FINMARINET: Inventories and Planning for the Marine Natura 2000 Network in Finland. A.2 Geological inventories of the seafloor Final Report

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LIFE07 NAT/FIN/000151 FINMARINET: Inventories and Planning for the Marine Natura 2000 Network in

1 LIFE07 NAT/FIN/ FINMARINET: Inventories and Planning for the Marine Natura 2000 Network in Finland A.2 Geological inventories of the seafloor Final Report Geological Survey of Finland, GTK

1. Introduction Marine geological inventories provide information on the characteristics of the sea floor e.g. bathymetry and distribution of different seabed materials.

2 1. Introduction Marine geological inventories provide information on the characteristics of the sea floor e.g. bathymetry and distribution of different seabed materials. Inventories were made using acoustic-seismic methods and bottom sampling, using mainly GTK's survey vessel Geomari. Drop video was also used in all study areas. Acoustic-seismic methods include continuous sub bottom profiling, reflection seismic, side scan sonar and multi-beam echo sounding investigations. Picture 1. Acoustic-seismic methods used in geological field inventories. Acoustic-seismic surveys were done in one survey campaign per year/area. Sampling sites were selected on the basis of preliminary interpretation of acoustic-seismic surveys. Sediment samples were taken on a separate cruise to enhance the interpretation of acoustic-seismic records and to provide material for laboratory analysis. Piston corer, Van Veen grab sampler, box corer and a twin barrel GEMAX gravity corer were used in sampling. Acoustic-seismic data collected during fieldwork in addition with sediment sample data were used to produce marine geological maps of the survey areas. These maps were later used as background information for biological studies as well as for marine landscape production and other modelling purposes. Because of restrictions set by the Territorial Surveillance Act it is not possible to publish the marine geological maps produced in the project, except the map of Western Gulf of Finland EEZ, which is located outside Finnish territorial waters. However, all maps produced within FINMARINET were licensed for projects internal use for all beneficiaries e.g. as background information for modelling.

3 2. Field work performance Field work was originally scheduled for three first field seasons of the project Minor changes to the plans came up as the extension to the project was proposed in 2011 and thus a complimentary survey in target area 4 was executed in Nearly all goals set for the action were achieved and most of them clearly exceeded. The area covered by geological inventories 787 km 2 and the amount of survey line kms 1707 were well within the planned km 2 and km respectively. The amount of samples 107 exceeded the planned 100. Drop video recordings were not part of the original plans in geological field inventories, but 106 recordings were made in addition to scheduled work. Table 1. Original plan and realised outputs of geological field inventories. Project site Year PLANNED OUTPUT Area km 2 Survey line km Samples pcs Area km 2 Survey line km EEZ of Western Gulf of Finland, TA 6 The Archipelago of the Eastern Gulf of Finland, TA Samples pcs Bothnian Bay National Park, TA Kvarken Archipelago, TA Rauma Archipelago, TA TOTAL * Not included in the original project plan Drop video* 3. Description of project target areas 3.1. EEZ of Western Gulf of Finland (target area 6) The study area of Western Gulf of Finland is situated in the EEZ, south of the existing Tammisaari Archipelago Natural Park. Acoustic-seismic surveys covered an area of 102 km 2. The whole study area was totally covered with multibeam and side scan sonar data using line spacing of approximately 200 m instead of the 500 m normally used in marine geological mapping. This resulted in an excellent data set widely used within the project. In addition to the original plan, geological surveys were also performed during R/V Aranda's cruise in target area 6 in 14th-16th June 2010 in collaboration with SYKE's experts. In order to further study the geological structure of the seabed, three long sediment cores were recovered during the cruise. The lengths of the cores were 560 cm, 612 cm and 550 cm. The cores were described and photographed during the cruise and sub-sampled for further laboratory analyses.

Further west and south the bottom topography is more even and soft sediments prevail. Picture 3.

4 Picture 2. Bathymetry of the Western Gulf of Finland EEZ study area produced from multibeam data. Geologically the area represents a typical bottom type for the Gulf of Finland. In the north, i.e. closer to the shore, there are many bedrock outcrops with strong topography. Further west and south the bottom topography is more even and soft sediments prevail. Picture 3. Marine geological map combined with depth model of the Western Gulf of Finland EEZ study area.

3.2. The Archipelago of the Eastern Gulf of Finland (target area 7) Geological field inventories conducted in 2009 covered an area of 185 km 2 in the Eastern Gulf of Finland.

5 3.2. The Archipelago of the Eastern Gulf of Finland (target area 7) Geological field inventories conducted in 2009 covered an area of 185 km 2 in the Eastern Gulf of Finland. A normal survey line spacing of 500 meters was used excluding the detail area where the line spacing was meters. The area studied is geologically very diverse. Most of the bottom types of Finnish coastal waters occur here to some extent. Typical features of the Eastern Gulf of Finland are the underwater continuations of eskers and reefs composed of bedrock outcrops. Ferro manganese nodules are abundant on soft bottoms. Acoustic profiles show great variation both in bottom types and topography. Picture 4. A 28 khz echo sounder profile from the Eastern Gulf of Finland showing thick sediment structures combined with bedrock outcrops and high topographic variation Bothnian Bay National Park (target area 1) The northernmost part of the Finnish coastal waters, the Bay of Bothnia, is characterized with strong postglacial land uplift of about 8 mm/y. Several large rivers also discharge to the Bay of Bothnia. Typical for the study area are very soft and organic rich sediments in sheltered areas between the islands. On the other hand, an erosional sand cover of 1-5 cm on top of sediments is also typical, but on more open sea areas. The sediment cover in general is quite thick, and there are no bedrock outcrops in the study area while sand and till formations are the dominating substrate types with some clayey basins in between.

