deep sea Flashcards
deep sea characteristics
- Least understood ecosystem on the planet
- > 200m
- Av depth = 3800m, max depth = 11,000m
- 64% of earth
- Food supplys surface - seasonal
- 90% of ocean
- Largest ecosystem on earth
- 0.0001% explored
- 28 habitats are currently known in deep sea e.g. cold water corals
- Extremely high biodiversity – in 0.25m2 = 100sp
- Est richness 500,000 – 100,000,000
- decrease of abundance and biomass with depth
what did Forbes propose in 1840
Azoic hypothesis - there’s no life below 600m
what kind of habitat is the majority of the deep sea
soft sediment
what supplies the deep sea with food
faecal pellets, floating algae, bodies of dumped fish -> most derived from surface layer
what is Seasonality of repro and abundance in the deep sea tied to
phytoplankton blooms at the surface
2 types of predominantly soft sediment environments
Continental margins
Abyssal plains
continental margin characteristics
(200 - 4,000m – 15% of seafloor) – shelf, slope, rise, abyss
- Impacted by trawling
- Studied minimal
- Heavily impacting areas of the seafloor before we have studied them
- OMZs
abyssal plains characteristics
(3800m - 75% of seafloor)
- <1% explored
- Magonese nodules
- Low energy
- Low accumulation rates
- 1-4 degrees c
- Generally high o2 concs
3 types of predominantly hard sediment environments
Seamounts
Canyons
Coral ecosystems
seamounts characteristics
Volcanic in origin
Isolated – currents
Geographic distance
Canyons characteristics
- Oceanic island + continental margins
- Conduits for transport of organic material into deep ocean
- Significance:
-structurally diverse habs - diversity hotspots
-Larval sources to adjacent cont margins
-Refuge from ocean acidification
4 types of Coral ecosystems
- Shallow tropical coral reefs
- Mesophotic reefs
- Deep sea and cold water coral reefs (no zooxanthellae)
- Deep sea and cold water coral beds / gardens
importance of deep sea coral habitats
- Largest structures or extensive beds created
by living organisms - Great diversity of species
- Habitats
- Fisheries
- Long-lived and slow growing, take 1000s of years to develop
reasons deep sea coral communities are in decline
Humans = greatest threat
* Ocean Acidification – affect deep species first
* Mining
* Trawling - Rockhopper gear
=> even more in danger than shallow reefs
4 types of chemosynthetic habitats
hydrothermal vents
cold seeps
whale falls
sunken woods + org remains
hydrothermal vents characteristics
- Spreading centres
- High biomass (rich food source) but low diversity community (toxic – need to be specifically evolved)
- Ephemeral 10s to 100 yrs
- Fastest growing orgs
cold seeps characteristics
- Subduction zones
- Cont margins – oil and gas reserves
- Stable envs – last for 1000s of yrs
- Slowest growing orgs
whale falls characteristics
- Bones have large lipid amounts
- Last 100 yrs
- Dispersal + evolutionary stepping stones for net/seep fauna
- High diversity
- Impacts of Whaling
sunken wood characteristics
- Most ephemeral
- Least well-developed
- Chemo community
