DIATOM (BACILLARIOPHYTA) COMMUNITY RESPONSE TO PHOSPHORUS IN THE EVERGLADES NATIONAL-PARK, USA

The Everglades National Park, a World Heritage site, is showing the first signs of nutrient impacts caused by intensive agricultural farming north of the Park. Investigations have shown that sediments in the Park are advectively accumulating phosphorus. At the study site, median total phosphorus concentration inflows have increased from 7 to 12 mug 1(-1) and the TN:TP ratio has decreased from 250 to 120 over a 12-year period. Periphyton diatom mean diversity and taxon numbers are increasing in association with increased amounts of sediment phosphorus. Cymbella pusilla Grunow and Anomoeoneis vitrea (Grunow) Ross were generally predominant at less impacted far-field stations but yielded in predominance to Nitzschia palea (Kutzing) W. Smith, Fragilaria vaucheriae (Kutzing) Petersen var. capitellata (Grunow) Patrick, and Cymbella microcephala Grunow at phosphorus-enriched near-field stations. Two non-predominant indicators of phosphorus enrichment, Gomphonema parvulum Kutzing and Nitzschia amphibia Grunow, showed a response to increased sediment phosphorus along the transect. These diatom community responses are the forerunner of undesirable changes experienced in the upper everglades where cattails (Typha spp.) replaced sawgrass (Cladium jamaicense Crantz).