A new study could be good news for the fate of abalone off the California Coast in the face of climate change and ocean acidification.
The study by Cal Poly’s School of Science and Mathematics and California Sea Grant “sounds a hopeful note for the resilience of California abalone in the face of ocean acidification,” read a news release. “The study, conducted by Cal Poly biologist Jennifer O’Leary, focuses on crustose coralline algae and their effects on abalone’s ability to reproduce.”
O’Leary said, “This research is novel in that it shows that some critical interactions between species can be maintained, even for sensitive species. This is good news for California abalone, as loss of the algae would mean catastrophic declines in abalone replenishment.”
Pinkish in color, the algae grow on rocks near shore and produce a hard external skeleton of calcium carbonate, similar to coral. Larval abalone, which are born free floating in the sea and attach to rocks to grow, are more likely to settle where coralline algae are present.
The algae give off a scent, “that abalone use to find the right habitat. Previous studies have shown that coralline algae are sensitive to ocean acidification.”
One of the suspected ill effects of climate change, ocean acidification, occurs as carbon dioxide is absorbed by seawater. As CO2 in the atmosphere is absorbed by ocean waters, it causes a “chemical reaction” that increases the acidity of seawater.
O’Leary and her fellow researchers devised their tests to see whether the algae would still give off the right scent for abalone after ocean acidification. Since the beginning of the Industrial Revolution (roughly 1760), ocean waters have experienced a 30-percent increase in acidity, according to the National Oceanic and Atmospheric Administration.
“Ocean acidification,” O’Leary said, “is one of the biggest issues facing marine communities. It’s critical to understand the impacts of this threat and evaluate where and when organisms and communities are able to withstand acidification.”
The test involved exposing a group of algae to ocean acidification for 4 months, then seeing whether the algae still attracted abalone settlement.
The results were encouraging because while acidification reduced algal growth, more than half of the abalone produced larvae when the algae were present, compared with fewer than one in 10 when the algae were not. The researchers concluded that some species interactions may continue despite acidification, which will increase the species’ resilience.
A possible explanation for the results is that some organisms in California may be better able to withstand ocean acidification because they live in highly variable physical conditions naturally. But O’Leary cautioned, “This explanation needs to be tested before it can be confirmed.”
If the results hold, it could be good news for a species that has seen wild fluctuations in populations, ultimately leading to collapses in most of the varieties. Abalones are also a favorite food of sea otters, which exact a heavy toll on their numbers.
Abalone is a marine snail in the family, Haliotidae. According to Wikipedia, the number of species recognized worldwide ranges from 30-130 with over 230 species-level categories (ex. red, white and black abalone). Abalones are found in most oceans and there are eight species of abalone in the U.S. West Coast (seven off California). The most comprehensive treatment of the family considers 56 species valid, with 18 additional subspecies.
There is currently no commercial fishing of abalone off California, regardless of species, according to the California Department of Fish & Wildlife. However, a recreational fishery for red abalone still remains in Northern California. The commercial fishery was halted in 1999.
Recreational take is allowed with a California fishing license and abalone stamp, but is prohibited south of the mouth of San Francisco Bay. Only red abalone may be taken and they must measure 7-inches or greater along the longest shell diameter.
No more than three red abalones may be possessed at any time and no more than 24 may be taken in any calendar year. No scuba or surface-supplied air may be used in taking abalone, so-called “shore picking.”
Considered a delicacy, abalone are also grown in aquaculture operations, like the Abalone Farm located north of Cayucos, and harvested and processed into steaks, while still relatively small (about palm sized), for export to fresh fish markets and seafood restaurants.
By Neil Farrell
