Marine phytoplankton are mainly comprised of microalgae known as dinoflagellates and diatoms, though other algae and cyanobacteria can be present. There are thousands of species of planktonic algae, or microalgae, floating in water all over the world.
Green algae, diatoms and dinoflagellates are the most well-known, though other microalgae species include coccolithophores, cryptomonads, golden algae, yellow-green algae and euglenoids 1.
While diatoms and dinoflagellates are forms of planktonic algae, they can be incorrectly classified as red or brown algae 9. Red and brown algae are not considered phytoplankton as they are not free-floating. True red and brown algae are rarely single-celled, and remain attached to rock or other structures instead of drifting at the surface 1, Multicellular green algae is also not considered phytoplankton for the same reasons. To be considered a phytoplankton, the algae needs to use chlorophyll A in photosynthesis, be single-celled or colonial a group of single-cells , and live and die floating in the water, not attached to any substrate 1.
Despite their ability to conduct photosynthesis for energy, blue-green algae are a type of bacteria. This means that they are single-celled, prokaryotic simple organisms. Prokaryotic means that the cyanobacteria do not have a nucleus or other membrane-bound organelles within their cell wall 5.
Cyanobacteria are the only bacteria that contain chlorophyll A, a chemical required for oxygenic photosynthesis the same process used by plants and algae 1, This process uses carbon dioxide, water and sunlight to produce oxygen and glucose sugars for energy. Chlorophyll A is used to capture the energy from sunlight to help this process.
Other bacteria can be considered photosynthesizing organisms, but they follow a different process known as bacterial photosynthesis, or anoxygenic photosynthesis This process uses bacteriochlorophyll instead of chlorophyll A These bacteria cells use carbon dioxide and hydrogen sulfide instead of water to manufacture sugars. Bacteria cannot use oxygen in photosynthesis, and therefore produce energy anaerobically without oxygen Cyanobacteria and other phytoplankton photosynthesize as plants do, and produce the same sugar and oxygen for use in cellular respiration.
In addition to chlorophyll A, blue-green algae also contain the pigments phycoerythrin and phycocyanin, which give the bacteria their bluish tint hence the name, blue-green algae Despite not having a nucleus, these microorganisms do contain an internal sac called a gas vacuole that helps them to float near the surface of the water Chlorophyll is a color pigment found in plants, algae and phytoplankton.
This molecule is used in photosynthesis, as a photoreceptor Photoreceptors absorb light energy, and chlorophyll specifically absorbs energy from sunlight Chlorophyll makes plants and algae appear green because it reflects the green wavelengths found in sunlight, while absorbing all other colors.
However, chlorophyll is not actually a single molecule. There are 6 different chlorophylls that have been identified 1, Chlorophyll A is the primary molecule responsible for photosynthesis 1, That means that chlorophyll A is found in every single photosynthesizing organism, from land plants to algae and cyanobacteria 1. The additional chlorophyll forms are accessory pigments, and are associated with different groups of plants and algae and play a role in their taxonomic confusion.
These other chlorophylls still absorb sunlight, and thus assist in photosynthesis As accessory pigments, they transfer any energy that they absorb to the primary chlorophyll A instead of directly participating in the process 1, Chlorophyll B is mainly found in land plants, aquatic plants and green algae 1. In most of these organisms, the ratio of chlorophyll A to chlorophyll B is Due to the presence of this molecule, some organizations will group the green algae into the Plant Kingdom.
Chlorophyll C is found in red algae, brown algae, and dinoflagellates This has lead to their classification under the Kingdom Chromista 4. Chlorophyll D is a minor pigment found in some red algae, while the rare Chlorophyll E has been found in yellow-green algae. Chlorophyll F was recently discovered in some cyanobacteria near Australia Each of these accessory pigments will strongly absorb different wavelengths, so their presence makes photosynthesis more efficient Chlorophyll is not the only photosynthetic pigment found in algae and phytoplankton.
There are also carotenoids,and phycobilins biliproteins. These accessory pigments are responsible for other organism colors, such as yellow, red, blue and brown.
