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MARINE ECOLOGY BOOK
By: Christina Craciun

Marine Ecology Book
Created by Christina Craciun
for
Marine Ecology Class at MVHS

Chapter 1 - Physical Oceanography

Chapter 2 - Ecology and Ecosystems

Chapter 3 - Seaweed

Class Chlorophyta
Green Algae
Anatomy :
Blade - leaf like part
Stipe - “stem” of a seaweed
Float - gas-filled bladder that keeps the
seaweed floating
Holdfast - anchors the seaweed to a solid
surface
Unique features/behavior :
● Sargassum - large floating seaweed
are food, help turtles migrate and
organisms hide from their predators
● Kelp - large seaweeds that grow 1
meter a day
Class :
● Rhodophyta – red algae
● Chlorophyta – green algae
● Phaeophyta – brown algae
Class Rhodophyta
Red Algae
Class Phaephyta
Brown Algae

Importance :
● Help turtles migrate
● Provide foods to organisms
● Helps organism hide from predators
● First organism in marine food chains
Found in :
●
●
●
Ocean, rivers, lakes, and other water bodies
8-40 m in most oceans, some are found to
depths of 250 m in particularly clear waters
such as the Mediterranean, Caribbean, and
Brazil
Cholorphyta - freshwater and marine habitats
but some are terrestrial, growing on soil,
trees, or rocks .

Class Chlorophyta
Green Algae
Characteristics :
● Unicellular (one cell),
multicellular (many cells),
colonial (living as a loose
aggregation of cells) or
coenocytic (composed of
one large cell without
cross-walls)
● Membrane-bound
chloroplasts and nuclei.
Class Rhodophyta
Red Algae
Characteristics :
● Walls are made of cellulose
and agars and carrageenans
● Several groups are eaten
● Absence of flagella and
centrioles
● No chloroplast endoplasmic
reticulum
Class Phaephyta
Brown Algae
Characteristics :
● Most are marine
● Larger and more species are
found in cold water
● Unicellular or multicellular
body
● Cells are eukaryotic

Chapter 4 - Porifera

Anatomy : simple - specialized cells, but no
tissues or organs
Symmetry : asymmetric
Unique features/behavior:
● sessile, meaning it doesn't move
● no tissues or organs
● filter feeders, filter food through their
bodies
● internal skeleton of spicules
● central cavity and/or series of
branching chambers
● asexual and sexual reproduction
● no mouth
Kingdom : Animalia
Phylum : Porifera
Class :
● Class Hexactinellida - glass sponge
● Class Calcarea - calcareous sponges
● Class Demospongiae - demosponges
Class
Hexactinellida
Class Demospongiae
Barrel sponge
Class
Calcarea

Importance :
●
●
●
Found in :
●
●
●
●
●
Changes in water quality
Collect bacteria as they feed that may be able
to turn ammonium from the sponge’s
breathing into nitrogen gas that releases into
the atmosphere
Prevent harmful ecosystem changes
99% of all sponges live in marine water
1% live in freshwater
8km deep on the ocean floor
Higher number in the tropics of all regions
because of the warmer water
Prefer clearer water over murky waters
because murky water can clog the pores of
the sponge

Class Hexactinellida
Venus Flower Basket
Characteristics :
● Sometimes called
'Glass sponges'
● have spicules made
from silica
Class Demospongiae
Bath Sponge
Characteristics :
● spicules made from silica
and/or spongin
Class Calcarea
Leucosolenia
Characteristics :
● these sponges have
spicules of calcium
carbonate

Chapter 5: Cnidaria

Anatomy :
● Epidermis - skin
● Gastrodermis - inner layer of cells that lines a
large open cavity.
● Mesoglea - jelly like material between the
epidermis and gastrodermis.
● Basic digestive tract - only one opening and
large internal cavity a.k.a the gastrovascular
cavity.
Symmetry : Radial symmetry - many planes can be
drawn through the central axis that will divide the
animal into equivalent halves.
Unique features/behaviors :
●
●
2 different body plans - polyp, one opening
(mouth) which is surrounded by tentacles.
medusa, free floating such as a jelly fish.
stinging cells - cnida, stinging organelle within a
cnidocyte. nematocysts, spearing type cnida
which are discharged when the cnidocill, the
trigger, contacts another object, can also be
triggered by certain chemicals released by prey.
Kingdom : Animalia
Phylum: Cnidaria
Class :
● Class Hydrozoa - fire coral and portuguese
man-o-war
● Class Scyphozoa - true jellyfish
●
●
Class Cubozoa - box jellyfish
Class Anthozoa - sea anemones, corals and
gorgonians

