SNOOP
This presentation is the property of its rightful owner.
Sponsored Links
1 / 11

SNOOP PowerPoint PPT Presentation


  • 68 Views
  • Uploaded on
  • Presentation posted in: General

SNOOP. The effect of ship Nox deposition on cyanobacteria blooms. Marine Systems Institute at Tallinn University of Technology. Urmas Raudsepp. Aim. Additional atmospheric deposition of nitrogen caused by shipping likely

Download Presentation

SNOOP

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Snoop

SNOOP

The effect of ship Nox deposition on cyanobacteria blooms

Marine Systems Institute at Tallinn University of Technology

Urmas Raudsepp


Snoop

Aim

Additional atmospheric deposition of nitrogen caused by shipping likely

result in changes of phytoplankton spring bloom and summer nitrogen-fixing

cyanobacteria bloom dynamics.

The task was to assess the degree of inter-annual variability of

spring and summer phytoplankton blooms and nitrogen fixation in

response to a shipnitrogen deposition on the background of

natural variability of environmental conditions in the Gulf of Finland.

Two 10-year runs with coupled3D physical and biological-chemical model were

performed using atmospheric deposition of NOx without ship deposition and including

ship deposition (year 2008).


Snoop

3D physical (GETM) and biological-chemical model (ERGOM)

Model domain was the whole Baltic Sea

Model domain

Gulf of Finland

Blue line B along longitude 23º30’E marks the western boundary of the Gulf of

Finland basin in the present study


Snoop

Model validation (monitoring station LL7)

D is mean of observations

M is mean of simulated data

SD is standard deviation

CFis cost function

Cost function definition (Eilola et al. 2009):

CF =|(M–D)/SD|

SD is standard deviation of observations

Cost function values:

0–1 indicate good result,

1–2 indicate reasonable result

and >2 indicate poor result.

The 10-year mean, standard deviation and cost function values of temperature (T, ºC), salinity (S), dissolved oxygen (O, ml l–1), nitrate (N, mmol m–3), phosphate (P, mmol m–3) for the surface (s) and near-bottom (b) layers and chlorophyll (Chl, mg m–3).


Snoop

Atmospheric and ship NOx deposition to the Gulf in 2008

Monthly atmospheric NOx deposition (t N month–1) without ship deposition (black bars)

and ship NOx deposition (t N month–1) (shaded bars) to the Gulf of Finland area in 2008.

Annual atmospheric NOx deposition was 13.7 kton and ship NOx deposition

1.6 kton to the Gulf of Finland area.Annual ships NOx deposition is about 12%

from total atmospheric deposition.Ship NOx deposition is highestin May, June,

July and August(20-30%).


Snoop

Annual ship NOx deposition to the Gulf of Finland area (year 2008).

Distribution of annual ship NOx deposition (kg N km–2 y–1) to the Gulf of Finland area.

The annual ship NOx deposition was larger in the western and central Gulf

(up to 70 kg N km–2 y–1) compared to the eastern part (10-40 kg N km–2 y–1).


Snoop

Winter nutrient conditions in the Gulf of Finlandupper layer

Mean winter ratio of dissolved inorganic nitrogen

to phosphorus (DIN:DIP) in the upper 10-m water

column.

DIN:DIP ratio was low, varying inter-annually

from 8.5 to 11.5.

The increase of DIN:DIP ratio caused by ship

NOx deposition was minor (about 1%)

compared with natural variability.

Mean winter excess phosphate (eP=DIP–DIN/16)

in the upper 10-m layer.

Black bars show excess phosphate without ship

NOx deposition and shaded bars show excess

phosphate ship NOx deposition included.

The addition of ship NOx deposition reduced

excess phosphate from 1 to 2.5% depending

on DIN and DIP resources in the upper layer.


Snoop

Annual phytoplankton primary production and nitrogen fixation

by cyanobacteria (in nitrogen units).

phytoplankton

cyanobacteria

Annual primary production of phytoplankton over the Gulf area.

Green bars indicate phytoplankton production and blue bars nitrogen fixation by cyanobacteria.

Simulations performed without ship NOx deposition.

Note different scales.


Snoop

Impact of ship NOx deposition on the phytoplankton primary production

and nitrogen fixationby cyanobacteria

phytoplankton

cyanobacteria

Changes of the annual phytoplankton primary production (green bars) and

cyanobacteria nitrogen fixation (blue bars) caused by ship NOx deposition in

the Gulf water column.

Changes are calculated:

primary production with ships−primary production without ships

nitrogen fixation with ships − nitrogen fixation without ships.


Snoop

10-year mean decrease of nitrogen fixation rate in the Gulf

Distribution of 10-year mean decreaseof nitrogen fixation rate

(ship NOx deposition included–without ship NOx deposition) in the Gulf of Finland

Annual averaged nitrogen fixation over the Gulf area was 1300 kg N km-2 y-1


Snoop

Conclusions

  • The annual ship NOx deposition was about 1.6 kt N y–1 i.e. 12% from annual atmospheric deposition.

  • Ship NOx deposition was larger during summer months when the relative importance is about 20-30%.

  • Ship NOx deposition caused the increase of spring bloom and post bloom biomass phytoplankton biomass (~1%) reducing at the same time phosphate resources.

  • Ship NOx deposition causes the decrease of nitrogen fixation about 2-6%. Thus the increase of the Gulf nitrogen pool caused by the additional ship NOx deposition to the Gulf was partly compensated by the decrease of nitrogen fixation.

  • The effect of ship NOx deposition on cyanobacteria bloom was larger in the westernand centralGulf of Finland.

  • No trend in phytoplankton primary production and nitrogen fixation due to accumulation of ship NOx deposition in the Gulf water column was observed.

The 10-year simulation with coupled hydrodynamic and ecological model

forced by ship NOx deposition showed changes in the dynamics of

phytoplankton spring bloom and summer N-fixing cyanobacteria bloom.

Due to the phytoplankton composition (green algae+cyanobacteria) the

annualtotal biomass in the Gulf is actually limited by phosphorus, i.e. the

increase of green algae primary production is practically compensated

by the decrease of nitrogen fixation by cyanobacteria.


  • Login