THE IMPACT OF THE BOTTOM TRAWLING THE IMPACT OF THE BOTTOM TRAWLING ON NUTRIENTS EXCHANGE BETWEEN ON NUTRIENTS EXCHANGE BETWEEN

SEDIMENT AND OVERLYING WATER IN SEDIMENT AND OVERLYING WATER IN THE THE GULF OF GDANSKGULF 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

University of Gdansk, Institute of OceanographyUniversity of Gdansk, Institute of Oceanography

Department of Marine Chemistry and Marine Environment ProtectionDepartment of Marine Chemistry and Marine Environment Protection

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)

18.75 ° 19 ° 19.25 ° 19.5 °

54.3 °

54.5 °

54.7 °

5 Nm

Baltic Sea

10m

20m

30m

60m

80m

Sampling area

Baltic field experiments:19 - 28.03.2003,

23.06 – 2.07.2003

- Fairaway area (untrawled)

Site 1

Site 2

Site 3

Site 4

- trawled stations

UD1

UD2

UD3

UD4

- control stations

UN1

UN2

UN3

UN4

Vistula river

Site- corresponding pair of control and trawled station

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)

The sediment-water nutrient fluxes were calculated from the equation:

NF = (C - C0)*F*103 / A*Mw where

NF is the nutrient flux (µmol m-2 h-1)C is the concentration of nutrient in the water entering the core (mg kg-1)C0 is the concentration of nutrient in the water leaving the core (mg kg-1)F is the flow of water through the core (kg h-1)A is the area of the core (m2)Mw is the molecular weight of nutrient ion

The

Vis

tula

Hel Peninsula

UN1,UD1UN2, UD2

UN3UD3

UN4UD4

0 20 40 60 80 100

Corg

Ntot

0 20 40 60 80 100

Porg

Chl-a

0 20 40 60 80 100

LOI

H

sandy silt

mg g-1 d.s.

g g-1 d.s.

%

silty sand

mg g-1 d.s.

g g-1 d.s.

%

0 20 40 60 80 100

Corg

Ntot

silt

g g-1 d.s.

mg g-1 d.s.

%

0 20 40 60 80 100

Corg

Ntot

0 20 40 60 80 100

Porg

Chl-a

0 20 40 60 80 100

LOI

H

0 20 40 60 80 100

Porg

Chl-a

0 20 40 60 80 100

LOI

H

The

Vis

tula

Hel Peninsula

UN1,UD1UN2, UD2

UN3UD3

UN4UD4

Phosphate [mol dm-3]

-20

-15

-10

-5

0

0 50 100 150 200 250 300 350

de

pth

[c

m]

mean

Phosphate [mol dm-3]

-20

-15

-10

-5

0

0 50 100 150 200 250 300 350

de

pth

[c

m]

mean

Phosphate [mol dm-3]

-20

-15

-10

-5

0

0 50 100 150 200 250 300 350

de

pth

[c

m]

mean

The

Vis

tula

Hel Peninsula

UN1,UD1UN2, UD2

UN3UD3

UN4UD4

Ammonium [mol dm-3]

-20

-15

-10

-5

0

0 400 800 1200 1600 2000 2400

de

pth

[c

m]

mean

Ammonium [mol dm-3]

-20

-15

-10

-5

0

0 400 800 1200 1600 2000 2400

de

pth

[c

m]

mean

Ammonium [mol dm-3]

-20

-15

-10

-5

0

0 400 800 1200 1600 2000 2400

de

pth

[c

m]

mean

The

Vis

tula

Hel Peninsula

UN1,UD1UN2, UD2

UN3UD3

UN4UD4

Silicate [mol dm-3]

-20

-15

-10

-5

0

0 250 500 750 1000

de

pth

[c

m]

mean

Silicate [mol dm-3]

-20

-15

-10

-5

0

0 250 500 750 1000

de

pth

[c

m]

mean

Silicate [mol dm-3]

-20

-15

-10

-5

0

0 250 500 750 1000

de

pth

[c

m]

mean

-20

-15

-10

-5

0

0 50 100 150 200 250 300

phosphate [mol dm-3]d

epth

[cm

]

trawled control

-20-15-10

-50

0 300 600 900silicate [mol dm-3]

de

pth

[c

m]

trawled control

-20

-15

-10

-5

0

0 100 200 300 400 500

ammonium [mol dm-3]

dep

th [

cm]

trawled control

Ammonium flux

[microM m-2 h-1]

-350-300-250-200-150-100-50

050

100

trawled control

Phosphate flux [microM

m-2 h-1]

-250

-150

-50

50

150

trawled control

Silicate flux [microM m-2

h-1]

-700-600-500-400-300-200-100

0

trawled control

Oxygen consumption

[microM m-2 h-1]

0500

100015002000250030003500

trawled control

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-sediment interface.

