Download Chapter 15: Animals of the benthic environment

CHAPTER 15
Animals of the Benthic Environment
Distribution of benthic organisms
Fig. 15.1

More benthic productivity when closely beneath areas of
high surface primary productivity
 Mainly on continental shelves
 Affected by surface ocean currents
Benthic organisms on rocky shores

Epifauna
(on top)
 Attached to substrate
(e.g., marine algae)
 Move on/over seafloor
(e.g., crabs, snails)

Moderate diversity of
species
 Greatest animal
diversity at tropical
latitudes
 Greatest algae diversity
at mid-latitudes
http://dnr.metrokc.gov/wlr/waterres
Epifauna
Intertidal
zonation
(rocky
shore)
Fig. 15.2 a
Epifauna

Spray zone
(supratidal)
 Have to avoid
drying out
 Many animals have
shells
 Very few species of
marine algae
Fig. 15.2b
Epifauna

High tide zone
 Avoid drying out so
animals have shells
 Marine algae—rock
weeds with thick cell
walls
http://www.ecology.org/ecophoto/algae/Thumbnails/Plant%20Images-
Epifauna

Middle tide zone
 More types of marine algae
 Soft-bodied animals
http://www.wallawalla.edu/academics/departments/biology/rosario/inverts/Mollusca/Bivalvia/Mytiloida/Mytilidae/Pisaster%20Predate%20mussels.jpg
Epifauna

Low tide zone
 Abundant algae
 Many animals hidden by sea weed and sea
grass
 Crabs abundant in all intertidal zones
http://www.fisherycrisis.com/chondrus/fig32.JPG
Benthic organisms on sedimentcovered shores


Similar intertidal zones to
that of rocky shores
Less species diversity
 Greater number of organisms
 Mostly infauna – burrow into
sediment

Microbial communities
Coquina (Donax)
http://bivalves.info/Donax_hanleyanus.jpg
Intertidal zonation (sandy shore)
Fig. 15.8
Benthic organisms on sedimentcovered shores

Energy level along shore depends on
 Wave strength
 Longshore current strength

Wave/current energy determines
habitat…





Coarse boulder beaches
Sand beaches
Salt marshes
Mud flats
Fine-grained, flat-lying tidal flat more
stable than high energy sandy beach
Sandy beaches
Animals burrow
 Bivalve mollusks
 Annelid worms
 Crustaceans
 Echinoderms
 Meiofauna

http://photography.nationalgeographic.com/staticfiles/NGS/Shared/StaticFiles/Photography/Images/POD/g/ghost-crab-hiding-760340-sw.jpg
Mud flats
Eelgrass and turtle grass common
 Bivalves and other mollusks
 Fiddler crabs

http://www.sms.si.edu/irlspec/images/06PhotoContest/06DeWolfeH3.jpg
http://www.lacoast.gov/articles/bms/1/3_mud_flat_ground_view.jpg
Shallow ocean floor
Continental shelf
 Mainly sediment covered
 Kelp forest associated with rocky
seafloor

 Also lobsters
 Oysters
http://www.ianskipworth.com/pho
to/pcd1742/kelp_forest_15_4.jpg
Figure 15.14a,b
Figure 15.14c
Coral reefs


Most coral polyps live in large colonies
Hard calcium carbonate structures cemented
together by coralline algae
www.gettankedaquariums.com
www.mpm.edu/images
Coral reefs

Coral reefs limited to
 Warm (but not hot) seawater
 Sunlight (for symbiotic algae)
 Strong waves or currents
 Clear seawater
 Normal salinity
 Hard substrate
www.waterfrontchattanooga.com/Newsroom/High_res
Reef-building corals
Fig. 15-17
Symbiosis of coral and algae
Coral reefs made of algae, mollusks, foraminifers as
well as corals
 Hermatypic coral mutualistic relationship with algae –
zooxanthellae
 Algae provide food
 Corals provide nutrients

Soft coral polyp (Lobophytum compactum). Green shows
the polyp tissue, while the red shows the zooxanthellae.
http://www.reefed.edu.au/explorer/images
Importance of coral reefs

