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Intertidal zones in the Great Barrier Reef A field guide for Whitsunday Sea kayaking journeys LIVING BETWEEN THE TIDES IN THIS ISSUE Introducing the Intertidal Zone Picture: Whitehaven Beach (Darren Tierney Photography, 2011) Retrieved from: http://www.qualia.com.au/aboutqualia/destination/whitsunday-islands by Bree Tivendale 18068168 The intertidal, or littoral zone, is defined by the high and low tide. During high tide the zone is completely covered with sea water, and at low tide the area is exposed. This biome is therefore extremely variable and includes different bioregions. These include mangroves, mud flats, the reef crest, rocky shores and sandy shores. Bree Tivendale 1 80681 68 The intertidal zone can be broken down into 4 sections depending on the amount of time they spend submerged (Marine Society of Australasia, 2000). The lower intertidal zone is found closest to the low tide mark and spends the most amount of time underwater. The high intertidal zone is found closest to the hid tide mark with the mid intertidal zone found in the middle. Above the high intertidal zone is the splash or spray zone. Although this zone is rarely ever submerged, it is sprayed by the splashes of larger waves and is therefore still exposed to littorial action. Different species can be found at different levels of the intertidal zone based on these 4 sections and the amount of time they spend under water (Marine Society of Australasia (2000). Diagrams drawn by Breanna Tivendale (2015). Adapted from the Marine Society of Australasia (2000). Original image retrieved from: http://www.mesa.edu.au/friends/seashores/zonation.html INTERTIDAL ZONE IN THE GREAT BARRIER REEF 2 Living in the Intertidal Zone Intertidal Environments: Beach Rock NOT AS SIMPLE AS GOING WITH THE FLOW This bioregion is always changing with the tides usually coming in and out at least twice a day with a battering force (Davey.K.,2000). Not only do organisms have to deal with being exposed to water then air multiple times a day, as well as the sun and highly variable temperatures, they also have to defend against a variety of terrestrial and marine predators (Davey. K. 2000). This has cause these littoral species to be quite unique, with specific adaptations to survive this array of environmental pressures. Some physiological adaptations include camouflage through attaching plant matter to the individual, having a shell that can hold in water and provide protection from waves and predators. There are also behavioral adaptations such as hiding under rocks or in crevasses from predators and the sun. A Study conducted by Jason Sheehan from Queensland University (2012) found that the average temperature difference between above rocks and below rocks differed by 5.5 degrees Celsius. The temperature below the rocks remained within narrow limits to the temperature of the water during high tide. The organisms in this document are organized into their biological classes. Malacostraca are commonly called crabs, Maxillopoda are referred to as Barnacles. All species listed are found in the Whitsunday’s area. The rocky shore environment has been focused on due to its higher level of larger organisms that are easier to identify. There are many more species to be found in this environment, some of the species identified are still in need of further study to understand their place in the ecosystem and to identify different adaptive behaviors. Great care should always be taken in this environment to ensure no harm is done to the ecosystem or to the individual. Do not remove any organism or other objects from their habitat and take extreme caution if turning over rocks. Avoid touching any organism and always return rocks to their place. Taken by Sandie Degnan (2015). Retrieved from: http://www.gbri.org.au//Habitats//Beachrock Malacostraca Menaethius monoceros: Also known as the Spider Crab or Decorator Crab. Can be found in the intertidal zone and upto a water depth of 90m. This crab is know for camuflaging it’s self by ‘decorating’ it’self in seaweed and algaea’s. It therefore requires the presence of algae and other sea plants on rocky shores. Females typically are the largest in this species. Students at Queensland university recorded a female of 1.3cm and a male of only 0.9cm. It has a distinctivly shaped body which is covered with plant matter (Chiu Lo. C. 2014) Taken by Denis Riek (2013) Retrieved from: http://www.roboastra.com/Crustacea6/hpde214.html Eriphia sebana: Also known as the Red-eyed Rock Crab. Males of this species can grow anywhere between 39.2mm to 57mm in length with females getting as big as 36mm. These crabs can be identified by their stocky build and their obvious red eyes. However they are inactive during the day time, coming out only at night to feed on molluscs and anything else it can find. Stimdromia lateralis: Also known as the Ridged Sponge Crab. This species has an adverage carpuce length of 29mm and can be found in a variety of intertidal environments including sand, mud, corals and algae beds. They are typicaly orange to dark red or brown in colour with their Chelipeds (claws) being of a similar length. The term ‘sponge crab’ comes from their behaioural adaption to carry sponges on their backs. These little crabs can be distinguished from similar speices by their last leg, which points the same direction as all it’s other legs(Chan.C. 2014) Gastropoda Terence Tan (2011) Planaxis sulcatus: Also known as a Furrowed Clusterwink or a Tropical Periwinkle. They are known to have shells that grow to around 35mm in length with females growing larger than males. They can be found in both the upper and lower littorial zones but are inactive during low tide. The coils around their shells are called whorls. The patterned whorls are often covered by a range of parasites covering them (Tan.T. 2011). INTERTIDAL ZONE IN THE GREAT BARRIER REEF 3 Intertidal Environments: Beach Rock Bornella stellifer: Also known as Starry Bornella Nudibranch. Unlike