fulltext - DiVA

22 MATS WlERNalways sterile). Ceramium rubrum, Polysiphoniaelongata and P. urceolata are found lying loose onthe mud in inner parts of the fjords.Living "merl", the loose-lying Lithothamnion calcareum,common in the south of Europe, has beenfound in Sweden inside Bonden (Bohusliin). Big ballsof Lithothamnion known as "rugl" are very commonon the bottom of Arctic fjords in Norway. Only smallspecimens are found ·in Sweden (SuNESON 1943), butnever in the Baltic.A mixed vegetation, made up of species livingpartly attached to shells, partly loose-and-entangled,partly lying free on the bottom-as met within the Baltic-is , however, a common feature oncomparatively deep bottoms with a high salinity inArctic fjords of Norway:Omphalophyllum olivaceumDesmarestia aculeataEuthora cristataTurnerella PennyiExtinction of the intertidal beltRhodophyllis dichotomaPhyllophora Brodiaeiv. interruptaPtilota pectinataPhycodrys sinuosaOn the Atlantic coast the tide is everywhere presentand in places becomes heavily marked. At forinstance 8 m tidal amplitude as much as about lof the total vertical profile of algal vegetation maybe laid bare at lowest ebb. Where the coast is nottoo steep the ebb tide affords us possibilities towalk across the "hydrolittoral" landscape for miles,between rocks from which bundles of large Fucaceaehang down and across sandfields overgrown byVaucheria and crossed by salt-water trickles-occasionallyalso brooks with freshwater. We maystop to collect tender red algae in rock-pools retainingthe receding sea water or in caves wherethey are protected against rain and excessive light.For a visitor grown up on a non-tidal coast, themost interesting feature is the arrangement of thefucaceous algae in distinct belts, with a fixed verticalextension related to duration of exposure andimmersion. From the Pelvetia canaliculata belt,wetted only at high tide, we pass the belts of Fucusspiralis, of F. vesiculosus and Ascophyllum nodosum,and of F. serratus.It is remarkable to observe the rigidity in positionof these belts. Towards the interior of thePorsanger Fjord in Norway, bordering the BarentSea, Fucus serratus for some reason disappearsfrom its level. Though free for colonization, thisbelt of the rock remains naked, being invadedneither by Ascophyllum nor by Fucus vesiculosus.On the Swedish coast, however, the fixed levelsare given up by some of the belt-forming species.With the reduction and final disappearance of thetide and, further inward, the continued decrease insalinity, they develop the ability to proceed downward,the littoral position being left for the infralittoral.We shall later refer to this phenomenon asthe "downward process". However, we shall firstconsider some aspects obviously related to thereduction and finally almost total extinction ofthe tides, and thus to the disappearance of the"littoral" in the sense familiar to the algologists ofthe oceanic shores, viz. the intertidal zone. However,a different type of "littoral" does exist on theshores of tideless seas, for due to season, prevailingwinds, local exposure, etc., there is a considerableoscillation in sea level. The zones thus laid bare atintervals are, however, unsuitable to the Fucaceae(see below).On the Swedish side of the Skagerrak the tide issmall yet distinct. (See 86DERSTR6M's contributionto this volume.) The intertidal belt comprises perhapsfo of the algal profile. In this narrow fringe,a few decimetres only, we find as usual Fucusspiralis, F. vesiculosus and Ascophyllum, whereasPelvetia, Lichina pygmaea and Fucus ceranoides donot extend so far into the Skagerrak as the Swedishcoast, obviously expelled by the reduction of thetide.The most remarkable feature in the formation ofbelts on the Swedish West Coast is the fact thatFucus serratus is here entirely an infralittoral plant,extending in great masses down to a depth of 5-6 m,single plants even deeper.Further south, on the Kattegat, KYLIN (1907,p. 226) found a dense vegetation of Fucus vesiculosus(with or without Ascophyllum). It was saidto extend somewhat deeper down than on theBohuslan coast, to be replaced by F. serratus at adepth of i to 1 m. Single plants of F. vesiculosuswere found as deep down as 3 m in sheltered stations.At the northern entrance to the 6resund, SJ6-Acta Phytogeogr. Suec. 50