Associations between water chemistry and fish community composition: a comparison between isolated and connected lakes in northern Sweden

• Published in: Freshwater Biology
• Main Authors: ÖHMAN, JOHANNA, BUFFAM, ISHI, ENGLUND, GÖRAN, BLOM, ANDREAS, LINDGREN, EMMA, LAUDON, HJALMAR
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2006
• Subjects: Northern Sweden
• Online Access: http://dx.doi.org/10.1111/j.1365-2427.2006.01514.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1365-2427.2006.01514.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2427.2006.01514.x

Summary 1. The correlation between water chemistry, physical variables and fish community composition was examined in 40 small (≤30 ha) coastal lakes in northern Sweden. Twenty of the 40 lakes were isolated from other water bodies and 20 were connected to the Baltic Sea. Lakes were fished in summer, using three different methods. Water chemistry was sampled in late winter prior to ice‐out and pH was measured additionally in summer. 2. Our central question was whether water chemistry plays a greater role in the composition of fish communities in isolated lakes than in connected lakes, as isolated lakes cannot be recolonised once a species has become extinct. 3. Results indicate that winter anoxia affects community composition only in isolated lakes, whereas acidity is of importance in both connected and isolated lakes. Methane (indicating anoxia), was significantly correlated with variation in fish community composition in isolated lakes, and a group of variables that indicate anoxia (CH 4 , pCO 2 , inorganic carbon and dissolved oxygen) explained 24–34% of the variation. pH alone explained 12% of the variation in community composition for connected lakes and a group of variables indicating acidity (summer and winter pH and ANC) explained 10–20% of the variation in isolated lakes. Lake area was the most important physical variable, being significantly correlated with the variation in fish community composition in connected lakes. 4. In isolated lakes, the presence of pike ( Esox lucius ), perch ( Perca fluviatilis ) and roach ( Rutilus rutilus ) was associated with low CH 4 . The occurrence of crucian carp ( Carassius carassius ) and roach was positively correlated with pH, and the crucian carp was apparently also affected by predation by pike and perch. In connected lakes the effect of anoxia was low, probably due to the possibility of recolonisation and pockets of oxygenated water, allowing pike and perch to persist and thereby limiting the distribution of crucian carp.