Ulva lactuca (Sea Lettuce)
Shernae Sartor
"On the beach it’s more like over-ripe, discardable, still fairly green, table lettuce that can be overlooked and begins breaking down in the vegetable drawers of our refrigerators." - Pat Nash, WSU Beachwatchers, 2006 |
Taxonomy
Kingdom: Protoctista Phylum: Chlorophyta Class: Ulvophyceae Order: Ulvales Family: Ulvaceae Genus: Ulva Species: lactuca |
Sea lettuce is not a plant because it has no vascular system or roots. It is a green algae which means it is available for human consumption. It is often used in Asian cuisines as seaweed. Sea lettuce conducts photosynthesis and produces oxygen. The abundance of sea lettuce is causing alarm for fisheries around the world. It is believed to be the source of anoxic conditions in marine environments that lead to the deaths of fish and other sea animals. Special bacteria that decomposes dead materials in the marine environment must use oxygen to do so. It is not clear why sea lettuce populations are so vibrant other than high levels of nitrogen, but their deaths cause the bacteria to use all the oxygen left in the aquatic atmosphere. A project on Prince Edward Island in Canada was observed to see if harvesting the algae could prevent such events from occurring. Scientists around the globe are also trying to use sea lettuce in fertilizers, plastics, cements and even hygiene products and cosmetics. The future of sea lettuce is also traveling towards being used as a fossil fuel.
Sea lettuce or Ulva lactuca is a type of green algae. It is thin and very translucent, because it only has two cell layers. Many people enjoy this seaweed in salads and soups. It is very high in iron, protein, iodine, vitamin C and dietary fiber. It is found worldwide growing in the midlittoral zone in estuaries and other places rich in nutrients such as nitrogen. Sea lettuce is sessile which means it cannot move, so it anchors itself onto rocks and other hard substrates. Sea lettuce grows abundantly and is feared to create anoxic conditions by smothering other plants and organisms. Because of the large quantity of sea lettuce in some areas, when it dies it is broken down by large blooms of bacteria that deplete oxygen in the water. This then leads to harm and even death for fish and other oxygen-dependent organisms.
The life-cycle of sea lettuce is like that of a fern. It begins with the mature diploid sporophyte. Diploid means it has two sets of chromosomes. The sporophyte releases spores that grow into male and female haploid gametophytes. Haploid means it only has one set of chromosomes, which is half the amount of the sporophyte. The gametophytes will produce and release gametes that will join together to create a brand new sporophyte! Because sea lettuce is so thin, photosynthesis can occur at a higher rate than with other algae, awhich allows the sea lettuce to reproduce abundantly, “especially in areas where other organisms have been cleared away, like after a storm.” Sea lettuce can grow up to 2 feet tall and can live 75 feet below the water’s surface.[1]
Unlike the beloved kelp, sea lettuce is not a favorite food choice among marine animals. Perhaps they find it lacking in nutritional value. Besides humans, sea urchins, mollusks and other crustaceans, small fish and shorebirds add sea lettuce to their diets. Sea lettuce grows abundantly in the summer. This is called a “bloom.” During the summer months, a lot of sea lettuce washes up on shores. It quickly starts to deteriorate, turning into a brown mush. It gives off a horrid smell and is often mistaken for sewage.
Sea lettuce has no real predators besides extremely desperate marine herbivores and omnivores, pollution and technology (dredges) from mankind, and crashing waves and the dryness of the terrestrial environment.
The life-cycle of sea lettuce is like that of a fern. It begins with the mature diploid sporophyte. Diploid means it has two sets of chromosomes. The sporophyte releases spores that grow into male and female haploid gametophytes. Haploid means it only has one set of chromosomes, which is half the amount of the sporophyte. The gametophytes will produce and release gametes that will join together to create a brand new sporophyte! Because sea lettuce is so thin, photosynthesis can occur at a higher rate than with other algae, awhich allows the sea lettuce to reproduce abundantly, “especially in areas where other organisms have been cleared away, like after a storm.” Sea lettuce can grow up to 2 feet tall and can live 75 feet below the water’s surface.[1]
Unlike the beloved kelp, sea lettuce is not a favorite food choice among marine animals. Perhaps they find it lacking in nutritional value. Besides humans, sea urchins, mollusks and other crustaceans, small fish and shorebirds add sea lettuce to their diets. Sea lettuce grows abundantly in the summer. This is called a “bloom.” During the summer months, a lot of sea lettuce washes up on shores. It quickly starts to deteriorate, turning into a brown mush. It gives off a horrid smell and is often mistaken for sewage.
Sea lettuce has no real predators besides extremely desperate marine herbivores and omnivores, pollution and technology (dredges) from mankind, and crashing waves and the dryness of the terrestrial environment.
Many fisheries may have been outraged when they noticed a significant decline in
their yearly catch. Something was causing large numbers of fish and even other
organisms to die. What could it be? The culprit was sea lettuce.
In the summer of 2011, the PEI Department of Environment, Labour and Justice and the PEI Department of Fisheries, Aquaculture and Rural Development conducted a harvesting project on Prince Edward Island located in Canada.
The harvest of sea lettuce has been discussed as a possible means to reduce or eliminate anoxic events in PEI. Although this practice has been attempted in other areas, there is limited information available that would help guide this activity on PEI. This pilot was conducted to determine: (1) the effectiveness and efficiency of a sea lettuce harvest
on PEI, (2) the harvest intensity required to impact sea lettuce populations, (3) the harvest intensity required to prevent anoxic events from occurring and (4) the environmental impacts resulting from the harvest.
