Annotations of the seaweed geographical distribution in the Atlantic Ocean North of Equator, in the Mediterranean and in the Baltic
by FREDRIK RUTGER AULIN
translated by Algologia

[CHAPTER 2. PHYSICAL PARAMETERS AFFECTING THE ALGAL DISTRIBUTION.]

Regarding the distribution of higher plants, as it is known, several different reasons exist that control more or less the species distributions; among other things, the nature of the ground and the related factors are of high significance, since these plants take up the nutrients through their roots from the matrix, which is not the case with the algae where the nutritive media, that are dissolved in the water that surrounds the algae, are absorbed through the surface of cells and by this way are acquired by the cell parts that deal with development and growth. The chemical compounds in the water are decomposed by the algae which take up what they need och separate the material that is useless; as an example that was demonstrated: a confervaceous [alga] was submerged in a solution of sulfur acid with copper oxid; the sulfur acid was then taken up by the alga while the copper was separated being useless. The algae lack such roots which being penetrated into a surrounding substrate can take up nutrients for the plant; instead, they have bulb-like, disc-like or filamentous rhizoids, by which they adhere, often very strongly to the substrate. They grow on rocks and stones of different type, on other algae, on wood, on shells of mussels, etc, in short on every substrate, that being submerged in the water offers them appropriate attachment. The so called rhizoids of algae have not in any way the same function as in seed plants or in the higher spore plants; the algal rhizoid is exclusively a structure for attachment. In one or another [alga], it reaches a significant size, namely in some tropical species that grow on loose bottom, on sand and among pieces of corals [rhodoliths ?]; under such conditions it develops towards each direction filaments that go rather deep; by this way, these rhizoids bind together the loose parts, amongst which they grow, to a concrete lump, and thereby the algae can remain attached despite a strong surge. When the algae grow on solid substrates, the rhizoids become of small size. Since the rhizoids of algae do not at all have with the nutrient uptake to do, one could think that the character of the bottom and the growth place have little or no influence on their distribution. However, this is not the case; the character of the bottom along with many of the other conditions occurring at the growth place have a strong influence on the distribution of algae. Solid rocks are more advantageous for the algae than loose pebbles, since the latter are easily removed by the waves and thereby the algae are getting loose; but if the surface of the rock is smooth, without any depressions, the strong waves can remove the algae from their growing places and thereby prevent the development of a rich vegetation. At very sheltered shores and in the innermost part of bays, a rich vegetation is formed, but this is homogenous with a large number of individuals of a few species, most often Fucaceans and the associated algae, which outcompete numerous younger species.
  In the same way as the large sand banks on earth are sterile and lack vegetation, the same applies to the sand bottoms below the sea surface and the long coast lines that have clay; we can say that bottoms of this kind represent the sea deserts. When such substrates, of the one or the other kind, occur off a coast, it is natural that this would make a large barrier for the dispersal of different species from the one place to the other; obvious is however, that on the earth this is a more efficient barrier for the dispersal of terrestrial plants, because algal spores can benefit from the waves and with greater easiness reach more remote areas, than what seeds of terrestrial plants can achieve by the help of winds. The most suitable algal substrates are therefore rocks, not very exposed or very sheltered, provided with deeper depressions, where the algae can find the shelter they need. During ebb remain these depressions [rock pools] full of water and thereby a large number of younger and delicate species, that could not stand the effect of direct sunlight, are protected; in this way, however, the rise of temperature in such rock pools benefits the beginning and development of a lively algal vegetation. North America's east coast, north of Florida, is rather poor in algae; this is rather certain because similar localities are here rare; the few in number Fucaceans are apparently an event directly related to the above named conditions. Since it is known that certain algae thrive being exposed sometimes to the air and sometimes protected by the water, it is natural that the