Productivity estimation of Zostera marina on the southern coast of Korea: Effects of leaf marking height and duration

The effects of marking height and duration were examined to determine optimal marking height and duration for accurate productivity estimation of eelgrass, Zostera marina, on the southern coast of Korea. Shoots were pierced through the sheath at 2, 5, and 8 cm above the meristem and through the leaf blade at 1 cm above the blade/sheath junction (+ 1 cm blade). The marked shoots were collected weekly during periods of 4-week duration; the experiments were conducted seasonally. Leaf productivities were estimated using three measurement methods, the conventional leaf marking method (CLM), Short '87 method (Short, 1987; Gaeckle and Short, 2002), and plastochrone method. The optimal marking height and duration for leaf productivity estimation varied with the measurement method. CLM and the Short '87 method, but not the plastochrone method, were affected by marking height. The productivity estimates were lowest with a 2-cm marking height treatment due to injury of immature leaf blade tissues. The highest marking height on the sheath gives a more reliable productivity estimate with CLM, whereas any location on the sheath other than the base was appropriate as a marking point for the Short '87 method. CLM and the plastochrone method, but not the Short '87 method, were significantly affected by marking duration. CLM underestimated leaf productivity with less than a 1- or 2-week marking duration because more immature leaf tissues were counted with shorter marking durations. The marking duration should be longer than the plastochrone interval (about 2 weeks in this study) to prevent under- or overestimation of leaf productivity, but the duration should not be longer than the triple-plastochrone interval (about 6 weeks in this study) to prevent underestimation due to the sloughing off of the marked leaves.