Name: _____________________
Per;______________
Benthic Organisms
A) The benthic region
1) The ocean can be divided into two general zones:
a) Pelagic zone – the zone of the ocean which is open-ocean.
b) Benthic Zone – anything underwater near or on the ocean floor
(I) There are 5 different types of benthic regions of the ocean
(i) Rocky Shores
(ii) Sediment-Covered Shores
(iii)
The subtidal continental shelf
(iv) Coral Reefs
(v) Deep Ocean Floor
A) Rocky shores
1) Rocky shores – benthic environments covered with rock that become partially exposed by the tides
2) Arias of the rocky shore community
a) One of the most predominate features of all rocky shore communities is thought the world, certain
species are always found in a given
height above the waterline
b)
Vertical Zonation – The distinct
banded pattern found on all
rocky shores formed by certain
organisms always living at certain
heights above the shore
3) There are three major zones characterized
by how often the zone is covered with
water
a) The upper tide zone
Rocky shores have distinct vertical Zonation marking
b) The middle tide zone
certain heights above sea level where certain organisms
c) The lower tide zone
have specially adapted to live
4) The upper tide zone - A mostly dry zone of the rocky shore that is covered with water only during
high tide
(I) organisms here must be well adapted to desiccation they are above water for most of the day,
(II) Most of the upper intertidal animals avoid desiccation by running and hiding
(i) Run and hide - When the tide goes out these organisms go somewhere wet and wait
it out,
5) Middle tide zone – A zone of the rocky shore that is above and below water for equal parts of the
day
a) The middle Intertidal zone is home to the heist variety of organisms because it undergoes the most
dramatic environmental changes with the tides, covered with water during part of the day and
uncovered the other part of the day
b) Most animals in the middle intertidal zone avoid desiccation by sealing water in their shells
(I) Clam up- Organisms that have some sort of protective coating like a shell that they can
seal water in at low tide to avoid desiccation
c) Lower tide zone – A zone of the rocky shore that is covered with water almost all the
time and only exposed during the lowest low tides
(I) The lower Intertidal zone is dominated by seaweeds who, because they are covered with water for
most of their lives are poorly adapted to desiccation, they just dry out and hope the tide will
come back in soon
(i) Sit and bear it – organisms that can resist loosing large amounts of water and
still live
6) Very few organisms can burrow into rock, (rock burrowing clams can do it in soft rock like sandstone)
so burrowing is the least common adaptation for desiccation
A) Sediment covered shores
1) Sediment covered shores– shores covered with gravel, sand, silt and clay
2) Formation of sediment covered shores
a) There are two basic types of sediment covered shores, sandy beaches and muddy salt
marshes.
b) The type of sediment covered shore that forms depends largely on wave energy in that area
Sandy beaches tend to be covered with larger grain particles because the large amount of wave
energy washes away any smaller grain particles. On the other hand muddy salt marshes are
covered with smaller silt and clay particles which traps large amounts of detritus
c) Sandy beaches – sediment covered benthic environment created by areas of stronger wave
action which washes away all smaller sediment leaving only gravel and sand
d) Muddy salt marshes – sediment covered benthos environments created by areas of less wave
action which allows mud (silt and clay) to settle on top of sand and gravel
B) Zonation of the sediment covered shore community
1) Sandy beaches and muddy slat marshes have two separate zones:
a) Sandy beach Zonation
(I) There are two basic zones to a sandy beach, the dryer upper Intertidal beach, and the more wet
subtidal beach
(i) The upper beach is inhabited by Meiofauna and inphanic animals like smaller lug
and bristle worms
(between sand particles)
(burrow)
(ii) The lower beach is inhabited by epiphanic animals that don’t tend to burrow as much
such as sea cucumbers, large crabs, sand dollars and snails
(II) Most sandy beach animals resist desiccation by burrowing
(III) There are more filter feeders than deposit feeders on a sandy beach because the
large amount of wave action creates rapidly moving water that is relatively free of tiny
