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76 Cards in this Set
- Front
- Back
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How are tides generated? |
A combination of 1. influence of the moons gravity, 2. the rotation of the moon and earth system, and 3. the rotation of the earth on its axis. |
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What are the difference between Spring & Neap tides? |
Spring tides - the sun and moon are aligned with the earth, resulting in the strongest rise and fall in tidal level. (low low and high high tides) |
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What determines whether a location has a diurnal or semidiurnal tide? |
This depends on the surrounding bathymetry and the earth's declination. Surrounding land masses block can block the passage of tidal bulges, resulting in the formation of complex tidal patterns all over the world. |
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What impact does the Coriolis effect have on tides? |
As earth is constantly rotating east at different speeds at different latitudes, rotation is fastest on the equator and slowest towards the poles. The coriolis effect forces moving objects to follow curved paths. In the Northern hemisphere objects move to the right, and in the Southern hemisphere objects move to the left. As a result ocean basins in the Northern hemisphere are clockwise, and counterclockwise in the Southern hemisphere. |
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What is a tidal bore? |
A bore caused by the constriction of a tide entering a shallow inlet, resulting in a 'wave'. |
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How are waves generated? |
Combination of the wind pushing water molecules into ripples, the interaction between moving water molecules, internal friction of the watermass, and friction with the sea floor. |
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How do waves move and what happens to a wave as it approaches the shallows? |
Waves move in a circular orbital motion as the water particles transmitting the wave move forward in a circle due to intermolecular attraction. As the ground becomes shallow, the water begins to move in an elliptical shape and wave speed decrases. The top of the waves are moving faster than the bottom, resulting in breakers. |
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What is wave refraction? |
Refraction is the changing velocity of waves due to varying water depths below. This occurs when waves approach shallow water - the wave in shallow water is moving slower, resulting in bending. Refraction occurs around islands or headlands. |
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What are the main types of waves? |
Slipping breakers: occur on gently sloping or flat beaches. Spill gently over |
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What is "fetch"? |
Fetch: The distance from where a wave has travelled before breaking. Bigger fetch results in a larger wave. Good method to estimate wave exposure. |
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How can wave energy be quantified? |
Wave energy is difficult to quantify as it requires pressure transducers to measure force, integration over time and calibrated erosion methods. Surrogates (e.g. wave height/direction, fetch) are often used. |
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What influence to ocean currents have on a global scale? |
Ocean currents drive broad scale taxon distribution, particularly corals, drive global weather patterns and influence ecosystems on a global, regional or local scale. |
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What drives sediment distribution? |
1. Exposure to wave energy |
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Name three sources of sediment. |
1. Major streams deposit fine sediment (mud) into coastal areas. |
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How does water velocity sort sediment particles? |
Sediment is easily picked up and carried by water. Larger particles are denser with a lower sa/vol ratio, and are dropped first as they require a higher velocity to carry. Small particles are dropped at low velocities. This operates on a range of scales. |
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What are the size classifications of sediment grains? (finest to largest) How does grain size effect the biology of an area? |
Mud (Clay, fine silt, coarse silt) fine sand, coarse sand, shingle, cobbles, boulders, cliffs, planet... |
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What is Flocculation? How does this occur during Mud transport? |