regular low-leveling and high-leveling of the sea, that we call flood and ebb, must have a strong influence on the algal vegetation in the coasts where the phenomenon exists; this is confirmed by the rich and diversified vegetation that occurs between high and low water level. - Wherever water is missing for a time and the coast becomes exposed to air, there develops shortly algae of one or another group. They occur in warm and cold climates, in fresh and marine waters, on moist soil and as far as I know, yes, even in snow, and thereby show an extreme tolerance that surpasses that of any other plant. A striking difference between the marine algal vegetation and the fresh water algal vegetation in general is that the algae in lakes and in other fresh water systems are usually smaller in size and quantity in comparison to the higher plants that are both more numerous and larger in the same waters; in the sea the situation is totally different; there, the algae take the first place as regards the amount of individuals and size, and at times there are no seed plants at all in the sea; when they are found, they are always of lower significance; they prefer the brackish and fresh waters than the salty sea water. Along the sea shores, everywhere exists an algal vegetation, that usually is not vertically distributed to a great depth. From the Polar seas, where the shores are free from ice, to the Equator, the shores are covered with algae, which of course differ a lot after temperature and other parameters like growth place, water salinity, etc.
  A parameter that has great influence on the lower, no much less than the higher, plants's geographical distribution and perhaps to a greater degree than growth place is the water temperature. With regard of the wide temperature variation in the air, and the small changes in the water, particularly of the oceans, one could conclude that by no means the influence of temperature can have the same large impact on the water vegetation, and particularly on the marine one, as it does on the terrestrial plants. The influence of temperature is however easily observed. Comparing the algal vegetation at different latitudes, one founds that it changes in a similar way as the water temperature increases or decreases, approaching or moving away from the Equator; this difference resulting from temperature change is shown thereby in the presence of certain genera and groups exclusively in warm waters, and others exclusively in cold ones. Sea shores on the same latitude can, however, have a quite different algal vegetation, when because of one or another reason the temperature at one or the other place is higher or lower, as for example is the case between the European and the American coasts. This difference of temperature and the corresponding difference in algal vegetation depend significantly on the currents, that passing through the seas bring warm water to colder or cold water to warmer zones; thus, the above mentioned differences between Europe's and North America's algal vegetations are caused; therefore southern forms on the European coast reach much higher in the north than on the North American coast, and northern forms reach much lower in the south on the North American coast than on the European one; the influence of the Gulf Stream on the climate of various European coasts is marked when numerous algae that have been recorded in large amounts and well-developed sizes on the Irish coast, are absent on the English coast except in the southernmost bays and then [are found again] on the south coast of the European continent. In the North Atlantic, the Gulf Stream brings Sargassum bacciferum (Turn.) far up to the 44 latitude, although this alga belongs to the tropics[Footnote 1]. Of similar examples, it is easily understood, what great influence the temperature exercises on the geographical distribution of the marine algal vegetation. Even the seasonal temperature variations have an effect on the fertility of algae and in their wide or limited occurrence. This is particularly obvious for those species occurring between ebb and flood; they develop richer fructification and form well-developed structures during the warmer than the colder seasons, which is easiest observed for species that have exceeded their natural vegetation limit. Harvey takes as an example Padina pavonica (L.) that on the English coast during summer reaches a size slightly smaller than that which the plant obtains in the subtropical seas; during the cold seasons it becomes again dwarfish and stunted. The marine vegetation, like the terrestrial one, is considerably richer after a favorable winter and spring, than when these seasons of the year have been disadvantageous. To judge from the information that the present author had available, it appears that the algae in the Northern Hemisphere's warmer seas are more numerous than in the tropical waters; towards both Poles diminish their number gradually. A striking difference between the algal vegetation between the Northern and Southern Hemispheres is that within the former the species are usually smaller than in the latter, that is characterized by larger in size algae, while the Northern Hemisphere again has a greater variety of forms.
