Benthic macrofauna classification system for Faroese fjords: Menning av flokkingarskipan fyri botndjór á føroysku firðunum

The aim of this project was to develop a classification system for benthic macrofauna analysis in the
Faroese fjords, to be used by the Environmental Agency for assessing the potential impact of
aquaculture. With inspiration from our neighbouring countries, who have implemented the EU´s
Water Framework Directive, two different approaches were tested and compared; the Danish
approach that does not incorporate natural variabilities in the fjords, and a novel approach that
incorporates depth, Loss on ignition (LOI) in the sediment and sediment types, which are known to
affect the natural composition and abundance of the benthic community.
Our analysis shows that when developing a classification system for the Faroese fjords, there is no
need to develop individual classification systems for the different fjords, but that the classification
system must differentiate between sediment type, since muddy sediments have significantly lower
index values for benthic macrofauna compared to sandy sediments, which harbour a more diverse
habitat environment, and therefore a more diverse and richer benthic community. Therefore, we
recommend the latter approach that differentiates between sediment type to be used for developing
a classification system for the Faroese fjords.
However, as new aquaculture sites generally are placed outside fjords at more exposed sites it should
be kept in mind that the system will need to be re-evaluated on a regular basis, when more data from
these sites become available, since some of these areas might contain a different benthic community
and consequently naturally different index values, and that the classification system maybe should
differentiate between other factors as well, such as LOI content in the sediment.
Since no specific Faroese multi-metric index has been developed, another aim was to test established
indices that the Aquaculture Stewardship Counsel has approved, and those employed by our
neighbouring countries Norway, Sweden, Denmark and Scotland. The conclusion was, that 8 out of
the 10 candidate indices responded well to Zn as an environmental pressure derived from
aquaculture, and that the indices IQI and NQI, which are employed in Scotland and Norway,
respectively, were most sensitive to this pressure. Since IQI has a reference variable that is locally
determined for Great Britain built into its formulation, it is recommended that the NQI multi-metric
index is used in the Faroe Islands, as long as no Faroese index is specifically developed.