Conducting Surveys It takes awhile for you to reach the bottom, 18 meters down. At the base of the kelp, you notice a tangle of woody roots. Its called a holdfast. T is structure fi rmly anchors the kelp to the seafl oor. It’s time to get to work. Your fi rst task is to
identify some species living or growing in this area. Scientists call this a qualitative survey. You pull out a graphite stick attached to
the end of some surgical tubing. T is tubing is threaded through a hole in a synthetic plastic slate. You can write on the slate, and the water won’t wash away your marks. T is is how you will keep notes during your dive. You write down that you saw young bull
kelp growing up from the bottom here. You also remember to write about the gopher rockfi sh that was hunting smaller fi sh further up in the bull kelp forest.
Making Observations As you look around, you notice something out of place. A type of brown seaweed is growing among the bull kelp. T is seaweed is an invasive species. It’s native to Japan and China. If the species gains a foothold here, it might change the local ecosystem. You carefully record this in your notes. As you bend down to examine a clump of
the brown seaweed, something glides past your fi eld of view. You spin in the water and fi nd yourself face to face with a harbor seal. T e seal is curious. First it swims up close
to get a good look at you, staring into your facemask. T en it swims lower, playfully nipping at the tips of the fi ns on your feet. T e seal swims ahead, and you follow. T e
bull kelp forest thins out. Taking its place is a diff erent species, a grove of giant kelp. You point toward the giant kelp and swim that way. Your partner nods and follows.
Swimming with Giants As you approach the giant kelp, you see how diff erent it is from bull kelp. Giant kelp needs more space to grow. Swimming here is like fl ying through a forest on land. A few tubes jut out from the base of each plant. Tiny, gas-fi lled fl oats support the tubes all the way to the ocean’s surface. Hundreds of blades that look like leaves stick out from the tubes in every direction. Giant kelp grows
very quickly—sometimes a third of a meter in one
day! It lives for many years. T is
makes it a perennial. Bull kelp is diff erent. It only grows for
The holdfast of giant kelp keeps it anchored to the ocean fl oor.
6 NATIONAL GEOGRAPHIC EXPLORER
one year. T en it dies. It is called an annual. But both types of kelp absorb carbon dioxide, just like land-based forests. T ey use photosynthesis to change carbon dioxide into energy for growth. And they produce much of the oxygen we need to breathe.
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