MANGROVES

What are mangroves?

Various types of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics

Thrive in intertidal between seagrass beds and the coast

Extremely productive and provide numerous goods and services both to the marine environment and people

Fisheries (nurseries), timber and land products, costal protection and tourism

How are mangroves interconnected with coral reefs and seagrass beds?

How do mangroves help the Goliath Grouper?

Crucial in juvenile survival because mangroves serve as microhabitats that prevent predation

What are epiphytes?

'Air plants' - plants that grow on top of other plants (typically trees) co-existing in the most harmonious, harmless way

E.g., creepers, orchids, fernsW

Why are mangroves considered blue carbon ecosystems?

Blue carbon is any carbon stored by the ocean

Highly effective at capturing and storing carbon dioxide (CO2) from the atmosphere and storing it in their biomass and sediments (burial)

CO2 decomposes under anaerobic conditions

Largely due to the deep, organic rich soils

What is carbon storage vs sequestration?

Carbon storage: total amount of carbon contained in a forest or a part of the forest (soil or trees) “stock” or “pool”

Carbon sequestration: the process of removing carbon from the atmosphere and storing it in another form that cannot be immediately released (wood) “rate”

How do mangroves protect the coastline?

Natural barrier against storms

Absorbing and weakening wave energy as well as preventing damage caused by debris movement due to storms or tsunamis

Entangled roots stabilize coastal areas through sediment capture and bio-filtration of nutrients and pollutants

Aerial roots filter sediments and reduce pollutants from sewage and aquaculture in estuaries and coastal waters H

What are the benefits to local communities?

Provide food, medicines, fuel wood, charcoal, and construction materials

What was the evolution of mangroves?

Evolved independently 16 times

Polyphyletic group - set of organisms that have been grouped together but do not share an immediate common ancestor (e.g., sharks and dolphins)

Similar traits due to convergent evolution

~ 55 species in 20 genera in 16 families

Mangal = mangrove community

Mangrove tree root system

What are aerial roots?

“Breathing roots”

Allow mangroves to exchange gases, including oxygen, with the air

Oxygen content of water is far below that of air

Bacteria in soil can deplete soil oxygen content

Oxygen diffuses through water 10,000 times slower than air

Types of mangrove roots

How are sponges beneficial to mangroves?

Nitrogen: sponges provide nitrogen to mangroves, essential for growth

Carbon: mangroves provide CO2 to sponges through photosynthesis

Protection: sponges protect mangrove roots from isopods that burrow into roots

Growth: mangroves grow 2-4 times faster when sponges grow on their roots

What is gas exchange?

Occurs through specialized pore in plants

• Stomata: pores in the epidermis of leaves

• Lenticels: pores found in the trunk or roots of the tree

Adaptations for salinity

Mangroves have aerial and salt-filtering roots and salt-excreting leaves which enable them to occupy the saline wetlands

Exclusion of salt (prevention)

• From root and leaves

  • Transport systems with low affinity to Na+ and Cl- uptake

Secretion of salt (expelling excess)

• In bark of stems or roots

• In leaves (salt glands)

Conserving water

• Succulent leaves with waxy cuticle on top

• High water use efficiency

• Smaller leaves

• Leaves at an angle to the sun (adaptation to light)

How do mangroves reproduce?

By flowering with pollination

Wind - Rhizophora

• Produce lots of light, powdery pollen

• No nectar

Animals

• Bats

• Bees

• Birds

• Hawk moths

What are mangrove propagules?

Seed-like structures that allow mangrove trees to reproduce (“seedlings”)

All mangroves disperse offspring by water

Produce large propagules

Vivipary: growing embryo remains on parent tree before departing as a seedling

Parent supplies water, nutrients, carbohydrates

Controlled by hormones

Threats to mangroves

Over ½ of the world’s mangrove forests have been destroyed during the last 50 years (80 million acres)

Coastal developments, shrimp aquaculture, agriculture expansion, and unsustainable tourism

Natural habitat migration vs coastal squeeze

Natural habitat migration: mangrove forests migrate landwards

• Sea level rise causes erosion of mangrove at seaward edge

Coastal squeeze

• Area is being ‘squeezed’ as mangrove forest cannot migrate landward due to a sea wall

What are the impacts of eutrophication on mangroves?

What are mangrove cultivating pots?

Rough texture

Made with concrete that disintegrates within a few years

Pot hold soil and reef safe slow fertilizers

Anchor to hold in position

Helps keep waves and floating debris from knocking over

Wrack protector (pop off as tree grows)

What are problems with mangrove restoration?

Mostly happening with red mangrove propagules

• Single species creates monoculture that are not resilient to storms and surges

Planting is often done where mangroves do not naturally grow

• Other ecosystems (seagrass beds) are trampled on by volunteers

Seedlings are planted in areas that are submerged for too many hours or where wave impact is too strong

Restored mangrove belts do not often extend for more than 100 meters

What is the mangrove zonation?

Caused from varying salinity tolerances

Red mangroves with prop roots are closest to the water, followed by black mangroves with pneumatophores, and white mangroves closest to land