Factors Limiting Distribution: Species interactions and the physical environment

Question 1

What controls species distributions?

Answer 1

Biotic and abiotic factors

Question 2

What organisms are found in the littoral fringe?

Answer 2

Lichens
Cyanobacteria
Periwinkles

Question 3

What organisms are found in the eulittoral zone?

Answer 3

Barnacles
Mussels
Fucoid seaweeds

Question 4

What organisms are found in the sublittoral fringe?

Answer 4

Laminarian seaweeds

Question 5

Describe seaweed and barnacle zonation

Answer 5

-Barnacles dominate the eulittoral zone on moderately exposed to exposed to shores
-Fucoid seaweeds dominate eulittoral on sheltered shores
-Kelps dominate the sublittoral
-Within each group, zonation in species composition also evident

Question 6

What was the conclusions of experiments conducted by Schonbeck and Norton?

Answer 6

Upper limits of fucoid seaweeds determined by effects of desiccation, lower limits determined by interspecific competition

Question 7

Describe the Torrey Canyon oil tanker spill

Answer 7

-Torrey Canyon oil tanker spill, ship sank 18th March 1967 carrying 119,000 tons of oil
-14,000 tons of oil washed up on the coast of Cornwall
-10,000 tons of dispersants (solvents) were released
-Clean up operation killed intertidal organisms
-Recolonisation occurred over a period of 10 years and was studied by ecologists

Question 8

What was the reconolisation pattern from 1967 to 1977 after the oil spill?

Answer 8

-Green algae was first to return, thrived in absence of predators
-Green algae was replaced by fucoid seaweeds, which eliminated any barnacles and extended past their normal limits, even on exposed shores
-As limpet populations recovered, fucoid seaweeds lost their dominance
-As fucus cover reduced, barnacle populations recovered and limpet populations decreased

Question 9

What does recolonisation patterns show the importance of?

Answer 9

Show the importance of grazers for restricting the upper limit of kelp and limiting growth of fucoid algae

Question 10

What regions have major developed coral reefs?

Answer 10

-Indo pacific region
-Red sea
-Greater Caribbean Region of the Western Atlantic

Question 11

What regions have minor, smaller fragmented areas of corals?

Answer 11

-Eastern Pacific, Off Western Australia
-Southern Japan in the Pacific ocean
-Tropical eastern Atlantic: East coast of southern Brazil, Island of Bermuda in Western Atlantic

Question 12

What order do reef building corals belong to?

Answer 12

Scleractinia (stony coral)

Question 13

What do all reef-building corals contain in their tissues?

Answer 13

Zooxanthellae

Question 14

What density do zooxanthellae live at in coral tissue?

Answer 14

1 million cells in cm-1 of coral tissue

Question 15

What do zooxanthellae do?

Answer 15

-Give coral their colour
-These photosynthetic dinoflagellates live in symbiosis within the coral

Question 16

Describe coral-algae symbiosis

Answer 16

-Coral provides protection, nutrients like CO2, nitrogenous and phosphate wastes
-Coral get O2 and food from photosynthesizing zooxanthellae
-Zooxanthellae produce 10 - 100 times more carbon then they require
-Excess carbon sustains reef building corals in waters that are very unproductive

Question 17

What physical factors limit the distribution of coral reefs?

Answer 17

Zooxanthellae have narrow requirements
-Need temperatures of 18 - 30 degrees
-Need solid substrate to grow on
-Need access to light- shallow clear waters
-Narrow range of salinity tolerance

Question 18

What impacts does range of tolerance have on organisms?

Answer 18

-Organisms have adapted o specific conditions
-Abundance is highest within the optimum range of these conditions
-In zones of physiological stress, survival and reproduction are possible but not optimal
-In zones of intolerance the organism is absent
-Organisms with a wide range of tolerance are generally more widely distributed then those with a narrow range of tolerance

Question 19

What are the two main abiotic factors that limit species?

Answer 19

-Temperature
-Moisture

Question 20

What do abiotic effect?

Answer 20

-Can influence any stage of the life cycle
-Survival
-Reproduction
-Development
-Effects may be indirect, like species may become suspectable to disease at specific temperatures

Question 21

Describe coral bleaching

Answer 21

-Coral algae tolerant to narrow ranges of light, salinity and temperatures
-Changes in environmental conditions can kill the algae causing the coral to expel them resulting coral bleaching
-Very difficult for coral to survive with the algae
-Algae may recolonize when conditions improve, but coral growth and reproduction may be impaired and more susceptible to disease

Question 22

What factors trigger coral bleaching?

Answer 22

-Increases or decreases in water temperature (A change of 1 degrees for 4 weeks can trigger bleaching events)
-Reduced pH (acidification)
-Low salinity (increased inputs of freshwater)
-Pollution
-Increased solar radiation
-Non-biodegradable chemicals in some sunscreens

Question 23

What other pressures effect coral reefs?

Answer 23

-Crown of Thorns Starfish is a voracious predator of corals, increased populations linked to overfishing
-Overfishing of grazers that prevent increased algae growth
-Destructive fishing methods damage reef structures
-Ocean acidification leads to weakening of CaCO3 skeleton of reef building corals

Question 24

What must temperatures be reduced to save >10% of world’s corals?

Answer 24

Temperature rises of no more than 1.5 degrees

Question 25

Can corals adapt to thermal stress?

Answer 25

-Dinoflagellate algae associated with reef building corals belong to the genus Symbiodinium which includes many different species
-More corals contain a dominate type, but others may be present at low levels
-Evidence suggests that some types of zooxanthellae may be more resistant to thermal stress than other

Question 26

Describe a coral transplant experiment (Berkelmans et al 2006)

Answer 26

-The common but bleach sensitive coral Acropora millepora was transplanted from two cool offshore reefs to a warmer inshore reef (0.9-1.3 C temp difference) on the Great Barrier Reef (control transplantation also conducted).
-The type of zooxanthellae present in the corals was determined using genetic techniques before and after transplantation.
-The study found evidence that in transplanted corals which suffered bleaching and then recovered, the dominant zooxanthella had switiched from Type C (heat sensitive) to Type D (heat tolerant)

Question 27

What is another potential species of zooxanthellae that could be tolerant to heat stress?

Answer 27

-Porites divaricata, but symbiosis was not stable

Question 28

Describe Staghorn coral (Acropora cervicornis)

Answer 28

-This coral species could become increasing rare in the next 20 years due to rising sea temperatures and ocean acidification

Question 29

Describe mountainous star coral (Orbicella faveolata)

Answer 29

This coral species possesses an adaptation that allows it to survive under high temperatures and acidity conditions

Question 30

What traits make organisms more susceptible to climate change?

Answer 30

-Requirements for specialized habitat
-Specific environmental tolerances
-Dependence on environmental cues
-Dependence on interactions
-Ability to disperse

Question 31

What factors influence species distributions?

Answer 31

-Dispersal : Area inaccessible/ insufficient time for dispersal
-Behaviour: Habitat selection
-Other species: predation, competition
-Physical and chemical factors: Temperature, salinity, oxygen, soil structure

Question 32

What are the general principles?

Answer 32

-Species distributions are influenced by biotic interactions and the physical environment
-Often these factors interact to shape species composition in a community
examples include:
-Species zonation in rocky shore habitats
-Distribution of reef building corals determined by zooxanthellae