describe coral reefs and mangrove swamps and the conditions required for their development

•reef-building corals cannot grow anywhere:

          •although corals are found everywhere, coral reefs are only found in or near the tropics and are controlled by seven limiting factors

          

          •temperature: mean annual temperature has to be over 18 degrees, with an optimum of 24

          •depth: can only grow in water less than 25 metres deep 

          •light: shallow water allows light for tiny photosynthesising algae, providing coral food 

          •salinity: can only live in sea water with not too high salts

          •sediment: sediment clogs up feeding structures and cleaning systems of corals

                    •cloudy water also reduces light penetration required for photosynthesis 

          •wave action: prefer high energy, ensuring freshly oxygenated water

                     •it helps clean out trapped sediment, brings plankton but may be destroyed if too exposed

          •exposure to air: corals die if they are exposed too long to arise they can only survive and grow at low tide level 

          •cleanliness: water needs low pollution as they are sensitive 

•there are three types of coral reefs:

•there is a link between the formation of these three - each is developed version of the last from fringing reef to barrier then atolls

•mangroves are various types of trees and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics

          •roots give stability against tides and surges

          •gaps in between roots to filter out water and to prevent coastal erosion

          •can store salt to limit intake and to limit water loss

          •has adaptations to capitalise on nutrients and adapt to low oxygen 

•mangroves need specific conditions for development to protect from waves, accumulate sediments from rivers, tolerate saline species and for tidals so saline condition are replenished