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Briefly describe three major types of coral reefs and discuss how each of these are formed.
The three types of reef are fringing, barrier and atoll with all reefs starting as fringing. Fringing are the most simple reef forms, growing on the edge of the land and growing outward. Consists of a reef flat (inner) and a reef slope (outer). A barrier reef is formed as coastal land is flooded by rising sea levels. Grow as fringing reef on former coastal hills and reefs, and are much larger than fringing reefs. Atolls are fringing reefs subsiding around volcanic islands
List the advantages and disadvantages of synchronised mass spawning on coral reefs
Describe Langmuir circulation and its causes
Langmuir circulation is a large-scale feature of the open ocean. Weak to moderate winds blowing persistently across the sea establish long, parallel, rotating cylinders of water, with adjacent cylinders rotating in opposite directions (Figure 1 at right). Langmuir circulation therefore comprises alternate streaks of downwelling and upwelling which may extend for tens of kilometres and be separated by tens of metres. Buoyant particles aggregate in the downwellings and sinking particles in the upwellings. Langmuir circulations generally require surface winds of at least 8 m.s Langmuir circulation is responsible for fine-scale and large-scale patchiness of plankton.-1 in order to form.
Why is knowledge of temporal and spatial scales important in marine ecology?
One example of the importance of the concepts of space and time can be seen in the responses of algae to environmental fluctuations. Clearly we must combine the correct time-scale and spatial scale in order to be able to observe the effects of the environment on photosynthesis, growth or seasonal changes in population size and structure.
Define the term dispersal. Precisely identify a marine species, evaluate the intrinsic dispersal potential of that species, and explain the basis of your evaluation using precise information about the species.
Describe three structural adaptations that seagrasses have made to the marine habitat
- • Thin cuticles, no stomata
- • Leaf sheaths protect from salt
- • Fibres for strength, flexibility
- • Arenchyma and spaces- tissues to conduct air through plant (especially roots)
- • Rhizome system to anchor in soft sediment
- • Waterproof pollen
List three major roles algae play in coral reef ecosystems and give a named example of a typical algae for each role.
- Nitrogen fixers – blue green algae
- Reef formers-Porolithon
- Sediment formers- Halimeda
Describe three major food source categories for deep-sea animals living on the seabed
- Suspension and deposit feeders
- • Different protists produce different types of detritus, producing different muds
• Seagrass, Sargassum, wood•
- Fed on directly by urchins, molluscs
- • Bacteria in guts decompose cellulose
- • Fix nitrogen to supplement nutrient requirement
- Faecel pallets
- • Important source of nutrients
- • Large variety in size, shape, composition
- • Physical characteristics determine sinking rate and intactness
- • More biodegradation by gut flora contained within pellets than external bacteriaAnimal carcasses
- • Bodies of vertebrates (fish, mammals) and large invertebrates (squid)
- • Carcasses may provide 11% of community food requirements
- • Fed on by many organisms
Identify the main geomorphological differences between drowned-river valley, inter-barrier and basin estuaries
Drowned river valley
• Incised bedrock and adjacent coastal plain
- • V shaped in cross-section
- • Perpendicular to coast
- • Often no more than 20m deep
- • E.g) Swan-canning estuary
• Often no more than 2m deep
- • Parallel to coast
- • Elongate bodies with large surface area
- • Entrance channels often narrow
- • E.g) Harvey Estuary
• Usually no more than 2m deep
- • Entrance channels often narrow
- • Round bodies with large surface area
- • E.g) Peel inlet
Indentify the main life history categories of fish that are commonly found in the estuaries of southwestern Australia and how they relative abundance of these categories varies with type of estuary?
- Estuarine-dependent (Nursery Area):
- for numerous marine fish species
- Such species typically enter estuaries from marine waters as larvae or juveniles, and often in large numbers. They remain for a period in the estuary, exploiting the rich food reserves and shelter it provides, before eventually migrating back to Sea where they mature and spawn. Near shore marine waters also provide a similar nursery function for various marine species, and thus their juveniles are not necessarily dependent on estuaries for the completion of this phase of their life cycle. Consequently, marine species that often, but not exclusively, use estuaries as a nursery area were termed ‘marine estuarine-opportunists’.
