Urchins

     Recently in Tasmania there has been an invasion of centro (long-spine) urchins, that have over grazed and  thus developed ocean barrens, unable to support much marine life.  The Eastern Australian Current has washed them into areas they have never before inhabited , probably due to increased strength of the current due to climate change factors.  Consequently this has nearly depleted rock lobster and abalone populations and poses a serious threat to shallow reef ecosystems as a whole.  The centro urchins are a keystone species in their native habitats, however have many detrimental effects when they invade other areas and there is great potential for them to continue spreading southward of Tasmania.  In order to not only better understand the grazing / feeding habits of these urchins but also how they respond to climate change conditions, Symon has developed an experiment in the ocean acidification lab that will examine these various factors and will be one of my main projects for the next 8 or so weeks.  We have approximately 140 baby urchins (varying in weight from .05 to .11 grams) each in a microhabitat in the larger flow through system.  The treatments consist of combinations of 3 different temperature treatments, 3 different acidification levels of the seawater, 2 different types of algae (encrusting and sargassum) and of the sargassum treatments some are allowed unlimited access to food and others have limited access to food.  We weighed and measured the urchins at the beginning of the experiment and will continue to do so weekly.  Wednesday begins week 2 so more to come as the experiment progresses.  

The babies

Flow through system

I think science programs should start offering a 'photographing scientific specimens' class!!!

   

Some photos of the urchins with the microscope camera, the scale is 1 mm and we use image J to set the scale to our the scale in the photos and measure the diameter and spine lengths of the urchins.