The fouling organisms at Songkhla Port were investigated from November 2011 to December 2012. Samples were collected using PVC panels (10 cm x 20 cm) submerged for one-month and three-month periods. Analysis of fouling panels was carried out using PhotoGrid software. In addition to slime and silt, three types of fouling organisms, namely encrusting bryozoa, barnacles and calcareous polychaetes, were observed on the submerged PVC panels. Calcareous polychaetes and molluscs were the most diverse groups (ten species) on panels that were submerged for one-month and three-month periods. Barnacles (Balanus spp.) were most abundant on panels submerged for three-month periods, while calcareous polychaetes dominated one-month panels. The dominant species of mollusc was the mussel Brachidontes sp. The major polychaetes identified were Ficopomatus macrodon, F. enigmaticus and Hydroides norvegicus. A highlight of this study was the first record of the Caribbean tubeworm Hydroides sanctaecrucis in Thailand, which has previously invaded and established in Australian waters through hull fouling.

Benthic fauna plays an important role in marine ecosystems as the primary food for other aquatic animals, and this animal group helps reduce sediment nutrients by filter feeding. The aim of this study was to evaluate and explain the diversity and abundance of the benthic fauna community at the Songkhla port, where both human activities and environmental fluctuations affect this community. Benthic fauna and water samples were collected at 2-month intervals from January to November 2017. The results show that most physical parameters had wide ranges and varied by month. The benthic fauna in the Songkhla lagoon was observed in this study. The results showed a higher number of taxa compared with a previous study. Three phyla, namely, Annelida, Arthropoda, and Mollusca, had 25 taxa recorded in this study. Crustaceans were the most diverse (nine taxa) and abundant (2981 6 313 ind/m 2 ) group, followed by polychaetes (eight families, 2350 6 288 ind/m 2 ) and mollusks (eight taxa, 633 6 200 ind/m 2 ). Barnacles were the dominant group of crustaceans (2153 6 758 ind/m 2 ), whereas Serpulidae (1864 6 647 ind/m 2 ) and Mytilidae (447 6 367 ind/m 2 ) were the dominant families of polychaetes and mollusks, respectively. Cluster analysis showed that the distribution of benthic fauna and physicochemical water quality varied with similar patterns. Clustering gave two groups: for rainy season from November to January and for dry season from May to November. According to canonical correspondence analysis, salinity and transparency were the main environmental factors associated with the distribution pattern of benthic fauna in the area. In conclusion, the activities at the Songkhla port have not yet created problems for marine benthic fauna; instead, seasonal changes appear to drive changes in benthic fauna. However, future construction developments can affect the geographical area, complementing stresses from parameter changes at local scales.