Avicennia alba (Blume, 1826)Api-Api Putih

General Introduction

Table of Contents

Avicennia alba is a common species of mangrove plant that belongs to the family Acanthaceae. It has a common name Api-api putih, in the Malay language[1] Ng P.K.L and Sivasothi N. (1999). A Guide to the Mangroves of Singapore I: The Ecosystem and Plant Diversity. Singapore Science Centre.

Distribution

Global distribution
Api-api putih has a wide distribution from Western India to Indochina, the Malay Archipelago, the Philippines, New Guinea and Northern Australia (Figure 1)[3] Tomlinson P. B. (eds). (1994). The botany of mangroves. Cambridge tropical ecology series. Cambridge university press. pp. 419. Tomlinson, B. P., 1986. The Botany of Mangroves. Cambridge University Press, Cambridge

Distribution within Singapore
This particular species is very common in Singapore and can be found in almost all the mangrove patches in Singapore, as seen in Figure 2. The map below shows the distribution of mangrove forest in Singapore and the places bold in red are mangroves where Api-api putih can be found, with information gathered from various online sources[4] Yee A.T.K., Ang W.F., Teo S., Liew S.C., Tan H.T.W. (2010). The present extent of mangrove forest in Singapore. Nature in Singapore 3:139–145. 

If you want to visit a mangrove in Singapore, there are four that are accessible to the public!
1) Sungei Buloh Wetland Reserve;
2) Chek Jawa;
3) Pasir Ris Mangrove and;
4) Berlayer Creek
Visit National Parks Board website for directions!
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How to identify Api-api putih!

Api-api putih is a tree that can grow up to around 10 to 25 metres in height. With the description of the plant below, you can learn how to identify Api-api putih as well[3] Tomlinson P. B. (eds). (1994). The botany of mangroves. Cambridge tropical ecology series. Cambridge university press. pp. 419. Tomlinson, B. P., 1986. The Botany of Mangroves. Cambridge University Press, Cambridge

Leaves -Characteristically lanceolated (long and pointed at the apex) -Around 8-12cm long -Dark green on upperside, pale-coloured, whitish on the underside -Leaves are simple (undivided leaf blade) and opposite (a pair of leaves attached at a node) Pale, whitish underside of leave (leftmost), Glossy, dark green upperside of leave (middle), Long elliptic opposite leaves at each node. A node is circled red in the picture (rightmost) (Source: © Jessica Tay)

Flowers - Orange-yellow colour with around 10-30 flowers on each unit. - Each flower is only about 0.5cm in diameter with four equal lobed petals that are smooth on the inside. - Flowers of Api-api putih is distinguished from other Avicennia species by its long spicate distal flower units that are about 1.5 to 3cm long. - Stamens are short, only about 2mm long and does not protrude or thrust outwards - Ovary is about 2mm long and without a style. Small protruding spicate (form of spike) orange-yellow flower unit (left) and up-close of flower that has four equal lobed petals (right). (Source: © www.NatureLoveYou.sg).

Fruits Conical shaped fruits with its distinctive pointed tip (Source: © www.NatureLoveYou.sg). - Distinctive conical shape that extends to a pronounced pointed tip. - It is especially obvious during the early stages of fruit development. - About 1-4cm long - Smooth velvety outer skin. - Each fruit contains a single seed.

Pencil roots growing upwards to a height of around 20 to 30cm. (Source: Cheong J. M. D) Roots- Pencil-like aerial roots known as pneumatophores. - About 20–30 cm tall with a tapered bluntly pointed end. - Lenticels, for gaseous exchange, are found on the roots.

Bark Greyish-brown bark that is smooth and non-fissured.(Source: © www.NatureLoveYou.sg) - Somewhat dark grey/brown. - Smooth or slightly roughened but it is not fissured. - A distinct character of Api-api putih tree is the growth of sooty mould on older stem parts.

