GG2013: Physical Environments Exercise 1

GG2013:  Physical  Environments  Exercise  1  

Student  ID:  51442329  

Reconstructing  palaeo-­‐hydrology  and  environmental  change  in  glaciated   catchments  using  sub-­‐fossil  invertebrate  assemblages.  

    Objective  1  

Suitability  for   Species: 0  -­‐  Unsuitable 1-­‐  Suitable

Figure  1:  Graph  illustrating  the  relationship  between  the  mean  annual  July   temperature  and  the  species  suitability  level  for  4  types  of  invertebrate.         Objective  2  

Figure  2:  Abundance  values  for  selected  species  (no.  of  individuals  per  m2)   at  each  sample  site.     By  taking  the  information  provided  in  Figure  2  along  with  the  map  of  the  field   site  in  Figure  3,  it  is  possible  to  estimate  the  water  temperature  at  each  site  in   relation  to  environmental  conditions  (i.e.  elevation  of  each  site,  vegetation  cover,   what  type  of  stream  the  sample  is  taken  from,  and  any  surrounding  tributaries   which  may  help  explain  any  patterns).  

 

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GG2013:  Physical  Environments  Exercise  1  

Student  ID:  51442329  

  Figure  3:  Map  of  field  site  indicating  location  of  sampling  sites.     The  data  for  site  1  shows  that  there  is  a  presence  of  both  the  Orthocladius  and   Microspectra  invertebrates,  where  the  temperature  suitability  indices  state  that   the  temperature  is  optimum  for  which  they  can  survive  in.  According  to  the   constructed  graph  in  Figure  1,  the  estimated  suitability  point  at  which  the  curves   for  both  invertebrates  are  at  an  optimum  level  of  1  can  possibly  be  around  a   temperature  of  2oC.  This  assumption  complies  with  Figure  3,  as  it  can  be  seen   that  site  1  is  at  an  elevation  of  1200m,  with  very  little  willow  &  birch  scrub  cover.   But  most  importantly,  the  data  for  site  1  was  collected  from  the  St  Mary’s  River,   which  is  directly  fed  by  the  glacial  melt  water  from  St  Mary’s  Glacier;  therefore   the  temperature  of  the  water  will  be  substantially  colder  than  other  sites.   Therefore,  the  water  cannot  be  lower  than  2oC  as  according  to  Figure  1,  any   temperature  below  2oC  has  a  rapid  decline  in  the  species  suitability  on  the  Y-­‐axis,   so  the  estimated  water  temperature  of  site  1  is  2oC.     The  data  for  site  2  shows  that  there  is  a  very  small  presence  of  Orthocladius  and   Microspectra  invertebrates,  along  with  a  much  more  noticeable  presence  of  the   Psectrocladius  invertebrate.  Figure  2  indicates  that  the  presence  of  Orthocladius   and  Microspectra  is  very  small,  with  only  1  and  2  individuals  per  m2  respectively,   which  shows  that  the  temperature  of  site  2  is  not  very  suitable.  Since  Figure  1   shows  that  site  2  has  an  abundance  of  Psectrocladius,  it  is  clear  than  site  2  will  

 

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GG2013:  Physical  Environments  Exercise  1  

Student  ID:  51442329  

have  a  higher  temperature  than  site  1.  This  also  complies  with  the   environmental  factors  surrounding  site  2  shown  in  Figure  3,  as  although  it  is  still   being  sourced  by  St  Mary’s  Glacier’s  melt  water,  it  has  a  lower  elevation  of   1000m,  is  surrounded  by  more  willow  &  birch  scrub  cover  and  has  a  non-­‐glacial   tributary  feeding  into  the  river  system.  In  terms  of  an  estimated  temperature,  it   is  clear  in  Figure  1  that  the  combination  of  the  Orthocladius  and  Microspectra   curves  intersecting  the  Psectrocladius  curve  at  a  point  of  5oC  with  0.5  habitat   suitability,  along  with  Psectrocladius  having  an  optimum  suitability  at  6oC  –  it  is   therefore  possible  to  estimate  the  water  temperature  at  site  2  to  be  5.5oC.     The  data  for  site  3  shows  that  there  is  a  dominance  of  the  Tanytarsus   invertebrate  over  the  other  3,  which  makes  it  more  clear  as  to  what  the   estimated  temperature  can  be.  Figure  3  shows  that  site  3  is  situated  at  an   elevation  of  1200m  on  King’s  Peak,  but  most  importantly  the  Elphinstone  River   is  a  non-­‐glaciated  stream,  so  therefore  the  temperatures  will  be  noticeably   warmer  compared  to  St  Mary’s  River.  But  since  Figure  1  indicates  that  site  4  has   twice  as  many  Tanytarsus  invertebrate  individuals  per  m2  compared  to  site  3,  it   is  clear  that  site  3  does  not  have  the  most  suitable  temperature  for  all  the   Tanytarsus  invertebrates  to  survive.  Therefore,  according  to  Figure  1  it  is   possible  to  estimate  that  the  temperature  at  site  3  is  11oC,  as  on  the  graph  that   point  sits  on  the  0.5  suitability  scale,  half  as  much  as  the  optimal  level.     As  explained  before,  site  4  has  twice  as  many  Tanytarsus  invertebrates  than  site   3,  at  40  individuals  per  m2.  Therefore  according  to  Figure  1,  the  optimal  level  of  1   on  the  Tanytarsus  curve  shows  that  the  estimated  temperature  for  site  4  is  12oC.   The  reasons  for  the  higher  temperature  can  be  due  to  site  4  being  200m  lower  in   elevation  compared  to  site  3,  the  amount  of  willow  &  birch  scrub  cover  being   higher,  along  with  site  4  being  14km  further  South  than  site  3.       Objective  3  

