A comparison of hole punch and needle punch methods for the measurement of seagrass productivity

Seagrass productivity, as leaf extension, was measured using the hole punch and needle punch techniques. These methods have been widely implemented to determine seagrass leaf extension rates, yet there is no evidence in the literature of a comparison between methods. The hole punch method involves removing part of the basal area of a seagrass leaf and it was proposed that this measurement technique may affect the leaf extension rates that are being measured. Leaf extension rates were measured in Posidonia sinuosa meadows off the coast of Perth, Western Australia. There were no significant differences in seagrass leaf extension between the two methods. The hole punch method is favoured, as measurement of incremental leaf growth is facilitated by the obvious hole left by the punch. The needle punch method leaves lesions on seagrass leaves that are easily confused with other lesions, possibly left by invertebrate grazers. These findings are likely to be applicable to other straplike seagrass species, though a similar comparison is recommended in the initial stages of a study. (c) 2006 Elsevier B.V All rights reserved.