HELSINKI COMMISSION HELCOM CORE EUTRO 5/2012

Workshop on development of core eutrophication indicators Fifth Meeting Berlin, Germany, 13-14 March 2012

Note by Secretariat: FOR REASONS OF ECONOMY, THE DELEGATES ARE KINDLY REQUESTED TO BRING THEIR OWN COPIES OF THE DOCUMENTS TO THE MEETING Page 1 of 1

Agenda Item 4 Updating of chlorophyll a, Secchi depth and nutrient core indicators with 2006-2010 data

Document code: 4/6

Date: 09.03.2012

Submitted by: Finland

REMOTE SENSING BASED CHLOROPHYLL A EQR-CLASSIFICATION FOR THE BALTIC SEA

The fourth intersessional workshop of HELCOM MONAS on the development of HELCOM core eutrophication indicators (HELCOM CORE EUTRO 4/2011) welcomed the development of a draft indicator on chlorophyll-a status in the open sea areas of the Baltic Sea based on

remote sensing data which was elaborated by SYKE. The meeting noted that the draft indicator was based on data for the year 2011, recognizing that this was a first step for developing a core chlorophyll-a indicator based on remote sensing data. The meeting also

took note that SYKE have remote sensing data back to the year 2005 and welcomed the possibility that SYKE might be able to back-calculate and update the chlorophyll-a indicator using a five-year average, provided the availability of resources (paragraphs 4.17 & 4.19, Minutes of the meeting).

HELCOM CORE EUTRO 4/2011 appreciated the development in producing a chlorophyll-a indicator based on remote sensing data and invited SYKE to present a further developed indicator to the spring meeting of HELCOM MONAS 16/2012, taking into account the discussions held during the Meeting.

The attached document presents an updated indicator on chlorophyll-a status in the Baltic

Sea open sea areas, based on remote sensing data for 2010 and 2011.

The Meeting is invited to consider the updated draft indicator report and to provide feedback that should be taken into account when further developing the indicator.

REMOTE SENSING BASED CHLOROPHYLL A EQR-CLASSIFICATION FOR THE BALTIC SEA

Preliminary study for the Helsinki Commission, 8.3.2012 Saku Anttila, Finnish Environment Institute (SYKE)

Remote sensing based weekly chlorophyll a (chl-a) composite products from the

summer months of 2010 and 2011 were used to calculate areal statistics for the

specific open sea areas in the Baltic Sea. A chl-a based Ecological Quality Ratio (EQR)

classification for the open sea areas were derived by using this data. Overall aim was

to study the possibilities of remote sensing applications in eutrophication assessment

of the Baltic Sea. Work was conducted at Finnish Environment Institutes (SYKE) in co-

operation with the Helsinki Commission (HELCOM).

DATA SETS AND METHODS

GIS-data delineating the different open sea areas were used to extract pixels values from the

remote sensing based weekly chlorophyll a composite products from the summer months (Jun-

Sep) of 2010 and 2011. Extracted pixel values were then used to calculate areal statistics

(including mean, median, minimum, maximum, standard deviation, coefficient of variation and

10% and 90% percentiles) for each week and the open sea area. EQR-index values were derived

by dividing the area specific chl-a reference value with the area-temporal mean of chl-a (mean of

areal means from weekly chl-a products from Jun-Sep and years 2010-2011). Furthermore, time

series of chlorophyll a for the each open sea area with areal standard deviation were generated

from the collected statistics. The area specific high and poor EQR levels are also presented in the

time series graphs.

Processing flow is generally presented in the end of this document (Appendix 1). More information

on SYKEs remote sensing products can be found at

http://wwwi4.ymparisto.fi/i4/eng/chl_a/2011/chl_a_sat_2011_eng.html.

RESULTS

Figure 1. Chlorophyll a EQR classification map for the open sea areas based on the remote sensing data from the

summer months (Jun-Sep) of 2010 and 2011.

A-CHLOROPHYLL TIME SERIES FOR 2011 AND OPEN SEA AREAS IN BALTIC SEA

Figure 2. Chlorophyll a time series for the open sea areas of Bothnian Bay (A) and Quark (B) and for the years 2010-

2011. Each observation in time series indicates the areal mean from the weekly composite product derived with

remote sensing. Error bars shows the spatial variation within the open sea area. Red dashed line indicates the level of

Bad EQR status in chl-a units and blue the level of Good-status. With black dashed line the two year spatio-temporal

mean from the open sea area are shown.

Figure 2. Chlorophyll a time series for the open sea areas of Bothnian Sea (A) and Åland Sea (B) and for the years

2010-2011. Each observation in time series indicates the areal mean from the weekly composite product derived with

remote sensing. Error bars shows the spatial variation within the open sea area. Red dashed line indicates the level of

Bad EQR status in chl-a units and blue the level of Good-status. With black dashed line the two year spatio-temporal

mean from the open sea area are shown.

A B

A B

Figure 2. Chlorophyll a time series for the open sea areas of Northern Baltic Proper (A) and Gulf of Finlad (B) and for

the years 2010-2011. Each observation in time series indicates the areal mean from the weekly composite product

derived with remote sensing. Error bars shows the spatial variation within the open sea area. Red dashed line

indicates the level of Bad EQR status in chl-a units and blue the level of Good-status. With black dashed line the two

year spatio-temporal mean from the open sea area are shown.

Figure 2. Chlorophyll a time series for the open sea areas of Western Gotland Basin (A) and Eastern Gotland Basin (B)

and for the years 2010-2011. Each observation in time series indicates the areal mean from the weekly composite

product derived with remote sensing. Error bars shows the spatial variation within the open sea area. Red dashed line

indicates the level of Bad EQR status in chl-a units and blue the level of Good-status. With black dashed line the two

year spatio-temporal mean from the open sea area are shown.

A B

A B

Figure 2. Chlorophyll a time series for the open sea areas of Bornholm Basin (A) and Gulf of Riga (B) and for the years

2010-2011. Each observation in time series indicates the areal mean from the weekly composite product derived with

remote sensing. Error bars shows the spatial variation within the open sea area. Red dashed line indicates the level of

Bad EQR status in chl-a units and blue the level of Good-status. With black dashed line the two year spatio-temporal

mean from the open sea area are shown.

Figure 2. Chlorophyll a time series for the open sea areas of Gdansk Deep (A) and Arkona Basin (B) and for the years

2010-2011. Each observation in time series indicates the areal mean from the weekly composite product derived with

remote sensing. Error bars shows the spatial variation within the open sea area. Red dashed line indicates the level of

Bad EQR status in chl-a units and blue the level of Good-status. With black dashed line the two year spatio-temporal

mean from the open sea area are shown.

A B

B A

APPENDIX 1.

Figure 1. Chlorophyll-a weekly composites from summer months of 2010 and 2011 with open sea areas GIS

data (A) were used to calculate the areal statistic for each open sea area (B). Statistics were used to derive

time series for each AoI (C). Remote sensing data based EQR classification (C) was calculated by dividing the

area specific reference concentration with the area-temporal chl-a mean.