Opportunist rotifers: colonising species of young ponds in Surrey,England

Quantitative substrate samples were collected at a newly constructed gravel bar habitat in the Tombigbee River, Mississippi, to characterize oligochaete (naididae and tubificidae) species richness and community composition. A total of 28 species of naidid and tubificid worms were indentified during the three-year study; Nais pardalis, Dero nivea, D. obtusa, Pristina aequiseta (naididae), and Branchiura sowerbyi (Tubificidae) were dominant. In June, 1985, three months after construction, 30 samples yielded seven taxa of oligochaetes; naidid and tubificid densities (± standard deviation) were 12.9 (± 29.7) and 10.1 m^–2 (±39.6), respectively. In October, 1985, 20 taxa were identified, and naidid and tubificid densities were 387.9 (± 300.5 and 22.9 m^–2 (± 50.7), respectively. Tubificid densities were highest in the spring, except during the first year, and naidid densities showed their highest densities in the fall during all years. Dominance changed from Nais pardalis and Dero nivea during the first year to Pristina aequiseta and D. nivea during the last year. The naididae, which typically inhabit gravel, exhibited more uniform colonization patterns than did the tubificidae. Comparatively low densities characterized the oligochaete community during the first year and high naidid densities during the last. Because this gravel bar is relatively isolated from similar substrates, and since oligochaetes disperse only via drift or crawling, colonization processes have been slow.