Description: Zooplankton metabolic processes play an important role in carbon budgets and fluxes of pelagic ecosystems. Respiration rates of several copepod species were determined to reveal their energy requirements and assess their significance in the carbon cycle. Respiration rates were measured by optode respirometry and allometrically based on body dry mass (DM). For the on-board measurements, a 10-channel optode respirometer (PreSens Precision Sensing Oxy-10 Mini) was used and experiments were run in gas-tight glass bottles (13-14 ml) filled with filtered seawater to reduce bias by microbial respiration. In addition, respiration rates for all dominant copepod species during MSM80 including copepodite stages C4 to C6 were determined based on individual DM and respective ambient temperatures after Bode et al. (2018). For that, individual DM, if not available from frozen specimens, was determined from formalin/Steedman-preserved samples by weighing the dried samples on a microbalance. Losses in body DM due to formalin/Steedman preservation were considered after Schukat et al. (2021). Respiration rates were calculated separately for the copepod family Eucalanidae (a) as they are rather sluggish while all other copepods exhibited normal activity (b). (a) lnRTF = -2.180 + 0.787 ln(DM) + 0.131T and (b) lnRAC = -0.890 + 0.646 ln(DM) + 0.094T, where R (μl O2 ind-1 h-1) is the individual respiration rate for eucalanid (RTF) and active (RAC) copepods, DM represents dry mass in mg and T the average temperature (°C) of the sampling interval. Respiration rates of the medium- to larger-sized copepods (female prosome length (PL) of 1.2-6.0 mm) were compared to those of "small copepods" (all copepods with female PL 〈1.1 mm and young stages). Medium- to larger-sized species ingested on average 13-212 mg C m-2 d-1 in coastal regions while "small copepods" on average consumed 118-328 mg C m-2 d-1. The potential egestion varied on average from 5-64 mg C m-2 d-1 for medium to larger-sized copepods and 35-98 mg C m-2 d-1 for "small copepods". Data of energy demands, consumption and egestion rates of copepod species differing in size are essential to improve carbon budgets and food-web models in the Humboldt Current System.

Description: Small copepod genera play an important role in marine food webs and biogeochemical fluxes but have been neglected in many studies. Abundance, biomass and carbon consumption rates of small- (〈1 mm prosome length (PL)), medium- (1-1.5 mm PL) and large-sized (〉2 mm PL) copepods along a cross-shelf transect in the southern Benguela upwelling system were determined using rather high taxonomic resolution. Zooplankton samples were collected with a Multinet (Hydrobios Multinet midi, 5 nets with 200 µm meshsize) during the Meteor cruise M153 in February/March 2019. Calanoids contributed on average 55 ± 19% to total copepod abundance and 82 ± 13% to total copepod biomass. Small-sized Oithona spp. (119/114 mg C m-2 d-1) and Clauso-/Paracalanidae (87/263 mg C m-2 d-1) as well as large-sized Calanoides natalis (47/193 mg C m-2 d-1) were the dominant consumers at the most inshore stations. Small and medium-sized copepodite stages of Metridia lucens were also important, especially towards the continental slope. At offshore stations, Para-/Clausocalanidae (17-27 mg C m-2 d-1), Oithona spp. (9-16 mg C m-2 d-1), Pleuromamma spp. (0-16 mg C m-2 d-1), Calanus agulhensis (0-15 mg C m-2 d-1), Acartia spp. (0-12 mg C m-2 d-1), C. natalis (0-10 mg C m-2 d-1) and M. lucens (2-6 mg C m-2 d-1) were dominant consumers. Hence, usually small- and medium-sized copepods dominated total copepod ingestion, emphasizing that inadequate representation of small copepods will lead to significant underestimations and misinterpretations of the functioning of zooplankton communities, and finally to inadequate biogeochemical models.

Description: A combined stable isotope and fatty acid trophic biomarker approach was adopted for key zooplankton taxa and higher trophic positions of the northern Humboldt Current System to elucidate the pelagic food-web structure and to better understand trophic interactions. Samples covered an extensive spatial range from 8.5°S to 16°S and a vertical range down to 1,000 m depth. Immediately after each haul, specimens were sorted alive in the lab and apparently live and healthy individuals were stored in vials and deep-frozen at -80°C until further lipid and stable isotope analyses. The comprehensive data set covered over 20 zooplankton taxa and indicated that three biomass-rich crustacean species usually dominated the zooplankton community, i.e., the copepods Calanus chilensis at the surface and Eucalanus inermis in the pronounced oxygen minimum zone and the krill Euphausia mucronata, resulting in an overall low number of major trophic pathways toward anchovies. In addition, the semi-pelagic squat lobster Pleuroncodes monodon appears to play a key role in the benthic-pelagic coupling. By partly feeding on benthic resources and by diel vertical migration, P. monodon provides a unique pathway for returning carbon and energy from the sea floor to the epipelagic layer, increasing the food supply for pelagic fish.

