Environmental Conditions

Corals have specific environmental conditions that they require in order to survive. These factors limit wherein corals deserve to live. In this unit, we will certainly learn about the abiotic factors that corals have to thrive.

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These environmental problems are referred to as biotic and abiotic factors. Remember, us can failure the indigenous abiotic:

a bioticwithout life

Therefore, abiotic means without life. Abiotic factors are non-living materials of an organism’s environment. Do you psychic what biotic means? It means life. Biotic factors are life or as soon as living contents of a community.

Coral reefs are complex ecosystems. There are numerous different biotic components that influence coral reefs. They will be disputed throughout different units. Because that now, us will emphasis on the abiotic components that impact corals.

Can you think of any type of abiotic components that may influence coral reef ecosystems?

Here room some examples:

Abiotic Factors
Ocean depth
Inorganic nutrient (phosphorus, nitrogen, etc.)
Dissolved gases – oxygen (O2), nitrogen (N2), carbon dioxide (CO2), etc.
Aragonite and calcium carbonate saturation(we will certainly discuss more about this in later units)

Abiotic Factors

Figure 8-1. Abiotic factors

There are multiple abiotic determinants that influence coral reefs (figure 8-1). The number in the diagram exchange mail to the numbered explanation below. Here are the optimal parameters because that corals to live in:

Light: Corals require a moderate lot of sunshine in order come survive. Irradiate is rapidly took in by seawater and also does not pass through to an excellent depths. If there is too small light, then the zooxanthellae will not have the ability to photosynthesize and also produce food because that corals. Too much light, specifically ultraviolet (UV), may reason corals to expel zooxanthellae, causing them come bleach. In later units, we will certainly learn more about coral bleaching.

Salinity deserve to be measure by making use of a hand-held refractometer (figure 8-2). Once using this tool, a little drop the seawater is placed between a measure up prism and a cover plate. Irradiate passes v the sample and also the irradiate is refracted with the prism come the scale. By looking with the eyepiece, the salinity can be read. There are various other tools, such as hydrometers and also conductivity meters, the are also used to measure up salinity.


Figure 8-2. The light (red arrow) bends with a refractometer providing a salinity reading, i beg your pardon is seen v the eyepiece.

Corals require clear water (water through low turbidity) so the the light deserve to penetrate v the water column, permitting the zooxanthellae to photosynthesize. When there is high turbidity, light can’t penetrate through the rely particles. Additionally, corals have the right to be smothered by sediments or particles that settle on top of the corals. Eventually, this might lead to the coral dying.

One way to measure turbidity is to use a Secchi disk. A Secchi disc is frequently an 8 customs (20.3 centimeter) ring disk the has alternative black and white quadrants (figure 8-3).

Secchi disks space lowered right into the water through a rope. Light mirrors off the the peak of the Secchi disk. When the Secchi decaying is no longer able to it is in seen, the human being stops lowering the rope. Then they document the depth the is significant on the rope. Using the Secchi depth, scientists can calculate the turbidity that the water.


Figure 8-3. Secchi decaying pattern.

Nutrients: Corals like low nutrient water. Nutrients encompass phosphorus (P) and also nitrogen (N). As soon as there are lots of nutrients, this may reason algae and phytoplankton come grow. This process can block out the light that zooxanthellae must survive. Also, algae can overgrow coral while contending for space. If the coral cannot acquire light, then it will certainly die.

Figure 8-4. PH scale

Corals favor seawater to have actually a pH level in between 8.0–8.3, i beg your pardon is the typical pH of saltwater. That is very complicated for corals to grow in acidic conditions. We will certainly learn an ext about this topic and how that is related to s acidification in later units.

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On a coral reef, room can it is in very restricted and corals must contend with sponges, macroalgae (seaweed), and even various other coral species. When space becomes limited, many corals can’t choose up and also move. Instead, they fight it out v their neighbors. Part coral polyps execute this by prolonging their mesenteries from your stomachs. Then the battle begins. The mesentery strands cover the intruder species and the coral releases digestive enzyme that start to devour their neighbor. This fight for territory can be watched in the Coral Nighttime Battle. Click on video #5 come view.

Remember the these are basic parameters and that there are corals that have adjusted to different conditions. For example, Siderastrea radians, the lesser starlet coral, has adapted to living in an extremely stressful conditions in Florida bay (Lirman et al. 2002). This huge body that water is an estuarine area whereby seawater mixes with freshwater. The median depth in Florida just is 5 feet (152.4 centimeters), which is among the factors that environmental problems fluctuate greatly. Throughout the dry season, as soon as there is small to no rain and evaporation prices are high, salinity levels can reach hypersaline conditions (greater 보다 40 ppt). It has additionally been documented that details basins in Florida just reach over 70 ppt. This would be a very an overwhelming place to live if you were a coral. Mental that many corals can tolerate 23–42 ppt.

In another example, American Samoa corals have adapted to high temperatures the can easily exceed 89.6°F (32°C) for multiples hours and days at a time (Craig et al. 2001). This provides us hope that part corals will certainly adapt to climate change and warming seas.

There are various other abiotic components that influence coral reefs. We have currently learned exactly how currents can affect distribution the coral reefs in Unit 7: Distribution. Over there are various other abiotic components that we will certainly learn much more about in later units (see Unit 9: Coral Growth). Us will additionally learn about the biotic determinants that affect coral reefs as well (see Unit 16: Food Webs, coming soon).

Next Course



Figure 8-1. Sun. 2014 via Clipart Panda. http://www.clipartpanda.com/clipart_images/sun-clipart-medium-5602503.

Figure 8-1. Thermometer. N.d. Via Teacher’s Files. http://www.teacherfiles.com/clip_art_thermometers.htm.

Figure 8-2. Refractometer adjusted from CEphoto, Uwe Aranas , 29 Oct 2013 via Wikimedia Commons. https://commons.wikimedia.org/wiki/File%3APortable-Refractometer-03.jpg.

Figure 8-3. Through User: Mysid (Own work) , 1 Nov 2005 via Wikimedia Commons. http://upload.wikimedia.org/wikipedia/commons/0/0b/Secchi_disk_pattern.svg.


Craig, P., Birkeland, C., & Belliveau, S. (2001). High temperatures tolerated by a diverse assemblage of shallow-water corals in American Samoa. Coral Reefs 20: 185-189.

Dubinsky, Z. & Falkowski, P. (2011). Light as a source of information and energy in zooxanthellate corals. In: Dubinsky, Z. And also Stambler, N. (eds.) Coral reefs: one ecosystem in transition, Springer, Dordrecht.

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Lirman, D., Orlando, B., Marcia, S., Manzello, D., Kaufman, L., Biber, P., Jones, & Tahzay, J. (2002). Coral areas of Biscayne Bay, Florida and adjacent offshore areas: diversity, abundance, distribution, and also environmental correlates. Aquatic Conservation: Marine and also Freshwater Ecosystems 13(2): 121-135.