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The Endangered Corals of Fisher Island & The Saga of The Deep Dredge (Pt. 2 of 3)

Fisher Island Hybrid Fused-Staghorn Coral (Elkhorn Morphotype) pre-dredge/ mid-dredge health survey

The most remarkable aspect of the health of the corals growing on Fisher Island, is the success story of two hybrid fused-staghorn corals (Acropora prolifera) that live along its shorelines. The story of the first hybrid coral is well documented through the TEDxMIA talk Colin conducted in 2011. This hybrid coral appears to be much more palmate in its growth morphology which typically means that its mother was a staghorn and its father an elkhorn. This coral has proven to be the most remarkably resilient of the Fisher Island Acropora corals. While its growth has been somewhat slow, it has never demonstrated any evidence of significant die-off, white pox, or bleaching. It also features significant amounts of fluorescent green proteins which may confer it with an adaptive advantage over its non-fluorescent parent species.

However, there is another equally unusual hybrid fused-staghorn coral living on Fisher Island that we’ve also been observing since 2009. And it demonstrates a much more compact branching staghorn morphology, indicating that its mother was likely an elkhorn coral and its father a staghorn.

While we’ve watched this coral grow, die-back, and re-grow over the years, it has grown significantly in the past year of dredging. All of its branch tips are white, indicating that it is growing quickly. No signs of recent die-off are evident. Several years ago before the dredge, portions of this colony had died back as a result of competition with macroalgae which managed to grow between its tightly compacted branches and out compete it.

Fisher Island Hybrid Fused-Staghorn Coral (Staghorn Morphotype) pre-dredge/ mid-dredge health/growth survey

While the good health of both hybrid Acropora prolifera colonies during the Deep Dredge (as compared to the elkhorn corals) supports the hypothesis that their resilience can be attributed to their hybridity, they are still highly vulnerable to extirpation. Being singular colonies, they are still at the whim of sudden catastrophe. In order to increase the likelihood that these corals survive to be studied and cloned, it is important to aquaculture fragments of these corals in multiple locations, both in the wild and in the laboratory. Despite the fact that both of its parent species are listed on the Endangered Species List, Acropora prolifera is not conferred Federal protection due to the assumption that hybrid animals can’t reproduce. The upside to this illogical rule is that it actually makes research and grow-out of these hybrid corals in controlled environments much simpler, as it drastically reduces the amount of bureaucratic paperwork and permitting road-blocks that would otherwise apply to its parents.

Read more about our proposed solution to ensure the future survival of Fisher Island’s unique Acropora corals in Part 3.

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