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Seaweed Facts & Worksheets

Seaweed is an umbrella term used to describe a variety of marine algae. It comes in a range of shapes and sizes, from small bacterial strands up to large kelp plants.

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Seaweed accumulates in shallow water or on rocky shores and frequently forms dense growths. Many exhibit a clearly defined zonation around the coasts of the oceans, specifically in areas where the depth of the water is less than 50 meters (or approximately 165 feet). There are several types of seaweed that humans can consume, many of which also have commercial value.

See the fact file below for more information on Seaweed, or you can download our 32-page Seaweed worksheet pack to utilize within the classroom or home environment.

Key Facts & Information

What is seaweed?

  • Holdfasts, which resemble roots and serve the primary purpose of attachment, are typically what keep seaweeds attached to the ocean floor or other solid structures. Unlike other plants’ roots, holdfasts do not draw in nutrients from the soil. 
  • The varieties of seaweed that grow at the high-water mark, where the plants are frequently exposed to air, are distinct from the types of seaweed that grow at lower levels when the plants receive little to no exposure to stand.
  • Some are utilized in producing fertilizers, while others serve as sources of polysaccharides.

Seaweed Anatomy

  • Seaweed looks like land plants that don’t have woody stems. It has the following parts:
  • Thallus: algal body
  • Lamina or blade: A flat structure that looks a bit like a leaf. Spore cluster pneumatocyst, or air bladder: an organ on the blade that helps it float.
  • Between the lamina and the stem is an organ that helps the kelp float.
  • Stipe: stem-like structure, may be absent
  • Holdfast: a base structure that sticks to a surface.
  • Haptera: a finger-like extension of the holdfast that anchors to a benthic substrate
  • The frond is made up of the stipe and the blade.

Taxonomy 

  • The term “seaweed” does not have a precise definition, although it is usually understood to refer to plants that are found in the ocean and may be observed with the naked eye. 
  • Both more extensive marine algae and flowering plants that grow at the bottom of the sea, such as eelgrass, are included in the scope of this word. 

Taxonomy 

  • In most cases, it belongs to one of several types of multicellular algae, including the brown, green, or red variety.
  • Due to the absence of a multicellular parent in their lineage, they are classified as a polyphyletic group.
  • In addition, cyanobacteria, often known as blue-green algae, are sometimes considered in seaweed research.
  • There is still some debate among scientists over the total number of seaweed species. However, there are likely several thousand different types.

Ecology 

  • Two environmental needs mostly determine the ecology of seaweed. 
  • These include ocean, or at the very least, brackish water, as well as adequate light for photosynthesis to take place.
  • Another critical factor is the presence of an attachment site; hence, seaweed is found in the littoral zone (nearshore seas) and, within that zone, on rocky coasts more frequently than on sand or shingle beaches.
  • In addition, a few species, such as Sargassum and Gracilaria, do not live anchored to the sea floor but instead float freely in the water.
  • There are many different ecological roles that seaweed plays. At the surface, they are merely wetted by the tops of sea spray, but certain species are known to attach themselves to a substrate that is several meters deep.
  • In certain locations, colonies of littoral seaweed can extend for miles into the ocean.
  • Some types of red algae are the deepest-living seaweed. Others have developed the ability to survive in the rock pools created by the tides. In this environment, seaweed must be able to tolerate abrupt shifts in temperature and salinity, as well as the infrequent occurrence of drying out.
  • Macroalgal debris is a food source for benthic creatures because they shed old fronds. Benthos along the shore use these macroalgal fronds. Pneumatocysts (gas-filled “bubbles”) can float macroalgae thallus when wind transports fronds.
  • Macroalgae fronds that drift offshore into deep ocean basins and sink without being remineralized can sequester carbon in the ocean.
  • The significance of this process for the storage of blue carbon is a topic of discussion among scientists.
  • Applications: There are many applications for seaweed, which is why it is either cultivated or collected wild.

