What is Algae?

Introduction

Wandering the rocky coasts of Maine at low tide you are likely to come across a mess of brownish green and red tendrils covering the shore. Ascophyllum nodosum (rockweed), Fucus spp. (bladderwrack), Chondrus crispus (Irish moss), Ulva lactuca (sea lettuce), and Saccharina latissima (sugar kelp) are several seaweeds that make up the base of coastal ecosystems in this region and are just a few of the roughly 22,900 species of macroalgae that can be found around the world.

Some Maine seaweeds in the wild!

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Ascophyllum nodosum

Drawing by Priscilla Fawcett. For more information about this species, see the Maine Seaweed Council website.

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Chondrus crispus

Drawing by Priscilla Fawcett. For more information about this species, see the Maine Seaweed Council website.

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Ulva lactuca

Drawing by Priscilla Fawcett. For more information about this species, see the Maine Seaweed Council website.

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Saccharina latissima

Drawing by Priscilla Fawcett. For more information about this species, see the Maine Seaweed Council website.

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Palmaria palmata

Drawing by Priscilla Fawcett. For more information about this species, see the Maine Seaweed Council website.

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Fucus spp.

Drawing by Priscilla Fawcett. For more information about this species, see the Maine Seaweed Council website.

What makes something ‘algae’?

Seaweeds– also called macroalgaeMarine plants that photosynthesize and reproduce with flowers, also known as seaweed.– are a group of multicellular algae that are usually visible without a microscope. AlgaeA simple, non-flowering, and typically aquatic plant of a large group that includes seaweeds and many single celled organisms. are a diverse group of aquatic primary producers that include macro- and microalga. They produce energy via photosynthesisProcess where plants use their chloroplasts to create food from water and carbon dioxide., which is the conversion of light energy into chemical energy using carbon dioxide and water. Algae are similar to plants in that they are autotrophsAn organism that can produce its own food using light, water, carbon dioxide, and other chemicals.: organisms that produce energy without consuming other organisms. Instead, algae and plants take up nutrients from their environment in the form of simple inorganic compoundsA chemical compound that does not contain carbon. (like CO2, H2O, NH3, NH4+, HPO4 2-, PO4 3-) and use these nutrients to grow, reproduce, and maintain a stable internal environment.

A video (2:47) about explaining photosynthesis (the process of converting sunlight, carbon dioxide, and water into carbohydrates and oxygen). Video Credit: RicochetScience. Available on YouTube: https://www.youtube.com/watch?v=zWO-bTi6u8M

However, despite their similarities to plants, algae are not plants. To start, algae have a different level of biological complexityHow complicated an organism is, which is directly related to that organism's ability to survive in its environment than plants; algae can be unicellular, multicellular, or colonial and can also be classified based on cellular complexity as prokaryotic or eukaryotic while plants are always multicellular and eukaryotic.

Cellular Complexity Explained

Unicellular, Multicellular, and Colonial

UnicellularAn organism with only one cell. organisms are made of a single cell that provides all of the necessary functions for survival. MulticellularAn organism that consists of more than one cell organisms consist of multiple cells that must grow together to perform the functions necessary for survival and cannot survive separately from the primary organism. ColonialSeveral individual organisms living together in close association organisms behave like multicellular organisms but are made up of unicellular organisms, meaning individual cells can survive separately from the primary organism.

 

Image credit: Armin Hallmann

Prokaryotic vs. Eukaryotic

ProkaryoticSingle-celled microorganisms that do not have a defined nucleus, and are considered to be the oldest organisms on Earth. cells are simple cells with only a few internal parts– or organelles– required to function and are always found as single-celled organisms. EukaryotesAny cell or organism that contains a clearly defined nucleus. are more complex cells with many internal structures that can be part of unicellular or multicellular organisms. Prokaryotes evolved before eukaryotes and contributed to the evolution of eukaryotes.

