Nutrient Determination in the Nutrient Determination in the Belgian Coastal Waters of the Belgian Coastal Waters of the

North Sea North Sea

By By

Sheku Sei andSheku Sei and

Enyue XueEnyue Xue

11stst Year Ecomama Year Ecomama

ContentContent

1.1. IntroductionIntroduction

2.2. Sampling SiteSampling Site

3.3. Materials and MethodsMaterials and Methods

4.4. ResultResult

5.5. DiscussionDiscussion

6.6. ConclusionConclusion

IntroductionIntroduction

– The North Sea - situated on the continental shelf of northwest Europe.

– The Belgian part of the North Sea –

– 3,600 km², which is about the size of West Flanders. about half a per cent of the surface of the North Sea.

IntroductionIntroduction

• The basis of the practicalsThe basis of the practicals

• To quantify nutrient concentration from To quantify nutrient concentration from sea water samples collected at different sea water samples collected at different stations and different depthsstations and different depths

• To obtain an insight into nutrient variabilityTo obtain an insight into nutrient variability

• learn Practical techniques how and learn Practical techniques how and seasonal variationsseasonal variations

IntroductionIntroduction

• Nutrients - important for primary Nutrients - important for primary production in the seaproduction in the sea

• A limiting factor :light+low nutrient=low ppA limiting factor :light+low nutrient=low pp

• Concentrations- usually high in winter- why?Concentrations- usually high in winter- why?

• High mixing processesHigh mixing processes

• High nutrient + light =high ppHigh nutrient + light =high pp

• Light limiting factorLight limiting factor

High nutrient consumption at surface watersHigh nutrient consumption at surface waters

Sampling stationsSampling stations

Ostend

N

North Sea

Ostend

North Sea

N

Method and materialsMethod and materials• Sampling- survey cruise :Sampling- survey cruise : Research vessel ZEELEEUWResearch vessel ZEELEEUW• Sampling along the Belgian Continental ShelfSampling along the Belgian Continental Shelf• Sea water –collected –by Niskin BottlesSea water –collected –by Niskin Bottles• Samples filtered in polyethylene bottles and deep Samples filtered in polyethylene bottles and deep

frozenfrozen• Analysis done using the standard protocols of reagentsAnalysis done using the standard protocols of reagents• Equipment: spectrophotometer - absorbance Equipment: spectrophotometer - absorbance • Calibration done using different dilutions to generate Calibration done using different dilutions to generate

calibration curve –useful to determine concentrations calibration curve –useful to determine concentrations (Con. (ug/l =corrected extinction –b)/a(Con. (ug/l =corrected extinction –b)/a

• Ammonium determined immediatelyAmmonium determined immediately

Result Calibration curve -Phosphate

Phosphate Concentration in Samples

 

Station 230 Station 330 Station 435

Conc. (ug/l) Depth (m)

46.4555SD: 3.3165

3

41.9005SD: 0.0493

10

Conc. (ug/l)

Depth (m)

40.5367SD:1.007

3

40.868SD:0 .681

10

40.02 SD: 0.682

20

MeanConc. (ug/l)

Depth (m)

44.0627SD:4 .268 

3

44.556SD: 3.828

10

44.995SD: 4.102

20

Calibration Curve for Silicate

Station 230 Station 330 Station 435

Conc.(ug/l)

Depth(m)

29.826SD: 5.137

3

26.3815SD:0 .01

10

Conc.(ug/l) Depth(m)

27.705SD: 3.5260 3

22.898SD: 2.4045 10

29.459SD:7.071 20

Conc. (ug/l)

Depth(m)

22.259SD: .606 3

23.308SD:0.9390 10

22.193 

SD: 0.61420

Silicate Concentration in Samples

Calibration Curve for Ammonium

Station Mean Concentrations(ug/l)Lagoon 84.2222

SD: 1.398

230 19.870SD:4.243

330 60.611SD: 33.793

435 27.741SD:3.539

1Nb 30.056SD: 0.278

2Nb1 32.833SD: 1.690

Nbii 24.500SD: 1.470

3Nb2 

Ammonium Concentration at Various Stations

Vertical profiles PhosphateConc.(ug/l)

D(m)

20 40 60

3

10

20S 230-P

S 435P

330-P

Vertical profiles- SilicateConc. (ug/l)

D(m)

3

10

20

2040 6

0

230

330

435

DATA ANALYSISDATA ANALYSIS HypothesisHypothesis• The Waters of the North Sea has water The Waters of the North Sea has water

characteristics as that of the Atlantic characteristics as that of the Atlantic Ocean. Since the Southern bight of the Ocean. Since the Southern bight of the North Sea is part of the Atlantic Ocean, the North Sea is part of the Atlantic Ocean, the hypothesis is that during winter, nutrient hypothesis is that during winter, nutrient concentrations at different depths don’t concentrations at different depths don’t vary much with depthvary much with depth

• Null Hypothesis (HNull Hypothesis (H00) = Mean nutrient ) = Mean nutrient concentrations don’t vary significantly with concentrations don’t vary significantly with depth and at different stations.depth and at different stations.

• Alternative Hypothesis(HAlternative Hypothesis(H11) =Mean ) =Mean concentrations vary with depth and at concentrations vary with depth and at different stations.different stations.

DATA ANALYSIS- phosphateDATA ANALYSIS- phosphate• We test the difference of two means, We test the difference of two means,

assuming the concentrations are all normal assuming the concentrations are all normal and testing at the level of significance of 5% and testing at the level of significance of 5% for stations 330 at 3m and 10m:  H0: µ2 - for stations 330 at 3m and 10m:  H0: µ2 - µ1 = 0, H1: µ2 - µ1 < 0µ1 = 0, H1: µ2 - µ1 < 0

    NN1 1 = Number of samples for X = 3= Number of samples for X = 3

•     NN2 2 = Number of samples for = 3= Number of samples for = 3•   Critical point at 5% confidence interval = - Critical point at 5% confidence interval = -

1.6451.645•   Y– X - (µY– X - (µ11 -µ -µ22)H)H0 0

• = 0.1490 > - 1.645 we cannot reject H= 0.1490 > - 1.645 we cannot reject H00

• √√ss1122

/n/n11 + s + s22 22 /n /n22 Hence nutrient  Hence nutrient

concentrations at the two depths do not vary concentrations at the two depths do not vary significantlysignificantly

DATA ANALYSISDATA ANALYSIS• 2. Station 330-3m and station 330- 20m2. Station 330-3m and station 330- 20m

•   Calculated = 0.7032, which is > -1.645, we Calculated = 0.7032, which is > -1.645, we cannot reject Hcannot reject H00. Thus nutrient concentrations . Thus nutrient concentrations

at this depth do not differ greatly at this depth do not differ greatly 

• 3. Station 330 –3m and 230 –3m3. Station 330 –3m and 230 –3m

•   Calculated = 0.7032, is greater than critical p Calculated = 0.7032, is greater than critical p value. We cannot reject the null hypothesis. value. We cannot reject the null hypothesis. Hence nutrient concentrations at these stations Hence nutrient concentrations at these stations do not differ significantly do not differ significantly 

• 4. Station 330 –10m and 435 -10m.4. Station 330 –10m and 435 -10m.

•   Calculated = -1.630, which is greater than the Calculated = -1.630, which is greater than the critical point. We cannot reject null hypothesis critical point. We cannot reject null hypothesis

DATA ANALYSIS- silicateDATA ANALYSIS- silicate•   Station 330 –3m and station 330 –10mStation 330 –3m and station 330 –10m•   Calculated test value = - 1.6845 < - Calculated test value = - 1.6845 < -

1.645, we reject H0 the 1.645, we reject H0 the concentrations differ.concentrations differ.

•   Station 330 –3m and 330-20mStation 330 –3m and 330-20m•   Calculated test value = 0.3197 > -1.645, Calculated test value = 0.3197 > -1.645,

we cannot reject Null. The concentrations we cannot reject Null. The concentrations at this depth do not differ greatlyat this depth do not differ greatly

•   Station 330- 10m and station 330-20mStation 330- 10m and station 330-20m•   Calculated = 1.2644 > - 1.645, we cannot Calculated = 1.2644 > - 1.645, we cannot

reject Null, the concentrations of silicate reject Null, the concentrations of silicate do not differ greatly at these depthsdo not differ greatly at these depths..  

DATA ANALYSISDATA ANALYSIS

• Station 330- 3m and 230- 3mStation 330- 3m and 230- 3m•   Calculated test value = - 0.4814 > -1.645, we Calculated test value = - 0.4814 > -1.645, we

cannot reject Null, the concentrations at these cannot reject Null, the concentrations at these stations do not differ greatlystations do not differ greatly

•   Station 330-10m and 435 –10mStation 330-10m and 435 –10m•   Calculated test value = 0.2751 > –1.645, we Calculated test value = 0.2751 > –1.645, we

cannot reject Hcannot reject H0, 0, the concentrations of silicate the concentrations of silicate do not vary greatly at this depth.do not vary greatly at this depth.

•   Station 230 -3m and 435- 3mStation 230 -3m and 435- 3m•   Calculated test value = - 2.0732 < - 1.645, we Calculated test value = - 2.0732 < - 1.645, we

reject null hypothesis, and say that the reject null hypothesis, and say that the concentrations differ at these stations.concentrations differ at these stations.

DISCUSSIONDISCUSSION

• From the vertical profiles and from the statistical From the vertical profiles and from the statistical tests, we see that the nutrient concentrations do tests, we see that the nutrient concentrations do not vary greatly with depth though there are some not vary greatly with depth though there are some variations in the silicate concentrations for variations in the silicate concentrations for instance at stations 330 and 435 at 3m depth, and instance at stations 330 and 435 at 3m depth, and that also at stations 330-3m and 330 10 m that also at stations 330-3m and 330 10 m

• The concentrations of phosphate is high due to the The concentrations of phosphate is high due to the fact during the period we sampled, there was not fact during the period we sampled, there was not much productivity of plankton. Though there were much productivity of plankton. Though there were lots of nutrients and mixing, light was limited lots of nutrients and mixing, light was limited during that period hence light will be a limiting during that period hence light will be a limiting factor for primary production though there is factor for primary production though there is enough nutrient.enough nutrient.

Discussion 2Discussion 2

• well mixed water column and high nutrient well mixed water column and high nutrient concentrations, in the photic zone. The concentrations, in the photic zone. The concentrations slightly low at the surface at concentrations slightly low at the surface at station 330 station 330

• and high at the bottom. At station 435, the and high at the bottom. At station 435, the concentrations are a bit higher at the concentrations are a bit higher at the surface and low at the bottom. surface and low at the bottom.

• Silicate concentrations are also slightly high Silicate concentrations are also slightly high at the bottom depth. at the bottom depth.

• Such fluctuations may be due to the slower Such fluctuations may be due to the slower process of consumption by phytoplankton at process of consumption by phytoplankton at a very low rate though sunlight is light is a very low rate though sunlight is light is limited.limited.

Discussion 3Discussion 3• The concentration of ammonium is very high in The concentration of ammonium is very high in

the Spuikom lagoon. the Spuikom lagoon.

• May be due to waste disposal in to the lagoonMay be due to waste disposal in to the lagoon

• Ammonium not taken up by phytoplanktonAmmonium not taken up by phytoplankton

• Excretion processes of zooplanktonExcretion processes of zooplankton

• The high concentration of ammonium at the The high concentration of ammonium at the different stations, Nb stations and stations 230, different stations, Nb stations and stations 230, 330, 435, are all as a result of the fact that 330, 435, are all as a result of the fact that enormous quantity of ammonium is discharged enormous quantity of ammonium is discharged in to the sea from rivers from industrial and in to the sea from rivers from industrial and agricultural sources, from estuaries like the agricultural sources, from estuaries like the Scheldt. Scheldt.

CONCLUSIONCONCLUSION •The trend of vertical distribution of

silicate and phosphate are similar at station 435 and 230,

• low concentrations at the surface and high at mid depth and bottom, at station 330 the fluctuation also vary with high concentration at the surface and low at mid depth.

•These are due to the mixing of the water column and the fluctuations in the photosynthetic activities, which is dependent on as when light is available.

CONCLUSIONCONCLUSION• High mixing takes place, the bottom is

close to isothermal. Where nutrient concentrations are low it is due to the utilization by during photosynthesis

• Seasonal changes in nutrient concentration most evident in the temperate area.

• expected productivity - higher during spring - enough light, enough nutrient- diatom bloom in the North Sea.

• The period of study was faced with light limitation.

Danke Zier Danke Zier Gut!Gut!