Appendix B. Evaluating estimates of kelp performance.
To quantify CHN, a blade near a growing apical meristem and newly growing haptera were sampled randomly from three individuals in each plot of kelp and from 12 individuals from the natural reef at the end of this experiment. Samples were dried at 35º C to prevent loss of CHN and then pulverized into a fine powder. Subsamples of 8.0 mg were weighed and placed in tin capsules and analyzed with a Carbo Ebra CE NCS 2500 Elemental Analyzer to determine CHN concentrations.
The size and morphological complexity of giant kelp calls for several estimates to assess growth of kelp, including elongation rates of fronds and the total number of fronds per individual (Zimmerman and Robertson 1985, Edwards 2004), the increase in size of kelp blades (Littler and Littler 1985), the number of meristems, and the elongation of haptera. To evaluate the density of fronds as an indicator of growth, the difference in the number of fronds was determined on each experimental plot between the beginning and end of the experiment. The number of growing meristems also was counted at the end of the experiment as a measure of growth. To assess the growth of kelp blades, six blades were chosen randomly from three randomly selected giant kelp on each plot and from12 randomly selected giant kelp on the natural reef. On each blade, holes were punched 10 cm from the pneumatocyst (Littler and Littler 1985). At the end of the experiment, blades were collected and the difference in distance (mm) of the holes from their previous location relative to the pneumatocyst was recorded. The growth of haptera was examined by marking three newly growing haptera on each of three giant kelp with elastomer (Northwest Marine Technology), an inert colored substance injected 1 cm below the growing tip. Marked haptera were collected at the completion of the experiment, and the distance from the elastomer mark to the end of all subsequent branching haptera was recorded.
LITERATURE CITED
Edwards, M. S. 2004. Estimating scale-dependency in disturbance impacts: El Niños and giant kelp forests in the northeast Pacific. Oecologia 138:436–447.
Littler, M. M., and D. S. Littler. 1985. Ecological field methods Pages 461–478 Handbook of phycological methods: ecological field methods; macroalgae. Cambridge University Press, London, UK.
Zimmerman, R. C., and D. L. Robertson. 1985. Effects of El Niño on local hydrography and growth of the giant kelp Macrocystis pyrifera, at Santa Catalina Island, California. Limnology and Oceanography 30:1298–1302.