DIVE DRY WITH DR. BILL #834: GREEN GROW THE ALGAE
Anyone who took a basic biology class in high school knows that most land-based plants create their own "food" through a process known as photosynthesis. The pigment that captures energy from the sun to initiate this process is known as chlorophyll. My former students had better know or I'll go back into the records and change their grade!
Wouldn't it be nice if we could do that too? A number of invertebrate critters are capable of incorporating photosynthetic pigments such as chlorophyll into their own tissues. This type of symbiosis is known as mutualism, a relationship that benefits both species. For example, the zooxanthellae in corals and sea anemones provide nutrients to their hosts while the host provides "fertilizer" and other goodies including oxygen.
Marine algae also create their own food through photosynthesis. The pigments involved in energy capture include chlorophyll and often accessory pigments such as fucoxanthin (brown algae) and phycocyanin (red algae). We often classify algae based on these accessory pigments. But why are they necessary? Anyone with a basic knowledge of the visual light spectrum should know that the color we perceive in an object is a result of those wavelengths being reflected back to our eyes.
Green chlorophyll is ideal for capturing sunlight on land and in shallow marine environments. It captures both the red and blue ends of the spectrum and reflects back the middle bands (green). Divers and other intelligent folks are aware that the red end of the spectrum is filtered out in shallow water. Thus photosynthesis based solely on chlorophyll would be less efficient at depth. The accessory pigments often reflect red or "brown" light back to our eyes and absorb the wavelengths at the blue end that penetrate deeper.
So green algae are most common at shallower depths than red algae. A number of species can be found in our waters. One of the frequently seen genera is Codium, represented by "dead man's fingers" (Codium fragile). Now I have never seen a dead man's fingers, but I question whether they are green (unless infected with mold). Other species are present in California waters as well.
Other commonly seen green algae include members of the genus Bryopsis. These are generally small, bushy algae that grow on rocks and occasionally other hard surfaces such as the shells of snails. That way they get to see more of the world... at a snail's pace, of course.
Another green alga that frequently confuses divers (and landlubbers alike) is Chaetomorpha spiralis. It appears like a bundle of thin filaments entangled in one another. I have had divers ask why there is so much green fishing line in the park at certain times of the year. Ha, any fish worth its salt would snap it if used as fishing line! Of course the fishing line I used years ago to catch bluegills and catfish often looked just like this alga after I made my cast!
Green algae are often "pioneering" species. They quickly establish on rocks that have rolled over and present a relatively uncolonized surface with little to no competition from other alage. Eventually the browns and others outcompete the greens. However the greens may attach to species like gorgonians (soft coral) or reef-building corals in warmer waters, thus posing a problem. In quiet waters, greens will often encrust on the surface of sand and other substrate forming an algal "mat."
So now you know a little more about the often overlooked greens in our waters. Aren't you thrilled? I knew you would be!
© 2019 Dr. Bill Bushing. For the entire archived set of over 800 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Green algae including species of Bryopsis, Codium, and Chaetomorpha with a dense growth of greens on a rock.
Anyone who took a basic biology class in high school knows that most land-based plants create their own "food" through a process known as photosynthesis. The pigment that captures energy from the sun to initiate this process is known as chlorophyll. My former students had better know or I'll go back into the records and change their grade!
Wouldn't it be nice if we could do that too? A number of invertebrate critters are capable of incorporating photosynthetic pigments such as chlorophyll into their own tissues. This type of symbiosis is known as mutualism, a relationship that benefits both species. For example, the zooxanthellae in corals and sea anemones provide nutrients to their hosts while the host provides "fertilizer" and other goodies including oxygen.
Marine algae also create their own food through photosynthesis. The pigments involved in energy capture include chlorophyll and often accessory pigments such as fucoxanthin (brown algae) and phycocyanin (red algae). We often classify algae based on these accessory pigments. But why are they necessary? Anyone with a basic knowledge of the visual light spectrum should know that the color we perceive in an object is a result of those wavelengths being reflected back to our eyes.
Green chlorophyll is ideal for capturing sunlight on land and in shallow marine environments. It captures both the red and blue ends of the spectrum and reflects back the middle bands (green). Divers and other intelligent folks are aware that the red end of the spectrum is filtered out in shallow water. Thus photosynthesis based solely on chlorophyll would be less efficient at depth. The accessory pigments often reflect red or "brown" light back to our eyes and absorb the wavelengths at the blue end that penetrate deeper.
So green algae are most common at shallower depths than red algae. A number of species can be found in our waters. One of the frequently seen genera is Codium, represented by "dead man's fingers" (Codium fragile). Now I have never seen a dead man's fingers, but I question whether they are green (unless infected with mold). Other species are present in California waters as well.
Other commonly seen green algae include members of the genus Bryopsis. These are generally small, bushy algae that grow on rocks and occasionally other hard surfaces such as the shells of snails. That way they get to see more of the world... at a snail's pace, of course.
Another green alga that frequently confuses divers (and landlubbers alike) is Chaetomorpha spiralis. It appears like a bundle of thin filaments entangled in one another. I have had divers ask why there is so much green fishing line in the park at certain times of the year. Ha, any fish worth its salt would snap it if used as fishing line! Of course the fishing line I used years ago to catch bluegills and catfish often looked just like this alga after I made my cast!
Green algae are often "pioneering" species. They quickly establish on rocks that have rolled over and present a relatively uncolonized surface with little to no competition from other alage. Eventually the browns and others outcompete the greens. However the greens may attach to species like gorgonians (soft coral) or reef-building corals in warmer waters, thus posing a problem. In quiet waters, greens will often encrust on the surface of sand and other substrate forming an algal "mat."
So now you know a little more about the often overlooked greens in our waters. Aren't you thrilled? I knew you would be!
© 2019 Dr. Bill Bushing. For the entire archived set of over 800 "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Green algae including species of Bryopsis, Codium, and Chaetomorpha with a dense growth of greens on a rock.
