Mesocosm Experiment

Below is a brief description of the mesocosm experiments (shown at left) that were used for the data assimilation modeling.

In order to examine how marine food web communities process and use dissolved organic matter (DOM), a mesocosm experiment was conducted in Woods Hole, MA, USA in which 7 m3 seawater enclosures were augmented with combinations of dissolved inorganic nitrogen (DIN) and DOM. The enclosures were polyethylene bags equipped with flotation collars and structural hoops, which were deployed in Great Harbor. The DOM in these experiments was prepared by leaching leaf litter in seawater. The mesocosm experiment consisted of four treatments: Bag A, control (no additions); Bag B, one-time addition of DOM at the start of the experiment resulting in an increase of 300 uM DOC (dissolved organic carbon); Bag C, daily additions of nitrate, phosphate, and silica equivalent to 5 uM N, 0.5 uM P, and 7 uM Si, respectively; Bag D, treatments B and C combined. All treatments also received NaH13CO3 as a C-tracer.

The experiment was conducted outdoors under ambient lighting from 10 Sep. to 30 Sep. 1994. The measurements used for data assimilation involve: dissolved organic carbon (DOC, uM C); particulate organic carbon (POC, uM C); particulate organic nitrogen (PON, uM N); dissolved inorganic nitrogen (DIN, uM N); chlorophyll a (ug l-1); net primary productivity at a specified depth (NPP, uM C d-1); bacterial productivity (BP, uM C d-1); light extinction coefficient (K, m-1). Measurements were taken daily or every other day. The raw data is given below:

Note, all time is in days and begins at midnight, 10 Sep 94.

Drivers: PAR data, PP Incubation depths, Temperature data

Data assimilated: Bag A, Bag B, Bag C, Bag D

Other Data: Dissolved Oxygen, pH, NH4 and NO3

The data given above is not the complete set. In particular, we also measured 13C in DIC and various size fractions of POC, including small (~1-2 cm) Menidia menida that were added to the bags. Populations of bacteria, nanoflagellates, and various species of phyto- and zooplankton were also measured. This data can be made available on request.

The primary purpose of this page is to provide data to others that are involved in developing data assimilation techniques for marine food webs. With this goal in mind, investigators are encouraged to used Bag D for initial model development/tuning, then use data from Bags A, B and/or C to test model performance as was done in the JMR manuscript.