THE DIATOM FLORA OF PHOSPHORUS-ENRICHED AND UNENRICHED SITES IN AN EVERGLADES MARSH

Abstract

Diatoms are used as environmental indicators in the Florida Everglades, a large subtropical wetland highly impacted by phosphorus pollution. However, the taxonomy of the diatom flora, a mix of temperate and tropical diatoms, is understudied. Therefore, we analyzed the taxonomy of 71 diatom taxa collected in Water Conservation Area 2A (WCA-2A). Diatoms were analyzed from sediment cores and from floating algal mats collected in phosphorus- enriched northern WCA-2A and in relatively unenriched southern WCA-2A. In addition, diatoms were analyzed from experimental mesocosms in southern WCA-2A dosed with 0–126 μgL⁻¹ P-PO₄. Total phosphorus optima were calculated for dominant taxa. Average percent abundances in phosphorus-enriched and unenriched conditions are given for all taxa. Eleven taxa were dominant (>5% abundance in at least one sample) in unenriched conditions, 17 taxa were observed only in phosphorus-enriched conditions, and 9 taxa were observed only below 2 cm in sediment cores. We compared the flora to taxonomical accounts of diatoms from temperate and tropical regions, with a special focus on nearby Antillean islands (Cuba, Jamaica, and Puerto Rico). Light microscope images of each taxon and SEM images of selected taxa are presented. Taxonomical measurements are given for each taxon, and differences from descriptions in other taxonomical accounts are discussed. A new combination, Achnanthes caledonica Lange-Bertalot = Achnanthidium caledonicum (Lange-Bertalot) comb. nov. is proposed.