This dataset includes carbon fluxes computed by postprocessing nitrogen outputs from StrathE2E model runs, by taking into account carbon-nitrogen stoichiometry dynamics in the food web.

This dataset was compiled for deliverable 5.2 of the Ocean-ICU Horizon Europe project.

Version 1.1 updates:

• The algorithm had minor errors which were fixed.
• Quality improved observational data used for fitting and optimising parameter q.

StrathE2E model runs

The StrathE2E model is an end-to-end ecosystem model, describing the entire food web within shelf regions, from inorganic nutrients to megafauna (Heath et al, 2021). It uses climate model outputs, and combined with a fishing fleet model, StrathE2E allows for the study of both climate and fishing effects on nutrient cycling and trophic interactions.

Data were computed from running the following StrathE2E model variants and fishing scenarios:

Dataset description

Overview

For each model variant and fishing scenario tested, the following data (in .csv format) are available:

• Carbon budget data ("#_Cbudget-data.csv")
• Matrices of annual carbon and nitrogen fluxes for whole area (inshore and offshore zones combined) from last year model outputs ("#_C-fluxes.csv" and "#_N-fluxes.csv")
• Landings by guild (e.g. planktivorous fish, pelagic invertebrates, benthos, birds...) and by gear (e.g. beam trawls, dredges...) in carbon and nitrogen units ("#_C-land-by-gear.csv" and "#_N-land-by-gear.csv")

In addition, the "CN-ratios_all-model-variants.csv" file compiles all resulting C:N ratios of each guild for each model run performed here.

Carbon budget data

This contains a summary of the following boundary and internal (production) fluxes which are of interest for the deliverable 5.2 of the Ocean-ICU project:

• Carbon sequestration (net sediment burial)
• Landings
• Discards
• Corpses (note that discards end up in this guild after a short life time (see flux matrices))
• Faecal pellets
• CO2 absorption by food web guilds
• CO2 release by food web guilds
• Beach cast of macrophytes (kelp)
• Passive inflow of organic carbon (from phytoplankton and detritus) from open ocean
• Passive outflow of organic carbon (from phytoplankton and detritus) from open ocean
• Fish migration inflow
• Fish migration outflow

For each variable, both the total annual flux and flux by guild are given.

Matrices of annual carbon and nitrogen fluxes

Each column represent the destination/consumer guild and each row the source/prey guild.

Example: the value read in row "carnzoo" (carnivorous zooplankton) and column "pfish" (planktivorous fish) is the annual flux of consumption of carnivorous zooplankton by planktivorous fish.

These matrices include boundary fluxes (e.g. open ocean, atmosphere...).

Fluxes are given in mmol.m^(-2).y^(-1) of either carbon or nitrogen.

Landings by guild and by gear

Units: mmol.m^(-2).y^(-1) of carbon/nitrogen

Fishing gears:

• artisanal
• beam trawls
• dredges
• driftings and handlines
• fly dragging and anchor seine
• gillnets and longlines
• kelp harvesting
• mid-water trawl
• nephrops trawls
• pots
• purse seine.

Guilds harvested:

• Planktivorous fish
• Quota-limited demersal fish
• Non-quota demersal fish
• Migratory fish
• Suspension/deposit feeding benthos
• Carnivore/scavenge feeding benthos
• Pelagic invertebrates
• Birds
• Pinnipeds
• Cetaceans
• Macrophytes

C:N ratios

Table compiling C:N molar ratios by guild for each model variant.

Note: These C:N ratios are the result of a nitrogen-to-carbon conversion which describes the transfer of carbon up the food web by using one parameter (q). This parameter was fitted to compiled observational C:N ratio data using outputs from the baseline model (so one parameter value for model variant with CNRM climate input and one for model with GFDL). Once fitted, this parameter value was kept constant for all other model runs.

Funding acknowedgement

This work was co-funded by the European Union under grant agreement no. 101083922 (OceanICU) and UK Research and Innovation (UKRI) under the UK government’s Horizon Europe funding guarantee [grant number 10054454, 10063673, 10064020, 10059241, 10079684, 10059012, 10048179]. The views, opinions and practices used to produce this dataset are however those of the author(s) only and do not necessarily reflect those of the European Union or European Research Executive Agency. Neither the European Union nor the granting authority can be held responsible for them.