Populations of anaerobic phototrophic bacteria in a Spartina alterniflora salt marsh

Abstract

In salt marsh at Sapelo Island, Georgia, no phototrophs were detected in samples of creekside (low marsh) sediment or in tidal waters in creekside regions. In the high marsh region, 90% of anaerobic phototrophic bacteria occurred in the top 5 mm of sediments; none were detected < 6 mm. There was seasonal variation, with maximal populations occurring in summer and fall (mean 4.4 × 105 phototrophs g of dry sediment-1), minimal numbers in winter (3.9 × 103 phototrophs g of dry sediment-1). During winter and late spring, phototrophs had a patchy distribution over the high marsh sediment surface. During late summer they had a random uniform distribution. Tidal water collected over high marsh sediment contained an average of 8.7 × 102 phototrophs ml-1, with no significant seasonal variation. Anaerobic phototrophic bacteria were also cultured from the lower stem tissue of Spartina alterniflora growing in both the high (4.3 × 104 phototrophs g of dry tissue-1) and creekside (4.9 × 104 phototrophs g of dry tissue-1) marsh regions. Chromatium buderi, C. vinosum, Thiospirillum sanguineum, Rhodospirillum molischianum and Chlorobium phaeobacteroides were the predominant anaerobic phototrophic species cultured from high marsh sediment. The Chromatium species were dominant. -from Authors