By Alex Scott
It’s all in the name: Hoshizuna no Hama, or Star Sand Beach, located on Taketomi Island in Okinawa, Japan, is filled not with sand made up of rocks and minerals, but instead with microscopic star-shaped particles. These tiny particles have no relation to the stars in the night sky, nor to the starfish that often wash up on shore with them.
Star sand is actually the remnants of tiny organisms, a group of animals belonging to the subphylum Foraminifera. Their scientific name is Baculogypsina sphaerulata, but marine biologists call them “living sand,” although technically the discarded exoskeletons of the microscopic animals that wash up by the millions on shore are just the dead remains. This particular species of “forams” is found only in East Asia along the Pacific Ocean in coral reefs, making Star Sand Beach and the other coastlines where B. sphaerulata live and die rare treasures.
The shells of these animals aren’t just good for admiring and collecting, however. They also may one day be used to combat the adverse effects of climate change. A 2014 study published in the Journal of Sea Research (below) suggests breeding the forams artificially in order to replenish beaches and save sinking coasts and coral reefs that are in danger of rising sea levels.
Although that solution may be a long way from becoming reality, in the meantime we can do our best to protect coral reefs and our coastline ecosystems, down to the tiniest star on the beach.
Saving the Shoreline with Star Sand
Photographs of Baculogypsina sphaerulata in (A) its natural habitat and (B) a culture tank. The bar in each photograph measures approximately 1 cm.
A 2014 scientific study led by researchers at the University of Tokyo presents a unique solution to the problem of rising sea levels due to climate change: breeding foraminifera in order to replenish coastlines. The study, which took place on the island of Tuvalu north of Fiji, is one of many being done by scientists around the world working on beach nourishment, and while others have done smaller scale experiments breeding star sand, this study focused on a much larger scale over a much longer period of time. In this way, the researchers were hoping to test the viability of breeding star sand all along the Pacific coast in order to save the coastlines.
After recreating a Tuvalu coastline environment in a large plastic tank using artificial lawn, coral sand, and PVC pipes to move seawater to simulate currents, the team placed two batches of foraminifera, one with larger sized shells and one with smaller, into two separate areas. Over the next 182 days, the researchers recorded both the average size of the shells and the number of shells in each environment and compared them to the start date and to natural populations at a nearby beach.
There were many fascinating results that emerged from the two batches, but the most important was the first ever successful asexual reproduction of foraminifera in artificial conditions. The researchers identified many factors like sunlight, algae growth, and water movement that may have lessened the extent to which the star sand grew and multiplied, but their initial success will undoubtedly lead to more experiments and more refined techniques. As they write in their conclusion, “There are significant merits to culturing Foraminifera as a countermeasure against sea level rise, although technical issues still remain to be resolved.”
Although using forams as a method of coastal rejuvenation is not a tried and true method yet, this study proves it is possible to breed large batches of star sand in an artificial environment, a critical first step in using star sand to save the shoreline.
This article appeared in the Beachcombing Magazine January/February 2020 issue
Thank you to Takashi Hosono for sharing his research findings from "Mass culturing of living sands (Baculogypsina sphaerulata) to protect island coasts against sea-level rise," Journal of Sea Research, July 2014. Authors: Takashi Hosono, Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo; Paeniu Lopati, Fisheries Department, Teone Funafuti, Tuvalu; Filipo Makolo, Fisheries Department, Teone Funafuti, Tuvalu; Hajime Kayanne, Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo.