Distribution of Family Spionidae (Annelida: Polychaeta) in the Calamianes Islands, Northern Palawan, Philippines

Abstract

The distribution of family Spionidae (Annelida: Polychaeta) in the Calamianes group of islands, northern Palawan, Philippines was investigated. Sampling was conducted in a total of 21 stations using a van Veen grab. The depths (m) and sediment regime in these stations were also determined. The spionids were selected for this study because this group was the most abundant polychaete family in the samples. A total of 96 individuals divided into 14 species belonged to the family Spionidae, with Spiophanes soederstromi, Spio filicornis, and Prionospio pinnata as the top three species. Overall mean density of the 14 species was 48.8ind・m^<-2>. A geographical pattern was observed in the distribution of the specimens wherein specimens were found only in the peripheral stations (i.e. those fringing the islands), while there was an absence of specimens in the 9 centrally-located stations (non-fringing). The Q-mode cluster analysis revealed that the distribution of Spionidae in the 21 stations was divided into 2 major clusters and 3 station groups, namely cluster 1 with the 9 centrally-located stations, and the peripheral stations classified as Clusters 2A & 2B. The absence of the specimens in the centrally-located stations (Cluster 1) was attributed to the high percentage of sand and a very low silt-clay component in these stations. A 2-way ANOVA showed that spionid density significantly affected the observed clustering pattern. The peripheral stations were also shallower in depths and nearer to habitats such as seagrasses and mangroves. Thus, higher spionid abundance was associated not only with finer sediments experiencing low wave action, but also with areas nearer islands, which were ideal sinks for organic matter.