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Horse Conch - Pleuroploca gigantia

It's still snail week (hey every week is at least ten days long isn't it?) - with even groovier Gastropoda!

The Daily Bucket is a regular feature of the Backyard Science group.  It is a place to note of any observations you have made of the world around you.  Insects, weather, meteorites, climate, birds and/or flowers.  All are worthy additions to the bucket.  Please let us know what is going on around you in a comment.  Include, as close as is comfortable for you, where you are located. Each note is a record that we can refer to in the future as we try to understand the patterns that are quietly unwinding around us.

One of the benefits to living in Florida is the ocean.  This whole other set of ecosystems chock full of cool critters just down the road and under a little bit of water.

One of the dominant marine ecosystems in the big bend region of Florida (i.e. where the panhandle meets the peninsula) is the sea grass bed.  These are expanses of shallow water dominated by marine grasses.  Sea grass communities are apparently a major carbon sink.  Although making up a tiny proportion of the ocean they store carbon extremely disproportionately to the rest of the marine ecosystems.  Sea grass communities have declined to less than 50% of their 1950s levels here in Florida.  The primary causes are siltation, turbidity, damage from boating, and other human habitat modification.

One of the striking things about this marine community is that it is dominated by flowering plant species rather than 'seaweed' (i.e. algae) as is usual in submerged marine enviroments.  There is algae present such as (I presume) this red algae.
There are several species of sea grass in Florida but the dominant one is turtle grass, Thalassia testudinum.  It has broad flat leaves and will be seen in most of the pictures.  The sea grass beds are very productive with the plants doing a lot of photosynthesizing and fixing of nutrients.  The beds also offer shelter and hiding places for a myriad of small organisms.  This is a great place to snorkel but it isn't like snorkeling over a coral reef.  You aren't likely to come across big flashy fishes or spectacular coral formations.  What you will find, if you poke around, is a lot of cool little critters (and a few not so little like the horse conch Ms Mole is holding above).

One of the best places to explore sea grass is in St Joe Bay near Cape San Blas in the Florida panhandle east of Panama City.  This large shallow bay is largely cut off from the surrounding ocean by the St. Joe peninsula and is not influenced by any major rivers.  Thus the water is relatively clear.  The presence of St Joe Peninsula State Park also give lots of public access to the bay.

For many years a graduate student course in my department has come here every fall.  The course is in statistical analysis and the purpose of the field trip is to conduct an experiment on which to practice analysis.  This year the experiment dealt with colonization (by various small organisms) of substrate (bricks) and distance from patches of sea grass.

A brick

We joined the class although we were mostly there for the snorkeling.  Those in charge have been doing this trip for many years and they tell us wondrous stories of sea horses, burr fish, and so on.  I can see that it is going to take a few years to build up my search image skills.

The snorkeling conditions are slightly daunting.  The bay coastline has little wave action so there are no beaches to speak of.  At high tide the water ends and the forest starts.  At low tide there is generally a mass of dead sea grass to wade through (at high tide as well although then it is under water).  The shoreline odor isn't that great as a result.  The water is very shallow so you have to walk a ways before it is deep enough to start snorkeling.  My wife saw a (small) shark during the wading out part.  You have to be pretty careful walking because of stingrays.

Once you are in this is what you see at first.  A sea of undersea grass.

After a few minutes you start to pick up the details.

The sea urchins are the most abundant larger animals in this area.  It turns out that I didn't have an in focus picture of the common color form this time but, trust me, they are everywhere, gluing bits of shells and grass to themselves.

A lot of the organisms spend a lot of time in the sand.  Running your fingers through the sand frequently yields small bivalves (clams) or sand dollars.  This time, purely by chance it produced a horseshoe crab.  I didn't have the heart to dig it out completely so I just uncovered the top.

Bay Scallop - the bay is a common place for people to come and 'pick their own' scallops for dinner.

