Abundance, biomass and growth rates of Synechococcus sp. in a tropical coastal ecosystem (Philippines, South China Sea)

The abundance, biomass and growth rates of Synechococcus sp. were estimated in a tropical coastal ecosystem (Philippines, South China Sea). The patterns of change of these parameters were further examined in relation to human-derived disturbance such as siltation, and by short-term episodic disturbances such as the typhoons, which are frequent in the region. The average abundance and biomass of Synechococcus sp. in the coastal ecosystem ranged from 0.13 to 21 × 10⁶ cells l^-1, and from 0.01 to 1.6 mg C m^-3, respectively, with higher biomass occurring near river sources rich in inorganic nutrients. There was, however, a significant decline of specific growth rates and maximum frequency of cells in division with increasing siltation, which suggests a deterioration of the environmental conditions to support picocyanobacterial populations. The low biomass of Synechococcus sp. in more pristine sites, in spite of relatively high growth rates there suggests that loss factors (i.e. grazing) are important in controlling the biomass in the area. The temporal pattern of picocyanobacterial abundance in the tropical ecosystem studied was tightly coupled with their temporal patterns of growth indicating that changes in abundance may result from changes in growth rate. There was not, however, a clear annual pattern of Synechococcus sp. abundance in the study site but there was some evidence for effects of storms on Synechococcus sp. abundance.