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


PROLOGUE

Aulin submitted this thesis at the University of Uppsala where he defended it on the 18th of May 1872, at the age of 31, a week before the five-years younger Kjellman presented his. Although Kjellman's thesis, on the brown algal family Ectocarpaceae, was rather narrow-minded, it gained better support as it can be concluded by Kjellman's later promotion as professor in Botany. We do not know what the situation would have been if Aulin had also been granted a place, but he was ostracized and never made another contribution on algae. On the other hand, Kjellman's advancement led to his significant studies on the arctic algae and the development of a strong taxonomic school from where phycologists such as Kylin, Skottsberg and Svedelius graduated.
 As sources to his work, Aulin cited Harvey, Agardh and Areschoug, and indeed the entire thesis is a compilation of the most recent floristic observations made by the above and other authorities. The major thrust of Aulin's thesis lies, however, in the 3nd Chapter where he presents geographical data of distinct taxa (as briefly done by Lamouroux in 1826). Orders, families, genera, and sometimes even species appear systematically (after Areschoug's latest unpublished classification) and information is given with regard to commonness, habitat, diversity and distribution. In this way, the various algae are separately examined within 'monophyletic' groups and the 'biogeography' of each group, is assessed in a way that is unique for that time. This analysis remains, however, sterile. No hypotheses are discussed as to possible centers of origin, dispersal routes, or closely related taxa, although some of these concepts are touched. Aulin's account could be greatly improved if he had considered Darwin's recent theories, but this never happened.
  A few additions and the division of the text into 4 chapters [in parentheses] have been made in this translation, that otherwise is rather close to the Swedish original. The six footnotes given by Aulin appear at the end together with three more [in parentheses].

Goteborg, 4th December 2000

Algologia

[INTRODUCTION]

It was reserved to the scientists of the past century, to start the significant and large task of classifying the numerous living things of the botanical kingdom. They gave all their love to the study of higher plants, whose flowers could be distinguished by the naked eye; to the plant's structure, different tissues, and other peculiarities of the plant kingdom they paid less attention to. Obvious was that under such circumstances the lower plants would not be studied with care. The botanists were busy with describing and classifying the higher plants. The undeveloped optical instruments were a good reason for the botanists of that time to avoid the study of lower plants. Because it is rather certain that not a Linne, in case he had access to a modern microscope, and his scientific time was enough for numerous investigations, would have placed the lichens within a few or the algae within 3-4 genera. The incomplete study of the reproductive structures, their function och purposes made also the reasons of separating the plants in two groups: phanerogams and cryptogams; hopefully the terms seed plants and spore plants should be instead used today.
  It is true that the compound microscope had long ago been invented, but it was imperfect; in our century they have become much improved, and thereby the possibility to investigate many things in nature, that are obscure to the naked eye, has increased. Without these closer observations on the development and reproduction of the spore plants, no real knowledge of them could have been achieved. Now, the obstacle to get this knowledge for the lower plants was removed. One could say that the footsteps of botanists went parallel to the improvement of the microscope, and soon the great discoveries on the reproduction and internal structure of the seed and spore plants were made. The study of ferns, most of the mosses and some other families of spore plants necessitates no high resolution; the plants in these families allow to be readily classified. But this is not the case with the three large groups Lichens, Algae, and Fungi, although the first named were relatively well-known prior to the advent of the microscope. Yet, only after its usage we have been able to name different species in a natural way within these groups.
  As it is known, the algae exhibit forms that apart from reproduction are highly different from each other. With regard to e.g. Wormskioldia [Delesseria] and the species of the large genus Sargassum, which both have a kind of blade and a midrib, or the small unicellular algae that like Caulerpa are composed of a single cell, but only the latter become large and highly branched (and are undoubtly the most interesting amongst the algae). We also mark the Laminarians's and the Fucaceans's olive, green or brown colored species, that have very solid structure and some of which can reach considerable length, Florideans's variation of red, purpure, violet and even green color, the green algae, the incrusting corallines, those in the Mediterranean and in the West Indies occurring Siphonaceae, and the microscopic, motile, silicon-armed Diatomaceae. With regard to reproduction, they show no less variation; Florideans's reproduction, as far as we know, is highly strange and complicated, while in the Zoosporeae, Conjugatae, and in the lowest developed algae we deal we simple cell divisions. Of what has been indicated so far, and much more that could be added, it becomes clear that algae should have been studied carefully, and this has now been achieved. Many highly educated botanists have thoroughly studied these plants, and consequently the algae are now relatively well-known. To this event it has greatly contributed the continuous expeditions to all oceans of the world. By this way, enormous amounts of seaweeds have been taken home. The algae, which almost entirely live in the water from where they take up the necessary nutrients that support their development and distribution, in such a different manner than earth plants which take up nutrients from a matrix. Since the rhizoids, by which algae are attached, do not play a role in the supply of nutrients that [instead] are directly taken up from the surrounding medium that varies so greatly - different nutrients exist in fresh-, marine-, running-, or stagnant water - the algal vegetation must show differences in all these kinds of water. The present author has considered that it would not be without interest to attempt showing in some way, which differences exist in the algal vegetation within different parts of the Atlantic Ocean North of Equator, in the Mediterranean and in the Baltic, and even to try clarify what the reasons for these differences could be. In the preparation of this paper, I have taken into consideration the works of [J.] Agardh and Harvey, as well as Prof. Areschoug's lectures during the semesters of Spring 1865 and 1866. In addition, several minor communications and papers from natural history journals have been used.