non edible debris
(i) Olive shells make a mucus net to capture their food as it is washed in the tides
(i) Sand crabs
combine filter
feeding with
locomotion. They
uncover
themselves right
before a wave
hits. They then
ride the wave up
the shore
extending there
antennae to catch
any food particles
suspended in the
water. As the
water washes out
There are two basic zones of sand beaches, the dry Intertidal zone filled
they burrow to
with mostly infauna and the lower subtidal zone which is inhabited by
keep from getting
mostly epifauna
washed back
down. at the end of the day they do the opposite
b) Muddy salt marshes
(I) There are three basic zones to a
muddy salt marsh:
(i) The lower mud flat – an aria that
usually become completely
covered with water during
high tide, which helps
circulate nutrients and detritus
(ii) Cord grass aria – an aria of
marsh plants that provide
shelter and food for many
smaller marine invertebrates in this
area such as crabs snails, and small
fish
(iii)Transition zone - area of muddy
salt marshes consists of cord grass
mixed with other terrestrial or land
plants
(II) Muddy salt marsh animals tend to be
deposit feeders rather than
suspension feeders for two reasons
(i) The finer sediments clog up
filter feeders nets
(ii) There is a large amount of detritus
The three zones of a muddy salt marsh are the lower
in the mud that is a great source of
mud flat, the cord grass aria, and finally the transition
nutrients
zone
 Deposit feeders in
muddy salt marshes
 Some clams use there long siphons to suck food of the surface of the mud
 Fiddler crabs fed at low tide, using there pincers to scoop mud up into their mouths,
they extract the detritus from the mud by coughing up water from their gill chamber
to their mouth. This water allows the lighter detritus in the mud to float to the top and
be swallowed.
The clean sand
is spat out in
neat balls and
kicked aside
2) Predation sediment covered shores
a) Predation varies with the tides
on sediment covered shores,
fish feed primarily at
high tide while birds
feed primarily at low tide
b) Birds who prey on
Birds who prey on sediment covered shores usually have
specialized bills used to probe into different depths into
the mud looking for a particular Infauna animal
sediment covered shores usually have specialized bills used to probe into different depths into
the mud looking for a particular Infauna animal
B) The subtidal continental shelf
Subtidal continental shelf – the area extending from the lowest tidal edge of rocky and sediment covered
shores to the abyssal plain
1) There are two main arias of the subtidal continental shelf
a) soft bottom community- areas of the continental shelf covered with sand or mud. These are
the Subtidal regions of sediment covered shorelines
b) hard bottom communities - areas of the continental shelf covered with rock or the hard
skeletons of various marine invertebrates. These are the Subtidal regions of rocky shorelines
2) Adaptations for living on subtidal continental shelf
a) Feeding
(I) Feeding in the Soft bottom subtidal communities
(i) Primary production in the soft bottom continental shelf is due mostly to sea grass
which has roots that can anchor themselves to the soft bottom
(ii) Most organisms of the soft bottom subtidal region feed on detritus through deposit or
suspension feeding
Sea cucumbers take in large
amounts of sand, and then digest
Sand dollars are grazers which have
the detritus and Meiofauna that
adapted a flattened body shape to help
lives between the particles. When them scrape algae off the ocean floor
it is done it excretes the sand in
neat lumps on the ocean bottom
(II) Feeding in the hard bottom subtidal communities
(i) Hard bottom subtidal communities are much more productive than soft bottom
community.
 Large amounts of seaweeds and
algae is able to anchor itself to the rock with
their holdfasts and form highly productive
environments
 Kelp beds are especially common in cold
waters, these 100 foot long seaweeds form
environments not unlike rainforests on the hard
bottom subtidal shore, with kelp canopies at the top
of the water blocking out most of the sunlight from
the under story
(ii) Because primary production is so prevalent hard bottom
subtidal communities have a number of grazing
fish and snails that life off the algae and seaweed
Sea Urchins are some of the most
important grazer in all the ocean.
They single handedly keep Kelp
and other MicroAge in check.


