Tuesday, July 21, 2009

Things you find on a Queensland beach at low tide

Michele: Today is a very low tide: 0.09. In August we will have another low tide like this and then there won't be any more that low for the rest of our stay. The water level today was lower than the boat ramp. One of our very favorite things to do at the coast is tidepooling and over the past few days we've found some pretty cool things at the beach at low tide.

First, I will geek out a little and describe the hydrogeology of the beach at low tide. If you don't want to read about this just skip ahead to the critters. At low tide the ocean surface drops below the ground water table. This is evident on the photo from the shimmer of the wet sand. Throughout the wet area are seeps where the groundwater flows onto the surface. Lots of cool erosion sand patterns too that I didn't photo... yet. All the interesting low tide critters live in this region. Maybe because it is always wet, even when exposed by low tide. Maybe because they like the combination of ocean and ground water. questions for a biologist. As for the salinity of the seeps? I don't know. I didn't get to the ground and lick them... yet.

OK onto the critters. We saw these strange coils of sand that are pushed up from some critter in the sand. No these aren't piles of the topic of Gavin's recent post.. these are indeed sand. The piles accumulate when the tide recedes and the waves no longer wash the piles away. This photo shows one of the larger piles, some are smaller, some are nearly perfectly coiled. We speculated that these were clams but weren't able to dig deep enough to find one... yet. We don't yet have confirmation that these are clams... stay tuned.

Another fascinating find was live sand dollars. No sand dollars are not the eggs of starfish as some kids at school tried to covince Robin. These photos show the track of a sand dollar and the critter slightly buried in the sand as well as a cleaned off sand dollar on my hand. I remember finding lots of sand dollars on the beach in Florida as a kid. These must live in the water there too. Their thousands of tiny feet along the rim are amazing. In your hand, they kind of suction on a little -- not as much as a starfish but a little tickle.

Another thing you can f
ind on the beach are urchins. Both children (who are pointing out a crab) and the spiny kind that live in the sea. Note that Will is sporting the typical Queensland footwear (see Gavin's recent post). Unfortunately, the glassy rind of a vesicle within the basalt cut Will's foot only a few minutes after this photo was taken. Maybe we are not so crazy to be skeptical of this Queensland trend... or maybe Will just needs tougher feet. Next to the urchin in the second photo is sea cucumber. In the third photo, it doesn't look as if the sea cucumber that Robin found is in water, but it was in a shallow tide pool crawling along. Very cool find!
And all over the rocks are crabs. Gavin looks rather proud of finding this crab.

This blog format is not so convenient for lots of photos... Because facebook is much more convenient for series of photos I've made an album there. In the future when I have a bunch of images to post, I will just put them on facebook and only put a few here. If you want to see all the photos and don't have a facebook account.. yet.. just send me a note and I will email you a link to the album.


  1. cant believe how BLACK the sea cucumber is! i remember seeing one when i was in california.. and i thought they were green? looks like u all are having the times in your life!

  2. The strange coils of sand in your story came out of the back end of an acorn worm...hope this helps :)

  3. coils are from lugworms and not as previously suggested