Seagrass; Heroes of our Oceans
Are planting seagrass beds in our nearby oceans a convenient and sustainable way to slow down acidification in them (Increase pH)?
Based on the information I already know, I assume that we could use seagrass beds to slow down acidification in our local oceans (Oceans that surround Canada) by using the process of photosynthesis.
- In sexual reproduction, pollen is carried through the water to fertilize female plants
- In asexual reproduction (clonal growth), they shoot out rhizomes that sprout new growth which means one plant can produce a tuft of seagrasses.
For this to work, we will need to lower the amount of carbon dioxide we are putting in the atmosphere by switching to renewable resources and going green.
For this project, I used both primary and secondary data.
I read some pages of an eBook, online journals, emailed professors and used websties.
Ocean Acidification (OA)
What Is It?
- Acidification is the process in which a substance gradually decreases in pH over time. This means that the acids in the substance surpasses the bases (alkali) changing its pH. Therefore, ocean acidification is when the oceans lower in pH because the amount of carbon dioxide in our atmosphere is too much to be converted into oxygen by plant
- pH is a unit of measurement used to measure how acidic or basic (alkali) a substance is. Its scale ranges from 0 (acidic) to 14 (alkaline).
- 0-6.5 is acidic, 7 is neutral and 7.5-14 is alkaline.
- The pH of the oceans could drop from it's average 8.1 down to 7.8 in 2100. Though this may seem like a small change, this could have a big impact in our marine ecosystems and such.
- Acid rain
- Podzolization (Minerals from the upper layer of soil become acidic then leach into the lower layer of soil. This could enter ground water and flow into runoff streams)
- Atmospheric carbon dioxide levels increase and dissolve into the water. (Humans increase the levels, co2 dissolves on its own)
- Dry deposition of air pollutants. (Atmospheric gasses freely fall into our oceans from the atmosphere.)
- Wet deposition of air pollutants. (Atmospheric gasses mix with water in the atmosphere, then are washed out with precipitation and land in the ocean)
- Man Made
- Vehicle Emissions
- Burning of fossil fuels and Fossil fuel emissions
- Using nitrogen fertilizers. (Runoff water from fields with high levels of dissolved nitrogen and phosphorus may enter the water)
- Marine Life
- Reduces the amount of carbonate which is very needed for marine life.
- Makes it difficult for marine organisms to create their shells and skeletons and their existing shells may dissolve or lose their strength.
- Calcifying organisms might not be able to adapt to the rapid change of pH
- A more acidic environment will harm other marine species such as molluscs, corals and some kinds of plankton.
- Coral reefs will be more vulnerable to storm damage and slow the recovery rate.
- Marine organisms could also experience changes in growth, development and survival (Most species will be more vulnerable in their early life stages like how Juvenile fish may have trouble locating suitable habitat to live.)
- Some organisms affect by this:
- Sea butterflies
- Sea urchins
- This will affect the food we eat since most of our shellfish require calcium carbonate to form or to fortify their shells.
- We will loose coastal protection and some opportunities to new medicine (Medicines are being developed for cancer, arthritis, human bacterial infections, Alzheimer's disease, heart disease, viruses, and other diseases)
- Potential job losses through declining harvest and fishery revenues from shellfish.
- New Brunswick and Nova Scotia could see declines in resource accessibility.
- Prince Edward Island plus Newfoundland and Labrador are more vulnerable to losses in fisheries.
What is it?
- Seagrass is a flowering plant that is known to be as the Asteraceae family and is in the group called monocotyledons (This is where you would find lilies, grasses, palms etc)
- It is not a seaweed
- Has veins, roots, rhizomes, and produces flowers and seeds.
- Mostly found in salty and brackish water
- Deepest it can grow is 190ft
Why is this Plant Important?
- Acts like a home to some animals
- Provides food
- Stabilizes the sea bottom
- Maintains water qualities
- Seagrasses can tolerate various degrees of salinity
- They can tolerate temperatures ranging from minus 6 to 40 degrees C. (Coldest part of the ocean is -1.94C). If the temperature is higher or lower than it should be, it can change the pattern of sexual reproduction
- Seagrass responds to rising sea levels by spreading shore-wards into shallower water. The sediment it collects helps prevent erosion and slow the rate at which land area is lost to the sea.
- Their stems, called rhizomes, anchor the plant.
