Flash ea 3000

The content of chlorophyll and carotenoids in leaves was determined by a simplified spectrophotometry method (Shu et al., 2010 ). A leaf with known weight was extracted overnight in 5 mL of 80% acetone solution, and the volume of the extracted solution was determined in 5 mL. The optical density was read at 663, 645, and 470 nm, respectively, by spectrophotometry, and the content of photosynthetic pigments was calculated by the following formulae:
Chl a (μg mL^–1) = 12.7 OD₆₆₃–2.69 OD₆₄₅Chl b (μg mL^–1) = 22.9 OD₆₄₅–4.86 OD₆₆₃Carotenoid (μg mL^–1) = (OD₄₇₀–3.27 Chl a–104 Chl b)/229
Leaf length, leaf width, and root length were measured for five randomly selected leaves from each group. Seagrasses were carefully retrieved, separated into aboveground and belowground tissues, and subsequently dried at 60°C for 72h until a constant weight was achieved. Seagrasses were then homogeneously powdered. The total carbon and nitrogen of seagrasses were analyzed using an Elementary Analyzer (Flash EA 3000, Thermo Scientific, Milan, Italy).

The collected samples underwent a process of air-drying at ambient room temperature. Subsequently, they were meticulously sieved through 35 mesh screens to eliminate any coarse impurities. The remaining fine particles were then finely ground using a mortar and pestle. To determine the soil pH, a 1:2.5 (w/w) suspension of the soil samples was prepared, and the pH analysis was conducted using a pH meter (pH 211, Hanna Instruments, Germany), adhering to the method outlined by Acosta-Martínez et al. (2007) (link). Furthermore, the analysis of total organic carbon (TOC) and total nitrogen content (TN) was carried out utilizing an advanced Elemental Analyzer (Flash EA 3000 Thermo Scientific, Milan, Italy), following the methodology established by Zhao et al. (2019) (link). Total phosphorus (TP) was determined by the H₂SO₄–HClO₄ digestion method (Kuo, 1996 ). Chl a content was measured based on described by Wang et al. (2022) (link). The grain-size components of samples were analyzed using a laser particle sizer (Malvern Mastersizer 2000) as previously described (Tian et al., 2019 (link)).