   Another noteworthy reason for the differences of algal geographical distribution, we can search in the depth variation in the seas, in the water's different pressure and in the light's stronger or lower intensity, conditions that are closely related to each other. Known is, what strong influence the light has on higher plants; although submerged in the water, the algae are also sensitive to it in high degree. It is strange to see, what significant differences exist between the same kind of algae, because they grow in deeper or shallow waters, on places exposed or not to the light; exceeding their natural territory, they become often dwarfish or distorted. A similar ability of change is observed, not only for the individual, but also for the terrestrial vegetation in general after the different height of the growing places over the sea; in the terrestrial plants this ability of change should be mainly controlled by temperature conditions; for the algae, this cannot be the only case, and several other reasons must exist; and other [factors] than changes in light intensity and pressure, being mutually connected, should be difficult to find. Sometimes the algae are getting loose from deeper places and drift to the surface, or the opposite; but they do not thrive and develop abnormally, on the same way as terrestrial plants that having passed their niche (moving upper or lower) change in one way or the other. Harvey tells us that in many such algae, which usually occur in shallow waters, a large number of branches and branchlets are present when specimens drift to deeper water; they show a clear tendency to develop a kind of rhizoids from various parts of the frond and the branches. In some cases, the habit changes considerably by the development of these outgrowths that it is difficult to identify such forms with the typical ones. The algae on the sea shores are usually restricted to a narrow zone, outside of which they do not thrive particularly well. Most algae grow in relatively shallow water; an exception appears to be the Diatomaceae, which occur everywhere between the splash zone and so deep in the sea as human research has gone; the lowest algae reach thereby to the greatest depths, in a similar way as the lower [terrestrial] plants reach the highest tops of the mountains. Apart from the diatoms, it appears that the deep sea lacks vegetation; however, the diatoms exist there in large number. As an example of the large amount they occur, it can be enough to cite that d'Orbigny counted no less than 3.849.000 such small plants in a pound sand from the Antilles. When one follows the bottom in a sea shore, he observes easily, as said, that the main vegetation soon diminishes and disappears long before the limit of the animal life is reached. To tell more exactly, where the algal vegetation ceases, is not so easy to say, particularly with the limited material of that type that we can refer to. Lamouroux maintains, according to Harvey, that algae exist down to a depth of 100 to 200 fathoms, which Harvey finds as being of a great difference; he names of course that Macrocystis, the longer alga we know, was once found by Hooker at about 40 fathoms depth (the length of the plant was of course greater); however, he considers this as an exception and cites 8 to 10 fathoms as the usual limit of the algal vegetation in southern temperate and Antarctic regions; this limit is probably deeper in the tropics and in the Northern Hemisphere after the observations we have on hand; and so has Humboldt collected an alga from a depth over 30 fathoms, and he marks that despite the low light and great pressure it was very alike as if it grew at a usual depth. In the Aegean Sea, Forbes collected an alga[Footnote 2] from a depth of 50 fathoms - the greatest depth from where an alga other than diatom has been demonstrably collected. The green, olive-colored brown and red algae usually occur at different depths in the sea[Footnote 3]; the green generally thrive best in the splash zone or in shallow waters, sometimes floating on the water surface; they love sun light and exist most in such places, where they are not totally exposed to the sun; certain genera however, such as Anadyomene, Caulerpa, Bryopsis are exceptions to that; they are by no means less green that the other, even if they occur on such depths where light is partly reduced. Within the zone that lies between ebb and flood or just below water