Peter D. Nichols

FATTY ACID COMPOSITION OF TEN MARINE ALGAE FROM AUSTRALIAN WATERS

Detailed fatty acid analyses are reported for ten benthic algae from Australian waters of which the data for Cladophora fascicularis (Chlorophyta); Polysiphonia pungens, Porphyra sp., Centroceras clavatum (Rhodophyta); Hormosira banksii, Ralfsia sp., and Dictyota dichomota (Phaeophyta) are presented for the first time. The analyses report the exact molecular structure of component acids which is essential for taxonomic and food chain studies. The acid 16:4ω3 could be taxonomically distinguishing for species of the Chlorophyta. The occurrence of cis-vaccenic acid (18:1ω7) in the algae reported here suggests a distribution in marine benthic algae which is wider than hitherto realised, with particular taxonomic importance for Chlorophyta species in which it occurs in high levels. Corallina officinalis was found to contain the non-methylene interrupted acids 20:2 and 22:2.

A comparison of lipid components of the fresh and dead leaves and pneumatophores of the mangrove Avicennia marina

Abstract The component hydrocarbons, sterols, alcohols, monobasic, α,ω-dibasic and ω-hydroxy acids of the fresh hand decayed leaves and the pneumatophores of the mangrove Avicennia marina are reported in detail. From the quantitative comparisons which can be drawn, relative changes in the lipid classes occurring during leaf decay can be highlighted. These base-line data are important to our understanding of inputs to marine intertidal sediments. During leaf decay the only significant changes were a reduction in the total absolute concentrations of monobasic acids due largely to a decrease in concentration of the C 18 polyunsaturated fatty acids, and an enhancement of the concentrations of the long-chain monobasic acids, ω-hydroxy acids and α,ω-dibasic acids. This resistance to degradation shown by the cutin derived acids (α,ω-dibasic, ω-hydroxy and long-chain monobasic acids) relative to the cellular and wax derived lipids may allow these cutin components to be used as quantitative markers of A. marina in mangrove associated sediments.

Lipid components of the seagrasses Posidonia australis and Heterozostera tasmanica as indicators of carbon source

Abstract The component hydrocarbons, sterols, alcohols, monocarboxylic, α, ω-dicarboxylic and ω-hydroxy acids of the seagrasses Posidonia australis and Heterozostera tasmanica and a sample of P. australis detritus are reported. The fresh leaves of P. australis and P. australis detritus are characterized by a distinctive distribution of solvent-extractable long-chain monocarboxylic, α, ω-dicarboxylic and ω-hydroxy acids. This distinctive pattern should enable these lipid components along with other distinctive components to be used as chemical markers of the seagrass P. australis . H. tasmanica is characterized by (1) higher relative concentrations of 16:2ω6 and 16:3ω3 than P. australis , (2) the absence of the distinctive distribution pattern of long-chain monocarboxylic and ω-hydroxy acids observed for P. australis , (3) the absence of α, ω-diacids and (4) a lower absolute concentration of ω-hydroxy acids than P. australis .

The fatty acid and sterol composition of two marine dinoflagellates

Abstract The fatty acid, sterol and chlorophyll pigment compositions of the marine dinoflagellates Gymnodinium wilczeki and Prorocentrum cordatum are reported. The fatty acids of both algae show a typical dinoflagellate distribution pattern with a predominance of C18, C20 and C22 unsaturated components. The acid 18:5ω3 is present at high concentration in these two dinoflagellates. G. wilczeki contains a high proportion (93.4%) of 4-methyl-5α-stanols including 4,23,24-trimethyl-5α-cholest-22E-en-3β-ol (dinosterol), dinostanol and 4,23,24-trimethyl-5α-cholest-7-en-3β-ol reported for the first time in dinoflagellates. The role of this sterol in the biosynthesis of 5α-stanols in dinoflagellates is discussed. P. cordatum contains high concentrations of a number of δ 24(28)-sterols with dinosterol, 24-methylcholesta-5,24(28)-dien-3β-ol, 23,24-dimethylcholesta-5,22E-dien-3β-ol, 4,24-dimethyl-5α-cholest-24(28)-en-3β-ol and a sterol identified as either 4,23,24-trimethyl- or 4-methyl-24-ethyl-5α-cholest-24(28)-en-3β-ol present as the five major components. The role of marine dinoflagellates in the input of both 4-methyl- and 4-desmethyl-5α-stanols to marine sediments is discussed.

The effect of mercury and cadmium on the fatty acid and sterol composition of the marine diatom asterionella glacialis

Abstract Cells of the marine diatom Asterionella glacialis treated with the organomercurial p-chloromercuribenzoate (PCMB) and cadmium, at growth retarding concentrations, exhibit decreased total fatty acid, polyunsaturated fatty acid and sterol contents. The level of individual fatty acids and sterols was also affected by metal treatment with significant decreases in the major polyunsaturated fatty acids 20:5Δ5,8,11,14,17, 16:1Δ9 and 16:3Δ3,6,9 in PCMB-treated, and 20:5Δ5,8,11,14,17 in cadmium-treated cells; increased cholest-5-en-3β-ol, particularly in PCMB-treated cells; and a decrease in the ratio of 24-ethylcholest-5-en-3β-ol to 24-ethylcholesta-5,24(28)Z-dien-3β-ol which was most notable in cadmium-treated cells. These results can be explained in terms of the formation of mercury and cadmium complexes with thiol-containing enzymes involved in lipid biosynthesis and metabolism, and thus provide further support for the hypothesis that transition metal toxicity is mediated by metal inactivation of physiologically essential, thiol-containing enzymes and co-factors.

