Lecture 3 Flashcards
What does Benthic mean
Epifauna (on) or infauna (in) the sea bed - provide structural complexity
What does Demersal mean
Associated with the sea bed
What does Pelagic mean?
In the water column, includes plankton (passive drifters) and nekton (active swimmers)
What links the pelagic and benthic realms
Benthic organisms have planktonic larvae
Where is most productivity found
In the open ocean in the form of phytoplankton
What are phytoplankton
Single cells floating in the sea
They produce about half the oxygen in the atmosphere
Explain the two layered ocean
Light at the top, nutrients at the bottom - If the ocean was truly homogenous life would not persist
How to overcome the two layered ocean dilemma
Mixing of surface waters by wind
Coriolis effects caused by the earths rotation
Surface currents driven by ocean-atmosphere interactions
Localised upwelling of nutrient-rich deep waters driven by the above
How can the ocean be divided up horizontally
Ocean basins Pacific Atlantic Indian Arctic Southern
How can we divide up the seas
Horizontally by geography - ocean basins
Vertically by depth - depth zones
Biologically by productivity
Biogeographically by species composition - ecosystems, biomes, eco regions
Politically - EEZs, management units, territorial purposes, fishing areas
Name the major seas
North Baltic Mediterranean Caribbean Red South China
Describe the continental shelf
Surrounds all continents Up to 200m Shelf slopes down to abyssal plain - underwater mountains, featureless Ocean ridges Trenches down to 11,000m
What is the epipelagic/euphotic zone
Up to 200m - light enough for photosynthesis
What is the mesopelagic / dysphotic zone
Up to 1000m - enough light for animals to see - not for plants
What is the bathypelagic / aphotic zone
Up to 6000m - no light - 3/4 of marine world
What is the hadal zone
More than 6000m - deep ocean trenches
What is longhursts bio geographical provinces
Oceans divided into 4 pelagic biomes based on forces regulating the distribution of phytoplankton
What are the 4 pelagic biomes based on forces regulating the distribution of phytoplankton
- Polar biome
- Westerlies Biome (temperate)
- Trade-winds Biome (tropical)
- Coastal boundary Zone biome
(Each biome occurs in every major ocean basin)
Describe the polar biome
Mixed layer depth - driven by wind and currents - mixing brings nutrients up to the surface
Mixed layer constrained by surface brackish layer that forms each spring in the marginal ice zone
Allows phytoplankton to photosynthesise and powers marine food webs - mediated by polar irradiance
Low taxonomic diversity at all trophic levels
Describe the westerlies biome
Mixed layer depth forces largely by local winds and local irradiance
Strong seasonality at higher latitudes
Spring production limited by nutrient availability- rely on storms to bring nutrients to the surface
Complex herbivore ecology, migratory pelagic fish driving herbivore community
Describe the trades biome
Mixed layer depth forced by ocean basin scale adjustment to wind forcing - more stable
Large amplitude responses to monsoon reversal of trade winds
Pronounced diel vertical migrations of zooplankton, fish and squids
Most taxonomically diverse pelagic ecosystem
Describe the Coastal biome
Diverse coastal processes (tides, river outpits) modify mixed layer depth and nutrient inputs
Production intermittent at coastal divergences and upwelling
Water shallower - benthic-pelagic coupling
-> through trophic relations and merplanktonic larvae (pelagic larvae of benthic animals)
What are the pros of longhurst
Concentrates on planktonic ecosystem and the physical oceanographic processes driving it
Useful for large-scale ecological studies
What are the cons of longhurst
Doesn’t cover significant marine ecosystems ecosystems (coastal regions) or taxa (fish) of particular interest to people
Marine eco regions of the world (MEOWS)
Strong bio geographic basis Taxonomic configurations Evolutionary history Patterns of dispersal and isolation Hierarchical structure Combination of data-driven and expert opinion
Realms
12 very large regions with internally consistent biotas at higher taxonomic levels we a result of unique shared evolutionary history
High levels of endemism, including genetic and family level
Driven by water temp, isolation and depth
Provinces
62 large areas defined by distinct biotas that have some cohesion over evolutionary time
Some level of endemism , particularly among species
Driven mainly by distinct abiotic boundary features
Similar to longhurst provinces
Ecoregions
232 areas of relatively homogeneous species composition - distinct adjacent systems
Species composition driven by habitat types, oceanographic or topographic features
Biogeography driven by isolation, upwelling, nutrient inputs, temp, ice currents, bathymetric or coastal complexity
Ecologically cohesive, endemism not a key determinate of ecoregion identification
Meow pros
Designed to be pragmatic and relevant to management and conservation
Do their job well for coastal and shelf ecosystems
Meow cons
Only consider a minority of marine taxa
Most of the worlds oceans are not covered by this scheme
What is the aim of data driven marine biogeography
To integrate data across all marine species and environments to map specifies endemicity
What data is used
Occurrence records if 65,000 marine species used to provide an objective, empirical, reproducible basis for biogeographic realms
Similarities and differences in species composition between grid cells used to propose a new map of marine biogeography that covers all oceans from coastal to the deep sea
30 coherent biogeographic realms determined
Describe endemicity in biogeographic realms
The 30 biogeographic realms had a minimum of 17% and an average of 42% endemicity
endemicity was 4 times higher for proposed biogeographic realms compared to the “seas and oceans” indicating that the realms were the better representation of endemicity
This is above the threshold of 10% endemicity proposed for a geographic area to qualify as a biogeographic region
Species-rich benthic taxa such as Arthropoda and molluscs contributed most to endemicity
What are the comparisons with MEOWs
- The biogeographic realms were a close match to 9 of the 11 MEOW realms
- This provides empirical support for marine biogeographic realms proposed based on reviews that synthesised taxon-specific and regional knowledge
- But this extended into deep sea and open ocean systems
- Results suggest that one global classification may be realistic with a close spatial relationship between the pelagic and deep sea realms
- This also complements that Holt et al terrestrial realms with a similar proportion of terrestrial (12 in 29% of the worlds area) to marine (28 in 71%) realms per unit area