[CHAPTER 1. GENERAL REMARKS ON THE ALGAL DISTRIBUTION.]

One is justified in saying that the geographical distribution of algae is mainly dependent on laws that correspond to those applying to other plants, although considering the fresh water algae our imperfect knowledge about their distribution within different regions and the vague limitation of species makes harder the fixation of such laws. Of course, one should take into account the great variety of conditions that cause differences in algal distribution against those causing differences in the distribution of other plants. As regards the seaweeds, the phytogeographical laws appear rather clear, although the large number of species and the many different parameters that contribute, make it more difficult to separate the borders between the vegetation regions than it is for terrestrial plants. One should also remember that the more primitively a plant is organized all the better it can overcome a greater variety of climatic variations under otherwise favorable conditions.- It has been observed that some algae in different waters of the same latitude show a very different distribution. Because, so long the sea temperature exercises a decisive influence, the seaweed floras in similar climatic conditions are characterized by similar or analogous forms, in case other parameters permit that. Sea currents cause not insignificant changes in this respect, thereby bringing several southern species higher up to the nordic countries; thus the Gulf Stream brings the tropical Sargassum up to the 44 north latitude; and similarly, because of that current, bend the isothermes considerably and the arctic algae reach more southernly on the North American coast than in Europe, whose NW coast receives a much milder climate than otherwise would have had. As it was said, many other parameters exist, apart from temperature, that control the distribution of seaweeds, for example water salinity, depth, ebb and flow, the character of the bottom, etc. Otherwise, since the temperature of the water does not vary in the same grade as in the air, one could suppose that the seaweed flora should be homogenous; yet, seas with rather similar temperatures display usually different and widely related species, particularly if they occur in a far remote distance from each other. Thus, although the Atlantic seaweed flora on the American coast is similar to that of the [Atlantic] Europe, it is certainly composed of a great part of different species; the seaweed flora of Florida reminds us by its general physiognomy, and none the less by some identical species, of the Mediterranean flora. Certain groups of algae exist entirely or with few exceptions in the warmer seas, as for example the Sargasseae, Corallineae, Cystoseireae, while other are found in the colder ones as for example, the Fuceae, Laminarieae etc.
  Within the different regions of the world, as regards terrestrial plants, we have considered certain places from where the plants gradually have dispersed to adjoining territories and thereby formed certain phytogeographical provinces, characterized by a uniform vegetation; in the same way we have observed in the sea several different floristic regions, where the same kind of alga dominates in each one. The seaweed flora of the Baltic appears to have been formed by this way, viz. that a part of the North Sea algae penetrated in and then dispersed to the various parts of the Baltic. The invaded flora by this way has changed much; species have become dwarf-sized and modified in other ways as the salinity decreases. In a similar way, the brackish water forms gradually become dominant as regards species diversity and quantity of individuals, until they are also replaced by fresh water forms in the innermost parts of the Finish Bay and the Bothnia Gulf. The number of Florideae diminishes in the Baltic, since they require for their growth partly higher salinity and partly other conditions not found there; therefor they become often sterile, dwarf-sized, and in many ways changed; Confervaceae [Cladophoraceae], Ulvaceae, etc., that thrive in lower salinity become instead the dominant species. Even in the North Sea, one can observe something similar; some algae become larger and more luxurious towards the north, other develop better in more southern sites, other still when they approach the open sea, hence it appears that they have wander to foreign regions from their original centre; also the North Sea displays an analogous mixture of algae from different places. The Mediterranean represents another highly remarkable region; already by the large number of genera and species, we can observe a significant difference from the Atlantic vegetation in general; observing closer the Mediterranean's many peculiar forms and the dominating families, one can confirm this truth even more. The coasts of SW Europe and NW Africa, and the islands between have an algal vegetation that forms a transition between that of the Atlantic and the Mediterranean in general. As it is known, the Mediterranean terrestrial coast has a rather peculiar plant vegetation, well distinct from those occurring in other coasts; and similarly its seaweed flora shows a different character than in other seas, such as the Atlantic in general or the North Sea. The algae growing near the water surface, those forming the upper layer to say, belong more or less to the same genus and species and show no obvious