Marine Invertebrates
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Zoanthids Contents 2 Visiting Port Davey 3 When to visit 3 What’s protected? 3 Why marine reserves are important 4 The Marine Reserve 4 From the air 4 Underwater 5 Unusual water features 6 The Marine Life 6 What lives where? 8 Marine invertebrates 14 Fish, sharks, rays and eels 15 Seaweeds and seagrasses 16 Biosecurity at Sea 16 Marine pests 18 Biosecurity on Land 18 Root rot 19 Chytrid frog fungus 19 Other plant and animal pests 20 Aboriginal Heritage 22 European History 26 The Landscape Port Davey Marinemap andReserve notes 29 The Weather This visitors’ guide is accompanied by 30 Threats the Port Davey Marine Reserve map 31 Further Reading and notes which contains information 32 Acknowledgements on zonings, limits, biosecurity, boating, 33 Contacts diving, kayaking, camping and walking. 1 Visiting Port Davey The Port Davey Marine Several hundred boat-based visitors arrive each year, including yachties, sea kayakers and scuba divers. Commercial and Reserve is located in recreational fishermen sometimes enter the reserve seeking the far south-west of shelter from the weather. A further 5000 or so day visitors the State, within the arrive each year by light plane to participate in harbour cruises. Southwest National Occasional cruise ships also visit, under strict regulation. Park and the Tasmanian 146°24'0"E Wilderness World 43°4'0"S Heritage Area. It is accessible only by boat, light plane or on foot. Svenor Marine Reserve Pt Southwest CA Southwest NP & WHA boundary Bathurst PORT DAVEY Harbour Soft coral Cox Bight South West Cape De Witt Island SOUTHERN OCEAN 43°38'0"S 2 145°36'0"E When to visit What’s protected? Seastar South-west weather is often The Port Davey Marine wild, wet and unpredictable – Reserve (17 753 hectares / 178 it’s this weather that has played km2) extends inland for more a large part in shaping the than 20 km to the north and landscape. It is not uncommon east, up to the high water mark to experience day after day of all rivers, bays and estuaries. of rain at any time of the year. Within its boundaries, the However, more settled weather reserve protects all marine life is usually experienced during and all habitats, including open summer and autumn, with less ocean, exposed reefs, steep Why marine reserves are rain and less wind – northerlies gorges, bays and inlets, kelp important in summer and westerlies forests, seagrass meadows, and We need marine reserves in autumn. Spring winds are muddy and gravelly sediments. for the same reasons we often strong and gusty, while Declared in 2005, it is presently need national parks on winter brings strong prevailing the only protected area within the land – to conserve westerlies, low temperatures, the Davey Bioregion – one of our plants, animals and frosts and high rainfall. If you’re Tasmania’s eight continental landforms for future lucky, you can strike a week shelf marine bioregions. generations. Port Davey of perfect crisp, calm weather Marine Reserve is part in the middle of winter. Get a of a system of marine long-range forecast and cross reserves the Tasmanian your fingers. If you’re seeking Government is creating to solitude, avoid visiting between ensure that representative mid-January and mid-March. samples of our diverse marine ecosystems are protected from potentially damaging human activities. Their conservation and sustainable use is everyone’s responsibility. 3 The Marine Reserve From the air Underwater Sea pens This region must surely be The underwater landscape one of the most magnificent is even more surprising. In landscapes on the planet. Bathurst Harbour and Bathurst Gold-green ranges, with bony Channel a very unusual marine quartzite ridges, rise sharply environment has been created from the southern ocean and by a deep layer of dark red- the broad interior waterways of brown, tannin-rich freshwater, Port Davey. which overlies tidal saltwater. Four major rivers and numerous The tannins restrict sunlight creeks cut through gorges penetration to the top few and snake across open plains, metres, limiting the growth of draining their rust-coloured marine plants. In their place live waters into the marine reserve. colourful and delicate marine Small islands dot the surface of invertebrates. In the clearer the dark waters. White quartzite marine waters of Port Davey – sands fringe the shoreline. Mt away from the influence of the Rugby – the highest and most freshwater tannins – a more prominent peak bordering the typical Tasmanian underwater reserve – rises grandly from world exists. Diverse kelp the western shore of Bathurst forests and abundant fish thrive Harbour. On a fine, calm day beneath the surging Southern the marine reserve’s waters Ocean waves. reflect the landscape to endless The marine reserve was perfection. created to protect this extraordinary underwater world. 