Like chlorophylls B, C, D, E and F, these molecules improve light energy absorption, but they are not a primary part of photosynthesis. There are two phycobilins found in phytoplankton: phycoerythrin and phycocyanin. Phycoerythrin reflects red light, and can be found in red algae and cyanobacteria. Some algae will appear green despite the presence of these accessory pigments. Just as in plants, the chlorophyll in algae has a stronger relative absorption than the other molecules.
Like a dominant trait, the more intense, reflected green wavelengths can mask the other, less-reflected colors In green algae, chlorophyll is also found at a higher concentration relative to the accessory pigments.
When the accessory pigments are more concentrated such as in red algae, brown algae and cyanobacteria , the other colors can be seen Photosynthesis is the process by which organisms use sunlight to produce sugars for energy. Plants, algae and cyanobacteria all conduct oxygenic photosynthesis 1, That means they require carbon dioxide, water, and sunlight solar energy is collected by chlorophyll A. Plants and phytoplankton use these three ingredients to produce glucose sugar and oxygen.
This sugar is used in the metabolic processes of the organism, and the oxygen, produced as a byproduct, is essential to nearly all other life, underwater and on land 1, Phytoplankton drifting about below the surface of the water still carry out photosynthesis. This process can occur as long as enough light is available for the chlorophyll and other pigments to absorb. In the ocean, light can reach as far as m below the surface This region where sunlight can reach is known as the euphotic zone.
Phytoplankton and other algae can be found throughout this zone. As light is required for photosynthesis to occur, the amount of light available will affect this process. Photosynthetic production peaks during the day and declines after dark However, not all light can be used for photosynthesis.
Only the visible light range blue to red is considered photosynthetically active radiation 1. Ultraviolet light has too much energy for photosynthesis, and infrared light does not have enough. Within the visible light spectrum, chlorophyll strongly absorbs red and blue light while reflecting green light This is why phytoplankton, particularly cyanobacteria, can thrive at the bottom of the euphotic sunlit zone, where only blue light can reach.
As blue light is both high in energy and strongly absorbed by chlorophyll, it can be used effectively in photosynthesis. Turbidity, or the presence of suspended particles in the water, affects the amount of light that reaches into the water 1.
The more sediment and other particles in the water, the less light will be able to penetrate. With less light available, photosynthetic production will decrease. Water temperature will also affect photosynthesis rates 1. As a chemical reaction, photosynthesis is initiated and sped up by heat As photosynthesis production increases, so will phytoplankton reproduction rates This factors into the large, seasonal swings of phytoplankton populations However, the extent to which temperature affects photosynthesis in algae and cyanobacteria is dependent on the species.
For all phytoplankton, photosynthetic production will increase with the temperature, though each organism has a slightly different optimum temperature range 1.
When this optimum temperature is exceeded, photosynthetic activity will in turn be reduced. Too much heat will denature break down the enzymes used during the process, slowing down photosynthesis instead of speeding it up Microscopic phytoplankton play some of the biggest roles in climate control, oxygen supply and food production.
That process uses up carbon dioxide, which helps regulate CO2 levels in the atmosphere, and produces oxygen for other organisms to live Phytoplankton make up the foundation of the oceanic food web.
A food web is a complex net of organisms and food chains who-eats-who. To survive, every living thing needs organic carbon Phytoplankton produce their required sugar through photosynthesis. As they are able to produce their own energy with the help of light, they are considered autotrophic self-feeding. Phytoplankton and other autotrophs are called primary producers, and make up the bottom of the food web Phytoplankton are generally consumed by zooplankton and small marine organisms like krill.
These creatures are then consumed by larger marine organisms, such as fish 29, This chain continues up to apex predators, including sharks, polar bears and humans. During the photosynthetic process, phytoplankton produce oxygen as a byproduct.
Due to their vast and widespread populations, algae and cyanobacteria are responsible for approximately half of all the oxygen found in the ocean and in our atmosphere Thus oceanic lifeforms not only feed off the phytoplankton, but also require the dissolved oxygen they produce to live.
