Differences in Carbon Acquisition Could Explain Adaptive Responses in a Baltic Sea Pico-Phytoplankton

Pico-phytoplankton have ample scope to react to environmental change. Nevertheless, we know little about the underlying physiological mechanisms that govern how evolutionary history may affect short-term responses to environmental change. We investigated growth rates and carbon uptake related traits at 15° and 22°C and at different times during the microbial growth curve (lag phase, mid and late exponential) of eight novel strains of Ostreococcus sp. (ca. 1 μm). The strains were isolated from two distinct regions of the Baltic Sea differing in salinity and temperature as well as variability therein from North-East (Bornholm Basin) to South-West (Kiel area). Strains from Kiel area had ca. 10% higher growth rates on average and showed more variation between strains compared to strains from the Bornholm Basin. While biomass increased throughout the experiment in both temperature, CUE (carbon use efficiency, indicative of photosynthetically derived carbon available for growth) was too low to explain positive growth throughout the entire growth curve at 15°C and during the early stages at 22°C. Throughout the growth curve CUE then increased enough to sustain growth, but only at 22°C. Consequently, we then tested whether Ostreococcus use organic carbon to supplement growth when light is not a limiting factor. We show that Ostreococcus qualitatively modulate their potential to grow on organic carbon sources throughout a single growth curve. Based on the differences between CUE and a potential to grow on organic carbon, we postulate a shift in carbon acquisition between inorganic and organic sources in Ostreococcus sp. with potential implications on ecological dynamics within microbial communities.

Holocene Spatiotemporal Redox Variations in the Southern Baltic Sea

Low oxygen conditions in the modern Baltic Sea are exacerbated by human activities; however, anoxic conditions also prevailed naturally over the Holocene. Few studies have characterized the specific paleoredox conditions (manganous, ferruginous, euxinic) and their frequency in southern Baltic sub-basins during these ancient events. Here, we apply a suite of isotope systems (Fe, Mo, S) and associated elemental proxies (e.g., Fe speciation, Mn) to specifically define water column redox regimes through the Baltic Holocene in a sill-proximal to sill-distal transect (Lille Belt, Bornholm Basin, Landsort Deep) using samples collected during the Integrated Ocean Drilling Program Expedition 347. At the sill-proximal Lille Belt, there is evidence for anoxic manganous/ferruginous conditions for most of the cored interval following the transition from the Ancylus Lake to Littorina Sea but with no clear excursion to more reducing or euxinic conditions associated with the Holocene Thermal Maximum (HTM) or Medieval Climate Anomaly (MCA) events. At the sill-distal southern sub-basin, Bornholm Basin, a combination of Fe speciation, pore water Fe, and solid phase Mo concentration and isotope data point to manganous/ferruginous conditions during the Ancylus Lake-to-Littorina Sea transition and HTM but with only brief excursions to intermittently or weakly euxinic conditions during this interval. At the western Baltic Proper sub-basin, Landsort Deep, new Fe and S isotope data bolster previous Mo isotope records and Fe speciation evidence for two distinct anoxic periods but also suggest that sulfide accumulation beyond transient levels was largely restricted to the sediment-water interface. Ultimately, the combined data from all three locations indicate that Fe enrichments typically indicative of euxinia may be best explained by Fe deposition as oxides following events likely analogous to the periodic incursions of oxygenated North Sea waters observed today, with subsequent pyrite formation in sulfidic pore waters. Additionally, the Mo isotope data from multiple Baltic Sea southern basins argue against restricted and widespread euxinic conditions, as has been demonstrated in the Baltic Proper and Bothnian Sea during the HTM or MCA. Instead, similar to today, each past Baltic anoxic event is characterized by redox conditions that become progressively more reducing with increasing distance from the sill.

Carbon acquisition in a Baltic pico-phytoplankton species - Where does the carbon for growth come from?

