Fucus radicans – Narrow wrack

The scientific name of narrow wrack is Fucus radicans which means that it belongs in the Fucus family, together with bladderwrack, serrated wrack and spiral wrack (Fucus spiralis).

Narrow wrack is recently discovered, since it was long belived to be a dwarf morph of bladderwrack. It is not unusual that organisms are smaller in the low salinities of the Baltic Sea. Using genetic tools, narrow wrack was identified as a new species in 2005. Since then, researchers at Stockholm and Gothenburg University have studied the ecology, reproduction and genetics of the narrow wrack.

Narrow wrack (right) is thinner and more bushy than bladderwrack (left)

Narrow wrack (right) is thinner and more bushy than bladderwrack (left)

Narrow wrack is found along the Swedish coast from Öregrund to Umeå, from around Vaasa area down to Poori/Björneborg on the Finnish coast and around the Estonian island Ösel/Saaremaa (see map under The Baltic Sea fact). Narrow wrack has not been found outside the baltic Sea, as far as we know.

Narrow wrack is clonal, wich means that it reproduces by fragmentation, but it also has sexual reproduction. The individuals that have formed by fragmentation, where small branches from the plant falls off, drift away and then reattach to a rock or boulder, all have the same genetic variation as their “mother” plant. There is one plant in particular that have been very successful along the Swedish coast, where almost 80% of all individuals are one clone.

The Baltic Sea

The Baltic Sea is unique because of its low salinity. In the northernmost parts, the water is almost considered freshwater, whilst the salinity at the entrance/exit in Öresund lies around 15 psu (practical salinity unit, roughly equal to ‰ and denotes salinity). The low salinity of the Baltic Sea makes it a stressful environment for both freshwater and marine species, both groups lives on the very edge of their tolerance of either too high or too low salinity.

Salinity and Fucus distribution in the Baltic Sea

Salinity and Fucus distribution in the Baltic Sea

The map show surface water salinity and the distribution of the three species from the genus Fucus that can be found in the baltic Sea.
Green denotes bladderwrack (Fucus vesiculosus)
Orange denotes narrow wrack (Fucus radicans)
Yellow denotes serrated wrack (Fucus serratus) Note that for this species only the distribution along the Swedish coasline is shown, since we have not found any data on its distribution in any other countries along the Baltic Sea.

More information will follow.