Motivation: Ecological stoichiometry investigates the equilibrium and the fluxes of chemical elements and energy between organisms and their environment. Several studies pointed out the value of integrating stoichiometric traits for a better understanding of the mechanisms behind community and ecosystem processes. Especially in the light of globally changing nutrient levels in freshwater systems, the link of stoichiometric traits to nutrient cycling and trophic interactions can improve our investigations of a species or community response to these changes. Benthic macroinvertebrate assemblages are widely used for biomonitoring in freshwaters, providing a large number of data sets gathering information about their taxonomic diversity at many different spatial and temporal scales. Likewise, an increasing number of large databases gives ready access to information on a variety of macroinvertebrate biological traits. The addition of stoichiometric traits to this pool of available information could thus expand the application of trait approaches and facilitate the study of the links between nutrient cycling and ecosystem functioning.
Main types of variables contained: The database contains information on elemental content of 188 taxa, in terms of the major nutrients %C, %N and %P and the corresponding molar ratios C:N, C:P and N:P. We provide calculated taxon mean values as well as the underlying raw data on individual level that was obtained from field sampling, supplemented by a literature research (n=1555, 174 taxa).
Major taxa and level of measurements: The database contains information on 188 macroinvertebrate taxa, available at species (n = 33), genus (96), tribe (9), subfamily (6), family (42), order (1) or class (1) levels.
Software format: .csv file

Data acquisition and compilation

The data originate mainly from field samplings we conducted with the aim of constructing a database of stoichiometric information for headwater macroinvertebrates (~64% of data presented in our database, n = 998). The sampling campaigns took place from May 2019 to January 2020 in small streams located in North-Eastern France and the Vosges mountains. We additionally integrated data from previous field campaigns done by our lab in the same region and similar stream types (~27%, n = 424) and data from the literature (~9%, n = 133). The literature research was not exhaustive and not filtered by sampling region, but tried to gather information on the most common macroinvertebrates in Western Europe. As a result, the stoichiometric information was gathered mainly from studies conducted within Western Europe, but sometimes completed by information from studies in the US.
For some taxa the provided values have been exclusively based on literature, but those values have only extended the number of taxa within groups (mainly family) we had already found in the field. Additionally, we graphically verified that literature values (and therewith also those from different regions) did not substantially increase the range of values associated to a given taxon.

The information was gathered at the finest taxonomic level of identification possible (mainly genus), or taken as provided by the literature. Data were included when at least information for one stoichiometric variable (%C, %N, %P, C:N, C:P, N:P) was available for one individual or taxon. Mass ratios were transformed to molar ratios if necessary.

Details on the sampling sites and the laboratory nutrient analyses are provided in the supplementary material of the corresponding data paper (Appendix S1+S2).

Data curation

The molar ratio values (C:N, C:P, N:P) were calculated for each individual from the corresponding elemental stoichiometric values. When measurements were done on a pool of individuals, they were treated like individuals in the following calculations.

To construct the stoichiometric database, the mean of elemental contents and ratios was calculated for each taxon and several coarser taxonomic levels, up to the family level (genus, sub-family, family). For a given taxonomic level (e.g. family) and a given stoichiometric variable, we averaged the information provided by all the individuals belonging to this taxonomic group, independently of their identification level. For example, if for a given family and a given stoichiometric variable, values were available for five individuals of a first genus and three individuals of a second genus, these eight values were averaged to provide the value of this family for this stoichiometric variable. If information was available for one genus (four individuals) and two species (three and four individuals), the family value was calculated as the mean of these eleven individuals. The geometric mean was used for all the stoichiometric variables, as suggested by Isles (2020).

Here we provide both the calculated mean values ("StoichioDB") as well as the underlying raw data ("StoichioDB_rawdata").

StoichioDB_rawdata
Taxon: Name of the taxon
%C: Carbon mass content (%)
%N: Nitrogen mass content (%)
%P: Phosphorous mass content (%)
C:N_molar: molar C:N ratio
C:P_molar: molar C:P ratio
N:P_molar: molar N:P ratio
Biomass: Dryweight per individual in mg (when available; when a pool of individuals has been analyzed, the overall weight has been divided by the number of individuals to obtain the individual weight). Note that values for Bivalvia and Gastropoda include the shell
Sample: Indicates wether the sample analysed was a pool of organisms or a single individual
Reference: Indicates whether the value was obtained from the literature giving the corresponding reference, or from fieldsampling

Class, Order, Family, Subfamily, Genus, Species: Indicates for each taxon the taxonomic group it belongs to

Stream: Stream/ site name
Long(E)/ Lat(N): Sampling site coordinates; when not available and value was not obtained from the literature, the sampling site was in the Vosges mountains (France).

StoichioDB
Taxon: Name of the taxon
%C: averaged carbon mass content (%), using the geometric mean
%N: averaged nitrogen mass content (%), using the geometric mean
%P: averaged phosphorous mass content (%), using the geometric mean
C:N_molar: averaged molar C:N ratio, using the geometric mean
C:P_molar: averaged molar C:P ratio, using the geometric mean
N:P_molar: averaged molar N:P ratio, using the geometric mean

sd_X: Standard deviation for each taxon and stoichiometric value, using the geometric standard deviation
range_X: Minimum and maximum value for each taxon and each stoichiometric variable
n_X: Sample size used in the calculation for each taxon and stoichiometric variable

Reference: Gives the reference when literature values were integrated in the calculation; the number in parentheses indicates the number of values from this source. Details of references can be found in the reference list of the data paper.
Class, Order, Family, Subfamily, Genus, Species: Indicates for each taxon the taxonomic group(s) it belongs to