Meiofauna is important food source for higher trophic levels and facilitate the biomineralisation of organic matter in the ecosystem. The present study aims to determine the biodiversity of meiofauna with special emphasis on the harpacticoid copepods in seagrass beds of Pujada Bay, The Philippines. Triplicate meiofauna samples were collected using PVC meiocores in sediment spots adjacent to the seagrasses Halophila minor, Halodule uninervis, Syringodium isoetifolium and Thalassia hemprichii. The samples were processed in a standardised way, counted and identified up to higher taxa for meiofauna and genus level for harpacticoid copepods. Diversity indices were calculated corresponding to the spatial levels of hierarchical biodiversity: alpha, beta and gamma. Appropriate statistical analysis was used to test the variance of diversity and abundance. Available data of other locations (Mexico & Kenya) sampled following the same protocol as in The Philippines were incorporated and interpreted for the gamma diversity ofharpacticoid copepods. Average meiofauna densities in the upper sediment layers (0 to 3 cm) in all seagrass species ranged from 123 to 567 ind./10 cm2. The most abundant meiofauna groups in sediment layers and along the tidal gradient are Nematoda (37-92%) followed by harpacticoid copepods (4.0-40.6%). Harpacticoid copepods are highly diverse on the surface sediments (No: 3.0-13.0; 0-1 cm) in all seagrass species. There is also a significant turnover of harpacticoid copepods observed along the tidal gradient, indicating the habitat specificity of harpacticoid behaviour along the environmental gradient. The major contributor to the total diversity of harpacticoid copepods in Pujada Bay is its high alpha diversity (94.7%), suggesting the high heterogeneity of the sediment layers and influencing the increase in species richness of these organisms in the location. Geographically, alpha diversity is the primary contributor to the total diversity of harpacticoids based on genus richness and abundance. Although beta diversity (diversity change between seagrass species) showed low contribution to the total diversity, it is still important in harpacticoid community structure because seagrass forms are essential source for the production of detritus, the food of harpacticoid copepods. The location factor has slightly influenced the increase in harpacticoid copepod richness due to the possible inclusion of rare species to the total diversity. Compared to the other two tropical regions, The Philippines showed the highest gamma diversity of harpacticoid copepods, which supports the East lndies spotof diversity. |
