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: Highlights: • Environmental conditions cause specific zooplankton life strategies. • No ontogenetic or diel vertical migration in the life cycle of Calanus chilensis. • Spatial expansion of Calanus chilensis secondary production far offshore. • Compacted surface biomass of Calanus chilensis allows easy foraging by anchovy. Abstract: Calanid copepods of the genera Calanus and Calanoides are key components of zooplankton communities in upwelling systems. Here, we compare the life-history traits of Calanus chilensis from the Humboldt Current Systems (HCS) off northern Peru and its counterpart Calanoides natalis from the northern Benguela Current System (BCS) off Namibia. A comprehensive data set of the distribution and abundance patterns of these species along extensive horizontal and vertical scales is presented. C. chilensis from the HCS was almost exclusively restricted to the surface layer (50–0 m) above the oxygen minimum zone (OMZ), whereas C. natalis from the BCS inhabited the entire water column down to 800 m performing ontogenetic vertical migration (OVM) through the OMZ. Resting stages of C. natalis at depth accumulated high amounts of lipid (30–60% of dry mass, DM), whereas C. chilensis did not rely on lipid reserves. These findings confirm that the life cycle of C. chilensis does not include OVM with diapause at depth. Surprisingly, the regional distribution of C. chilensis secondary production extended much further offshore (〉200 km from the coast) than is typical of other coastal upwelling systems. Deviating environmental conditions forced the two key calanid species to develop specific, but different life strategies for HCS and BCS. Compacted biomass concentrations of C. chilensis in the surface layer from the shelf (≤3 g DM m−2) to offshore waters (≤1.5 g DM m−2) facilitate easy and efficient foraging by predators such as juvenile Peruvian anchovies. In contrast, a large fraction of the C. natalis biomass occurs within the OMZ and is thus out of reach for hypoxia-sensitive predators. Calanoid copepods (e.g. C. chilensis) play a crucial role as important prey for growth and recruitment of small pelagic fish. Thus, the compacted biomass and high productivity of C. chilensis at the surface derived from its adaptive life-history traits (no OVM) may explain the superior trophic transfer efficiency and hence enormous fisheries yield of the HCS compared to the BCS.

Description: Background: Trophic interactions are key processes, which determine the ecological function and performance of organisms. Many decapod crustaceans feed on plant material as a source for essential nutrients, e.g. polyunsaturated fatty acids. Strictly herbivorous feeding appears only occasionally in marine decapods but is common in land crabs. To verify food preferences and to establish trophic markers, we studied the lipid and fatty acid composition of the midgut glands of two marine crab species (Grapsus albolineatus and Percnon affine), one semi-terrestrial species (Orisarma intermedium, formerly Sesarmops intermedius), and one terrestrial species (Geothelphusa albogilva) from Taiwan. Results: All species showed a wide span of total lipid levels ranging from 4 to 42% of the dry mass (%DM) in the marine P. affine and from 3 to 25%DM in the terrestrial G. albogilva. Triacylglycerols (TAG) were the major storage lipid compound. The fatty acids 16:0, 18:1(n-9), and 20:4(n-6) prevailed in all species. Essential fatty acids such as 20:4(n-6) originated from the diet. Terrestrial species also showed relatively high amounts of 18:2(n-6), which is a trophic marker for vascular plants. The fatty acid compositions of the four species allow to clearly distinguish between marine and terrestrial herbivorous feeding due to significantly different amounts of 16:0, 18:1(n-9), and 18:2(n-6). Conclusions: Based on the fatty acid composition, marine/terrestrial herbivory indices were defined and compared with regard to their resolution and differentiating capacity. These indices can help to reveal trophic preferences of unexplored species, particularly in habitats of border regions like mangrove intertidal flats and estuaries.

Description: Submesoscale structures, characterized by intense vertical and horizontal velocities, potentially play a crucial role in oceanographic dynamics and pelagic fluxes. Due to their small spatial scale and short temporal persistence, conditions for in situ measurements are challenging and thus the role of such structures for zooplankton distribution is still unclear. During RV Polarstern expedition PS107 to Arctic Fram Strait in July/August 2017, a submesoscale filament was detected, which initiated an ad hoc oceanographic and biological sampling campaign. To determine zooplankton taxonomic composition, horizontal and vertical distribution, abundance and biomass, vertical MultiNet hauls (depth intervals: 300–200–100–50–10–0 m) were taken at four stations across the filament. Zooplankton data were evaluated in context with the physical-oceanographic observations of the filament to assess submesoscale physical-biological interactions. Our data show that submesoscale features considerably impact zooplankton dynamics. While structuring the pelagial with distinct zooplankton communities in a vertical as well as horizontal dimension, they accumulate abundance and biomass of epipelagic species at the site of convergence. Further, high-velocity jets associated with such dynamics are possibly of major importance for species allocation and biological connectivity, accelerating for instance processes such as the ‘Atlantification’ of the Arctic. Thus, submesoscale features affect the surrounding ecosystem in multiple ways with consequences for higher trophic levels and biogeochemical cycles.

Description: Macrozooplankton and its grazing pressure shape ecosystem structures and carbon pathways in the Southern Ocean. Here, we present the implementation of “polar macrozooplankton” as a plankton functional type and a related fast-sinking detritus class (fecal pellets) into the biogeochemical model REcoM-2. We use the model to assess major carbon pathways and ecosystem structure in the Southern Ocean south of 50°S. The model represents zooplankton biomass and its spatial distribution in the Southern Ocean reasonably well in comparison to available biomass data. A distinct difference of our model from previous versions is the seasonal pattern of particle formation processes and ecosystem structures in the Southern Ocean. REcoM-2 now captures high zooplankton biomass and a typical shift from a dominance of phytodetrital aggregates in spring to zooplankton fecal pellets later in the year. At sites with high biomass of macrozooplankton, the transfer efficiency of particulate organic carbon can be as high as 50%, and the carbon content of the exported material increases. In our simulations, macrozooplankton is an important component of the Southern Ocean plankton community, contributing up to 0.12 Pg C per year (14%) to total modeled carbon export across 100 m depth. Macrozooplankton changes the phytoplankton composition and supports the recycling of macronutrients. These results support the important role of macrozooplankton such as krill in the Southern Ocean and have implications for the representation of Southern Ocean biogeochemical cycles in models.