plant and animal interactions

Nota:

• competition is the result of limmiting factors the main for algae is space for light attenuation and food for many other species this is more important in low stress environments 

1. algae barnacles and mussels
   1. algae removal

      Nota:

      • a redution in dominent brown fucoids cover allows settlement of baranacles, this normally happens in april when there is spawning sue to a disturbance 
      • barnacles have the ability to remove holdfasts of the shore meaning they start to compete with the algae leading to a sucessful dominance 
   2. barancle removal

      Nota:

      • mussels then start to grown on the barancles and the algae due to more hard substrate 
      • they can then outcompete them by smouthering the competition 
   3. mussel removal

      Nota:

      • mussels can be dislogded by a disturbance such as wave action or grazing which means algae can re-establish and the cycle can continue 
      1. as well as this cycle and opetunist species Postelsia palmaeformis

         Nota:

         • this plant doesnt normally grow as it is not that great as a competator but if it is established in a free space it will respawn in that space immediatley after removal by a disturbance 

1. mangrove systems

   Nota:

   • these are the main source of primary production within the tropics however the leafs are palatable to many organisms due to too much cellose content to break down lee 1998
   1. Robertson 1986

      Nota:

      • sesarmid crabs break down 28% of the leaf litter by taking them into its burrow where it can be exturnally digested by microrobes = important for the nirtogen and carbon cycle 
   2. many of the leafs are carried of to corals and seagrasses where they can be broken down taking the nutrients else where
   3. terrestrial grazers can break down the leafs however this enters the terrestrial environent
      1. reptials and amphibians are adapted to high slaine content
      2. birds

         Nota:

         • show high variability in niches due to feeding see noske 1995 for the different feeders 
   4. Marine fauna
      1. mollusca

         Nota:

         • these feed on the algae growing onthe mangrove trees, they are sepearted by the algae they concume and where it isfound on the trees
         • adult molluscs can feed directly on the leafs and this has a direct impact on its distribution - wont fight with juveniles for food 
         • the chemical content dictates the amount of gastropods present and the amount of leaves dictates the size and its distribution 
         • leafs are found by chemicals being released into the air and water by breaking down of the leaf by one gastropod = makes the process quicker 
      2. crustaceans

         Nota:

         • ecosystem engineers by building birrows and bioturbating the sediment present recycling nutrients. 
         • two main families 
   5. Gastropod and grapsid interaction

      Nota:

      • they both compete for the same food resource of the eafs - however they have differentfeeding stratgergies to try ad overcome each other ie too many gastropods on one leaf means a crab cant take it 

1. algae are primary produces and therefore dictate the whole food chain
   1. herbivores can effect this and the system greatly
      1. can lead to a competitive balance
         1. therefore it is shown that intermediate grazinf pressure is the ideal for themaximum productivity and biodiversity
      2. impacts
         1. types

            Nota:

            • fish - large foraging ranges but occur in low densities 
            • urchins intermidaites in both catogories 
            • mesograzers - only found on the shore but occur in very high densities 
         2. mesoherbivores

            Nota:

            • high algal diversity = grazers show a preference on which they graze on this could be link to different nutrient values 
   2. Algal defences
      1. strutural and mophological

         Nota:

         • certain growth forms are developed so grazers can minipulate them
         • tougher and less palatable plant tissue 
         • calcification 
         • heteromorphical life cycle 
      2. chemical

         Nota:

         • constitutive or induced 

Nota:

• many grazers use algae as habitats   - 
• factors affecting this  - availiability  - complexity  - suitability as a food source 
• there has to best balance between all three of these however this is not normally the case 

1. Marsham 2007