Flocculation occurs when water containing sediment (from a river) mix with seawater. It involves the coalescence of separate molecules through attraction. Van der Waals forces attract silt particles to water molecules, which clump together. When this bond is broken, the mud falls out of suspension - "floccules". Floccules generally accumulate in mud flats or areas of high turbidity along the river to sea gradient, e.g. protected locations behind barrier islands, and settle higher on the shore. (tidal asymmetry) |
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Explain longshore drift. |
Waves can hit the shore at an angle, washing back sediment as the water recedes. The sediment can then be moved down the shoreline in a zig-zag pattern, with sediments being deposited further down the shore. Longshore drift is important in building beaches and dunes or spits. If interrupted, sand can build up on upstream side with erosion on the downstream side. Sand bypass stations can aid this issue. |
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Salinity |
Operates at scales from local to global, can vary with tides, seasons, extreme weather. Can be abrupt horizontally and vertically (haloclines). |
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Describe rocky shore environments |
Rocky shore ecosystems are a 2d environment, frequently exposed to the elements with a lack of shelter from physical/thermal stresses, predators and competition. Wave energy and thermal stress means only specially adapted organisms can survive. Most have a shell or exoskeleton, are slow moving or sessile. |
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Describe zonation on rocky shore environments and universal tripartite zonation |
Earliest observations on rocky shores notes distinct verticle bands known as "zones," which are similar all over the world. |
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What gives the "zones" such clear boundaries? How are vertebrate distributions controlled on rocky shores? |
On the upper boundary, tolerance to abiotic factors like dessication and thermal stress is the controlling factor, while on the lower levels biological interactions like predation and competition are the controlling factor. Higher the waves reach, higher distribution of rocky shore organisms. |
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Describe three adaptations to life in a rocky shore environment |
1: hang on - limpets and barnacles. streamlined shape, extremely strong suctorial foot. |
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Why are rocky shores dominated by algae producers (liche, cyanobacteria, algae, seaweed)? |
No soil, no plant competitors, firm surface for attachment, plenty of light, little sediment, waves provide water and nutrients for photosynthesis. However grazers limit algal biomass & distribution with specialised structures (radula) and behaviours (homing) |
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Describe the sub-littoral zone |
Important source of nutrients to intertidal zone. Dominated by kelp / giant kelp. Highest primary production rates on earth - sequesters 1000g carbon/m2 per year. Most production is not directly grazer- eroded as dissolved organic matter / particulate organic matter |
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What effects does grazing have on algae? |
Limits distribution and biomass. Seems to determine upper limit of macroalgae - lower limit set by competition between algae species. Grazers can eat microalgae and newly settled macroalgae, but not established microalgae. |
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How does grazing effect other fauna? |
Grazing may remove newly settled organisms eg. tubewarms, barnacle larvae. However this can create space for larval settlement from other organisms. Also mediates competition for good. Grazers are preyed on by gastropods, crabs, starfish, fish and birds. Size limited - predators seek smallest prey. Juveniles frequently targeted. Grazing can sometimes get out of control e.g. urchin pops removing kelp forests for over 10 yrs. |
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What do the major predators on Rocky Shores have in common? (e.g. starfish,predatory gastropods, crabs) |
Heavily constructed, relatively slow moving - main predator strategy is muscle rather than speed. Usually hunt at high tide when water is covering prey and they are exposed. |
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What defences to rocky shore prey use to defend against predators? |
Defensive structures - spines, sharp edges (bivalves) |
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What are the effects of predation on prey species on rocky shores?
