Seagrasses are marine plants with high photosynthetic efficiency and efficient uptake of carbon dioxide (CO₂). Although they cover less than 0.1% of the ocean surface, they account for about 20% of marine CO₂ burial in sediments. Carbon storage is supported by low oxygen sediment conditions, which slow organic matter decomposition and reduce CO₂ release. Despite their limited spatial coverage, seagrasses are widely distributed in coastal environments and influence nutrient and carbon cycling. This study focuses on the seagrass Halophila stipulacea from the Gulf of Aqaba, an oligotrophic environment with strong seasonal stratification and mixing, and will focus on phosphorus as a case study.
Phosphorus is an essential nutrient in oceanic systems but is often poorly bioavailable in sediments due to binding with iron and calcium. Seagrass can actively uptake inorganic phosphorus through local acidification, thereby recycling the nutrient back to the surrounding environment. Despite its importance, phosphorus measurements in seagrass tissues are still based on non-uniform protocols. To address this gap, an existing laboratory protocol was examined to establish a consistent approach and identify the most suitable method. As part of a broader research, seagrass samples are collected to examine seasonal variability in nutrients, carbon, metals, and chlorophyll across different seagrass tissues. The first sampling campaign took place in February, providing initial results on nutrient and carbon processes in the system. Using the refined phosphorus protocol, these initial samples were measured for the first time with an improved method, providing a baseline for further measurements.