Importance :
● can affect the amount of zooplankton and fish
populations by preying on fish larvae and eggs.
● some are eaten in some areas of Asia and North
American
● coral skeletons are used as building material such
as cement.
● cnidarian skeletons can make jewelry
● Can affect country's economy
Found in :
● Anthozoans - benthic, bottom dwellers
● soft and hard corals coexist in virtually all tropical
areas
● Indo-Pacific coral reefs - hard coral
● Caribbean coral reefs - soft corals
● Temperate rocky intertidal zones - sea
anemones.
● Antarctic seabed - anemones, near the deep-sea
hot vents.
Fire Coral
Pacific Sea Nettle

Class Hydrozoa
Portuguese Man-o-War
Class Scyphozoa
Moon Jelly
Characteristics :
Characteristics :
● Exoskeleton composed
of chitin
●
●
Radially symmetric
Dominant medusa
● Are almost entirely
marine and predators ●
stage.
Short or long
● Stinging cells called
Cnidocytes
tentacles with
nematocysts.
● Mostly
free-swimming
Class Cubozoa
South African Box
Jellyfish
Characteristics :
● considered
members of the
plankton.
● medusa is
predominant life
stage.
● photoreceptors:
organs that sense
light or dark
Class Anthozoa
Cylinder Anemone
Characteristics :
● Mouth has
tentacles w/
nematocysts.
● Secretes substance
outside of body to
support & protect
soft body tissues.

Chapter 6: Mollusca

Anatomy :
●
Mantle - extension of the body wall,
responsible for secreting the shell and it
encloses the mantle cavity.
● Head-foot: region containing the head with its
mouth and sensory organs and the foot
● Visceral mask: body region containing the
other organ systems
Symmetry :
● Bilateral symmetry - divisible into symmetrical
halves on either side of a unique plane.
Unique features/ behavior :
● Shells - made of calcium carbonate, chitin, and
conchiolin. Not all have shells.
●
●
●
Foot - acts as a sucker that helps the animal
attach to a hard surface.
Many have at least one pair or only one
feather-shaped gill found in the mantle cavity.
Radula - acts as a tongue line with teeth, used
to scrape bacteria and algae off rocks. Most
have a radula
Kingdom - Animalia
Phylum - Mollusca
Class -
● Class Polyplacophora - chitons.
● Class Scaphopoda - tusk shells.
●
●
●
Class Gastropoda - abalone, conch, limpet,
nudibranch, slug, snail, whelk.
Class Bivalvia - clam, mussel, oyster, scallop.
Class Cephalopoda - nautilus, cuttlefish, squid,
octopus.

Importance :
● food for humans and other animals
● Some snails are intermediate hosts to parasites
● Shipworms cause extensive damage to
wooden pilings and boat hulls, but also prevent
wood from accumulating in the marine
environment
● A few bivalves have commensal relationships
(attaching to other animals)
Found in :
●
most live in the ocean, but some live on land
and in fresh water
Class Polyplacophora
Chiton
Class Scaphopoda
Tusk Shell
Class Cephalopoda
Nautilus
Class Gastropoda
Abalone
Class Bivalvia
Mussel

Class
Polyplacophora
Chiton
Class Scaphopoda
Tusk Shell
Class
Gastropoda
Conch
Class Bivalvia
Clam
Class Cephalopoda
Cuttlefish
Characteristics :
● flattened
bodies, usually
with 8 plates
● attach to rocks
in intertidal
zone
● roll up into ball
for protection
when removed
● scrape off
algae w/ radula
Characteristics : Characteristics :
● Resemble
elephant
●
tusks
(univalve)
● Shells open at ●
both ends
● Burrow into
sand
most have shells
that are one piece
can withdraw into
shell for protection
& close opening
w/ a cover called
an operculum
Characteristics :
● shells have 2
jointed halves
called valves
● have no head or
radula
● free swimmers
use jet
propulsion
Characteristics :
● when disturbed
releases cloud
of inky fluid
called sepia
● have 3 hearts
& pump blue
blood

