Not so long ago, semen cryopreservation was a fairly expensive proposal, and reproductive specialists could never quite be certain whether their efforts would pay off with viable reproductive cells once the sperm thawed. Thanks to additional research and new developments in the area of assisted reproduction technology, humans are not the only life forms to benefit from cryopreservation; instead, animals of all kinds, including many endangered species, are reproducing with scientists’ help. Now, even coral can benefit. Let’s take a look at how biologists are helping conserve coral.
Understanding Coral Spawning
Like most other marine animals, many species of coral spawn, releasing reproductive cells into the open water. Though many species are capable of asexual reproduction, it is the tiny animals’ ability to spawn that is helping the Smithsonian Institution’s Dr. Mary Hagedorn to create what amounts to a sperm bank focused on preserving the world’s corals.
Approximately 75% of all stony corals release eggs and sperm, which are also known as gametes, into the water. During spawning, eggs and sperm are released. Shortly thereafter, they fuse and become larvae, which eventually grow into new coral colonies. Often, coral spawn in sync with one another. Called synchronous spawning, this occurs on the same night, even when more than one species is present on a reef. Environmental cues including temperature change, day length, and lunar cycle precipitate spawning; in some cases, coral send chemical signals to one another to indicate that they are ready to spawn.
Preserving Coral for the Future
Dr. Hagedorn and her team are gathering gametes from corals from Australia, Hawaii, the Caribbean, and other areas. So far, the researchers have frozen approximately one trillion individual coral sperm, which is enough to fertilize between 500 million to a billion coral eggs. In addition, they have preserved approximately three billion embryonic cells, some with stem cell characteristics. All of these cells possess the potential to mature into adult corals.
This dedicated team of researchers is racing against a clock that is always ticking faster. In the past few years, bleaching events have spread across the globe, in some cases causing so much damage that affected corals are not able to recover. Ocean acidification is weakening reefs and inhibiting coral skeleton growth. Other problems are causing rapid decline as well; in the Caribbean, for example, overfishing, disease, and high water temperatures have killed an estimated eighty percent of the region’s corals. Similar problems are causing devastation to Pacific reefs, and throughout the western and central portions of that ocean, researchers estimate that coral populations have shrunk by about fifty percent between the 1980s and 2000s.
There are some bright spots for coral; marine protected areas and other preserves suffer less from overfishing and other problems caused directly by human interference. Even so, these corals are not immune to the devastation warm, acidifying seas are causing.
Researchers working with corals are focusing not just on improving the odds for coral by freezing reproductive cells; they are also watching coral for signs of biological adaptability, and they are raising captive corals, then reintroducing them to wild habitats. Coral cells and coral sperm are being stored at various locations, side by side with reproductive material from dugongs, koalas, and other creatures. Thanks to these efforts, endangered corals are being given a chance to survive and perhaps even to thrive in the future.