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Biology

Habitat type

Api-api putih is known to be a pioneering species, meaning they are able to quickly colonise areas which are previously damaged. A typical zonation pattern in the Indo-Pacific region is one with Avicennia species to be nearest to the coastline (seaward side) on newly-formed mud banks[5] Smith T.J.III. (1992). Forest structure. In: Robertson AI, Alongi DM (eds) Tropical mangrove ecosystems. American Geophysical Union. American Geophysical Union, Washington, pp 101–136.

Reproduction

Api-api putih, like all other Avicennia species are insect-pollinated. They are commonly pollinated by flies and bees. These pollinators serve an important purpose for successful sexual reproduction for greater genetic variability because Api-api putih is capable of self-pollination[8] Matthijs S., Tack J., van Speybroeck D. and Koedam N. (1999). Mangrove species zonation and soil redox state, sulphide concentration and salinity in Gazi Bay (Kenya), a preliminary study. Mangroves and salt marshes 3: 243–249.

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Ecology

Damage/Pest	Mechanism/Organism
Avicennia seed moth Autoba alabastrata[12] Murphy D.H. (1990). The natural history of herbivory on mangrove trees in and near Singapore. Raffles Bulletin of Zoology 38:119–203. ]]>	This is the most serious pest related mortality on mature fruits of Api-api putih. Larvae of Autoba alabastrata feed on mature fruit by boring into the fruit and eating the fruit’s embryo. Infected fruit will be attached to a nearby stem by a web produced by larvae. This prevents fruit from falling into the water when it detaches from the parent tree because larvae would drown if water floods into the fruit via large bore holes. Large bore holes on fruit (Source: Guide to the mangroves of Singapore) Each larva is capable of destroying up to eight fruits before it pupates in the last fruit. An infected tree is easily identified by its shrivelled fruits. Larva feeding in a fruit (Source: Guide to the mangroves of Singapore)
Foliage damage by herbivores[12] Murphy D.H. (1990). The natural history of herbivory on mangrove trees in and near Singapore. Raffles Bulletin of Zoology 38:119–203. ]]>	All Avicennia species are often damaged by leaf mining moth Phyllocnistis which will destroy young leaves by mining the upper surface of young expanding leaves. They then pupate in a fold at the edge of the leave. Example of leaf-mining in the Lonicera periclymenum leaf (Source: Creative Commons: Share Alike)
Structural damage[12] Murphy D.H. (1990). The natural history of herbivory on mangrove trees in and near Singapore. Raffles Bulletin of Zoology 38:119–203. ]]>	Twigs and young stems of young Avicennia species saplings are susceptible to twig boring larvae of Cossidae moth (Zeuzera conferta). The larva bore through the pith canal and causes nodular enlargement. Example of stem-boring damage by larvae of Leopard Moth, Zeuzera pyrina. (Source: © Mike Hardman, Cyprus) Back to Top

Adaptations

Api-api putih are usually found near the coast and its habitat is frequently inundated. Therefore, it has special adaptations to survive in areas that have high salinity, waterlogged muddy soil and high wave actions[13] Joshi H. and Ghose M. (2003). Forest structure and species distribution along soil salinity and pH gradient in mangrove swamps of the Sundarbans. Tropical ecology 44:197–206. 

Roots

Vertical pencil roots (pneumatophores) help to transport oxygen to underground root system

.
During a tidal inundation, waterlogged soils are often poorly oxygenated. Therefore, Api-api putih has specialised roots, also known as breathing roots, to help in gaseous exchange. These roots are vertical pencil roots, known as pneumatophores, which grows vertically upwards from the submerged lateral underground root system (Figure 5). Pencil roots are covered with lenticels that enables gaseous exchange for oxygen directly from the surface (Figure 4). Hence, pencil roots provide the plant with additional oxygen which cannot be taken from the soil. However, gaseous exchange can only occur when pencil roots are not submerged because at high tides, surface tension of water blocks lenticels and prevent gaseous exchange[14] Mangrove roots (2014). Retrieved from: http://www.mangrove.at/mangrove_roots.html. (Accessed on 18th October 2014)

Important for salt exclusion
Mangroves evolved specialised survival strategies to thrive under high salinity environments. For Avicennia species, they are salt secretor, which means that they exclude excess salt from their roots and leaves. The roots exclude 85-95% of the salt that are carried towards the roots via transpiration. This is because roots develop barriers against apoplastic movement that increase resistance to water flow and exclude salt from entering the roots[15] Krishnamurthy P., Jyothi-Prakash P.A., Qin L., He J., Lin Q., Loh C., and Kumar P.P. (2014). Role of root hydrophobic barriers in salt exclusion of a mangrove plant Avicennia officinalis. Plant, Cell and Environment.

