Bożena Graca

THE IMPACT OF DREDGING DEEP PITS ON ORGANIC MATTER DECOMPOSITION IN SEDIMENTS

In this study, the results of investigations of organic matter decomposition in natural and dredged areas of the inner Puck Bay (Baltic Sea) are presented. The dredging of relatively deep pits causes environmental problems. Researched post-dredging pits are sediment traps in which 3 times more organic carbon (Corg), 3.5 times more total nitrogen (Ntot), about 1.5 times more organic phosphorus (Porg) and 1.7 times more total phosphorus (Ptot) accumulate as compared to the non-dredged regions; they are also characterized by very intensive decomposition of organic matter. About 42, 44, 95 and 50% of the annual load of, respectively, Corg, Ntot, Porg and Ptot undergo decomposition in the dredged area, whereas the respective values for natural seabed are ca. 11, 44, 41 and 21%. Reduction of nitrogen in the pit occurs mainly through ammonification, while in the natural areas of seabed denitrification prevails. In non-dredged sediments, 84% of the released nitrogen comes from denitrification whereas in the pit, it is only 18%. Organic matter degradation in the pit sediments manifests itself by a 7-fold increase in the phosphate flux into near-bottom water as compared to natural seabed. The observed phosphate flux originated from the organic matter as well as from the decomposition of inorganic phosphorus compounds. Periodically, sulphate reduction in the pit sediments resulted in hydrogen sulfide occurrence.

Factors determining accumulation of bisphenol A and alkylphenols at a low trophic level as exemplified by mussels Mytilus trossulus.

The aim of the study was to investigate abiotic and biotic factors influencing the accumulation of endocrine disrupting compounds (EDCs) such as bisphenol A (BPA), 4-tert-octylphenol (OP) and 4-nonylphenol (NP) in mussels Mytilus trossulus from the Gulf of Gdansk (Southern Baltic). The key abiotic factor influencing BPA, OP and NP accumulation in mussels is their hydrophilicity/lipophilicity, which affects their main assimilation routes - by digestive tract for the more lipophilic OP and NP, and additionally by the gills for the less lipophilic BPA. As a result, high condition index (i.e. higher soft tissue weight) is more often correlated with high concentrations of OP and NP in mussels than with BPA. Furthermore, alkylphenols have 6-8 times greater accumulative potential than BPA. Concentration of the studied compounds was lower in females than in males following spawning, and the effect lasted longer for BPA than for alkylphenols. The influence of season and hydrological conditions on BPA, OP, NP in the mussel was more pronounced than the proximity of external sources of these compounds. An increase in water temperature in summer probably stimulated the solubility of BPA, the least lipophilic of the studied compounds, and led to increased assimilation of this compound from water (through gills). On the other hand, high OP and NP concentrations in mussels occurred in spring, which was caused by increased surface run-off and sediments resuspension.

Laboratory study of the effect of salinity and ionic composition of water on the mortality and osmoregulation of the gammarid amphipod Dikerogammarus haemobaphes (Eichwald, 1841): implications for understanding its invasive distribution pattern

The effect of salinity and ionic composition of ambient water on the mortality of the Ponto-Caspian gammarid amphipod Dikerogammarus haemobaphes (Eichwald, 1841) was measured in the laboratory and an osmoregulatory curve plotted. A three-day experiment showed that salinities both higher (15, 20 PSU) and lower (0.1, 3.5 PSU) than 7 PSU reduced survival. Salinity levels of 0.1 and 20 PSU were lethal after 20 and 55 h of exposure, respectively. Among the ions analysed (Cl−, , Na+, K+, Ca2+, Mg2+), Cl− and K+, and the ratios of Na+/K+ and Na+/Cl− had the greatest influence on the mortality of D. haemobaphes. Mortality was zero in waters where the concentrations and ratios of these ions most closely resembled those prevailing in the Caspian Sea. The osmoregulatory curve shows that D. haemobaphes is a eurytopic species i.e. osmoregulation is hyperosmotic within the salinity range of 0.1–20 PSU. The results of this study indicate ways in which inherent physiological capabilities affect the ability of an organism to tolerate environmental conditions outside its historical range. The results suggest some ways in which anthropogenic changes may have affected the spread of this species beyond its original range.