Seaweed reproduction can involve either exclusively sexual or asexual phases, while some species display an alternation of generations that involves both in succession. In the former, the seaweed produces gametes egg and sperm cells with a single set of chromosomes and, in the latter, spores containing two sets of chromosomes.
Some species can also reproduce asexually by fragmentation—that is, the blades shed small pieces that develop into completely independent organisms. The the red alga Porphyra , used for making Japanese nori, has a highly complex life cycle.
Asexual reproduction allows for fast propagation of the species but carries with it an inherent danger of limited genetic variation. Sexual reproduction ensures better genetic variation, but it leaves the species that depend on this method of reproduction with an enormous match-making problem, as the egg and sperm cells need to find each other in water that is often turbulent.
Some species solve the match-making problem by equipping the reproductive cells with light-sensitive eyespots or with flagella so that they can swim. Others make use of chemical substances, known as pheromones or sex attractants.
These are secreted and released by egg cells and serve to attract the sperm. Some species for example, the large seaweed masses in the Sargasso Sea secrete enormous quantities of slime, which ensures that the egg and sperm cells stick close to each other and do not go astray.
A newly discovered species of red seaweed is now named Porphyra migitae. The red alga Porphyra has an especially complicated life cycle, with a fascinating aspect that merits further discussion because of the interesting history associated with its discovery. It relates directly to the cultivation of Porphyra for the production of nori, which is especially widely used in Japanese cuisine—most familiarly, as for the wrapping for maki rolls See the recipe in the caption for the nori roll image below.
The blades used in nori production grow while the seaweed is in the generation that reproduces sexually, although the organism itself can actually develop asexually from spores. The blades produce egg cells and sperm cells. The egg cells remain on the blades, where they are fertilized by the sperm cells. The fertilized eggs can then form a new type of spores, which are released. These spores germinate into a calcium-boring filament stage that can grow in the shells of dead bivalves, such as oysters and clams, in the process developing spots that give the organism a pinkish sheen.
Until the s it was thought that this sexual stage was actually an entirely separate species of alga, given the name Conchocelis rosea. Without an understanding of the true life cycle, it was not possible to grow Porphyra effectively in aquaculture. No one knew where the spores for the fully grown Porphyra originated. This was the main reason for the recurring problems experienced by the Japanese seaweed fishers in their attempts to cultivate Porphyra in a predictable manner.
It was an English alga researcher, Dr. Kathleen Mary Drew-Baker, who discovered the secret of the sexual segment of the Porphyra life cycle. Drew-Baker was unaware of the difficulties of the seaweed fishers. Instead, she was preoccupied with shedding light on the mystery of why the species of laver Porphyra umbilicalis that grew around the coast of England seemed to disappear during the summer, reappearing again only toward the end of autumn.
She tried without success to germinate spores that she had collected. They would even grow on an eggshell. A few months later, the resulting small, roseate sprouts produced their own spores that, in turn, could germinate and develop into the well-known large purple laver.
Drew-Baker published her results in Shortly thereafter the Japanese phycologist Sokichi Segawa repeated her experiments using local varieties of Porphyra and found that they behaved in the same way as the English species. The mystery was solved and the results were quickly put to use in Japan. Drew-Baker died at a relatively young age in , apparently unaware that her curiosity and seminal research had laid the foundations for the development of the most valuable aquaculture industry in the world.
As in green plants, photosynthesis enables seaweeds to convert sunlight into chemical energy, which is then bound by the formation of the sugar glucose. The photosynthetic process uses up carbon dioxide, which is thereby removed from the water.
In addition, phosphorous, a variety of minerals, and especially nitrogen are required. Oxygen is formed as a by-product, dissolved in the water, and then released into the atmosphere. This by-product is of fundamental importance for those organisms that must, like humans, have oxygen to be able to breathe.
Photosynthesis can even, to a certain extent, be carried out when seaweeds are exposed to air and partially dehydrated. They now run Maine Coast Sea Vegetables, a company which has its own building and 20 employees who transform the locally harvested seaweeds into more than 20 different products.
