engleski

Recovery of photosynthesis parameters from in situ profiles of primary production

In order to quantify primary production in models, information on the production light relationships is required. This information typically comes in the form of photosynthesis parameters, which are routinely estimated from in vitro experiments under controlled light conditions and as such are used in models. Complementary to this approach is the in situ approach, where production is measured under natural light conditions in the sea, yielding the production profile. In standard oceanographic practice in situ data are used to estimate daily watercolumn production, whereas in vitro data are used to recover the parameters and to calculate watercolumn production. Here, we follow a different approach and use in situ data to recover the photosynthesis parameters and subsequently calculate watercolumn production with the extracted parameters. To accomplish this goal an inverse model is implemented, which optimizes a model for the production profile to match the in situ measurements as close as possible. An analytical solution for the production profile is derived to serve as a model for the production profile. Limitations of the model are discussed and expressed mathematically. It is demonstrated that each production profile is uniquely determined by a set of photosynthesis parameters, contrary to daily watercolumn production, which does not share this property. The inverse model is further tested with data from the Hawaii Ocean Time-series. The model explained 97.88% of variance in measured normalized production at depth and 99.21% of variance in measured watercolumn production. As a result an archive of photosynthesis parameters for this region of the ocean is established and seasonal cycles of parameters estimated. The results are put in a remote sensing context and a demonstration of primary production calculation is carried out for the Hawaii region.

photosynthesis irradiance functions ; photosynthesis parameters ; primary production ;

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