Biochar and compost effects on mobility of Cu and other soil parameters and plant growth

A pot experiment was conducted to determine the effects of three biochars and compost on plant growth and the immobilisation of Cu in a contaminated soil obtained from a former wood preservation site in the Gironde County Saint Médard d'Eyrans, France (N 44° 43.353, W 0° 30.938). To assess Cu mobility, amended soils were analysed using CaCl**2 leaching tests pre- and post-incubation, and post-growth. Amended and unamended soils were planted with sunflower, and the resulting plant material was assessed for yield (mass and height) and Cu concentration. All amendments significantly reduced leachable Cu compared to the unamended soil, however, the greatest reductions in leachable Cu were associated with the higher biochar application rate. The greatest improvements in plant yields were obtained with the higher application rate of biochar in combination with compost. pH, DOC, EH were measured in soils to help explain the leaching and plant growth trends. Soil pore water was collected during plant growth and analysed for metal concentration, pH and EH. Prior to treatment, background analyses were carried out on the soil and individual amendments (including PAH + metal concentrations measured by gas chromatography mass spectrometry and ICP-AES respectively).

Stable isotope ratios measured on carbonate tests from the Kara Sea

River discharge of Ob and Yenisei to the Kara Sea is highly variable on seasonal and interannual time scales. River water dominates the shallow bottom water near the river mouths, making it warmer and less saline but seasonally and interannually more changeable than bottom water on the deeper shelf. This hydrographic pattern shows up in measurements and modelling, and in stable isotope records (delta18O, delta13C) along the growth axis of bivalve shells and in multiple analyses of single benthic foraminiferal shells. Average isotope ratios increase, but sample-internal variability decreases with water depth and distance from river mouths. However, isotope records of bivalves and foraminifera of a sediment core from a former submarine channel of Yenisei River reveal a different pattern. The retreat of the river mouth from this site due to early Holocene sea level rise led to increasing average isotope values up core, but not to the expected decrease of the in-sample isotope variability. Southward advection of cold saline water along the palaeo-river channel probably obscured the hydrographic variability during the early Holocene. Later, when sediment filled the channel, the hydrographic variability at the core location remained low, because the shallowing proceeded synchronously with the retreat of the river mouth.

Seawater carbonate chemistry and maximum growth rates of Skeletonema marinoi and Alexandrium ostenfeldii, toxin composition of Alexandrium ostenfeldii in a laboratory experiment

Phytoplankton populations can display high levels of genetic diversity that, when reflected by phenotypic variability, may stabilize a species response to environmental changes. We studied the effects of increased temperature and CO2 availability as predicted consequences of global change, on 16 genetically different isolates of the diatom Skeletonema marinoi from the Adriatic Sea and the Skagerrak (North Sea), and on eight strains of the PST (paralytic shellfish toxin)-producing dinoflagellate Alexandrium ostenfeldii from the Baltic Sea. Maximum growth rates were estimated in batch cultures of acclimated isolates grown for five to 10 generations in a factorial design at 20 and 24 °C, and present day and next century applied atmospheric pCO2, respectively. In both species, individual strains were affected in different ways by increased temperature and pCO2. The strongest response variability, buffering overall effects, was detected among Adriatic S. marinoi strains. Skagerrak strains showed a more uniform response, particularly to increased temperature, with an overall positive effect on growth. Increased temperature also caused a general growth stimulation in A. ostenfeldii, despite notable variability in strain-specific response patterns. Our data revealed a significant relationship between strain-specific growth rates and the impact of pCO2 on growth-slow growing cultures were generally positively affected, while fast growing cultures showed no or negative responses to increased pCO2. Toxin composition of A. ostenfeldii was consistently altered by elevated temperature and increased CO2 supply in the tested strains, resulting in overall promotion of saxitoxin production by both treatments. Our findings suggest that phenotypic variability within populations plays an important role in the adaptation of phytoplankton to changing environments, potentially attenuating short-term effects and forming the basis for selection. In particular, A. ostenfeldii blooms may expand and increase in toxicity under increased water temperature and atmospheric pCO2 conditions, with potentially severe consequences for the coastal ecosystem.

Impact of changing carbonate chemistry, temperature, and salinity on growth and test degradation of the benthic foraminifer Ammonia aomoriensis

The present study investigated the combined effects of ocean acidification, temperature, and salinity on growth and test degradation of Ammonia aomoriensis. This species is one of the dominant benthic foraminifera in near-coastal habitats of the southwestern Baltic Sea that can be particularly sensitive to changes in seawater carbonate chemistry. To assess potential responses to ocean acidification and climate change, we performed a fully crossed experiment involving three temperatures (8, 13, and 18°C), three salinities (15, 20, and 25) and four pCO2 levels (566, 1195, 2108, and 3843 µatm) for six weeks. Our results highlight a sensitive response of A. aomoriensis to undersaturated seawater with respect to calcite. The specimens continued to grow and increase their test diameter in treatments with pCO2 <1200 µatm, when Omega calc >1. Growth rates declined when pCO2 exceeded 1200 µatm (Omega calc <1). A significant reduction in test diameter and number of tests due to dissolution was observed below a critical Omega calc of 0.5. Elevated temperature (18°C) led to increased Omega calc, larger test diameter, and lower test degradation. Maximal growth was observed at 18°C. No significant relationship was observed between salinity and test growth. Lowered and undersaturated Omega calc, which results from increasing pCO2 in bottom waters, may cause a significant future decline of the population density of A. aomoriensis in its natural environment. At the same time, this effect might be partially compensated by temperature rise due to global warming.