Phytoplankton carrying capacity: Is this a viable concept for coastal seas?

Carrying capacity estimations for any population of organisms is made in order to determine the maximum population densities that could result under set environmental conditions. Carrying capacity ( K ) is often used in terrestrial ecosystems to estimate potential plant densities (yields) related to the availability of resources. Here we wanted to see whether a similar concept could be applied to the plants of the ocean: Phytoplankton. Using the Helgoland Roads Time Series data sets, the main focus was on those which control phytoplankton growth in the ocean. We aimed to estimate K and determine whether K is static or variable, evaluated the relationship of phytoplankton K with higher trophic levels. We also provided a guideline to use K as ecosystem management tool. Algorithms were developed to estimate the K based on each controlling factor. A pair-wise comparison matrix was used for weighting the controlling factors and then to integrate the estimated K based on controlling factors to obtain an overall K . Long-term intra-annual and inter-annual mean K were estimated 10.13 × 10 7 cells m −3 and 1.30 × 10 8 cells m −3 , respectively. Our analyses suggest that K should not be considered as a static permanent value. This is because it is driven by overall environmental conditions and is subject to change when overall environment change. We linked the estimated K to pelagic fisheries data of the North Sea and found that phytoplankton K is correlated with the pelagic fisheries of this area. Our overall conclusion is that phytoplankton K is a viable concept and could be utilized as a valuable management tool. [ABSTRACT FROM AUTHOR]