Information on the energy density of prey is critical for estimating food requirements and consumption by predators and modelling energy flux through food webs (Van de Putte et al., 2006). We compiled energy density values for 121 marine species or genera from 12 published sources. The dataset encompasses 71 benthic and pelagic fish, 29 crustaceans, 15 cephalopods, 2 elasmobranchs, 2 jelly fish and 1 salp, sampled in the central and Northeast Atlantic and in the Mediterranean Sea between 1992 and 2017. Data were collected from studies that measured energy density directly by bomb calorimetry, and those studies that measured the proximate composition (i.e. the percentage of proteins, lipids and carbohydrates) of sampled tissues and converted these percentages into energy using combustion equivalents reported in the literature. When available, we reported energy density (or mean density, for samples with more than one individual) as a function of dry and wet weight, and the moisture percentage of samples. For each data record, we also provided the sampling location, geographic coordinates, month and year of sample collection, method of sample collection, taxonomic ranks (phylum, class, order, family), number and size (or size range) of sampled organisms, as well as the reference and DOI of the original data source, for further details on the samples analysed and/or the analytical techniques used.
Bulk stable isotope ratios, primarily of carbon (δ13C) and nitrogen (δ15N), are increasingly used to examine predator-prey interactions and food web structure. We compiled δ13C and δ15N values of marine taxa from 56 published sources to support investigations on trophic interactions in mesopelagic food webs and assess the importance of mesopelagic organisms in the marine ecosystem. A total of 2095 records were collected, representing 8716 individual organisms from 349 unique species or genera sampled across the central and Northeast Atlantic, and the Mediterranean Sea, between 1905 and 2020. Records include 185 benthic and pelagic fish, 47 cephalopods, 31 marine mammals, 30 crustaceans, 26 elasmobranchs, 16 seabirds, 4 marine turtles, 4 jelly fish, 3 copepods, 2 salps, in addition to data from several organisms only identified to higher taxonomic ranks (family or above). The dataset includes isotopic ratios measured in the tissues or in the whole body of individual organisms, or mean values (and standard deviations) from pooled samples. Because lipids have more negative δ13C values relative to other major biochemical compounds in plant and animal tissues (DeNiro & Epstein, 1977), many studies correct for the lipid effect by extracting lipids from samples before analysis, or a posteriori, through mathematical corrections (Post, 2002). Therefore, δ13C values were reported as uncorrected, lipid-extracted, or mathematically-corrected. When available, the total organic carbon to nitrogen ratio (C:N) was included. For each data record, we also provided the sampling location, geographic coordinates, month and year of sample collection, method of sample collection, taxonomic ranks (phylum, class, order, family), number and size (or size range) of sampled organisms, as well as the reference and DOI of the original data source, for further details on the samples analysed and/or the analytical techniques used.
Fractional trophic levels (i.e., trophic positions) describe the position of organisms within food webs and help define their functional roles in ecosystems (Odum & Heald, 1975). Trophic positions are thus critical for characterizing species' diets and energy pathways, investigating food web dynamics and ecosystem functioning, and assessing ecosystem health and resilience (Pauly et al., 1998; Pauly & Watson, 2005; Vander Zanden & Fetzer, 2007). We compiled estimates of trophic positions of marine organisms sampled across North Atlantic and Mediterranean waters between 1974 and 2015, gathered from 33 published and unpublished sources. The dataset comprises 208 unique species or genera, including zooplankton, decapods, cephalopods, pelagic and benthic fish, elasmobranchs, marine mammals, marine turtles, seabirds, as well as detritus. Estimates of trophic position were based on the analyses of stomach contents, bulk nitrogen stable isotopes (δ15N values), or amino acid compound-specific nitrogen isotopic analysis. For each data record, we also provided the sampling location, geographic coordinates, month and year of sample collection, method of sample collection, taxonomic ranks (phylum, class, order, family), number and size (or size range) of sampled organisms, type of analyses and estimation method, as well as the reference and DOI of the original data source, for further details on the samples analysed and/or the analytical techniques used.
Ecosystem models often use wet weights to parameterise biota disregarding their water content. This may be especially erroneous for gelatinous plankton, such as salps and pyrosomes, with high, compared to crustaceans, water content. Poorly quantified residual water should also be corrected when using dry weights for parameterisation. We estimated the residual water content (as well as elemental and organic contents) for seven tunicate species, one pyrosome and six salps (N = 107). Specimens were collected during several research expeditions in the Southern Ocean, the Northeast Pacific, east of New Zealand, and around Hawaii between 2004 and 2021. The residual water content of tunicates was analyzed for inter- and intraspecific variability. The H-surplus method (Madin et al. 1981) was applied for the residual water content calculation. The dataset contains information about the life cycle stage (blastozooid versus oozooid), tissue type (tunic versus whole organism), drying method (oven versus freeze-drying), size, and the elemental and organic contents of the samples. The methods and results of the study are described in detail in Lüskow et al. (submitted).