Seagrasses | Ecology In Action

Summary

Seagrass meadows, underwater ecosystems rich in biodiversity, play a crucial role in marine life support, water filtration, and carbon sequestration. They act as nurseries for fish and help in coastal protection. Despite their importance, seagrasses face threats from pollution and destructive fishing practices. Urgent conservation and restoration efforts are needed to preserve these vital ecosystems.

Takeaways

• 🌿 Seagrasses are marine plants that form dense underwater meadows, providing one of the most productive and valuable ecosystems on Earth.
• 🌱 They have a long evolutionary history, descending from flowering land plants that returned to water over 75 million years ago.
• 🌊 Seagrass meadows thrive in shallow coastal waters with the right combination of water quality, light, and depth.
• 🐢 They support a diverse range of marine life, including endangered species like seahorses, turtles, sharks, and stingrays.
• 🌱 Seagrass meadows act as natural filters, enhancing water quality by stabilizing heavy metals and pollutants, and absorbing bacteria and excess nutrients.
• 💨 They produce vast quantities of oxygen through photosynthesis, enriching the water column and sediment for the species that live there.
• 🐟 They serve as important nurseries for coral reef animals and commercially valuable fish species, including the second most important catch fish, Alaska pollock.
• 🌳 Seagrasses contribute significantly to 'blue carbon', removing carbon dioxide from the atmosphere and storing it in marine sediments.
• 🌍 Seagrass prairies account for over 10% of the ocean's total carbon absorption per hectare, holding twice as much carbon as rainforests.
• 🌊 They are ecosystem engineers that alter the landscape, slowing water currents, building up the seafloor, and protecting coastal settlements from storm surges.
• ⚠️ Seagrasses are under threat from fishing practices, pollution, and coastal development, with an area the size of two football fields lost every hour.

Q & A

What are seagrasses and where do they typically form?

Seagrasses are marine plants that form dense underwater meadows, typically found in shallow coastal waters on continental shelves.

How long have seagrasses been evolving?

Seagrasses have a long evolutionary history, descending from flowering land plants that returned to the water over 75 million years ago.

How many species of seagrasses are there and what are the four main lineages?

There are 60 species of seagrasses spread across four main lineages, although the specific lineages are not named in the script.

What kind of marine life depends on seagrass meadows for their habitat?

Seagrass meadows support a diverse range of marine life including marine reptiles, mammals, invertebrates, endangered species such as seahorses, green turtles, sharks, and stingrays.

How do seagrasses contribute to water quality?

Seagrasses enhance water quality by stabilizing heavy metals and pollutants, absorbing bacteria, and excess nutrients.

What is the role of seagrass meadows in oxygen production?

As they photosynthesize, seagrasses produce vast quantities of oxygen, enriching the water column and the sediment for the species that dwell there.

How do seagrass meadows support fisheries and coral reefs?

Seagrass meadows serve as important nurseries for coral reef animals and commercially valuable fish species, including the world's second most important catch fish, the Alaska pollock.

What is blue carbon and how does it relate to seagrasses?

Blue carbon refers to the carbon dioxide removed from the atmosphere by marine ecosystems. Seagrass prairies, despite covering only 0.1 percent of the ocean floor area, account for over 10 percent of the ocean's total carbon absorption per hectare.

How much carbon do seagrasses bury each year?

Seagrasses bury 27 million tons of carbon each year.

What benefits do seagrasses provide in terms of coastal protection?

Seagrasses act as ecosystem engineers, altering the landscape to slow down water currents, building up the seafloor, and forming shallow offshore banks that shield coastal settlements from storm surges and high waves.

What are the main threats to seagrass meadows?

The main threats to seagrass meadows include fishing practices that uproot the grasses, pollution from land and coastal development, nutrient runoff that fuels algal blooms blocking sunlight, and overfishing of top predators.

How much seagrass meadow area is lost each hour and what is being done to restore it?

An area the size of two football fields of seagrass meadows is lost each hour. Efforts to restore them include replanting using cuttings from donor meadows in artificial sandbags, and researchers are developing new planting methods and seed banks.

Outlines

00:00

🌿 Seagrass Ecosystems: Nature's Carbon Sinks

Seagrasses are marine plants that form dense underwater meadows, which are incredibly productive and valuable ecosystems. They have a long evolutionary history, descending from land plants that returned to water over 75 million years ago. These grasses thrive in shallow coastal waters where they provide a perfect habitat for a diverse range of marine life, including endangered species. Seagrass meadows offer a multitude of ecosystem services, such as supporting marine herbivores, enhancing water quality by stabilizing heavy metals and pollutants, and producing oxygen. They also serve as important nurseries for coral reef animals and commercially valuable fish species. Seagrasses are particularly notable for their role in carbon sequestration, known as 'blue carbon'. Despite covering only 0.1% of the ocean floor, they account for over 10% of the ocean's carbon absorption per hectare, storing twice as much carbon as rainforests. They bury 27 million tons of carbon annually, locking it away under the sediment through their root systems. However, seagrass meadows are under threat from fishing practices, pollution, and coastal development, leading to a loss of these vital ecosystems.

05:02

🌊 The Plight of Seagrass Meadows

Seagrass meadows are facing significant threats in the 21st century, including damage from fishing practices and pollution. The pollution, particularly from land and coastal development runoff, introduces nutrients like nitrogen and phosphorus into the seas, which are toxic to the grasses and lead to algal blooms that block sunlight, halting photosynthesis and causing the ecosystem to collapse. Overfishing of top predators also disrupts the balance, as it reduces the control of grazing species that help maintain the health of the prairies. Despite efforts to regrow seagrass meadows using cuttings and artificial methods, restoration is challenging, expensive, and labor-intensive. It is clear that the focus should be on protecting existing seagrass prairies, as they are crucial tools in combating global climate change. The loss of seagrass meadows could have severe consequences for both the marine ecosystem and global food security.

Keywords

💡Seagrasses

Seagrasses are marine plants that form dense underwater meadows. They are crucial for the health of coastal ecosystems and are among the most productive and valuable ecosystems on Earth. In the video, seagrasses are described as having a long evolutionary history, with their lineage tracing back to flowering land plants that returned to water over 75 million years ago. They play a vital role in supporting marine life, enhancing water quality, and acting as carbon sinks.

💡Ecosystem Services

Ecosystem services refer to the benefits humans obtain from ecosystems. The video highlights the immense range of services seagrass meadows provide, such as supporting marine life, enhancing water quality by stabilizing heavy metals and pollutants, and producing oxygen. These services are essential for maintaining biodiversity and supporting human activities like fishing.

💡Blue Carbon

Blue carbon is the carbon dioxide removed from the atmosphere by marine ecosystems. Seagrass prairies, despite covering only a small fraction of the ocean floor, account for over 10% of the ocean's total carbon absorption per hectare. The video emphasizes the importance of seagrasses in carbon sequestration, as they bury carbon in their roots and rhizomes, locking it away in marine sediments.

💡Nurseries

The term 'nursery' in the context of the video refers to the role seagrass meadows play as critical habitats for the young of many commercially valuable fish species and coral reef animals. These underwater meadows provide a safe and abundant food source for juvenile marine life, emphasizing their importance in supporting global fisheries.

💡Coral Reefs

Coral reefs are ecosystems composed of countless coral polyps. The video mentions that seagrass meadows are important nurseries for coral reef animals, indicating the interconnectedness of these two ecosystems. Healthy seagrass meadows contribute to the health of coral reefs by providing a habitat for young reef species.

💡Food Security

Food security implies that people have access to enough food for an active, healthy life. The video points out that seagrass savannas support commercially valuable fish species, which are crucial for global food security. The health of seagrass meadows is directly linked to the availability of fish resources.

💡Ecosystem Engineers

Ecosystem engineers are organisms that create or modify habitats. Seagrasses are described as such because they alter the landscape around them by slowing down water currents, causing sediment to drop and build up the seafloor. This process forms shallow offshore banks that protect coastal areas from erosion and storm surges.

💡Carbon Sequestration

Carbon sequestration is the process of capturing and storing carbon dioxide to mitigate climate change. Seagrasses are highlighted in the video as efficient carbon sequestrators, capable of burying 27 million tons of carbon each year. This process is vital for combating global warming.

💡Pollution

Pollution refers to the presence of substances or things causing harm or undesirable effects. The video discusses how pollution from land and coastal development poses a significant threat to seagrass meadows. Nutrients like nitrogen and phosphorus, when they runoff into the seas, can be toxic to seagrasses and lead to algal blooms that block sunlight, hindering photosynthesis.

💡Overfishing

Overfishing is the practice of catching fish at a rate faster than they can reproduce. The video mentions that overfishing of top predators like sharks reduces the control of grazing species, which can lead to the degradation of seagrass meadows. This highlights the importance of sustainable fishing practices for maintaining the balance of marine ecosystems.

💡Restoration

Restoration refers to the process of repairing or returning a damaged ecosystem to its natural state. The video discusses the challenges of restoring seagrass meadows, which include the expense and labor intensity of the process. It emphasizes the need for protection of existing seagrass prairies over restoration efforts due to the superior ability of seagrasses to naturally regenerate.

Highlights

Seagrasses form dense underwater meadows that are highly productive and valuable ecosystems.

They have a long evolutionary history, descending from flowering land plants over 75 million years ago.

Seagrass meadows are found in shallow coastal waters on continental shelves.

There are 60 species of seagrass spread across four main lineages.

Seagrass meadows support a diverse range of marine herbivores.

Endangered species like seahorses, green turtles, sharks, and stingrays inhabit these ecosystems.

Seagrass meadows act as a natural filter, enhancing water quality by stabilizing pollutants.

They produce vast quantities of oxygen, enriching the water column and sediment.

Seagrass meadows are important nurseries for coral reef animals and commercially valuable fish species.

Seagrass savannas support both coral reefs and global food security.

Seagrasses are a significant source of 'blue carbon', removing CO2 from the atmosphere.

Seagrass prairies account for over 10% of the ocean's total carbon absorption per hectare.

They bury 27 million tons of carbon each year.

Seagrass meadows store nearly 20 billion tons of organic carbon globally.

Seagrasses are ecosystem engineers, altering the landscape around them.

They slow down water currents, building up the seafloor and forming shallow offshore banks.

Seagrasses protect coastal settlements from storm surges and high waves.

Pollution and runoff from coastal development pose the greatest threat to seagrass meadows.

Seagrass restoration is expensive and labor-intensive, making protection of existing meadows a priority.

Seagrass prairies are crucial tools to combat global climate change and must be protected.

Transcripts

hey

[Music]

seagrasses are marine plants that form

dense underwater meadows which are among

the most productive and valuable

ecosystems on earth these grasses have a

long evolutionary history they descend

from flowering land plants which

returned to the water over 75 million

years ago

their meadows form in shallow coastal

waters on continental shelves

they are a diverse group with 60 species

spread across four main lineages but

only the coasts provide their specific

habitat needs a perfect combination of

water quality light availability and

shallow depth the sheer range of

ecosystem services that these grasslands

provide is immense

they support an entire guild of marine

herbivores from marine reptiles to

mammals to invertebrates all graze the

submarine meadows

and endangered species such as seahorses

green turtles sharks and stingrays all

call this habitat home

and the huge prairies act as a natural

filter enhancing water quality by

stabilizing heavy metals and pollutants

absorbing bacteria and excess nutrient

and because sea grass is

photosynthesized they produce vast

quantities of oxygen enriching the water

column and the sediment for the myriad

species which dwell there these

underwater grasslands are important

nurseries for coral reef animals and for

commercially valuable fish species half

of all global fisheries exploit species

whose young grow in the sea grass

meadows including the world's second

most important catch fish the alaska

pollock the seagrass savannas support

both coral reefs and global food

security

if we lose them we stand to lose both

the reefs

and the fisheries too

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but perhaps the greatest asset that

seagrasses provide concerns blue carbon

blue carbon is the name for all the

carbon dioxide removed from the

atmosphere by marine ecosystems they may

cover only 0.1 percent of the ocean

floors area but seagrass prairies

account for over 10 percent of the

ocean's total carbon absorption per

hectare they hold twice as much carbon

as rainforests

burying 27 million tons of carbon each

year

this incredible process has its roots in

roots

unlike seaweeds sea grasses have roots

and rhizome systems which absorb carbon

and lock it away under the sediment

and because they grow using

photosynthesis

they use the sun's energy to convert the

carbon dioxide and water

into carbohydrates and oxygen

unlike carbon stored in forest soils on

land which can be released by forest

fires or deforestation

marine sediments are anoxic with low

microbial activity

meaning organic carbon can be

continually stored away for thousands

upon thousands of years

globally the seagrass meadows are

estimated to store nearly 20 billion

tons of organic carbon

but these vast underwater prairies can

have profound short-term benefits as

well for both people and the natural

world

seagrasses are ecosystem engineers

because they alter the landscape around

them their rising leaves slow down water

currents

causing them to drop their sediment

building up the seafloor

and forming shallow offshore banks of

sea grass and sediment

these shield coastal settlements from

storm surges and high waves and protect

valuable ecosystems like mangroves and

salt marshes

their underground network of routes

stabilizes these banks

reducing coastal erosion as well

seagrasses have thrived for millions of

years but in the 21st century these

delicate underwater grasslands are under

threat

fishing with dredges and beam trollers

uproots and destroys the meadows but

it's pollution from the land and runoff

from coastal development which poses the

greatest danger nutrients like nitrogen

and phosphorus run off into the seas

they're toxic to the grasses and they

fuel the growth of algae blocking out

the sunlight and halting the

photosynthesis needed for growth

as the grasses decay the algae bloom and

the ecosystem collapses a cascading

shift from seagrass to algal dominance

and overfishing of top predators like

sharks reduces the control of grazing

species which strip the fragile prairies

bear it's thought that today there are

between 300 to 600 000 kilometers

squared of seagrass meadows across the

world

but each hour an area the size of two

football fields is lost the damage must

be halted before it's too late seagrass

prairies can be regrown using cuttings

from donor meadows planted in sunken

artificial sandbags and researchers and

marine biologists are experimenting with

new planting methods and developing seed

banks for some species but restoration

is expensive and labor intensive and to

so far produce poor outcomes it is clear

that with the current understanding and

technology our ability to regenerate

seagrass meadows will always fall short

of the sea grasses natural ability to

spread and therefore our foremost

priority must be the protection of

existing seagrass prairies these rich

fragile ecosystems could be one of our

greatest tools to combat global climate

change

and they must be protected

at all costs

[Music]

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[Music]

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