Nature-based solutions: Seagrass
Image: Glen Carbines, NIWA
Native Ecosystems
- Native ecosystems: our climate superheroes
- Our natural heritage
- The villains: predators & pests
- Our native forests
- Our soils: carbon super-sponges
- Our rivers & lakes
- Our wetlands
- Our dunes & coastal wetlands
- Our estuaries & hapua
- Our oceans: the ultimate climate superheroes
- Our blue carbon
- Seaweed
- Seagrass
- Ecosystem services: free stuff from Nature
- Losing our biodiversity
- Plants & animals on the move!
Other sections
Blue carbon: seagrass
Summary
- Seagrasses are found in shallow salty and brackish waters, from the tropics to the Arctic Circle.
- There is just one species in Aotearoa, rimurēhia (Zostera muelleri). Significant declines occured mostly between the 1930s and 1970s in Whangarei, Waitemata, Manukau, Whangamata and Tauranga Harbours, and the Avon-Heathcote estuary in Christchurch.
- Like kelp, seagrass meadows are some of the most productive ecosystems on Earth. They provide shelter and food for diverse communities of animals, from tiny invertebrates to large fish, crabs, marine mammals, and birds. The small crustaceans and worms that live in them are important sources of food for wading birds (such as the South Island oyster catcher, pied stilt, royal spoonbill, bar-tailed godwit) and fish: snapper and leatherjacket juveniles, mullet, trevally, garfish, parore, spotties, pipefish and triplefins.
- Dense meadows of seagrass can stabilise the sea bed and reduce erosion. Their leaves trap fine sediments and reduce particle loads in the water by slowing water movement and encouraging particle deposition, which improves water clarity.
- They also drawdown large quantities of carbon dioxide, absorb nutrients from the water and seabed, and fix nitrogen in their soils, and then release oxygen from their leaves and roots, which is beneficial for other biota and stimulates nutrient cycling.
- None of this carbon is accounted for under the Emissions Trading Scheme.
- Risks to seagrasses: polluted water from our rivers. Increasing marine heatwaves means that some species that have adapted to live in cooler waters, are under threat. Ships that release ballast water into harbours also release exotic species. Coastal squeeze limits their ability to move inshore as sea levels rise. The loss of seagrasses could lead to a negative trophic cascade.
Native Ecosystems
- Native ecosystems: our climate superheroes
- Our natural heritage
- The villains: predators & pests
- Our native forests
- Our soils: carbon super-sponges
- Our rivers & lakes
- Our wetlands
- Our dunes & coastal wetlands
- Our estuaries & hapua
- Our oceans: the ultimate climate superheroes
- Our blue carbon
- Seaweed
- Seagrass
- Ecosystem services: free stuff from Nature
- Losing our biodiversity
- Plants & animals on the move!
Other sections
Blue carbon: seagrass
Summary
- Seagrasses are found in shallow salty and brackish waters, from the tropics to the Arctic Circle.
- There is just one species in Aotearoa, rimurēhia (Zostera muelleri). Significant declines occurred mostly between the 1930s and 1970s in Whangarei, Waitemata, Manukau, Whangamata and Tauranga Harbours, and the Avon-Heathcote estuary in Christchurch.
- Like kelp, seagrass meadows are some of the most productive ecosystems on Earth. They provide shelter and food for diverse communities of animals, from tiny invertebrates to large fish, crabs, marine mammals, and birds. The small crustaceans and worms that live in them are important sources of food for wading birds (such as the South Island oyster catcher, pied stilt, royal spoonbill, bar-tailed godwit) and fish: snapper and leatherjacket juveniles, mullet, trevally, garfish, parore, spotties, pipefish and triplefins.
- Dense meadows of seagrass can stabilise the sea bed and reduce erosion. Their leaves trap fine sediments and reduce particle loads in the water by slowing water movement and encouraging particle deposition, which improves water clarity.
- They also drawdown large quantities of carbon dioxide, absorb nutrients from the water and seabed, and fix nitrogen in their soils, and then release oxygen from their leaves and roots, which is beneficial for other biota and stimulates nutrient cycling.
- None of this carbon is accounted for under the Emissions Trading Scheme.
- Risks to seagrasses: polluted water from our rivers. Increasing marine heatwaves means that some species that have adapted to live in cooler waters, are under threat. Ships that release ballast water into harbours also release exotic species. Coastal squeeze limits their ability to move inshore as sea levels rise.The loss of seagrasses could lead to a negative trophic cascade.
More information
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Drawdown
To draw excess greenhouse gasses, primarily carbon dioxide from the atmosphere and store it back underground. See the carbon cycle.
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Trophic systems
Level 1: Producers: plants and algae make their own food.
Level 2: Primary consumers: herbivores such as cows eat plants.
Level 3: Secondary consumers: carnivores that eat herbivores.
Level 4: Tertiary consumers: carnivores that eat other carnivores, such as big fish eating smaller carnivorous fish.
A trophic cascade is a side-effect when a trophic level (species such as top predators) of an ecosystem is reduced or removed. This results in a negative ‘domino’ effect because their interactions with other species would normally keep the entire ecosystems balanced. Removing or reducing the number of whales, for example, interrupts the vital exchange of nutrients that support the growth of plankton, and with them, the other species (including humans) which rely on them for their existence.
Another simple example is removing top predators. Removing wolves, for example, would cause their prey, such as deer, to multiply in number. Too many deer means the ecosystem that once supported them will be depleted with so many deer, they over-graze their habitat, which in turn will have a negative impact on other species and lead to problems such as soil erosion and loss of soil carbon.
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- Sustainable Seas Challenge (part of the National Science Challenge New Zealand; includes up-to-date research links and papers)
- Seagrass Restoration Network (Australia and New Zealand)
- Landcare Research
- Cawthron Institute
- Blue Carbon NZ
- AgResearch
- NIWA
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- 2024: Capistrant-Fossa & Dunton; Rapid sea level rise causes loss of seagrass meadows, Nature Communications Earth & Environment 5 | 87
- 2024: Wernberg et al; Impacts of Climate Change on Marine Foundation Species; Annual Review of Marine Science, 16: 247-248
- 2022: Pullen et al, Seasonal dynamics of faunal diversity and population ecology in an estuarine seagrass bed. Estuaries and Coasts 8: pp 2578-2591 (study undertaken in Duvauchelle Bay)
- 2020: Thomsen et al, Seagrass beds provide habitat for crabs, shrimps and fish in two estuaries on the South Island of New Zealand; Report to Environment Canterbury
- Project Seagrass
- United Nations: Healthy seagrasses, healthy planet