Description: This study was undertaken as part of a collaborative project titled Biotechnological Applications of Marine Biofilms developing on solid surfaces in the Arabian Gulf funded by research grant (SQU-GCC/CL/17/02). The succession of marine biofouling communities (mature biofilms) on plastic panels were investigated over a period of six months in four locations in the Arabian Gulf (Fintas and Salmiya marinas in Kuwait, and Bandar Rowdha and Al Mouj marinas in Oman). Monthly assessment of the physico-chemical parameters of the seawater at each location was done using portable meters (thermometer, refractometer, pH meter, turbidity meter and conductivity/TDS meter). The concentrations of nutrients and elements were analysed using ion chromatography (IC) and inductively coupled plasma optical emission spectrometry (ICP-OES), respectively. After each month, the developed biofilm on each panel was quantitatively and qualitatively analyzed as follows; total wet weight, abundance of bacteria using epifluorescence microscopy, chlorophyll a concentrations using spectrophotometry, percent coverage of macrofoulers, and presence or absence of signs of grazing based on visual observations and/or photodocumentation (using Image J software), which was also used to assess the presence/absence and dominance of macrofouling species. Additionally, the composition of the microbial community was investigated using 16S amplicon sequencing, resulting in supplementary data sets for bacterial community composition, predicted bacterial metabolic pathways (Bowman and Ducklow 2015, doi:10.1371/journal.pone.0135868), and presence/absence of microalgae based on their chloroplast 16S.

Description: Physicochemical parameters and relative abundance of selected nutrient cycling genes were measured in sediment and pore water samples taken from a fish farming area (Site S3 16◦23.097 N, 119◦55.551 E, depth 12.6m) and a control site (Site S1 16◦22.960 N, 119◦54.723 E, depth 15m) not influenced by fish farming. From each site, five pairs of cores representing five biological replicates were collected. One core from each pair was used for physicochemical analysis while the other cores were used for microbial community analysis. Samples from S1 were collected on 2017-06-10 and samples from S3 were collected the following day. The following parameters were measured from the sediment: grain size distribution, % Carbon (%C), % Nitrogen (%N), % total organic carbon (%Corg), and stable isotope (d13C and d15N) content. The following were measured in the pore water: dissolved organic carbon (DOC), total dissolved nitrogen (TDN), ammonium, phosphate, and silicate. Nitrogen (bacterial ammonia monooxygenase/ amoA and nitrite reductase/ nirK) and sulfur (dissimilatory sulfate reductase/ dsrA and sulfur oxidation/ soxB) cycling genes were quantified and normalized against the abundance of the 16S rRNA gene.