Chapter 7: Arthropoda

Anatomy:
● Segmented body and appendages.
● Exoskeleton - made of chitin and proteins.
Symmetry:
● Bilateral symmetry - one plane through the center
divides the organism into equal parts and
symmetrical halves.
Unique features/behaviors:
● Open circulatory system - blood is pumped
through open spaces called sinuses in order to
reach tissues.
● Mandibules - complex structure that allows for
chewing of food.
Kingdom : Animalia
Phylum : Arthropoda
Class :
● Class Merostomata - horseshoe crab
● Class Pycnogonida - sea spider
● Class Copepoda - sea louse
● Class Cirripeds - barnacle
● Class Ampipoda - sand fleas

Importance:
● Most important part of the ocean food chain
● Recyclers in many ecosystems
Found in:
● Ocean environments
Class Pycnogonida
Sea Spider
Class Copepoda
Sea Louse
Class Merostomata
Horseshoe Crab
Class Cirripeds
Barnacle
Class Ampipoda
Sand Fleas

Class Merostomata
Horseshoe Crab
Class Pycnogonida
Sea Spider
Class Cirripeds
Barnacle
Class Copepoda
Sea Louse
Class Ampipoda
Sand Fleas
Characteristics:
● Not true crabs
● Primarily
scavengers, but
sometimes feed
on worms,
mollusks, and
other small
animals
● Pick up food with
pincers
Characteristics: Characteristics:
● Small,thin
bodies with long
appendages
●
● Male carry eggs
until they hatch
● Palps -
appendages
used as
sensory organs
Can be attached
to almost
anything
● Cirripeds -
modified
appendages for
feeding
Characteristics: Characteristics:
● Most are less
than 3mm long
● Very small,
grow up to 11
● Filter feeders
that rely on
phytoplankton
●
inches
Last 3
appendages
● Some are
predatory and
attack young
fish in swarms
●
●
are backward
Live near high
tide line
Feed on algae
or plant and
animal wastes

Chapter 8: Echinodermata

Anatomy:
● Endoskeleton - internal skeleton
● Water-vascular system - hydraulic system that
aids in locomotion, feeding, gas exchange,
excretion
● Pedicellariae - small pincer-like structures that are
used to keep the body surface clean and free of
parasites and larvae
Symmetry:
● Pentaradial symmetry - Body can be split
symmetrically in 5 ways
Unique features/behaviors:
● Some are carnivorous, others are detritus
foragers, or planktonic feeders.
● Reproduction - release sperm and eggs into the
water.
● Can regenerate missing limbs, arms, spines -
even intestines
● Some can automize/detach rays when they are
disturbed
Kingdom: Animalia
Phylum: Echinodermata
Class:
● Asteroidea - sea stars
● Ophiuroidea - brittle stars
● Echinoidea - sea urchins & sand dollars
● Crinoidea - sea lily
● Holothuroidea - sea cucumber

Importance:
●
●
●
●
Found in:
●
●
Important part of ocean food chain
Sand dollars and sea cucumbers burrow into the
sand, providing more oxygen at greater depths of
the sea floor.
Starfish prevent the growth of algae on coral reefs.
Many sea cucumbers provide a habitat for
parasites such as crabs, worms, and snails.
Most echinoderms are benthic
Members of Holothuroidea and Crinoidea are
often found in deep sea environments.
Class Ophiuroidea
Brittle Star
Class Echinoidea
Sand Dollars
Class Asteroidea
Sea Star
Class Crinoidea
Sea Lily
Class Holothuroidea
Sea Cucumber

Class Asteroidea
Sea Star
Class Ophiuroidea
Brittle Star
Class Echinoidea
Sand Dollars
Class Holothuroidea
Sea Cucumber
Class Crinoidea
Sea Lily
Characteristics: Characteristics: Characteristics:
● Eat invertebrates ● Slender arms ●
such as bivalves
and occasionally
compared to
central disk
fish
● Tend to avoid a.k.a test.
● Sea stars have light
●
the ability to ● Autotomize -
regrow a new ray detach a ray burrowing
● Eggs and sperm when disturbed ●
are released into ● Detached ray
the water
quivers wildly to
distract predators
Body enclosed by
a hard, circular
endoskeleton
Sand dollars
spines - used for
Sea urchins have
a chewing
structure in their
mouth called
Aristotle’s lantern
Characteristics:
● Elongated bodies
● Respiratory tree
● Aid in gas
exchange
● Oral tentacles
● Cuverian tubules -
sticky spaghetti-like
tubules released
from the anus to
deter potential
predators
Characteristics:
● Look like
flowers
● Some are
able to swim
● Suspension
feeders -
feed by straining
suspended matter
and food particles
from water

Chapter 9: Fish

Anatomy: