environmental gradients Flashcards
what are examples of environmental gradients?
• particle size
• salinity
• vertical: emersion/depth
• wave exposure
• latitude/temperature
• anthropogenic disturbance
what life is present on rocky shores?
epifauna and flora
what life is present on cobbles and shingles?
unstable and lifeless, no macrobiota
what life would be present in salt marshes, mangroves, seagrasses and sandy beaches?
infauna, epifauna and macrophytes
What adaptations would be present in plants in anoxic sediments?
Prop roots - enable gas exchange out of sediment using lenticels
Pneumatophores – roots that stick up out of surface and do gaseous exchange
MANGROVES IN MUDDY SHOREs
What are halophytes?
Plants adapted to growing in saline conditions, e.g. mangroves in muddy shores or terrestrial plants in salt marshes
What is true of mangroves in muddy shores?
Serves as coastal erosion protection
Sediment accretion
Infaunal communities present
What are infaunal communities?
Aquatic animals that live in the substrate of a body of water and which are especially common in soft sediments
What is true of sandy beaches?
(in terms of sediment)
- Physical substrate is shifting and unstable
- Substance disturbance by waves
What is true for fauna on sandy beaches?
- Burrow to avoid stresses and predation
- Fauna rely on imported food
- Low primary production
What is the intermediate disturbance hypothesis?
Predicts that the highest diversity will occur at levels of moderate disturbance.
What are Sousa’s (1979) notes on the intermediate disturbance hypothesis?
Size of boulders, mobility and their diversity – boulders with intermediate disturbance had highest number of species
What are Connell’s (1978) notes on the Intermediate disturbance hypothesis?
Low or high diversity is bell shaped from frequent and rare, large or small, etc.
What is true of rocky shores?
- Physical substrate is hard and stable
What is true of fauna on rocky shores?
- Organisms visible
- Living on top of substrate: epifauna, epifloral, not to be confused with epibiont
- Abundant and small – unusually large specimens on West Coast of USA
- Sessile or sedentary
What is a fully stratified salinity gradient?
Fresh water flows over seawater
What is a moderately stratified salinity gradient?
- Wind
- Tide mixing
- River water begins to mix
- Wedges formed
What is a vertically homogenous salinity gradient?
Zones gradually become saline
What is true of estuaries salinity regime?
Variable salinity regime
What is the flow of estuaries?
Fresh -> river, head, upper reaches, middle reaches, lower reaches, mouth -> marine
What is true of the biodiversity of estuaries?
- Few true estuarine species (complete whole life cycle)
- Many visitors (anadromous/catadromous)
What are some adaptations of estuarine species?
- Osmoconformers - Adapt to salinity of local environment as it changes
- Osmoregulators - internal processes to regulate own salinity of body, don’t take on local salinity regime
What is an example of the broader biogeographic impacts of freshwater input?
– Yangtze River Plume:
–– Genetic differences present for 3 rocky shore limpet species between the Yellow Sea and other 2 marginal seas (East China Sea and South China Sea)
–––– No difference for muddy shore species Atrina pectinate (salt marsh around estuary)
What does the vertical gradient represent?
Shallow subtotal to intertidal to terrestrial