The raw material for this business is delivered by about 60 seaweed harvesters who work along the coasts of Maine and Nova Scotia, where algae are found in abundance. Shep trains the harvesters himself. It is of utmost importance to him that they understand the principles of collecting the different types of marine algae sustainably so that they do the least harm to the environment. Maine Coast Sea Vegetables processes about 50 tons of dried seaweeds annually, of which about 60 percent is the dulse for which the company is especially famous.
Eating dulse is an old tradition in Maine, brought to its shores by settlers from Wales, Ireland, and Scotland. I have become a great fan of their applewood smoked dulse; I eat it as if it were candy. When dried dulse is brought to the factory, it is sorted by hand, and epiphytes, small crustaceans, and bivalves are picked off. The bone-dry dulse is placed in a sealed room to reabsorb some moisture and then left to ripen for a couple of weeks.
In tightly sealed packages, the chewy blades have a shelf life of about a year. During the night, when the light level is low, photosynthesis stops and the seaweeds begin to take in oxygen, burn glucose, and give off carbon dioxide. Under normal conditions, photosynthesis is the dominant process, allowing the seaweeds to build up their carbohydrate content.
To the extent that they have access to light in the water, seaweeds actually utilize sunlight more efficiently than terrestrial plants. Marine algae are a much better source of iron than foods such as spinach and egg yolks. The red macroalgae normally grow at the greatest depths, typically as far as 30 meters down, the green macroalgae thrive in shallow water, and the brown algae in between.
This distribution of species according to the depth of the water is somewhat imprecise, however; a given species can be found at a location where there are optimal conditions with respect to substrate, nutritional elements, temperature, and light. In exceptionally clear water, one can find seaweeds growing as far as meters below the surface of the sea.
It is said that the record is held by a calcareous red alga that was found at a depth of meters, where only 0. Even though the waters at that depth may appear pitch-dark to human eyes, there is still sufficient light to allow the alga to photosynthesize.
In turbid waters, seaweeds grow only in the top, well-lit layers of water, if at all. Formerly it was thought that seaweed species had adapted to their habitat by having pigments that were sensitive to the different wavelengths of the light spectrum.
In this way they could take advantage of precisely that part of the spectrum that penetrated to the depths at which they lived. For example, the blue and violet wavelengths reach greater depths.
The red algae that live in these waters must contain pigments that absorb blue and violet light and, as a consequence, appear to have the complementary color red. Experiments have since shown that this otherwise elegant relationship does not always hold true. Given that all the substances that seaweeds need in order to survive are dissolved in the water, macroalgae, unlike plants, have no need of roots, stems, or real leaves.
Nutrients and gases are exchanged directly across the surface of the seaweed by diffusion and active transport. In some species there is no meaningful differentiation, and each cell draws its supply of nutrients from the surrounding water. On the other hand, specialized cell types and tissues that assist in the distribution of nutrition within the organism can be found in a number of brown macroalgae.
Access to nitrogen is an important limiting factor in seaweed growth, particularly for green algae. The increasing runoff into the oceans of fertilizer-related nitrogen from fields and streams has created favorable conditions for the growth of algae, especially during the summer when it is warm and the days are long.
What is Seaweed 3. What is Seagrass 4. Similarities Between Seaweed and Seagrass 5. Seaweed is a large alga that belongs to Kingdom Protista. Some types of red algae, green algae and brown algae are seaweeds. They are simple and unspecialized structures. The thallus of seaweed has a stalk-like part stipe , a leaf-like part and a holdfast. Holdfast anchors the seaweed to a surface.
They extract nutrients from the water by diffusion. Seaweeds do not produce flowers or seeds. They reproduce via spores. Seaweeds are photosynthetic; hence, they do not need sunlight. They produce oxygen and contribute to capturing carbon dioxide. Moreover, seaweeds provide habitats for fisheries and other marine species. Some seaweeds are edible. Some are used as fertilizers.
Furthermore, some species are used as a source of polysaccharides. Seagrass is a flowering plant which grows in the marine environment. It is a vascular plant that has true stem, roots and leaves. Seagrasses have long green grass-like leaves. In fact, they are monocotyledons.
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