Factors Limiting Distribution: Species interactions and the physical environment Flashcards
What controls species distributions?
Biotic and abiotic factors
What organisms are found in the littoral fringe?
Lichens
Cyanobacteria
Periwinkles
What organisms are found in the eulittoral zone?
Barnacles
Mussels
Fucoid seaweeds
What organisms are found in the sublittoral fringe?
Laminarian seaweeds
Describe seaweed and barnacle zonation
-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
What was the conclusions of experiments conducted by Schonbeck and Norton?
Upper limits of fucoid seaweeds determined by effects of desiccation, lower limits determined by interspecific competition
Describe the Torrey Canyon oil tanker spill
-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
What was the reconolisation pattern from 1967 to 1977 after the oil spill?
-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
What does recolonisation patterns show the importance of?
Show the importance of grazers for restricting the upper limit of kelp and limiting growth of fucoid algae
What regions have major developed coral reefs?
-Indo pacific region
-Red sea
-Greater Caribbean Region of the Western Atlantic
What regions have minor, smaller fragmented areas of corals?
-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
What order do reef building corals belong to?
Scleractinia (stony coral)
What do all reef-building corals contain in their tissues?
Zooxanthellae
What density do zooxanthellae live at in coral tissue?
1 million cells in cm-1 of coral tissue
What do zooxanthellae do?
-Give coral their colour
-These photosynthetic dinoflagellates live in symbiosis within the coral
Describe coral-algae symbiosis
-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
What physical factors limit the distribution of coral reefs?
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
What impacts does range of tolerance have on organisms?
-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
What are the two main abiotic factors that limit species?
-Temperature
-Moisture
What do abiotic effect?
-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
Describe coral bleaching
-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
What factors trigger coral bleaching?
-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
What other pressures effect coral reefs?
-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
What must temperatures be reduced to save >10% of world’s corals?
Temperature rises of no more than 1.5 degrees
Can corals adapt to thermal stress?
-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
Describe a coral transplant experiment (Berkelmans et al 2006)
-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)
What is another potential species of zooxanthellae that could be tolerant to heat stress?
-Porites divaricata, but symbiosis was not stable
Describe Staghorn coral (Acropora cervicornis)
-This coral species could become increasing rare in the next 20 years due to rising sea temperatures and ocean acidification
Describe mountainous star coral (Orbicella faveolata)
This coral species possesses an adaptation that allows it to survive under high temperatures and acidity conditions
What traits make organisms more susceptible to climate change?
-Requirements for specialized habitat
-Specific environmental tolerances
-Dependence on environmental cues
-Dependence on interactions
-Ability to disperse
What factors influence species distributions?
-Dispersal : Area inaccessible/ insufficient time for dispersal
-Behaviour: Habitat selection
-Other species: predation, competition
-Physical and chemical factors: Temperature, salinity, oxygen, soil structure
What are the general principles?
-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