NIT

RIT

E [

mic

roM

m-2

h-1

]

-12

-8

-4

0

4

TRAWLED CONTROL

OX

YG

EN

[m

icro

M m

-2h

-1]

1000

2000

3000

4000

TRAWLED CONTROL

SIL

ICA

TE

[m

icro

M m

-2h

-1]

-900

-600

-300

0

TRAWLED CONTROL

Min-Maks.25%-75%Mediana

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.

Principal component analysis

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 PO4

3--0.03 -0.02

0.72

NO3- + NO2

- 0.14 0.42 0.07

Content (%) 31 21 17

principal component I (season)

pri

nci

pal

com

pon

ent

II (

regi

on)

-2,0

-1,5

-1,0

-0,5

0,0

0,5

1,0

1,5

2,0

2,5

-2,5 -2,0 -1,5 -1,0 -0,5 0,0 0,5 1,0 1,5 2,0

JuneMarch

Principal component analysis

17 21 31Content (%)

0.07 0.42 0.14 NO3- + NO2

-

0.72-0.02-0.03

interstitial waters PO4

3-

0.86

0.09

0.08

sediments organic carbon

0.02 0.24-0.80 temperature

0.14 0.89 0.18 salinity

-0.10-0.86

0.25bottom waters oxygen

-0.30 0.17 0.78 SiO44-

-0.19 0.22 0.85 PO43-

0.70 0.08-0.23 oxygen

0.02 0.89-0.15 NO3-

-0.36 0.51-0.58 NO2-

-0.71-0.35 0.43

fluxes NH4

+

Component IIIComponent IIComponent I

principal component I (season)

pri

nci

pal

com

pon

ent

II (

regi

on)

-2,0

-1,5

-1,0

-0,5

0,0

0,5

1,0

1,5

2,0

2,5

-2,5 -2,0 -1,5 -1,0 -0,5 0,0 0,5 1,0 1,5 2,0

U1, U2

TRAWLED AND CONTROL

U3, U4

TRAWLED AND CONTROL

Principal component analysis

17 21 31Content (%)

0.07 0.42 0.14 NO3- + NO2

-

0.72-0.02-0.03

interstitial waters PO4

3-

0.86

0.09

0.08

sediments organic carbon

0.02 0.24-0.80 temperature

0.14 0.89 0.18 salinity

-0.10-0.86

0.25bottom waters oxygen

-0.30 0.17 0.78 SiO44-

-0.19 0.22 0.85 PO43-

0.70 0.08-0.23 oxygen

0.02 0.89-0.15 NO3-

-0.36 0.51-0.58 NO2-

-0.71-0.35 0.43

fluxes NH4

+

Component IIIComponent IIComponent I

principal component II (region)

pri

nci

pal

com

pon

ent

III

(ch

emic

al c

omp

osit

ion

)

-2,5

-2,0

-1,5

-1,0

-0,5

0,0

0,5

1,0

1,5

2,0

-2,0 -1,5 -1,0 -0,5 0,0 0,5 1,0 1,5 2,0 2,5

U1, U2 U4

U3

Corg= 40 mg g-1

(33-57 mg g-1)

Corg= 61 mg g-1

(53-73 mg g-1)

Corg= 16 mg g-1

(10-27 mg g-1)

Principal component analysis

17 21 31Content (%)

