The "Plant Life" of the Seas -- Oxygen Producers, Food Producers, Habitat Providers

One of the most prevalent and influential aspects of the oceanic (and even the world's!) environment are algae--also known as "sea weed". Algae are sort of misunderstood because they are assumed to be "plants"--but they more resemble bacteria in their structure. However, they do photosynthesize. They provide much of the oxygen for the ocean and the atmosphere. Some kinds of algae resemble bacteria more than others. And, some algae resemble terrestrial plants more than others. Some of these algae are microscopic. Some are huge--up to 100ft tall. Some have calcium "shells" and stay on the ocean bottom. Others can SWIM!--they have a "flagellum" for propulsion and they are planktonic. Algae live in all sorts of environments other than the ocean (although we'll be sticking with the oceanic ones with this lens!). There are algae that live in snow in the Alps, and algae that live in freshwater and even in terrestrial environments. There's one on Guam called "taki utsan" (taki is a word for "excrement" and utsan means "rain" in the native Chamoru language)--this blue-green algae lies dormant, black, and crispy on the ground in the grass during the dry season, but when the rainy season kicks in, it becomes a slippery, slimy, green mass that resembles the "blob that ate the island"!

Two of the most obvious and prevalent brown algae (Phaeophyta)--kelp (pictured the photo at the top of this lens and to the left) and sargasso--provide huge areas of habitat for sea life such as fish, turtles, molluscs, and echinoderms.

Certain members of the red algae family (Rhodophyta) are "calcareous" -- in that they create calcium "shells" or "structures" within their cell structure. When these algae eventually die, they provide much of the substrate or solid structure of a coral reef--in fact, some red algaes provide more structure for a coral reef than the coral itself! Red algae are also some of the most economically valuable sea life in that they are regularly harvested in many cultures for food (in Japan, "nori"--used for wrapping sushi) and other products.

Green algae (Chlorophyta) are also commonly seen along beaches and on the reef. Some are again, like some red algae, calcareous, and contribute to the substrate or structure of the ocean floor. Other green algae are commonly harvested and eaten--such as the "sea grapes" (Caulerpa racemosa) shown being harvested on the reef flats of Guam in the photos below.

The blue-green algae (Cyanophyta) are some of the more weird varieties of oceanic (and elsewhere) algae. Although many grow commonly on the coral reefs and near the shore, these algae are the closest to bacteria in the way that they live (and their structure). Many of these blue-green algae synthesize oxygen through the using the "plant-method" of chlorophyl, others can synthesize oxygen directly from the water (it's "dihydrogen monoxide, right?) or from hydrogen sulfide produced by volcanic vents in the sunless deep abyss.