Salt secretion from leaves
Api-api putih, like other Avicennia species, secretes excess salt that is not excluded at the roots from its leaves[16] Parida A.K. and Jha B. (2010). Salt tolerance mechanisms in mangroves: a review. Trees 24:199–217.

Conservation status

Despite the threats listed above, Api-api putih has a conservation status of being the least concern, according to the IUCN Red list[19] International Union for Conservation of Nature (2014). Avicennia alba. Retrieved from: http://www.iucnredlist.org/details/178830/0 (Accessed on 26th October 2014).

Taxonomy

Original description
The original description of Api-api putih is in Latin by Blume C.L.(1826) Bijdragen tot de flora van Nederlansch Indië Vol. 14: 821.

From the description above, it roughly translates to:


'Leaves are oblong-lanceolate and acute, smooth snowy underside. It increases towards the shore.
Flowers blossoms all year-round and the name is Api Api'

Type Information
The type specimen of Api-api putih can be found in Botanic Garden Meise Herbarium in Belgium (Barcode number: BR0000009088016).
One can refer to this type specimen (Figure 7) to confirm the identification of Api-api putih plant.

Phylogenetic analysis
In the genus Avicennia L., there are eight species. From a study by Schwarzbach and McDade (2002)[20] Schwarzbach A.E. and McDade L.A. (2002). Phylogenetic Relationships of the Mangrove Family Avicenniaceae based on chloroplast and nuclear ribosomal DNA sequences. Systematic Botany 27:84–98.

Genetic studies to help improve efficiency of breeding programmes
In another study by Ghose et al. (2014)[21] Ghosh P., Das S. S. and Das S. (2014). Phylogenetic relationship among three species of the mangrove genus //Avincennia// found in Indian Sundarban, as revealed by RAPD analysis. Asian Journal of Plant Science and Research 4:25-30.

1. A. alba and A. officinalis are more closely related to each other and share a common mode on the phylogenetic tree at 73.4% of similarity (Figure 9).
2. A. marina showed most genetic variability.

Therefore, this suggests that A. marina should be used over other species in breeding programmes to conserve genetic variability which are needed for species to have higher fitness and have the ability to adapt, evolve and prevent extinction. Genetic studies can help in improving the understanding of phylogenetic relationships, which may further assist breeding programmes for sustainable management and conservation of genetic resources.
Hybridization in Avicennia species
There are no evidence of hybridization among different species of Avicennia, even if more than one species are found in close proximity to one another, thus demonstrating their reproductive isolation[22] Duke N.C., Benzie J.A.H., Goodall J. A. and Ballment E.R. (1998). Genetic structure and evolution of species in the mangrove genus Avicennia(Avicenniaceae) in the Indo-West pacific. Evolution 52: 1612–1626.

Importance of Mangroves

Other than Api-api putih, there are many other species of mangrove plant. In fact, that are roughly 70 species of mangroves around the world[22] Duke N.C., Benzie J.A.H., Goodall J. A. and Ballment E.R. (1998). Genetic structure and evolution of species in the mangrove genus Avicennia(Avicenniaceae) in the Indo-West pacific. Evolution 52: 1612–1626.

1) They are ‘land builders’[24] McKee K. L. (1996). Mangrove ecosystem: Definitions, distribution, zonation, forest structure, trophic structure, and ecological significance. In: Feller I. C. and Sitnik M. (eds). Mangrove ecology: a manual for a field course. A field manual focused on the. biocomplexity on mangrove ecosystems. 1–6.