4 Unusual water Low nutrient levels It is highly unusual for an estuary features to have low nutrient levels, Dark, layered water as the waters that drain into When freshwater meets them usually contain sediments saltwater, layering occurs rich in nutrients. In the south- because freshwater is lighter west however, the waters have in weight than dense saltwater. drained through the nutrient- Within the marine reserve, poor, shallow soils of eroded this causes the dark band of quartzites. tannin-rich freshwater to sit The low nutrient levels affect on top of the clear saltwater. the entire food chain, with less This phenomenon is known plankton, less fish and less as stratification. In Bathurst filter-feeding invertebrates, Harbour and Bathurst Channel, other than at locations with the freshwater layer is at its rapidly flowing currents. deepest – around 4 m – in The marine invertebrates in winter, when rainfall is highest. Bathurst Channel and Bathurst The narrow zone where Harbour exist in – and rely on – freshwater meets saltwater this low nutrient environment. is called the halocline, or salt Any increase in nutrients gradient. Mixing of the halocline can poison the animals and disturbs marine life, as some encourage invasive species. species have adapted to live in either fresh or saltwater. Discharging boat sewage and sullage increases nutrient Reducing boat speed helps levels. Boat owners are avoid mixing the fresh and encouraged to discharge saltwater layers. outside the marine reserve. PORT DAVEY BATHURST HARBOUR fresh tannin layer halocline salty wedge seabed 5 The Marine Life Port Davey 0 What lives where? dilute tannin layer bull kelp Different species live (mixed with salt) brown and red algae in different places blue-throated according to the amount wrasse of tannin and nutrients, sponge type of sediments, 5 speed of currents and purple wrasse wave action. abalone hula fish rock lobster sponge 10 Port Davey is exposed to the Southern Ocean’s currents and waves. Its shoreline includes exposed cliffs, islands, sheltered inlets and sandy beaches. These habitats support a variety of seaweeds, fish and invertebrates, with occasional visits from marine mammals. Further inside the port, in Payne Bay and east of the Breaksea Islands, the marine waters are mixed with tannin freshwater flowing out from Bathurst Channel and the Davey River. 6 Neptune’s necklace Bathurst Channel Bathurst Harbour sea lettuce mussels 0 0 tannin layer brown and tannin layer brown algae Neptune’s red algae necklace red algae encrusting Maugean skate corals soft coral 5 5 lace bryozoan sea cucumber anemone fan bryozoan encrusting tube worms sponge Bramble coral heart urchins bryozoan brittle star 10 10 biscuit star solitary sea pens ascidian sea urchin colonial ascidian Bathurst Harbour’s shallow waters (5-7 m deep) are strongly influenced 15 by tannins in the freshwater draining from the Old and North rivers, and myriad creeks and rivulets. Heavier finger sponge sea anemone saltwater lays beneath, carried in zoanthids tidally from Port Davey. In the inky stony dark harbour waters, phytoplankton coral cup sponge and marine plants struggle to survive. Few invertebrate species live 20 on the muddy harbour floor, although Bathurst Channel connects Bathurst Harbour with Port Davey. The heart urchins, sea cucumbers and centre of the 12 km long narrow channel varies in depth from 15 to polychaete worms are common. 40 metres. Tannin freshwater enters from Bathurst Harbour, the Spring Dogfish and skates move about the River and numerous creeks and rivulets, as well as tidal saltwater from seabed. Port Davey. The dark waters restrict growth of seaweeds to the top few metres. Below this, a magnificent display of colourful invertebrates attach themselves to the rocky channel walls and seafloor reefs. 7 The Marine Life Marine More than 500 species of There are single animals, like marine invertebrates (animals sea urchins and seastars, and invertebrates without backbones) have been colonial animals, which look Bathurst Channel is the recorded, with many still to like one animal, but are in fact jewel of the marine reserve, be described. Some, such as hundreds of tiny animals living anemones and zoanthids, bear together. There is safety and however if you were to travel more resemblance to flowers efficiency in living as a colony. over these dark waters, you than animals. Most do not move, Each animal within a colony has could be forgiven for thinking anchoring themselves firmly to a particular function – some nothing much was going on the seafloor or channel walls, gather food, some strengthen down below. With the aid of where they feed on other the colony and others even a strong torch, highly skilled marine animals, or filter-feed clean the colony! scuba divers illuminate the plankton and nutrients from the Many of the marine dark depths to reveal an swiftly flowing passing current. invertebrates found in Bathurst incredibly beautiful world Channel are usually found of exotic creatures. The in much deeper and often following pages provide inaccessible ocean waters.