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Seafloor Squared You look at your watch—time for another survey. You pull two tools from pockets on your wetsuit. T e fi rst is a type of tape measure that looks like a belt. T e second tool is a set of three, plastic square-shaped frames. You unwind the belt along the seafl oor,

between the bases of two giant kelp stalks. T en you place the frames next to the belt, each less than a meter apart. Next you count the number of species you fi nd within each frame. T is is a quantitative survey.

Frame by Frame Inside the fi rst frame, you count a group of feather duster worms. T ese worms live in tubes made from their mucus and mud or sand. T ey have tentacles on their heads that look like feathers. T ey use these tentacles to take in oxygen and gather bits of food that fl oat by. In the second frame, you notice a number

of strawberry anemones. Together, these creatures look like a pile of pink donuts with white tentacles sticking out the top. T ey are carnivores. T ey eat other creatures.

Groups of sea urchins can take over sections of the ocean fl oor and change the ecosystem there.

A Fading Forest Within the third frame is a Kellet’s whelk. T e tan shell of this 15-centimeter-long sea snail reminds you of a drill bit. T e whelk has tracked down a dead fi sh. As it scavenges, the whelk acts as a

decomposer for the kelp forest. It’s recycling nutrients from dead things. Seeing so many animals within your frames is a good sign. T is area is healthy. As you take notes, your dive partner appears. He motions behind him. You grab the belt and frames and follow him. Before long you arrive at a clearing in the

giant kelp forest. T ere are only two kelp stalks growing here. Why so few? You swim toward the seafl oor and make a discovery. Small, spiky creatures called sea urchins are

gathered around the holdfasts of both kelp. T ey are chewing off the anchors that keep the kelp in place. T ere are so many of them that the kelp doesn’t stand a chance. Nearby, other giant kelp have already been

uprooted. You see some pieces strewn about the ocean fl oor. Others have fl oated away. You have seen this in other kelp forests before.


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