Robert J. Morris

Sterols of the phytoplankton—effects of illumination and growth stage

Abstract The sterol compositions of different species of cultured phytoplankton, (two diatoms— Phaeodactylum tricornutum and Skeletonema costatum , two green algae— Danaliella minuta and Tetraselmis tetrathele and a brown alga— Monochrysis lutheri ) were compared with that of a diatom field population ( > 98 % Thalassionema nitzschioides ) using GC-MS techniques. The effect of culture age in the cultured specimen; was examined by harvesting in both the exponential and stationary growth phases and was found to produce considerable differences in the sterol composition in some species. The influence of the intensity and different spectral illumination on a cultured specimen of a green alga ( Danaliella minuta ) was also examined and found to produce changes in the sterol composition.

The fatty acids of some marine crustaceans

The lipids of one species of epipelagic euphausiid and six species of mesopelagic decapods from the eastern-North Atlantic have been shown by thin-layer chromatography to consist mainly of triglyceride, with small amounts of mono- and di-glyceride, sterol, sterol ester and phospholipid. The generally low level of lipid (2–5% wet weight) suggests that lipids have no buoyancy function in these animals. Gas-liquid chromatography showed that the fatty acid composition of Euphausia brevis differed from that of the decapods in having much less octadecaenoic acid (18:1) and more eicosapentaenoic acid (20:5) and docosahexaenoic acid (22:6). The principal differences in the fatty acid composition of the decapods were in their contents of octadecaenoic, eicosaenoic (20:1) and docosaenoic (22:1) acids, but no correlation was found between fatty acid composition and species. A specimen of Acanthephyra acanthitelsonis which had a high fat content (9% wet weight) had a fatty acid composition different from that of another specimen with a normal fat content (3·8%). No significant differences were found between samples of Systellaspis debilis collected from two stations 1000 miles apart.

Concentrations of some trace metals in pelagic organisms and of mercury in Northeast Atlantic Ocean water

Abstract Several trace metals (Zn, As, Cd, Sb and Hg) have been determined, by neutron activation analysis, in pelagic organisms, mainly crustaceans and fishes, collected mostly off northwest Africa and in the Azores region. Concentrations of mercury (0·06 to 0·38 ppm dry weight) showed no clear trend with trophic level. Organo-mercury analyses on two species showed that the element was present largely in the methyl mercuric form. Concentrations of cadmium, which reached 13 ppm dry weight in Systellaspis deblis and Oplophorus sp., and of arsenic, which averaged 25 ppm dry weight in the crustaceans, tended to decrease in the tissues of fishes. Values for antimony which were all below 0·1 ppm dry weight, showed some indication of a similar trend. Concentrations of mercury in sea water from an adjacent area ranged from 17 to 142 ng/l., the highest concentration occurring in deep water.

The geochemistry of a recent marine sediment off northwest Africa. An assessment of source of input and early diagenesis

Abstract An 80-cm sediment core (0 to 10,000 years B.P., 14 C date), taken from the continental slope in the Eastern Atlantic has been examined for variation with depth in clay mineral content, calcite/ quartzratio , δ 13 C value and lipid (hydrocarbon and fatty acid) content. The results suggest a dual (marine and terrigenous) origin for the sediment. Lipid analyses indicate marked variations with time in sources of lipid to the sediments as well as a high degree of preservation of organic material, including unsaturated compounds.

Marine sterols. V. sterols of some tunicata. The occurrence of saturated ring sterols in these filter-feeding organisms

Abstract The sterols present in one oceanic and two coastal tunicates have been determined by combined gas chromatography-mass spectrometry techniques. Very complex sterol profiles were found in a Pyrosoma sp. and Ascidia mentula O. F. Muller, with 25 and 27 sterols, respectively, in which a high proportion of the sterols were identified as saturated ring compounds. The analyses established the presence of related pairs of 5α-stanols and Δ5-sterols with identical sidechains, whereas Δ7-sterols were almost absent in these extracts. A number of the 5α-stanols found are very uncommon in the marine environment and the presence of new C31 and C32 sterols with long sidechains indicated in the Ascidia mentula extracts is notable. Extracts of the coastal species, Ciona intestinalis L., were much simpler and contained only 13 sterols, some of which were saturated ring compounds.

The fatty acids of some cephalopods

Abstract Eight species of squid from the eastern-North Atlantic have been found to contain low levels (2–3% wet weight) of lipid. The fatty acid composition of these lipids was found to be similar to that of euphausiids but different from that of decapods from the same region. An octopod, also from the same region, was found to have a high level of a branched chain acid (probably C 18 ) but was deficient in some of the more typical marine fatty acids.

Changes in the lipid composition of Acanthephyra purpurea Milne Edwards (Crustacea: Decapoda) during its diurnal migration: A preliminary investigation

Abstract The lipids of the mesopelagic decapod Acanthephyra purpurea Milne Edwards have been studied in relation to its diurnal vertical migration. The total lipid content increased between midnight and early morning, and both the triglyceride and wax ester fractions showed considerable variation in amount. There was a significant increase in the phospholipid content during its period in deep water, suggesting a diurnal rhythm of lipid metabolism associated with the migratory rhythm.

Occurrence of long-chain alkan-diols and alkan-15-one-1-ols in a quaternary sapropel from the Eastern Mediterranean

C28−C32 alkandiols and keto-ols are reported in an S1 sapropel from the Eastern Mediterranean. Mediterranean. Their occurrence in this sediment and in certain other sedimentary environments may provide a clue to their source which is thought to be a specific marine organism or group of marine organisms.

Variations in the fatty acid composition of oceanic euphausiids

Abstract The lipids of twelve species of euphausiids from the N.E. Atlantic and the W. Mediterranean have been examined by thin-layer chromatography and their fatty acid compositions have been determined by gas-liquid chromatography. There was little variation in fatty acid composition found between species of the same genus and even between different genera. However the two deep non-migrant species examined were unusual in their high percentage of monounsaturated fatty acids. There also appeared to be a seasonal variation in the content of polyunsaturated fatty acids for Euphausia gibboides .

Marine sterols—VII. The sterol compositions of oceanic and coastal marine annelida species

Abstract 1. 1. The sterol compositions of two oceanic and three inter-tidal zone species of annelid have been analysed by combined GC-MS techniques and the results compared with previous analyses. 2. 2. It was found that the oceanic annelids had more complex sterol profiles in which small quantities of 5α-stanols were present, whereas in the simpler profiles of the intertidal zone species, 5α-stanols were normally absent. 3. 5. It was also found that lugworm species from South Africa and South Wales contained substantially identical sterol compositions.