Description: Abundance and community structure of calanoid copepods of one day (stn. 16; bottom depth 5,433 m) and one night station (stn. 15; bottom depth 5,462 m) were analyzed (Fig. 1). Stratified vertical hauls were carried out within 24 h with a HydroBios Multinet Maxi (0.5 m2 net opening, 9 nets, 150 µm mesh size) from 800 m depth to the surface (strata: 800-700-600-500-400-300-200-100-50-0 m). The filtered water volume was measured with a flowmeter attached to the net opening. After retrieval, samples were preserved in a 4% borax-buffered formaldehyde in seawater solution. Calanoid copepods were sorted according to their developmental stages (copepodids C1-3 and C4/5, adult females and males), counted and identified to genus or, if possible, to species level under a dissecting microscope (Leica MZ12). Rare species (〈100 individuals per sample) were counted from the entire sample. Total length (TL) of up to 100 calanoid individuals per taxonomic category (i.e. family/genus/species) and stage was measured (~6,600 specimens in total). Dry mass (DM) of calanoids was calculated based on the median TL of each taxonomic category. Individual respiration rates were calculated from individual DM and in situ temperatures, which were then converted to carbon units and used to calculate ingestion and egestion rates.

Description: This dataset shows abundance of zooplankton taxa in individuals per liter as determined by ZooScan. Each data point is one sampling day (date) in one mesocosm (MK). For details on experimental treatments and sampling, refer to Bach et al. 2021 (https://doi.org/10.5194/bg-17-4831-2020) and Ayon et al. 2022 (https://doi.org/10.5194/bg-2022-157). Raw images are stored in https://ecotaxa.obs-vlfr.fr/prj/3784. All taxonomic categories are self-explanatory.

Description: Males of the four crab species Percnon affine (H. Milne Edwards, 1853), Grapsus albolineatus (Latreille in Milbert, 1812), Orisarma intermedium (Schubart &Ng, 2020), and Geothelphusa albogilva (Shy, Ng & Yu, 1994), were collected in the southern part of Taiwan in May 2007. Individuals were starved for 12 days and midgut glands were dissected before and after the starvation period. Midgut glands were lyophilized and total lipids were extracted with dichloromethane:methanol (2:1 per volume) and an aqueous solution of 0.88% KCl. Extracted lipid mass was determined gravimetrically. Lipid classes were separated and quantified using Thin-Layer Chromatography with an integrated flame ionization detector (MK-5 TLC/FID analyzer, Iatron Laboratories). Lipids were converted to fatty acids methyl esters (FAME) by applying methanol containing 3% concentrated sulfuric acid. FAMEs were quantified by gas chromatography equipped with a DB-FFAP column, a programmable temperature vaporizer injector, and a flame ionization detector. Helium was used as carrier gas. Fatty acids were identified by retention times and by using fish oil standard (Marinol). Data are supplement to: Stumpp et al (2021) Dietary preferences of brachyuran crabs from Taiwan for marine or terrestrial food sources: evidence based on fatty acid trophic markers accepted for publication in Frontiers in Zoology

Description: Fatty acids were analyzed by gas chromatography using a DB-FFAP column of 30 m length and 0.25 mm inner diameter and a programmable temperature vaporizer injector. Following the trophic biomarker concept, the fatty acids 16:0, 20:5(n-3) and 22:6(n-3) were classified as typical components of biomembranes. High levels of 16:1(n−7) as well as 16:4(n−1) and 18:1(n−7) were used as diatom markers and 18:4(n−3) as fatty acid marker for dinoflagellates. The fatty acid 18:1(n-9) indicates carnivorous feeding. A carnivory index was applied based on the fatty acid ratio 18:1(n−9) / [16:1(n−7) + 16:4(n−1) + 18:1(n−7) + 18:4(n−3) + 18:1(n−9)] to reflect the proportion of carnivorous compared to herbivorous feeding in an organism. Fatty acid compositions of zooplankton and fish were taxon-specific and did not depend on sampling area or depth. Most species showed a dominance of typical membrane fatty acids, e.g., 16:0, 20:5(n-3) and 22:6(n-3). The dominant copepod Calanus chilensis had a low carnivory index and elevated amounts of diatom fatty acid markers which point to a predominantly herbivorous feeding. Among the krill species, Euphausia mucronata had the lowest carnivory index compared to the other euphausiids indicating a more herbivorous feeding. The squat lobster Pleuroncodes monodon had a significantly lower carnivory ratio compared to the deep-sea decapods Gennadas sp. and Acanthephyra sp. emphasizing its different trophic role compared to other decapods.