Lecture 7- Intertidal zone I Flashcards Preview

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Flashcards in Lecture 7- Intertidal zone I Deck (20):

What is the definition of the intertidal zone?

-  shoreward  fringe  of  the  sea-­‐bed  between  the   highest  and  lowest  extent  of  the  tides. -Productive  areas  which  receive  rich  nutrient  supply terrestrial  nutrients  and  coastal  phytoplankton -Very  close  proximity  to  humans  ␣ which  means  they  are  well   studied  ecosystems  and  also  highly  exposed  to  human   impacts


What are some examples of intertidal zones?

 -mangrove  forests,  seagrass  beds,  mud  flats,  beaches,   rocky  coastline


What is typical of the intertidal zone?

-zonation is typical of intertidal zone, across a short gradient even just meters

-over just tens of meters completely different organisms= different species


What cause zonation in the intertidal zone?

1. Physiological  tolerance 2. Wave  shock 3. Larval  and  adult  preferences 4. Competition 5. Predation -Similar  patterns  of  species  vertical  ranges  combined  with  sharp   boundaries  suggests  zonation  is  caused  by  simple  factors


How does physiological tolerance and wave shock determine the zones in the intertidal zone?

-Species  found  higher  on  the  shoreline  are  generally  more  tolerant  of   dessication,  reduced  feeding  time,  reduced  access  to  oxygen  and  extreme   temperatures.  Organisms  lower  in  the  intertidal  are  more  resistant  to  wave   shock. example:because  of  their  ability  to  seal  themselves  inside  their  test,  barnacles  are   found  higher  in  the  intertidal  than  anemones


How does body size and the surface to volume ratio influence water loss?

-As  body  size  increases,  the  surface  area  relative  to  body   volume  decreases,  and  this  aids  in  reducing  water  loss.

-However,  a  decreased  surface  area  to  volume  ratio  comes   with  increased  size  which  is  a disadvantage  for  heat  loss

-Intertidal  organisms  trade  off  water  loss  and  heat  loss  in   their  body  sizes


How does shape influence water loss and hence zonation?

- Long  thin  organisms  lose  water  more  rapidly  than  spherical   organisms - E.g.  sea  anemones  contract  into  a  small  cylinder  at  low  tide   to  reduce  surface  area  and  water  loss


What are the adaptations to heat stress?

-Evaporative  cooling  and   circulation   of  body  fluids - Higher  intertidal  animals  better   adapted  to  heat  stress  than  lower   intertidal  species - e.g.  species  of  the  intertidal   gastropod  Nerita that  reside  higher   in  the  intertidal  zone  retain  cellular   function  at  higher  temperatures


How are feeding mechanism affected as an adaptation to heat stress?

-feeding capabilities differ for upper intertidal and  lower  intertidal  organisms -e.g.  movement  of  the  feeding  appendages   (cirri)  in  a  lower  intertidal  and   an  upper   intertidal  dwelling  barnacle   differs  in   response  to  temperature  i.e.  upper  intertidal   barnacle  increases  its  feeding  rate  at  higher   temperatures  (up   to  an   upper  thermal  limit)


How do periwrinkles adapt to heat stress?

close  their   operculum(the bottom opening)  to  remain  moist   during  low  tide  when  exposed   to  air


How do limpets adapt to heat stress?

-make  the  edge  of  their   shell  fit  the  exact  configuration   of  the  rock  where  they  live,   keeping  water  inside.  These   spots  on  the  rock  are  known  as home scar


What is the example of heat stress adaptation where the colour of an organism changes?

-Colour  may  vary  with  latitude -e.g.  proportion  of  brown  and black  colour morphs  of  the   blue  mussel  Mytilus  edulis Varies  with  latitiude on  the   east  coast  of  the  U.S.A. -the brown are more common than black closer to equator -warmer region= more brown individuals


How are crabs adapted against dessication?

-Many  intertidal  organisms  have   gills  which  they  can  use  to   breathe  when  exposed  to  air  as   long  as  the  gills  are  moist -High  intertidal  crab  Scopimera has  a  mambrane on  each  leg   designed  to  exchange  gas  from   the  air  for  uptake  into  arterial   blood


In what three ways can waves damage intertidal organisms?

-1. Abrasion  (sand  in  suspension,  floating  debris,  or  whipping   seaweed  fronds  against  rock) -2. Pressure  (Crushing  of  delicate  or  compressible  structures   e.g.  gas-­‐filled  air  bladders  of  seaweeds) -3. Pressure  drag  (directional  force  of  waves  may  rip  apart  or   dislodge  organisms  or  dislodge  just  their  support  structures   such  as  hold  fasts  and  the  byssal  threads  of  mussels)


How are mussels adapted to wave shock?

Wide  range  of  morphological   adaptations  to  wave  shock: -Mussels  have  thick  shells  and  thick   byssal  threads  for  attachment -Mytilus  edulis  changes  its   attachment  strength  with  season  i.e.   secretes  more  byssal  threads  in   winter  so  it  can  resist  winter  storms   -Individual   mussels  more  vulnerable   to  waves.  Dense  beds  dissipate  wave   forces  along  the  surface  of  the   mussel  bed.   Flow  within  mussel   aggregations  is  0.1%  to  10%  of  free-­‐ stream  velocity.


How is the production of byssal threads affected by the velocity of water?

-4 different species looked at -the mussels make fewer byssal threads with high velocity= so it is not the increase in threads that allows them to stick there -put plaster rods to test how much it falls away= the ones in dense mussel beds= less flow less worn out so they resits the high energy environment by assembling as groups


How is the sea star Pisaster ochraeus adapted to wave shock?

-    Sea  star  Pisaster  ochraeus  living  in  the  intertidal  zone  have  a     harder  and  thicker  integument  compared  to  individuals   living  in  sheltered  waters


How do larval and adult preferences affect the zonation in the intertidal zone?

-Most  invertebrates  in  the  intertidal  produce  larvae -Larvae  must  settle  into  a  suitable  habitat -Larvae  of  many  species  are  able  to  locate  the  tidal  height  suitable  for  adults  of   their  own  species -Preferential  settlement  on  adults   of  their  own  species  (e.g.  the  Australian barnacle  Hexaminius popeiana= can recognise the chemicals -Mobile  animals  can  adjust  their  tidal  height  by  a  combination  of  responses  to   light,  gravity  and   moisture but for sessile really crucial where they settle


How does predation affect zonation in the intertidal zone?

-Predators  often  limited  by  the  time  of  immersion  as   predators  must  be  moist  as  they  move  to  locate  and   ingest  prey -Susceptibility  to  dessication  limits  sea  stars  and   snails  to  the  lower  shore  or  to  refuges  where  water   exists  in  the  intertidal -E.g.  dog  whelks  (Nucella)   emerge  from  moist  cracks   to  prey  upon   barnacles -Mussel  beds  in  California  have  a  sharp  lower  limit   due  to  predation  by  a  large  sea  star  (Pisaster)


How does competition affect zonation in the intertidal zone?

-Intertidal  habitats  may  be  severely  space  limited -Species  capable  of  undercutting  or  overgrowing   others  can  dominate  the  shore  level  where  they  do   well  physiologically -E.g.  mussels  are  able  to  move  by  forming  and   detaching  byssal  threads -This  allows  them  to  climb  on  top  of  competitors  and   smother  them -As  a  result,  mussels  frequently  dominate  the  lower   shore