Description: Lithogenic material deposited as dust is one of the major sources of trace metals to the ocean, particularly in the tropical and subtropical Atlantic. On the other hand, it can also act as a scavenging surface for iron. Here we studied this double role of lithogenic material in the marine iron cycle by adding a new scheme for describing particle dynamics into a global biogeochemistry and ecosystem model including particle aggregation and disaggregation of two particle size classes as well as scavenging on both organic and lithogenic particles. Considering the additional scavenging of iron on lithogenic particles, the modelled dissolved iron concentration is reduced significantly in the tropical and subtropical Atlantic, bringing the model much closer to observations. This underlines the necessity to consider the double role of dust particles as iron source and sink in studies on the marine iron cycle in high dust regions and with changing dust fluxes.

Description: The global marine iron cycle has been modeled using REcoM2 (Regulated Ecosystem Model 2) coupled with the ocean circulation model MITgcm (MIT General Circulation Model). A general description of the model can be found in the supporting material for Hauck et al. 2013. In the simulations producing this data set, the organic complexation of iron was made dependent on seawater pH and concentration of dissolved organic matter. With this parameterization, the effect of pH change on the iron cycle and the biological feedback to the iron cycle have been examined through the pathway of ligand binding. In this data set, model output of dissolved iron (DFe), dissolved organic carbon (DOC), stability constants of ligands, free Fe concentration and net primary production (NPP) are included. Four different simulations are considered: R_std (standard), R_constL (with constant 1 nM ligand concentration), R_progL (with one prognostic ligand) and R_ph (with future pH field).

Description: Acidification (OA), a global threat to the world's oceans, is projected to significantly grow if CO2 continues to be emitted into the atmosphere at high levels. This will result in a slight decrease in pH. Since the latter is a logarithmic scale of acidity, the higher acidic seawater is expected to have a tremendous impact on marine living resources in the long-term. An 8-week laboratory experiment was designed to assess the impact of the projected pH in 2100 and beyond on fish survival, health, growth, and fish meat quality. Two projected scenarios were simulated with the control treatment, in triplicates. The control treatment had a pH of 8.10, corresponding to a pCO2 of 321.37 ± 11.48 µatm. The two projected scenarios, named Predict_A and Predict_B, had pH values of 7.80-pCO2 = 749.12 ± 27.03 and 7.40-pCO2 = 321.37 ± 11.48 µatm, respectively. The experiment was preceded by 2 weeks of acclimation. After the acclimation, 20 juvenile black sea breams (Acanthopagrus schlegelii) of 2.72 ± 0.01 g were used per tank. This species has been selected mainly due to its very high resistance to diseases and environmental changes, assuming that a weaker fish resistance will also be susceptibly affected. In all tanks, the fish were fed with the same commercial diet. The seawater's physicochemical parameters were measured daily. Fish samples were subjected to physiological, histological, and biochemical analyses. Fish growth, feeding efficiency, protein efficiency ratio, and crude protein content were significantly decreased with a lower pH. Scanning electron microscopy revealed multiple atrophies of microvilli throughout the small intestine's brush border in samples from Predict_A and Predict_B. This significantly reduced nutrient absorption, resulting in significantly lower feed efficiency, lower fish growth, and lower meat quality. As a result of an elevated pCO2 in seawater, the fish eat more than normal but grow less than normal. Liver observation showed blood congestion, hemorrhage, necrosis, vacuolation of hepatocytes, and an increased number of Kupffer cells, which characterize liver damage. Transmission electron microscopy revealed an elongated and angular shape of the mitochondrion in the liver cell, with an abundance of peroxisomes, symptomatic of metabolic acidosis.

Description: In this study, we used MITgcm-REcoM2 to simulate the stepwise glacial-interglacial atmospheric pCO2 change. A general description of the model can be found in the supporting material for Hauck et al. 2013. There are seven simulations included in this dataset: two control runs for interglacial and glacial conditions (IG_ctl, G_ctl); three region-specific sensitivity runs(IG_Gso, IG_Gna, IG_Gns); and two simulations regarding the glacial iron fertilization in the Southern Ocean. Dissolved Inorganic Carbon (DIC) and Export Production in all runs are included in this study, and the potential temperature (THETA), salinity (SALT), meridional velocity (VVEL), sea ice concentration(SIarea), air-sea surface pCO2 (dpCO2surface) difference are available in IG_ctl, IG_Gso, IG_Gna, IG_Gns, and G_ctl.