most invertebrate in the Gastropoda family these organisms donnot have a procetive shell. They only grow to around 24mm-48mm but reduce their size by almost a third during low tide when they undergo desication. They have red geometric patterns along their bodies and head with a translucent body. Godiva sp.: This species of Gastropoda also lack a shell. They can grow to around 1037mm long and are found in the lower littoral zone. Cerata are located in patterned clumps along their backs and can extend to as long as 12mm when the organism is distressed. The species lay their eggs in coiled ribbons and look like yellow apple peels. These are laid in an anti-clockwise direction. Turbo militaris: Also known as The Military Turban can grow upto a large 120mm in length. Their outerlip is sharp surrounding their almost round appeture. Their shells have dark green and bown bands. These Gastropods can be found mostly in northern NSW, but also along rockyshores in QLD. Although they are large, they are hebivourious feeding mostly on algaes (Chin Wai.C.2014) Polyplacophora Manning.F.2014 (2014) Morula marginlba: Also known as the Mulburry Whelk. These are predators of the intertidal zone feeding on oysters, barnicles, limpets and other gastropods. The spiral rows of noudules are said to look like mulburies, giving this species it’s common name. They usually grow to around 20mm but have been seen upto 35mm in length. Their shells come in different shades of brown, grey and black. Will not be found where there is intense wave action (Manning.F.2014). Cypraea caputserpentis: The Sperpents Head Cowrie is found in the intertidal zone near tropical reefs. It’s shell is oval, shiny, smooth and brown with white bloches. It’s underside it light in colour with it’s appeture looking like teeth. This species does not like the light and is normally found under rocks. They can be seen feeding on algae or coral animals including sponges and small crustaceons after dark ( Wong.S.Y. 2014) Athousis.C. (2011) Acanthopleura gemmata: Also known as a Chilton. This species is quite unique in appearance with 8 overlapping plates acting as a shell. They can grow to roughly 12cm, but have been seen upto 14cm in length. They are found attached to rock in littorial zones grazing on microflora. They returne to a ‘home scare’ everynight but it is unclear how they find their way back as they have no cephalic eyes. It’s believed they may use light recreptors in their shells to ‘see’. Chilton were used by Aboriginals as food. If disturbed the Chilton will roll up in a ball simlar to an armadillo (Athousis.C. 2011). INTERTIDAL ZONE IN THE GREAT BARRIER REEF 4 Intertidal Environments: The Reef Crest Macroalgae Exposed reef tops are home to an abundance of life, often including a rich algae layer (Zell.L.,2012).Macroalgaes, also known as seaweeds, come in 4 different varieties; Bluegreen Algae, Red Algae, Brown Algae and Zooxanthellae ( Marine Education Society of Australia, 2004). Species of algea on the Great Barrier can range immensly in size from just millimeters to 3 or 4 meters high. Each different algae species proforms a different role in the reef ecosystem which would not survive without these algae. Species of algae can be seen growing on rocks and water surfaces in the intertidal zone (Marine Education Society of Australia, 2004). A species of Red Algae (picture below) is one of these algaes. Reef Crest (Zell.L.,2012) Intertidal sponge (Zell.L.,2012) These organisms have to withstand great forces from waves every day and must have firm attachment to the surface below them. They are also exposed to weather and events such as cyclones with often leave the reef in servere damage. Similarly to the invertebrates that live on the rocky shores, these organisms have had to adapt to their exposure to the air and sun. when they become exposed at low tides the soft part of the coral, called the polyp, are retracted using the harder skeleton of the coral as protection (Zell.L.,2012). The coral in the picture to the left has secreted a purpled protective mucus. This is an adaptation to help provent the coral from becoming burnt and is used by many species (Zell.L.,2012) Red Algae (Moetary institute for Technology and Education, 2015) Algaes provide a major resourcee for a range of organisms forming the base of the reefs eosystem. Not only do they fuel the basis of life on the reef they also are vital for some orgnaisms as protection including many of the Malacostraca listed on page 2. As plants, algae undergo photosyntheseis, removing CO2 from the water and replacing it with O2. They also trap nitrogen from the water in their structure with makes it available for hebivors who would other wise not be able to injest this, and other, nutrients (Great Barrier Reef Marine Park Authority, 2008). The reef crest is located between the Back Reef and the Buttress Zone. It’s a raised part of the reef that protects the lagoon and shorelines from the force of the waves(Queensland Museum Network, 2015). It can become exposed during low tide making it an intertidal environment. It is compromised of n intertidal algae pavement and a coral shingle zone (Queensland Museum Network, 2015). There are many different species of coral, sponges, algae and many other found in this environment. Exposed coral with protective mucus (Zell.L.,2012) The Parrot Fish have specially designed heads and beaks to scrape away at corals forming sights for new corals to settle (Kerry.J. 2013). Below is an image Taken by the Living Oceans Foundation of a school of Bolbometopon muricatum swimming across the reef crest below the waves. Algaes found in the intertidal zone are usually more ridged and fleshy than other species. They form distinct lines on the rock beds acording to the littorial levels they function in. There are usually a diverse range of algaes found, but populations are usually sparse (Great Barrier Reef Marine Park Authority, 2008 Picture retrieved from: http://www.livingoceansfoundation.org/photo/great-barrier-reef-album/