Report on field sampling in Sozopol in September 2009 and June 2010 and future activities

By Prof. Marianne Holmer and Ph.D. student Katrina Povidisa, Institute of Biology, University of Southern Denmark

Date: July 5, 2010

Status of Zostera meadows in impacted and relatively undisturbed sites (sediments,water and community)

  1. List of planed actions (sampling, measurements etc.) versus real performed actions

№ / Planned Activity / Partner / Performed activities
1 / Stations setup, initial site mapping and survey / CLGE, Bulgaria
Institute of Botany, Bulgaria
Institute of Biology, Denmark / 4 stations were established along a gradient from sewage outlet to pristine conditions
2 / Sample collection
- Zostera meadows, soft bottom sediments, and water column
- / CLGE, Bulgaria
Institute of Botany, Bulgaria
Institute of Biology, Denmark / Seagrasses, sediments and water column were sampled at all 4 stations during September 2009 and June 2010
3 / Sediment analyses
- 34S stable isotope pools, C,N,P, Fe+ , / Institute of Biology, Denmark(IBD) / Samples from September 2009 have been analysed. Results are shown below. Samples from June 2010 are pending
5 / Zostera analyses
- Detailed meadows mapping
- Shoot density and cover of seagrasses, Above-to-below-ground ratio
- Tissue nutrient contents (above and below-ground tissues),
- Carbohydrate storage in below-ground tissues
- 34S stable isotopes in above- and below-ground tissues to indicate sulfide invasion from sediment
- 15N stable isotopes in leaves to indicate nutrient source;
- Iron plaque extractions / CLGE, Bulgaria
Institute of Botany, Bulgaria, CLGE, Bulgaria
Institute of Biology, Denmark
Institute of Biology, Denmark
Institute of Biology, Denmark
Institute of Biology, Denmark
Institute of Biology, Denmark / Sampled seagrasses at 4 stations, divided into species (up to 4 different species at each station), above- and below-ground biomass determined by drying seagrass.
Samples from September 2009 have been analysed. Results are shown below. Samples from June 2010 are pending. Samples for carbohydrate storage and 15N stable isotopes are pending from all campaigns
After visual inspection of the seagrasses, there can be noted a difference between P01 and P03, where at P03 the plants are less diverse but larger and sturdier, also more overgrown by epiphytes. At P01 there is higher species diversity, and plants are smaller. Regarding iron plaque on the plants, no large difference between the two locations can be visually observed. Since sediment is quite similar at both locations, no remarkable difference in iron plaque concentration is expected.

In June 2010, at each sampling location (plot) additional sediment samples were collected to measure the following parameters:

1)sulfate reduction rate (12 samples, 3 replicates from each location)

2)reactive iron content (12 samples)

3)total iron content (12 samples)

There were also collected seagrass samples for iron plaque extraction, 27 samples in total. They were collected in two locations: P01 and P03. There were two species analyzed: Zostera marina (present at both locations) and Zostera nana (present only at P01).

  1. What is the reason of not performed measurements/sampling and will this affect the results of the project. Can this experiments be omitted?

All planned samples were collected, and there are no needs for modification of the working protocol.

  1. Number of samples/parameters measured or planned for measurement

4 stations were sampled and at each location between 1 to 4 seagrass species were sorted and separated into above- and below-ground tissues in 3 replicates. The below-ground tissues was later be divided into rhizomes and roots. We have analysed approximately100 plant samples for nutrient (N,P), Carbon and Fe content. The 34S values, including total sulfur content, have been analysed for 2009.

We collected 3 replicate sediment samples from the 4 stations (12 in total), and they are analysed for nutrient (N,P) and carbon and Fe content.

We collected 3 replicate sediment samples from the 4 stations for 34S values (12 in total). The sediments have been distilled to separate into the acid volatile and chromium reducible fraction and analysed for 34S values.

  1. When do you expect to receive the end results

The results from 2009 are available and shown below. The 15N values are waiting the installation of a new mass spectrometer, and we hope to be able to provide the numbers by the end of the year at latest. The carbohydrates will be analysed during the autumn and early winter depending on the available technical support in the laboratory.

The dried sediments have been processed along with the plant samples, and results are shown below.

5. Suggestions for the next field work in September 2010.

a. Repeat sampling of seagrasses at the 4 stations to obtain above- and below-ground biomass, and keep dried materials for nutrient analysis, carbon, carbohydrate and possibly 34S values.

b. Take photos of the sites to visualize the presence of macroalgae and estimate visual changes of the meadows compared to summer sampling.

c. Sample sediments for nutrient and carbon analysis, but no sampling for 34S values, as we will use the values from the summer sampling.

Plant results from July and September 2009

Carbon (left) and nitrogen (right) content in Zostera marina sampled at 4 stations in July 2009. Note reduction in carbon content at Sta. 4 and 5
Carbon (left) and nitrogen (right) content in Zostera noltii sampled at 3 stations in July 2009. Note high N content in leaves.
/ Carbon (upper) and nitrogen (lower) content in Ruppia maritima and Potamogeton sampled at 4 stations in July 2009. Note low N content inPotamogeton in Sta. 2.
Phosphorus content in Z. marina and Z. noltii during sampling in July 2009
Phosphorus content in Ruppia maritima and Potamogetonduring sampling in July 2009
Carbon (left) and nitrogen (right) content in Zostera marina sampled at 4 stations in September 2009.
Carbon (left) and nitrogen (right) content in Zostera noltii sampled at 3 stations in September 2009. Note high N content in leaves.
Phosphorus content in Z. marina and Z. noltii during sampling in September 2009
Carbon (left) and nitrogen (right) and phosphorus (lower) content in Ruppia maritima sampled at 2 stations in September 2009.
Total sulfur content (upper) and δ34S (lower) in Zostera marina sampled in July 2009. Not much difference between stations and quite positive numbers suggesting limited sulfide invasion into the plants.

1