Roland,

There is an interesting side aspect of this question that I have
encountered in Southern California recently.  Normally our sandy beaches
have a limited fauna in evidence.   Some of the beaches in San Diego
County, however,  are being replenished with sand dredged from
offshore.  The one beach that I visited is suddenly loaded with shells
of many different types.

There are deeper water species in evidence (Cancellarias, Turrids,
Bursa, some deepwater Epitoniums, etc.) and many shallow water species
as well.  These shallow water shells, however, include species normally
found in muddy bays and other environments unrelated to the current
habitat in that spot.

What is going on here?  It happens that the dredged sand is coming from
a submerged beach terrace that was the coastline about 10,000 years
ago.  So, this particular beach is strewn with shells that are the
remains of current intertidal residents, current deeper water species
and fossil/subfossil species.  Could it get more confusing?

Is this experience similar to what one finds in beach replenishment
projects in Florida?

Phil Liff-Grieff
[log in to unmask]
La Crescenta, California

Roland Anderson wrote:

>  Hi All,Does anyone know the relationship between the live mollusks
> living intertidally on a beach and the dead shells you might find on a
> beach? How well do the washed-up shells reflect the actual population
> living there? Anybody know of any studies done on this
> subject?Thanks.Roland