Garrison Bay

Garrison Bay

gbbig Aerial view of Garrison Bay (© Washington Dept. of Ecology)

Garrison Bay, located on the west side of San Juan Island, was named after the military camp established by the British following the Pig War eruption in 1860. The bay is characterized by muddy substrate, which is overlain by a thick diatomaceous layer close to the shoreline. Coarse shell material is abundant within the mud, along with numerous boulder-size rocks. Both the shells and rocks provide microhabitats for many organisms found in the bay, including polychaetes, crabs, nudibranchs, brittlestars, bryozoans, limpets, anemones, chitons, sponges, and gastropod egg masses.

Team Mud (Paul Harnik, Katherine Nicholson, Krisha Tracy, and Susan Wang) spent four low tides characterizing unique aspects of Garrison Bay's physical biology and faunal diversity. Our objectives at Garrison Bay were to:

Using an onshore - offshore transect , characterize the environmental gradient through the intertidal by

recording temperature variation at the surface and within the sediment, and

characterizing the relationships between the surficial shell abundance, large and small burrows, and the percentage of coarse material found in the muddy substrate

Characterize microhabitats and the marine invertebrate fauna of Garrison Bay by

compiling a species list using mud cores and surface observations and

quantifying faunal variation in three ways,

recording abundance in quadrats along the onshore-offshore transect

observing surficial frequency of target fauna (Tresus capax, Metridium sea anemones Melanochlamys and Haminoea bubble snails) along two transects parallel to the shoreline

comparing fauna in open mud to that associated with dead shell microhabitats

Document invertebrate adaptations for life in this habitat, focusing on

Locomotion

Reproduction

Feeding

Protection

Team Mud gives special thanks to the Howe family for allowing us generous access to the intertidal through their property.

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