level, we encounter the brown algae. They prefer sites where the water surf reaches them, and also localities where they can be exposed to the air during ebb and washed by the water during flood; they form a relatively wide zone along the shores just below water level; these are the condition in the Northern Hemisphere; in the Southern Hemisphere, those belonging to this group are gigantic species of the genera Macrocystis, Nereocystis, Lessonia, and by them many brown algae become deep water plants. The extensive zone that follows [below the brown algae] is occupied by the red algae that occur in the relatively deeper and darker parts of the oceans; they are rarely found in tide pools, when they are not protected from the direct sun light. Their red color is most clear and intensive, when the plants come from deeper water, which can be easily observed if they are collected both from the shallowest and deepest places where they are found. The strange encrusting or erect Corallineae are amongst the red algae, which one could not expect; while other algae decrease in number, increasing depth, these grow until they are the dominating plants in places where they soon become the only vegetation. As to the question of place, between the surface and the bottom, that the differently colored algae intake, the ability of the sea water to absorb the different colors of the white light must be remembered, since this appears to play a significant role, and apparently because of this capacity of the sea water the different shades of color are dependent upon.
   The distribution of higher plants is to a great extent controlled by the type of substrate in which they grow, especially its composition and its nutrients that the plants take up. Since the algae, as said above, do not take up any part of their nutrition from the sea bottom, but are exclusively depending on the nutrients in the surrounding sea water, one could conclude that the water is for the algae what for the higher plants represents the type of susbstrate itself. Obviously, the components that are essential for the growth of algae must exist in the water; analyses of the sea water indicate that the same substances occur as those found in seaweeds, although one and another element is rare in the seawater in contrast to what is found in algae; analyses of ashes of burned algae present just the most particular salts existing in the sea water. With knowledge of that, without difficulty, we can realize that the geographical distribution of seaweeds to a significant part, perhaps more than any other, is depending on the different salt content in the sea water. Iodine and bromine are obtained, as known, through the burning of Fucaceans, and after further processing of their ashes; when we now realize how small- just 0.000001%- the iodine percentage is in the sea water, and then consider, how much iodine is produced from the Fucacean ash, we can only wonder over the large amount that the Fucaceans yearly take up from the sea water. Since all the iodine unions with alkali-metals are highly water soluble, we can only presume that in the Fucacean's organization there exists a control that permits the uptake of iodine, in some kind of soluble salt union, and its assimilation so that the iodine cannot return to the surrounding water; these plants are for the iodine similar storerooms like terrestrial plants are for alkalines. Amongst the reasons of salinity differences in the sea water, one can name the great or small depths, the differences of desiccation from the surface, as also the large rivers that can decrease the water salinity by their outflow within considerable areas. In general, salinity becomes greater and greater from the Poles towards the Equator and from the surface to the bottom; in bays, where large rivers discharge their waters, the salinity considerably varies even during different seasons, as the rivers do not bring always the same water amount. The salinity in the oceans could be generally estimated between 33 and 38 gr/l. (Forchhammer cites a median value of 34.304 for the world oceans); that significant fluctuations in this case can take place, is natural. The great salinity of the Mediterranean is apparent; in this, its extension on the North African coast exercises a significant influence, since because of the hot winds the Mediterranean waters evaporate easily; because of the greater temperature in the Equatorial areas, the sea water becomes in these regions more saline than in the Poles. Following the work of Forchhammer, which as known, deals much with research about the sea water composition, the table below has been prepared, to show the salinity variation within diverse parts of the Atlantic north of Equator, in the Mediterranean and the Baltic (here, like elsewhere, is salinity always cited in gr per liter.):

