THE MARINE HABITAT
I.
INTRODUCTION
A. Most marine organisms live in the photic zone, as light brings about photosynthesis which
brings about consumers, which creates a habitat
II.
CLASSIFICATION OF LIVING THINGS
A. There are three domains
i. Archaea, Bacteria, and Eukarya
B. There is debate over how many KINGDOMS there are
i. Your book says 5 (recently more accepted that Monera split up into Archaeabacteria &
Eubacteria):
a. MONERA (DOMAIN ARCHAEA & DOMAIN BACTERIA)
1. Single-celled
2. Lack a discrete nucleus
3. EXAMPLES
a) Cyanobacteria (blue-green algae)
b) Heterotrophic bacteria
c) Archaea
b. PROTISTA (DOMAIN EUKARYA)
1. Single-celled
2. Multi-celled
3. Have a discrete nucleus
4. EXAMPLES
a) Marine Algae (microscopic mainly)
b) Protozoa
c. FUNGI (DOMAIN EUKARYA)
1. Multi-celled
2. Have a discrete cell wall which contains chitin (as opposed to cellulose)
3. EXAMPLES
a) Mold & Lichen
b) Decomposers mainly
d. PLANTAE (DOMAIN EUKARYA)
1. Multi-celled
2. Have a discrete cell wall which contains cellulose
3. They photosynthesize!
4. EXAMPLES
a) Surf Grass
b) Eelgrass
c) Mangrove Swamps
d) Salt Marshes
e) Marine Algae (multi-cellular & photosynthetic)
e. ANAMLIA (DOMAIN EUAKRYA)
1. Multi-celled
2. EXAMPLES
a) Pretty much everything else
b) Us
c) Fish
d) Simple sponges to complex vertebrates
III.
CLASSIFICATION OF MARINE THINGS (ORGANISMS)
A. There are two main divisions based on mobility: plankton & nekton
B. The rest are benthos
C. PLANKTON (free-floaters, planktos = wandering)
i. An individual member is a plankter
ii. It’s not that they can’t swim, just vertically
iii. PLANKTON TYPES BASED ON PURPOSE
a. PHYTOPLANKTON
1. Single-celled photosynthetic algae
b. ZOOPLANKTON
1. Single-celled herbivorous organisms
c. BACTERIAPLANKTON
1. Single-celled bacteria (no nucleus)
iv. In fact, most of the world’s biomass
v. 98% of marine species are bottom-dwelling
vi. PLANKTON TYPES BASED ON SIZE
a. Look at the chart given to you
vii. PLANKTON TYPES BASED ON LIFE CYCLE
a. HOLOPLANKTON
1. holo = whole
2. they spend their entire life as plankton
b. MEROPLANKTON
1. They spend part of their life as plankton
2. Typically, this is usually during larval and/or juvenile stage
D. NEKTON (swimmers, nektos = swimming)
i. Everything else, pretty much
ii. Everything that swims and can change its position horizontally
iii. Nekton can be divided up by Migration Patterns
a. Diadromous fish migrate between fresh and salt water
1. Anadromus are saltwater fish that migrate to fresh to breed
2. Catadromous are freshwater fish that migrate to salt to breed
3. Amphidromous are either that change locale for other reasons
b. Potamadromous fish stay in freshwater their entire life
c. Oceanodromous fish say in saltweater their entire life
E. BENTHOS (bottom-dwellers, benthos = bottom)
i. They live in or on the ocean floor
a. Epifauna live on the surface of the ocean floor, attached to rock or moving along
b. Infauna live buried in the surface of the ocean floor
ii. Nektobenthos live on the bottom, but also swim or crawl through the water above
iii. HYDROTHERMAL VENT BIOCOMMUNITIES
a. Very, very bottom of the ocean around hydrothermal vents
IV.