- Roots grow down from the rhizome to also anchor the plant to the seabed
- Flexible blades grow straight up and can bend to the current.
- Fast-growing grasses form a mat that traps sediment (solid material that settles at the bottom of a liquid) and stabilizes the seabed, allowing taller, slower-growing varieties to establish roots.
- Flowers that carry pollen and seeds.
How does Seagrass Photosynthesize?
- Like most plants, seagrass needs sunlight to grow and photosynthesize (Even in the ocean, sunlight still penetrates it for about 600ft. This is known as the sunlight zone)
- Special cells within the seagrass, called chloroplasts use the sun's energy to convert carbon dioxide and water into sugar and oxygen for growth through the process of photosynthesis. Veins transport nutrients and water throughout the plant, and have little air pockets called lacunae that help keep the leaves buoyant and exchange oxygen and carbon dioxide throughout the plant.
- Like other flowering plants, their roots can absorb nutrients.
- Seagrass reproduces in 2 ways:
- Asexual Reproduction
- Send out rhizome roots that can grow new plants, so a single plant is capable of producing an entire underwater meadow.
- Or a rhizome root could detach and land on the sand then begin it’s growth.
- Seagrass can also break a propagule which will begin to grow into a new plant
- This is known as clonal growth.
- Sexual Reproduction
- Pollen is carried through the water to fertilize female flowers.
- Or seagrass can send out a fruit that will bring out a seed which will sink when it is a week old.
- Then it will anchor unto sand and fiber and begin its growth.
How can Seagrass Help with OA
- A single square meter of seagrass can produce ten litres of oxygen per day
- This plant is photosynthetically productive; Seagrass can absorb huge amounts of carbon from the atmosphere.
- Each square metre of seagrass can absorb 83 grams of carbon per year
- Seagrass meadows hold 15% of the oceans carbon but only make up only 0.1% of the ocean floor.
- If a plant dies, the leaves sink to the seabed and decay. The carbon trapped inside the leaves and rhizomes of the seagrass will become buried by sediment, and trapped - that is if it has not been tampered with.
An Endangered Plant
- We are losing an acre of seagrass habitat every 30 seconds and an estimated 29% of seagrass meadows have disappeared over the past century.
- Seagrass is endangered. Here are some of its threats:
- Natural Threats
- Climate change due to global warming threatens both marine and terrestrial ecosystems. Storms, earthquakes and tsunamis can rip up seagrass fields and fill the water with mud and debris.
- High levels of plant nutrients. High nutrient levels, often due to agricultural and urban runoff, cause algae blooms that shade the seagrass. Reduction in light decreases seagrass growth and can kill whole populations.
- Man Made Threats
- Global warming
- Sewage, oil spills and agricultural and industrial waste pollute the water and make it murky.
- Seagrass needs clear, sunlit water for photosynthesis. Without it, the plants die and rot, resulting in more greenhouse gases, as well as loss of habitat for the other plants and animals that depend on the grass.
- Coastal development; dredging harbors and building seawalls and jetties can destroy seagrass meadows and disrupt currents.
- Boat propellers can also tear up seagrass, leaving deep scars.
How to Protect this plant
- Prevent damage to seagrass meadows
- Create protected areas of seagrass
- Reduce overfishing
- Reduce stress from coastal development
Q and A with Professors
- For an opinion on my theory, I decided to contact Prof. Kim Juniper, a professor in Marine Sciences in the University of Victoria and Prof. Nancy WIlliams from the Marine Sciences department at the University of South Florida.
- Professor Kim Juniper's reply:
- Interesting question. All plants can help reduce global atmospheric CO2 by fixing it into biomass, and this will eventually help reduce acidification caused by atmospheric CO2 dissolving in the oceans. However, this global effect does not scale down very well. Planting seagrass beds in one of our local oceans is unlikely to have much of a local effect on acidification because CO2 usually enters oceans from the atmosphere faster than it can be removed by the seagrass.
- Professor Nancy Williams' reply:
- I do think that this strategy of using seagrass to create local OA refugia locally can be a short-term solution, but I do not see it as a long-term solution to OA. These plants eventually die and break down and their carbon is released back into the water, so the storage of carbon is not forever, and we still need to work to reduce anthropogenic CO2 emissions...
To show how seagrass takes in carbon dioxide and converts it into oxygen underwater, I am going to use a demonstration. In this demonstration, I am going to use aquatic plants Java Fern (Microsorum pteropus) and Gulf Swampweed (Hygrophila costata) as alternatives to seagrass.
