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 ZONESOcean 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 life-forms, 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.