Hide and Seek on a Coral ReefLatest update June 7, 2019 Started on June 7, 2019
Fish love to hide inside the complex architecture that corals build. But on many reefs, corals are being replaced by more tolerant organisms, including sponges. Can soft-and-wobbly sponges provide a safe habitat for fish on future reefs?
From water pollution to global ocean warming, reef-building corals are facing a suite of pressures that are transforming the face of tropical reefs worldwide. On changing Caribbean reefs, more tolerant organisms such as sponges are gaining ground, often replacing corals. But can sponges also replace the complex architecture that corals build to house thousands of species of reef-dwellers worldwide?
Previous research has shown that in deep waters, and in environments where sand would dominate if it wasn't for sponges, sponges do provide habitat to fishes. But we simply don't know enough about the relationship between sponges and fish on shallow, tropical coral reefs.
Sponges form soft structures that often lack the intricate nooks and crannies of the coral framework where reef fish hide. If reef fish potentially have less space to live, grow and reproduce, their already decreased populations might suffer further losses, with critical downstream effects for the food chain of reef ecosystems. Not to mention the effects for fisheries and food security of local communities and beyond.
So our mission is to shed light on the potential of sponges to provide refuge and shelter to Caribbean fishes. First we will describe the 'architectural complexity' of sponges and corals. That is, we will use underwater photography to create 3D models of different coral and sponge species, and based on these models we will evaluate how much hiding space each organism offers. Then we will film these organisms on the reef for extended periods of time to quantify the size, numbers and diversity of fishes associated with sponges, in comparison to corals.
We have chosen to do this study on the coral reefs of Curaçao in the southern Caribbean. Curaçao is a young island nation formerly part of the Netherlands Antilles. Compared to elsewhere in the region, many reefs here are relatively healthy, with a decent coral cover. And they are also rich in sponges!
A collaboration between the Caribbean Research and Management of Biodiversity Foundation (CARMABI) on the island, and the California Academy of Sciences (CAS) in San Francisco, our project will kick off later this year. For now, we will dive into field work planning and logistics, but we invite you to stay tuned as our project unfolds!
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