Identifying recent sources and fate of sedimentary nitrogen in the Baltic Sea based on organic matter elemental composition and nitrogen and carbon stable isotopes ratios

Abstract. Extracellular enzymatic activities (EEAs) are a crucial step in the degradation of organic matter. Dissolved (cell-free) extracellular enzymes in seawater can make up a significant contribution of the bulk EEA. However, the factors controlling the proportion of dissolved EEA in the marine environment remain unknown. Here we studied the seasonal changes in the proportion of dissolved relative to total EEA (of alkaline phosphatase (APase), β-glucosidase (BGase), and leucine aminopeptidase (LAPase)), in the Baltic Sea for 18 months. The proportion of dissolved EEA ranged between 37 and 100, 0 and 100, and 34 and 100 % for APase, BGase, and LAPase, respectively. A consistent seasonal pattern in the proportion of dissolved EEA was found among all the studied enzymes, with values up to 100 % during winter and <  40 % during summer. A significant negative relation was found between the proportion of dissolved EEA and temperature, indicating that temperature might be a critical factor controlling the proportion of dissolved relative to total EEA in marine environments. Our results suggest a strong decoupling of hydrolysis rates from microbial dynamics in cold waters. This implies that under cold conditions, cell-free enzymes can contribute to substrate availability at large distances from the producing cell, increasing the dissociation between the hydrolysis of organic compounds and the actual microbes producing the enzymes. This might also suggest a potential effect of global warming on the hydrolysis of organic matter via a reduction of the contribution of cell-free enzymes to the bulk hydrolytic activity.

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Pectenotoxin-2 and dinophysistoxin-1 in suspended and sedimenting organic matter in the Baltic Sea

Limnology and Oceanography ◽

10.4319/lo.2006.51.5.2300 ◽

2006 ◽

Vol 51 (5) ◽

pp. 2300-2307 ◽

Cited By ~ 18

Author(s):

Pirjo Kuuppo ◽

Pauliina Uronen ◽

Anika Petermann ◽

Timo Tamminen ◽

Edna Granéli

Keyword(s):

Organic Matter ◽

Baltic Sea ◽

The Baltic Sea ◽

The Baltic ◽

Pectenotoxin 2

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The influence of dissolved organic matter on the acid–base system of the Baltic Sea

Journal of Marine Systems ◽

10.1016/j.jmarsys.2014.01.011 ◽

2014 ◽

Vol 132 ◽

pp. 106-115 ◽

Cited By ~ 51

Author(s):

Karol Kuliński ◽

Bernd Schneider ◽

Karoline Hammer ◽

Ulrike Machulik ◽

Detlef Schulz-Bull

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Baltic Sea ◽

Base System ◽

The Baltic Sea ◽

Acid Base ◽

The Baltic

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Study on organic matter fractions in the surface micro layer in the Baltic Sea by spectrophotometric and spectrofluorometric methods

10.5194/os-2017-4 ◽

2017 ◽

Author(s):

Violetta Drozdowska ◽

Iwona Wróbel ◽

Piotr Markuszewski ◽

Przemyslaw Makuch ◽

Anna Raczkowska ◽

...

Keyword(s):

Organic Matter ◽

Baltic Sea ◽

Subsurface Layer ◽

Molecular Size ◽

Surface Microlayer ◽

The Baltic Sea ◽

Vistula River ◽

Meteorological Observations ◽

Organic Matter Fractions ◽

The Baltic

Abstract. The fluorescence and absorption measurements of the samples collected from a surface microlayer (SML) and a subsurface layer (SS), a depth of 1 m were studied during three research cruises in the Baltic Sea along with hydrophysical studies and meteorological observations. Several absorption (E2 : E3, S, SR) and fluorescence (fluorescence intensities at peaks: A, C, M, T, the ratio (M + T) / (A + C), HIX) indices of colored and fluorescent organic matter (CDOM and FDOM) helped to describe the changes in molecular size and weight as well as in composition of organic matter. The investigation allow to assess a decrease in the contribution of two terrestrial components (A and C) with increasing salinity (~ 1.64 % and ~ 1.89 % in SML and ~ 0.78 % and ~ 0.71 % in SS, respectively) and an increase of in-situ produced components (M and T) with salinity (~ 0.52 % and ~ 2.83 % in SML and ~ 0.98 % and ~ 1.87 % in SS, respectively). Hence, a component T reveals the biggest relative changes along the transect from the Vistula River outlet to Gdansk Deep, both in SML and SS, however an increase was higher in SML than in SS (~ 18.5 % and ~ 12.3 %, respectively). The ratio E2 : E3

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Parameterization of the light absorption properties of chromophoric dissolved organic matter in the Baltic Sea and Pomeranian lakes

Ocean Science ◽

10.5194/os-12-1013-2016 ◽

2016 ◽

Vol 12 (4) ◽

pp. 1013-1032 ◽

Cited By ~ 12

Author(s):

Justyna Meler ◽

Piotr Kowalczuk ◽

Mirosława Ostrowska ◽

Dariusz Ficek ◽

Monika Zabłocka ◽

...

