Tropical Communities Flashcards
what is the global distribution of coral reefs?
tropical
- tropics of cancer and capricorn (broadly)
BUT @ higher latitudes
why reefs not found between the tropics in certain locations?
e.g./hint South America
water currents
deep ocean upwelling - cold water
cold water surface currents
TOO COLD FOR REEF BUILDING CORALS
what are coral reefs composed of?
CaCO3
skeletons of colonial polyps
what are polyps?
anemone-like organisms with a CaCO3 skeleton
what are responsible for most of the CaCO3 secretion in coral reefs?
stony corals
Phylum: Cnidaria
order: Scleractinia
a few mm wide
what does ‘Hermatypic’ mean?
reef-building (corals)
what are hexa-corals?
have 6-sided radial symmetry
what are octa-corals?
have 8-sided radial symmetry
what is an example of hexa-corals?
stony corals
what is the organism with which reef-building corals form a symbiosis?
symbiotic zooxanthellae
Example of a species of coral which undergoes sexual reproduction: spawning
Montastrea cavernosa
what is the typical lifecycle of coral?
- eggs in water
- planula larva
- settles down on seabed (after couple of days) and develops into polyp
what is a common genus of branching coral
acropora
colony growth forms
branching massive foliaceous pillar solitary plate encrusting
main framework coral of reef in Pacfic and Indian Ocean
Family: Poritidae = main mass of reef
HUGE
main framework coral of reef in western Atlantic Ocean (e.g. Caribbean)
Family: Faviidae
what are hydrozoa?
another group of cnidarians (reef-building coral also in.)
which family of hydrozoa are CaCO3 secreting?
millepridae
what are ‘soft’ corals?
no external CaCo3 skeleton
- may have CaCO3 spicules
different species which make up reefs
branching coral plate/encrusting coral fire corals soft corals sponges giant clams fishes invertebrates
types of reef
fringing reef
barrier reef
atolls
patch reefs
what are fringing reefs?
- grow almost up to shore line
- some secrete mucus to survive exposure periods
what are barrier reefs?
futher away from shore
- land between shore and reef has subsided due to tetonic activity leaving gap of deeper water
what are atoll reefs?
circular formations surrounded by very deep water
- old extinct volcano island sinks and collapses into see leaving rim
what are patch reefs?
small structures, found within lagoons
why are coral reefs more productive than tropical rain-forests?
warmer conditions, nutrients recycled wells, good at catching nutrients that goes by
case study of coral reef-algae phase shift
Hurricane Allan - Caribbean
- rainfall reduced water salinity
what is thermal stress?
when temperatures rise 1 degree Celsius above highest temperature expected that year
where are mangroves found?
sub-tropical and tropical (tropics of cancer and capricorn) sheltered shorelines
mangrove tree adaptations
- erenchyma
- don’t tend to have a deep tap root
- buttress roots (prop)
- salt elimination
- propagule and seedlings
what salt elimination adaptations can mangrove trees have?
- secrete salt from underside of leaves
- nectaries - glands which secrete salt
- salt washed from leaves
what are erenchyma?
soft and spongy tissue - allows aeration (O2 to roots)
Mangrove habitat organisms
- mud lobster
- crabs
- molluscs
- termites
- fish
- reptiles
- birds
- mammals
- seagrass
what are the different roles of crabs in mangrove environments?
feed on algae and detritus on mangrove roots
some shred dead leaves - adding to sediment
what propagule and seedling adaptations do mangrove trees have?
continue to develop as travel in water
at point in development when settle bottom become heavy and as tide goes out, digs into sediment
what are the two forms coral can take?
polyp cups or corallites in massive skeleton
which type of zooxanthellae are found in coral-algae symbiosis?
dinoflagellates
where are the symbiotic zooxanthellae found in the coral?
in cells in the gastrodermal layer
what is a conspicuous member of Atlantic coral reefs?
Fire Coral
- strong piercing (painful) nematocysts
what are some key reef echinoderms?
sea urchins and starfish
example of exploitative competition between corals
branching coral grows faster than encrusting or massive coral
- branching coral extends self over encrusting and massive coral, shading them out
example of interference competition between corals
some slow-growing coral species can extend filaments from gastrovascular cavities that, when encounter living tissue from another colony (of a different species), digest the tissue (kill)
what are cryptofauna on coral reefs
sponges/bryozoans/tunicates - small colonial (non-coral/algae) encrusting invertebrates
role of damselfishes in coral reefs
have algae gardens - no coral can survive there
role of encrusting red coralline algae in coral reefs
maintain integrity of coral reef, cement various pieces together with CaCO3
role of green coralline algae in coral reefs
significant contributors to sand
other roles of algae on coral reefs
some bore into coral skeletons - reef break down
create shade
food
what are the four models of fish species diversity and community structure in coral reefs?
competition model
lottery hypothesis
predation-disturbance model
recruitment limitation
what is the coral reef fish species diversity and community structure problem?
not enough diversity in habitats to explain high diversity of reef fish
what are the two factors that the coral reef fish species diversity and community structure models consider?
importance of recruitment processes VS importance of postrecruitment competition
what mangrove grows at water’s edge?
red mangrove
what are mangroves?
salt-tolerant trees and shrubs
a group of different taxa of trees - not an official groups itself
where are mangroves found?
between the mean tidal level and extreme higher water of spring tides
where to mangroves grow?
waterlogged soil
saline environments
muddy sediments
what is the soil of mangroves like?
anaerobic (bacteria)
what are hard bottom mangroves?
live in shallow sediment
- overlies reef/rocky areas
which habitats can magroves be found in?
deltas, estuaries, rivers, sheltered bays, lagoons, lee shores of islands (sheltered locations)
why can’t mangroves tolerate wave action?
would strip away soil from around roots
magroves are a ______ systesm
detritus
seagrasses are…
submerged angiosperms
