Productivity estimation in Halodule wrightii Aschers: comparison of leaf-clipping and leaf-marking techniques and the importance of clip height

Abstract

We compared estimates of Halodule wrightii leaf growth rates obtained from leaf-clip- ping and leaf-piercing methods in a south Texas lagoon. Leaf clipping underestimated leaf produc- tion from 15 to 37% in winter and 25 to 60% in summer relative to leaf piercing. The underestimation of leaf-clipping derived growth rates were corrected using a linear regression between leaf growth rates determined by leaf-clipping and leaf-piercing methods. To examine the effect of clip height on H. wrightii leaf growth rate estimation, leaves were clipped at 0, 2, 4, 6, and 8 cm above the sediment. Leaves clipped at 2 cm exhibited the fastest leaf growth rate (average = 3.66 mm d -1 ) while leaves clipped at 8 cm had the slowest rate (average = 2.30 mm d -1 ). Depressed leaf growth rates for 8 cm clip height were likely due to the slowing of growth rate with increasing leaf age. Reduced growth rate for the 0 cm clip height treatment may be attributable to removal of nearly all photosynthetic tis- sue and limited below-ground resources. In design of leaf-clipping studies, it is suggested that the selection of clip height and the period of growth after clipping be optimized for each season of a study.