Chapter 8: Continental Shelf Seabeds Flashcards
what percentage of the global sea habitats are the continental shelf seabeds?
8%
What are some defining characteristics of the continental shelf seabeds?
- mostly euphotic
- mineral and organic inputs from rivers
- strong mixing
- upwelling
- most productive marine biome
- fuels strong secondary production
what percentage of the word’s fisheries are taken from the continental seabed?
90%
what changes are being caused to the continental shelf seabed from overusage?
- overfishing
- eutrophication
- mineral extraction
- waste dumping
- oil spills
what are some physical forcing processes in which the CSS are influenced?
- glaciation events
- currents
- waves
- the formations of fronts
- water turbidity
how has wave action influenced secondary production?
by limiting the body size of organisms that can survive in a highly energetic environment
what influence does current flow have on organisms?
- the active/passive transport of organisms, gametes, and food supply rate
- causes physical limitations on organism types that can survive
when are currents increased?
when water moves through, or around, land-bounded restrictions or across irregularities in the seabed topography
describe the differences btwn east and west coast shelves
West: narrow shelf steep slope inward prevailing winds East: broader shelf gradual slope outward prevailing winds
what areas are algae restricted to?
narrow zones of near-shore shallow waters in regions where major riverine discharge and near-bed tidal resuspension of sediments increase the turbidity of the water column.
what are some constraints attached to a biota’s body size in regard to habitat?
- burrowing restricted by respiration and burrowing ability
- attached biota restricted by physical processes, like current velocity
what are some typical characteristics of biota that live in high levels of shear stress?
- highly flexible or encrusting
- shelter seeking
explain frontal systems
- full salinity water approaches the coastline
- interacts with lower salinity water discharged as an estuarine plume
- difference in density btwn the 2 bodies of water sets up a frontal system
depth and turbidity: why does it matter?
- important determinants of the distribution of benthic algae in the shallow waters
- estuarine plumes usually severely light-limited
- turbid areas may be dominated by animals, and algae restricted to shallowest waters.
the seven continental shelf ecosystems are categorized according to what?
physical processes and biology
what are the 7 continental shelf ecosystems?
1-polar: perm ice cover
2-polar: partial/complete ice disp
3-mid-latitude: spring/autumn blooms
4-topo forced Summer production
5-inermittent production at coastal divergence
6- small response to Trade Wind seasonality; coastal river discharges
7-small response to trade wind seasonality; insignificant river discharge
Region 1
Polar; permanent ice cover
- light limited
- low phyto- and zooplankton product.
- many benthic invertebrates, low fish and squid pop diversity
Region 2
Polar; partial or complete ice dispersion
- shallow halocline
- light limited
- productivity increase with ice-melt, then declines
- productivity>consumption, supporting rich and diverse macrobenthos
- low fish diversity
Region 3
Mid-Latitude; spring/autumn blooms.
- winter and autumn mixing
- spring water column stability, productivity pulse
- summer stratification, low productivity
- wind induced coastal convergence and divergence
- abundant, diverse autotrophic production passing through macrobenthos
Region 4
Topography-forced summer production
-similar to region 3, but phytoplankton peak mid-summer, not spring.
Region 5
Intermittent Production at coastal divergence
- trade winds (strong Ekman drift, causing upwelling. Lot of 1* produc)
- high biomass, little diversity
- abundant benthic consumers
Region 6
Small response to Trade wind seasonality, coastal river discharges
- weak seasonality in depth of mixed layer
- strong seasonality of riverine discharges into low salinity surface layer (rainy/dry seasons)
- resuspension of inshore organic rich sediment by monsoon waves
- small sized autotrophs and consumers
- diverse fish fauna
Region 7
Small response to Trade wind seasonality, insignificant river discharge
- dry coast
- weak seasonality in depth of mixed layer
- photic depth is deeper than nutrient cline
- benthic primary production
- high water clarity
- diverse coral reef formation and fish fauna
- high density of filter-feeding crabs
- complex trophic link between fish and benthic invertebrates
what are the sea bed position of biota?
- epibiota
- epibenthic
- infaunal
- microbial communities
what are the types of life modes and mobility of biota?
- sessile biota
- mobie epifauna
- habitat affinity
representative species are categorized by what two main things?
What they consume:
-predators, scavengers, herbivores, filter feeders, suspension feeders
What they do:
-bioturbators, eco-engineers
what is the importance of filter feeders?
bentho-pelagic coupling: process phytoplankton an suspended OM into faeces and pseudofaeces which are deposited on the seabed. This is rich in OM, which can be taken up by the microbial community
what do suspension feeders feed on?
processed OM as a result of faces and pseudofaces of filter feeders.
what are bioturbators, and what is their important role?
- re-work sois and sediments
- works soils up to 2m deep, aerating
- increase the surface area available for oxygen and nutrient exchange that encourages enhanced microbial activity on and in the burrow walls.
ecosystem-engineering biota
if a significant decrease in a population occurs, the E-E biota take their place, which means that the linkage btwn one trophic level and another is strong.
why is it important to not limit research to one particular species on the continental seabed shelf?
you may miss more relevant patterns at higher levels of organization within communities.
what are biotopes and what are their significance?
characterized biological communities of indicator species and habiats
- useful for conservation agencies for classification
- infinite characterization!
what type of specific habitats are there in the continental seabed shelf?
- dominated by sediments
- hard habitat relatively rare
- soft habitats depend on processes
hard habitats:
- relatively rare in the continental shelf seabed
- exist in a range of low to high environmental stress
- occupied y encrusting sessile biota
soft habitats:
what does the stability of these habitats depend on?
physical, biological an chemical processes
what are biogenic reefs?
structures created by aggregations of organisms which form a discrete community
-contribute to large amounts of seabed habitat
