Polymorphism of CaCO3 and the variability of elemental composition of the calcareous skeletons secreted by invertebrates along the salinity gradient of the Baltic Sea

Biomineralization is of great importance in ecosystem functioning and for the use of carbonate skeleton as environmental proxies. Skeletal formation is controlled to different degrees by environmental parameters and biological mechanisms. While salinity is one of the most important factors affecting ecological processes and ocean physiochemistry, the goal of this investigation was to identify how salinity influences the mineral type and the concentrations of chemical elements in the whole skeleton of invertebrates from the Baltic Sea. In this model system, the surface salinity decreases from marine values (27.2) to almost fresh water (6.1). The selected organisms, mussels (Mytilus spp.), bryozoans (Einhornia crustulenta, Cribrilina cryptooecium, Cryptosula pallasiana, Electra pilosa, Escharella immersa), barnacles (Amphibalanus improvisus, Semibalanus balanoides), and polychaetes (Spirorbis tridentatus), precipitated skeleton composed of calcite and aragonite, most likely as a result of various interacting environmental and biological factors. The concentrations of all elements in bulk skeleton were highly variable between species from the same location, underlining the role of the biological mechanisms in skeletal formation. The concentration of Ca, Mg, Sr, and Na increased in the bulk skeleton of stenohaline organisms with increasing salinity, while in the bulk skeleton of euryhaline species, only the concentration of Na increased with increasing salinity. The concentrations of Mn, Ba, Cu, Pb, Y, V, Cd, and U in the skeleton of euryhaline species generally decreased at higher salinities, most likely reflecting the lower bioavailability of elements at higher salinity. However, the concentrations of elements in the skeleton of stenohaline organisms were highly variable with no clear salinity impact. This study suggests that, although the composition of skeleton of calcifying organisms along the salinity gradient of the Baltic Sea is to a large extent affected by biological mechanisms, it also reflects the responses to environmental conditions.

Submarine groundwater discharge as a source of pharmaceutical and caffeine residues in coastal ecosystem: Bay of Puck, southern Baltic Sea case study

Even though the occurrence of pharmaceuticals in the water environment is thought to be a potential problem for human health and aquatic organisms, the level of knowledge of their sources and presence in the marine ecosystem is still insufficient. Therefore, this study was designed to determine the emergence of sixteen pharmaceuticals and caffeine in groundwater, submarine groundwater discharge (SGD), rivers and coastal seawater in the southern Baltic Sea. It has been recognized that chemical substances load associated with SGD can affect coastal ecosystems equally or even greater than surface runoff. Hence, the Bay of Puck, which is an active groundwater discharge area, has been chosen as a model study site to assess the preliminary risk of pharmaceutical and caffeine residues supply in coastal ecosystem. A special focus was placed on tracing the possible sources of pollution for groundwater and SGD based on the composition of collected samples. Five pharmaceuticals (carbamazepine, sulfapyridine, sulfamethoxazole, ketoprofen and diclofenac) and caffeine were detected in varying concentrations from below the detection limit to 1528.2 ng L^-1. Caffeine and diclofenac were the most widespread compounds. Groundwater was mostly enriched in the analysed compounds and consequently SGD has been recognized as an important source of identified pharmaceutical and caffeine residues to the Bay of Puck. A predicted no-effect concentration (PNEC) was determined in order to perform an environmental risk assessment of five pharmaceuticals and caffeine detected in water samples. Finally, future challenges and potential amendments in monitoring strategies are discussed.

Legacy and emerging pollutants in the Gulf of Gdańsk (southern Baltic Sea) - loads and distribution revisited

Coastal marine areas of densely populated countries are exposed to a wide array of human activities having an impact on their ecological status. The Baltic Sea is particularly susceptible to pollution by hazardous substances (limited water exchange, shallowness, and large catchment area). Polish media regularly reports ecological catastrophes in the Gulf of Gdańsk area caused by eg. shipwrecks leaking. Thus, there is a need of a broad scientific based report on recent contaminant loads and distribution. In this review paper, we report loads of contaminants from different obvious and non-obvious sources. We also gather data on legacy and new emerging contaminant concentrations measured in the Gulf of Gdańsk within the last decade (2008-2018). The paper also includes available biological effect measurements performed recently as well as a summary of needs and gaps to be filled for the development of reliable risk assessment.

Sorption of Cr, Pb, Cu, Zn, Cd, Ni, and Co to nano-TiO2 in seawater

In this study, the role of nanoparticles in complex aqueous matrices such as the Baltic Sea was investigated in batch-mode experiments in which titanium dioxide nanoparticles (nano-TiO₂) were tested for their ability to remove heavy metals (Cr, Pb, Cu, Zn, Cd, Ni, Co) from multicomponent spiked and non-spiked Baltic Sea water. The experimental data were analyzed using different isotherms (Langmuir, Freundlich, Dubinin-Kaganer-Radushkevich (DKR)) and models (pseudo-first-order and pseudo-second-order models, the double-exponential model, and the Weber-Morris model). The equilibria and kinetic investigations showed that metal sorption to nano-TiO₂ occurs in a two-step, multilayer process and that there is strong competition for sorption sites. The results of the DKR isotherm and dilution experiment indicated weak electrostatic bonds, except for Pb. The distribution coefficient values (1.8 × 10³ to 2.8 × 10⁵ ml g^-1) were consistent with the good sorbent properties of nano-TiO₂ and supported the use of the particles in seawater purification technologies. However, metal-enriched nano-TiO₂ may also act as an effective carriers of metals to marine sediments, which could increase their availability to benthic organisms.

