Lec #5 Coral reefs and wetlands Flashcards
What are coral reefs?
These are biogenic structures built by organisms and the most biodiverse and extensive hosts to life on the planet
What other reefs can there be?
Algal reefs, oyster reefs, mussel reefs…..
What heat factors need to be present for a reef to form?
Mean coldest winter 18oC
Mean warmest summer 34oC
What are coral polyps?
Small Coraline organisms that can extract calcium from the water and grown by accretion
what physical forms can polyps be in
straight, round or branching skeletal sturctures
What are the requirements from growth (3, excluding temp and salinity)
Firm sea bed
Lack of sedimentation
Adequate supply of sunlight
What are the salinity requirements for coral and the ideal conditions
27-38 ppt, ideally though is 34 - 36 ppt
What is the average coral growth rate
between 0.4 and 0.7 mm per year, although there are expections
Why would corals stop growing upwards
corals would stop when they reach the sea surface and die due to exposure, although the associated organisms can lead to a solid reef structure above the water
Explain growth on the seaward size
this is subject to wave action which prevents collaging from silt and maintains oxygen and nutrient supply, although wave action may break corals and mean only short round ones grow
Explanation of growth on the sea side
there is a large range of life due to the protection from the sea side of the coral reef, although sediment is washed over the top of the reef
What is the impact of predators on coral growth
these limit the growths of corals, some organims can grow to plauge proportions
What is the impact of humans on coral growth, both local and global (4)
marine pollution
quarrying of corals
nutrient concentrations causing eutoprhication
bleaching due to higher ocean temps (salinty too)
What are the three types of coral reefs
Fringing, barrier and atolls
Explanation of a fringing reef
usually border contient and island shore and are built upwards and outwards from the shore, consist of a reef platform, exposed at low tide,
Just what is a boat channel
Some reefs have large areas begind them which is shallow depression known as the boat channel, it becomes a lagoon at low tide and consists of coraline sands
What are barrier reefs
these are reefs that have indured changes to sea leel rise frm exposure and then regrowth
Why might there be gaps in coral reefs such as the GBR
these may account for prehistoric river outflows, the freshwater would killed the coral reef due to low salinity
What are atols
these reefs are typicall circular surrouding a lagoon
what are the dimesntions of atols
range from 1km to 100km in diameter
average lagoon 30 to 100m deep
What ( and explain) the three types of atols
Oceanic - formed around volcanic deposits, as deep at 550m
Shelf atolls - rise from continental shelf wont be deeper than 500m
Ring atolls - surrounding either earlier or relic atolls
What is involved in the formation of mudflats
Silts mud and clays, dispersed by the ocean will only settle in low energy deposition zones, with out erosion mudflats will aggrade and turn into salt marshes
Where are areas where wave energy is low enough (3)
Along the fringes of estuaries
behind longitudinal bars
embankments or coves
What temporary changes can effect mudflats
during storm conditions and high tidal ranges their presence and size may vary
Key points about the biology of mudflats
home to a range of invertebrates and microorganisms
key part of marine system food web
have a bio film secreted by benthic organisms that help stablise a sediment
Explain the process in simple steps of a mudflat turing into a slat marsh
stable mudflat - aggradation of sediment will raise surface - surface becomes above water at low tide - organisms will become rooted - stablises, other plants build sediment - salt marsh
What do plants do in the creation of mudflats
physical stablisation of mudflats
introduction of organic matter
hydronamics of tidal floods
where are salt marshes found
in the upper part of the intertidal zone
What forms in salt marshes
tidal creeks
What are mangrove
these are shurbs and trees that grow in the upper part ofthe intertidal zone, they are great and diverse on tropical coasts, similar habbit to salt marshes
what is needed from mangrove formation
muddy substrates and low wave enery
What can increase size of mangroves
if there is a small tidal range (macrotidal) they can exsist for ages
