Fatty acids have been used as qualitative markers to trace or confirm predator-prey relationships in the marine environment for more than thirty years. More recently, they have also been used to identify key processes impacting the dynamics of some of the world's major ecosystems. The fatty acid trophic marker (FATM) concept is based on the observation that marine primary producers lay down certain fatty acid patterns that may be transferred conservatively to, and hence can be recognized in, primary consumers. To identify these fatty acid patterns the literature was surveyed and a partial least squares (PLS) regression analysis of the data was performed, validating the specificity of particular microalgal FATM. Microalgal group specific FATM have been traced in various primary consumers, particularly in herbivorous calanoid copepods, which accumulate large lipid reserves, and which dominate the zooplankton biomass in high latitude ecosystems. At higher trophic levels these markers of herbivory are obscured as the degree of carnivory increases, and as the fatty acids originate from a variety of dietary sources. Such differences are highlighted in a PLS regression analysis of fatty acid and fatty alcohol compositional data (the components of wax esters accumulated by many marine organisms) of key Arctic and Antarctic herbivorous, omnivorous and carnivorous copepod species. The analysis emphasizes how calanoid copepods separate from other copepods not only by their content of microalgal group specific FATM, but also by their large content of long-chain monounsaturated fatty acids and alcohols. These monounsaturates have been used to trace and resolve food web relationships in, for example, hyperiid amphipods, euphausiids and fish, which may consume large numbers of calanoid copepods. Results like these are extremely valuable for enabling the discrimination of specific prey species utilized by higher trophic level omnivores and carnivores without the employment of invasive techniques, and thereby for identifying the sources of energetic reserves. A conceptual model of the spatial and temporal dominance of group-specific primary producers, and hence the basic fatty acid patterns available to higher trophic levels is presented. The model is based on stratification, which acts on phytoplankton group dominance through the availability of light and nutrients. It predicts the seasonal and ecosystem specific contribution of diatom and flagellate/microbial loop FATM to food webs as a function of water column stability. Future prospects for the application of FATM in resolving dynamic ecosystem processes are assessed.

Fatty acid trophic markers in the pelagic marine environment.

In a series of experiments with nitrogen stress, optimum and supra-optimum nitrogen supply, N, K, P, Ca, and Mg have been analysed in leaves, stems and roots of birch seedlings (Betula oerrucosa Ehrh.). Growth rate was strongly and linearly correlated with the nitrogen status of the seedlings within the whole sub-optimum range. Seedling weight was equally strongly correlated with nitrogen status, although exponentially. Various expressions for growth rate and nitrogen status give similar results. Nitrogen efficiency (dry matter produced per unit nitrogen) decreased with increasing nitrogen status, but nitrogen productivity (dry matter produced per unit nitrogen and time) increased up to optimum.

The maintenance of a stable nitrogen status in the seedlings and a stable growth rate requires an accurate and closely controlled technique of nitrogen addition. Because of the exponential relation between seedling weight and sub-optimum nitrogen status and a rapid decrease in the supra-optimum range, a strict control of the optimum status is necessary to maintain maximum growth.

Nitrogen stress in birch seedlings. II. N, K, P, Ca, and Mg nutrition

Spectrophotometric Determination of Ammonia as Indophenol

Publisher Summary The determination of the total plankton biomass or biovolume is rapid compared with the enumeration and identification techniques. Many samples can be processed in parallel. These measurements are suitable for mixed samples as well as for samples of selected individual species. There is a wide variety of biovolume and biomass measurements. The effort involved in sample treatment increases within the conventional methods and is generally large in biochemical procedures. The methodological bias decreases stepwise: when the amount of excess and interstitial water is reduced by measuring displacement volume or wet mass instead of settled volume, when body fluids are totally removed during dry mass determination, and when the inorganic substances are subtracted. Volumetric methods are the only choice if the samples are to be used for species identification as well. Volumetric methods are also recommended as a quick-look procedure; that is, on board a ship, and in cases where no microbalance or other sophisticated equipment is available. There are two principles related to the volumetric methods: the direct volume estimation of settled plankton and the measurement of the amount of water displaced by the plankton. The first method is more gentle but less precise.

Biomass and abundance

The annual cycle of primary production in the Sargasso Sea off Bermuda

Of the reagents so far suggested for the reduction of phosphomolybdic acid to molybdenum blue in the determination of phosphate, only stannous chloride (Atkins, 1923; Harvey, 1948), metol (Burton & Riley, 1956), and ascorbic acid (Greenfield & Kalber, 1954), give colours of sufficient intensity to be used in the analysis of sea water. Burton & Riley (1956) have recently reviewed the use of stannous chloride as a reducing agent in the molybdenum-blue method for the determination of phosphate in sea water. This reagent suffers from a number of disad­ vantages; in particular that (i) the time taken for development of maximum colour depends on the salinity of the water and its temperature, (ii) the colour fades quite rapidly, (iii) there is a large salt error, and (iv) different batches of molybdate reagent give different extinctions with the same amount of phosphorus. These workers have proposed the use of metol (p-methyl-aminophenol sulphate) for the reduction of phosphomolybdic acid in the analysis of sea water. This reagent is free from most of the disadvantages of stannous chloride, but requires the development of colour to be carried out at 100° C. The use of ascorbic acid for the reduction of phosphomolybdic acid was first reported by Ammon & Hinsberg (1936). Their method was modified by Lowry, Roberts, Leiner, Wu & Farr (1954), who used a greater concentration of ascorbic acid. Essentially the same procedure was employed by Chen, Toribara & Warner (1956) for the micro-determination of phosphorus in biological fluids. Greenfield & Kalber (1954) have suggested the use of ascorbic acid for the determination of phosphorus in sea water. When this reductant was investigated, it was found possible to use a single reagent containing ammonium molybdate, ascorbic acid and sulphuric acid, instead of adding the acid molybdate and reducing agent separately, as in the stannous chloride method. The present paper describes the application of this mixed reagent to the determination of soluble phosphate in sea water. The relative amounts of sulphuric acid and ammonium molybdate in the reagent exert a very marked effect on the formation of phospho- and silico­ molybdic acids, and on the ease of reduction of these heteropoly acids and of