Edible seaweed

  • It is common practice to eat seaweed in many parts of the world, including East Asia (including Japan, China, Korea, and Taiwan), Southeast Asia (including Thailand, Singapore, Brunei, Burma, Indonesia, Vietnam, Cambodia, the Philippines, and Malaysia), South Africa, Belize, Peru, South West England, the Canadian Maritimes, Scandinavia, Chile, Ireland, Wales, Hawaii, and California, and Scotland.
  • Gim (Korean), nori (Japanese), and zicai (Chinese) are all names for sheets of dried Porphyra that can be found in soups, sushi, and onigiri (rice balls). 
  • Along with Kappaphycus and Gigartinoid seaweed, Chondrus crispus, sometimes known as “Irish moss” or carrageenan moss, is utilized in the production of food additives.
  • Laverbread is traditionally made with Porphyra in Wales (sometimes with oat flour).
  • The dessert known as “dulce” is usually prepared in northern Belize by combining seaweed, milk, nutmeg, cinnamon, and vanilla (“sweet”).
  • Hydrocolloids and phycocolloids are two names that are used interchangeably to refer to gelatinous seaweed products, including alginate, agar, and carrageenan.
  • Food additives are known as hydrocolloids. 
  • The food business uses gelling, water-retaining, and emulsifying qualities, amongst other physical characteristics. 
  • Agar is an ingredient that can be seen in a variety of meals, including confectionary, goods made with meat and poultry, desserts, beverages, and foods that have been molded. 
  • Carrageenan is a preservative used in meals, including meat and fish, dairy products, and baked goods. It is also used in salad dressings and sauces, as well as dietetic foods.

Uses of seaweeds as medicinal plants 

  • Alginates find their most common application in wound dressings (for more information, see alginate dressing) and dental molds.
  • Agar is frequently utilized in the field of microbiology as a culture medium. 
  • Applications in biomedicine can be found for macroalgal polysaccharides such as carrageenans, alginates, and agaroses, amongst others.
  • It’s possible that Delisea pulchra will prevent bacteria from colonizing. 
  • Some DNA- and RNA-enveloped viruses can be stopped by the sulfated saccharides found in red and green algae.
  • Some diet pills contain seaweed extract as an ingredient.
  • Other seaweed tablets achieve the same effect as gastric bands by expanding in the stomach to give the impression that there is more food than there actually is.

Reducing the impact of climate change

  • The potential for large-scale seaweed growing in the open ocean to operate as a type of carbon sequestration and reduce the effects of climate change has received much attention in recent years.
  • Several academic studies have shown that nearshore seaweed forests are a source of blue carbon. 
  • This is due to the fact that wave currents transport debris from seaweed into the center and deep ocean, where it stores carbon.
  • In addition, nothing on earth is capable of sequestering carbon at a faster pace than Macrocystis pyrifera, better known as giant kelp. 
  • This particular species of kelp may grow at a rate of up to 50 centimeters per day and can reach a length of up to 60 meters if the right conditions are present.
  • It has consequently been hypothesized that cultivating seaweeds on a large scale may have the potential to have a significant effect on climate change.
  • One study concluded that reforesting just 9% of the world’s oceans with kelp forests “could provide enough biomethane to supply all of today’s fossil fuel energy needs while reducing 53 billion tons of CO2 per year, restoring pre-industrial levels.”

