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Katarzyna Matuszewska

University of Gdansk, Institute of Oceanography Department of Marine Chemistry and Marine Environment Protection. THE IMPACT OF THE BOTTOM TRAWLING ON NUTRIENTS EXCHANGE BETWEEN SEDIMENT AND OVERLYING WATER IN THE GULF OF GDANSK. Katarzyna Matuszewska

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Katarzyna Matuszewska

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  1. University of Gdansk, Institute of Oceanography Department of Marine Chemistry and Marine Environment Protection THE IMPACT OF THE BOTTOM TRAWLING ON NUTRIENTS EXCHANGE BETWEEN SEDIMENT AND OVERLYING WATER IN THE GULF OF GDANSK Katarzyna Matuszewska Dorota Burska, Bożena Graca, Dorota Pryputniewicz, Izabela Białkowska Jerzy Bolałek Costing the impact of demersal fishing on marine ecosystem processes and biodiversity Q5RS-2001-00993) ELOISE, Portorož, November 14-18, 2004

  2. Gulf of Gdansk • a eutrophic, first-order estuary of the Vistula (one of the largest rivers discharging into the Baltic Sea) • salinity : 7 to 8 PSU (uniform to a depth of 60-70 m) A halocline occurs below the depth of 70 m, separating the upper isohaline water from more saline (10-13PSU) bottom water usually suffering from oxygen deficit • seasonal thermal stratification • 65% of the bottom is covered by muddy – silty sediments; at the rest of the bottom sandy sediments occur (Szczepańska T., Uścinowicz Sz., 1994; Witek et al., 2003)

  3. Baltic field experiments: Baltic Sea 19 - 28.03.2003, 23.06 – 2.07.2003 54.7 ° Site 4 Site 1 80m UD4 UN4 Sampling area UN1 Site 2 UN2 UD1 - trawled stations - controlstations UD2 - Fairawayarea (untrawled) 54.5 ° Site- corresponding pair of control and trawled station Site 3 UN3 60m UD3 30m 20m 10m 5 Nm Vistula river 54.3 ° 18.75 ° 19 ° 19.25 ° 19.5 °

  4. Environmental parameters measurements: • Sediment: Corg, Ntot (Hedges and Stern, 1984), P forms (Jensen and Thamdrup,1993), chlorphyll a (Edler, 1979, Parsons et al., 1985), grain size, humidity (drying to the constant mass at 105oC),LOI (ignition at 450oC) • Near-bottom water : salinity, temperature, oxygen, biogenic substances (Grasshoff et al. 1983) • Pore water: biogenic substances (Grasshoff et al. 1983)

  5. The sediment-water nutrient fluxes were calculated from the equation: NF = (C - C0)*F*103 / A*Mw where NFis the nutrient flux (µmolm-2h-1) Cis the concentration of nutrient in the water entering the core (mgkg-1) C0is the concentration of nutrient in the water leaving the core (mgkg-1) Fis the flow of water through the core (kgh-1) Ais the area of the core (m2) Mwis the molecular weight of nutrient ion

  6. sandy silt silt mg g-1 d.s. mg g-1 d.s. mg g-1 d.s. mg g-1 d.s. % % silty sand Hel Peninsula mg g-1 d.s. mg g-1 d.s. The Vistula % UN1,UD1 UN2, UD2 UN4UD4 UN3UD3

  7. Hel Peninsula The Vistula UN1,UD1 UN2, UD2 UN4UD4 UN3UD3

  8. Hel Peninsula The Vistula UN1,UD1 UN2, UD2 UN4UD4 UN3UD3

  9. Hel Peninsula The Vistula UN1,UD1 UN2, UD2 UN4UD4 UN3UD3

  10. The U-Mann Whitney’s test and Principal Component Analysis (PCA) were used to test the hypothesis: Trawling impacts in a significant way the exchange of nutrients and oxygen at the water-sedimentinterface.

  11. The differences in the fluxes between the hole set of control and traweled stations (regardless of geographic position and season) were significant (p<0.05) for silicates, oxygen and nitrites.

