Download Chap 3 marine zones

Chapter 3:
MARINE ENVIRONMENTS
Marine Environments – Physical Settings
• Every marine environment has living (biological)
and nonliving (physical and chemical)
components
• The living (biotic) components are called “biota”
and include algae, fish, sponges, bacteria, etc.
• The nonliving (abiotic) components include
water chemistry, light, salinity, pressure,
density, etc.
Marine Environments…
• Several different classification systems exist for
dividing the ocean into sections…the system
used depends on the purpose
– Oceanographers use a different set of terms than
marine biologists would use.
Marine Environments…the physical setting
Continental Crust = mostly granite, thicker and
less dense than ocean crust
Oceanic Crust = mostly basalt, thinner and more
dense, so usually sinks below the continents
Continental Shelf = the relatively shallow part of
the seafloor that adjoins the continents
Continental Slope = the area where the seafloor drops
steeply at the outer edge of the continental shelf
Continental Rise = the accumulation of mudslide
sediments at the base of a slope
Continental rise
Marine Environments…the physical setting
Marine Life Zones
• A life zone is a region that contains
characteristic organisms that interact with one
another and with their environment.
Marine Life Zones
• The majority of life in the oceans occurs near
the coastlines, in relatively shallow areas above
the continental shelf!
• Why do you think this is?
Major Life ZONES
Ocean life zones are based on differences in physical
conditions such as…
• Light
• Salinity
• Exposure to moisture
• Pressure
• Temperature
Remember
• Living things evolve to survive in their
surroundings
The Life Zones
• Photic – The part of the ocean where light
penetrates (up to 200 m deep)
• Aphotic – Below 200 m. Receives no sunlight;
always dark
1. Life Zones of the Continental Shelf
• Supratidal – Above the high tide line, receives
only “wave spray”
• Intertidal – Area between high and low tide;
sometimes dry, sometimes wet
• Subtidal – Area just past low tide level, always
under water (often barely)
• Benthic – The whole ocean floor
2. Open Ocean Life Zones…
• Pelagic – Entire ocean of water past intertidal
zone
• Neritic- Part of the pelagic zone directly above
the continental shelf.
• Oceanic- Part of the pelagic zone past the shelf
(deep ocean water)
• Benthic – The whole ocean floor
– Note: benthic refers to any area of the ocean floor,
so it is everywhere the ocean is!
Supratidal Zone
• The supratidal zone
receives only sea spray
from the crashing waves
• Salt spray limits the
growth of plants in the
lower supratidal areas,
so grasses, shrubs, and
trees only grow in the
mid to upper supratidal
areas.
The Intertidal Zone
• The intertidal zone is the area located
between high tide and low tide.
– High tide is marked by the strandline, a long line of
seaweed and debris deposited on the beach during
each high tide
• Organisms that live in the intertidal zone are
specifically adapted to meeting the challenges
of living in an area that has alternating periods
of wet and dry, as the tides come in and go out
each day
Intertidal Zone
• Adaptations of organisms
include ability to burrow,
ability to hide in shell, cling to
surfaces, store water in the
body for long periods of time,
excrete excess salt, etc.
• Beach fleas live in the
seaweed of the strandline, in
the upper intertidal area
• Crabs can burrow into the
sand…snails can protect
themselves from drying out
or being preyed upon by
hiding in shells
Subtidal Zone
• The subtidal zone is the area below the low tide line at all
times….always submerged under water but often experiencing
turbulent conditions due to crashing waves
• Organisms living in the subtidal zone need the ability to cling to
surfaces or else they will be washed away by the wave impact
associated with tides
• Barnacles secrete a glue that allows them to literally attaches
themselves to a substrate (rocks, other plants, objects in water,
etc)
• Mussels secrete a tough, fibrous byssal thread that is used to
attach their bodies to a substrate
• Marine algae (kelp, for example) have a feature called a
holdfast, a fibrous pad of tissue used to adhere to rocky
surfaces
Subtidal Zone
• Many organisms living in the subtidal zone
possess flattened bodies to minimize wave
impact
– Some, like the flounder can bury themselves in the
sand to avoid predation
– Sand dollars use their tube feet to inch along the
seafloor and feed on algae
– Clams, crabs, snails, worms, and shrimp are also
abundant in the subtidal area, and become food for
fish that move in during high tide.
What do you see????
Pelagic Zone
• The pelagic zone is the open ocean, from the
areas above the continental shelf out to the
deepest parts of the ocean.
