L6 - Tropical Coasts Flashcards
What are continental margins of ocean basins?
The boundaries between continental and oceanic crust
What is the oceanic crust?
8% of the ocean’s surface area, but biologically richest parts of the ocean
What is the tropical seascape?
It is interconnected, Land, mangroves, seagrasses, coral reef, offshore waters
What are coral reefs?
Among the most biologically diverse ecosystems - biodiversity hotspots. They provide a habitat structure and facilitate other species by providing a range of niches.
What do coral reefs do?
They are ecosystem engineers. They support important subsistence and commercial fisheries. They account for ~5% of the world marine fisheries landings. 22million artisanal fishers worldwide - 6 million of those are on coral reefs.
What do coral reefs habitat structure provide?
Tourism/cultural services, biodiversity, shoreline maintenance, coastal protection, fisheries
Where are coral reefs distributed?
Within 30 degrees latitude of the equator, bounded by minimum average water temperature ~ 20 degrees.
What is the coral triangle?
Centre of diversity. ~76% of the worlds coral species, 37% of the worlds coral reef fish species. 6 out of 7 marine turtle species
Where are there no coral species in common between?
The atlantic and indo-pacific ocean
What are corals?
Coral is a general term for several different groups of cnidarians. Not all corals species build reefs.
What are the two types of corals?
Hermatypic and Ahermatypic
What are Hermatypic corals?
Reef building, mostly in the tropical regions.
What are Ahermatypic corals?
Non reef-building distributed world wide.
Which type of corals are strongly influenced by their physical environment?
Hermatypic
What ate scleractinian corals?
Main group of hermatypic corals, coral reefs are colonies of various hermatypic corals. Each coral colony is comprised of tiny animals called polyps. The polyps produce skeletons made of calcium carbonate.
What are some characteristics of hermatypic coral reefs?
The corals have a larval stage as a planula - zooplankton, spawning can be synchronised, rarely grow deeper than ~ 50m. Most tropical waters where coral reefs are found are usually nutrient-poor. Little in the way of phytoplankton.
Hermatypic coral reefs - What do polyps contain?
Polyps contain symbiotic algae (zooxanthellae)
What are some common hermatypic corals?
Acropora, Tubinaria, Porites, Fungia
What are the different coral reef zones?
Shore zone, back reef zone, reef flat zone, fore reef zone, drop-off zone.
What are the different types of reef?
Fringing reef, patch reef, barrier reef, atoll
What is a fringing reef?
Along the coast, most common, susceptible to terrestrial influences.
What is a Barrier reef?
Surround many tropical islands, separated from land by lagoons, may develop from fringing reefs after sea level rise.
What is a Atoll reef?
Found far from land. Rising from depths of 1000s metres. Ring of reefs, islands and sand cays.
What are some reef algae?
Many species of algae are also fundamental to coral reef structure and function. Macroalgae, coralline algae, turf algae.
What is macroalgae?
Can be calcified, compete with coral for space and light, shade out coral, mechanical and chemical damage, prevent coral larvae settlement.
What is coralline algae?
Slow growing crustose coralline algae, secondary carbonate producer, cements and stabilises.
What is Turf algae?
Fast growing, epilithic (grow on rock surface). Cyanobacteria and meiofauna within. Can be drowned by sediment, with zooxanthellae, one of the most important primary producers on reefs.
What phase shifts are there on coral reefs?
From coral dominated to algae dominated. This can be triggered by e.g. coral bleaching, cyclones/hurricanes, crown of thorns starfish, eutrophication. Herbivorous fish are important in regulating space competition between corals and algae.
What types of herbivorous fish are there?
Browsers, grazers/croppers
What are Browsers?
Key for reef resilience, eat large, fleshy macroalgae, e.g. unicornfish, batfishes, rabbitfish.
What are Grazers/croppers?
Intensely graze epithilic algal turfs, can limit the establishment and growth of macroalgae, e.g. rabbitfishes, surgeonfishes.
What are parrotfishes?
Scrapers/excavators - scrape coral surface and erode reefs, exposing new substrate for larval settlement. Maintain low algal cover, remove live and dead coral, remove and transport sediment.
What are mangroves?
Dicotyledonous woody shrubs, 54 true species exclusively in mangrove habitats, confined to tropics, form dense forests - monospecific patches.
What do mangroves do?
Can dominate intertidal muddy shores, need soft sediments to get established, stabilise soil, create structurally complex habitats, an example of convergent evolution.
What is a mangroves environment?
Periodically inundated by the tides, soils are usually permanently waterlogged and anoxic. Soils are soft and fairly unstable. Fluctuating salinity -> evaporation leads to hypersalinity.
What are mangroves adaptations to waterlogged soils?
Buttress roots (pelliciera sp.), Knee roots (bruguiera sp.), prop roots (rhizophora sp.), pencil roots (avincennia or sonneratia)
What % can aerial roots account for of above ground biomass?
24%
What are some examples of mangroves?
Rhizophora mangrove (red mangrove), avicennia germinans (black mangrove), laguncularia racemosa (white mangrove).
How are mangroves adapted to hypersalinity?
Exclusion of salts at the roots (e.g. red mangrove), a physical process. Intracellular partitioning of salt (e.g. black and white mangroves) a chemical process, na+ and cl- in vacuoles, salt glands on leaves.
What is productivity and complexity in mangroves?
Mud surface a site for photosynthetic algae, below, bacteria and fungi decompose organic matter. Burrows of deposit and filter feeders, detritivores, herbivores, and predators aerate the mud, trees provide a substrate which other organisms colonise - epibionts. Primary production, nutrient cycling and structural complexity.
What are mangroves role as nursery habitats?
Higher species richness, shelter, food, fish : ontogenetic migration.
What do mangroves show?
Zonation
What are human impacts on coral reefs?
Climate change, human development, eutrophication, overfishing, invasive species
What are impacts on mangroves?
Storms - hurricanes and typhoons, tsunamis. Human impacts - deforestation, agriculture, aquaculture, urbanisation, pollution.