differences in both seas; the algae growing around the upper tide level in general look like each other in different seas, in a similar way as it is the case with certain terrestrial plants in the maritime zone, or with nitrogen-requiring plants, that apparently lack specific variation in different places. Those occupying the zone below exhibit however not minor differences: in the North Sea and the Atlantic this is demonstrated by the various brown algal species, such as Fucus, Fucodium [Ascophyllum], Halidrys, etc. which almost are entirely absent in the Mediterranean, where they are replaced by some Sporochnaceae, some species of Sargassum, as well as Cystoseira that in the North Sea has only one corresponding form, i.e. Halidrys siliquosa (L.). Similarly, in the Mediterranean occur only sporadic plants of some species of the characteristic Laminarieae that occupy the zone just below low tide; these are replaced by Dictyotaceae and several green algae such as Bryopsis, Valonia, etc. Certain North Sea forms are represented in the Mediterranean by similar but nevertheless really different species. Numerous of the beautiful Florideans of the North Sea, that grow in the Laminarian zone and also below, are lacking entirely or occur rarely in the Mediterranean, such as Delesseria, Plocamium, Ptilota, etc. In their place one finds other superficially less distinctive forms such as Aglaophyllum [Nitophyllum], Rytiphlaea, etc. Of Callithamnion, Ceramium and Polysiphonia we find many species, some of which are more luxurious that those in the North Sea; some species are the same in both seas, but not seldom these forms are dwarf-sized or modified in one of the places. Another region, whose algal vegetation also deserves attention is the Atlantic coast of North America; nevertheless, this floristic region does not have so many peculiar or different elements like the previous one; it shows some similarity partly with the North Sea and Atlantic Europe, as also with the Mediterranean vegetation; it is easier to recognize this similarity with the Mediterranean vegetation on the coasts of Mexico, the West Indien Islands and Florida. If we compare the algal vegetation on the Atlantic east coast with the west coast, we can observe numerous differences but also a significant similarity in many cases; a striking difference is that the same species on the American coast do not extent so far in the north as they do on the European coast. The reason for that is easy to find. Looking on a physical map, where the isothermes are marked, we observe that these bend to the benefit of Europe, in particular for Europe's NW part, so that for example the same line that touches New York on the 41 latitude meats Europe in Ireland on the 54 latitude; thereby a temperature difference between the countries lying on the same latitude on the west and east side of the Atlantic must exist, large enough to result in the above mentioned difference of algal vegetation. Among the floristic peculiarities of this region, formed by the American and European Atlantic coasts, it can be postulated that the algal vegetation is much more lively on the European coast than on the North America's corresponding parts, i.e. north of Florida; because south of this cape [Florida] the vegetation is extraordinarily rich and varying. On the European north and northwestern coasts occur, apart from several rare, six common Fucaceae, of which at least four are easy to find on every coast; on the American coast only Fucus vesiculosus L. and Halicoccus [Ascophyllum] nodosus (L.) are widely occurring; Fucus serratus L. and Fucodium [Pelvetia] canaliculatum (L.) have not been recorded so far; whether Halidrys and Himanthalia exist is uncertain. This apparent lack of Fucaceae is more obvious on the NE coast and is partly replaced by numerous Laminarians; a few amongst them that are specific for this coast deserve a closer examination, in particular the highly characteristic genus Agarum. Florideans occur in large amount on the coast of both continents; amongst them the blade-like species seem to be more common on the American than on the European coast. It is certain, as we will see in the following, that different families are differently represented on both coasts of the Atlantic, but on both coasts the red algae are generally the same. Along the northernmost parts of both continents occur about the same kind of green algae; nevertheless, a few characteristic forms are found for the different localities; on the other hand, in Central America the green algae occur with numerous genera and species, of which nothing is found along the European Atlantic coast; as mentioned before, analogous species are however encountered in the Mediterranean. The European coast between the Channel and Gibraltar is not different in its algal vegetation from the other [nearby] regions; numerous of those algae that have penetrated in the North Sea and where are usually met with as undeveloped, obtain here their natural forms as they grow on more open coasts and warmer waters; other disappear leaving space for northernmore and southernmore forms; a few Mediterranean algae are scattered here and by this way the vegetation appears mixed. I thought I ought to point out these differences as regards the algal vegetation in general within these regions that we have to pay particular attention to.


The text continues in AULIN.2

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