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.

/pdf/determination-of-trophic-relationships-within-a-high-arctic-1mcgoeorbz.pdf

Determination of trophic relationships within a high Arctic marine food web using δ13C and δ15N analysis

Microscopic plastic debris, termed “microplastics”, are of increasing environmental concern. Recent studies have demonstrated that a range of zooplankton, including copepods, can ingest microplastics. Copepods are a globally abundant class of zooplankton that form a key trophic link between primary producers and higher trophic marine organisms. Here we demonstrate that ingestion of microplastics can significantly alter the feeding capacity of the pelagic copepod Calanus helgolandicus. Exposed to 20 μm polystyrene beads (75 microplastics mL(–1)) and cultured algae ([250 μg C L(–1)) for 24 h, C. helgolandicus ingested 11% fewer algal cells (P = 0.33) and 40% less carbon biomass (P < 0.01). There was a net downward shift in the mean size of algal prey consumed (P < 0.001), with a 3.6 fold increase in ingestion rate for the smallest size class of algal prey (11.6–12.6 μm), suggestive of postcapture or postingestion rejection. Prolonged exposure to polystyrene microplastics significantly decreased reproductive output, but there were no significant differences in egg production rates, respiration or survival. We constructed a conceptual energetic (carbon) budget showing that microplastic-exposed copepods suffer energetic depletion over time. We conclude that microplastics impede feeding in copepods, which over time could lead to sustained reductions in ingested carbon biomass.

The Impact of Polystyrene Microplastics on Feeding, Function and Fecundity in the Marine Copepod Calanus helgolandicus

VOLUME I Introduction The Incentive Physical-Chemical Properties Experimental Methods Quantitative Structure-Property Relationships (QSPRs) Mass Balance Models of Chemical Fate Data Sources and Presentation Illustrative QSPR Plots and Fate Calculations References Aliphatic and Cyclic Hydrocarbons Lists of Chemicals and Data Compilations Summary Tables and QSPR plots References Mononuclear Aromatic Hydrocarbons Lists of Chemicals and Data Compilations Summary Tables and QSPR plots References Polynuclear Aromatic Hydrocarbons (PAHs) and Related Aromatic Hydrocarbons Lists of Chemicals and Data Compilations Summary Tables and QSPR plots References VOLUME II * Halogenated Aliphatic Hydrocarbons Chlorobenzenes and Other Halogenated Mononuclear Aromatics Polychlorinated Biphenyls (PCBs) Chlorinated Dibenzop-dioxins Chlorinated Dibenzofurans VOLUME III * Ethers Alcohols Aldehydes and Ketones Carboxylic Acids Phenolic Compounds Esters VOLUME IV Nitrogen and Sulfur Compounds Lists of Chemicals and Data Compilations Summary Tables References Herbicides Lists of Chemicals and Data Compilations Summary Tables References Insecticides Lists of Chemicals and Data Compilations Summary Tables References Fungicides Lists of Chemicals and Data Compilations Summary Tables References APPENDICES List of Symbols and Abbreviations Alphabetical Index CAS Registry Index Molecular Formula Index * Each chapter contains lists of chemicals and data compilations, summary tables, QSPR plots, and references

Handbook of Physical-Chemical Properties and Environmental Fate for Organic Chemicals