Seasonal changes of mercury speciation in the coastal sediments

PurposeMercury speciation in sediments is linked to environmental conditions and processes. Domination of particular mercury species depends on its source, displays considerable seasonal behavior, and may be further modified due to oxygen levels, icing conditions, or the input of fresh organic matter. The purpose of this study was to examine the coastal area of the Gulf of Gdańsk in terms of mercury contamination and the influence of seasonal environmental changes on its speciation.Materials and methodsIn three highly dynamic coastal sites, mercury speciation in sediments was studied in relation to other environmental parameters (redox conditions, organic matter concentration, bacteria abundance, etc.). Sediment and water samples were collected monthly during a 3-year study. Sequential extraction of sediments was used for identification of four inorganic mercury species: dissolved, bound with fulvic and humic acids, mercury sulfide, and residual fraction. Cold vapor atomic fluorescence spectrometry (CV-AFS) was used for extracts and liquid sample analysis. Total mercury in sediments was measured with atomic absorption spectrometry (AAS). Changes in salinity were analyzed by measurements of chloride and sulfate ion concentrations using ion chromatography. Bacteria number and biomass were measured by direct counting using epifluorescence microscopy.Results and discussionSeasonal changes in mercury speciation were observed at all sites and attributed to different processes. Labile mercury fraction contribution varied from 0 to 80%. The speciation patterns varied locally as the stations selected for the study are diversified in terms of anthropogenic impact, water dynamics, and output from land. Mercury concentrations at all stations fluctuated during phytoplankton blooms, icing of marine waters, precipitation, or increased surface runoff from the land. In this local scale, the global climate changes are visible already as environmental conditions in studied area changed in comparison to elder research.ConclusionsObtained results suggest that although mercury emissions to the environment have decreased in recent years, local weather conditions, which may be intensified by climate change, seriously affect the bioavailability of past mercury deposits in coastal sediments.

Effect of salinity on the distribution of Ponto-Caspian gammarids in a non-native area – environmental and experimental study

ABSTRACT The native area of gammarids from the so-called ‘Caspian complex’, Pontogammarus robustoides (G.O. Sars, 1894), Obesogammarus crassus (G.O. Sars, 1894), Dikerogammarus haemobaphes (Eichwald, 1841) and D. villosus (Sowinsky, 1894), is associated with brackish waters. Over the last several decades they have colonized the European inland waters and part of the brackish Baltic Sea. It is believed that anthropogenic increase in the salinity of inland waters facilitated their expansion. However, the influence of salinity on the dispersal of gammarid species outside their native area is not fully understood. We tested the hypothesis that salinity was a major factor in determining distribution, based on the abundance of Gammaridae in three coastal areas of low salinity (brackish Baltic), i.e. 0.3, 3.4 and 7.3 PSU, successfully inhabited by them. Additionally, for the first time, the effect of water salinity on the osmoregulatory capacity of O. crassus was examined under laboratory conditions, for the salinities given above. The experiments showed that similarly as in the case of other Caspian complex species, salinity values of about 7 PSU create better conditions for osmoregulation in O. crassus than lower salinities (i.e. 0.3 and 3.4 PSU). In the environmental part of the study, we observed that only D. villosus achieved a significantly higher abundance in the area of 7.3 PSU. Thus, we concluded that in the range of 0.3–7.3 PSU, salinity is not a key factor governing the distribution of Ponto-Caspian gammarids.

Diversity and environmental control of benthic harpacticoids of an offshore post-dredging pit in coastal waters of Puck Bay, Baltic Sea

Abstract Placer extraction in Puck Bay, a shallow (3 m depth) area of the Baltic Sea, resulted in the formation of post-dredging pits. Such dredging activities led to a considerable local disturbance of the soft-bottom communities. Topography and sedimentary characteristics of the disturbed area have been radically changed. It is therefore a matter of concern as to whether these alterations to the environment resulted in any serious permanent changes to the biological communities in the affected areas. Benthic copepod assemblages were examined 10 years after termination of placer digging in one of the post-dredging pits and compared with the fauna in a natural depression (Kuźnicka Hollow) and on the shallow sandy bottom surrounding the pits. Samples were collected on four occasions in 2001–2003. This study has generated ecological information on the status of harpacticoid species inhabiting the dredged and undredged areas in the vicinity. Analyses of data showed that the sampling stations differed significantly, during all the sampling events, in harpacticoid abundance, taxonomic composition and Shannon–Wiener diversity index. The natural depression and the shallow sandy bottom of Puck Bay were found to support specific harpacticoid assemblages. Interstitial and sand-burrowing species (e.g. Paraleptastacus spinicauda) dominate the shallow sandy bottom, and the Kuźnicka Hollow is inhabited mainly by epibenthic and silt-burrowing species (e.g. Halectinosoma curticorne, Tachidius discipes, Microarthridion littorale). The post-dredging pit assemblage showed the presence of epibenthic species, e.g. Tachidius discipes, Dactylopusia euryhalina, and Stenhelia palustris, passively transported into the pit by wave action and currents, possibly with algal mats and/or plant remains. The taxonomic composition and occurrence of harpacticoid species in the post-dredging area is therefore random and accidental.