Microsorum pteropus (Java Fern)
Hygrophila costata (Gulf Swampweed)
Three 0.8-Gallon Tanks
2 with plants
Sea gravel (optional)
Temp of water and carbonic acid
Amount of water and carbonic acid
Size of tubs
Time the tubs are left out
Amount of light each tub gets
2 tanks have a plant, the other does not
pH of the water.
Wash each tank
Fill each tank with 1L of lukewarm water.
Pour in 1L of carbonated water (carbonic acid) and mix.
Put sea gravel at the bottom of the tank (sea gravel is not needed for this experiment. It only keeps the plant in place)
Put a plant in one of the tanks and put the second one in a different one.
Leave one tank with no plant (Control)
Record the pH of the water for each tank
Put each tank under a grow light and leave overnight for a week after that night
Every night at 8:30, record the pH of each tank
Put the information gathered into a graph and table
|Days Left Out||Microsorum pteropus (Java Fern)||Hygrophila costata (Gulf Swampweed)||
Control (No Plant)
And I transferred this data to a line graph.
Analysis and Conclusion
In conclusion, I found out that my hypothesis was right and wrong at the same time. Planting seagrass beds in our local oceans can be a way to slow down ocean acidification because they take in a good amount of carbon dioxide (83 grams per square metre) and convert it into oxygen even though they only make 0.1% of the ocean.
Even if this could work, seagrass is becoming endangered and if they were only to remain untouched and untampered with, this could actually work.
For this to succeed, we will need to reduce anthropogenic carbon emissions first, then save seagrass. Without us doing so, this could only be a short term solution to this global problem.
- If I could continue my project, I would begin to look at this at a larger scale by looking at all the oceans. I would find out if a specific type of seagrass is invasive and how it will affect OA and organisms in the ocean.
- I would like to research other plants that take in large amounts of carbon dioxide and look at the pros and cons of that.
- I would also like to look for land based options to slow down ocean acidification and how realistic this plant would be.
National Oceanic and Atmospheric Administration. “Ocean Acidification.” April 2020,
Raunek. “Effects of Ocean Acidification on Marine and Human Life.” 24 December 2019,
“World Meteorological Organization.” Atmospheric Deposition, © 2021 World Meteorological Organization (WMO),
The National Academies Press. Ocean Acidification: A National Strategy to Meet the Challenges of a Changing Ocean. A National Strategy to Meet the Challenges of a Changing Ocean,
Stone, Debbi, and Kevin Van Dien. “How are humans causing ocean acidification?” Climate Interpreter,
“Ocean Acidification and it's Effects.” 27 April 2018,
Gill, Laura. “Jeopardy at Sea: What Atoms in Clams Tell us about Ocean Acidification.” 27 November 2018,
SMITHSONIAN OCEAN. “Farming Oysters Despite Acidic Seas.”
Samarrai, Fariss. “OCEAN ACIDIFICATION MAY REDUCE SEA SCALLOP FISHERIES.”
Chelsea Leu, Dissolving brittle stars hint at implications of ocean acidification, 15 August 2018,
Wilson, Tyler J. “Potential socioeconomic impacts from ocean acidification and climate change effects on Atlantic Canadian fisheries.” 20 January 2020,
Woods Hole Oceanographic Institution. “Ocean Acidification.”
- U.S. Geological Survey. “pH and Water".
- Britanica. "pH".
- Frontiers. "Secret Gardens Under the Sea: What are Seagrass Meadows and Why are They Important?" 1 February 2018
SMITHSONIAN OCEAN. "What Are Seagrasses? A Plant, Not A Seaweed"
- GLOBAL SEAGRASS OBSERVING NETWORK. "Seagrass",
- Give Canada "THE IMPORTANCE OF SEAGRASS: WHY WE SHOULD CONSERVE THIS MARINE HABITAT",
- The Order of Underwater Coral Heroes "Seagrass Beds",
- AIMS "Seagrass"
- Laura Guerrero-Meseguer "Understanding the sexual recruitment of one of the oldest and largest organisms on Earth, the seagrass Posidonia oceanica"
Pictures (Used in Slide)
I would like to thank:
Both Prof. Kim Juniper and Nancy Williams for feedback on my project
My teacher, Mrs Tara Hobart for great advice
My parents for helping me through the way.