0.07 0.42 0.14 NO3- + NO2

-

0.72-0.02-0.03

interstitial waters PO4

3-

0.86

0.09

0.08

sediments organic carbon

0.02 0.24-0.80 temperature

0.14 0.89 0.18 salinity

-0.10-0.86

0.25bottom waters oxygen

-0.30 0.17 0.78 SiO44-

-0.19 0.22 0.85 PO43-

0.70 0.08-0.23 oxygen

0.02 0.89-0.15 NO3-

-0.36 0.51-0.58 NO2-

-0.71-0.35 0.43

fluxes NH4

+

Component IIIComponent IIComponent I

NH4+ NO2

- NO3- oxygen PO4

3- SiO44-

March U1, U2 T -78.60 -5.78 -44.58 2985.21 -4.96 -229.80

C -43.01 -1.54 -37.95 2744.47 -1.06 -210.84

U3 T -23.73 0.60 39.72 2479.65 5.01 -110.48

C -25.18 -0.15 41.60 2551.87 4.84 -107.90

U4 T -198.60 -0.15 75.42 2840.76 1.70 -122.48

C -297.59 0.32 74.78 2937.06 -5.40 -258.85

June U1, U2 T -101.1 0.77 9.50 2327.18 -41.51 -248.97

C -161.97 0.91 9.50 2904.96 -103.39 -619.62

U3 T -31.30 0.12 5.49 1845.69 -8.88 -380.61

C -41.30 0.45 6.83 2423.48 -7.87 -538.95

U4 T -229.48 0.09 6.62 2953.11 -71.31 -463.90

C -283.85 0.23 6.48 3009.28 -57.37 -609.69

All data

T -74.76 0.00 6.46 2551.87 -6.55 -229.80

C -106.80 0.16 9.50 2872.86 -8.01 -387.96

U-Mann Whitney’s Test p<0.05

-20

-15

-10

-5

0

0 50 100 150 200 250 300

phosphate [mol dm-3]d

epth

[cm

]

trawled control

-20-15-10

-50

0 300 600 900silicate [mol dm-3]

de

pth

[c

m]

trawled control

-20

-15

-10

-5

0

0 100 200 300 400 500

ammonium [mol dm-3]

dep

th [

cm]

trawled control

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.

THANK YOU

NH4+ NO2

- NO3- oxygen PO4

3- SiO44-

March U1, U2 T -74.80 -5.78 -44.58 2985.21 -4.96 -229.80

C 3.93 -1.54 -37.95 2744.47 -1.06 -210.84

U3 T -23.73 0.60 39.72 2479.65 5.01 -112.48

C -25.18 -0.15 41.60 2551.87 4.84 -90.90

U4 T -198.60 -0.15 75.42 2840.76 1.70 -122.48

C 297.59 0.32 74.78 2937.06 -5.40 -258.85

June U1, U2 T -172.45 0.77 9.50 2327.18 -41.51 -248.97

C -161.97 0.91 9.50 2904.96 -103.39 -619.62

U3 T -41.30 0.12 -0.15 1845.69 -8.88 -380.61

C -41.30 0.45 6.53 2423.48 -7.87 -538.95

U4 T -293.48 -0.09 6.62 2953.11 -71.31 -463.90

C -263.85 0.23 6.48 3009.28 -57.37 -609.69

All data

T -74.76 0.00 6.46 2551.87 -6.55 -229.80

C -106.80 0.16 9.50 2872.86 -8.01 -387.96

U-Man Whitney’s Test p<0.05

52,68%

29,38%

23,91%

59,85%

3,28%

19,89%

23,84%

DECREASE

40,77%11,17%

UN1 UN2

UN4

UN3

UD4

UD3

UD2UD1

7,82

7,52

7,37

7,48

5,06

4,80

5,13

5,31

9,75

9,75

9,95

10,04

5.15

5,07

2,48

2,50

O2

[cm3 dm-3]

7,17

7,21

7,17

7,27

9,35

9,39

10,22

9,95

8,10

8,33

9,00

8,05

3,62

3,69

3,74

3,73

65

65

66

65

62

62

76

75

UN1

UD1

UN2

UD2

UN3

UD3

UN4

UD4

65

65

66

65

62

62

76

75

h

[m]

7,24

7,25

7,23

7,23

9,98

10,10

11,19

11,13

2,25

2,37

2,18

2,25

6,34

6,44

6,88

6,71

UN1

UD1

UN2

UD2

UN3

UD3

UN4

UD4

S [PSU]T

[Co]

stationdateS

pri

ng

24.0

3

21.

03

Su

mm

er01

.07

2

3.06

Temperature, salinity and oxygen concentration in near-bottom water

Location of sampling stations

( trawled and control)

stoper przeciwdziałający zanieczyszczeniu z powietrza

pomiar temperatury oraz tlenu

plastikowa pokrywa

mały magnetyczny walec 1-2 cm nad osadem

nylonowa nić

Pompa perystaltycznaWatson Marlow

marprenowy wąż o średnicy 1,15 mm (Watson-Marlow)

cienki wąż transferowy z tygonu o średnicy 2 mm

TANK300 l wody nadddennej z rejonu badań

7,6 cm PC-rdzeń z osadem (h = ~29 cm) i wodą (h =~20 cm)

kabel do urządzenia sterującego

schemat systemu przepływowego

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,

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,

przebieg ekspetrymentu