Adaptations to
The tidal Zone

Australia’s mangroves show remarkable adaptations dealing with frequent saltwater inundation and varying climatic zones from arid to very wet. Mangroves share specialised attributes for growing with excess salt and saturated air-less soils. They also have special growth strategies to facilitate establishment and regeneration. One special attribute promoting sustainability and dispersal of mangroves is their unusual production of live young - vivipary. Such attributes have kept mangroves from extinction for more than 50 million years, and enabled them to occupy tidal areas around the world.

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Flowers & Propagation

Acanthus Butterfly

Flowers Spreading Love Around

Flowers facilitate pollination and fertilization. They do this by both attracting specific pollinators and providing a strategy for effective transfer of pollen from male to receptive female reproductive parts. Flowers are spectacularly variable in structure with perfect combined-sex flowers (like Rhizophora spp., Sonneratia spp., Avicennia spp.), separate-sex flowers (like Heritiera littoralis), separate-sex trees (like Excoecaria agallocha); colours as white (like Sonneratia alba, Lumnitzera racemosa), red (like Sonneratia caseolaris, Lumnitzera littorea), pink (like Lumnitzera X rosea), purple (like Acanthus ebracteatus subsp. ebarbatus), lilac (like Acanthus ilicifolius), pale yellow (like Avicennia integra), orange-yellow (like Avicennia marina); and size as large (like Dolichandrone spathacea), medium size (like Bruguiera gymnorhiza) and small (like Avicennia marina, Osbornia octodonta).

Flowers are used by a range of fauna including: birds with honey eaters (triggering an explosive pollen release in Bruguiera spp.), and parrots (cropping Lumnitzera littorea); insects with large bees (Acanthus spp.), hawk moths (Sonneratia alba), honey bees (Avicennia marina), flys (Nypa fruticans); and nectar feeding bats (Sonneratia alba).

Acanthus ebracteatus subsp. ebarbatus, South Alligator River, Northern Territory.

  • Opening flower buds of Sonneratia caseolaris.
  • Multiple flowered inflorescences of Bruguiera parviflora.
  • Spreading white flower of Lumnitzera racemosa.

Propagules for Drift and Dispersal

An important attribute of mangroves is the high percentage of viviparous propagules. Vivipary is the bearing of live young where seeds germinate on the parent tree and new seedlings remain attached as they grow. Not all mangroves have this character, and many have lesser degrees of vivipary while a small group have no apparent specialization.

In most cases, all propagules are buoyant for at least a short dispersal phase. The undeniable dispersal specialists are the Rhizophoras. These have highly-developed viviparous propagules that are believed to endure for several months at sea in a semi-dormant state. In general however, the propagules of different species possess differing dispersal abilities, causing each species to have distributional ranges that differ according to their capacity to travel specific distances at sea.

Fruits, including viviparous propagules, have a range of characteristics including: seeds (like Xylocarpus spp., Osbornia octodonta, Sonneratia spp.), cryptovivipary (like Avicennia spp.), and vivipary (like Rhizophora spp., Bruguiera spp., Ceriops spp.); structural features as drupe (like Sonneratia spp.), capsules (like Excoecaria agallocha), hypocotyls (like Rhizophora spp., Bruguiera spp., Ceriops spp.), cotyledons (like Avicennia spp., Lumnitzera spp.), kapok (suggested dry climate benefit, Camptostemon schultzii), fleshy (like Sonneratia caseolaris), woody (like Xylocarpus spp.), persistent style (like Sonneratia spp., Avicennia spp.), keeled pod (like Heritiera littoralis), and elongate pointed radicles (like Rhizophora mucronata, Rhizophora stylosa).

Mature viviparous hypocotyls of Ceriops australis.

  • Mature fruit capsules of Scyphiphora hydrophylacea.
  • Mature crypto-viviparous fruit of Avicennia marina.

Community Volunteers

A key feature of MangroveWatch is its close partnership between community volunteers and scientists from the James Cook University’s Mangrove Hub. Together they are systematically recording basic data as video and still imagery for assessments of estuarine habitat health.

Armed with expert support, training and advice, MangroveWatch volunteers in key regions are actively contributing to the monitoring of local estuaries and shorelines. An important goal in this phase of the program is to develop a network of like minded groups with the aim of producing public documents that describe important issues affecting local estuaries and mangroves, and their overall health.

Getting Involved

If you would like to find out more about us or if you like to initiate your own MangroveWatch group within your area, please contact someone at the Mangrove Hub. We will be happy to help.

  • Mangrove Hub Facilitator
  • Dr Norm Duke
  • MangroveWatch Ltd
    ABN: 44 153 297 771
  • PO Box 1250,
  • Elanora Q 4221
  • Mangrove Hub Email

Mangrove Watch Brochure

You can download our fact and information sheet (see link below) to get more information about the MangroveWatch programs.

Mangrove Watch Brochure