Bioecology of Sediment-Polychaete in Estuarine Subtidal Habitat on Bonny River, Nigeria

Abstract

Midchannel subtidal Polychaete Fauna were collected at the Bonny-estuary and analysed for their composition and abundance in relation to biotic and abiotic factors that are associated with life history strategies through a twelve-month cycle. The diversity index of Shannon-Weiner (0.637 to 2.252) showed that monthly diversity ranges from low to moderate, while the diversity index of Margalef (0.558 to 2.667) showed a moderate to high species diversity. Two Polychaete associations were identified -the generalists made up of 12 species with frequent occurrences and the specialists made up of 13 species with single month occurrences. The species turnover among the specialists with single month occurrences seems to be governed by environmental processes. In contrast, the generalists with the ability to recur throughout the sampling period seem to be less restricted by the prevailing environmental conditions. A positive correlation was observed between Polychaete abundance and silt/clay (p>0.05 r = 0.5429) and organic matter (p>0.05 r = 0.8857), which shows that both organic matter and silt/clay were important in promoting the abundance and diversity of the Polychaete fauna in the study area. The study provides evidence that variation in occurrence of the Polychaetes operates on a range of scales with differing responses to abiotic variables. This should be considered in environmental impact assessments and monitoring studies to fully account for observed distribution.