 

Figure  4:  Species  abundance  values  within  each  dated  stratigraphic  layer   and  at  each  sample  site.      

 

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GG2013:  Physical  Environments  Exercise  1  

Student  ID:  51442329  

Layer  1  –  AD  1600   From  the  data  provided  in  Figure  4,  it  is  clear  that  in  AD  1600  both  sites  1  and  3   show  to  have  recorded  0  of  all  four  species.  Comparing  this  data  with  Figure  1,  it   draws  the  assumption  that  the  temperature  of  the  water  at  sites  1  and  3  must   have  been  too  cold  for  the  invertebrates  to  be  present,  so  ideally  where  all  the   curves  show  that  the  species  suitability  level  is  0.  Therefore,  it  appears  that  the   estimated  water  temperature  at  sites  1  and  3  in  AD  1600  would  have  been  0oC  or   below.     On  the  other  hand,  Figure  4  indicates  that  in  AD  1600  sites  2  and  4  have  a  slight   presence  of  Orthocladius  and  Microspectra  invertebrates,  and  from  previous   analysis  we  know  that  these  invertebrates  are  present  in  lower  temperatures   rather  than  warmer.  Since  the  numbers  of  these  invertebrates  are  reasonably   low,  it  can  be  suggested  that  the  suitability  of  the  temperature  is  not  optimum,   and  therefore  when  compared  with  Figure  1  it  is  possible  to  estimate  that  the   temperature  would  be  lower  than  the  optimum  temperature  of  2oC,  more  so   around  the  region  of  0-­‐1oC  with  site  2  having  a  slightly  warmer  temperature   compared  to  site  4  since  there  are  more  invertebrates  present.       Layer  2  –  7000  BC   From  the  data  provided  in  Figure  4,  it  is  clear  that  at  Site  1  there  is  an  equal   presence  of  Psectrocladius  and  Tanytarsus  invertebrates,  and  as  we  know  from   previous  questions,  the  presence  of  these  invertebrates  indicate  a  warmer   temperature  rather  than  colder.  But  if  we  look  at  Figure  1  in  question  1,  and   draw  on  the  fact  that  there  are  equal  numbers  of  both  invertebrates  at  each  site,   the  temperature  can  be  estimated  to  be  the  point  at  which  the  Psectrocladius  and   Tanytarsus  curves  intersect  one  another.  Therefore  the  estimated  temperature   at  site  1  would  be  9.9oC.     From  the  data  provided  in  Figure  4,  it  is  evident  that  Site  2  must  have  a  higher   temperature  as  the  number  of  Psectrocladius  invertebrates  drops  from  20  to  5   per  m2,  whilst  the  number  of  Tanytarsus  invertebrates  increases  from  20  to  40   per  m2,  showing  that  Tanytarsus  are  more  suited  to  warmer  temperatures  in   contrast  to  Psectrocladius.  Therefore,  by  comparing  Figure  1  with  the   assumptions  made,  as  Tanytarsus  numbers  double  and  Psectrocladius  numbers   decrease,  the  estimated  temperature  can  be  10.5oC  as  this  temperature  on  the   graph  shows  a  negative  relationship  in  the  suitability  level  for  Psectrocladius  and   a  positive  increase  for  Tanytarsus.     The  continuous  decrease  in  the  Psectrocladius  numbers  carries  on  when  looking   at  the  data  for  Site  3,  where  Tanytarsus  numbers  increase  to  50  whilst   Psectrocladius  is  not  present  anymore,  therefore  indicating  that  the  temperature   is  higher  at  Site  3  than  Site  2  since  the  number  of  Tanytarsus  invertebrates  has   further  increased.  From  the  information  shown  on  the  graph  in  Figure  1,  it  is   possible  to  estimate  that  the  temperature  at  Site  3  could  have  been  12oC,  since  at   this  point  on  the  graph  the  curve  for  Psectrocladius  invertebrates  is  at  a   suitability  level  of  0,  indicating  that  there  would  be  none  present.    