...........................................................................................................................SALINITY
......................................................................No Analyses..........Median..............Maximum............Minimum

1. Atlantic from Equator - 30 N..........................19....................36,253.................37,908................34,283
2. Atlantic from 30 N - to a line bet.
Scotland and Newfoundland.................................25....................35,932.................36,927...............33,854
3. Atlantic from the above line-Iceland
and Labrador......................................................12.....................35,391..................36,480..............34,831
4. Greenland's current.........................................13.....................35,278..................35,563.............34,694
5. Davis Straits and Baffin's Bay...........................8.....................32,281..................34,414.............32,304
6. North Sea........................................................6.....................32,823..................35,041.............30,530
7. Kattegat and Oeresund (The Sound)...................7.....................15,228..................19,940.............10,869
8. Baltic and Bothnia Bay....................................9.......................4,931...................7,481................0,610
9. Mediterranean Sea..........................................11.....................37,936.................38,654..............36,931

As shown above, the salinity changes much within the various parts of each region; one observes a rise from the Pole to the Equator. Of interest, can also be to see how salinity increases in the Mediterranean, as we extend to the east, but it decreases in the same direction in the Baltic and in the Bothnia Bay. We also have to deal with the following information of salinity:

........Mediterranean Sea [Footnote 4]..............................................Baltic Sea [Footnote 5]
In the Gibraltar Straits..............36,391............................Karlskrona, sev.decades km off shore.................7,688
Bet. the Baleares & Spain..........38,321.............................In Landsort at Soedertoern.................................6,984
Between Sardinia & Naples.......38,654.............................Sev. decades of km north of Aaland.....................5,668
In Malta....................................37,177................................Qvarken at Holmoen...................................1,916
Between Malta & Greece............38,013..............................Haparanda skerries, Maloeren...........................1,505

To even show how the concentration of nutrients varies within different places, often to a large extent, the following is stated[Footnote 6]:

.....................................Atlantic below........Atlantic 20 54'N.....................Mediterranean bet..............Baltic Sea
...........................................Equator..............&..40 44'W..........................Sardinia & Naples
Natriumchlorid.....................27,892..................26,424........................................30,292.........................25,513
Magnesiumchlorid.................3,332....................4,022..........................................3,240...........................4,641
Natriumbromine.....................0,520...................0,400..........(Potassiumchlorid)......0,779...........................0,373
Potassium (in H2SO4)..........1,810...................1,625...............................................-...............................1,529
Calcium (in H2SO4)..............1,557...................1,597..........................................1,605............................1,622
Talc (in H2SO4)...................0,584...................0,678..........................................2,638............................0,706

Morover, different amounts and concentrations of substrates in the ashes of burned algae are produced:

     Ash
     %       KO    N20    C2O   MgO  Fe2O3  NaCl   NaI     SO2    PO5    SiO3
1.  20,40  22,40  08,29  11,86  07,44  00,62  28,39  03,62  13,26  02,56  01,56
2.  16,39  15,23  11,16  09,78  07,16  00,33  25,10  00,37  28,16  01,36  01,35
3.  15,63  04,51  21,15  16,36  12,66  00,34  18,76  01,33  21,06  04,40  00,43
4.  16,19  10,07  15,80  12,80  10,93  00,29  20,16  00,54  26,69  01,52  01,20

1. Laminaria digitata. 2. Fucus vesiculosus. 3. Fucus serratus. 4. Halicoccus [Ascophyllum] nodosus.

Of the above, where much more could be added, it is easily understood the great impact of the various amounts of nutrient in the sea water on the geographical distribution of algae. Moreover, even the rolling of sea has an influence on the composition of the sea water; in high sea its concentration of chlorine and sulphuric acid increases, to decrease again in calm weather.
  That the sea currents play an important role in the geographical distribution of seaweeds, since through their impact the temperature of the sea changes significantly, has been already said; but they also contribute purely physically in the dispersal of algae, often to widely remote areas. They bring with them not just spores but also sometimes entire individuals drifting them to places far away from where they had grown; even storms and strong waves tear them loose and bring them from one coast to the other; (so is Himanthalia found drifting on the coast of Bohus [Swedish west coast] with the help of west winds); usually then it is not possible for them to propagate, but for a short time it is possible like for example Sargassum bacciferum (Turn.) out in the Atlantic. As an example of how far an alga can reach by the help of the winds and the waves, it could be noted, that this Sargassum species often is found driven on the coast of England and sometimes even on the coast of Flandern. - As it is known, the algae are variously colored in the most strange ways; we have rather generally assumed, that this difference in color is caused by the light, that in this respect must have a strong influence; the stronger or lighter light, the stronger or lighter pressure, as well as the larger or smaller amount air in the water should be the most important factors on the issue of algae's color; algae of different colors are however found together from the surface and down to several fathoms depth. Examples occur [however], that red algae which have their apices over the water surface become green-colored, while the frond that is submerged remains red-colored. We have also tried to find an explanation of the various algal colors, in the latitudinal differences; but this appears to hold even less, since algae of different colors occur even more mixed on the same latitude than at the same depth.
  After these general observations, a brief description of the geographical distribution of the most important genera within the different groups must be given; here of course the notorious question of species number within families and orders can be raised, especially as the authors have rather different opinions about the species limits, as it is for the present the case; one extreme is for example to mention Kuetzing's rather soon to say countless species. - Professor J. E. Areschoug has kindly allowed me to use in my work his systematic classification that he applied in his lectures.

The text continues in AULIN.3

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