Density derived estimates of standing crop and net primary production in the giant kelp <Emphasis Type="Italic">Macrocystis pyrifera</Emphasis> |
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Authors: | Daniel Reed Andrew Rassweiler Katie Arkema |
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Institution: | (1) Marine Science Institute, University of California, Santa Barbara, CA 93106, USA;(2) Woods Institute for the Environment, Stanford University, Stanford, CA 94305, USA |
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Abstract: | Assemblages of macroalgae are believe to be among the most productive ecosystems in the world, yet difficulties in obtaining
direct estimates of biomass and primary production have led to few macroalgal data sets from which the consequences of long-term
change can be assessed. We evaluated the validity of using two easily measured population variables (frond density and plant
density) to estimate the more difficult to measure variables of standing crop and net primary production (NPP) in the giant
kelp Macrocystis pyrifera off southern California. Standing crop was much more strongly correlated to frond density than to plant density. Frond density data collected in summer
were particularly useful for estimating annual NPP, explaining nearly 80% of the variation in the NPP from year to year. Data
on frond densities also provided a relatively good estimate of seasonal NPP for the season that the data were collected. In
contrast, estimates of seasonal and annual NPP derived from plant density data were less reliable. These results indicate
that data on frond density collected at the proper time of year can make assessments of NPP by giant kelp more tractable.
They also suggest that other easily measured variables that are strongly correlated with standing crop, such as surface canopy
area, might serve as similarly useful proxies of NPP. |
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