 

Image credit: How Stuff Works

Algae also lack a variety of physical features that are characteristic of plants such as roots, shoots, stems, leaves, and a vascular system. Instead of these structural features– which are key in helping plants to take up and transport nutrients – algae absorb nutrients from their environment through the tissue along their entire body. You might think about algae as nutrient sponges whereas plants are nutrient straws.

What do algae do in the environment?

Algae– and by extent seaweeds– play a crucial role in creating the conditions for life on earth as we know it. Every time we breathe in, 50 percent of the oxygen filling our lungs, entering our bloodstream, and powering our cells comes from algae– specifically phytoplankton. PhytoplanktonPlankton consisting of microscopic plants. are single-celled algae that live drifting in freshwater and marine environments.

In addition to providing oxygen, algae are also important in the carbon, nitrogen, and phosphorus cycles because they absorb large amounts of these nutrients from aquatic environments. This means that they help to control excess nutrient and carbon dioxide levels in the water, contributing to local reduction of eutrophicationExcessive nutrients in the water, usually due to runoff, that causes an increase in plant growth and kills animals due to a lack of oxygen. and ocean acidificationIncrease of the pH level in the ocean, primarily caused by the uptake of carbon dioxide from the atmosphere..

A video (1:16) providing an overview of the carbon cycle. Video Credit: NOAA. Available on YouTube: https://www.youtube.com/watch?v=0-DtXqr-gPQ

A video (8:52) about the role of seaweed in the carbon cycle, featuring Dr. Nichole Price from Bigelow Laboratory for Ocean Sciences. Video Credit: Maine Aquaculture Innovation Center. Available on YouTube: https://www.youtube.com/watch?v=r12pRMULu8U

How can algae be categorized?

One way to subdivide the massive group of organisms classified as ‘algae’ is to distinguish them by cellular structure. As we mentioned above, macroalgae are multicellular algae that are visible to humans without microscopes. (These are also commonly known as ‘seaweeds’). Most macroalgae are benthicFrom, relating to, or occuring on the bottom of a body of water., meaning they attach to the substrateA substance that an organism grows and lives on, or is supported by. in the body of water they grow in. Macroalgae that we most commonly think of are marine, living in saltwater or brackish water, although there are a few species that can live in freshwater such as filamentous green algae.

MicroalgaeMicroscopic single celled algae that are not visible to the naked eye, and typically live in fresh and salt water environments., on the other hand, can be unicellular, multicellular, or colonial and are abundant in saltwater and freshwater. Microalgae are often free floating and individual cells can only be seen with a microscope. In abundance, microalgae give rise to different coloration in the water – often greens, yellows, and browns – which can be observed to the naked eye. Both microalgae and macroalgae are primary producers in aquatic ecosystems, meaning they create chemical energy from light. However, microalgae tend to play the role of ‘food’ in these ecosystems while macroalgae are more commonly a structural element of aquatic environments and play the role of ‘habitat.’

A video (3:55) offering a basic explaination of what algae are. Video Credit: SAMS Marine Science. Available on YouTube: https://www.youtube.com/watch?v=BgMR2VaEVUo

A video (10:24) explaining the evolution of macroalgae and how algae have influenced Earth as we know it featuring phycologists Susan Brawley, P.h.D, and Jessie Mulin, P.h.D. Video Credit: Maine Aquaculture Innovation Center. Available on YouTube: https://www.youtube.com/watch?v=60DAcVHGyvQ&list=PLa6yzmcW1D9fLMWDQ4EUMRwBzCUXOyuLR&index=2

Within the categories of microalgae and macroalgae, there are many more groups that algae are further divided into based on the type of photosynthetic pigmentA pigment present in photosynthetic organisms that captures light energy needed for photosynthesis. they contain and the structure of their cells. Since this learning module focuses on farmed seaweeds, we will only cover the classification of macroalgae into three groups: brown, green, and red. These three types of macroalgae contain unique light-absorbing pigments, have distinct reproductive strategies, and evolved from separate biological lineagesA series of populations, organisms, cells, or genes connected by a continuous line of descent from parent to offspring..