Fatty acid components of nine species of molluscs of the littoral zone from Australian waters

Abstract 1. 1. There is evidence that differences in algal diet are reflected in the component fatty acid compositions of the limpets found at two sites. 2. 2. The tropical species of gastropods lacking macroscopic algae in their diet suggest in several component acids a high bacterial biomass intake. 3. 3. Seasonal variations are reflected in varying proportions of saturated, monoenoic and especially polyunsaturated fatty acids. A sub-tidal gastropod although in a stable environment relative to the intertidal zone still reflected a seasonal change which is presumably metabolic in origin. 4. 4. Nonmethylene-interrupted fatty acids were detected in relatively high concentration levels in all the molluscs examined.

STEROLS AND FATTY ACIDS OF THE MARINE UNICELLULAR ALGA, FCRG 51

Abstract The fatty acids and sterols of the marine unicellular alga FCRG 51 have been determined. The fatty acids show a predominance of C 18 and C 22 polyunsaturated components, typical of the Dinophyceae. Eleven sterols were detected, of which eight have been identified. Both 4-methyl sterols (41%) and 4-desmethyl sterols (59%) are present and these exhibit a wider range of structural diversity than has been reported previously for dinoflagellates. 24-Methylenecholesterol, 23,24-dimethylcholesta-5,22 E -dien-3β-ol and dinosterol are the three major sterols which together represent 75% of the total sterols. Dinosterol is found only in dinoflagellates and in some organisms which feed on dinoflagellates, but the two 4-desmethyl sterols are rarely reported in these algae. The lipid composition indicates that the unicellular alga FCRG 51 is related to the Dinophyceae and not to the Chloromonadophyceae or Chrysophyceae as previously proposed.

THE LIPID COMPOSITION OF THORACOSPHAERA HEIMII: EVIDENCE FOR INCLUSION IN THE DINOPHYCEAE1

The fatty acid, sterol and chlorophyll composition of the calcified, unicellular alga Thoracosphaera heimii (Lohmann) Kamptner are reported. The presence of 4,23,24‐termethyl‐5α‐cholest‐22E‐en‐3β‐ol (dinosterol), 4,23,24‐trimethyl‐5α‐cholest‐22E‐en‐3‐one (dinosterone) and the predominance of C18, C20 and C22 unsaturated fatty acids, including the acid 18:5ω3, indicates that T. heimii is a dinoflagellate. The fatty acid: sterol ratio (1.3), is typical of dinoflagellates. The geochemical significance of dinosterone, the high relative concentration of 4‐desmethyl‐5α‐stanols and the role of 23‐methyl‐5α‐cholest‐22E‐en‐3β‐ol in the biosynthesis of dinosterol in T. heimii are also discussed.

Lipids of the tropical seagrass Thallassia hemprichii

Abstract The component sterols, alcohols, hydrocarbons, monocarboxylic, α,ω-dicarboxylic and α- and ω-hydroxy acids from the leaves and roots of the tropical seagrass Thallassia hemprichii are reported. The leaves contained significant concentrations of cholest-5-en-3β-ol, a sterol not normally detected in either higher plants or seagrasses. The lower abundance of polyunsaturated fatty acids found in both the leaves and roots compared to other seagrass species may be a result of the warmer waters from which this species was collected. Solvent-extractable, long-chain (> C 22 )α,ω-diacids, α- and ω-hydroxy and monocarboxylic acids were also isolated from the leaves. The distribution pattern of these lipids should enable these components along with other distinctive components to be used as chemical markers for this seagrass.

Lipid components and utilization in consumers of a seagrass community: An indication of carbon source

Abstract 1. 1. The lipid components of three animals, the rock crab Nectocarcinus integrifons , the rock flathead Platycephalus laevigatus and the southern garfish Hyporhamphus melanochir , feeding in the seagrass beds at Corner Inlet, Victoria, Australia have been examined in detail in order to provide further information on seagrass community structure. 2. 2. Biological marker compounds detected within animal gut content material were used to recognize dietary sources and then utilized by community members. 3. 3. Both H. melanochir and N. integrifons have been shown to ingest and to varying degrees incorporate seagrass lipid material, thus further confirming the importance of seagrass carbon in the Corner Inlet environment. 4. 4. The southern sea garfish H. melanochir is observed to remove C 18 PUFAs (polyunsaturated fatty acids) from ingested seagrass material. 5. 5. Seagrass sterols are altered during incorporation into the lipids of this fish. 6. 6. Lipid-rich digestive juices play a role in the digestive processes of all three animals. 7. 7. Components tentatively identified as (NMI) (non-methylene interrupted) fatty acids have been detected in the lipids of the garfish H. melanochir and the crab N. integrifons . 8. 8. The fecal material of all three animals represent possible sources of these lipids (NMI acids) in Corner Inlet sediments. 9. 9. Based on lipid compositional data, N. integrifons feeds on Posidonia australis detritus and associated epiphyte material. 10. 10. The removal of both plant and epibiota cellular lipids along the digestive tract of the crab was observed, although structural components such as long chain mono- and α,ω-dicarboxylic acids, which have been previously recognized as seagrass marker lipids are not directly absorbed.