Spatio-temporal Variability in Macroalgal Biomass in the Central Arabian Gulf

Abstract

Marine macroalgae are productive multicellular photosynthetic eukaryotes that cover around 28% of the world's coastal environments. They are critical primary producers, commonly known as seaweed, that have complex thallus structures and may reach several meters in length, forming underwater forests. They play a significant role in the global carbon and oxygen cycles, acting as a valuable carbon sink. Moreover, they provide critical habitats for enormous invertebrates and fish larvae. From an applied perspective, they seem to be a promising renewable source for bioenergy fuel, bioplastics, fertilizers, and animal feed. Despite their importance, studies on macroalgae distribution in the Arabian/Persian Gulf are limited to descriptive small-scale studies in the areas off Iran and Kuwait. There is lack of information on the biomass, distribution, and function of macroalgae in the Gulf and in Qatar. The present study examines the spatio-temporal variability of macroalgal biomass in the Qatari coastal waters of the central Arabian Gulf. The study aims to characterize the dominant macroalgal species, assess their seasonal and spatial distribution, and evaluate the underlying environmental factors influencing their pattern. Quantitative sampling was conducted twice a year (summer and winter) across five coastal transects at depths ranging between 1 to ~ 10 meter. The collected macroalgae were stored in -20 ℃, sorted, identified to species level, dried, powdered, and processed for biomass and elemental composition (C, H, and N). Simultaneously, water samples were analyzed for a variety of nutrients (NO2-, NO3-, NH₃+, PO₄3-) in addition to physicochemical parameters in the field (temperature, salinity, pH, DO). Univariate and multivariate statistical analyses (PCA) were conducted to examine the effect of abiotic factors on the macroalgal biomass distribution. These analyses were performed using statistical software (SPSS and Origin Pro). The results of our study are important to understand the macroalgal ecology and biodiversity, as well as the management of resources for the application of bioenergy, especially in the extreme environment of the Gulf.