Mangroves in the Northern Territory - Department of Land Resource ...

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Crustaceans Crustaceans, a group of animals which includes prawns and crabs, can be differentiated from other animals by having appendages (legs) which split into two. The most obvious example being the claw of crabs (see Plate 52) (Knox et al. 1994). Crabs play an important role in mangrove nutrient recycling and soil aeration (Moritz- Zimmerman et al 2002). Plate 53: Fiddler crab (Uca sp.) Fiddler crabs can be easily identified, as male fiddler crabs have one massively disproportionate, brightly coloured claw which is used when courting female crabs, in territorial defence and as a warning system (Mastaller 1997). Insects Many different types of insects can be found in mangrove environments. However their significance to tropical mangrove systems, specifically in regards to pollination and herbivory is poorly understood. The links between mangroves and insects is a current focus of study in Darwin Harbour (Moritz- Zimmerman et al 2002). Plate 54: Katydid The most infamous of mangrove insects are those which parasitise humans. Biting insects found in the mangroves include mosquitos and sand flies. Visitors to mangroves should be careful by wearing protective clothing and insect repellent. Molluscs Plate 55: Telescopium telescopium (Long bum) Molluscs are animals which have soft bodies which are supported and protected by unusually hard shells. Examples of molluscs include snails, oysters and mussels. Many different types of molluscs can be found in the mangroves. Indigenous people harvest various mollusc types for food. Bush tucker can include long bums, periwinkles, scallops, mud whelks and mussels (Puruntatameri et al 2001). Northern Territory Mangrove Education Kit 22
What’s that smell? Mangrove Soils Mangrove communities are often associated with thick glutenous mud. This mud has been formed by the continuous deposition of fine soil particles which may have been transported by watercourses such as creeks or rivers for many kilometres (Mastaller 1997). Plate 56: Mangrove mud The muddy substrate commonly associated with mangroves is actually made up of many tiny grains of soil, which in combination with tidal water sources form semi fluid mud. The lack of spaces between soil particles mean that no oxygen can infiltrate past the uppermost soil layers. This lack of oxygen means that bacteria can live happily in these lower levels. The bacteria produce a gas called hydrogen sulphide. When this gas reaches the surface it is easily recognisable by its characteristic rotten egg smell (Mastaller 1997)! Acid sulphate soils Acid sulphate soils are a major concern of both environmental scientists and developers of mangrove areas. Acid sulphate soils are formed when naturally occurring regions of waterlogged iron sulphides are exposed to oxygen in the air. When these sulphides come into contact with air, for example through clearing or excavation, they oxidise to form sulphuric acid (Sammut & Lines-Kelly 1997). Regions most susceptible to acid sulphate soil formation are low lying areas near the coast including mangrove forests, salt marshes, estuaries and tidal lakes. The sulphuric acid produced can acidify the soil, soil water, groundwater and surface water, including tidal creeks. Acid affects the health of fish, plants and other organisms by reducing the ability to breed and increasing susceptibility to disease (Sammut & Lines-Kelly 1997). The sulphuric acid produced can also be strong enough to dissolve many man made materials including concrete, steel and some aluminium alloys. Acid has already been observed to weaken and corrode concrete slabs, building foundations and underground water and sewage pipes (Sammut & Lines-Kelly 1997). The effects of acid sulphate soil disturbance can have tragic short and long term effects. Rectifying and rehabilitating problems which have arisen from the disturbance of potential acid sulphate soils can be very difficult and expensive. It is very important that people learn about acid sulphate soils so that their disturbance can be avoided in the future and those areas which are currently affected can be properly managed to minimise the impacts (Sammut & Lines-Kelly 1997). Information on acid sulphate soils can be found at http://www.agric.nsw.gov.au/reader/8632 Northern Territory Mangrove Education Kit 23
Page 1 and 2: Mangroves in the Northern Territory
Page 3 and 4: TABLE OF CONTENTS WHAT ARE MANGROVE
Page 5 and 6: Plate 20: Avicennia marina (Grey ma
Page 7 and 8: What are Mangroves? Mangroves consi
Page 9 and 10: Harsh Conditions The coastal enviro
Page 11 and 12: Aeration through Roots Plant roots
Page 13 and 14: Mangrove Plants (Flora) Many plant
Page 15 and 16: Avicennia marina (Grey mangrove) An
Page 17 and 18: Ceriops tagal (Yellow mangrove) Cer
Page 19 and 20: Hibiscus tiliaceus (Beach hibiscus)
Page 21 and 22: Rhizophora stylosa (Stilt rooted ma
Page 23 and 24: Mangrove Zonation Why does Zonation
Page 25 and 26: The Seaward Zone Plate 45: Sonnerat
Page 27: Fish Plate 51: Periophthalmus sp. (
Page 31 and 32: This function is important particul
Page 33 and 34: Economic lmportance Tourism Mangrov
Page 35 and 36: lmpacts on Mangroves Coastal Develo
Page 37 and 38: Mangrove Monitoring and Protection
Page 39 and 40: Remote Sensing - A Management Tool
Page 41 and 42: Aerial photography has been used co
Page 43 and 44: Activity 1 Focus Question: Aim: Why
Page 45 and 46: Activity 3 Focus Question: Aim: Why
Page 47 and 48: Want more activities????? Greening
Page 49 and 50: acid, 34 acid sulphate soils, 34 Ae

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