Echinoderms (members of the phylum Echinodermata) were out in force.  In addition to the red urchins and the sand dollars there were two other species of urchins and two species of sea star (i.e. starfish).  Other folks also found some brittle stars inside things but I don't have a picture.  All of these animals share striking structural similarities.  They are radially symmetrical (i.e. no front or back, no left or right) and usually in units divisible by five.  However they are ecologically quite divergent: the urchins are grazers, the sand dollars filter food out of the sand and the sea stars are predators.

Echinaster spinulosus  Brown spiny sea star.  Found in the sea grass.  Apparently more common in open well lit areas than most sea stars.
Luidia clathra This relative large sea star is one I've often seen washed up on beaches.  It primarily lives under the sand and has a soft velvety texture.  Can move very rapidly.
Variegated Urchin, Lytechinus variegatus  This is by far the commonest larger animal in the sea grass.  Most individuals were a reddish color but a few were colored like the one above.  They are almost always holding pieces of shell or turtle grass next to the body with their tube feet.  I found one that had sandwiched itself between two pieces of pen shell much bigger than the urchin.
Atlantic Purple Sea Urchin, Arbacia punctulata.  Sea Urchins have been very commonly used in studies of developmental biology.

Warning me that being cautious about running my hands through the sand was this adorable little Atlantic Stingray, Dasyatis sabina.  The whole animal was only just over a foot long meaning the disk of the body was only about four inches across.  It showed no inclination to move whatsoever.  

Our shoreline is, to put it mildly, not rocky.  There isn't much substrate for algae and invertebrates that like anchor themselves in place.  Animals with hard parts are and important source of substrate.  One of the larger and more abundant shells out there belongs to the pen shells (Atrina species).  These bivalves (clam relatives) have a pointed end they embed firmly in the sand and the broad end points up and is opened slightly so the animal can filter food from the water.  After the death of the mollusk, the shells are an important substrate for algae, barnacles, etc.  The inside of the shell can serve as a home for all manner of animals.  My colleague tells me she's found toadfish and blennies and all kinds of other things inside them.  I did see something dart to the back of one but I didn't feel like tearing its home apart.
Actual living pen shell embedded in sand with the 'mouth' facing up.  The orange is the mantle inside the shell.  Note even this living Atrina is covered in other organisms.
Various barnacles, algae, tunicates, worm tubes and other unidentified things on and in dead pen shells.
Juvenile grunt and what I think is manatee grass.

There are numerous small fish feeding in the sea grass, most of which don't hold still long enough for ID (juvenile grunt are among the most common).  This wrasse followed me around for quite a while (so it gets to be in the diary).  I saw some small jack, sheepshead, a lizard fish, and a young mullet.  None of which held still to be photographed.

But the real stars of the day were (what else?) Gastropoda.  Not a lot of them but the ones that did show up were spectacular.  I saw two horse conchs, large predatory snails.  The one I found was cool enough but then some smarty pants grad student had to find the truly enormous one that Ms Mole is holding up at the top.  The picture does distort its size somewhat but it was a real whopper.

The final sighting of the day was this sea hare (Bursatella leachii).  It was doing a very good imitation of a blob of algae.  But I noticed that it was algae with a purpose and a mission and thus not algae at all.  Instead it was a really cool sea slug pretending to be algae.  Sea hares are one of the different groups of sea slugs, snails that have lost their shells independently of the land slugs.  Nudibranchs are a closely related group of sea slugs.  Sea hares in the genus Aplysia are commonly used in studies of learning and neurobiology.



"Green Diary Rescue" is Back!

Meteor Blades has revived his excellent series.  As MB explained, this weekly diary is a "round-up with excerpts and links... of {diaries} bringing matters of environmental concern to the community... "

"Green Diary Rescue" will be posted every Saturday at 1:00 pm Pacific Time on the Daily Kos front page.  Be sure to recommend and comment in the diary.

Originally posted to Backyard Science on Tue Sep 17, 2013 at 05:00 AM PDT.

Also republished by Community Spotlight.

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