No. 03–The Realm of the Oyster

Oysters are builders. Each oyster builds its own home. In the intertidal regions they build colonies called oyster rakes. The ironic thing is that it is the very youngest of the species that are responsible for all new construction.

Oysters spawn from mid spring through summer by releasing sperm and eggs into the water. The fertilized eggs and hatching larva have neutral buoyancy which means they remain suspended in the water column. There are 4 larval stages over a period of a few weeks culminating in the post larval spat.

Lacking the buoyancy of its larval stages but having developed cilia which give it some mobility, the spat begins to settle to the bottom. This is a critical time in the life of the young oyster. It needs a hard surface to attach to if it is to survive. If it comes to rest in sand or mud and not able extricate itself it will die there.

If in the tumble of the tides the young oyster spat is fortunate enough to come into contact with a hard surface, it will chemically cement itself to that spot and begin to build its home. Even casual observation reveals that virtually any hard surface will serve. The most natural and widely available foundation surfaces are the shells of other oysters. Hence you will observe intertidal oysters of varying size cemented one on top of another in clusters.

Once secured to its foundation, the diminutive oyster begins home construction using the water borne mineral calcium carbonate as building material. As the body of the oyster grows, layer upon very thin layer of calcium carbonate are secreted to enlarge the shell incasing it. It is this continuous layering outward that is responsible for the perpetually sharp edge of the living oyster.

Oysters not only build homes for themselves, their cluster colonies also provide habitat for many other species far too numerous to list to here. Encrusting organisms form colonies of their own, countless microorganisms find shelter in the tiniest of fissures when the tide is running and swarm the rake on slack high water nourishing tube worms, barnacles and the filter feeding oysters themselves.

Small distant cousins of shrimp called amphipods dart about the superstructure of shell when the tide is in and shelter in the slurry and loose shell litter at its base when the tide is out. Oyster drill and banded tulip snails feed on small oysters and attach their egg cases, porcelain crabs scurry through the nooks and crannies when disturbed while at least three species of mud crabs hunt, scavenge and graze on algae.

Sub tidal oysters provide homes for others even in death. If it has not been destroyed by the predatory attack of a stone crab or had its hinge broken by a ravenous whelk, a dead oyster is quickly recycled by scavenging neighbors leaving a clean and empty shell.

The recently vacated one bedroom apartment will not be on the market very long. Any number of opportunists may vie for the unit before clear title is established through force of will. Small fish and crabs are most often the tenants of these previously owned dwellings.

The best method I have found for collecting blennies and gobies (species of small reclusive fish) for the Estuarium is to throw my cast net where I know there to be a scattering of unanchored oyster clusters small enough for my net to handle. Each cluster I bring to the surface is a treasure as I turn it in my hands and marvel at the small wonders of a very special world.