6 Picture 5. Bottom sediment sample from the bay of Bothnia showing litorina gyttja (grey) overlain by erosional sand (reddish brown). Multibeam equipment of the R/V Geomari went out of service during the survey in the Bothnian Bay and thus the multibeam data of project site 1 is missing. However, despite the malfunctioning of the multibeam equipment, enough data was recovered to produce depth models and seabed surface models for the area Kvarken Archipelago (target area 3) The study area of Kvarken Archipelago is very shallow and rocky. Bedrock outcrops and big boulders are typical for the area. This presents a problem with acoustic survey methods using research vessels. In order to guarantee safe navigation and to avoid damage to the equipment it is very challenging to run appropriate amount of survey lines in such difficult environment. In the future new survey methods, such as airborne Lidar and satellite imagery, should be used increasingly in shallow areas.

Picture 6. Nautical chart of the Kvarken Archipelago study area indicating difficulties in running the survey lines (black lines) in very shallow and rocky environment.

7 Picture 6. Nautical chart of the Kvarken Archipelago study area indicating difficulties in running the survey lines (black lines) in very shallow and rocky environment. The multibeam equipment of R/V Geomari was still out of order during major part of the acoustic survey and only the detailed study area of 2 km 2 could be covered with comprehensive bathymetric data. However, being so shallow in general, the Kvarken as well as any other shallow area, is not ideal for multibeam studies. This emphasizes even more the need for new survey techniques in shallow areas. As the Kvarken is situated close to the threshold between the Bay of Bothnia and the Sea of Bothnia, it is exposed to strong currents. Detailed multibeam study shows clearly how strong the currents are in the study area. The abundance of erratic boulders is also evident.

Picture 7. Multibeam image from Kvarken Archipelago showing clear marks of bottom current induced sediment structures. 3.5.

8 Picture 7. Multibeam image from Kvarken Archipelago showing clear marks of bottom current induced sediment structures Rauma Archipelago (target area 4) Geological inventories of Rauma Archipelago started in 2011 with acoustic survey covering ca. 200 km 2 and a sampling campaign resulting in 23 bottom sediment samples and 24 drop video recordings. As the survey campaigns in 2011 were executed with less effort than anticipated, it was considered worthwhile to invest the saved resources in a complementary survey campaign in the same area in The survey focused on possible sedimentary bedrock outcrops and De Geer moraine ridges found in 2011 survey campaign. The occurrence of sedimentary bedrock outcrops would have been of high interest since they potentially offer a totally different breeding ground for biota compared to the predominant crystalline bedrock. De Geer moraine ridges are typical for example the Quarken area of the Baltic Sea. Such moraine formations are not previously found in Rauma Archipelago. During the 2012 survey, six bottom samples with 15 drop video recordings were obtained. In addition, a second detail area of 2.5 km 2 with full coverage of multibeam data was surveyed. All bedrock outcrops inspected turned out to be of crystalline origin e.g. not sedimentary. De Geer moraine ridges were identified in the detail area and can be seen in Picture 8.

Picture 8. Multibeam image showing De Geer moraine ridges running in northeast-southwest direction in Rauma Archipelago. Overall, bottom conditions in the area seem to be very dynamic.

9 Picture 8. Multibeam image showing De Geer moraine ridges running in northeast-southwest direction in Rauma Archipelago. Overall, bottom conditions in the area seem to be very dynamic. This results in erosional sea bottom conditions with active sedimentation only in the sheltered inner archipelago. Eastern part of the area close to the shoreline consists mostly of till and bedrock outcrops with only a few basins with finer material. Going out to west towards the open sea and deeper water, the amount of clayey basins increases but till and bedrock outcrops are still quite frequent. There is a small esker formation in the southern part of the study area. 4. Conclusions Geological field inventories in Life+ FINMARINET project were conducted mainly according to the original plans. Most of the goals set for the action were achieved and some of them clearly exceeded. A lot of new information was gathered in and around the existing Natura 2000 areas within the scope of the project. Valuable experience was gained through the field inventories on how to execute the surveys in most efficient way in conjunction with biological inventories. During the project the interpretation process of the acoustic data was enhanced to better meet the demands of biological studies. Marine geological data collected in action A.2 of Life+ FINMARINET project were further used in project s other actions e.g. A.4 and A.5. Some difficulties came up during the project in delivering the marine geological data to project partners. All bathymetric and bottom quality data in Finnish territorial waters are restricted by the Territorial Surveillance Act. Licenses to deliver the data are granted by the Finnish Defense forces. Licensing processes were unexpectedly long and in future projects more effort should be given to these procedures already in advance.

10 Surveys in shallow areas, especially Kvarken Archipelago, revealed that new methods should be adopted in studying these kinds of environments. Multibeam technique is depth dependent and the coverage gained in shallow areas is very limited. To be able to collect comprehensive data sets of shallow areas new techniques are needed. Remote sensing methods, such as satellite imagery, aerial photography and Lidar are among these techniques, which potentially could be of more importance in the future.

BALANCE; sediment classification & harmonization, Archipelago Sea

BALANCE; sediment classification & harmonization, Archipelago Sea Title Intercalibration of sediment data from the Archipelago Sea BALANCE Interim Report No.14 Authors Reijonen, A. Kotilainen, A.T. Geological Survey of Finland Date May 2007 Approved by Johnny Reker Revisi