Chapter 8

1. Chapter 8 Continental shelves!!!

2. Intro! • Only 8% of global sea surface • Mostly falls in the euphotic zone • Its shallow • Areas that have narrow shelves there is also upwelling which helps the production • The shelves fuel of 90% world’s fisheries • Are affected by human influences

3. Continental shelves! • The shelf goes from the ­­­­­­­­­­­­extreme low-water mark on the shore line about 200 m deep • Its considered neritic • Continues till shelf break (anywhere from 0-1500km offshore ) • Usually has a shallow gradient of 1˚ • Strongly influenced by physical forcing(physical processes like waves) because they are really close to shore • Waves affect ecology of the shallower parts of the shelf • Effects on benthic ecology go to about 80m • Fetch is the uninterrupted distance over which winds exert friction at the sea surface • http://www.youtube.com/watch?v=v0OYJzyxAZc

4. Currents and water… • Currents are increased when a water mass moves through or around land bounded restrictions, or across irregularities in seabed topography • Straights and estuaries typically have typically have the strongest tides • Headlands and bedrock cause tides to be strong around the apex of the headland • Irregularities in seabed cause friction so the current slows down

5. Fronts! • Fronts occur at a point where stratified water and mixed water meet • Results in density gravity dientbetween the two bodies of water • Causes an influx of nutrients • Causes more productivity • Can also happen near estuaries • mixing of waters with different densities. • Causes a frontal system • Can deflect the current away from the shore with aid from the Coriolis affect • Called Regions Of Freshwater Influence (ROFIs)

6. Depth and turbitity • Depth and turbidity are important determining factors of the locations of benthic algae • Areas affected by estuarine plumes are usually very light limited • Caused by suspended sediment and photodetritus • These places are mostly lived in by animals • Coastal areas that are open to the ocean are much clearer • Algae can be found almost everywhere there • Clear zonation from the shallow water to the deeper • Green (shallow), brown, red (deep) • In these situations algae are dominant in biomass • Width of algae dominance depends on water clarity and slope of sea bed

7. Animals and stuff • Processes vary with morphology of the seabed and coast • Body size affects both production processes and how much a specific life form is associated with a specific place • Size of animals living on seabed is constrained by ability to burrow and respire • Size of attached animals are limited by physical processes • Sheer due to current speed • Mobility of organism varies • Highly mobile fish and • Anemones that can move a few mm a day • Others cemented to the rock • Mobility affects the ability to respond to environmental change • Places a limit on how much they can use the enviroment

8. More animals… • Grouping are based on body size • Macrofauna • Anything larger than meiofauna • Most research has been done on them • Easiest to study • Meiofauna • Organisms that would pass through a sieve with a mesh diameter of .5mm but would be restrained by mesh of .063 mm • Least studied but most diverse • Rates of production is much higher than larger macrofauna • Make very indication of environmental stress • http://www.youtube.com/watch?v=x_xyQFGId3g

9. Yaaay.. Yet more animals Microbiota • Contribution is often underrepresented • In tropics can be much greater than the others combined • Body size and longevity are factors that affect recovery time • Smaller organisms take less time to recover • Organisms are also categorized by relative position on seabed • http://www.youtube.com/watch?v=t8nodTdbRqc

10. Things that live in sand… Epibiotaorganism • Emergent organisms that are anchored in or on substratum or free living organisms that move on surface of substratum • Algae are almost exclusively epibenthicGrowattached to substratum • Sometimes calcareous algae form their own habitats Infaunal organisms • Live buried within substratum • Entirely • Partialy

11. Movement! • Sessile organisms show seasonal patterns of growth at high latitudes • Mobile organisms show varying level of inshore/ offshore movement due to temperature • Many crabs and lobsters move inshore during spring and summer to find mates • Then move back during winter to avoid storms • Distribution of bottom dwelling fish in regional seas are linked to certain habitat types

12. Yay fish and movement • At mid-high latitudes fish are associated with a range of habitats • Variation can be attributed to different behavioral characteristics at different life stages • Juveniles are vary picky of sediment grain sizes • Needs more protection • Limits places it can live • Adults are less picky • They can live more places

13. Feeding • Nearly all predators will also eat carrion • Even herbivorous sea urchins and suspension feeders will eat carrion • They are known as facultative scavengers. (Will eat carrion if there is nothing else). • Obligate scavengers are debated to exist. (Only eats carrion) • Candidates would have to be <6 mm • There have been lots of possible species but no conclusive evidence.