Depth of the vadose zone controls aquifer biogeochemical conditions and extent of anthropogenic nitrogen removal

We investigated biogeochemical conditions and watershed features controlling the extent of nitrate removal through microbial dinitrogen (N₂) production within the surficial glacial aquifer located on the north and south shores of Long Island, NY, USA. The extent of N₂ production differs within portions of the aquifer, with greatest N₂ production observed at the south shore of Long Island where the vadose zone is thinnest, while limited N₂ production occurred under the thick vadose zones on the north shore. In areas with a shallow water table and thin vadose zone, low oxygen concentrations and sufficient DOC concentrations are conducive to N₂ production. Results support the hypothesis that in aquifers without a significant supply of sediment-bound reducing potential, vadose zone thickness exerts an important control of the extent of N₂ production. Since quantification of excess N₂ relies on knowledge of equilibrium N₂ concentration at recharge, calculated based on temperature at recharge, we further identify several features, such as land use and cover, seasonality of recharge, and climate change that should be considered to refine estimation of recharge temperature, its deviation from mean annual air temperature, and resulting deviation from expected equilibrium gas concentrations.

Significance of groundwater discharge along the coast of Poland as a source of dissolved metals to the southern Baltic Sea

Fluxes of dissolved trace metals (Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn) via groundwater discharge along the southern Baltic Sea have been assessed for the first time. Dissolved metal concentrations in groundwater samples were less variable than in seawater and were generally one or two orders of magnitude higher: Cd (2.1-2.8nmolL(-1)), Co (8.70-8.76nmolL(-1)), Cr (18.1-18.5nmolL(-1)), Mn (2.4-2.8μmolL(-1)), Pb (1.2-1.5nmolL(-1)), Zn (33.1-34.0nmolL(-1)). Concentrations of Cu (0.5-0.8nmolL(-1)) and Ni (4.9-5.8nmolL(-1)) were, respectively, 32 and 4 times lower, than in seawater. Groundwater-derived trace metal fluxes constitute 93% for Cd, 80% for Co, 91% for Cr, 6% for Cu, 66% for Mn, 4% for Ni, 70% for Pb and 93% for Zn of the total freshwater trace metal flux to the Bay of Puck. Groundwater-seawater mixing, redox conditions and Mn-cycling are the main processes responsible for trace metal distribution in groundwater discharge sites.

Submarine Groundwater Discharge as a Source of Mercury in the Bay of Puck, the Southern Baltic Sea

Both groundwater flow and mercury concentrations in pore water and seawater were quantified in the groundwater seeping site of the Bay of Puck, southern Baltic Sea. Total dissolved mercury (HgTD) in pore water ranged from 0.51 to 4.90 ng l-1. Seawater samples were characterized by elevated HgTD concentrations, ranging from 4.41 to 6.37 ng l-1, while HgTD concentrations in groundwater samples ranged from 0.51 to 1.15 ng l-1. High HgTD concentrations in pore water of the uppermost sediment layers were attributed to seawater intrusion into the sediment. The relationship between HgTD concentrations and salinity of pore water was non-conservative, indicating removal of dissolved mercury upon mixing seawater with groundwater. The mechanism of dissolved mercury removal was further elucidated by examining its relationships with both dissolved organic matter, dissolved manganese (Mn II), and redox potential. The flux of HgTD to the Bay of Puck was estimated to be 18.9 ± 6.3 g year-1. The submarine groundwater discharge-derived mercury load is substantially smaller than atmospheric deposition and riverine discharge to the Bay of Puck. Thus, groundwater is a factor that dilutes the mercury concentrations in pore water and, as a result, dilutes the mercury concentrations in the water column.

Nutrient fluxes via submarine groundwater discharge to the Bay of Puck, southern Baltic Sea

Submarine groundwater discharge (SGD) has been recognized as an important exchange pathway between hydrologic reservoirs due to its impact on biogeochemical cycles of the coastal ocean. This study reports nutrient concentrations and loads delivered by SGD into the Bay of Puck, the southern Baltic Sea. Measurements were carried out between September, 2009 and October, 2010 at groundwater seepage sites identified by low salinity of pore water. Groundwater fluxes, measured using seepage meters, ranged from 3 to 22 L m(-2)day(-1). Average concentrations of nutrients in groundwater samples collected were as follows: 0.4 μmol L(-1) nitrate (NO(3)), 0.8 μmol L(-1) nitrite (NO(2)), 18.2 μmol L(-1) ammonium (NH(4)) and 60.6 μmol L(-1) orthophosphate (PO(4)). Levels of NH(4) and PO(4) were significantly higher in samples from SGD sites than in seawater. Seawater and SGD samples showed similar NO(2) concentrations but SGD samples exhibited lower NO(3) levels than those observed in seawater samples. Measured seepage water fluxes and nutrient concentrations were used to calculate nutrient loads discharged into the study area while the literature groundwater flux and the measured nutrient concentrations were used to estimate nutrient loads discharged into the Bay of Puck. The estimates suggest that SGD delivers a dissolved inorganic nitrogen (DIN) load of 49.9 ± 18.0 t yr(-1) and a PO(4)(-) load of 56.3 ± 5.5tyr(-1) into the Bay of Puck. The projected estimates are significant in comparison with loads delivered to the bay from other, well-recognized sources (705 ty r(-1) and 105 ty r(-1) respectively for DIN and PO(4)). Nutrient discharge input loads were projected to the entire Baltic Sea The extrapolated values indicate SGD contributes a significant proportion of phosphate load but only an insignificant proportion of DIN load. Further studies are necessary to better understand SGD contributions to the nutrient budget in the Baltic Sea.