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A Single-Solution Method for the Determination of Soluble Phosphate in Sea Water

Thin-layer chromatographic procedures using silica gel and glucose have been employed for the examination of the pigments of twenty-three species of marine phytoplankton, drawn from a number of classes. Several new xanthophylls have been found including one similar to fucoxanthin which is the principal pigment in an, as yet, undescribed member of the Haptophyceae. The pigment array of a species of Olisthodiscus sp. (Plymouth no. 239) differs considerably from that of members of the Xanthophyceae and this species is probably incorrectly classified.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0025315400056459

The pigments of some marine phytoplankton species

Thin-layer chromatography has been used for the rapid separation of microgram amounts of pigments of marine phytoplankton, both from cultures and from the sea. The separation is carried out on plates coated with silica gel; the chromatogram is developed with a solvent consisting of petroleum ether (b.p. 60–80°), ethyl acetate and diethylamine in the ratio 58:30:12 by volume. The separated individual pigments may be eluted from the plate and characterized by their absorption spectra. The pigments of the following phytoplankton have been examined: Dunaliella primolecta, Phaeodactylum tricornutum, Isochrysis galbana, Dicrateria inornata, Coccolithus huxleyi, and Peridinium trochoidium.IntroductionA knowledge of the component pigments of phytoplankton is of value in the systematic classification of these organisms and in the study of the mechanism of photosynthesis. Very little is known about the amounts of the lesser phyto-plankton pigments associated with the natural phytoplankton crop in the sea, but a considerable amount of work has been carried out on the measurement of chlorophylls a, b and c and of carotenoids for the estimation of the plant bio-mass in the sea. These determinations are usually carried out by modifications of the poly-chromatic spectrophotometric method originally described by Richards with Thompson (1952) and modified by Creitz & Richards (1955) (see also Parsons & Strickland, 1963). While these procedures give a satisfactory measure of chlorophylls a and b, their precision for chlorophyll c and carotenoids is poor; furthermore, no resolution of carotenes from xanthophylls can be attained; nor can any indication of the presence of unusual pigments be obtained.

The use of thin-layer chromatography for the separation and identification of phytoplankton pigments

The component acids of the fats of the following marine algae have been investigated by gas-liquid chromatography:Rhodymenia palmata, Laurencia pinnatifida, Laminaria digitata, L. saccharina, Fucus vesiculosus, F. serratus, Pelvetia canaliculata, Ascophyllum nodosum. The principal saturated acids are palmitic and myristic acids, some contain ca. 2–5% of stearic acid; traces of C8 and C10 saturated acids are present, but C12 (and in all but one) C 20saturated acids are absent. The major unsaturated acids are octadecenoic and octadecadienoic acids (probably oleic and linoleic acids), but some species also contain appreciable amounts (up to 12%) of hexadecenoic acid. All the oils contain significant amounts of an eicosatetraenoic acid (probably arachidonic acid) and in some eicosatrienoic and/or eicosapentaenoic acids are also present in small quantities. Two acids of unknown constitution (possibly branched chain acids) are also present in minor amounts. No C22 unsaturated acids could be detected.INTRODUCTIONVery little is known about the component fatty acids of marine algae. Lovern (1936) examined the fatty acids from the fats of Fucus vesiculosus, Laminaria digitata and Rhodymenia palmata using lead salt crystallization and fractional distillation techniques (Table 2). With these methods, however, it was not possible to separate individual unsaturated acids having the same number of carbon atoms from one another. The mean unsaturation values of these fractions were therefore evaluated from their iodine values and expressed as the number of hydrogen atoms necessary to convert the fraction to the corresponding fully saturated state; thus ( — 4–0H) indicates an average unsaturation corresponding with two double bonds.

The component fatty acids of some sea-weed fats

Microdiffusion using a Cavett flask has been employed instead of vacuum distillation for the separation of ammonia from sea water; diffusion is approximately 75% complete after 24 h at 70°C. The recovered ammonia is determined by a modification of the phenate-hypochlorite method. Raney nickel in the presence of ethylenediamine-tetraacetic acid has been used for the reduction of nitrate and nitrite to ammonia. The latter is separated by microdiffusion and determined colorimetrically. The method showed a coefficient of variation of 2·5% on a sample of sea water containing No interference was encountered from a variety of organic nitrogen compounds.

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J. P. Riley

Papers

A Single-Solution Method for the Determination of Soluble Phosphate in Sea Water

The pigments of some marine phytoplankton species

The use of thin-layer chromatography for the separation and identification of phytoplankton pigments

The component fatty acids of some sea-weed fats

The determination of ammonia and total ionic inorganic nitrogen in sea water