Seasonal dynamics of dissolved organic matter and microbial activity in the coastal North Sea

Sintes, Eva; Stoderegger, Karen E.; Parada, Verónica; Herndl, Gerhard J.

doi:10.3354/ame01404

Cited by 33 publications

(30 citation statements)

References 51 publications

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“…This means that the initial qualities of DOC and DON (as specified in Table 2), determined by the catchment characteristics, were the major factor defining the biodegradability of DOC and DON, which supports our main hypothesis. Bioavailability of DOM has been previously reported to have strong seasonal variation (Lønborg et al, 2009;Sintes et al, 2010). However, in the experiments presented here the season surprisingly did not have significant effect on DOC and DON degradation in spite of the seasonal changes in DOM quantity and quality in study estuaries (Fig.…”

Section: Doc and Don Degradationcontrasting

confidence: 37%

Bioavailability of riverine dissolved organic matter in three Baltic Sea estuaries and the effect of catchment land use

et al. 2013

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Abstract. The microbial degradation of dissolved organic carbon and nitrogen (DOC, DON) was studied in three Finnish boreal estuaries with contrasting land use patterns (Kiiminkijoki -natural forest and peatland; Kyrönjoki -agricultural; Karjaanjoki -mixed/urban). Bioassays of 12-18 d long durations were used in 3 seasons at in situ temperatures. Besides the bulk parameters, a suite of dissolved organic matter (DOM) quality parameters were also investigated, including colored DOM (CDOM), fluorescent DOM and the molecular weight of DOM. Bioavailable DOC and DON pools varied significantly between the estuaries, from 7.9 to 10.6 % and from 5.5 to 21.9 %, respectively. DOM originating from the catchment dominated by natural forests and peatlands (Kiiminkijoki) had the lowest DOC and DON degradation rates, as well as the lowest proportions of biodegradable DOC and DON. A greater proportion of agricultural land in the catchment increased the bioavailability of DON, but not the bioavailability of DOC (Kyrönjoki). Additionally, DOM quality varied significantly between the estuaries, and DOM originating from the agricultural Kyrönjoki catchment sustained higher DOC and DON degradation rates and higher bacterial growth efficiency (BGE) compared to those of the natural forest and peat dominated Kiiminkijoki catchment. The quality of DOM, indicated by differences in CDOM, fluorescent DOM and molecular weight, varied between estuaries with differing land use and was concluded to be major driver of BGE of these systems and thereafter to the microbial CO 2 fluxes from the estuaries. The differences in BGE resulted in a 5-fold difference in the calculated daily bacterial CO 2 emissions between the study's estuaries due to bacterial activity, ranging from 40 kg C d −1 in the Karjaanjoki estuary to 200 kg C d −1 in the Kyrönjoki estuary. Lower DOC : DON ratios, smaller molecular weight and higher CDOM absorption spectral slope values of DOM resulted in higher proportion of the initial DOC and DON being transferred to microbial growth and therefore to the pelagic food web. The pristine, peatland and forest-dominated Kiiminkijoki catchment had the lowest BGE, and therefore proportionally highest CO 2 fluxes.

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Section: Doc and Don Degradationcontrasting

confidence: 37%

Bioavailability of riverine dissolved organic matter in three Baltic Sea estuaries and the effect of catchment land use

et al. 2013

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“…In coastal upwelling systems, similar trends have been observed in which a high percentage of accumulated OM is partitioned into the particulate phase during exponential bloom conditions (Doval et al 1997, Wetz & Wheeler 2003, with evidence of greater DOM partitioning during later phase of the bloom (Hill & Wheeler 2002). Sintes et al (2010) assessed the seasonal variability of DOM and bacterioplankton dynamics in the coastal North Sea and observed a seasonal transition in the source of organic carbon that supported bacterial carbon demand (BCD). They demonstrated a pronounced seasonal pattern in DOM and found that extracellular release (ER) from primary production (PP) could account for BCD in spring and summer but that in winter periods the accumulated DOM was also required to partially support BCD.…”

Section: Introductionmentioning

confidence: 61%

Annual cycle of organic matter partitioning and its availability to bacteria across the Santa Barbara Channel continental shelf

Halewood¹,

Carlson²,

Brzezinski³

et al. 2012

Aquat. Microb. Ecol.

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Seasonal trends in organic matter (OM) partitioning (between the dissolved and particulate phases), dissolved inorganic nitrogen (DIN) distributions, and bacterioplankton dynamics were examined across a 3 km stretch of the Santa Barbara Channel continental shelf from January 2008 to April 2009. OM partitioning was assessed as the percentage of 14 C-primary production (PP) released as 14 C-labeled dissolved organic carbon (DOC), i.e. percent extracellular release (PER), and as the ratio of DOC and particulate organic carbon (POC) concentrations. Spring upwelling raised surface DIN concentrations, stimulating phytoplankton blooms and OM accumulation. During upwelling, PER accounted for 10 to 30%, with ~60% of OM accumulating as POC versus ~40% as DOC. After stratification and macronutrient depletion, PER increased to between 35 and 45%, and the proportion of seasonally produced DOC to total accumulated organic carbon increased to > 50%. Experiments revealed a seasonal maximum in DOC bioavailability to heterotrophic bacterioplankton during upwelling: 9 to 18% of DOC was consumed in <1 wk at bacterial growth efficiencies (BGE) of 5 to 12%. Throughout the stratified period, ≤5% of DOC was consumed in <1 wk, and the BGE increased to between 12 and 52%. Bacterial carbon demand (BCD) ranged from 0.2 to 24 µmol C l, and for most of the sampling period, PP was sufficient to meet BCD. However, at times, BCD exceeded phytoplankton PP, indicating that sources of DOC other than daily PP were used to support BCD. Similar to other coastal systems, OM is partitioned mainly into the particulate phase under nutrient-replete conditions and into the dissolved phase following stratification and the onset of oligotrophic conditions. We discuss how the partitioning of OM has consequences for bacterial metabolism and carbon cycling of this coastal system.

