Honors Marine Biology

Module 9Intertidal Zones

January 17, 2013

Class Challenge

Birding Field Trip

The CeleryFields

Make up Field Trips

Intertidal Zone

The Area of Shoreline between high and low tides. Also known at Littoral Zone.

This coastal strip where the land meets the sea is by far the smallest area in all the world’s marine environments, yet more is known about it than any other.

Intertidal Zone

• This is a narrow strip of land that is only a few meters in width, and it is defined as the area between the oceans’ high tide and low tides.

• Although it is small, it is the most accessible place to scientists, and is therefore the most studied marine habitat.

Littoral Zone or Intertidal Zone

• Even though this zone is small, it has the greatest variation of environmental factors as compared to any other marine ecosystem.

• There are even several differences within a single square meter containing huge diversities of life.

Intertidal Communities

As the tides rise and fall, covering and then exposing areas along the coast we can observe the dramatic changes in the environmental conditions.

• Most intertidal plants and animals experience a time of stress during low tide.

• They are exposed to the air, which may be hot or freezing.

• If it rains, these marine organisms will be exposed to an overabundance of fresh water.

Also, the exposure provides an opportunity

for land predators, such as birds and rodents to move in.

At high tide, the area returns to an aquatic

environment. This brings moderate temperatures and high salinity levels, and it also replenishes nutrients and dissolved gases necessary to many of the creatures that live in the intertidal zone.

During High Tide

Waves and surf return to the intertidal zone. Wave movement can wash away organisms that do not have the ability to either hang onto the rocky surface or burrow into the sand.

The waves can also push rocks and debris onto organisms crushing them.

• Waves can also be beneficial to organisms.

• Waves bring nutrients, carry off reproductive cells and accumulated wastes.

• Wave energy shifts soft sediments and shapes the shoreline.

• Waves constantly remove fine sediments from rocky shores, resulting in a hard bottom, and wash away; fine materials from beaches, leaving only grains of sand. These finer materials will be washed out to sea and deposited in more protected bays and lagoons.

Substrate

Is the bottom surface of a marine habitat.

It is the type of material located on the bottom and provides the basic habitat and determines what organisms can live there.

A soft sandy substrate produces a different type of environment than a hard, rocky substrate.

The variety of tidal conditions, bottom types, and wave strengths create different living conditions for the organisms living there.

Rocky Intertidal Zones

• This is a harsh area for organisms to live.

• Rock boring sea urchins and clams, burrow into the rocks so that they are not swept away by the waves.

• Most organisms just hang on tightly to the rock.

Epifauna

Animals that hold on to the surface of a substrate, including sand or mud, are called epifauna.

They either crawl about the sea bottom or sit firmly attached to it.

When an epifaunal organism is attached to a substrate, it is referred to as sessile.

Rocky Intertidal Abiotic Conditions

Air, Temperature and Salinity

Desiccated : A term referring to an organism that has lost its body moisture.

In order to survive, creatures must be able to either endure the dry time or have a mechanism to counter it.

Organisms hiding under rocks and crevices and where water is pooled. (Tidal Pools)

• Some organisms are able to protect themselves against desiccation by capturing or sealing in moisture.

• These organisms have shells or other protective coverings to trap the moisture. See page 214

• Besides becoming desiccated, intertidal organisms face challenges of temperature and salinity fluctuations.

Wave Action

• See figure 9.4 on page 216

• Figure 9.5 on page 217

Zonation

One of the most striking features in an intertidal area is the noticeable horizontal bands of organisms exposed at low tide.

These bands can be seen on rocky shores nearly everywhere in the world.

The bands are made up of similar organisms located at a specific height are not typically found anywhere else in the ecosystem.

Vertical Zonation

• is defined at the noticeable horizontal bands of organisms living within a certain range in the intertidal zone.

3 Major Zones of the Rocky Intertidal

• Upper intertidal- sometime called the splash zone, because it rarely is covered with water.

• Middle intertidal – is filled with an abundance of species. This area is regularly covered and uncovered with the tides. Great quantity of Algae.

• Lower intertidal – is an area that is underwater most of the time. This allows slow moving predators such as sea stars and snails to almost constantly feed. This zone contains the largest diversity of organisms.

• See figure 9.7 page 220. Page 226 summary

YouTube• BBC: Race against the tide, Risking death

against huge blocks of ice.• http://youtu.be/Z0qGvC3vqaA

• http://youtu.be/u64ppKBY3cM

• http://youtu.be/renpnyTX-mc

• Intertidal Zones• http://youtu.be/g7Rlh5sA8WE

Lab: Intertidal Zone Organism Identification and Classification

Observations: Specimen found and ZoneSea Squirt: Upper and lower zoneAlgae: Upper, middle and lowerShrimp: middle and lowerBlue Crab: middle and lowerJuvenile lobster: lowerMud crab: middle and lowerSpider crab (male): middle and lowerMinnows: lowerSand flea: amphipod upper – attached to sea grassPike fish: lowerLightening Welk: lowerAscidian: upper attached to wall or rocksStone crab: middle and lowerPistol Shrimp middle and lowerArrow Shrimp middle and lowerHermit crab middle and lowerMussels middle and lower

Homework

• Finish reading Module 9 to page 232• OYO Questions 9.13 – 9.17• Study Guide: Define e-h and 19-28• Finish lab• Class challenge• Quiz: Rocky Intertidal Zones: See OYO

question 9.11 and 9.12; Abiotic Conditions of Intertidal zones. Be able to name 15 different species living in the Intertidal Zone