Great Barrier Reef Summary PDF

GREAT BARRIER REEF SUMMARY Week 1 – spatial patterns and dimensions: location, altitude, latitude, size, shape and continuity – biophysical interactions including: – the dynamics of weather and climate – geomorphic and hydrologic processes such as earth movements, weathering,...

GREAT BARRIER REEF SUMMARY Week 1 – spatial patterns and dimensions: location, altitude, latitude, size, shape and continuity – biophysical interactions including: – the dynamics of weather and climate – geomorphic and hydrologic processes such as earth movements, weathering, erosion, transport and deposition, soil formation – biogeographical processes: invasion, succession, modification, resilience – adjustments in response to natural stress – the nature and rate of change which affects ecosystem functioning – human impacts (both positive and negative) – traditional and contemporary management practices. SPATIAL PATTERNS AND DIMENSIONS Location: Located off the North Eastern coastline of Australia (Queensland) within the tropic of Capricorn and the equator (the tropics) thus the climate is warm all year round Series of reefs 2300 km from PNG to Fraser Island The Great Barrier Reef World Heritage Area contains most of the reef, extending from the tip of Cape York in the north (9°15'S) to Lady Elliot Island (24°07'S), north of Bundaberg, in the south. The reef extends from around the 8 degrees south latitude in the north (close to Papua New Guinea) to just north of Fraser Island around the 24 degrees south latitude in the south. Latitude = good water temp for coral growth World Heritage Reef mainly between Cape York to just north of Bundaberg Altitude: 0m underwater but can reach up to 2m high in some places. The corals can actually grow up to 100m below the ocean Extent/Size: It is not a single barrier reef, as its name suggests, but consists of multiple reefs. 2900 individual reefs + 600 islands + 70 coral cays GBR Marine Park Area = 348 700km squared GBRMPA – Area size of Italy Shape: Northern: (narrow < 50km wide) Central: widens Mackay Region = widest Southern Region - narrows slightly Continuity: Reef is 1-2 km thick, 15 million years old, reef to the south is thinner and younger at 2 million years old The spatial dimensions of the reef are constantly changing. With climate change the reef could be unrecognisable within 30 years BIOPHYSICAL INTERACTIONS Note: Biophysical Interactions Case Studies = dynamics of weather and climate, geomorphic and hydrologic processes, biogeographical processes and adjustments in response to natural stress. Some questions will just say biophysical interactions others will be specific to one of the listed sub-headings. BIOPHYSICAL INTERACTIONS INCLUDING THE DYNAMICS OF WEATHER & CLIMATE Optimum growth: shallow water, 20-27 ℃, unpolluted, saline, high oxygen, low turbidity Heavy Rain: located in the tropics - Freshwater poding can occur after heavy rain as salt is heavier (fresh water pools on top of salt water), increased turbidity and run-off from flooding, elevated water level (slows coral growth as zookanthallae need sunlight for photosynthesis Wind: shapes the reef (aeolion erosion) and influences wave formation (SE winds contribute to cyclones) Cyclones: shape the reef and break corals. There is one TC approx every 6 years (the intensity and duration of these is significant to impact). Global warming has increased the frequency of TC - 9 in the past few years Water Temperature/Global Warming: ideal temp 20-27 ℃. If water remp too low zooxanthallae do not produce. Zooxanthallae are algae that live in the coral polyp (limestone coral structure). They provide the coral with foods via photosynthesis. If water temp too high, zooxanthellae will leave the coral polyp and cause a bleaching event 2026/17 successive bleaching events (prolonged warming of water). Strongest El Nino in 20 years. Less than 10% of GBR coral is unaffected by coral bleaching Recent scientific studies have shown that coral can adapt to gradual change…….. But what is the limit????..... We need to be precautionary Wind: For about nine months of the year, the south easterly trade winds make the water flow in a northerly direction (trade wind drift current). During the summer months, the dominant wind comes from the north-east and this reverses the direction of the current to flow to the south. BIOPHYSICAL INTERACTIONS INCLUDING THE GEOMORPHIC AND HYDROLOGIC PROCESSES SUCH AS EARTH MOVEMENTS, WEATHERING, EROSION, TRANSPORT AND DEPOSITION, SOIL FORMATION Hydrolic - cyclones and destructive waves can erode the reef - the millions of tiny air bubbles in waves that crash on the edge of reefs provide the necessary oxygen for optimal coral growth - currents - move sediment and deposits them - forms islands -Around 7000 cubic kilometres of water a day is flushed through the system