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“…7). This paradox seems to be widespread and has been found in other regions of the Mediterranean (Zweifel et al 1995, Cauwet et al 1997, Thingstad et al 1997, Avril 2002 and in distinct places worldwide (Carlson et al 1994, Guo et al 1995, Hansell & Carlson 1998b, Sintes et al 2010. The magnitude of the increase in DOC concentration through the seasons is not always the same.…”

Section: Discussionmentioning

confidence: 96%

“…DOC is produced through different processes, such as phytoplankton excretion, egestion and release by grazers, viral cell lysis, and the enzymatic hydrolysis of detritus and aggregates (Biddanda & Benner 1997, Biersmith & Benner 1998, Fajon et al 1999, Nagata 2000, Sintes et al 2010, and heterotrophic bacteria are the main consumers of DOC. Decoupling between production and consumption processes can cause the accumulation of DOC.…”

Section: Introductionmentioning

confidence: 99%

Seasonal dynamics and net production of dissolved organic carbon in an oligotrophic coastal environment

Vila-Reixach

Gasol²,

Cardelús³

et al. 2012

Mar. Ecol. Prog. Ser.

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To understand dissolved organic carbon (DOC) seasonal dynamics in a coastal oligotrophic site in the north-western Mediterranean Sea, we monitored DOC concentrations monthly over 3 yr, together with the meteorological data and the food-web-related biological processes involved in DOC dynamics. Additional DOC samples were taken in several inshore− offshore transects along the Catalan coast. We found DOC concentrations of ~60 µmol C l −1 in winter, with increasing values through the summer and autumn and reaching 100 to 120 µmol C l −1 in November. There was high inter-annual variability in this summer DOC accumulation, with values of 36, 69 and 13 µmol C l −1 for 2006, 2007 and 2008, respectively. The analysis of the microbial food-web processes involved in the DOC balance did not reveal the causes of this accumulation, since the only occasion on which we observed net DOC production (0.3 ± 1 µmol C l from May to October) compared with those of winter to early spring (average 0.11 ± 0.048 d −1 from November to April). Indeed, the amount of DOC accumulated each year was inversely correlated with the average summer rainfall. We hypothesize that decreased DOC turn-over due to photochemical or biological processes -mostly active during the summer -and low water renewal rate combine to determine seasonal DOC accumulation and influence its inter-annual variability. KEY WORDS: Coastal DOC · Seasonality · Primary production · Bacterial metabolism · Physical transportResale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 456: 7-19, 2012 (Zweifel et al. 1995), the north-western Mediterranean (Copin-Montégut & Avril 1993) and the Sargasso Sea (Carlson et al. 1994). Accumulated DOC can be subsequently transported by convective or mixing processes and surface currents, therefore contributing to the carbon balance of adjacent regions. The potential for DOC transfer is thus dependent on its residence time in the water and on the biological availability of the DOC pool to bacteria.In terms of its availability, DOC consists of a broad spectrum of molecules: (1) labile DOC that is readily usable by bacteria turning over in time scales of hours to days, (2) semi-labile DOC that resists rapid microbial degradation turning over on seasonal to annual time scales and (3) refractory DOC with turnover times of millennia (Carlson 2002). Some processes, such as protozoan grazing and viral lysis, are known to be particularly important in producing refractory DOC, as reported by Strom et al. (1997) and Suttle (2007). Both, the refractory nature of DOC and the limited availability of inorganic nutrients can inhibit DOC utilization by bacteria and can thus contribute to DOC accumulation (Legendre & Le Fèvre 1995, Thingstad et al. 1997. As a consequence, the composition and re fractory nature of DOC can vary depending on the trophic structure and the environmental conditions of the ecosystem . Despite the widespread occurrence of DOC accumulation in a wide variety of oceanic and coastal eco...

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Seasonal dynamics of dissolved organic matter and microbial activity in the coastal North Sea

Cited by 33 publications

References 51 publications

Bioavailability of riverine dissolved organic matter in three Baltic Sea estuaries and the effect of catchment land use

Bioavailability of riverine dissolved organic matter in three Baltic Sea estuaries and the effect of catchment land use

Annual cycle of organic matter partitioning and its availability to bacteria across the Santa Barbara Channel continental shelf

Seasonal dynamics and net production of dissolved organic carbon in an oligotrophic coastal environment

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