L5 - Shallow Seas Flashcards
What is the Neritic zone?
In the pelagic zone, above the continental shelf
What is the subtidal zone?
In the benthic zone, the continental shelf below the intertidal (always submerged). Sometimes called the sublittoral zone
What can the continental margins of ocean basins be considered as?
Active or passive
What zone are shallow seas?
Epipelagic zone
What does most of the continental shelf fall within?
Euphotic zone (200m depth)
What is the Euphotic zone like?
It’s a highly productive area, high levels of nutrients, more stable than the intertidal zone.
Why are continental shelves so nutrient rich?
Photosynthesis (the euphotic zone). Lots of dissolved organic matter and dissolved particulate matter. From land sources as well as marine organisms. Nutrient upwelling from the continental slopes. Tides and currents mixing the water.
What are fronts?
Where two discrete water bodies meet. Well-mixed, nutrient-rich coastal water, stratified ocean water.
What are the continental shelf primary production zones?
Benthic + Pelagic
What are the oceanic primary production zones?
Pelagic
How can we classify organisms within benthic communities? Epifauna vs Infauna differences?
Size, location, type of habitat, feeding strategy, lifestyle. Epifauna - live on the sea bed. Infauna - live below the surface (majority)
What is the distribution of benthic organisms like?
Patchy. Planktonic larvae select a particular environment to settle on and undergo metamorphosis. Arrival of new individuals to a population is known as recruitment
Distribution of benthic organisms : examples?
A crab larva, settling based on cues released by its prey species. A barnacle larva, settling based on cues released by adults of the same species
What is the main dictating factor for where benthic organisms live?
The type of substrate (particle size) at the seafloor
What are the soft-bottom sublittoral communities?
Dominate the continental shelves
- ~45% of temperate
- ~30% of tropical
Can be vegetated or unvegetated
Can be important fishery grounds e.g. Nephrops norvegicus (Norway Lobster) burrows in soft, silty ground. E.g. Gadus morhua (Atlantic cod) feeds on many macrofauna
What are the hard-bottom sublittoral communities?
Can experience strong currents. Laminar flow towards the bottom, more complex towards the surface. Sessile benthos may have adaptations to minimise drag. Many autotrophs and passive suspension feeders
What are some methods for surveying benthic communities?
SCUBA
- Allows direct visual
- ‘Longer observations’
- Experimental manipulation in situ
- Time intensive
- Good visibility needed
- Limited in depth to shallow waters
What are some other methods for surveying benthic communities?
Van veen grab, Bottom trawl, Dredge, Box corer, Underwater camera or BRUVS