The project was successful in harvesting a total of 64.8 tonnes of sea lettuce from Covehead Bay, 29.9 tonnes from Hills River and a total of 146.2 tonnes (99.9 tonnes on the first harvest, 46.3 tonnes on the second harvest) from Mill
River. All harvested sea lettuce was either spread on agricultural land or composted.
The results of this piolot were not successfull in showing any decline in the anoxic events of all cites.[8]
their yearly catch. Something was causing large numbers of fish and even other
organisms to die. What could it be? The culprit was sea lettuce.
In the summer of 2011, the PEI Department of Environment, Labour and Justice and the PEI Department of Fisheries, Aquaculture and Rural Development conducted a harvesting project on Prince Edward Island located in Canada.
The harvest of sea lettuce has been discussed as a possible means to reduce or eliminate anoxic events in PEI. Although this practice has been attempted in other areas, there is limited information available that would help guide this activity on PEI. This pilot was conducted to determine: (1) the effectiveness and efficiency of a sea lettuce harvest
on PEI, (2) the harvest intensity required to impact sea lettuce populations, (3) the harvest intensity required to prevent anoxic events from occurring and (4) the environmental impacts resulting from the harvest.
The project was successful in harvesting a total of 64.8 tonnes of sea lettuce from Covehead Bay, 29.9 tonnes from Hills River and a total of 146.2 tonnes (99.9 tonnes on the first harvest, 46.3 tonnes on the second harvest) from Mill
River. All harvested sea lettuce was either spread on agricultural land or composted.
The results of this piolot were not successfull in showing any decline in the anoxic events of all cites.[8]
Sea lettuce that is used as seaweed is air-dried and pressed into long, thin sheets. Sometimes it is eaten freshly rinsed in soups such as in the dumplings above.[6]The algae also aids with the consistency of some ice cream products.
Sea lettuce is not only enjoyed as a delicious and nutritious snack but also as a skin care regiment. Alba Botanica’s Sea Lettuce Cleansing Milk utilizes the algae’s natural enzymes to gently exfoliate skin. [4] Sea lettuce is also use in
many handmade soaps and scrubs.
Currently Sea lettuce, do not seem to have any great threats aside from pollution and bacteria. Bacteria decomposes it and in doing so, the bacteria uses oxygen which in turn kills off the sea lettuce. Pollution would cause a problem for sea lettuce due to humans polluting the oceans.
Sea lettuce is not only enjoyed as a delicious and nutritious snack but also as a skin care regiment. Alba Botanica’s Sea Lettuce Cleansing Milk utilizes the algae’s natural enzymes to gently exfoliate skin. [4] Sea lettuce is also use in
many handmade soaps and scrubs.
Currently Sea lettuce, do not seem to have any great threats aside from pollution and bacteria. Bacteria decomposes it and in doing so, the bacteria uses oxygen which in turn kills off the sea lettuce. Pollution would cause a problem for sea lettuce due to humans polluting the oceans.
Residences of Tauranga, New Zealand know very well the horrible smell caused by sea lettuce. Professor Rocky de Nys, Head of Aquaculture at James Cook University in Townsville, Australia, specializes in turning algae into crude biofuels -
which can then be refined into whichever type of fuel is desired.[4]
The Olmix company of Britain is working on using sea lettuce for fish nutrition in aquaculture. They are also working on ways to utilize is as fertilizers and bio-fuel.[7]
The future of sea lettuce rests within the future bioengineers, chemists, marine biologists, farmers and concerned public. It could open a new field of revenue for all global economies just as corn has done for the United States. Our oceans have aided in the survival of mankind, now it is our turn, our responsibility to help them.
which can then be refined into whichever type of fuel is desired.[4]
The Olmix company of Britain is working on using sea lettuce for fish nutrition in aquaculture. They are also working on ways to utilize is as fertilizers and bio-fuel.[7]
The future of sea lettuce rests within the future bioengineers, chemists, marine biologists, farmers and concerned public. It could open a new field of revenue for all global economies just as corn has done for the United States. Our oceans have aided in the survival of mankind, now it is our turn, our responsibility to help them.
1. Environmental Data Center at the University of Rhode Island
www.edu.uri.edu
2. Capital Regional District
www.crd.bc.ca
3. Bay of Plenty Regional Council
www.boprc.govt.nz
4. Bay of Plenty Times
www.bayofplentytimes.co.nz
5. BetterLife
www.betterlife.com
6. Eat The Weeds
www.eattheweeds.com
7. Olmix
www.olmix.com
8. Prince Edward Island Department of Enviornment Labor and Justice
www.gov.pe.ca
9. Bay of Plenty
http://www.boprc.govt.nz/environment/coast/tauranga-harbour/sea-lettuce/
www.edu.uri.edu
2. Capital Regional District
www.crd.bc.ca
3. Bay of Plenty Regional Council
www.boprc.govt.nz
4. Bay of Plenty Times
www.bayofplentytimes.co.nz
5. BetterLife
www.betterlife.com
6. Eat The Weeds
www.eattheweeds.com
7. Olmix
www.olmix.com
8. Prince Edward Island Department of Enviornment Labor and Justice
www.gov.pe.ca
9. Bay of Plenty
http://www.boprc.govt.nz/environment/coast/tauranga-harbour/sea-lettuce/