Other uses of seaweeds

  • Other types of seaweed can be buried in coastal dunes and utilized as a form of erosion control or as a fertilizer, compost, or other material for landscaping purposes.
  • The use of seaweed as a possible source of bioethanol is currently being investigated.
  • After being removed from the top of the algae scrubber/cultivator, the seaweed is either thrown away, put to use as food or fertilizer, or used topically as a skin care product.
  • In the industrial sector, alginates are used to produce various products and processes, including paper sizing, textile printing, hydro-mulching, explosives, adhesives, gels, dyes, and explosives. 
  • Seaweed can be found in various products, including toothpaste, cosmetics, and paint. The manufacturing of bio yarn often involves the usage of seaweed (a textile).
  • Through the process of biorefining, it is possible to extract some of these resources from seaweed.
  • The process of harvesting seaweed entails gathering, drying, and pressing various types of seaweed. It was a well-liked activity throughout the Victorian era and continues to be a hobby in modern times. Every day, seaweed is gathered to sustain communities in some developing countries.
  • Tanzanians grow “Mwani” (seaweed in Swahili). The farms are constructed up of little sticks that are arranged in precise rows in the warm water that is shallow. Once the seaweed has been harvested, it is utilized for a variety of things, including food, cosmetics, and even textiles.
  • On the Danish island of Laes, dwellings are occasionally constructed with roofs made of seaweed.
  • Many types of seaweed are fed to animals. In Northern Europe, sheep, horses, and cattle have traditionally grazed on these grasses.
  • The addition of seaweed to the diet of livestock has been shown to reduce methane emissions from cattle significantly.

Potential Health Hazard

  • Seaweed that has started to rot is a significant contributor of hydrogen sulfide, an extremely poisonous gas. 
  • Its presence has been linked to certain cases of what appears to be hydrogen sulfide poisoning.
  • It is possible for it to cause sickness and diarrhea.
  • Microcoleus lyngbyaceus, often known as “stinging seaweed,” is a filamentous cyanobacterium that includes toxins such as lyngbyatoxin-a and debromoaplysiatoxin. 
  • These cyanobacteria are also known as “stinging seaweed.” Seaweed dermatitis, which can be caused by direct contact with the skin, is characterized by itchy, burning sores that can continue for days. 

Threats 

  • Bacterial disease: The red seaweed known as Kappaphycus becomes infected with ice-ice disease, which causes its branches to turn white. 
  • The Philippines, Tanzania, and Mozambique suffered significant crop losses due to the illness.
  • In several locations, kelp forests have been displaced by sea urchin barrens. They are “virtually impervious to famine,” according to the research. 
  • Their jaws and teeth increase when they are under the pressure of hunger, and they form groups called “fronts” to search for food together.

Seaweed Worksheets

This fantastic bundle includes everything you need to know about Seaweed across 32 in-depth pages. These ready-to-use worksheets are perfect for teaching kids about Seaweed, an umbrella term used to describe a variety of marine algae. It comes in a range of shapes and sizes, from small bacterial strands up to large kelp plants.

Complete List of Included Worksheets

Below is a list of all the worksheets included in this document.

  • Seaweed Facts
  • Spot in the Product
  • Kelp in Mind 
  • Weeds in the Sea
  • Support Your Answer
  • Fill Me In
  • Unique Me
  • Oh My Dish 
  • Risk and Benefits
  • What an Amazing Weeds
  • Journal 

Frequently Asked Questions

What is seaweed?

Seaweed is a type of marine plant that grows in the ocean.

What are the different types of seaweed?

There are three main groups of seaweed: brown, red, and green. Brown seaweed is the most common, and includes species such as kelp and rockweed. Red seaweed includes species such as dulse and Irish moss. Green seaweed includes species such as sea lettuce and sea grapes.

What are the benefits of seaweed?

Seaweed is a rich source of nutrients, including iodine, vitamins, and minerals. Seaweed is also used in various medicinal and cosmetic products.

How is seaweed used in cooking?

Seaweed is commonly used in sushi, soups, salads, and other dishes. It can also be used as a seasoning or a wrap for other ingredients.

How does seaweed grow?

Seaweed grows in the ocean, anchored to rocks, coral or other hard surfaces. Seaweed growth is affected by factors such as light, temperature, and the presence of nutrients in the water.

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Link will appear as Seaweed Facts & Worksheets: https://kidskonnect.com - KidsKonnect, January 17, 2023

Use With Any Curriculum

These worksheets have been specifically designed for use with any international curriculum. You can use these worksheets as-is, or edit them using Google Slides to make them more specific to your own student ability levels and curriculum standards.

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