Lake Alchichica displays a characteristic cyanobacterial bloom associated with the onset of the stratification period. It mostly consists of the nitrogen-fixing cyanobacterium Nodularia spumigena. Filaments of Nodularia were straight, usually with an evident colorless, transparent sheath, with gas vesicles and without akinetes. The bloom developed in waters with a conductivity of 13.47 to 14.14 mS/cm. Water column temperature was between 14.1 and 21.2 C, the pH fluctuated between 8.8 and 10.0 and dissolved oxygen between 0 and 9.3 mg/l. The annual mean concentration of N-NO3 was highest in 2001 and lowest in 2000. For P-PO4 the highest mean value was measured in 2002 with the lowest value in 1999. We monitored the bloom throughout four annual cycles. The intensity of growth and extent of the presence of N. spumigena in Lake Alchichica differed among the years. The highest mean density was observed in 2001, while the lowest values were found in 2000. N. spumigena is found regularly during a three-month period, but peak concentrations are reached only for a few weeks. In calm weather and following solar heating, the Nodularia filaments floated to the lake surface, causing the bloom to become apparent. The intensity of growth was correlated with the annual concentrations of N-NO3, indicating the role of the cyanobacteria as a source of new nitrogen to the lake.
Oliva, Maria Guadalupe; Lugo, Alfonso; Alcocer, Javier; Peralata, Laura; and Oseguera, Luis Alberto
"Planktonic bloom-forming Nodularia in the saline Lake Alchichica, Mexico,"
Natural Resources and Environmental Issues:
Vol. 15, Article 22.
Available at: http://digitalcommons.usu.edu/nrei/vol15/iss1/22