Seasonal Changes in the Biochemical Composition of Dominant Macroalgal Species along the Egyptian Red Sea Shore

SIMPLE SUMMARY: Macroalgae play a significant role as primary producers in marine ecosystems. The most dominant species at the three collection sites studied along the Egyptian Red Sea were seasonally harvested. Among several species collected, five dominant macroalgae (Caulerpa prolifera, Acanthophora spicifera, Cystoseira myrica, Cystoseira trinodis and Turbinaria ornata) were selected for further studies. These macroalgae were identified using morphological and molecular characteristics. During summer and winter, the mineral content and biochemical composition of the selected macroalgal species were evaluated. These analyses indicated that macroalgae are rich in minerals as well as primary and secondary metabolites. Moreover, the findings reported that the macroalgae studied possess high nutritional value in the summer more than in the winter season. ABSTRACT: Macroalgae are significant biological resources in coastal marine ecosystems. Seasonality influences macroalgae biochemical characteristics, which consequentially affect their ecological and economic values. Here, macroalgae were surveyed from summer 2017 to spring 2018 at three sites at 7 km (south) from El Qusier, 52 km (north) from Marsa Alam and 70 km (south) from Safaga along the Red Sea coast, Egypt. Across all the macroalgae collected, Caulerpa prolifera (green macroalgae), Acanthophora spicifera (red macroalgae) and Cystoseira myrica, Cystoseira trinodis and Turbinaria ornata (brown macroalgae) were the most dominant macroalgal species. These macroalgae were identified at morphological and molecular (18s rRNA) levels. Then, the seasonal variations in macroalgal minerals and biochemical composition were quantified to determine the apt period for harvesting based on the nutritional requirements for commercial utilizations. The chemical composition of macroalgae proved the species and seasonal variation. For instance, minerals were more accumulated in macroalgae C. prolifera, A. spicifera and T. ornata in the winter season, but they were accumulated in both C. myrica and C. trinodis in the summer season. Total sugars, amino acids, fatty acids and phenolic contents were higher in the summer season. Accordingly, macroalgae collected during the summer can be used as food and animal feed. Overall, we suggest the harvesting of macroalgae for different nutrients and metabolites in the respective seasons.