The Wonder of a Pink Beach

The beaches of Eleuthera Island, Bahamas are famous for having pink sand, and after the first time I saw these beaches several years ago, I heard and formulated myself some reasons for it.  First, I heard that the beaches were pink because of ground up conch shell.  This didn’t make a whole lot of sense to me because, when I looked closely at the sand, the pink pieces really didn’t look like shell.  My guess was that they were pieces of coralline algae, found everywhere on the reefs.

One of several species of Tubular Thicket Algae (Galaxaura spp.), a red coralline algae that incorporates calcium carbonate (the material coral and shell is made of) into their tissues making the algae hard like coral.  Pieces of this algae are constantly breaking off and being weathered, becoming an important component of sand.  This coralline algae is growing on a colony of finger coral.

I have learned from studying marine organisms that you cannot always identify something from first look. I have mistaken plants for animals and animals for plants in the past and it appears that I have done the latter again. It started when we recently visited a gift shop in Rock Sound, Eleuthera Island, Bahamas that specializes in making jewelry and other things from the local pink sand. In the store, an explanation of what makes the sand pink was posted along with some rock and sand samples. I had seen the red blobs on rocks and shells many times and written them off to be a type of coralline algae.  It makes perfect sense that pieces of this algae mixed in the sand would make it pink.  However, the explanation at the shop was that Foraminifera (often referred to as Forams) caused the pink sand.  I have known what Forams are for years (I will explain), but my preconception did not allow me to realize those red blobs as Forams.  I knew that terms, such as Foraminifera, are not bandied about lightly by island gift shops so I was curious.  Back at the boat I consulted the internet and soon came up with a scientific name (Homotrema rubrum) which allowed me to get more specific information and pictures—wow, I love it! I then went back to my stash of shells and found one covered with them!

Forams (Homotrema rubrum) found on a Carved Star Shell (Lithopoma caelatum) that I had collected a couple of years ago.

So now–what the heck is a Foraminiferan?  Well, it is a one-celled organism (Protist), that is like an amoeba in that it has no particular shape and it is very fluid.  Forams make a shell (called a test) around their bodies that can look very much like a snail shell or are made up of specific types of sediment stuck together. How a one-celled organism does this with no brain, nervous system, fingers or toes is one of the mysteries of life.  There are species that live drifting about in the water, in the sediment or attached to substrate.  Many are microscopic but some can be easily seen with the naked eye. The test structure is made of tiny compartments with pores where the protoplasm streams out in fine threads to catch prey.

Close-up of some of the forams found on the star shell.  You can see the small compartments.  Homotrema rubrum forms a somewhat circular glob, sometimes with points.  Some of the points on these have been broken off.  Thread-like objects on the forams are dust.

This particular foram makes its test with the help of an algae that lives with it symbiotically.  The photosynthetic pigment in the algae lends the color to the test.

At our anchorage in Governor’s Harbor, Eleuthera, I noticed, on the chart, a beach labeled Pink Sand Beach.  So, of course, I had to go.

Pink sand beach near Governor’s Harbor, Eleuthera, Bahamas.

The pinkest part is near the ocean and I think the best time to see it is at low tide. The color eventually fades in the sun and you will see less pink where the sand has been exposed.

Close-up of sand on the Pink Beach where pieces of the red foram were concentrated.
The foram particles are somewhat less dense than the rest of the sand and tend to float up with the waves and be deposited in ripples and around objects like this small piece of Sargassum weed.
Bill found a small bivalve shell with several forams on it in various stages of wear.
You can see the pores on this one where the protoplasm streams out.  I was hoping it might be alive but saw no protoplasm.

This beach was very clean without any shells that day.  We made our way over to some rocks.  Along the way I saw this stranded Portuguese Man O War.

The Portuguese Man O War (Physalia physalis) is related to the jellyfish but is actually a colony of hydrozoan polyps.  One modified polyp creates the blue float then the other polyps are modified to serve as defensive, feeding and reproductive parts of the colony.  These animals have a very bad sting.

At the rocks there were numerous small potholes left full of water at low tide. This is always a good place to find critters.

Algae-covered rocks are exposed at low tide.  Look into the potholes filled with water to find beautiful snails.
In this pothole we see the round shells of Nerite snails and the pointed periwinkle snails.  The zebra-striped ones are Zebra Nerites (Puperita pupa), I am not sure what the small brown one is, and the periwinkle is the Zebra Periwinkle (Littorina ziczac).  Ooops!  the periwinkle in the right corner has eyes and legs–it is a hermit crab, not a snail.
This Tessellate Nerite (Nerita tessellata) is less than an inch across but looks like a giant next to the small periwinkles–but look again–those periwinkles are no longer snails they are hermit crabs.
The Tricolor Hermit Crab (Clibanarius tricolor), like other hermit crabs, uses a snail shell as a home.  The snail actually makes the shell while it lives and grows and occupies it until it dies.  As the crab grows, it must find a larger shell.

There are always surprises to be found when observing marine life.  It’s the best when I clear up my own ignorance.

I have used the following website to obtain information on foraminiferans. http://www.ucmp.berkeley.edu/fosrec/Wetmore.htr

 

2 thoughts on “The Wonder of a Pink Beach”

  1. I learn something new everyday. Now I know what the red formations on shells are all about! Cool!

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