General Report

APPENDIXES Remark: The appendixes are published in the name and on the respon sibility of the different authors. 4 APPENDIX D ON THE PRODUCTION AND THE CONDITIONS OF PRODUCTION IN THE SEA BY K. BRANDT Translated from the German by 77. M. K Y LE 1 he practice of agriculture has received great benefits from scientific investigation of the cycle of chemical changes on land, by agricultural chemists, plant physiologists, bacteriologists, animal physiologists and by distinguished advocates of agricultural economy. It is now a question of utilising the experience and the results of investigation gained on land for an economy of the sea. It is self-evident that in this, we must take account of the special conditions which the organisms living in water experience as con trasted with the life surrounded by air. As many results of science have already been adopted with advantage in the management of ponds, we may be allowed to expect that similar principles can be introduced into the management of the sea, in such a way that the natural production can be helped out in the most rational manner possible. For all investigations which have as end the ascer taining of the productivity of a given area of water, a knowledge of the organic and inorganic changes in the sea and the discernment of the natural relations between pro duction and conditions of production are quite indispensable. We have tö thank V. Hen sen1 for the advancement of the aims and for the methodical grounding of all general marine biology. As I myself have been engaged in this field for 17 years, 1 have taken some pains to advance this branch of study as much as possible after the opportunity offered itself, with the organisation of the international investigations of the North-European seas, to make some voyages in the North Sea and Baltic on a German research-steamer, well equipped for scientific work, and to investigate some questions of general importance with the help of colleagues, also to improve the already existing methods so as to obtain results free of error. Just as on land, the true production ,in the sea, that is, the formation of new organic substance, arises exclusively from plant-life. It is only the plant which, owing to the possession of chlorophyll, can form organic materials from inorganic (carbonic acid, water and a number of salts) in the presence of light. The animals on the other hand, are all consumers; they must all take tbe organic materials necessary for the building up of the body and the maintenance of life from the plant-kingdom. On the death of animals .and plants the complex organic substances which composed their bodies, break down again, in consequence of the activity of certain bacteria, into the same simple inorganic materials from whicli the plants construct organic substance. The determination of the true production depends therefore entirely on the plants, J (Jeher die Bestimmung des Planktons oder des im Meere treibenden Materials an Pflanzen und Tieren. (5. Bericht d. Komm. z. wiss Unters, d. deutsch. Meere. 1887). t* APPENDIX D: BRANDT which occur in the sea chiefly in the form of extremely small chlorophyll-bearing organisms. The ocean in its entirety is comparable to very uniform and thickly populated paslure-land. The microscopic plants (diatoms, Peridineæ and fission-algae), which compose this pasture, are distributed like the finest particles of dust through the upper water-layers, sufficiently permeated by light. It is only where the land rises above the oceanic pasture which covers the greatest part of our Earth, that larger plants, such as sea-weeds, red algae, green algæ and sea grass, are found on the very narrow and also very defective ledge of the coast. On Ihe thickly populated pasture — of the land as of the ocean — the stock of plant-life appears to be very scarce because the newly formed plant-substance is con stantly being preyed upon, yet a closer investigation shows immediately that a very important amount of useful organic substance must in truth, be constructed in the course of the year. There is but one method for determining the production of plant-substance in the sea, namely, the plankton-method instituted in 1887 by Y. H en se n of Kiel. This method seeks to determine, as exactly as is possible in anything, the quality and the quantity of the smaller plankton-organims contained in a column of water of known dimensions. To ascertain the production for a region, it is necessary to make such hauls regularly once a week during a year at the same places. The same has to be done at other coast- places. The counting of the plankton, though it takes time, is quite indispensable, as it is only by exact numerical determination of the plants on the one hand and of the animals on the other, that we can estimate the production and consumption. For the commonest forms of plants and animals occurring in the plankton, we must determine by repeated investigation and observation, the rate of reproduction, the duration of the various developmental stages under varying conditions and the total organic changes of the species concerned; also for the commonest animals, the amount of food required and the kind of food. All these must be determined before we can estimate the production from the numerical data, obtained from a series of observations extending over at least one year. This is best done if, for the few dominant plant-species, we consider the quantity taken in the first haul as capital, the reproduction as interest, and then from previous knowledge of the rate of reproduction, calculate the year’s production from the interest. After one more year the capital is again almost as small as at the beginning. The interest has all been consumed. From the quantity and species of the animals, as well as from their ascertained requirements in the way of food, we can prove catch by catch, if the consumption has been as great in reality as the calculation has made it. The production of plant-substance in the sea may then be compared with that on land by arranging the chemical composition, as to quality and quantity, along parallel lines. We may determine how much organic substance in general, and in particular how much albumen, fat and carbohydrates, are formed per unit of surface during the course of the year, on the one hand for land e. g. a pasture, on the other hand, for water. The two more closely studied, main groups of plankton-flora, the Peridineæ and the diatoms, are very nearly related in composition to the best forage, and in autumn the plankton of Kiel Hay has in general almost the same composition as pasture ‘. 1 K. B ran d t, Beiträge zur Kenntnis der chemischen Zusammensetzung des Planktons. (Wiss. Meeres- untersuch. III. Kiel 1898i. — 5 — APPENDIX D: HRANDT The very numerous hauls of plankton made during the German quarterly cruises, have The prelimin ary work al been subjected to enumeration by Dr. Ap stein, partly with Dr. R a u schen plat, in order ready carried to determine exactly, the horizontal and vertical distribution of the principal plankton- out for the determination organisms in the regions of the North Sea and Baltic, and their relation to the seasons of the actual of the year. The results of the investigations for 1903 will be published this winter, production in the North Sea those for 1904 not before next summer. The opportunity has been utilised also, to make and Baltic special hauls for the investigation of the chemical composition of the plankton. A portion of this new material has already been worked out by Dr. Stiehr. Further investigations will also be set on foot to ascertain the structure, development, reproduction and habits, of the characteristic plant and animal forms of the plankton and their relation to other organisms, as well as to the outer conditions of life. Work is also being done on the plankton-methods, viz. comparison of the different nets, the quantities of the smallest plankton-organisms escaping through the pores of the nets, and the best method of quantitative estimation of the hauls. With respect to the last, Dr. Ap stein has just published an essay in which he maintains the indispensability of counting the plankton and the unserviceableness of mere estimates 1. Whilst these investigations are intended so to perfect Hen sen 's plankton-methods that a great, coherent investigation of the true production (e. g. in the North Sea) may be made in the not distant future, other preparatory work is also being done, which will contribute to deepening and extending the value of the results reached by the plankton- investigations. The aim of these new investigations is to learn more definitely, the general conditions of production in the ocean and to determine the factors on which the produc tion depends2. As the existence of animals is dependent on that of plants, so are these again Theconditions of production dependent on the general conditions of production for the amount of production. To gain information concerning the productivity of a region of the sea, it will probably soon be sufficient to make an exact investigation of the general conditions of production, which are-very much simpler and more uniform in the sea than on land. For this, we shall require to take into consideration, the scarce but indispensable food-stuff of plants dissolved in the water, and also the intensity of light — both of which investigations have been but little pursued hitherto — as obviously, the varying amount of the production in the sea depends mainly on these two factors.

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