coral reefs

eumetoza

animals with tissues

bilateria

animals with two-sided symmetry and three tissue layers

what are the two major clades of cnidaria

- medusozoa

- anthozoa

medusoza

polyp and medusa

anthozoa

polyp only

what are coral?

- animals

- polyps, tentacles, mouths, and digestive system

- sexual repro: free floating

- asexual: clonal polyp buds off parent

hard corals

calcareous exoskeleton makes them non-mobile

- available to build reefs

soft corals

flexible, non-reef forming, look like trees/plants

shallow water corals

- 0-30m, high light

- best known

- warm water

- much nutrition comes from symbiotic zooxanthellae

mesophotic corals

- 30-150m, low light

- less understood

- retain zooxanthellae, but unclear how much nutrition comes from the algae

deep sea corals

- >150m, many w/o light

- poorly understood, yet extensive

- do not have zooxanthellae

what are shallow water corals

- obligate mutualists

- nutrients derived from algal photosynthesis

- >6000 species, only 1000 hard corals

where are shallow water corals

- tropical

- asia/pacific

- 350,000 km cover (6% total wetland area)

ecological importance of corals

- rainforests of the sea

- protect costal areas

- provisioning

- regulating

- habitat

- cultural

- HUGE value per hectare (highest of all biomes)

coral reefs $$$

- 100,000 to 1,000,000

$/ha/yr

fringing reef

- directly attached to shoreline

- most common, much of GBR

barrier reef

- separated from shore by lagoon or channel

atolls (continuous barrier)

rings of corals in the middle of the sea

platform or patch reef

- grows up from bottom

- often small, but some large ones

- inside barrier = patch

- outside barrier = platform

outer (fore) reef

- most stable (temp, hydro, and DO)

- highest diversity

- strong depth zonation of species

reef crest

- highest point (near surface)

- wave break = high energy

-occasional exposure to air

inner reef (reef flat)

- lowest diversity zone

- largest variation in temp, DO and light

causes of decline: directly human

- reef extraction

- dredging

- overfishing

- sedimentation

- pollution

- ship damage

- recreation

causes of decline: natural and indirect human

- coral disease

- natural disaster

- problems from various organisms

- climate change

- coral bleaching

black band disease

- occurs in weakened corals

- brain corals

- filamentous cyanobacteria coating the corals

- kills corals by suffocation

white band disease

- primarily family of stone corals

- pathogen not yet determined

"natural" storms

- strong storms impact slow growing corals

- these were rare and corals were recovered

- increasing frequency of strong hurricanes likely a problem

crown of thorns

- starfish with 14-21 arms

- fast

- big

- external digestion

- eats up to 13 m each year

- very fertile

- indo-pacific

acidification

- more acidic waters does not kill adult corals

- lower pH impacts, making it harder for corals to form aragonite crystals

coral bleaching

- under stress, polyp expel symbiotic algae

- reversible

- caused by temp stress, acidification, unnatural light, exposure to air

trends of shallow coral decline

- 20% destroyed

- 24% at risk for immediate collapse

- 26% under long-term threat of collapse

- FL Keys: 40% loss

stressed coral dies if

experiences temps 1C above its thermal limit for two months

conservation efforts

1. passive management

- marine protected areas

- marine reserves

- integrated costal management

2. coral restoration

how long have we known about deep corals

> 200 years

deep corals seem to have

- huge accumulation of species

- spawning habitat (groupers)

- widely distributed

where is a large deep coral

- from florida to SC (310m)

- 200 to 1000 meters

- near mouth of amazon river too