Largest structures created by living
organisms
 Great Barrier Reef, Australia, more than 2000
km (1250 m) long
Great diversity of species
 Important tourist locales
 Fisheries
 Reefs protect shorelines

Humans and coral reefs


Activities such as fishing,
tourist collecting, sediment
influx due to shore
development harm coral reefs
Sewage discharge and
agricultural fertilizers increase
nutrients in reef waters
 Hermatypic corals thrive at low
nutrient levels
 Phytoplankton overwhelm at high
nutrient levels
 Bioerosion of coral reef by algaeeating organisms
Coral covered with macroalgae
http://daac.gsfc.nasa.gov/oceancolor/images/coral_reef_algae.jpg
○
Other problems
Smoothering by dredging, runoff
 Fishing practices, harvesting
 Pollution
 Global warming

Worm Reefs
www.floridaoceanographic.org/environ/images
• Sabellariid worms
(Phragmatopoma caudata) form
shallow reefs
• St. Augustine to south end of
Biscayne Bay
• Provide habitat for many
organisms
www.stlucieco.gov/erd/threatened-endangered







Sabellariid worms – polychaete worms
Adult worms (3/4 - 2 in. long) build reefs on limestone and
coquina formations, jetties
Build sand hoods over tubes to reduce desiccation at low tide.
Protective tubes made of sand, joined to neighbors to build rigid,
wave resistant structures.
15,000 to 60,000 worms per m2
Live up to 10½ years.
Thais (oyster drill) is an important predator
Benthic organisms on
the deep seafloor


Little known habitat – only
accessable via dredge and
some submersibles and ROVs
Bathyal, abyssal, hadal zones
 Little to no sunlight
 About the same temperature
 About the same salinity
 Oxygen content relatively high
 Pressure can be enormous
 Bottom currents usually slow
http://library.thinkquest.org/17297/images/alvin.gif
http://www.whoi.edu/science/B/people/sbeaulieu/rad_patch_by_mound.jpg
Food sources in deep seafloor
Most food sinks from surface waters
 Low supply and “patchy”

Fig. 15.22
Deep-sea hydrothermal vent
biocommunities




First discovered
1977
Chemosynthesis
Archaea use sea
floor chemicals to
make organic matter
Unique communities
 Tube worms
 Giant clams and
mussels
 Crabs
 Microbial mats
http://i.treehugger.com/images/2007/10/24/deep-sea%20hydrothermal%20vent-jj-001.jpg
Figure 15.27

Chemosynthesis
 Archaea use sea floor chemicals to make organic
matter
Figure 15.25b
Global hydrothermal vent
fields
Fig. 15.24
Deep-sea hydrothermal vent
biocommunities
Vents active for years or decades
 Animals species similar at widely
separated vents
 Larvae drift from site to site
 “Dead whale hypothesis”

○
○
How do organisms go from one hydrothermal vent to
another?
“Dead whale hypothesis” – Dispersal of vent organisms
 Pelagic eggs/larvae disperse to other food patches or
vent fields
- Methane-bearing springs on continental shelves and
slopes are more common than originally thought
- Possible dispersal to carcasses – support vent
organisms
- Take years to decompose
- Use as "stepping stones
Whale carcass with worms, sea cucumbers
www.mbari.org
Figure 15.C
Fish carcass
On ocean
floor
Deep-sea hydrothermal vent
biocommunities
Life may have originated at hydrothermal
vents
 Chemosynthesis also occurs at low
temperature seeps

 Hypersaline seeps
 Hydrocarbon seeps
 Subduction zone seeps
Figure 15.28 & 15.29
Beneath the sea floor

Deep biosphere
 Microbes live in porous sea floor
 Might represent much of Earth’s total
biomass
In may 2008, prokaryotes were
reported in mud cores extracted
from between 860 to 1626
meters beneath the sea floor
off Newfoundland. Cells were
100-1000 fold denser than in
terrestrial cores of similar
depth and about 5-10% of the
cells were dividing.
http://environment.newscientist.com/channel/ear
th/deep-sea/dn13960-huge-hidden-biomasslives-deep- beneath-the-oceans.html