Lesson 21:

Marine Ecosystems

Marine Ecology

Life in the marine environment

We’ve learned a lot about the biology of different types of marine organisms

In marine science, it is important to understand why these creatures live where they do and how they interact with their environment

Today we will learn about marine ecology: the study of the relationship of marine organisms with each other and with the environment

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Life in the marine environment

The ocean can be divided into zones based on depth (vertically) and distance from land (horizontally)

Different zones of the ocean have conditions that support different organisms

What is an ecosystem?

An ecosystem is a physically distinct area that contains a community of interacting organisms3

Ocean zones and continental margins

Many ocean zones are defined based on continental margins. To help you understand ocean zones, let’s first review

continental Margins: Continental Margin: Submerged area of continents. Include:

– Continental Shelf (flat gradually sloping seafloor) from shoreline to ~ 200m; End of Shelf is called the Shelf Break

– Continental Slope (steeply sloping seafloor) seaward of shelf break– Continental Rise (Moderately sloping seafloor) seaward of slope

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Pelagic and benthic zones

One simple ocean zone classification is between the water and the ocean floor

The water is referred to as the pelagic zone

– Organisms that swim through the water column are known as nekton

The ocean floor is referred to as the benthic zone

– Organisms that live here are benthic organisms or benthos

Photos: NOAA

Shark: Pelagic (nekton)

Crab: Benthic (benthos)5

Pelagic and benthic zone divisions

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Pelagic zone divisions (depth from surface)

Benthic zone divisions(seafloor zones)

Supralittoral –shore above high tide

Epipelagic (0-200m) Littoral – the intertidal zone (sometimes submerged and sometimes above water)

Mesopelagic (200-1,000m) Sublittoral – seafloor of the continental shelf (from low tide to the shelf break)

Bathypelagic (1,000-4,000m) Bathyl – seafloor of the continental slope to the deep ocean bottom

Abyssopelagic (4,000-6,000m Abyssal – deep ocean bottom between the base of the slope and 6,000 m

Hadalpelagic (6,000-10,000m) Hadal – the deepest zone, below 6,000m

Pelagic and benthic zone divisions

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PelagiczoneB

enthic zone

LittoralBathyl

Abyssal

Hadal

high tide

epipelagic

bathylpelagic

abyssa

lpelagic

hadalpelagic

200m

1,000m

4,000m

6,000m

Low tide

mesopelagic

Species evolve traits that help them survive in their environment

Species in different environments may evolve different lifestyles, behaviors and physical traits

Do you remember a few ways that intertidal organisms are adapted to their relatively harsh environment?

Species usually are not completely isolated from one another, but interact with other species that live in a shared environment

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Populations of different species interacting with one another in a shared environment form a community

An ecosystem is a distinct physical entity with unique abiotic (nonliving) conditions that is home to a community of interacting species

Can you think of some marine ecosystems you have learned about in earlier lessons, classes or elsewhere?

Intertidal (Splash zone)

Coral Reef Beach

What is an ecosystem?

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Energy is transferred through ecosystems

Solar energy is converted to chemicalenergy by autotrophs

Primary consumers eat primary producers to get energy

Secondaryconsumers eat primary consumers to get energy

Photos: NOAA10

Life in ecosystems is interconnected

As you’ve probably already realized, the marine environment consists of many distinct ecosystems that contain unique organisms

How do you think life within ecosystems is interconnected?

Marine organisms form relationships with one another and share space and resources

As a result, an impact on a single species in an ecosystem can affect many other species in the same ecosystem

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Important interactions

It is important to manage our natural resources in a way that reflects the interconnectedness of ecosystems and their components

Ecosystem-based management (EBM) is a management approach that includes these interactions instead of considering single species or single issues at a time

NOAA applies EBM in its management of marine resources

Management of ecosystems, like this bleached coral reef, requires looking beyond just the coral itself. Other important factors to study might include pollution, development, watershed management and interactions with other species.

Photo: NOAA

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Student activity: Ecosystem case study on an estuary

An estuary is a body of water that forms where freshwater from rivers and streams flows into the ocean and mixes with seawater to form a unique and productive ecosystem

One of our nation’s most valued ecosystems, the Chesapeake Bay, is an estuary– In fact, it is one of the largest estuaries in the world

In today’s exercise, you will analyze data about the blue crab to make inferences about the health of the Chesapeake Bay ecosystem

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