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Project: P-REDUCE - Consequences of phosphorus reduction for the dynamic transfer of organic matter

Project details

Acronym : P-REDUCE
Full project name : Consequences of phosphorus reduction for the dynamic transfer of organic matter
Initiating organisation : NIOZ Royal Netherlands Institute for Sea Research, Texel
Project leader : J.C. Kromkamp
Supporting organisation(s)NIOZ Royal Netherlands Institute for Sea Research, Texel
Financing : nwo
Project number : 83908340
Start date : Jan 01, 2009
End date : Dec 31, 2013


Programme :ZKO - Carrying Capacity: Line 3 - National Programme Sea and Coastal Research (ZKO) - Carrying Capacity: Line 3 - Hypothesis-driven Research
Main project :-


Description :

Primary production by both phytoplankton and microphytobenthos are key processes determining the carrying capacity of the Wadden Sea ecosystem. Our main aims are to investigate how bottom up processes regulate primary production of functional groups of phytoplankton and microphytobenthos, and how the structure of functional groups of primary producers is shaped as a result of the different resource demands.
The work proposed here specifically focuses on P as a factor limiting benthic and pelagic primary production in the western and central Wadden Sea, controlling the relative importance of pelagic versus benthic primary production and the species composition of the phototrophic communities. The implications of this compositional selection in structuring the food web and carrying capacity of the Wadden Sea will be addressed by defining the transfer of carbon to various development stages of selected benthic primary consumers. New views on the functioning of the lower food web are to be conceptualized in a biogeochemical model and provide essential information on the direction and magnitude of change in Wadden Sea carrying capacity as a result of management policies or global change.
The overall hypothesis to be tested is that the availability of the pelagic and benthic primary producers as a food source and the food demand of their primary consumers is changing due to a decrease in P-loading, altering the structure of the food web and decreasing the potential carrying capacity.
Group specific primary production will be measured by stable isotope labelling (measuring the rate of incorporation of 13C into phospho-lipid fatty acids using GC-IRMS). Bulk Primary production is measured using variable fluorescence techniques (FRRF and PAM for phytoplankton and microphytobenthos resp.) and is combined with the sampling campaigns carried out for the ZKO Line2 monitoring program "IN PLACE". We have chosen these latter techniques because they are the only techniques currently available which can be adapted for automated monitoring of primary productivity and which are consequently installed on the automated monitoring stations (the NIOZ Jetty), but calibration against standard C-fixation or oxygen production techniques is required. The stable isotope labelling of the different algal groups will give inside about their food quality. In combination with grazing experiments we will determine how the food quality influences the development of juvenile benthic bivalve larvae and how they in return influence the composition of the algal community by selective grazing.
Apart from light, nutrients are another major factor determining the rate of primary production. We will investigate phosphate as limiting factors by looking at proxies (nutrient concentrations and ratios), physiological parameters and perform bioassays. Commercially available molecular fluorescent probes (ELF 97) will be used to detect the induction of alkaline phosphatase, a potential indicator of P-limitation.
The sediments are potentially an important source as well as sink for nutrients, and this will be investigated as well, in combination with the effect that the presence of microphytobenthos has on the sediment water exchange of nutrients. This data will be used to develop and validate a dynamic biogeochemical sediment-water exchange model. This model can serve as submodel in an overall ecosystem model for the Wadden Sea.
3 PhD-students will carry out the day to day work, but will be part of a team in which also members sit who will coordinate or participate in other projects. This is to ensure efficient use of the data and to coordinate measuring and sampling efforts.
In this way we provide essential knowledge about the forces structuring the carrying capacity of the Wadden Sea, necessary for interpreting the data obtained by the automated monitoring platforms (Line 2 of the ZKO start program) and give important spatial information which facilitates extrapolation and evaluation of the monitoring platform data to larger spatial scales. We expect that this program not only generates important scientific knowledge but also generates important results for adequate management of the Wadden Sea. For this reason we will produce a yearly letter targeted to ecosystem managers and environmental organizations describing our results and their consequence for understanding and management of the Wadden Sea.