Evolution of Macroalgae: Green, Red, and Brown Algae

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Green Algae (phylum Chlorophyta)

Green algae are characterized by their pigments: Chlorophyll a and Chlorophyll b which give them a bright, nearly-fluorescent green color. Common green algae species in Maine include Ulva lactuca (pictured), Ulva intestinalis, and Codium fragile. Currently, research is investigating the potential to farm green seaweeds in Maine, though very few are farmed globally.

Photo credit: Seaweed.ie

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Red Algae (phylum Rhodophyta)

Red algae are characterized by their pigments: Chlorophyll a, Chlorophyll d, and phycobilins. Phycobilins are the specialized pigment in red algae that creates red, orange, or bluish hues, which supplement the light capturing ability of chlorophyll and masks it. In the wild, red algae may appear dark red, purple, brown, or even green or iridescent in color as a result of these pigments. Common red algae species in Maine include Chondrus crispus (pictured), Palmaria palmata, and Porphyra umbilicalis. The market for these valuable red seaweeds in Maine is currently supplied through wild harvest, although there is significant farming of red seaweeds globally and interest in commercializing red algae in Maine.

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Brown Algae (class Phaeophyceae)

Brown algae are characterized by their pigments Chlorophyll a, Chlorophyll c, fucoxanthin, and xanthophylls. The specialized marine carotenoids in brown algae create brown and deep-olive hues and help some species absorb light in lower-light environments. Brown algae tend to be dark greenish-brown in color but may also appear yellow, green, or deep brown-black depending on lighting and their environment. Multiple native species of kelp– which are brown seaweeds– are farmed in Maine including Saccharina latissima (pictured), Alaria esculenta, and Laminaria digitata (although the latter species is only farmed by one farm currently).

Photo credit: BBC

Green algae (phylum Chlorophyta)

Green algae are characterized by their pigments: Chlorophyll a and Chlorophyll b which give them a bright, nearly-fluorescent green color. Common green algae species in Maine include Ulva lactuca (pictured), Ulva intestinalis, and Codium fragile. Currently, research is investigating the potential to farm green seaweeds in Maine, though very few are farmed globally.

 

Image credit: Seaweed.ie

Red Algae (phylum Rhodophyta)

Red algae are characterized by their pigments: Chlorophyll a, Chlorophyll d, and phycobilins. Phycobilins are the specialized pigment in red algae that creates red, orange, or bluish hues, which supplement the light capturing ability of chlorophyll and masks it. In the wild, red algae may appear dark red, purple, brown, or even green or iridescent in color as a result of these pigments. Common red algae species in Maine include Chondrus crispus (pictured), Palmaria palmata, and Porphyra umbilicalis. The market for these valuable red seaweeds in Maine is currently supplied through wild harvest, although there is significant farming of red seaweeds globally and interest in commercializing red algae in Maine.

Brown Algae (class Phaeophyceae)

Brown algae are characterized by their pigments Chlorophyll a, Chlorophyll c, fucoxanthin, and xanthophylls. The specialized marine carotenoids in brown algae create brown and deep-olive hues and help some species absorb light in lower-light environments. Brown algae tend to be dark greenish-brown in color but may also appear yellow, green, or deep brown-black depending on lighting and their environment. Multiple native species of kelp– which are brown seaweeds– are farmed in Maine including Saccharina latissima (pictured), Alaria esculenta, and Laminaria digitata (although the latter species is only farmed by one farm currently).

 

Image credit: BBC

Algae’s place in aquaculture

Globally, around 220 species of seaweed are farmed although nearly 95 percent of seaweed landings come from eight major species of red and brown algaes: Laminaria japonica, Eucheuma spp., Gracilaria spp., Undaria pinnatifida, Porphyra spp., Kappaphycus alvarezii, Sargassum fusiforme, and Eucheuma denticulatum.