Seasonal variation in accumulation of mercury in the benthic macrofauna in a temperate coastal zone (Gulf of Gdańsk)

The main source of toxic mercury (Hg) in the human body is the consumption of fish and seafood. Therefore, it is particularly important to indicate the processes that condition Hg accumulation in marine organisms, especially those in the basal links of the food chain, which are rather poorly investigated compared to top predators. The aim of the study was to determine the seasonal variability of Hg concentrations in macrozoobenthic organisms and the factors that condition it. The research was conducted in 2012-2013 in a temperate coastal zone (Gulf of Gdańsk). The obtained results showed that both Hg concentrations within one trophic level, and their seasonal variation, may differ significantly if the organisms have different feeding habits. The research also indicated that the seasonal variability of Hg level in macrozoobenthos depended on a number of both biotic factors (primary production volume, biomass and rate of fauna metabolism) and abiotic factors (salinity and ionic composition of water, Eh). The variability of Hg concentrations in macrozoobenthos during the study period was different at the research stations, which were subjected to different land influence (e.g. surface run-off, coastal erosion), and consequently differed in the quantity and quality of organic matter. The increased load of suspended particulate matter (SPM) was also an important factor influencing the increase in Hg concentration in macrozoobenthos, regardless of their trophic status. This indicates that SPM is an important source of food for zoobenthos, even in species that prefer a different feeding strategies. The obtained results also showed the role of climate changes observed in the temperate zone - in particular, the warming of the winter season - in shaping the Hg level in macrozoobenthos. The accumulation of Hg in the bottom fauna occurred most intensively in spring immediately after a long period of icing - Hg concentrations were then much higher than those measured after a mild winter, during which the ice cover persisted for a short time. The warming of the winter season and the extension of the vegetation season contributed to an increase in macrozoobenthic biomass, and consequently to the biodilution of Hg, which could have had a negative effect on the Hg load introduced into the trophic chain.

Origin and fate of nanoparticles in marine water – Preliminary results

The number, morphology and elemental composition of nanoparticles (<100 nm) in marine water was investigated using Variable Pressure Scanning Electron Microscopy (VP-SEM) and Energy-dispersive X-ray spectroscopy (EDS). Preliminary research conducted in the Baltic Sea showed that the number of nanoparticles in seawater varied from undetectable to 380 (x102) cm-3. Wind mixing and density barriers (thermocline) had a significant impact on the abundance and distribution of nanoparticles in water. Many more nanoparticles (mainly nanofibers) were detected in periods of intensive primary production and thermal stratification of water than at the end of the growing season and during periods of strong wind mixing. Temporal and spatial variability of nanoparticles as well as air mass trajectories indicated that the analysed nanofibers were both autochthonous and allochthonous (atmospheric), while the nanospheres were mainly autochthonous. Chemical composition of most of analysed nanoparticles indicates their autochthonous, natural (biogenic/geogenic) origin. Silica nanofibers (probably the remains of flagellates), nanofibers composed of manganese and iron oxides (probably of microbial origin), and pyrite nanospheres (probable formed in anoxic sediments), were all identified in the samples. Only asbestos nanofibers, which were also detected, are probably allochthonous and anthropogenic.

Geochemical Changes in Aquatic Environment Caused by Deep Dredging - A Case Study: The Puck Bay (Baltic Sea)

Dredge activities is very widespread antropogenic seabed disturbance. It is used to replenish sand on beaches, to create and maintain harbor, berth, waterways, may also be used for underwater mining activities and as a technique for fishing certain species of crabs or edible clams. Dredging has many deleterious environmental effects (Johnston 1981). Changes in bottom topography due to dredging can influence water dynamic and in consequence sediment transport (Maa et al., 2004; Work at al. 2004). Dredge pits and deep furrows can create a sink for fine-grained sediments, organic matter and contaminants (Desprez 2000) and result in hypoxic and anoxic conditions, as well as sulfate reduction in sediment (Bolalek et al., 1996, Flocks&Franze 2002, Graca at al. 2004) (Fig. 1). Geochemical changes resulted in deep dredging can affect benthic organisms. Limited recolonization of dredge pits was observed (Palmer et al. 2008, Szymelfenig et al. 2006). Such condition can influence nutrients dynamic and potentially stimulate eutrophication (Graca et al., 2004). Impact of dredging depends on its intensity and the type of used method, as well as the environmental condition in dredge area (Boyd et al. 2005, Robinson et al. 2005). Puck Bay is a small water body located on the Polish Baltic coast. Deep dredging works carried in this reservoir, creates great opportunity to study the impact of deep dredging in areas with different water dynamics. From the north the bay is restricted from the open Baltic by the Hel Peninsula. It is 34 km long, and its width varies from 0.2 km to 2.9 km. A change of peninsula land cover during the last few decades, especially the construction of the new harbor, enhanced erosion processes. At present, the Hel Peninsula requires intensive reinforcement (Urbanski & Solanowska, 2009). Eighty-two percent (c.a. 6,98 mln m3) of sands for peninsula’s bank protection was gained from the bottom of the Puck Bay. First large beach nourishment was carried out by the end of 80’s in last century. As an effect, in the years 1989-95, five the dredge pits were created in the bottom of the Puck Bay along the Hel Peninsula (Fig.2). The depth of the pits reaches 7-14 m, while natural depth in the surrounding area does not exceed 2 m.