Summer Plankton of Lake Amatitlan, Guatemala

Abstract

Previous studies of plankton from Guatemala lakes, by Meek (1908); Clark (1908); and Tilden (1908); have been purely qualitative in nature. Juday's (19,16) limnological study of Lake Amatitlan, however, included a single series of quantitative plankton collections at various depths. The present paper is a report on a series of quantitative collections taken from Lake AmatitIan over an eight-week period during the summer of 1951. General description of the lake.-Lake Amatitlan is of volcanic origin and is situated at 90030' west longitude and 14025' north latitude in the Republic of Guatemala. It is eight miles long, 21/2 miles wide and with a surface of 3870 feet above sea level. A crossing of the International Railways of Central America divides the lake into two basins. Mountains, 4670-5170 feet above sea level, surround the lake; those of the northwest are composed of granite; the others are principally of volcanic ash, pumice, and other loose materials which are easily eroded. The mountains to the north and northwest show evidence of erosion in the form of huge cuts which are visible for several miles. Entering the lake on the north side is the Villalobos (Lobos) River, which is the main affluent stream during the dry season. The single outlet is the Michatoya River which drains the northwest basin from the south. The greater part of the lake shore is steep, especially to the east and southeast. Half or more of the north and northeast shores consist of a broad, low plain which 'has been built up by the LoSos River and temporary streams which enter the lake from the north and northwest during the rainy season (MayNovember).