• Mangroves roots help to trap sediments and reclaim land naturally. Trapping of sediments also contribute to soil formation which also facilitates in stabilizing the coastline[25] Ewel K.C., Twilley R.R. and Ong J.E. (1998). Different kinds of mangrove forest provide different goods and services. Global ecology and biogeography letters 7:83–94.

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2) Natural water purification system

• Mangroves act as a filter for upland run-off via trapping of sediments and litters between their network of roots[26] Sulochanan B. (2013). Mangrove ecosystem and its impact on fisheries. Central Marine Fisheries Research Institute. 57–62.

  ]]>(Figure 10). This helps to prevent sediments and litters from being flushed into the sea and cause marine pollution.

• Filtration of water improves water quality and maintain water clarity which are important for organisms like clams and oysters to thrive in the mangrove and intertidal area[26] Sulochanan B. (2013). Mangrove ecosystem and its impact on fisheries. Central Marine Fisheries Research Institute. 57–62.

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3) Nursery for juvenile organisms

• Mangroves serve as important nurseries for juvenile of many marine organisms, such as reef fishes, crabs and oysters[27] Robertson A. I. and Blaber S. J. M. (1992) Planktons, epibenthos and fish communities. In: Robertson A. I., Alongi D. M. (Eds.), Tropical Mangrove Ecosystems. Coastal and Estuarine Studies No. 41, American geophysical union, Washington, DC (1992), pp. 173 – 224.

  ]]>[28] Macnae W. (1974). Mangrove forest and fisheries. FAO. Rome. IOFC/DEV/74/34, 35 pp.
  ]]>, by providing food and shelter against predators before juveniles grow big enough to swim out to patch reefs or the ocean[29] Roach J. (2004). Mangroves are nurseries for reef fish, study finds. National Geographic news.
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• They are also important feeding grounds for transient birds, reptiles and fishes[25] Ewel K.C., Twilley R.R. and Ong J.E. (1998). Different kinds of mangrove forest provide different goods and services. Global ecology and biogeography letters 7:83–94.

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4) Contribution to marine productivity

• Mangroves produce large amounts of detritus that serves as the basis of the food web and hence possibly contributes to productivity in offshore waters[26] Sulochanan B. (2013). Mangrove ecosystem and its impact on fisheries. Central Marine Fisheries Research Institute. 57–62.

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5) Carbon sequestration 

• Mangrove forests are is one of the largest storage of carbon[30] Donato D. C., Kauffman B.J., Murdiyarso D., Kurnianto S., Stidham M., and Kanninen M. (2011). Mangroves among the most carbon-rich forests in the tropics. Nature Geoscience, 4: 293–297.

  ]]>. Thus they play an important role in the global carbon cycle. Therefore, increasing the extent of mangrove forests can be used as effective means against climate change.

6) Coastline protection

• Mangroves are found along coastlines and they serves as a barrier of protection against shoreline erosion by strong waves and currents and help to protect coastal communities against storms[25] Ewel K.C., Twilley R.R. and Ong J.E. (1998). Different kinds of mangrove forest provide different goods and services. Global ecology and biogeography letters 7:83–94.

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• From Figure 11, it shows that wave height can be reduced as it travels through the mangrove forest. For example, wave height is reduced by 35% as it travels through 80 metres of mangrove forest[31] McIvor A., Möller I., Spencer T., and Spalding M., (2012). Reduction of wind and swell waves by mangroves. Natural Coastal Protection Series: Report 1: The Nature Conservancy and Wetlands International.

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7) Contribute nutrient to environment

• Avicennia species have leaves that are known to be thinner and contain fewer types of tannin (less chemical defense against herbivory). Therefore they decomposed at a faster rate than other mangrove species[32] Sivakumar, A. and Kathiresan, K. (1990). Phylloplane fungi from mangroves. Indian Journal of Microbiology, 30(2) : 229 – 231.

  ]]>, contributing more nutrient to the environment.

