Deep Sea Benthos (exam 3)

geomorphological features of benthic realm

* sea mount
* abyssal plain
* mid ocean ridge
* trenches

sea mount

* underwater mountain doesn’t break water surface
* influence underwater currents
* species rich
* high species endomism

abyssal plain

flat

mid ocean ridge

* sea floor spreading
* production of new oceanic crust

trenches

* deepest portion
* have own ecology due to unique ecosystem

physiochemical factors od benthic realm

* light
* temperature
* dissolved oxygen
* bottom currents
* hydrostatic pressure
* sediment

light in benthic realm

* non existent in aqua photic zone of deep sea
* only bioluminescence

temp of benthic realm

* low and constant/-1-4 C avg. 2
* exceptions: Red Sea & Mediterranean Sea

dissolved oxygen of benthic realm

* relatively constant
* avg 0.5 mg/L below 2000m

bottom currents of benthic realm

* bidirectional tidal currents
* unidirectional thermohaline & Coriolis currents

hydrostatic pressure of benthic realm

* high constant pressure
* compresses gases
* limits depth range for most species/# of species declines with depth

sediment of benthic realm

* mostly soft sediment w/ consistent physiochemical properties
* clay particles/inorganic substances under oligotrophic waters
* two classes of biogenic ooze: siliceous & calcareous
* hard substrate uncommon (sea mounts, vents, slopes, whale skeletons

siliceous ooze

* silicon based
* formed by diatoms and radiolaria

calcareous ooze

* calcium carbonate based
* formed by foraminifera and coccolithophores

food availability in benthic realm

* primary production
* particulate organic matter
* dissolved organic matter
* large food falls

primary production in benthic realm

* rare
* mostly limited to hydrothermal vents and cold seeps

particulate organic matter

* 1-3% of surface POM production reaches sea floor
* marine snow

dissolved organic matter

* can be 10x higher than that of water
* significant portion of some species nutrients
* created mainly by metazoan metabolic processes, bacteria, decay

large food falls

* whole bodies of dead animals/large plants sink
* significant source of nutrients
* provides route for dispersal of deep sea species
* 4 stages

1st stage of food falls

* mobile scavenger stage
* fishes, lithodid crabs, octopus, giant isopods consume soft tissue with mouths

2nd stage of food falls

* enrichment opportunist stage
* aggregations of polychaete worms, cumaceans, snails, crabs, shrimp

3rd stage of food falls

* sulfophilic stage
* 10-50 years
* chemosynthetic bacteria use sulfate to breakdown lipids inside bones
* produce sulfide to support bacteria mats, mussels, tube worms

4th stage of large food falls

* reef stage
* remains provide sites of attachment/settlement for sessile species

wood in benthic realm

* boring bivalves convert it to fecal pellets
* symbiotic bacteria that digest cellulose reside in gills

trends of organisms

number of individual organisms and their total biomass show decline with depth

megafauna & bacteria trend

* clearest decrease in megafauna
* little change in bacteria trends

macrobenthos & meiofauna size size trends

show decrease in size with higher depth

microbes of benthic realm

* major role in carbon and nutrient cycles
* bacteria live in huge numbers
* viruses key drivers of microbial ecosystem
* archaea as abundant as bacteria

deep sea benthic organisms

* macrofauna: polychaetes, bivalve mollusks
* meiofauna: nematodes, copepods
* suspension feeders: rare
* deposit feeders: dominant
* more infauna than epifauna

sessile megafauna

* sea fans: gorgonians
* sea pens: pennatulids
* Porifera: sponges
* Ascidians: sea squirts

deep water corals

* occur worldwide on seamounts, canyons of continental slope, hard substrate
* 800-1300m
* diverse/rich in demersal fishes
* lack zooxanthellae
* Lophelia pertusa dominates

deep water coral mounds

* depths more than 1000m
* common in areas supported by PP from above
* calcareous coral dominate (coral whips/fans common)
* abundant fish species

sedentary megafauna

* mostly unknown bc of difficult sampling
* Echiurans: spoon worms live in burrows
* long proboscis to feed on surface detritus

3 most common groups of mobile megafauna

* echinoderms
* decapod crustaceans
* fish

echinoderms

* brittle stars
* sea cucumbers: from herds, exhibit resource partitioning on types of detritus
* wide spread and abundant

decapod crustaceans

* squat lobsters predominant reptant (on sea floor) decapods
* crabs rare except for red crab
* prawns common: red, natant (swim above sea floor)

fish

* swim just above sea floor
* diverse, elongated body form
* lipid stores instead of swim bladders
* depth limit 8200m

Xenophyophores

* large, single celled protists on deep sea floor

black smoker HTV

* hotter and larger
* release iron monosulfide: has black color, warm water hits cooler water creating smoke effect

white smoker HTV

* cooler & smaller
* further away from active rift
* release barium, calcium, silicon mostly
* support snails, sponges, deep sea corals but not in abundance of black smokers

hydrothermal vents

* in regions of high tectonic activity
* chemosynthesis: allows for primary production at hydrothermal vents

organisms of hydrothermal vents

* tube worms: have trophosome that houses chemosynthetic bacteria to supply carbon to worm
* squat lobsters
* shrimp
* some crabs
* some fish
* bivalve molluscs
* giant clam

two models of gene flow (vent dispersal)

* stepping-stone model: most gene flow btw neighboring vents
* island model: long distance dispersal and mixing of larvae

cold seeps

* occur at fissure/cracks caused by movement of tectonic plates
* hydrogen sulfide, methane seepage occurs in form of a brine pool
* dominated by bivalves w/ symbiotic chemosynthetic bacteria