LECTURE 6 Flashcards
What is Reid’s paradox?
Reid’s paradox looked at oak maturity age and dispersal rates
Explain what happened at the end of the last ice age in the northern hemisphere.
North America and Europe Ecosystems
- ice sheets retreated hundreds of km in northern hemisphere
- species ranges expanded northward, following retreat of ice
- constant shifting of species associations recorded as species advance
Explain what happened at the end of the last ice age in the southern hemisphere.
Southern Temperate Ecosystems
- v little land at high latitudes in south, instead of ice sheets
- expansive montane glaciers that shrunk/retreated upslope
- species expanded out of microclimate refugee (local expansions)
- dominant vegetation showed rapid shifts in response to climate change
What is the Younger Dryas?
The Younger Dryas is a rapid cold snap at the start of the Holocene
A return to cold conditions (esp in the northern hemisphere)
Duration of 1000 years, then conditions reversed
What triggered the Younger Dryas?
Global warming > ice melting (Greenland, North America)
Water built up in Great Lakes region for years (ice dam) released all that once down St. Laurence and into norther Atlantic ocean
Freshwater mixed w sea water to shut down Gulf Stream
No heat transported north (return to colder climate)
Describe the biological changes during the Younger Dryas.
Spruce disappeared in North America
Vast majority of plants survived this cold period
Species may be able to tolerate relatively short, extreme climate changes
If cold snap lasted longer, would they have gone extinct?
What are the four major drivers of marine responses to climate change?
TSAC
Temperature
Sea level
Acidification
Circulation
What is the most important factor that determines the distribution of marine organisms?
Temperature!
What are benthic communities? Why are they important?
Benthic communities are refuges for cold water species during times of warming.
Benthic communities help to recolonize shallow waters in times of cooling.
In the Pleistocene, describe the direction of range shifts with respect to warming and cooling.
Poleward range shifts with warming; equatorial shifts with cooling.
What are foraminifera? What is its significance?
Foraminifera are protista. They are microscopic organisms from the open ocean.
They are important because they are a proxy for sea temperatures.
Describe what a Foram test is.
Looking at the ratio of oxygen-18 to oxygen-16; indicates temperature regime under which shells were formed
What is the cool tropics paradox?
Foram tests indicated that tropical oceans were cooler than predicted during the interglacial periods
Until 2001, it was believed that tropical oceans warmed less than high-latitude oceans
Resolved when Pearson et al showed this was artifact of partial dissolving of foram tests in tropical waters
Better preserved foram tests showed that tropical ocean warming was in line with higher latitudes
*Using these foram test, it indicated that the oceans were cooler in the tropics than the high latitude oceans. But that was not the case. They were in fact warmer.
T or F: Sea levels are lower in warmer temperatures.
False - sea levels are higher in warmer temperatures.
This is because water expands as it warms. And land ice melts and increases sea level.
The melting of which two locations affected the sea level?
Melting of Antarctica and Greenland caused an increase in sea level
Coastal lowlands were flooded because of this
T or F: Melting of sea ice causes an increase in sea levels and has no impact on food webs.
Melting of sea ice does not raise sea levels (ice just displaces the water)
It does impact food webs
With respect to sea level changes in Eastern North America, foraminifera communities changed repeatedly during ______ and _____.
Foraminifera communities changed repeatedly during Eocene and Pleistocene
Species disappeared and others appeared
Species composition varied greatly, even when sea levels similar (substitutions from species pool)
With respect to sea level changes in Pacific Islands, describe the conditions with respect to inner reef and outer reef species.
When sea levels were too low, inner reef specialists extirpated.
When the habitat resubmverged, inner reefs recolonized.
Outer reef species persisted regardless of sea level.
Name two ways in which oceans can influence climate and biodiversity.
- Changes in thermohaline circulation
2. Changes in teleconnections
What happens in oceans when there are changes to thermohaline circulation?
Nutrients accumulate in deep waters and rise to surface through upwellings
Deep water form as heavy, cold, saline waters sink (bringing carbon dioxide and oxygen with them)
Shutdown of circulation = deep waters are oxygen-deprived
What happens in oceans when there are changes to global teleconnections?
Marine systems respond particularly rapidly (extirpations and range shifts)
i.e. Pacific herring, Pacific Salmon, Atlantic cod, sardines, anchovies
What is evidence of major ocean chemistry changes?
Major ocean chemistry changes recorded in shells/skeletons of marine organism fossils
What are two important aspects when looking at the effects of ocean chemistry?
Carbon dioxide and pH > ability to form calcium carbonate structures
What are the types of calcium-carbonate secreting organisms?
- Calcite-secreting organisms (bivalves, clams, Rugose and Tabulate corals)
- Argonite-secreating organisms (Scleractinian corals, pteropods)
Of the two types of calcium-carbonate secreting organisms, calcite-secreting or argonite-secreting, which is an important food source to fish like salmon, mackerel, and cod?
Aragonite-Secreting organisms are an important food source for salmon, mackerel and cod
T or F: Coral reef distributions are a very reliable indicator of past climate.
False - coral distributions are not a reliable indicator of past climate.
Which is a better indicator of past climate conditions: coral reef distribution or coral growth rates?
Coral growth rates are used to infer past climate
There is a strong correlation bt coral growth rates and global mean temperatures
How quickly these corals grow are a good indicator NOT presence/absence
Increases in ______ and ____ reduce photosynthetic productivity of zooxanthellae.
Increase in salinity and turbidity reduce photosynthetic productivity of zooxanthellae.
What is turbidity?
Turbidity refers to how much debris is floating in the water.
How does an increase in turbidity affect the photosynthetic productivity of zooxanthellae?
If there is more debris in the water, less light can get through
How does a storm increase turbidity?
Storms can increase turbidity by washing land into the water
They can also bring up benthic water
Compare and contrast how salinity and turbidity change.
Salinity changes on a regional and local scale
Turbidity changes on a generally local scale
What are reef gaps?
Where we don’t know what was going on; there were no reefs in fossil records
True or False: Freshwater systems cover more of Earth’s surface than oceans.
False - Oceans cover most of Earth’s surface while FW systems cover less than 0.1% of Earth’s surface.
True or false: Extinctions rates in FW are higher than on land.
True - Extinction rates in freshwater are 3 to 4 x higher than on land.
FW systems exist in balance between ______ and _____.
FW systems exist in balance between precipitation and evaporation.
Fossil records are from _______. Why not other FW bodies?
Fossil records are from lakes.
Rivers and streams lack sedimentation and fast waters can destroy fossil records.
T or F: Microorganisms preserve much better than larger organisms.
True. Microorganisms preserve much better than larger organisms.
What are laggerstatten?
Laggerstattten are large deposits of macrofossils.
What can we learn from sediments?
Sediments are indicative of biogeochemical and biological changes
Sediments are also informative about surrounding terrestrial and marine ecosystems
What are varves?
Varves are annual layers created by biological or biogeochemical processes (lake turnover) that provide a clock for climate change