Summary- Pico-phytoplankton have ample scope to react to environmental change. But we know little about the underlying physiological mechanisms that govern how evolutionary history may affect short-term responses to environmental change.- We investigated growth rates and carbon uptake related traits (i.e. fitness proxies) in different temperatures and at different times during the microbial growth curve of eight novel strains of Ostreococcus sp. (ca. 1-2µm). The strains were isolated from two distinct regions of the Baltic Sea differing in salinity and temperature from North-East (Bornholm Basin) to South-West (Kiel area).- Strains from the warmer, more variable Kiel area had higher growth rates in general and showed more variable growth rates compared to strains from the colder and less variable Bornholm Basin.- In addition, growth was maintained in early stages of the growth curve by organic carbon acquisition and the increase in growth over time and with temperature was associated with an increase in inorganic carbon acquisition (net primary productivity).- Based on the differences between net primary productivity and potential growth on organic carbon, we postulate a shift in carbon acquisition between inorganic and organic sources in Ostreococcus sp. with potential implications on ecological dynamics within microbial communities.

Changes in the composition and abundance of ichthyoplankton along environmental gradients of the southern Baltic Sea

The research focuses mainly on the ichthyoplankton of the Baltic deeps – the inflow route from the North Sea. The ichthyoplankton was represented by eggs and larvae of nine fish species: sprat, cod, herring, European flounder, fourbeard rockling, longspined bullhead, straightnose pipefish, sand goby and great sandeel. The species composition of ichthyoplankton varied depending on the location of a given site – the number of taxa ranged from one to five. The Slupsk Furrow was the most diversified area in terms of the number of taxa, while the highest abundance of ichthyoplankton occurred in the Bornholm Basin. The sprat clearly dominated and inhabited all the surveyed depths. Of the remaining species, only cod eggs as well as eggs and larvae of the fourbeard rockling significantly contributed to this formation. They occurred within their main spawning grounds (Bornholm Deep in the near-bottom layers) and secondary spawning grounds (Slupsk Furrow and Gdansk Deep) where salinity and oxygenation of water favored their development. Biometric research has shown that the diameter of eggs was within the size range typical of the Baltic Sea.

FEATURES OF THE NORTH SEA WATER SPREADING IN THE BORNHOLM BASIN BY MODEL RESULTS

With the help of mathematical modeling, the features of the distribution of North Sea waters in the Bornholm basin are considered on the example of a large inflow occurring in January 2003. For better resolution of bottom processes in the bottom density flow model, the computational domain is split vertically into bottom and overlying areas. In the lower region with a thickness of 20 m, the vertical grid spacing is 1 m. The basic equations of the model are transformed for each of the regions using σ-coordinate. According to the simulation results, the features of the distribution of North Sea water are highlighted, as well as the associated change in the salinity field in the overlying layer. Estimates of the possible influence of runoff currents on the distribution of North Sea waters are obtained.

Rare earth elements in Fe-Mn nodules from southern Baltic Sea – a preliminary study

Between 1976–1990, the Polish Geological Institute performed geological works in the Polish Maritime Areas. During these works, 260 occurrences of concretions were recorded from 7,500 sampled sites. In 1980, the threshold that separates the Bornholm Basin from the Słupsk Furrow was mapped. Numerous Fe-Mn nodules on the seabed were found in that area. The results of detailed analyses of nodule samples collected from four sites are presented in this paper. Analyzed nodules represent discoidal D, irregular I, and transitional D-I types. The nodules are characterized by varied chemical composition of main oxides (Fe, Mn). The maximum Fe2O3 content is 26.63% and MnO 23.18%. Total average amount of REE + Y in the samples is approximately 165.11 ppm, ΣLREE 145.72 ppm and ΣHREE 19.39 ppm. The LREE content is enriched in comparison to HREE. The majority of nodules consist of Fe-Mn oxy-hydroxide minerals with very low crystallinity (practically amorphous phases). The main confirmed Mn-phases are birnessite and todorokite. Other main components of the nodules are: detrital quartz, albite, microcline, glauconite and muscovite, clinochlore, and clay minerals: illite and chlorite. The rate of growth of Fe-Mn nodules has been estimated using a cobalt chronometer. The nodule growth rate ranges from 0.006 to 0.134 mm/yr –1. Based on the Fe, Mn and (Cu + Co + Ni) contents, the origin of studied nodules is determined as hydrogenetic, while using REE (Cesn/Cesn · vs. Nd) – as diagenetic.