Crushed shells ease acidity around young clams
· BehindLines newsroom
Fragments of shell can change the environment in which young clams grow. A study published on 29 October in Biogeosciences and presented by the University of California, Davis examines this effect in sand, at the scale of a laboratory experiment. It concerns Leukoma staminea, a bivalve of the North American Pacific.
For 90 days, the researchers compared four conditions: control or acidified water above a sediment that either did or did not contain crushed shells. This crossing makes it possible to separate the effect of acidification from that of the addition to the sand. It avoids comparing only two situations that would differ on several points at once.
The fragments raised the pH of the water held between the grains of sediment. The results indicate a partial easing of the effects of acidification on growth. The team also studied gene activity in the tissue involved in forming the shell. This part concerns gene expression; it does not describe a repair of DNA.
The university points out that adding shells to sediment belongs to Indigenous practices of coastal management. The experiment therefore seeks to shed light on a mechanism, rather than presenting the gesture as a recent invention with no history.
The publication nevertheless stresses the low replication of the set-up and the initial differences in size between the animals. These limits complicate the interpretation of the growth measurements. A local effect in the sediment does not show that an identical operation would succeed on every beach.
To judge any application, the ecological context, the duration of the effects and the field conditions will need to be checked. This study offers a line of research on the habitat of certain shellfish. It is neither an assessment of coastal restoration nor a solution to the acidification of the oceans as a whole.