marine ecosystems of the world (marine lecture 1) Flashcards
1
Q
Ocean statistics
How much of the earth?
Average depth?
Max depth?
How much of earth’s habitable volume?
A
- 71% earth’s surface area: 81% southern hemisphere, 61% northern hemisphere
- average depth = 3794km (4+x continental average)
- max depth 11,022m (mt. everest = 8848m)
- 99+% earth’s habitable volume
2
Q
Phytoplankton
- where?
- how much oxygen produced?
- how do they overcome coastal dependence
A
- ubiquitous across ocean, but not homogenous
- 50% oxygen in the atmosphere
- not coastal dependent bc single celled (small) and float
3
Q
Marine phytoplankton characteristics
- 4 major classes?
- how big?
- reproduction time?
- abundance
A
- cyanobacteria, diatoms, haptophytes, dinoflagellates
- all small, 0.5-300 microns in diameter
- all reproduce quickly, usually under 24h at 20oC
- incredibly abundant
4
Q
Problems for phytoplankton
- phytoplankton sinking
A
- phytoplankton tend to sink
- bigger cells sink faster
- too deep = too dark to photosynthesise & live
- why all ocean ‘plants’ tend to be small
5
Q
Problems for phytoplankton
- nutrient sinking / two layered ocean
A
- nutrients also sink
- light restricted to surface waters
- light at top, nutrients at bottom
- two layered ocean
6
Q
Overcoming two layered ocean problem
- physics
A
- mixing of surface waters by wind
- coriolis effects from earth rotation
- surface currents driven by ocean-atmosphere interactions
- localised upwelling of nutrient rich deep waters driven by above
7
Q
What is thermohaline circulation?
A
- cold water sinks near poles moves equatorward through deep ocean
- tropical water lifted/mixed/welled towards surface
- heated at surface, moves towards poles
8
Q
Overcoming two layered ocean problem
- biology: migration, phenology
A
Migration:
- seasonal
- diel-vertical
Phenology:
- plankton blooms
9
Q
What are diel vertical migrations?
A
- daily migration up/down water column
- avoid visually cued predators in day by swimming deeper
- swim up at night to graze on organic matter/feed on grazers
10
Q
Outcome of physical processes
A
- highly structured ocean
- life evolved to exploit this
- marine ecosystems, distinct & distinctive
11
Q
How are the seas divided up?
A
- ocean basins: horizontally, by geography
- depth zones: vertically, by depth
- ecosystems, biomes, ecoregions: biogeographically by species composition
- biologically, by productivity
- EEZs, management units, fishing areas: politically
12
Q
What are the
- ocean basins
- major seas
A
Ocean basins
- Pacific
- Atlantic
- Indian
- Southern
- Arctic
Major seas:
- North
- Baltic
- Mediterranean
- Caribbean
- Red
- South China
13
Q
What are the features of ocean floors?
A
- continental shelf
- slope
- rise
- seamount
- guyot (seamounts grow above surface, eroded by waves so top flattens, sea floor sinks and they become underwater flat-top structures)
- islands
- mid ocean ridge
- abyssal plain (deepest other than trenches)
- deep sea trenches
14
Q
What are the major depth zones?
A
epipelagic/euphotic zone:
- 50 to 100m, up to 200m
- light enough for photosynthesis
mesopelagic/dysphotic:
- up to ~1000m
- not enough light for photosynthesis
- enough light for animals to see
bathypelagic/aphotic:
- ~1000-6000m
- no light
- 3/4 marine world
hadal zone:
- < 6000m deep
- below abyssal plain
15
Q
What are the major classes of marine life?
A
Benthic:
- on (epifauna) or in (infauna) sea bed
- many benthic creatures have planktonic larvae
Demersal:
- associated with sea bed
Pelagic:
- in water column
- plankton = passive drifters
- nekton = active swimmers
16
Q
How is ocean productivity measured?
A
- NASA’s MODIS instrument
- measures Chlorophyll a across planet everyday
- done via ocean colour
- plus in situ measurements
17
Q
What are the biomes of Longhurst’s Biogeographical Provinces?
A
- oceans divided into four pelagic biomes: polar, westerlies (temperate), trade-winds (tropical), coastal boundary zone
- each found in every major ocean basic
- each ocean basin then divided into 52 biogeographical provinces
18
Q
What are the characteristics of Longhurst’s Westerlies (temperate) biome?
A
- mixed layer depth forced primarily by local winds + irradiance
- strong seasonality at high latitudes
- spring peak production limited by nutrient availability
- complex herbivore ecology & migratory predatory fish
19
Q
What are the characteristics of Longhurst’s Polar biome?
A
- mixed layer depth constrained by surface brackish layer formed in marginal ice zones in spring
- peak phytoplankton production relates to polar irradiance, at peak midsummer
- low taxonomic diversity at all trophic levels
20
Q
What are the characteristics of Longhurst’s Trade-Winds (tropical) biome?
A
- mixed layer depth = ocean-basin scaled adjustment to wind forcing
- small amplitude responses to weak trade-winds seasonality
- high amplitude responses to monsson reversal of trade-winds sometimes (e.g. in Indian Ocean)
- most taxonomically diverse pelagic systemm
- pronounced diel-vertical migrations, fish, squid, zooplankton
21
Q
What are the characteristics of Longhurst’s Coastal Boundary Zone biome?
A
- mixed layer depth + nutrient input controlled by diverse coastal processes (tides, river outputs etc)
- all non-polar coastal shelves more similar to each other than oceanic biomes
- intermittent production at upwellings and coastal divergences
- much benthic-pelagic coupling through trophic interactions and meroplanktonic larvae
22
Q
What are Longhurst’s provinces?
A
- defined by physical structure
- range of oceanographic measurements: mixed layer depth, photic depth, surface nutrient concentrations etc
- measurements, statistical tests & biogeographic observations i.e. species distributions
23
Q
What are the Marine Ecoregions of the World (MEOW)?
- purpose, focus, basis
A
- aim to ensure representative protected area systems
- concerned with coastal & shelf areas only, up to 200m deep
- benthic & shelf pelagic (neritic) biotas
- strong biogeographic basis: taxonomic configurations, evolutionary history, patterns of dispersal & isolation
- hierarchical structure: realms and provinces
24
Q
What are the Marine Ecoregions of the World (MEOW)?
- realms
A
- 12 v large regions, internally consistent biotas at higher taxonomic levels bc shared evolutionary history
- high levels of endemism, down to genera and family levels
- driven by water temperature, depth, isolation
25
Q
What are the Marine Ecoregions of the World (MEOW)?
- provinces
A
- 62 large areas
- distrinctive biotas w some cohesion over evolutionary time
- some endemism, especially among species
- mainly driven by distinctive abiotic boundary features: geomorphological, hydrographic, geochemical
26
Q
What are the Marine Ecoregions of the World (MEOW)?
- ecoregions
A
- 232 areas
- relatively homogenous species composition, distinct from adjacent systems
- species composition driven by: habitat types, oceanographic/topographic features
- biogeography driven by: upwellings, isolation, nutrient inputs, temperature, ice, currents, coastal/bathymetric complexity
- ecologically cohesive, endemism not key determinant
27
Q
Political and Management Units
- Large Marine Ecosystems
A
- for transboundary management issues
- expert derived, no core definition,
- 64 regions (200,000km2+)
- distinct in: bathymetry, hydrography, productivity, trophically dependent populations
28
Q
Political and Management Units
- FAO fishing areas
A
- divised by food & agriculture organisation for: collecting fisheries statistics, fisheries management and jurisdiction
29
Q
Political and Management Units
- Exclusive Economic Areas
A
- UN convention on Law of the Sea
- special rights to sovereign nations over areas of sea
- rights to resource exploitation: fishing, minerals, wind/wave power
- up to 200 nautical miles from coast
