Recent advances have improved ease and accuracy in seagrass growth measurements. Despite these improvements, seagrass leaf growth can be difficult to measure effectively; current methods are destructive to the plants and require at least two site visits per growth period. We used the "previous growth" of Ibarra-Obando and Boudouresque [Ibarra-Obando, S.E., Boudouresque, C.F., 1994. An improvement of the Zieman leaf marking technique for Zostera marina growth and production assessment. Aquat. Bot. 47, 293-302.] to develop a relationship between sheath length and leaf growth in eelgrass, Zostera marina L., and we demonstrated that a simple, non-destructive method allows reliable calculation of eelgrass leaf growth (mg shoot-1 day-1) based on sheath length. We measured eelgrass sheath length and leaf growth for 18 months, from November 1999 to April 2001, at a site in Portsmouth Harbor on the border of New Hampshire and Maine, USA. Regression analyses showed a high coefficient of determination between sheath length and leaf growth, demonstrating that sheath length reliably reflected eelgrass leaf growth. We also showed that four seasonal measurements were sufficient to establish a significant relationship between sheath length and leaf growth. After a regression of sheath length and leaf growth has been established for a site, eelgrass sheath length can be measured in situ to accurately calculate leaf growth, eliminating both the need for destructive growth measurements and the need to mark and relocate plants.
- Sheath length