Importance of mangrove in Singapore
Important feeding ground for migratory birds[33] Sivasothi M. (2003). Mandai mangrove and mudflat. Retrieved from: http://mangrove.nus.edu.sg/mandai/significance.html. (Accessed on 20th October 2014).

• An important mangrove habitat in Singapore is Sungei Buloh Nature Reserve which serves as a major bird roosting site. Every year, Sungei Buloh function as an important stop-over site for around 12 – 15 thousand million migratory birds flying from the northern Eurasian continent to Africa and the Southern parts of Asia to escape the winter months. The flyway (migratory route) along Singapore is known as the East Asian Australasian Flyway.
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Threats to Mangroves

Despite the importance of mangroves, this ecosystem still faces threats which have the potential of pushing some species to extinction. 

1) Conversion of mangrove forest for shrimp farming

• Due to the high biomass productivity in the mangrove forest, trees are often cleared away for conversion into shrimp ponds (Figure 12). In the past, Sungei Buloh also had shrimp ponds where prawns spawn in the mangroves that were rich in organic nutrients[34] Lee Kong Chian Natural History Museum (2014) Prawn farming. Retrieved from: http://lkcnhm.nus.edu.sg/dna/activities/details/32 (Accessed on 3rd November 2014). 

  ]]>. However, shrimp aquaculture has many harmful impacts on the mangrove forest, including direct loss of mangrove forest to construct ponds, increase in sedimentation and turbidity from ponds, reduction in water quality and influx of excess nutrients which could lead to harmful algal bloom[23] Alongi D.M. (2002). Present state and future of the world’s mangrove forests. Environmental Conservation 29:331–349.
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2) Overexploitation of ecological goods and services

• Mangrove forest has long been exploited by coastal communities for its ecological goods such as timber, tannin and food, and services such as water filtration and flood abatement. The increase in human population has led to encroachment of community into coastal area. This may results in increased volume of waste being dumped into mangroves and adjacent coastal habitats. While mangrove forest can adsorb some of the excess nutrients, toxic waste are harmful to their growth[35] Yim M.W. and Tam N.F. Y. (1999). Effects of wastewater-borne heavy metals on mangrove plants and soil microbial activities. Marine Pollution Bulletin 39:179–186.

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3) Mangrove deforestation

• Mangrove forests are also deforested for timber as well as to make space for growing agriculture crops, building of housing or for aquaculture (Figure 13). Sediments usually get accumulated at flooded estuaries and mangrove forests.When mangroves are removed, the loss of a sediment sink may lead to increase sediments in the sea[36] van Maren D.S., Liew S.C. and Hasan G.M.J. (2014). The role of terrestrial sediments on turbidity near Singapore’s coral reefs. Continental Shelf Research 76:75–88.

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4) Coastal squeeze

• Mangrove forests are vulnerable to sea level rise and they progress landwards at a rate that is determined by the rate of 1) sea level rise, 2) sediment accretion and 3) rate of erosion[23] Alongi D.M. (2002). Present state and future of the world’s mangrove forests. Environmental Conservation 29:331–349.

  ]]>. However, as countries build seawalls against sea level rise, they prevent migration of mangroves toward adjacent upland[37] Torio D.D. and Chmura G.L. (2013). Assessing coastal squeeze of tidal wetland. Journal of Coastal Research 29:1049–1061.
  ]]> (Figure 14). Coastal squeeze will slowly decrease the area of mangrove forest and eventually causing them to drown if sediment erosion by sea level rise is greater than sediment accretion[37] Torio D.D. and Chmura G.L. (2013). Assessing coastal squeeze of tidal wetland. Journal of Coastal Research 29:1049–1061.
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Glossary

Here are definitions of some of the terms used in the page to help you better understand the content[39] http://dictionary.reference.com/. Accessed on 23rd November 2014.

Contact me

Do feel free to contact me at jesstay92@gmail.com if you wish to use any of the photos which are taken by me (source: © Jessica Tay) or you have any questions regarding the page. Also, please check out the other species pages that were done by other students who have taken this module! 

References

This page was authored by Tay Ying Ling Jessica
Last curated on 2014