 

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GG2013:  Physical  Environments  Exercise  1  

Student  ID:  51442329  

Similar  to  Site  3,  Site  4  shows  an  even  further  increase  in  the  number  of   Tanytarsus  invertebrates,  indicating  that  the  temperature  at  Site  4  must  be   warmer  than  Site  3.  Tying  this  assumption  with  Figure  1,  it  is  clear  on  the  graph   that  Psectrocladius  invertebrate  levels  remain  at  0  as  the  temperature  passes   12oC,  so  therefore  the  estimated  temperature  of  site  4  could  be  12.5oC  at  most,   since  the  graph  begins  to  show  that  any  warmer  than  this  and  the  number  of   Tanytarsus  would  begin  to  decrease  as  the  suitability  level  begins  to  decrease.       Question  4  

  Figure  5:  Environmental  reconstruction/sketch  of  Layer  1  (1600AD)     By  combining  the  environmental  reconstruction  of  Layer  1  (1600AD)  shown  in   Figure  5  along  with  the  data  provided  in  Figure  4,  it  is  possible  to  estimate  that   due  to  the  lower  temperatures  and  absence  of  invertebrates  in  sites  1  &  3,  we   can  assume  that  St.  Mary’s  Glacier  could  have  been  situated  further  South  as   compared  to  in  Figure  3.  This  would  provide  enough  evidence  to  suggest  that   Site  1  could  have  been  covered  by  the  glacier,  which  resulted  in  the  absence  of  all   invertebrates  due  to  the  extreme  temperatures  that  the  glacier  brought.  Due  to   the  glacier  covering  more  of  St  Mary’s  River  channel,  this  would  further  explain   why  sites  2  &  4  had  only  very  small  numbers  of  Orthocladius  and  Microspectra   invertebrates  present,  since  the  temperatures  would  have  been  far  too  cold  for  

 

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GG2013:  Physical  Environments  Exercise  1  

Student  ID:  51442329  

Psectrocladius  and  Tanytarsus  invertebrates.  Further  explanation  as  to  why  St.   Mary’s  Glacier  would  have  extended  further  South  would  be  due  to  the  data   provided  in  Figures  3  &  4  in  the  hand-­‐out  booklet,  which  clearly  shows  that  the   temperatures  in  Layer  1  are  recorded  to  have  been  sub-­‐zero  (-­‐20oC),  along  with   high  levels  of  gravel  rich  sediments  at  sites  1  &  3  –  which  could  have  been  as  a   result  from  glacial  erosion/transport.  Also  shown  in  Figure  5  is  a  retreatment  of   willow  &  birch  scrub  cover,  where  due  to  the  colder  temperatures  vegetation   would  have  been  more  scarce,  as  it  has  been  studied  that  shrubs  shed  their   leaves  in  late  summer  to  avoid  autumn  frosts  (Ministry  of  Forests,  1998),  along   with  photosynthesis  not  occurring  at  low  water  temperatures.        

Figure  6:  Environmental  reconstruction/sketch  of  Layer  2  (7000BC)       By  combining  the  environmental  reconstruction  of  Layer  2  (7000BC)  shown  in   Figure  6  along  with  the  data  provided  in  Figure  4,  it  is  possible  to  estimate  that   due  to  the  higher  temperatures  and  presence  of  only  the  Psectrocladius  and   Tanytarsus  invertebrates  in  all  sites,  we  can  assume  that  St  Mary’s  Glacier  could   have  been  retreated  further  North  as  compared  to  in  Figure  3  along  with  an   increase  in  the  amount  of  willow  &  birch  scrub  cover.  Due  to  the  higher   temperatures  and  St  Mary’s  Glacier  retreating,  this  can  provide  further  evidence   of  the  higher  water  temperatures  since  St  Mary’s  River’s  source  is  no  longer  

 

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GG2013:  Physical  Environments  Exercise  1  

Student  ID:  51442329  

glacier  fed,  and  as  we  know  from  Elphinstone  River,  non-­‐glaciated  rivers  have  a   significantly  lower  water  temperature  compared  to  glacier  fed  rivers.  Therefore,   by  St.  Mary’s  Glacier  not  affecting  the  water  temperatures,  it  further  agrees  with   the  gradual  increase  in  the  invertebrates  that  are  suited  to  warmer   temperatures.  The  warmer  temperatures  also  agree  with  the  increase  in   vegetation,  as  photosynthesis  is  able  to  occur  in  the  rivers,  along  with  warmer   temperatures  suiting  willow  &  birch  requirements.               References   Boulton,  Andrew.  'Stream  Ecology,  Temperature  Impacts  On  -­‐  Dam,  River,   Freshwater,  Effects,  Important,  Plants,  Source,  Effect,  Oxygen,   Human'.  Waterencyclopedia.com.  N.p.,  2015.  Web.  18  Oct.  2015.     BRODERSEN,  KLAUS  PETER,  and  OLE  BENNIKE.  'Interglacial  Chironomidae   (Diptera)  From  Thule,  Northwest  Greenland:  Matching  Modern  Analogues   To  Fossil  Assemblages'.  Boreas  32.4  (2008):  560-­‐565.  Web.  18  Oct.  2015.     Forests,  Ministry  of.  'The  Ecology  Of  The  Spruce–  Willow–Birch  Zone'.  British   Colombia  Government  Portal.  N.p.,  2015.  Web.  18  Oct.  2015.    

 

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