Methods

MAREANO provides a unique picture of biodiversity through its use of various types of sampling equipment that provide good documentation of all types of seabed.

MAREANO carries out its surveys as follows:

1. The Norwegian Hydrographic Service supplies detailed maps of the seabed topography of the area to be surveyed, based on measurements made by multi-beam echo sounders.
2. The Geological Survey of Norway prepares seabed maps based on interpretations of the strength of acoustic signals from the multi-beam echo sounders, and seabed features interpreted from detailed terrain models
3. On the basis of this background information, the Institute of Marine Research and the Geological Survey of Norway select observation points for documentation of sediments, benthic fauna and environmental contaminants, with the aid of video and samples.

The seabed of the Norwegian continental shelf is highly variable and makes heavy technical demands of sampling equipment and procedures. Types of seabed are extremely varied; some of the main types are as follows:

• Soft, watery mud in sedimentation basins
• Hard- packed moraine clay (with gravel)
• Blocks and stones
• Sand
• Gravel
• Bedrock.

With the exception of mud, clay and sand without large stones, it is difficult to obtain seabed samples in such environments, which makes video documentation essential. The Campod video rig has been specially developed to meet the needs of MAREANO, and is an important tool for these surveys.

In some places, depths can vary between 200 and 2500 metres over short distances. Large topographical changes of this sort require a dense grid of observations, and are therefore time-consuming.

Sampling equipment

The  Campod video rig: covers 1500–2000 m² in one kilometre-long transects, and documents the distribution of seabed types and megafauna (benthic animals greater than 2 cm), but also shows traces left by fishing gear on both fauna and the seabed.

Box-corer: covers 0.1 m² and provides information about the particle composition of the sediments and organic material available as food for benthic fauna.

Grab: covers 0.5 m² and documents the quantitative composition of small organisms (0.15 cm) that live in the sediments (known as infauna).

Epibenthic sledge: covers 300–400 m² and documents the occurrence and composition of crustaceans (hyperbenthos) that live in the upper sedimentary layer or swim just over the seabed (shrimps, mysidae, amphipods, etc.).

Beam trawl: covers 500–800 m²; documents the occurrence of macro- and megafauna, particularly large animals that live in the upper layer or on the surface of the sediment.

Multicorer; capable of taking up to nine core samples, and used to study the sedimentary content of environmental contaminants.

The order in which these tools are used is not random. The video rig is the first to be deployed, as this enables  documentation of the seabed before the sampling process affects it, and indentification of sites where sensitive equipment (e.g. the box-corer, grab and epibenthic sledge) cannot be used. Samples are then gathered from suitable locations along the video transect, using the grab, multicorer and box-corer. Finally, the beam trawl and epibenthic sledge are dragged along the line of the video transect.