The grazing in this aria is so intense that many seaweeds have developed defenses
against grazing like production of poisons such as sulfuric acid and phenols, and well as
the ability to quickly regenerate eaten parts
sea urchins are the most important grazers in the hard bottom subtidal community. The
explosion of their populations in some areas has caused the complete destruction of kelp
beds in some areas.
C) Coral Reefs
1) Coral reefs- vast amounts of limestone (calcium carbonate) that is deposited by living
organisms (not just coral) over thousands or even millions of years
a) There are some corals that are non-reef building coral. These corals are
mostly known as soft coral
2) The beginning of any coral reefs starts with one coral larva settling on a hard surface like a rock
exposed bedrock on the ocean floor.
a) The portion of the floor that the polyp settles on must have environmental
b)
conditions of temperature, salinity, light availability, and nutrient content
favorable for coral growth or the coral larvae will die
Coral reefs rarely grow on sediment covered bottoms, there must be a initial hard
surface
3) Formation of Coral reefs
a) After settling this coral larva immediately metamorphosis’ into a single founder
polyp which divides over and over again over thousands of years until a reef is visible.
(I) Once they get started the coral will create its own hard surface on which to build and the reef will
expand
b) Since all reefs come from a single dividing polyp, most coral reefs const of only identical clones of
one or a few polyps that all share a single digestive and nervous system
(I) The great barrier reef only has 2,500 genetically different coral polyps that have been cloned
trillions of times, but it covers 80,000 mi2. That’s like having half the
population of north Penn high school spread over an area twice the zize of
Pennsylvania. Or one person every 32 mi2
4) Three types of coral reefs
a) There are three basic types of coral reefs, fringing reefs, barrier reefs and
atolls.
(I) Fringing reefs – a coral reef that develops as a narrow band close to or against a
shoreline
(i) Because fringing reefs are so close to the shore they are subject to more extreme conditions
such as sediment build up and exposure at low tide, both of which could kill the coral
Fringing reefs develop against shorelines
(II) Barrier reefs – coral reefs that develops a distance away from the shoreline and thus has a
lagoon
(i) Sand cay’s or “keys” form on barrier reef crests
 Sand cay’s (Keys) – small islands that form when waves pile up sand and clay on a reef
crest
The difference between a barrier reef and a fringing reef is that a barrier
reef has a lagoon between them and a shoreline
(III) Atolls – rings of reefs with steep reef slopes that enclose a lagoon
(i) Atolls are home to the most brilliant and dramatic coral growth because they are out in the
middle of the ocean, and so not subject to as harsh environmental conditions created by being
close to land
(ii) Since all other types of coral reefs need land and shallow water to form, it was a mystery as
to how rings of coral islands can form in the middle of the ocean
(iii)Darwin was the first one to propose that Atolls must form on subsiding or eroding volcanic
islands
(iv) Formation of atolls:
 First a fringing reef forms around a volcanic island

A barrier reef then forms as the volcano goes extinct and starts to erode away
from the reef, creating a lagoon between the reef and the island.

Eventually the island sinks altogether leaving only a ring of living growing coral – an
atoll
5) Adaptations for living on coral reefs
a) Feeding
(I) Coral must be adapted to survive waters low in nutrients
(i) Coral reefs are found to have shockingly low levels of nutrients even
though they are host to some of the most diverse communities in the ocean.