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Absorption Coefficient ◽

Baltic Sea ◽

Chlorophyll A ◽

Chromophoric Dissolved Organic Matter ◽

The Baltic Sea ◽

Absorption Properties ◽

Chlorophyll A Concentration ◽

The Baltic

Abstract. This study presents three alternative models for estimating the absorption properties of chromophoric dissolved organic matter aCDOM(λ). For this analysis we used a database containing 556 absorption spectra measured in 2006–2009 in different regions of the Baltic Sea (open and coastal waters, the Gulf of Gdańsk and the Pomeranian Bay), at river mouths, in the Szczecin Lagoon and also in three lakes in Pomerania (Poland) – Obłęskie, Łebsko and Chotkowskie. The variability range of the chromophoric dissolved organic matter (CDOM) absorption coefficient at 400 nm, aCDOM(400), lay within 0.15–8.85 m−1. The variability in aCDOM(λ) was parameterized with respect to the variability over 3 orders of magnitude in the chlorophyll a concentration Chl a (0.7–119 mg m−3). The chlorophyll a concentration and aCDOM(400) were correlated, and a statistically significant, nonlinear empirical relationship between these parameters was derived (R2 =  0.83). On the basis of the covariance between these parameters, we derived two empirical mathematical models that enabled us to design the CDOM absorption coefficient dynamics in natural waters and reconstruct the complete CDOM absorption spectrum in the UV and visible spectral domains. The input variable in the first model was the chlorophyll a concentration, and in the second one it was aCDOM(400). Both models were fitted to a power function, and a second-order polynomial function was used as the exponent. Regression coefficients for these formulas were determined for wavelengths from 240 to 700 nm at 5 nm intervals. Both approximations reflected the real shape of the absorption spectra with a low level of uncertainty. Comparison of these approximations with other models of light absorption by CDOM demonstrated that our parameterizations were superior (bias from −1.45 to 62 %, RSME from 22 to 220 %) for estimating CDOM absorption in the optically complex waters of the Baltic Sea and Pomeranian lakes.

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Response of Nodularia spumigena to pCO2 – Part 1: Growth, production and nitrogen cycling

Biogeosciences ◽

10.5194/bg-9-2973-2012 ◽

2012 ◽

Vol 9 (8) ◽

pp. 2973-2988 ◽

Cited By ~ 27

Author(s):

N. Wannicke ◽

S. Endres ◽

A. Engel ◽

H.-P. Grossart ◽

M. Nausch ◽

...

Keyword(s):

Organic Matter ◽

Baltic Sea ◽

N2 Fixation ◽

Inorganic Nitrogen ◽

High Pco2 ◽

The Baltic Sea ◽

Nodularia Spumigena ◽

Co2 Concentrations ◽

Elemental Stoichiometry ◽

The Baltic

Abstract. Heterocystous cyanobacteria of the genus Nodularia form extensive blooms in the Baltic Sea and contribute substantially to the total annual primary production. Moreover, they dispense a large fraction of new nitrogen to the ecosystem when inorganic nitrogen concentration in summer is low. Thus, it is of ecological importance to know how Nodularia will react to future environmental changes, in particular to increasing carbon dioxide (CO2) concentrations and what consequences there might arise for cycling of organic matter in the Baltic Sea. Here, we determined carbon (C) and dinitrogen (N2) fixation rates, growth, elemental stoichiometry of particulate organic matter and nitrogen turnover in batch cultures of the heterocystous cyanobacterium Nodularia spumigena under low (median 315 μatm), mid (median 353 μatm), and high (median 548 μatm) CO2 concentrations. Our results demonstrate an overall stimulating effect of rising pCO2 on C and N2 fixation, as well as on cell growth. An increase in pCO2 during incubation days 0 to 9 resulted in an elevation in growth rate by 84 ± 38% (low vs. high pCO2) and 40 ± 25% (mid vs. high pCO2), as well as in N2 fixation by 93 ± 35% and 38 ± 1%, respectively. C uptake rates showed high standard deviations within treatments and in between sampling days. Nevertheless, C fixation in the high pCO2 treatment was elevated compared to the other two treatments by 97% (high vs. low) and 44% (high vs. mid) at day 0 and day 3, but this effect diminished afterwards. Additionally, elevation in carbon to nitrogen and nitrogen to phosphorus ratios of the particulate biomass formed (POC : POP and PON : POP) was observed at high pCO2. Our findings suggest that rising pCO2 stimulates the growth of heterocystous diazotrophic cyanobacteria, in a similar way as reported for the non-heterocystous diazotroph Trichodesmium. Implications for biogeochemical cycling and food web dynamics, as well as ecological and socio-economical aspects in the Baltic Sea are discussed.

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