Spatial and temporal patterns of the macrobenthic algae community structure in selected intertidal zones of Iligan Bay, Northern Mindanao, Philippines

Abstract

Spatio-temporal patterns of community structure in terms of species composition, biomass, species richness, species diversity, equitability (evenness), and assemblage of the macrobenthic algae and physical factors (nitrate, phosphate, light intensity, water motion, temperature, pH and dissolved oxygen) that influenced their community structure were studied at three sites within the intertidal zones of Iligan Bay, Philippines, namely two southern (Kauswagan, Lanao del Norte and Dalipuga, Iligan City) and one northeastern (Gimangpang, Initao, Misamis Oriental) Iligan Bay sites from August 2008 to August 2009. A total of 63 macrobenthic algae were identified which are distributed as follows: 25 Chlorophyta, 15 Phaeophyta, and 23 Rhodophyta. The genera Caulerpa, Halimeda, Padina, Turbinaria, and Gracilaria had the highest number of taxa in all samples. Gimangpang site had the highest macrobenthic algae species diversity (3.73 ± 1.24), biomass (248.80 ± 5.04 g), and species richness (14.74 ± 5.08 g) during the dry season (February 2009). Pielou’s evenness index was highest in Dalipuga (3.14 ± 1.04), intermediate in Kauswagan (1.35 ± 0.45) and lowest in Gimangpang (0.73 ± 0.24). Constrained canonical correspondence analysis (CCA) showed environmental variables that strongly influenced the assemblages of macroalgae varied with sites. In Kauswagan, assemblage was influenced by light intensity (F = 2.40, P = 0.002) while pH (F = 2.43, P = 0.002) and dissolved oxygen (F = 1.92; P = 0.03) influenced assemblage in Gimangpang and Dalipuga, respectively. Multivariate analysis classified two clusters of sites, namely, the northeastern Gimangpang site, and the two southern Iligan Bay sites, Kauswagan and Dalipuga.