As we say hello to 2015, we also wrap up our first year monitoring our oyster reef on the Point Pinole Shoreline. We’ve found some great things!
First, and most important, we found our native Olympia oysters! These crusty creatures were the impetus for the reef project, and we are happy to report that they have found their new habitat and are settling in nicely. They are present by the hundreds on the reef balls, and they have grown an average of 220% since August–that means they have more than tripled their body size in just four months!
Olympia oysters are smaller than the Pacific oysters that we commonly think of (and eat), so these young bivalves are still pretty small: about a third of an inch in length. They can expect to get a few inches bigger before they’re fully grown.
Oyster larvae are only motile for a short time before they pick a spot and settle down. They need a hard surface to attach to, such as a rock or the shells of adult oysters. The sediment that washed down into the bay during the gold mining days covered up many of the habitable spots, and now hard surfaces are at a premium. The oyster reef balls, made of bay sand, oyster shell and concrete, provide nice hard spots for oysters to settle down and get to their life’s work: filtering water. As filter feeders, Olympia oysters strain their food from the water, filtering about 50 gallons of water per day and doing their part to keep the bay clean and healthy.
Our other reef inhabitants are barnacles. They are also filter feeders, but they have a specialized skill set: while oysters and most other filter feeders internally filter water, barnacles actually reach out of the shelter of their shells with long, feathery limbs and grab food particles from the water. Smaller than oysters, barnacles tend to grow on any hard substrate they can find, up to and including marine animals such as whales.
Oysters and barnacles tend to be among the first colonizers of new spaces in the marine world. They can weather harsh environments and end up creating more suitable habitat for many other life forms, including nudibranchs, crabs, and even small fish. This community is not always a welcome addition: for example, presence of these “fouling organisms” on boat hulls can create so much drag in the water that fuel efficiency drops, sometimes drastically. However, to us this community of hardy invertebrates communicates a healthy and prosperous bay.
We witnessed another magic moment that brought home the fact that the reef is fulfilling its purpose. It came in the form of a beautiful bird, near sundown, on a stormy December day: a Great Egret was spied fishing amongst the reef balls, a sure sign that life is moving into the reef.
If you’re interested in learning more and volunteering to monitor the reef, please contact Helen Dickson (firstname.lastname@example.org).