Sea urchin - By: Marco Busdraghi

The coral reefs off of Hawaii are being smothered by tons of algae, and efforts have been made to help solve this dilemma. The answer comes from an unlikely source.. Sea Urchins. Sea urchins, commonly known as the “cows of the sea”, are being used along side a new underwater vacuuming system aptly named the “Super Sucker” in an attempt to finally start getting the algae off the reef and get them healthy again.

Researchers from the state Department of Land and Natural Resources Division of Aquatic Resources are pleased to announce that the project has been a success, as it has been using sea urchins alongside the Super Sucker for the past year in Kaneohe Bay.

“It exceeded our exectations,” Tony Montgomery, a state aquatic biologist commented. “It actually worked better than we thought.”

The project began in August of last year, where divers were manually removing the offending algae from the reef. Once harvested, the algae was then sucked up using the super sucker.. On another part of the reef however, a bunch of sea urchins were left to do their business. The results were that these cows of the sea were quite the eating machines. While the project is being deemed a success there is still a lot of algae to be removed, and Montgomery is remaining casually optimistic. “We will see how they do with thousands of pounds of algae to eat,” He said.

Above you can see a fascinating video of squat Urchin shrimp and below you find some basic information about this tiny shrimp.

The squat Urchin shrimp, known in scientific circles as Gnathophylloides mineri, is quite a fascinating invertebrate that many aquarists would often look over, or even never see.

This fascinating little creature is only milometers in length, and it survives in its own little world, not seeming to care about how the rest of the Sea Urchins live. These Sea Urchins actually live ON TOP of other Sea Urchins!

The Squat Urchin Shrimp is incredibly tiny, often never reaching more than 6mm in length, and it often orients itself parallel with their hosts spines, which not only protects it from becoming lunch for some other sea critter, but also makes it nigh on impossible to see, some would even say it’s effectively invisible to the naked eye. Colonies of these little guys often have numbers ranging from a few to a half dozen will share the same host Sea Urchin. Not only does it seek protection from its hosts spines, it actually feeds on them, proving once again just how successful this tiny creature is at surviving. This is a rather odd kind of parasitism, as it does not have any ill effects for the host.

The Squat Urchin Shrimp also will take every chance they get to feed upon the detritus that the host sea urchin picks up off the ocean floor on it’s travels.

Out of the estimated 5.5 gigatonnes of carbon emitted each year by human activities, about 1.8 percent are removed from the air and stored by echinoderms such as starfish, sea urchins, brittle stars and sea lilies. This makes them less important “carbon sinkers” than plankton, but the finding is still significant since no one expected them to catch such a large chunk of our wayward carbon.

The new discovery is the result of a study* led by Mario Lebrato**, PhD student at the Leibniz Institute of Marine Science. The work was done when he was at the National Oceanography Centre, Southampton (NOCS) and affiliated with the University of Southampton’s School of Ocean and Earth Science (SOES).

“I was definitely surprised by the magnitude of the values reported in this study, but [the study’s] approach seems sound, so the reported numbers are probably fairly accurate,” says palaeoceanographer Justin Ries of the University of North Carolina at Chapel Hill.

Ries also points out that these important creatures might be affected by ocean acidification.

“If the echinoderms end up being disproportionately susceptible to ocean acidification then it’s conceivable that the dissolving of echinoderm-derived sediments will be one of the earliest effects of ocean acidification on the global carbon cycle,” he explains. “In fact, maybe it already is.”
The body of an echinoderm consists of up to 80% calcium carbonate and according to the Lebrato study these hard-shelled animals collectively capture 100 billion tons of carbon each year.

“The realisation that these creatures represent such a significant part of the ocean carbon sink needs to be taken into account in computer models of the biological pump and its effect on global climate“, says Lebrato. “Our research highlights the poor understanding of large-scale carbon processes associated with calcifying animals such as echinoderms and tackles some of the uncertainties in the oceanic calcium carbonate budget. The scientific community needs to reconsider the role of benthic processes in the marine calcium carbonate cycle. This is a crucial but understudied compartment of the global marine carbon cycle, which has been of key importance throughout Earth history and it is still at present.”

The study has been published in the journal ESA Ecological Monographs.

* Mario Lebrato, Debora Iglesias-Rodriguez, Richard Feely, Dana Greeley, Daniel Jones, Nadia Suarez-Bosche, Richard Lampitt, Joan Cartes, Darryl Green, Belinda Alker (2009) Global contribution of echinoderms to the marine carbon cycle: a re-assessment of the oceanic CaCO3 budget and the benthic compartments. Ecological Monographs. doi: 10.1890/09-0553.

** mlebrato13 [at]googlemail.com

Genetic pattern analysis strongly suggests that California and British Columbia urchins are not connected via larval dispersal and comprise two distinct populations. Sea urchins have one of the longest larval periods of any known marine invertebrate and it has therefore been tempting to assume that ocean currents must be mixing urchin larvae all over the place, making it difficult for any distinct populations to form. But research results from the University of California now indicate that these two Pacific populations are two clearly separated ones.

Sea urchins –  Picture from the Red Sea

Together with former* graduate student Celeste Benham, marine biology professor Ron Burton of the University of California at San Diego have analyzed 500 adult sea urchins from Californian waters across five microsatellite markers and then compared the genetic patterns to an existing, similar database of 1,400 urchins from British Columbia. The Californian specimens were collected off the coast of San Diego, Los Angeles and Mendocino counties.

The genetic signatures found by Burton and Benham strongly suggest that the southern and northern populations are not connected via larval dispersal.

“From my evolutionary perspective, our results are important because they imply that, even on long time scales, there is no mixing, Burton explains. This means there is at least the potential for populations to adapt to different ocean conditions and gradually diverge. This is the first step in the two populations potentially becoming different species.”

This is the first time scientists have detected any population structure in the species. Similar studies carried out in the past have used fewer genetic markers and found no population genetics structure in the species despite having tested many different patches across its range.

“The take-home message of this study is that if you use more markers and newer techniques you will find some population differentiation that before nobody found,” says Burton.

* Benham is now a research assistant at the marine mammal laboratory at Hubbs-SeaWorld Research Institute in San Diego.

Compared to just over a century ago, the pH-value of the sea’s surface water has gone down by 0.1 (i.e. 25 percent). This has caught the attention of Jon Havenhand and Michael Thorndyke, researchers at the University of Gothenburg, and they have together with colleagues in Australia studied if and how this decrease affects marine animals.

spatangus purpuerus – Sea urchin

As part of the study, Havenhand and Thorndyke used sea urchins of the species Heliocidaris erythrogramma to study reproduction. Sea urchins reproduce by releasing eggs that are fertilized out in the open water. In the study, Havenhand and Thorndyke studied breeding sea urchins in water where the pH-value had been lowered from its normal 8.1 down to 7.7. This might not sound as a significant drop, but a change from 8.1 to 7.7 means that the water becomes three times as acidic as before.

Havenhand and Thorndyke found out that in this changed environment, the sea urchins’ ability to reproduce was decreased by 25 percent. The low pH-value made the sperm swim slower than normally and move less effectively, which lowered the fertilization rate. But the problems didn’t stop here; when an egg was fertilized, the low pH-value could interfere with larval development and this too decreased the amount of eggs that actually developed into healthy sea urchin larvae.

More research is now needed to find out if these reproductive problems linked to acidification can be observed in other marine animals as well.