Lecture 19- Community change: Range shifts Flashcards
What are the two types of expansion/contraction of a species’ range?
•Expansion and/or contraction of a species range 1. Range shift=No direct human mediation= new area adjacent to old 2. Introduction = new area separated from old -directly mediated by humans
Were the Mediterranean and the Red Sea ever connected before the construction of the Suez Canal?
-yes, in the Pliocene, 2 million years ago
When was the Suez Canal opened?
1869
What is the functional significance of the Suez Canal?
-Removal of topographic barrier between two biogeographic provinces so can mix
Is the Suez a range shift of introduction?
- there is a human component but really it is mostly range shift as it is not a human mediated transport of organisms
How long, wide and deep is the Suez Canal?
-Length 193 km (164 km in 1869) -Max depth 24 m (8 m in 1869) –Width 123 - 313 m (65 - 98 m in 1869)
What are the intermediate water bodies on the Suez Canal and their salinity?
- SE Mediterranean: Summer SST up to 29oC Salinity 39.5 ppt
- Lake Timsah - brackish
- Bitter Lakes - hypersaline early 1870s - up to 70 ppt 1970s - 43 to 48 ppt
- Gulf of Suez Salinity up to 45 ppt -there is a difference in salinity in between the red sea and the mediterranean -big differences in salinity -brackish= less salty
What is the current direction in between the Red Sea and the Mediterranean?
-Currents to north except July-Oct
What is the environment of the Med. vs Red Sea?
1.SE Mediterranean (Levantine Sea) a) sub-tropical Atlantic-Mediterranean province b) relatively depauperate biota (e.g. < 50% benthic spp of whole Med) c) oligotrophic 2.Red Sea / Gulf of Suez a) tropical Indo-Pacific province b) abundant & diverse biota (lot of endemism, derived from the indo-pacific province) c) very oligotrophic
What is the biota derived from in the Med and Red Sea?
1.Med:sub-tropical Atlantic-Mediterranean province 2.Red:tropical Indo-Pacific province
How is the cross canal migration called?
-Lessepsian migration = migration from Red Sea to Mediterranean via Suez Canal –over 300 species
How many species migrate in the direction from Med to Red Sea? Why?
-Few spp. in reverse direction –all confirmed migrants are fish = only active swimmers as the current goes north most of the time so have to swim against it to get to the Red sea
What are some examples of the Lessepsian migrants?
1:Penaeid prawns –bulk of catches along Egyptian coasts 2.Commercial fish species –␣ e.g. lizardfish Saurida undosquamis 3.Jellyfish Rhopilema nomadica –first seen 1980s –now huge swarms June/July – impacts fishing, tourism ————————————– -almost 1/2 of fished species in SE Med. is from the species migrated from the Red Sea -this migration is a mixed blessing= good for fishing since more species but jellyfish are bad!
Is the transfer of organisms from Red to Med via shipping or aquaculture?
-only few tranported on hulls of ships= -Only 20% of Erythrean fish •Only 13% of Erythrean decapods •Only 12% of Erythrean molluscs –most are making their way by natural dispersal
What is the black urchin?
-Centrostephanus rodgersii •NSW species •Creates barrens on coastal reefs •First isolated specimens in NE Tas in 1978 •Over last 40 years, moved polewards at ~160 km / decade (-urchin use to reach souther limit in NSW -now even in Tasmania -moving to the South 160km/decade= rapid shift)
What do urchins feed on?
urchin barrens= lot of rocks= they graze on the rocks and eat everything (especially algae)
Why have the black urchins been moving southwards?
-Increased southward penetration of Eastern Australian Current over last 60 years -Eastern Tasmanian waters now warmer, saltier & lower in nutrients and can support the larvae that need 12C at least
What are the characteristics of the urchin larvae?
- Long-lived (~ 100 days)
- Min 12oC for successful development
- Sustained larval transport from NSW, not just chance dispersal event(s)
- can stay in the water column at a certain level thanks to the wings
- need 12C= now with the Eastern Australian Current it is further south where these temperatures are reached so they can disperse further
- sustained flow of larvae towards Tasmania, genetic diversity the same in Tas as NSW
What does this graph show?
-Barren= the bare rock grazed by urchins -have good populations in th enorth but as move south the age of populations declines -amount of barren decreases towards the south -so the urchins do less well in the south but still can survive
What is the whole flow chart of Macrocystic decline and the reasons for it?
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What are the general projections of change due to global climate change in temperature and pH?
- projections of what the temp and pH will be like in 2070
- increase in temp= mainly in the southeast part of australia -decrease in pH, the blue and purple is the most dramatic drop =influence on calcifying organisms= moluscs, corals and calcarious algae= won’t be able to grow
- the temp and pH will make range shifts occur
