MSCI 340 - Hard Bottomed Habitats Overview

The kelp forest segment of the MSCI340 content

Where can we find hard bottom habitats?

Practically everywhere in the ocean. From coastlines to deep sea, from the equator to both of the poles.

What are hard bottom habitats?

Primary geological features of the ocean. Not influenced by biogeography.

Describe where the littoral zone is located

An area located between the supralittoral (high tide) and sublittoral (low tide) zones. Typically extends from the shoreline to the continental shelf.

Describe where the infralittoral zone is located

An area located between the sublittoral (low tide) and lower infralittoral zone. Typically extends beyond the continental shelf where light is still available for photosynthesis.

Define the infralittoral zone, what part of the intertidal system is it part of?

A shallow zone in the subtidal zone dominated by macroalgae extending as far as enough light is sufficient for photosynthesis

What would you typically find in the infralittoral zone?

String seaweeds, grazers, and kelp

Describe where the circalittoral zone is located

An area that can be found beyond the lower infralittoral zone. There is not enough light for photosynthesis to be possible.

Define the circalittoral zone, what part of the intertidal system is it part of?

A region below the infralittoral zone dominated by invertebrates (sessile and mobile). There is no macroalgae due to the lack of sunlight.

What would you typically find in the circalittoral zone?

filter feeders

Describe an important factor affecting hard bottom habitats on a small-scale community structure

Slope can affect hard bottom habitats on a small-scale community structure

Define slope (in terms of MSCI 340)

Slope is the angle of the substrate, which fundamentally determines the community structure of hard bottomed habitats

What are the three types of slope.

Identify whether each of these slope types is “macroalgae dominant“, “diverse”, and “epifaunal dominant”.

Flat - “macroalgae dominant”

Sloped - “diverse”

Vertical - “epifaunal dominant”

Describe an epifaunal organism

An organism that lives on the surface of the substrate

Describe an infaunal organism

An organism that lives in the substrate

What is the MAIN determinant of species composition at different slopes?

light availaibility

What are the other determinants of species composition at different slopes?

water flow, flow availability, water temperature

Describe the relationship between slope and light availability

As the slope changes, the light level changes

Describe an important factor affecting hard bottom habitats on a medium-scale community structure

Water supply can affect hard bottom habitats on a small-scale community structure

Why is water supply important for hard bottom habitats?

Water supply determines the density, salinity, available nutrients, and water flow in a given area.

What are the three variables that stratify the water layers?

Temperature, salinity, and density

Define a seamount

An inactive underwater volcano that extends from the seafloor to the water column.

How do seamounts interact with the water column

They create hard-bottomed habitats, coming into contact with the flow of water masses

What makes seamounts significant for marine ecology?

They are the only phenomenon on Earth where hard substrates interact with the water column without being part of the continental shelf.

Seamounts also facilitate connectivity between the mainland and the island

What’s a seamount that we have off the coast of Monterey

Davidson’s Seamount

How can humans influence the rocky bottoms?

Shipping containers can fall off cargo ships, creating artificial rocky bottoms. They also become an artificial form of connectivity between the mainland and islands.

Name the five abiotic disturbances at the rocky bottoms

temperature, storm surge, earthquake, swells, iceberg scours

How do the influences of abiotic disturbances decrease with water depth?

An example can be wave orbitals, which decrease with depth. This reflects the effectiveness of storm penetration to the sediment below.

What are two biotic disturbances at the rocky bottoms?

Predation and competition

Describe how predation varies with water depth

This disturbance varies a lot with depth. Consumer activity is more limited in shallow areas and the variation in predation risk changes with water movement

Describe how competition varies with water depth

This disturbance varies less with depth (not including light penetration). Space is a main resource for competition.

What is an example of competition with space in context of rocky bottom habitats?

Horizontal slopes will produce more competition for space, as different organisms compete for different attributes of the seafloor space