Lecture 18-Biogeography of Coasts Flashcards
What is biogeography?
• Science documenting geographic patterns of biodiversity -has largely focused on species diversity
What are the three historic phases of biogeography?
- descriptive (ecological) 2. narrative 3. analytical
What is the definition of a biogeographic province?
-coastal region characterised by a relatively distinct and homogenous flora and fauna, with only a small percentage of species common to adjacent regions, and usually differing in temperatures from adjacent provinces by more than 5°C
Describe the O’Hara and Poole study (example of a biogeographic study).
•Patterns in species composition, species richness and endemism •347 echinoderm spp. -392 decapod spp. -biogegraphy study of echinoderms and decapods in southern australia -looked at distribution in these two groups -divided the coast into cells and recorded if the organism was there or not(•57x 1° lat/long cells along coast) -shows you have geographic structure 5 biogeographic regions present in the southern coast -strong evidence for biogeographic regions along coast -Fauna related to sea surface temperature, latitude, longitude, break-up of Gondwana
What was the distribution of Meridiastra calcar and Uniophora granifera in the O’Hara and Poole study and what does it show?
• Meridiastra calcar(doesn’t give you much info for biogeography as it is widely distributed) – Albany, WA, to Qld & around Tas. –␣Rockpools, sheltered reefs – Mid-intertidal to 10 m •Uniophora granifera – Spencer Gulf, SA to Solitary Is, NSW, & around Tas. – Sheltered reef, silt, seagrass – 0 to 30 m(this one gives you information as it is not widely distributed)
What are the patterns driving biogeographic distrivution? (4)
- Plate tectonics 2. Ocean currents & sea temperature 3. Habitat availability 4.Ability of species to disperse
How did the breakup of Gondwana affect biogeography? (1. Plate tectonics)
- along south australia= get different species than east australia as the organisms could interact only for 30MY
- By 30 Ma, Australia completely separated from Antarctica
- huge timescale
What is unusual in Australia’s geography of the coast?
- huge amount of south-facing coastline unlike south africa and south america
What is the unusual current around Australia? (2. ocean currents and sea temperature)
•Unusual to have warm current flowing polewards on east side of ocean basin in southern hemisphere
- red= coastal Loewen current -tropical water goes around the corner to the south coast
- unusual
- so thanks to that trpical organisms get transferred that way
- go quite far south
What is the sea temperature gradient in the world? (2. ocean currents and sea temperature)
• Gradient from tropics to poles •Also varies spatially over smaller scales • Has fluctuated through geological time spatial variation over small scales= vary in temp -around victoria= upwelling so cold -latitude biodiversity gradient= more species richness of organisms= but not with algae!!! -in colder water= more diversity of algae than in warmer water
How does species richness change with temperature? (2. ocean currents and sea temperature)
In general, spp. richness increases with temp. – exceptions include benthic macroalgae • diversity & endemism v. high in southern Aust. -macroalgae are more diverse in cold waters
How long is the Australian coastline and how much of it is sandy beach and rocky shore? (3. Habitat availability)
- coastline approx. 36,000 km – approx. 50% sandy beaches – approx. 40% rocky shores -the remaining 10% are various (estuaries etc.) –more contemporary timescale -determines the biogeography, eg. barnacles= need rocks so won’t occur in sand -mangroves= cannot grow in rocky shore, must have estuaries as less exposed
What determines a species’ ability to disperse? (4. Ability of species to disperse)
=Many benthic species have planktonic stage in life history – gametes –spores or larvae =Potential for currents to aid dispersal -so presence of currents and if they have larvae and what type
What are the two types of larvae?
-Lecithotrophic larvae -Planktotrophic larvae (Not always larvae/spores => e.g. seaweeds= disperse via adult thalli)
What are the characteristics of Lecithotrophic larvae?
– non-feeding – [lecitho = egg yolk, trophic = feeding on] – rely on energy reserves – relatively large & few in number –short time in plankton (mins to hrs)
What are the characteristics of Planktotrophic larvae?
– [plankto ~ plankton] –obtain own food –relatively small & numerous –longer time in plankton
How does time come into dispersal?
•More time in water = more potential for dispersal –Quick-settling spores of Postelsia released in spray of rising tide (must settle in matter of hours) – King George whiting larvae drift for 3 - 5 months, the adults swim out and lay eggs, then larvae drift with the current back to Port Philip Bay
What is the dispersal of King George whiting like?
–cycles in catches match cycles in westerly wind strength,as more larvae transported then with the current –good settlement in PPB corresponds to warmer SST west of Cape Otway
Are the planktonic stages completely at mercy of currents?
-no -like in the example of Western rock lobster
What is the dispersal mechanism of the Western rock lobster?
– phyllosoma larvae [phyllo = leaf, soma = body] – migrate vertically to catch offshore currents –spend 9–11 months 400+ km in open ocean (Indian Ocean) –daily vertical migration 0–60 m –late-stage larvae between 60–140 m depth during day to catch east-flowing current -once they grow large enough drop to the current and go towards the coast
What are the cues for settlement? (4)
1.chemical •e.g. abalone & crustose red algae • barnacles & conspecifics 2. light intensity 3. surface texture 4.presence of biofilm
What does this picture show?
-older larvae are more desperate to settle
What are the two systems of larvae dispersal?
-larvae retained= closed system -larvae dispersed= open system
What determines the biogeography of coasts?
-Various processes acting at different temporal and spatial scales: 1.geological events & evolution 2.dispersal (life history + currents) 3. habitat (temperature & micro-habitat) =Combine to generate the patterns we observe in present-day species distributions.
What did research show in terms of number of biorovinces in Australia?
5 -one type of division, based on qualitative studies
What are the marine bioregions?
–IMCRA: Integrated Marine and Coastal Regionalisation of Australia
–24 provinces + 17 transitional bioregions based on geomorphology, oceanography & demersal fish
–also meso-scale bioregions nested within provincial bioregions
–Also exists at global level (Spalding et al. 2007) -finer scale is important for management
Why are marine bioregions important?
•”provide spatial frameworks . . . for many aspects of natural resource management” •”contribute to an improved understanding of the wide variety of marine environments” •important input to planning and management decisions”