• The pelagic zone is divided into two
subsections, called Neritic and Oceanic.
– Neritic Zone = the area of shallow ocean waters
(less than 200m in depth), past the intertidal zone,
above the continental shelf
– Oceanic Zone = the deeper parts of the ocean
(more than 200m depth), beyond the neritic zone
Neritic Zone
• The neritic zone receives plenty of nutrients from
rivers emptying into the ocean near coastlines, and
the mixing caused by tides and currents.
• Sunlight is able to penetrate throughout the neritic
zone, leading to a very productive ecosystem, with
algae, phytoplankton, and marine plants serving as
the base of the food web.
• Most “deep-sea” fishing actually occurs in the neritic
zone, where waters are less than 200m deep
– Most of the world’s commercial fishing takes place here!
Oceanic Zone
• The upper part of the oceanic zone receives
light, whereas the lower part (most of the
ocean) is in darkness.
• Although there are fewer communities of
organisms in the aphotic zone, numerous lifeforms, such as fish, worms, squid, and
crustaceans, have been observed and
photographed in the great depths of the ocean.
• Deep-sea organisms are specially adapted to
live in the depths of the aphotic zone.
Oceanic Zone (Deep Sea) Adaptations
• The anglerfish is
adapted to live in the
deep ocean because it
possesses a huge
mouth and long sharp
teeth to help it catch
prey in the darkness.
– It even has a lure over
its mouth that glows in
the dark, making it
possible for the fish to
see and attract prey.
Oceanic Zone (Deep Sea) Adaptations
• Other deep-sea fishes
(such as the viperfish),
have mouths that are
pointed upward, which
helps them catch the
scraps of food that fall
from shallower waters.
Ocean Basin
• The deepest part of the ocean floor is called the
ocean basin or the abyssal plain
• The benthos (bottom-dwelling organisms) that
live in the ocean basin are adapted to regions
of very low temperatures and very high
pressure.
Fig. 13-21, p. 367
Epipelagic Zone
• Epipelagic Zone - Extends from the surface to
200 meters (656 feet). It is also known as the
sunlight zone because this is where most of the
visible light exists. With the light come heat.
This heat is responsible for the wide range of
temperatures that occur in this zone.
Mesopelagic Zone
Mesopelagic Zone - Below the epipelagic
zone extending from 200 meters (656 feet)
to 1000 meters (3281 feet). The
Mesopelagic zone is sometimes referred to
as the twilight zone or the midwater zone.
The light that penetrates to this depth is
extremely faint. It is in this zone that we
begin to see the twinkling lights of
bioluminescent creatures. A great diversity
of strange and bizarre fishes can be found
here.
Bathypelagic Zone
• Bathypelagic Zone - It is sometimes referred to as
the midnight zone or the dark zone. This zone extends
from 1000 meters (3281 feet) down to 4000 meters
(13,124 feet). Here the only visible light is that
produced by the creatures themselves. The water
pressure at this depth is immense, reaching 5,850
pounds per square inch. In spite of the pressure, a
surprisingly large number of creatures can be found
here. Sperm whales can dive down to this level in
search of food. Most of the animals that live at these
depths are black or red in color due to the lack of light.
Abyssopelagic Zone
• Abyssopelagic Zone - Also known as the abyssal
zone or simply as the abyss. It extends from 4000
meters (13,124 feet) to 6000 meters (19,686 feet). The
name comes from a Greek word meaning "no bottom".
The water temperature is near freezing, and there is
no light at all. Very few creatures can be found at
these crushing depths. Most of these are invertebrates
such as basket stars and tiny squids. Three-quarters
of the ocean floor lies within this zone. The deepest
fish ever discovered was found in the Puerto Rico
Trench at a depth of 27,460 feet (8,372 meters).
Hadalpelagic Zone
• Hadalpelagic Zone - This layer extends from 6000
meters (19,686 feet) to the bottom of the deepest
parts of the ocean. These areas are mostly found in
deep water trenches and canyons. The deepest point
in the ocean is located in the Mariana Trench off the
coast of Japan at 35,797 feet (10,911 meters). The
temperature of the water is just above freezing, and
the pressure is an incredible eight tons per square
inch. That is approximately the weight of 48 Boeing
747 jets. In spite of the pressure and temperature, life
can still be found here. Invertebrates such as starfish
and tube worms can thrive at these depths.