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A. B. Klugh. Studies on the photosynthesis of marine algae. No. 1.
Photosynthetic rates of Enteromorpha linza, Porphyra umbilicalis and
Delesseria sinuosa in red, green and blue light. Contrib. Canad. Biol.
& Fish. N. S., vol. VI, No. 4. Toronto, 1930.
About half the paper consists of a critical review of previous work upon
photosynthesis in various regions of the spectrum.
Pieces of the fronds of Enteromorpha linza, a green alga, growing just
beneath the surface of the sea, of a red alga, Porphyra umbilicalis, of which
the brownish red fronds were growing on the side of a dock at half-tide level,
and of Delesseria sinuosa, a bright magenta-red alga from a depth of 18
metres in Passamaquoddy Bay, were placed in vials of sea water (previously
brought to pH 7 by the addition of KH2PO4) behind Corning red, green
and blue filters, which had been brought to equal intensity in the photosynthetically active part of the spectrum, and exposed to sunshine. The
increase in alkalinity, due to the using up of carbon dioxide was determined by
observing the pH value with the set of capillary tubes containing standard
buffers, and phenol red as indicator, prepared by the British Drug Houses,
Ltd., of London. Photosynthetic rates for each species were determined by
dividing the gain in pH (in hundredths of a unit) by the time. The photosynthetic rates of these three species in the different regions of the spectrum
were different, those of £. linza being, red = 1.80, green = 0.16 and blue =
1.16; of P. umbilicalis, red, 2.46, green and blue 1.65; and of D. sinuosa,
red, 1.35, green, 1.25 and blue 1.05. These results fit in well with the transmission coefficients for red, green and blue light in the Bay of Fundy at
the place where the experiments were carried on, as green light penetrates
best, blue next and red least.
It may be noted that the change in pH value has been used as an index
of the carbon dioxide consumption, as over this range the two are proportional ; thus the latter is not proportional to the change in the hydrogen ion
concentration, but to a function of this, the pH value. The temperatures of
the experimental tubes were 25° C. at the start and never rose above 27° C,
being the same in all. The adjustment of the filters to equality was made by
the aid of a pyrheliometer using neutral tint screens, also a Wratten infrared (No. 88) filter. It was taken that mid-day sunlight consists of 50°/0
visible and 50°/0 infra-red radiation.
W. R. G. ATKINS.
A. Krogh and E. Lange with W. Smith. On the Organic matter given
off by algae. Biochem. Journ. Vol. XXIV, No. 6, London, 1930.
Although this paper deals with, fresh water algae, the results are of very
considerable interest to marine workers. According to Putter's well known
hypothesis, aquatic animals of all groups live largely on dissolved organic
matter present in the water and this is considered to be derived from the
photosynthetic processes of the plankton algae. The object of the present
work is to find whether, and to what extent, algae give off organic matter
to the surrounding medium. The final solution of such a problem in
the sea is not yet possible because of the difficulty of estimating,
with even a moderate degree of accuracy, the total dissolved organic matter
present. KROGH, however, has described a fairly accurate combustion
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method for fresh water (Biochem. Zeit. 221, p. 247, 1930) which surpasses
in reliability any methods hitherto available for sea water. His experiments
are in two groups; first, on pure cultures of Scenedesmus obliquus in artiflcal
media and second, on natural lake water in which the algae were brought
to luxuriant growth. In the culture experiments less than 5% of the organic
matter formed by photosynthesis was given off to the water while at least
95% was stored in the cells. In the experiments on natural lake water, the
amount given off was slightly higher but did not exceed 10°/0. In the
opinion of the authors, even this small quantity (at most 10°/0) was most
probably due mainly to dead and decomposed organisms. The organic
substances directly lost during assimilation was thought to be wholly
negligible.
The results then are very strong evidence against Putter's statement
that 80% or more of the material produced by algae during photosynthesis
is given up to the water, though whether different algae vary in this respect
remains to be seen. Among marine workers there is still a considerable
difference of opinion as to the validity of Putter's hypothesis, which will
only be removed as more accurate and reliable methods of analysis become
available. The present paper is an important step in that direction.
A. P. O.
W. N. Nikitin. Die untere Planktongrenze und deren Verteilung im
Schwarzen Meer. Int. Rev. d. ges. Hydrobiol. u. Hydrog. Bd. 25,
H. 1/2. Leipzig, 1930.
Since 1923 a number of periodic cruises have been made in the Black
Sea by which a general picture has been obtained of the various hydrographic conditions from the surface downwards throughout the year.
During this period plankton catches have been taken in silk townetss vertical hauls being made with NANSEN closing nets with which Corn's releasing
mechanism was used and horizontal hauls being made by means of a modifled model of GIESBRECHT'S closing net. The depths at which the nets were
fishing was estimated by measuring the angle of the towing warp and these
depths were checked by the use of Kelvin tubes.
As a result of these collections Professor NIKITIN has been able to provide a survey of the lower limits at which the plankton animals can live
over the whole of the Black Sea and the results are set out clearly in a map.
It is quite evident that this lower limit is determined by the peculiar hydrographic conditions to be found in the Black Sea. In the layers below 50 m.
there is a marked rising of all "Isoflachen" as one moves from the coast
outwards to the open waters; this contouring is closely followed also by the
lower limit of plankton life. Planktonic animal life is practically absent
at a depth at which the oxygen is reduced to 5—2%, and at which the
temperature varies between 8.55 and 8.65° C, and the salinity is at
21—21.10 %0. In this layer there are considerable quantities of dead plankton organisms and flocculent detrital matter due probably to a sudden
increase in the density and viscosity of the water. Here are also found a few
animals which can withstand temporarily the low oxygen conditions and
occasional presence of H 2 S. These are Calanus
finmarchicus,
Pseudocalanus