Starfish Gallactica Intertidal Work at MacKerricher



Field Trip

Mackerricher State Park at Laguna Point

Frank McGarvey, Tereise Van Wyhe and on loan from the Ecology Chicks - Cathy Lawrence

Question asked: What species can be found in a random one meter square area in the Zone IV tidal zone?

  1. The Starfish group member stood in an area identified as a Zone IV tidal zone. This zone was identified by the presence of eelgrass attached to the rocks.
  2. One of the group members faced away from the ocean and threw an easily identified, colorful rock over their shoulder, toward the ocean.
  3. The other group members watched the rock, went to the location it landed and centered the one foot square wood frame on the rock.
  4. The group spent the next 20 minutes identifying the presence of various species within the one foot square.

Information about the location:
  • Time: 1522 local time
  • Weather: High fog. Air temperature was perceived by group member to be cool to cold requiring a light coat for comfort. Light Breeze estimated to be less than 5 knots.
  • Tides: -0.3 feet at 1653 predicted for nearby Fort Bragg landing at the website.
  • Description of area observed: area was entirely underwater - 3 to 6 centermeters in depth. The area was part of a small tidal pool approximately one square meter in size. The bottom was covered in rocks ranging in size from two millimeters to 12 centimeters. Between and underneath the rocks were shell fragments from indeterminate shells.
  • Given our group did not have access to a quadrant we used a one foot square wooden frame. Number of objects are multiplied times nine giving us one yard square or a little less than one meter square which was the area we were instructed to survey.
  • All lengths are estimates.

Number of objects
Range in sized of objects
color of objects
Where found
Black Turban Snail
23-33 mm
Attached to rocks and slowly moving accross the surface
Red Algae
Colonies of small algae covering protions of rocks
reddish brown
attached to rocks of several sizes
Pink Coral algae
Entire plants 30-40 mm in diameter
light pink
growing out from underneath rocks
Spiny Leaf Algae
60 mm in length
Growing between rocks
Hermit crabs
Approximately 40 mm accross
Shells inhabited were black
Scampering about the area
Green anemone
50-70 mm in diameter
brownish green
In crevices of larger rocks
9 clumps of approx . 15 leaves each
Leaves 80-100 mm in length
dark green
crevice of two larger rocks
Horned snail
25 mm
black to brown
slowly moving accross the bottom of the tide pool
Unidentified small crabs
2-3 mm accross
off white
moving about the pool

Additional observations by the group members:

  • This was the best field trip so far.
  • We were thankful that no one was seriously hurt on the slippery rocks.
  • Everyone was very helpful and friendly which made the day very enjoyable.
  • The day was far too short.