I still need help with my coral reef project!!! what does sessile mean?

Question

Corals are sessile animals? what does that mean

how are coral reefs used by humans?

how r they under threat from both natural and human sources??

please help

10 points 4 the best answer at least please answer 1 of the questions please help!!

i know it's boring

Answer 1

From Merriam Websters website

Sessile - permanently attached or established : not free to move about sessile sponges and coral polyps

Answer 2

Sessile means that the organism is permanently rooted to the ground; in the case of corals that means that they are fixed to the seabed.  In other words they are not able to move around, like most plants. That is why the corals have a tendency to build upwards and outwards on the remains of older corals, eventually forming reefs.

How are coral reefs usedby humans? they attract fish, so  fishing would be one use.  Also, tourism.  Sheltered lagoons behind the windward edge of the reefs make good anchorages for boats.

Coral reefs are under threat from "global warming" - rising sea levels and subtle changes in water acidity caused by increased temperatures.  This could eventually kill many of them off.  Pollution is also a factor, especially where it reduces the clarity of the water (say, increased algae due to waste products in the water).  Reef-building corals can only live over a shallow water depth range, where the water is adequately penetrated by sunlight.

Certain natural parasites are also known to affect coral reefs - I think they have been implicated in the die-back of the Great barrier reef.