16 From the Continental Shelf to the Deep Sea

16 From the Continental Shelf
to the Deep Sea
Notes for Marine Biology:
Function, Biodiversity, Ecology
By Jeffrey S. Levinton
SAMPLING AND OBSERVING THE SEA BED
Anchor dredge: digs to a specified depth
Peterson
Grab
Box
Corer
Alvin from WHOI
Video camera
Grabbing
arm
The Ventana, MBARI
Remote Operated Vehicle - ROV
The Shelf-Deep Sea Gradient
•  Supply of nutrient-rich particulates to
open ocean deep sea is low:
Distance from shore
Depth and time of travel of material from
surface to bottom(decomposition)
Low primary production over remote deep sea
bottoms
BOTTOM LINE: Input to open ocean bottom
is low. Exceptions: trenches, near continents
Global particulate C – SEAWIFS
satellite image
Depth, distance from continental margin, low productivity in open sea
Input of organic matter
•  Input of organic matter from water
column declines with depth and distance
from shore: continental shelf sediment
organic matter = 2-5%, open ocean
sediment organic matter = 0.5 - 1.5%,
open ocean abyssal bottoms beneath gyre
centers < 0.25%
Microbial Activity on Seabed
•  Sinking of the Alvin and lunch.
•  Mechanism - not so clear. High pressure
effect on decomposition (depth over
1000m) or perhaps low rates of microbial
activity in deep sea.
Microbial Activity on Seabed 2
•  Deep-sea bottom oxygen consumption 100-fold
less than at shelf depths
•  Bacterial substrates such as agar labeled with
radioactive carbon are taken up by bacteria at
a rate of 2 percent of uptake rate on shelf
bottoms
•  Animal activity is more complex. Deep sea
benthic biomass is very low, some benthic fishes
are poor in muscle mass - others are efficient
predators and attack bait presented
experimentally in bait buckets. Also some
special environments with high nutrients (more
later)
Deep-Sea Bacteria
•  Known to be barophilic
•  Have reduced respiration rates and reduced
conversions of substrates in heterotrophy
•  Genetically different from shallow water
strains
Global particulate C – SEAWIFS
satellite image
Depth, distance from continental margin, low productivity in open sea
IS THE DEEP SEA IN SLO-MO?
Low input
Low microbial activity
Low biomass
Inactive species (e.g., fish)
Hot Vents - Deep Sea Trophic
Islands
•  Hot Vents - sites usually on oceanic ridges where
hot water emerges from vents, associated with
volcanic activity
•  Sulfide emerges from vents, which supports large
numbers of sulfide-oxidizing bacteria, which in
turn support large scale animal community. Most
animals live in cooler water just adjacent to hot
vent source
•  Examples: Vestimentifera (Annelid), bivalves –
endosymbiotic bacteria; galatheid crabs feed
directly on bacterial mats
Sulfide life style – two flavors
•  Direct consumption of sulfide processing bacteria –
grazing molluscs, crabs- bacteria on rock surfaces
•  Intracellular symbioses – bacteria on and
intracellular in gills of bivalves, in vestimentiferan
worms – specialized hemoglobin binds to sulfide
Vestimentiferan tube worms at a hot vent
Galatheid crab
Vestimentiferan tube worms at a hot vent
Courtesy Richard Lutz
Vestimentiferan worms, zoarcid fish
Vestimentiferan worms, zoarcid fish
Population of hot-vent bivalve Calyptogena magnifica
Cold Seeps - Other Deep Sea
Trophic Islands
•  Deep sea escarpments may be sites for
leaking of high concentrations of
hydrocarbons
•  These sites also have sulfide based trophic
system with other bivalve and
vestimentiferan species that depend upon
sulfur bacterial symbionts
Whale carcasses!
•  Fallen whale carcass – scavengers,
decomposition, and then…..
http://extrememarine.org.uk/
Sulfide symbionts in boneworms!!
Osedax frankpressi – boneworm – has endosymbiotic
sulfide oxidizing bacteria, worm body grows into bone,
this species has dwarf males
Conclusion
•  Deep sea can have very fast growth and
activity IF there is a nutritive source
•  “nutritive islands” include hot vents, cold
seeps, large carcasses that fall to the deep
sea bed, even hunks of wood
Deep Water Coral Mounds
•  On deep sea mounts
•  Domination by corals, often > 500 y old
colonies
•  Diverse species live with corals
•  Very endangered because of associated
deep water fish of commercial interest like
orange roughy
FIG. 16.16 The deep-water coral Lophelia pertusa with squat lobster and
sea urchin. (Photograph by Steve W. Ross and others)
Marine Biology:
Function, Biodiversity,
Ecology, 4/e
Levinton
Copyright © 2014 by Oxford
University Press
FIG. 16.17 Some organisms found on deep-sea coral mounds.
(a) Large antipatharian coral (probably Leiopathes) on a northeast Atlantic
carbonate mound. (Image courtesy of AWI & I. Fremer)
(b) These examples show fauna from a giant carbonate mound in the
northeast Atlantic: (1) isopod Natatolana borealis, (2) gastropod
Boreotrophon clavatus, (3) brachiopod Macandrevia cranium,
(4) hydrocoral Pliobothrus symmeticus. (Images courtesy of L. A. Henry,
Scottish Association for Marine Science)
Marine Biology:
Function, Biodiversity,
Ecology, 4/e
Levinton
Copyright © 2014 by Oxford
University Press
Deep-sea biodiversity changes
•  Problem with sampling, great depths make it
difficult to recover benthic samples
•  Sanders and Hessler established transect from
Gay Head (Martha’s Vineyard, Island, near
Cape Cod) to Bermuda
•  Used bottom sampler with closing device
•  Found that muddy deep-sea floor biodiversity
was very high, in contrast to previous idea of
low species numbers
•  Concluded that deep sea is very diverse
Deep-sea biodiversity changes
•  Problem with sampling:
Number of
species recovered
Correction for sample size - Rarefaction
Number of individuals collected
2
Deep-sea biodiversity changes
•  Problem with sampling:
Number of
species recovered
Correction for sample size - Rarefaction
Number of individuals collected
2
Deep-sea biodiversity changes 3
•  Results: Number of species in deep sea
soft bottoms increases to maximum at
1500 - 2000 m depth, then decreases with
increasing depth to 4000m on abyssal
bottoms
•  In remote abyssal bottoms, diversity
declines and carnivorous animals are
conspicuously less frequent (low
population sizes of potential prey species)
Deep-sea biodiversity changes 4
Deep-sea biodiversity changes. Why?
•  Environmental stability hypothesis –
species accumulate in stable
environment, less extinction
•  Population size effect - explains decline in
abyss -carnivores?
•  Possible greater age of the deep sea,
•  Particle size diversity greater at depths of
ca. 1500m – might cause higher diversity
Environmental stability in the deep sea
Shelf waters less physically constant than deep waters
Seasonal variation in bottom-water temperature at different depths
The End
Have a nice summer!!
Final Thursday, May 12 here at
1115 AM