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- Prey gets eaten |
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What causes competition on Rocky Shores? |
- Space: to settle as larvae, grow, feed, shelter, reproduce |
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How do grazers mediate competition between algal species? |
The colonization of one algal species can prevent settlement of competitors. Grazers clear space, allowing settlement and preventing dominance by a single species. Can be modified if grazers are selective. |
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Describe how the importance of competition and predation on rocky shores changes depending on exposedness / geographic area. |
The importance of either depends on community complexity, relative exposure, physical factors that limit distribution & resilience of prey species. In simple high lat systems, competition is more important in exposed sites, predation in sheltered. In complex lower lat systems, recruitment and disturbance becomes more important. |
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What is the benefit of having a '3rd dimension' in soft shore environments? |
Allows organisms to live in volume rather than a surface. |
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Which are easier to study - rocky or soft shore? |
Rocky shore much easier to study due to 2d substrate. Soft shofts have mobile sediments, changing levels, volumes, grain size and constant reworking of environment by burrowing organisms. |
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What size classes of organisms live on the soft shore? |
Micro - living on grains (diatoms) |
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Discuss bioturbation and how this changes ecosystems. |
Bioturbation involves burrowing - considered 'ecosystem engineers.' Strong driver of biogeochemical reactions on soft shores & mangroves. Can influence sediment biogeochemistry. e.g. |
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Discuss vertical environment gradients, redox conditions, RDL, and why sands appear black on some soft shores. |
Oxygen concentration decreases exponentially with depth, as does redox potential. At some point potential becomes negative (reducing conditions). Species are different below this level - chemoautotrophs and aerobic heterotrophs which do not require light or oxygen. Shift of energy production from carbon, to using nitrate, to using sulfate (produces sulfide - black layer). Location of RDL depends on wave energy. |
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How is food sourced differently at exposed & sheltered shores? |
Exposed beaches are primarily allochthonous - rely on nutrients from outside system aside from small amount of food from surf diatoms |
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Why does a a detritus based food chain become more important with decreasing sediment size? |
The retention of organic matter in fine grains makes detritus a convenient food source. This, combined with increases in macrophytes & food production means more organism support. |
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Discuss the positive and negative effects of burrowing for soft shore organisms. |
Advantages: -Secure place, less affected by disturbance |
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What are the main drivers of shore morphology? |
Waves, currents, substrate, slope, wind |
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What are the 3 types of shore? |
1. Dissipative - large number of breakers in surf zone, wide surf zone, gentle slope, fine particles, indistinct cusps & horns. Biologically rich, low wave energy 3. Intermediate- Narrow surf zone, steeper gradient. Most common. Can move towards reflective with heavy storms. |
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What are the key features of tsunamis? |
- Extremely long wavelengths |
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What 3 mechanisms form nearshore bars? |
1. Interaction of reflected & incident waves |
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Define cusps, horns & how they form. |
Cusps: semicircular shoreline formations made of grade sediments in an arc pattern. Occur when waves break directly onto the beach |
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What is a longshore current? What are rip currents & how do they form? |
The longshore current runs parallel to shore, and is generated from energy when a 'train' of waves reaches a beach or coastline. |
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Why don't exposed beaches support macrophytes? |
- Dynamic: erosion, deposition, unstable substratum |
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Why do surf diatoms migrate during the day/night? |
Diatoms migrate upwards during the day to photosynthesize and descend during the night. Their attachment to air bubbles during the day allows them to photosynthesize & multiply, and sink with sand grains to the bottom to escape predators during the night. |
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List strategies to maximise feeding opportunities and avoid predation on an exposed sandy shore. |
Debris provides habitat & food to invertebrates on exposed beaches. Organisms that wash up onto the beach often do not live in the ecosystem, but add to the food supply. Most micro/macrofauna are filter feeders, scavengers, opportunists. |
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What is the function / benefits of tidal migration on exposed sandy shores? What are costs? |
Tidal migration allows some species (eg. pipis) to feed in optimum conditions and avoid predators which are unable to forage in heavy surf. e.g. Pipis surf with their food and siphons extended to ensure they maintain their position at the waters edge. However the metabolic cost of constantly burrowing up and down is high. |
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How to mangrove / seagrass / salt marsh distributions on sheltered shores differ depending on latitude? |
Tropics - Mangroves thrive |
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What impact does bioturbation have on sheltered shores? (stabilizing / destabilizing) |
