. When the water heats to as little as one degree higher than normal, coral expels the algae living in its tissue, which causes it to turn completely white. The rise in temperature of the sea surface has been linked mainly to global warming. Other causes of coral bleaching include oxygen starvation caused by an increase in zooplankton, increased solar irradiance, increased sedimentation, bacterial infections, changes in salinity, herbicides, low tide and exposure, cyanide fishing and elevated sea levels. Bleaching events in 2016 were unprecedented, nearly 90% of the coral in the Great

Covering over 348,000 square kilometres, the reef is home to the most comprehensive coral ecosystem on the planet and is so large it can actually be observed from space (Australian government). Whilst predominantly being known for its large colourful reefs, is provides a home to a diverse array of marine creatures including 1625 different species of fish, around 600 types

Coral bleaching may seem new and a strange topic, but it has been around and wreaking havoc for many of years. Bleaching starts to happen when the water temperatures rise slightly above average temps for more than several days, which then kills the vibrant coral (“Global Warming”). The coral reefs get their vivid color from algae and other small organisms. They are found in the coral’s tissue. Algae helps supply food for the reef through carbohydrates. The algae creates the carbohydrates through photosynthesis (“Coral Reefs”). Coral bleaching

Coral reefs are threatened by global warming. They can only live in waters between 18 C and 30 C. Therefore, with the increase in temperature of the surrounding water, there has been an unprecedented increase in the number of coral bleaching events during the past 2 decades (which have had some of the warmest years in history). When ocean temperatures get too high, coral polyps lose the symbiotic algae inside them, causing them to turn white, or "bleach," and eventually die.

Covering over 348,000 square kilometres, the reef is home to the most comprehensive coral ecosystem on the planet and is so large it can actually be observed from space (Australian government). Whilst predominantly being known for its large colourful reefs, is provides a home to a diverse array of marine creatures including 1625 different species of fish, around 600 types of hard and soft corals, 100 species of jellyfish, over 3,000 molluscs, 500 species of worms, 215 bird species, thousands of different sponges and crustaceans and more than 30 species of mammals, including the endangered species the dugong.

Elevated sea temperatures are the primary cause of mass coral bleaching events. Bleaching is a stress replication of corals, during which they expel their zooxanthellae during unpropitious conditions, giving elevate to the typical white coloration observed. Aside from temperature, other stressors such as tropical cyclones, freshwater inflows and anthropogenic pollution can additionally induce bleaching but to a far lesser extent and generally not on immensely colossal spatial scales.

Coral bleaching means that corals or coral reefs lose their color because their symbiosis partner start to produce toxic substances with raising water temperatures and therefore the corals get rid of the algae by rejecting them. Without these algae the corals lose, despite their color, the nutrients that they would get from their partners and as the growth and development of the corals is very dependent on that relationship, the corals die due to a nutrition deficit. 3

Even a one degree Celsius can cause the zooxanthellae to leave the corals causing bleaching (Hoegh-Gulderg). Mass amounts of bleaching can result in death of the coral due to lack of food. Over the past 20 years the increase in sea surface temperature has caused chronic bleaching in coral reefs around the world (Brown). The zooxanthellae within the coral polyps go through photosynthesis and produce sugars, lipids, and oxygen (NOAA). The coral can use these products for food and respiration.

Coral bleaching is a phenomenal threat that occurs in response to fluctuating water temperatures, salinity levels, light exposure and disease (Veron, 2009). Embedded within the tissues of coral is a photosynthetic algae known as Zooxanthellae. Both coral and zooxanthellae share an integral symbiotic relationship each allowing each other to function. Zooxanthellae provide the coral with carbohydrates through the process of photosynthesis, allowing the coral to form its calcium carbonate skeleton. In response, the coral provides the zooxanthellae with nutrients needed for its survival. The ‘bleaching’ of the coral is a stress response to the breakdown of the coral-zooxanthellae relationship through the expulsion of the algae from the coral. When

Microalgae plants called zooxanthellae coexist in symbiosis with corals. The algae provide for the corals beautiful colours and other important factors (Nace, 2016). When the algae plant dies, the colours on the corals disappear and when the corals turn white - they are basically considered as dead (Cotes, 1998, p. 26). This is why it’s called coral bleaching! The relationship between corals and zooxanthellae are so critical that if the symbiosis between them gets disturbed - the corals cannot survive without. Further zooxanthellae plants can not survive when the water temperature becomes abnormally warm or contaminated (Nace, 2016). This explains how mass coral bleaching appears. Mass coral bleaching won’t only cause the destruction of corals, but also the habitat for the fish would be long gone. And without the coral reefs incredible colours or the fishes, it’s arguably that GBR won’t appeal to visitors in the same way, and that the reef may end up with an ecosystem that will not longer attract visitors (Newsome et al, 2002, p. 60). This might further lead Queensland to lose a billion dollar tourism industry and in addition a workplace for thousands of people (Armbruster,

Coral reefs contain symbiotic algae called zooxanthellae which gives the coral its healthy brownish color. The algae "utilizes sunlight and the coral animal's respired CO2 to produce energy rich compounds that feed the coral host" (AIMS, 2003). When stress factors such as "heat, solar radiation, pollution, reduced salinity and changes in oxygenation" occur around the coral, bleaching can begin (Dennis). When bleaching occurs, the algae, which create nutrients for the coral to feed from, is released due to stresses to the reef. Thus the coral starves and its white calcium carbonate skeleton of the coral becomes visible (AIMS, 2003). But one of the main stresses that contributes to the lifeless white appearance of the coral is the warmer temperatures of the sea surface water.