CHRYSOPHYCEAN STOMATOCYSTS FROM COSTA-RICAN TROPICAL LAKE-SEDIMENTS

Chrysophycean stomatocysts were identified and described from the surf ace sediments of 30 Costa Rican lakes located mostly in the interior r egion, from the Cordillera de Guanacaste in the north to the Cordiller a de Talamanca in the south. The lakes differ widely in their origins and physical characteristics, but they are, for the most part, fresh, poorly buffered, oligotrophic, and have a pH < 7.8. One hundred and fi ve chrysophyte cyst morphotypes were identified from the sediments. A high percentage (42%) of previously unidentified morphotypes is though t to be due to the paucity of cyst studies from tropical lakes. Suffic ient numbers of cysts for enumeration occurred in only 15 of the study lakes.