When burrows are abundant & close together, they restrict movement of water, skim flow & protect area from erosion. |
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Why are sheltered shores important for migratory birds? |
Birds migrate for 400+km during migration and fly for 3-5 days non stop during each leg. They can lose up to 50% of their bodyweight during this trip. As a result, wetlands and sheltered shores along the flyway are important for birds to be able to stop, eat, refuel and rest. Moreton bay is an important stop along the Oceanic flyway. |
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Whats the difference between a mangrove and a salt marsh |
Mangroves mainly woody plants, adapted to intertidal life. Salt marshes are herbaceous shrubs. Both are halophytes that provide a 3D environment. Dominance depends on latitude - mangrove dominant on tropics/subtropics, salt marsh dominant on subtropics/temperate. |
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How have mangroves adapted to survive in saline conditions? |
- Salt excretion through leaves |
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How have mangroves adapted to survive in fine, mobile, anoxic sediments? |
- Widespread root systems with vertical extensions (pneumatophores), lenticels to allow gas exchange |
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Mangroves and saltmarshes are valuable and productive ecosystems. Name some services mangroves & saltmarshes provide |
-Protection from predators from juvenile nekton |
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What are the biggest threats to mangroves? |
- Organic pollution - sediment runoff in catchments, estuaries, agrucultural runoff |
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What are some effects of flocculation on mudflats (particularly regarding nutrient / pollutant effects) |
Phosphates are a key nutrient for plants and 80-90% of ohosphate is locked up in sediments via flocculation, as well as many other ions (mercury, lead, cadmiun). This had implications for bioavailability and plant growth. |
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Are mudflats vegetated or unvegetated? What inhabits mudflats? |
- Rooted plants dont grow, too anoxic except for plants with adaptations. |
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Why does biomass increase in temperate conditions on mudflats and drop near the equator? (Opposite to other biological trends) |
The high water content and extremely hot conditions makes mud very difficult to survive in at the equator. Temperate mudflats are far less extreme. |
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How do corals generate energy? |
Most energy comes from Zooxanthellae, single celled algae, which fuses onto coral. Corals seek light like plants to allow zooxanthellae to photosynthesize. Only 2-8% of energy comes from food they capture. |
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Describe how corals reproduce. |
Sexually - broadcast spawning. Diecious & hermaphroditic species. Synchronised spawning to maximise fertilization chance. When egg is fertilized it will drift and settle in suitable substrate within 4 days. |
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Identify / describe the main agents of coral growth and how they work together. |
Bricks- Coral secretes hard calcium carbonate - silicon for sponges. Main structures. |
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What are the sequences of reef types in the growth of a coral reef? |
Isolated pinnacles - Incomplete ring - Completed ring - Partially filled with distinct lagoon - Completely filled. Corresponds to previous growth stages from pre-existing subtidal platforms - pinnacles grow first, reach the surface and spread laterally and leeward, eventually fill the platform. |
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What conditions are necessary for coral growth? |
- Warm water around 20C |
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Describe the "types" of coral reef colony. |
1. Fringing reefs - Grow around a geological structure e.g. islands, sandstone. |
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Differentiate between natural & anthropogenic disturbances. |
Ecological disturbance - cyclones, floods, thermal stress, periodic plagues (crown of thorns) |
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Why are anthrophogenic disturbances worse than natural? |
- Can be catastrophic and sometimes permanent |
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What are some common side effects of severely disturbed reefs? |
- Urchins everywhere - overfishing results in no fish predators to control urchin populations, unbalances ecosystem |
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How can natural & anthropohenic disturbances cascade to less diverse states by decreasing resilience? |
Normally: healthy, natural periodic disturbance, recovery |
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What is the most common human caused issue on coastal environments? |
Eutrophication - excessive nutrients from sewage, urban runoff, agriculture. Usually natural sequence, now usually human related. |
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Moreton as an example: What effects have human impacts had on the Moreton bay ecosystem? |
-30x more sediment than pre-settlement levels. Lots of sewage effluent due to sewage treatment center. Mangrove dieback at luggage point. Seagrasses in decline. Lynbya (fireweed) blooms. Pimpama river weir - upstream nutrients are backed up, phytoplankton grows dies and throttles oxygen, oxygen dropped to 25%. Sewage treatment upgrades help mitigate this |
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What are the direct & indirect impacts of fishing? |
Direct - overfishing, bycatch from gill netting catches turtles, sawfish, sawfish now extinct in southern US, shark finning, 47% fish stocks fully exploited, poorly managed long lines catch birds |
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What are the different fishing techniques? |
- Trawling - dragging across ocean floor, can wipe bottom clear |