14. Food… again • Maintain diversity within algal-dominated community. • Herbivory in fish is more common toward lower Lat. In higher lat. Herbivores are mostly invertebrates. • In systems where a specific species is the predominant grazer they can have a key-stone role or eco-engineering role because they eat certain algae. • Grazers also include carnivores • Evolutionary arms race:race for one species to evolve into something that the predator can’t eat vs. the predator trying to evolve to beat those defenses

15. Feeding.. Yet again • Filter Feeders: extract phytoplankton from water column and suspended mater from just above the seabed (suspension feeding) • Individual animal (about 1g dry weight) filters about 57 liters of water a day • Have an important role in Bento-pelagic coupling • Waste is rich in organic material that is processed by microbial community which feeds the suspension feeders and bulk sediment processers

16. More things • Organisms can have both a stabilizing and destabilizing role in communities. • Cumulative effect of all sediment disturbances known as bioterbation. • They left what’s called trace fosilsin rocks • They enhance the passage of oxygen rich water deeper than into the sediment than it usually would go. • Increases sediment porosity • Burrows made by high density organisms can expose 1.4 m2 • Sediment conveyors- transfer nutrients deeper into the sediment • http://www.youtube.com/watch?v=9SK5amoShPE

17. Cascades and stuff • The flexibility in feeding patterns leads to compications • if you remove species from system, the system isn’t likely to cause significant cascade effects at either end. • Resilience can weaken when human interference and environmental change happen simultaneously. • Simple systems like this are expected in high diverse systems that are characterized by specilized feeding interactions • Interactions in cascades are between organisms from major trophic levels ithin systems(Predator-Herbivore-Primary producer) • Key predators or herbivores in trophic cascades are usually the dominent organisms in their trophic level

18. Organisms • Often can be ecosystem-engineering biota. • They are organisms that due to their abundance or feeding or other activities, exert a strong influence on the structure of the ecosystem • When the link between one trophic level is strong that means that when there is a significant decrease in the pop of a predator/herbivore, there are few others to take their place • Habitat is composed of : • Non biologic material • Biogenic material • Things that came from living things (broken shells) • biota(living things) • Prevailing water-column conditions above • Normally depends on interaction between seabed hardness and stability • Sediments dominate the seabed habitat of the continental shelf • Very according to: • Tectonic history • quantity and quality of the inputs from rivers • transport by currents and waves

19. Surfaces • Hard substrata is rather rare • Strata categorized as: • hard (bedrock to cobble • Soft (gravel to mud) • Biogenic habitats • Bedrock is most stable • Provides an archer for sessile life forms • Occupied by crusting things • Really important for algae • Creates the ability for kelp forrests • Rocks with lots of relief, such as rock reefs also create microhabitats • http://www.youtube.com/watch?v=GcbU4bfkDA4

20. Fooooood • Dominated by particle feeders • The crevices permit the exchange well oxygenated water • provide a hiding place from predators • Many species of fish use these places for refuge when they are growing up • Fishery’s have tried to increase the available habitats by creating artifical reefs • The size of substrata is mostly determined by physical processes and are subject to frequent disterbances • When the physical processes weaken and there are less physical forces • There are more biological and chemical sediments • Stability of sedimentary habitats depends on interaction of physical, chemical and biological processes • http://www.youtube.com/watch?v=XiSU0n0EFoE

21. Size of things in the ocean • The size of substrata is mostly determined by physical processes and are subject to frequent disterbance • When the physical processes weaken and there are more fine sediments • There are more biological and chemical sediments • Stability of sedimentary habitats depends on interaction of physical , chemical and biological processes • Typically described by their partical size • We can only get partial info from this technique • Doesn’t tell us about how the different types of sediment pack together • We can’t tell the porosity or anything that we can learn from knowing the porosity

22. Sediments… yaay.. • Near-shore sediments less than 30m deep are often moved by wave actions • Almost no sessile life forms • Highly mobile organisms most common • In deeper water (more than 50m deep) or in shallow sheltered areas: • Finer sediments settle out due to redused physical forcing • Lots of burrowing amimals that shape seafloor • Mostly crustaceans and shrimp live here • Many semi-enclosed seas and fjordic areas have mud communities • Weak currents • Sheltered • Heavy stratification durring summer

23. Reefs…. kinda…. • Can be made entirely by reef building organisms • Formed by bivalves, corals (hermatypic vs. ahermatypic) and sponges • Can be made by accumulations of things , inorganic or organic material