Monday, June 8, 2015

Giant Kelp

As today is World Ocean Day, I thought I would feature a post about one of my favorite algae, the giant kelp, or more scientifically Macrocystis pyrifera. I learned to SCUBA dive in the kelp forests of Southern California. I have many, many fond memories of fining my way through the fronds. The way the light filters through the blades, the gentle swaying of the stalks, the many creatures darting around, was the epitome of peaceful.
My best pic of kelp, I haven't been back since digital cameras :(
Giant kelp gets its common name because it truly is giant, it can be 150 feet long and grow almost 2 feet a day! Kelp forests are so large they can be seen from space. In fact, Floating Forests takes advantage of this fact by using volunteers to mark the location of kelp in satellite imagines, it's a great little citizen science project which I reviewed here.

The pneumatocysts at the bottom of each blade resulted in the genus name Macrocystis as it means "large bladder." One of the characteristics that distinguish giant kelp from bull kelp or other large brown algae, is the single pneumatocyst found at the end of every single blade. These bladders are full of gas to keep the algae floating in the water column and closer to the sunlight needed for photosynthesis. Looking like a giant tangled knot of roots at the bottom of the kelp is the holdfast. Holdfasts do just what the name implies, hold tight so that the algae is not dislodged in rough conditions, they do not absorb water or nutrients like roots do for land plants. 

Another ancient film photo, this one featuring CA state fish the Garibaldi
Kelp forests resemble the forests you've probably hiked through since they are the base of a large food web, providing both food and habitat. They create a vertical environment, with different species of fish, invertebrates, algae, and even marine mammals inhabiting the various levels. They can be found in the holdfasts, living in the fronds, playing in the canopy. Sea otters have been known to wrap themselves in the canopy to keep themselves in position while sleeping. Encountering macrofauna such as seals, sea lions, giant sea bass, or sharks was common for me when diving the Channel Islands kelp forests, but my favorites were the tiny creatures. Staring closely at the rocks and kelp to find little invertebrates hiding in the fronds/holdfast or fish that mimic the kelp, all of which is easily missed when swimming past, was always exciting for teenage me. Not only do they provide habitat on the shore, when the holdfast breaks down, floating kelp mats bring their nutrients and hitchhikers out to the open ocean where they attract pelagic fish and birds.
 
Giant kelp is harvested and used to make algin, a thickening agent which is found in a lot of food. It also has been used for fertilizer, gun powder, in cosmetics and many other applications. In California, harvesting kelp is a $40 million dollar industry. To protect the kelp forest environment, only the kelp found in the top 4 feet of the water column are collected, leaving the bulk of the strand in tact to regrow. In addition to harvesting, kelp forests provide other economical advantages to the coasts they cover, such as tourism. Another important feature is shoreline protection, waves are slowed down by the thick kelp forests and thus less energy hits the shore, resulting in less erosion.
Last old scanned, film photos of the kelp forests, this time looking up!

To experience a small taste of the diversity of the kelp forest, Monterey Bay Aquarium features a Kelp Cam in their big kelp forest tank here, as does Scripps Birch Aquarium here.


References
http://aquarium.ucsd.edu/Education/Learning_Resources/Voyager_for_Kids/kelpvoyager/index.html
http://www.nhm.ac.uk/nature-online/species-of-the-day/biodiversity/climate-change/macrocystis-pyrifera/index.html
http://www.mbari.org/staff/conn/botany/browns/james/default.htm
 http://sanctuaries.noaa.gov/about/ecosystems/kelpdesc.html
http://www.westcoast.fisheries.noaa.gov/habitat/habitat_types/kelp_forest_info/about_kelp_forest.html

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