by tides and currents. There are two currents which affect the Great Barrier Reef: The Trade Wind Drift Current and the East Australian Current (the EAC out of Finding Nemo!). Currents affect Coral Reefs in a number of ways. move sediment weathered and eroded from other areas to be deposited onto the reef to form islands, cays etc. bring to the reef the tiny organisms called zooplankton to help feed the variety of life bring plant life and seeds that colonise newly exposed sand bars Currents are used by many marine organisms to migrate for breeding Geomorphic land clearing leads to erosion - sediment/soil formation: sediment increases turbidity, reducing photosynthesis -Subsidence is where the lithosphere sinks either through the settling of sediment or a great weight has been placed on it. The GBR has sunk twice (last one 4 mill years ago). When the land subsides coral reefs are able to form as they are an aquatic ecosystem - if subsides too far coral can die - drift - reef moves to warmer waters - hydro-isostacy - caused by the weight of the water and release when the water levels were low. During ice ages the underwater land around GBR was exposed, the land rose as the pressure of the water was released. - Rifting - two deep rift basins have determined the shape of the continental shelf and the present distribution and shape of the reef - weathering - Since much of the coral reef is made of CALCIUM CARBONATE(lime) it is subject to chemical weathering - coral's lime shells are broken down by chemical reactions. Limestone is chemically dissolved by acid that is made by the mixture of rainwater and carbon dioxide from the atmosphere to form CARBONIC ACID. This then is deposited on to the limestone which then weathers down. Large waves and strong winds that are associated with cyclones may break apart and move large areas of coral. These large blocks of corals that are broken apart are called BOMMIES Physical weathering - physical (storms and waves) + biological egCoral browsers, such as parrotfish (break 90kg of limestone into sand annually). Worm species tunnel through corals using acid secretions, weakening the structure. BIOPHYSICAL INTERACTIONS INCLUDING: BIOGEOGRAPHICAL PROCESSES: INVASION, SUCCESSION, MODIFICATION, RESILIENCE - biologically diverse - one of the richest and most complex ecosystems on Earth eg 500 coral species, rare marine turtle breeds, 14000 dugongs, approximately 2000 fish species. - high degree of specialisation and endemic species eg green turtles - there are still many species yet to be discovered - invasion: crown of thorns predator feeds on coral tissue - releases digestive juices onto the coral, breaking down the polyp -leaves coral skeleton which is invaded by algae and borers - succession - Succession is the changes in a plant community over time until it reaches a state of balance with its environment. Organisms invade, colonise, grow, reproduce, and die on surfaces that were blank (primary succession) or replace plants and animals fromareas that have been disrupted (secondary succession). The succession of plants and animals continues until stability is reached. - plant succession occurs on the many exposed sand bars on the reef which form the many islands along it. - resilience - due to high productivity and biodiversity + large extent but there is a long recovery rate after intense stress (have low elasticity - depends on intenisty + duration) - high resilience to cyclones- Only some localised coral polyp populations are affected by cyclonic storm damage, while all populations are adversely affected by an increase in sea temperature. - less resilient to physical factors changing ie need shallow water, 20-27 ℃, unpolluted, saline, high oxygen, low turbidity - see below (can put adaptations in this heading and the one below) - parrot fish mucus bubble), Epaullete shark, coral spawning, toxic missiles, cross-breeding, sun screen” excretion BIOPHYSICAL INTERACTIONS INCLUDING: ADJUSTMENTS IN RESPONSE TO NATURAL STRESS - Species adaptations include the Epaullette shark walk on shallow tidal pools during low tide + has evolved to cope with the severe night time oxygen depletion (hypoxia) in isolated tidal pools by increasing the blood supply to its brain and selectively shutting down non-essential neural functions (ie turn off half its brain) - Parrot Fish - Sleep in a bag of mucus + Just one male + produce large volume of sperm that can fertilise a lot of females (no need for a large male population). In the case of a scant number of males, females can readily change sex. - corals submit defensive enzymes which may act as sun screens in both coral host and zooxanthellae - evolution of particular genetic strains of both coral hosts and their zooxanthellae - species diversity helps GBR respond to natural stress - annual coral spawning - disperse and grow - chemical defense - some 73% of all coral is toxic to fish- recent study fish began preying more often upon those corals that had more nutritional benefits, so those corals had to increase their levels of toxicity in order to protect themselves and survive - stinging cells on the end of coral tentacles that are used to sting, capture and kill off small prey and neighboring coral in a continuous battle for space. - corals, competing for space on a coral reef, will resort to aggressive behaviors in order to preserve their territory and ward off potential competitors. This often means physically attacking, and subsequently, digesting it's competition (toxic missiles) - The shape of individual reefs and coral cays is a response to prevailing winds, waves, currents and the relict topography. Storm damage creates greater diversity in reefs, even though in the short term the reefs are damaged, over time they are resilient. - Recent study some coral have genes to cope with warmer water (cross-breeding coral) - If high water temperatures, fresh water, nutrient overload or sediment blanketing stresses a coral polyp, it usually expels the zooxanthellae and dies. This is called coral bleaching and the cause is not always natural +great debate on whether infestations by the poisonous crown-of- thorns starfish are naturally reoccurring phenomena or not & whether the Great Barrier Reef has adjusted to these natural stresses. Bleached corals are at a greater risk of mortality, although they may partially or fully recover, depending upon the environmental conditions - The ability of corals to adapt to environmental stress is fundamental to understanding evolutionary change over geological time and to prediction of coral reef survival under increasingly stressful conditions of altered climate and pollution. Coral reefs are not stable communities living in benign environments but ecosystems that are subject to frequent physical disturbances on time-scales, which vary from minutes to years. Corals have responded to these physical fluctuations by a variety of phenotypic and genetic adaptations. THE NATURE AND RATE OF CHANGE WHICH AFFECTS ECOSYSTEM FUNCTIONING - periods of reef growth and decline in relation to water depth - Aust sea level rise 12-16cm in the last 100 years - if water temp rises slowly scientific sudy shows coral can adapt - but not if fast and nobody knows to what temp ultimately will die - change affects the Great Barrier Reef on a variety of scales, from daily tidal fluctuations to seasonal changes and the longer-term changes associated with changes in sea level. In recent years, human-induced changes have accelerated the nature and rate of change - sea levels on GBR - sea level rise 12-16 cm past 100 yrs - Crown of thorns infestations frequent outbreaks in recent yrs - low elasticity (rate of recovery) 12-15 yrs for coral to get back to pre-infestation levels - Coral Bleaching occurs when the water temperature drastically changes, for a period of several weeks that it exceeds the coral polyps tolerance (usually around 30 degrees Celsius). The polyps eject their symbiotic zooxanthellae before they die. This allows the white limestone exoskeleton to show and hence are said to have bleached.The severity of bleaching can vary substantially according to water depth, location and species of corals. The Rate of Change. If stressful conditions continue long enough, bleached corals will die. However, if stressful conditions fade away, then the bleached corals can recover their symbiotic algae and return to their normal, healthy colour. If stressful conditions continue in particular regions, large areas of coral reef can be affected in what is known as a mass-bleaching event. The Great Barrier Reef (GBR) suffered widespread coral bleaching in the first half of 1998 - Greenpeace scientific study - if climate change is not stopped, coral bleaching is set to steadily increase in frequency and intensity all over the world until it finally occurs on an annual basis between 2030 and 2070 - Most robust corals on the reef have slowed its growth by more than 14% since 1990 - Declining growth rate will completely stop by 2050 if nothing is changed Climate change - continuum will result in the intensity and frequency of bleaching worldwide HUMAN IMPACTS: POSITIVE AND NEGATIVE NEGATIVE - since 1985 coral has declined from 28% to 14% in 2/3rd of the reef - The northern areas remain in good condition, while the inshore areas in the southern two-thirds face the greatest challenges - CORAL BLEACHING - the fifth mass bleaching event the Great Barrier Reef has experienced in just eight years, and the 2024 event is feared to be the most widespread and damaging to date. “The coral crisis is a climate crisis” - Global community believes Australia has poor emissions targets - 2024 74% bleached (of these - half high,