I’m a conservation land manager at the Port of San Diego in California. My team and I aim to manage the tidelands around San Diego Bay, an area of more than 4,850 hectares, three-quarters of which is covered by water at high tide. At least 60% of the bay’s shoreline is ‘hardened’ — that is, it is edged with either a solid seawall or rip rap, piles of artificial boulders.
To prevent erosion of the adjacent natural shoreline and restore wetlands, we’re participating in the San Diego Bay Native Oyster Living Shoreline project. As part of that, in December 2021, we placed 360 reef balls — depicted in this photograph from September this year — along 260 metres of shoreline to form the foundation of a native-oyster reef in the south bay. Here, I’m looking for oysters that have settled and are growing on the spheres.
The reef balls are made out of ‘baycrete’, a concrete mixture made with local sand and the shells of farmed oysters. These attract wild oysters, which come to live there. We’re targeting the native Olympia oysters (Ostrea lurida), which can filter up to 190 litres of water per day. And sediment should accumulate behind the reef balls, encouraging the growth of eelgrass (Zostera marina). The grass is the foundation of the bay’s food chain.
In a couple of years, native oysters will cover the reef balls, forming an artificial reef offshore. This reef will cause storm waves to break farther from the shoreline, protecting the adjacent salt marsh. Just inland from this area is a wetlands habitat refuge for the endangered California least tern (Sternula antillarum browni), and many birds are already hopping onto the reef balls and eating what’s living there.
Living shorelines are an important part of sequestering carbon to combat climate change — both eelgrass and oysters store a lot of carbon. The reef balls are win–win–win. I often joke that we’re trying to save the planet one acre (0.4 hectares) at a time.
Source: Ecology - nature.com
