A guide to the currently available network data
Ursula M. Scharler

     As you already know by now, there are several network data files on the ftp site under 4_Networks. These files are what we have produced thus far in terms of building Twin Cays specific networks (that the networks are not nearly as Twin Cays specific as we would like them to be, you also already know).
What are all these files about? In general, the files describe the data used to build the networks. They say how they were calculated, and they contain the input data for the network analysis.

To begin...

The information in file TCNetworkDec2002.xls are from the literature and your unpublished data. Here you will find the biomass, consumption (GPP for primary producers), production, egestion, respiration and decay rates (for the non-living compartments) in terms of carbon and nitrogen. The information is there for the fringe, transition and dwarf zones.
     This file also contains several metabolic ratios, and flows from and to the surroundings of Twin Cays (atmosphere, sea). The diet composition of each compartment (who eats whom?) was partly based on the literature and partly on the isotope data of Marilyn’s group. Currently there are 49 compartments for the three carbon networks and 50 for the three nitrogen networks.

How did we calculate these data?

Check out the Word files FringeC.doc, FringeN.doc, TransitionC.doc, etc…, there are 6 files, one for each network. It is way to complicated to tell you all of it again here, but these docs should be understandable.

How do we make a network out of all these data?

Some building blocks are in that file, TCNetworkDec2002.xls – these are the biomass, consumption, respiration, imports and exports and information on ‘who eats whom’. All the nitty gritty data are listed in 6 Excel files (again one for each network) called Fringe-C.xls, Fringe-N.xls, Transition-C.xls, etc….
     To be able to get the last piece in the puzzle of input data for the network analysis, the information on ‘who eats whom’ needed to be supplemented with ‘by how much’. Never despairing about a lack of data, Bob wrote a program which calculates the ‘by how much’ based on information on biomass, the topology of ‘who eats whom’, how much a compartment demands (consumes), and the availability of its food items. The flows magnitudes are partitioned in as functions of both supplies and demands.
     The results from Bob’s magical program are given in t-c-nets.xls for all 6 networks. These are also, finally, the input data for the network analysis.

     OK, so now, the file is read as follows – first you see an exchange matrix, which states how much food (in terms of carbon or nitrogen) is exchanged between the compartments (who eats whom and by how much). C or N flows from row (i) to column (j), e.g. in Fringe-C there are 1.00E-01 gC/m2/y flowing from Macroalgae (#7) to Fish (#26). Below the exchange matrix the imports from outside Twin Cays and the biomass of all compartments are listed. To the right of the exchange matrix the exports from Twin Cays and the respiration are listed. All the information on consumption, production, egestion and diet composition which we had in our first file TCNetworksDec2002.xls are incorporated in the exchange matrix. All data are expressed as gC (or N) per area (biomass) and as gC (or N) per area per year (all other). The file xls-fmt.doc contains a description of the format.

I know that this is a lot of files, but your brain shouldn't be full yet. Keep reading.

What use are these files to you?

You can get information on all the items I've talked about so far, specifically for the fringe, transition and dwarf zones of Twin Cays. These data are readily available for your use. You can trace (and check!) what we did with your data. Once we have meaningful results of Twin Cays specific networks, they will also be made available to you. These will contain data on all direct and indirect effects any one compartment has on another, on the trophic structure, the cycling of material, on the overall organizational and developmental status of the 3 zones and traces the nutrient limitation right through the networks (i.e. what compartment is limited by what nutrient).

How can you help us improve the dataset?

Please, look at what we have done! Since you are our most important source of data, your data contribution will make the networks. You can also help in checking the data from other compartments, particularly those you are familiar with. If any guesses we make are hopelessly out of bound, or any numbers are calculated the wrong way, please tell us.

Where are the data gaps?

Basically everywhere. You can check out the file Assign.xls on the ftp site under 3_Foodweb Data, which gives an estimate of how much data presently incorporated into the networks are Twin Cays specific. This file also assigns your name (yes, you) to specific compartments for which you can provide data. This list was drawn up, by you, during the last All Hands meeting.
     The results of the network analyses on the 6 networks described above are, however, at the moment not on the ftp site. Not that we don't want you to see them, but they aren't. If you want to know about them, or more about the methods, just send an email. You can also visit our website for more info (Twin Cays Network Analysis).