(ii) Nutrient recycling – the process by with the nitrates, phosphates, and
carbon dioxide excreted by the coral polyp are taken up immediately by the
zooxanthellae and converted to oxygen and sugar which are then taken up by the coral polyp
and converted back to nitrates phosphates and carbon dioxide
 Because the waists of one organism become the food for the next these coral
polyps can survive in waters that lack large consentrations of
nutrients
b) Competing for space
(I) With so many different organisms inhaling such a small area, space is at a premium for hard
and soft coral as well as fish
(i) Hard corals complete for space in two main ways
 some rapidly grow upward and then branch out cutting there neighbors off
from light
 other types of corals have adapted the ability
extrude there stomachs on
neighboring corals and digest them alive, or
extend long stinging tentacles which attack
neighboring colonies
(ii) Soft corals have adapted three main ways to
compete for space
 Soft corals can grow more
rapidly than hard corals because they
don’t have to build calcium carbonate
skeletons, and so they can more rapidly
populate a newly exposed area
Scientists believe so many fish can
 Some soft corals have adapted to grow
occupy the same space on a reef via
limestone spines, as well as
random chance and/or because they all
noxious and toxic chemicals that discourage
have slightly different ecological niches
fish from eating them
 Furthermore some soft corals can detach themselves and move if conditions become
unfavorable for growth
(iii) Scientists have two leading theories on how fish compete for space on a reef
 lottery hypothesis – since fish’s ecological niche overlap so much, the species that win
and loose are largely just based on chance

determinant hypotheses – even though reef fish have very similar
ecological niches, the ones with the exact same niche as others die out
while the ones with slight variation thrive
D) Deep ocean floor
1) Zonation of the deep ocean floor
a) There are 4 main areas in witch life is found on the deep ocean floor:
(I) Abyssal plain – large flat region of the ocean covered with sediment
the abyssal plain, is not dependent on chemosynthetic bacteria to
form the basis of the food web.
b) The remaining three areas, deep sea hydrothermal vents, cold seeps, and dead

Cold seeps – areas of the deep
Deep sea hydrothermal vents Dead bodies – dead whales and
ocean floor where hydrogen
(Black smokers) - undersea hot other organisms that have settled
sulfide and natural gas have
springs associated with the mid on the deep ocean floor
seeped out of the ocean floor and Atlantic ridge
settled in a low spot
bodies, are dependent of chemosynthetic bacteria as the main primary
producer
1) Adaptations for living on the deep ocean floor
a) Adaptations for living on the abyssal plan
(I) The main types of organisms found on the abyssal plan are deposit feeders who
have adapted to seek and eat dead material that floats down from the upper layers of the ocean
and settles on the bottom
(i) Deep sea cucumbers, brittle starts are the two types of deposit feeders that dominate the
ocean floor
(II) Predation in this area is relatively rare however there are some
(i) Most predators are inexplicably large, and have an elongated shape
(ii) These predators have adapted to have a generalized diet feeding on live organisms when
available as well as suspension feeding or scavenging when necessary
Deep sea fish that live on the abyssal plain tend to be elongates and adapted to hunt in low light
conditions. Most deep sea fish feed on live fish but also scavenge and suspension feed as well
2) Adaptations for living near deep sea hydrothermal vents
(I) Deep sea Chemosynthetic bacteria – bacteria that has adapted to take in hydrogen sulfide
emitted from hydrothermal vents and covert it to food which forms the bases for the deep
sea food web
b) The dominant animal in a hydrothermal vent community is the giant tube worm
(I) Giant tube worms don’t have a mouth or any digestive system, instead they have a specialized
organ called a feeding body which is packed with chemosynthetic
bacteria
(II) The bacteria in the feeding body perform chemosynthesis and pass the organic material to the
tube worm, in turn the tube worm takes in the hydrogen sulfide needed for chemosynthesis with
its red plume.
3) Adaptations for living near cold seeps
a) These arias are home to other organisms that have a mutualistic relationship
with chemosynthetic bacteria, such as mussels and giant clams
b) Since the water in cold seeps is so much more dense than surrounding water it looks like a lake
bordered by mussels, complete with a lapping shoreline
4) Adaptations for living on dead bodies
a) When scavengers are through eating the meat of the dead whale, the remains produce hydrogen
sulfide as they decay which creates communities like those seen at cold seeps and
hydrothermal vents with chemosynthetic bactera at the base.
b) Since cold seeps and hydrothermal vents eventually “die” or dry up the species that these geologic
areas support can only survive by constantly finding a new source of energy. It is thought that the
dead bodies provide a necessary stepping stone as many organisms use them as an
intermediate on the way to new vents and seeps