Nutrient dynamics in shallow lakes of Northern Greece.
GOAL, SCOPE, BACKGROUND: Shallow lakes display a number of features that set them apart from the more frequently studied deeper systems. The majority of lakes in Northern Greece are small to moderate in size with a relatively low depth and are considered as sites of high value of the wetland habitat. However, the water quality of these lakes has only been evaluated segmentally and occasionally.


OBJECTIVE
The objectives of this study were to thoroughly investigate nitrogen and phosphorus speciation in lakes of a high ecological significance located in N. Greece, in order to evaluate their eutrophication status and possible nutrient limitation factors, and to investigate the main factors/sources that affect the water quality of these systems.


METHODS
An extensive survey was carried out during the period from 1998-1999. Water samples were collected on a monthly basis from lakes Koronia, Volvi, Doirani, Mikri Prespa and Megali Prespa located in N. Greece. Water quality parameters (temperature, dissolved oxygen, pH and conductivity), organic indices (COD, BOD5), and N- and P-species (NO3(-), NO2(-), NH4(+), and PO4(3-), Kieldahl nitrogen and acid-hydrolysable phosphorus) were determined according to standard methods for surface water. Statistical treatment of the data was employed.


CONCLUSIONS
The physicochemical parameters determined in the lakes studied revealed a high temporal variation. The trophic state of the lakes ranged from meso- to hypertrophic. The nutrient limiting factor varied among lakes suggesting either P-limitation conditions or mixed conditions changing from P- to N-limitation throughout the year. Urban/industrial activities and agricultural runoff are the major factors affecting all lakes, although with a varying contribution.


CONCLUSIONS
This lake-specific research offers valuable information about water quality and nutrient dynamics in lakes of significant ecological value located in N. Greece that can be useful for an effective pollution control/management of these systems. Due to the large intra-annual variability of certain physicochemical parameters, a properly designed monitoring program of lake water is recommended.
Environmental Pollution Control Laboratory, Department of Chemistry, Aristotle University of Thessaloniki, GR-541 24 Thessaloniki, Greece.
Christina
C
Petaloti
Dimitra
D
Voutsa
Constantini
C
Samara
Mihalis
M
Sofoniou
Ioannis
I
Stratis
Themistocles
T
Kouimtzis
D000383:Agriculture; D004784:Environmental Monitoring; D005068:Eutrophication; D005618:Fresh Water / Q000032:analysis* / Q000737:chemistry; D006115:Greece; D006863:Hydrogen-Ion Concentration; D007221:Industry; D009584:Nitrogen / Q000032:analysis*; D010758:Phosphorus / Q000032:analysis*; D025341:Principal Component Analysis; D013696:Temperature; D014867:Water / Q000592:standards; D014873:Water Pollutants / Q000032:analysis
D014873:Water Pollutants; D014867:Water; D010758:Phosphorus; D009584:Nitrogen