- Yelloweye Mullet (Aldrichetta forsteri),
- Sea Mullet (Mugil cephalus),
- Eastern Striped Grunter or Trumpeter (Pelates sexlineatus),
- King George Whiting (Sillaginodes punctata), Tarwhine or Silver Bream (Rhabdosargus sarba)
- and Weeping Toadfish or Blowfish (Torquigener pleurogramma).
Marine species are found usually only in the lower reaches of estuaries and in low numbers
- Old Wife (Enoplus armata),
- Blue Sprat (Spratelloides robustus),
- Southern School Whiting (Sillago bassensis) and Rough Leatherjacket (Scobinichthys granulatus)
Complete their entire life cycles in estuaries and have thus been categorised as ‘estuarine’. Some of these are restricted entirely to these environments in south-western Australia and are thus termed ‘solely estuarine’
- Black Bream (Acanthopagrus butcheri), Yellowtail Grunter (Amniataba caudavittata),
- Bluespot goby (Pseudogobius olorum)
- and Western Hardyhead (Leptatherina wallacei).
Estuarine and Marine
The estuarine category are also represented by separate populations in coastal marine waters, and,in some cases, have been shown to be genetically distinct from their counterparts in estuaries.
- Estuary Cobbler (Cnidoglanis macrocephalus),
- Southern Bluespotted Flathead (Platycephalus speculator)
- Western Gobbleguts (Apogon rueppellii)
Name the marine biogeographical region that has the highest amount of biodiversity. State the geographical boundaries of this region. Outline one of the proposed explanations for the high level of biodivierstiy in the region.
- Indo- west pacific region has the highest amount of biodiversity – due to tropical weather. It extends from the eastern seaboard of Africa through south-eastern Asia, including northern Australia, to theeastern edge of Polynesia (Hawaii and Easter Island).The reason why there is such a high biodiversity is because;
- 1. climatic stability (low latitude and hence climatic fluctuations are relatively reduced and hence relatively low rates of extinction)
- 2. huge extent ~6,570,000 km2 (more space, more diversity)
- 3. close proximity to landmasses and consequent high productivity (more food, more diversity)
- 4. high rates of speciation resulting from sea-level changes in a geomorphologically complex area
- 5. area of overlap - accumulation of species from three separate sources
Explain how the nature of benthic substrates can influence the settlement of planktonic larvae onto these substrates
Outline the main details of a plausible marine example of each of: (i) allopatric speciation by subdivision; (ii) allopactric speciation by peripheral isolation; and (iii) a species flock.
Allopatric speciation by subdivision
• Large continuous population
- • A physical barrier more or less equally sub-divides the population
- • Immigration ceases: Large sub-populations on either side of barrier evolve independently and gradually diverge.
- • Secondary contact without interbreeding= speciation.
- • E.g) Very large number and broad range of closely related species pairs in the Western Atlantic and Eastern Pacific provide one of the most clear cut examples. (opposite sides of South America).
Allopatric speciation by peripheral isolation
• Large ancertral population
- • Small number of inidividuals colonise on unusual habitat
- • Isolated from parental population
- • Isolate evolves independently and diverges relatively rapidly
- • Secondary contact without interbreeding=speciation
- • E.g) Palau lake populations of the golden jellyfish provide a likely example of allopatric speciation by peripheral isolation
- • Lakes formed by marine inundation during Holocene marine transgression
• Endermic monophyletic assemblages that arose rapidly in a small geographic area.
- • E.g) Explosive radiation of Cape Verde Conus, a marine species flock.
How have mangroves adapted to survive in wet, muddy soils?
- Nutritive roots generally found in upper layers of soil where there is some oxygen.
- All mangroves species have additional roots or root adaptions to facilitate transfer of gases into or out of plants, arching stilt-like, air filled roots that arise from lower.
- Eg Avicennia- pneumatophoresXylocarpus- thickened conical structures on rootsBrugiera- knee like pneumatophoresRhizphora- no pneumatophores, but long arching stilt-like, air filled roots that arise from lower part of trunk