ADAPTATIONS OF ORGANISMS TO THE MARINE ENVIRONMENT
A. ORGANISM SIZE
i. Phytoplankton need to stay close to the surface to be able to get radiation
ii. They can’t propel themselves, so they have to create more frictional resistance
iii. This primarily depends on surface area to volume ratio
iv. By being smaller and having a higher relative surface area, there is much more frictional
resisitance
v. Diatoms (an important phytoplankton) have all kinds of appendages sometimes
a. Especially in warmer waters
vi. Oil droplets are even created by some phytoplankton
a. lowers overall density
b. increases buoyancy
B. STREAMLINING
i. There is friction involved in moving through the water
ii. Especially with an increase in size for nekton, that’s more energy needed
iii. Reducing drag is the best option to conserve energy
iv. A streamlined body does not create eddies (the wake)
C. TEMPERATURE
i. Plankton are physically smaller (less volume) in warmer waters than in colder waters
ii. Warm-water species have more ornate appendages to increase surface area to prevent
it from sinking (relation to the viscosity of water)
iii. Warmer temperatures increase biological activity
a. Tropical organisms grow faster, have a shorter life expectancy and reproduce
earlier and more frequently than those in colder waters
iv. There are more species in warmer waters, but much more biomass in colder climates
v. Stenothermal organisms can only withstand a very small temperature range
a. Steno = narrow
vi. Eurythermal organisms can withstand large and abrupt changes in temperature
a. Eury = Broad
D. SALINITY
i. Some organisms need to adapt to handle changes in salinity
a. Tides force salty water in river mouths, and then draws it out again
ii. Stenohaline organisms can only withstand a very small salinity range
iii. Euryhaline organisms can withstand large and abrupt changes in salinity
iv. EXTRACTION OF SALINITY COMPONENTS
a. Some organisms can extract minerals from ocean water
1. Phytoplankton (including diatoms) and microscopic protozoans
(e.g. radiolarians & silicoflagellates) extract silica
2. Coccolthiophores, foraminifers, most mollusks, corals and some
algae extract calcium carbonate
v. DIFFUSION
a. Diffusion is the movement of molecules from an area of high concentration (of
said molecule) to one of low until uniformity is met (equilibrium)
b. This is the main process by which cells take in nutrients and expel waste
vi. OSMOSIS
a. Osmosis is the movement of WATER molecules from an area of low salinity (of
some other constituent) to one of high salinity until uniformity is met
1. Hypotonic – low salinity
2. Hypertonic – high salinity
3. Isotonic – equal salinity
vii. OSMOTIC PRESSURE
a. The pressure that must be applied to the higher concentration to prevent any
water passing into it
b. If seawater has a lower salinity than the fluids in a fish, water will flow into the
fish, meaning the fish is hypertonic
1. These fish do not drink
2. Cells absorb salt
3. Large volume of dilute urine
4. These are FRESHWATER fish
c. If seawater has a higher salinity than the fluids in a fish, water will flow out of the
fish, meaning the fish is hypotonic
1. Drink large amounts of water
2. Secrete salt through special glands
3. Small volume of concentrated urine
4. These are SALTWATER (MARINE) fish
E. DISSOLVED GASES
i. Cold water can dissolve more gases than warm water
ii. Most organisms in the water must extract dissolved gases from the water
a. Carbon Dioxide for photosynthesis
b. Oxygen for metabolism
iii. Gills are specially designed fibrous respiratory organs
iv. Gill structure and location vary
v. Most need 4.0 ppm of Oxygen
F. WATER’s HIGH TRANSPARENCY
i. The Euphotic zone is about 1000 m deep in the open ocean
ii. Many marine species have awesome eyes
iii. Jellies are nearly transparent to help counteract
iv. Some organisms camouflage themselves
v. Some organisms use countershading
vi. Some migrate vertically to avoid detection
vii. Some organisms use disruptive coloring
G. PRESSURE
i. To combat the pressure, especially far down, some organisms do not have lungs, ear
canals or other possible air passageways
V.
DIVISIONS OF THE MARINE ENVIRONMENT
A. PELAGIC (OPEN SEA)
i. The pelagic realm is divided into biozones
ii. There are 2 main horizontal divisions
a. Neritic Province (from high tide until a depth of 200 m)
1. Mainly the continental shelf
b. Ocean Province (after a depth of 200 m)
iii. There are 3 main vertical divisions based on light availability
a. Euphotic Zone (until light still exists for photosynthesis)
1. Rarely deeper than 100 m
b. Disphotic Zone (light is small, but measurable)
1. Usually until 1000 m
2. End of Mesopelagic Zone
c. Aphotic Zone (no light)
1. 1000 m and below
iv. There are 4 main vertical divisions based on depths
a. Epipelagic Zone (until a depth of 200 m)
b. Mesopelagic Zone (until a depth of 1000 m)
c. Bathypelagic Zone (until a depth of 4000 m)
d. Abyssopelagic Zone (below 4000 m)
v. EPIPELAGIC ZONE
a. The upper half includes the Euphotic Zone, where photosynthesis occurs
b. The level of dissolved oxygen begins to decrease rapidly here
vi. MESOPELAGIC ZONE
a. This contains the oxygen minimum layer
1. 700 – 1000 m
2. Oxygen is used up at lower depths
3. Oxygen is replenished by deep sea cold currents
b. Species usually have large eyes to detect light levels
c. Bioluminescent organisms live here
1. Photophores are glandular cells that often contain luminous
bacteria surrounded by dark pigments
2. Luciferin reacts with luciferase
vii. BATHYPELAGIC AND ABYSSOPELAGIC ZONE
a. Both of these exist in the aphotic zone
b. 75% of all living space
c. Organisms are typically small and bizarre-looking
d. Detritus is common
B. BENTHIC (SEA BOTTOM)
i. There are two main horizontal parts that correspond: subneritic & suboceanic
ii. Before the subneritic province, you have the Supralittoral zone
a. It’s above the Spring high tide line
b. Commonly called the “spray zone”
c. Only covered in water in rare circumstances
iii. SUBNERITIC
a. LITTORAL ZONE
1. This coincides with the intertidal zone
2. It exists between high & low tide
b. SUBLITTORAL ZONE
1. This is the shallow subtidal zone
2. It extends from low-tide shoreline until 200 m depth
3. It consists of inner and outer regions
a) The INNER sublittoral zone extends until marine algae no
longer grow attached to ocean bottom
b) The OUTER sublittoral zone extends until 200 m depth
c. BATHYAL ZONE
1. This extends until about 4000 m depth
2. Typically corresponds with continental slope
d. ABYSSAL ZONE
1. This extends until about 6000 m depth
2. Over 80% of benthic environment
e. HADAL ZONE
1. This extends below 6000 m depth
2. Only deep trenches along margins of continents
3. Isolated organisms, so unique adaptations