David Kirsh asked,
> What about the "sand flea" or "sand bug" crustacean that burrows quickly
when it's uncovered?

Some other researchers do track Emerita talpoides or similar amphipod
crustaceans; they are good candidates as bioindicators although there may be
more than one species on some shores. We do take note of them, but they
aren't common enough to support a detailed analysis. We usually just find
one (or more usually none) after digging in three or five spots on the beach
for Donax.

Peggy Williams wrote,
> And Donax are all covered up and killed by beach renourishment, rife here
in Florida. It takes some time for them to recolonize a renourished beach!

I keep hearing this, and I believe it. However, the few renourishment
projects in Alabama before 2004 did not seem to have this effect, probably
because the amount of sand moved was relatively small and most of the sand
was pumped from offshore onto the upper (normally dry) part of the beach.

Post-Ivan renourishment may be different; in this case, sand that the storm
washed inland was bulldozed from the coastal highways and nearby back onto
the shore. I haven't been sent to inspect the shore yet but maybe Doug
Shelton can comment on how the Donax are faring. Parts of the coastline are
still controlled by police checkpoints, off-limits to casual visitors.

It would be very useful to know HOW long it takes for a beach to recover its
Donax population after renourishment. Since renourishment projects are
usually publicly announced well ahead of time, it should be possible for a
local resident to measure populations before and after renourishment, with
periodic measurements for at least a year afterward. Ideally, measurements
should be made at the same point in the tidal cycle each time, so if you are
studying a whole coastline with several sites, I recommend measurements at
neap tide. This is the point in the tidal cycle in which the tides are
minimal, so they will not change much during the day. Measurements can be
made monthly or less often; monthly is best. The study should continue for
at least one year because the populations naturally vary quite a lot during
the year regardless of human interference. Also, you should measure the
population at several points on the same beach, because Donax populations
are very patchy; you can find 20 specimens in one spot and only 3 nearby. Be
aware that Gulf beaches may have more than one species of Donax, as Harry
Lee has made clear:
http://www.jaxshells.org/anewolda.htm
http://www.jaxshells.org/0203.htm
It would help to measure the water temperature with a thermometer, because
Donax tends to become sluggish in cold weather, or at colder times of day.
Note anything unusual, such as storms, oil spills, epibionts on the shells,
etc. Don't assume that you'll remember anything accurately -- write it down
at the beach!

This sort of study could be conducted by a high school biology teacher, a
retired person, or simply someone who wants to make a contribution to
science and the environment. Because Donax variabilis is a common,
attractive, and highly visible mollusk, it has been studied often by
different researchers and there is more information available about it than
for most species. But we don't know all the basics, and the taxonomy of the
smaller forms is still a mess. It's amazing how long it has taken for people
to realize that a lot of what looks like "juvenile D. variabilis" is really
adult D. parvulus, for instance. Under our noses!

Cheers,
Andrew

Andrew K. Rindsberg
Geological Survey of Alabama

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