  12. Principal component analysis

  13. June March

  14. Component I Component II Component III fluxes NH4+ 0.43 -0.35 -0.71 NO2- -0.58 0.51 -0.36 NO3- -0.15 0.89 0.02 oxygen -0.23 0.08 0.70 PO43- 0.85 0.22 -0.19 SiO44- 0.78 0.17 -0.30 bottom waters oxygen 0.25 -0.86 -0.10 salinity 0.18 0.89 0.14 temperature -0.80 0.24 0.02 sediments organic carbon 0.08 0.09 0.86 interstitial waters PO43- -0.03 -0.02 0.72 NO3- + NO2- 0.14 0.42 0.07 Content (%) 31 21 17 Principal component analysis

  15. U3, U4 TRAWLED AND CONTROL U1, U2 TRAWLED AND CONTROL

  16. Component I Component II Component III fluxes NH4+ 0.43 -0.35 -0.71 NO2- -0.58 0.51 -0.36 NO3- -0.15 0.89 0.02 oxygen -0.23 0.08 0.70 PO43- 0.85 0.22 -0.19 SiO44- 0.78 0.17 -0.30 bottom waters oxygen 0.25 -0.86 -0.10 salinity 0.18 0.89 0.14 temperature -0.80 0.24 0.02 sediments organic carbon 0.08 0.09 0.86 interstitial waters PO43- -0.03 -0.02 0.72 NO3- + NO2- 0.14 0.42 0.07 Content (%) 31 21 17 Principal component analysis

  17. Corg= 40 mg g-1 (33-57 mg g-1) U4 U1, U2 Corg= 61 mg g-1 (53-73 mg g-1) U3 Corg= 16 mg g-1 (10-27 mg g-1)

  18. Component I Component II Component III fluxes NH4+ 0.43 -0.35 -0.71 NO2- -0.58 0.51 -0.36 NO3- -0.15 0.89 0.02 oxygen -0.23 0.08 0.70 PO43- 0.85 0.22 -0.19 SiO44- 0.78 0.17 -0.30 bottom waters oxygen 0.25 -0.86 -0.10 salinity 0.18 0.89 0.14 temperature -0.80 0.24 0.02 sediments organic carbon 0.08 0.09 0.86 interstitial waters PO43- -0.03 -0.02 0.72 NO3- + NO2- 0.14 0.42 0.07 Content (%) 31 21 17 Principal component analysis

  19. U-Mann Whitney’s Test p<0.05

  20. Conclusion In the majority of cases, trawling resulted in decreased oxygen consumption and the fluxes of ammonia, phosphate and silicate from the sediment. This might be a combined result of a short-term intensive release of nutrients from the sediment immediately after trawling, and a long-term effect caused by better oxygen conditions inside the sediment. The changes on benthic ecosystem caused by trawling depend on many factors such as marine sediment characteristics, intensity and area of trawling and period of the year.

  21. THANK YOU

  22. U-Man Whitney’s Test p<0.05 3,28% 52,68% DECREASE 19,89% 59,85% 29,38% 23,84% 23,91% 11,17% 40,77%

  23. date station h [m] O2 [cm3 dm-3] T [Co] S [PSU] UN1 UD1 UN2 UD2 UN3 UD3 UN4 UD4 65 65 66 65 62 62 76 75 9,75 9,75 9,95 10,04 5.15 5,07 2,48 2,50 2,25 2,37 2,18 2,25 6,34 6,44 6,88 6,71 7,24 7,25 7,23 7,23 9,98 10,10 11,19 11,13 UN1 UD1 UN2 UD2 UN3 UD3 UN4 UD4 65 65 66 65 62 62 76 75 7,82 7,52 7,37 7,48 5,06 4,80 5,13 5,31 8,10 8,33 9,00 8,05 3,62 3,69 3,74 3,73 7,17 7,21 7,17 7,27 9,35 9,39 10,22 9,95 Location of sampling stations ( trawled andcontrol) Spring 24.03 21.03 UN1 UD4 UN4 UN2 UD1 Summer 01.07 23.06 UD2 UN3 UD3 Temperature, salinity and oxygen concentration in near-bottom water

  24. schemat systemu przepływowego cienki wąż transferowy z tygonu o średnicy 2 mm stoper przeciwdziałający zanieczyszczeniu z powietrza marprenowy wąż o średnicy 1,15 mm (Watson-Marlow) pomiar temperatury oraz tlenu plastikowa pokrywa Pompa perystaltyczna Watson Marlow nylonowa nić mały magnetyczny walec 1-2 cm nad osadem kabel do urządzenia sterującego TANK 300 l wody nadddennej z rejonu badań 7,6 cm PC-rdzeń z osadem (h = ~29 cm) i wodą (h =~20 cm)

  25. założenia ekspetrymentu • nienaruszone rdzenie • rdzenie o zbliżonej wysokości słupa wody, • stała temperatura w inkubowanych rdzeniach oraz tanku, • stały przepływ ~ 1ml/min • mieszanie nad osadem, • ustalenie stanu równowagi, przebieg ekspetrymentu • codziennie, o stałej porze, w każdym rdzeniu oraz w tanku następuje: • pomiar przepływu, • pomiar temperatury i stężenia tlenu, • pobieranie 150 ml wody do analizy substancji biogenicznych,

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