Chapter 18 Deep sea Benthos

±Explain why nutrients are in low abundance in the deep sea. How might this explain the reduced abundance of carnivores in the deep sea? Slow decomposition rates?

-nutrients are low in abundance in deep sea because the nutrients come from the scraps from the region above.

-°Much organic matter used up before deep

°Open ocean not as productive as shelf

-less nutrients means less organisms because not enough to sustain.

-Slow decomposition due to reduced abundance of decomposers, slower metabolic rates

±List and describe the different types of habitats in the deep sea.

-Seamounts = Mountains under water

-Deep Water Coral Mounds = Very diverse (1300 species in some cases), but orders of magnitude less than tropical, shallow water coral

-No zooxanthellae, eat drifting particles, plankton

-Provide habitat for other species including fish

-Damaged by deep water trawling

-Development and burial cycle strongly tied to glacial periods

±What is a hydrothermal vent? Where are they found? What is the base of the food web?

±Water heated to 350oC from the ocean's crust

°Ambient temperature ~ 2-4oC

°Maximum temp for thermophilic bacteria ~ 120o

°Animals rarely tolerate > 60oC

±Temperature may vary from 2-350oC in 1 cm near vents

±Chemosynthetic bacteria for the base of a food web.

±Hydrothermal vents constantly being formed and destroyed

±Some known sites are on the map below. Most occur on boundaries between tectonic plates.

-Bacterial Based Food Web

-±Snails, crabs, and limpets graze on bacteria.

±Suspension feeding mussels, barnacles, and feather-duster worms remove food from the water.

±Anemones capture prey with tentacles.

±White crabs and brittle stars are scavengers that eat dead animals and bacteria.

±Explain zonation patterns found at hydrothermal vents. What causes the zonation?

°Highest flows (> 50oC) dominated by alvinellid polychaetes

°Strong vent flow (< 50oC) dominated by Riftia

° Areas without increased temperatures, have suspension feeders without symbionts

±Explain succession on hydrothermal vents.

-The closer to the vent the more stress from H2S

-As you move further from the vents, the more growth

-look at question before

-look at ppt

Explain succession on a whale carcass. What are the major stages? What occurs in each stage?

±_Scavenger_ stage - months to 1 year

-hagfish and other scavengers come and eat

±Opportunist Stage - 2 years. Polychaetes and crustaceans attracted to rich sediments

-animals feed on leftover meat and blubber that has soaked the surrounding sediment

±Sulfophilic Stage - 50 yrs? Chemoautotrophic bacteria and organisms their predators

-anaerobic bacteria produce hydrogen sulfide which other sulfphilic bacteria use for energy

Be able to compare whale falls, cold seeps, and hydrothermal vents

-cold seeps = ±A community similar to hot vents was first found near Flower Gardens at La-Tx border

-°Tube worms and mussels common

±Methane seeps from the seabed

±High levels of endemicity

±Methane oxidation pathway (coupled with sulfate reduction) used by symbiotic and free living bacteria at seeps

°carbon fixed and H2S produced

°Some bacteria may use hydrocarbons

±H2S may also be used by chemosynthetic bacteria

-They ALL have H2S produced

Explain diversity trends with depth. Why is the deep sea benthos so diverse?

-lots of different organisms with different niches

-niche partitioning

±Be able to compare deep sea communities with the RSP and Menge and Sutherland's model.

±Is space limiting?

°Abyssal plane? No.

°Vents, coral mounds, seamounts, methane seeps, whale falls? Yes, but many are also temporary habitats

±Monopolies forming?

°Hydrothermal vents - Riftia dominates

°Monopolies uncommon elsewhere even on coral mounds.

±Disturbances suppressing dominant competitor?

°Less common. Some disturbances eliminate the community

±Predators suppressing dominant competitor?

°Predators may play an important role, but food chains are often shorter

±Tolerance refuge?

°Important in vents, but stress and resources positively correlate in vents

°Other habitats more homogenous.