LAKE OHRID : A UNIQUE ECOSYSTEM

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LAKE OHRID A UNIQUE ECOSYSTEM ENDANGERED BY
EUTROPHICATION ?
Andreas Matzinger, Elizabeta Veljanoska, Momcula
Jordanoski Trajce Naumoski
Limnological Research Center EAWAG,
Kastanienbaum, Switzerland Hydrobiological
Institute, Ohrid, Macedonia
Finacially supported by the Swiss Secretariat for
Economic Affiars (seco) the Swiss National
Science Foundation
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General Information Max. length 30 km Max.
width 14 km Surface area 358 km2 Volume 54.7
km3 Mean depth 150 m Max. depth 287.7 m Age
mid pliocene (3 - 5 Mio a) Endemism gt 150 spec.
(10 fish, plants ?)
Lake Topography by Croatian Navy (1974) Map
redrawn from Naumoski T. (2001)
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Feared Eutrophication
Action in time is important
? negative effect on unique fauna and flora
? sluggish lake system (t 70 yr)
? slow bottom water exchange
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Phosphorus concentration
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Lake sediments A look back in time
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Linear Model Approach
Total load 41 t P yr-1
Pmean 4.5 µg l-1
51 t a-1
13 t a-1
P-residence time scale t 6 years
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Reaction to changes
?Pinp 27 t P yr-1
t
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Conclusions

• Lake Ohrid is in a process of eutrophication
• Detection is difficult ? e.g. biological
  observations might be more sensitive (goal
  preserve endemism)
• P is a good indicator for large-scale changes

Outlook

• Combination of changes in geochemical cycles with
  physical and limited biological parameters in a
  dynamic lake model
• Scenario analysis

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FIN
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Lake Ohrid, 16-Jan-2003
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Sediment cores
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OHRID
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