Zooplankton storage lipids play an important role during reproduction, food scarcity, ontogeny and diapause, as shown by studies in various oceanic regions. While triacylglycerols, the primary storage lipid of terrestrial animals, are found in almost all zooplankton species, wax esters are the dominant storage lipid in many deep-living and polar zooplankton taxa. Phospholipids and diacylglycerol ethers are the unique storage lipids used by polar euphausiids and pteropods, respec- tively. In zooplankton with large stores of wax esters, triacylglycerols are more rapidly turned over and used for short-term energy needs, while wax esters serve as long-term energy deposits. Zooplankton groups found in polar, westerlies, upwelling and coastal biomes are characterized by accumulation of large lipid stores. In contrast, zooplankton from the trades/tropical biomes is mainly composed of omnivorous species with only small lipid reserves. Diapausing copepods, which enter deep water after feeding on phytoplankton during spring/summer blooms or at the end of upwelling periods, are characterized by large oil sacs filled with wax esters. The thermal expansion and com- pressibility of wax esters may allow diapausing copepods and other deep-water zooplankton to be neutrally buoyant in cold deep waters, and they can thus avoid spending energy to remain at these depths. Lipid droplets are often noted in zooplankton ovaries, and a portion of these droplets can be transferred to developing oocytes. In addition to lipid droplets, zooplankton eggs have yolks with lipovitellin, a lipoprotein with approximately equal amounts of protein and lipid. The lipovitellin lipid is predominantly phosphatidylcholine, so during reproduction females must convert a portion of their storage lipid into this phospholipid. Developing embryos use their lipovitellin and lipid droplets for energy and materials until feeding begins. The various functions storage lipids serve during the dif- ferent life history stages of zooplankton are very complex and still not fully understood and hence offer a multitude of fascinating research perspectives.

/pdf/lipid-storage-in-marine-zooplankton-2zcd7u8bm9.pdf

Lipid storage in marine zooplankton

Wax esters, which function as reserve fuels, account for 25 to 40% of the lipid of the pelagic copepod Calanus helgolandicus (Copepoda, Calanoida). In laboratory experiments with these crustaceans, diatoms (Lauderia borealis, Chaetoceros curvisetus, and Skeletonema costatum) and dinoflagellates (Gymnodinium splendens), which contained no wax esters, were used as food. Changes in the food concentration affected both the amount of lipid and the composition of the wax esters. Since the fatty acids of the triglycerides and wax esters of C. helgolandicus resembled the dietary fatty acid composition, it appeared that copepods incorporated their dietary fatty acids largely unchanged into their wax esters. The polyunsaturated alcohols of the wax esters did not correspond in carbon numbers or degrees of unsaturation to the dietary fatty acids. We postulate two different metabolic pools to explain the origin of these long chain alcohols. The phospholipid fatty acids were not affected by changes in the amount or type of food, probably because of their structural function.

Importance of wax esters and other lipids in the marine food chain: Phytoplankton and copepods

The common marine mussel Mytilus edulis has been observed to rapidly take up mineral oil, [ 14 C] heptadecane, 1,2,3,4-tetrahydronaphthalene, [ 14 C] toluene, [ 14 C] naphthalene, and [ 3 C] 3,4-benzopyrene from seawater solution. This species of mussel did not metabolize any of these compounds, and transfer of the mussel to fresh seawater, after exposure to the hydrocarbon in solution, resulted in the discharge of most of the hydrocarbon, although significant amounts remained (between 1 and 400 micrograms per mussel). The nontoxic paraffinic hydrocarbons mineral oil and heptadecane were taken up (10 milligrams per mussel) to a much greater extent than the aromatic hydrocarbons (2 to 20 micro-grams per mussel).

https://science.sciencemag.org/content/sci/177/4046/344.full.pdf

Petroleum Hydrocarbons: Uptake and Discharge by the Marine Mussel Mytilus edulis

Analyses of zooplankton and nekton from the central South Pacific showed that surface an d epipclagic zooplankton had small amounts of neutral lipids, mainly triglyccridcs, while deep-water tropical copepods had wax esters as the major lipid type, presumed to function as a rcscrvc srtoragc. The total lipid content and wax esters of tropical copepods captured at about 500 m were significantly lower than those of spccics from high latitudes. The median percentage of wax esters incrcascd progrcssivdy from tropical to polar latitudes in nine species of Cdiznus and five or six species of Euchaela. Deep-living tropical copepods had the same median percentage of wax esters as mcsopelagic and bathypelagic copepods from a subtropical station. Caridcan and penaeidcan decapods and euphausiids showed less than 5% wax esters. Gncrthophausia, a mcsopelagic mysid, stored wax cstcrs (32% of the lipid). A deep-water chactognath (Eukrohnia sp. ?) and a mesopolagic cranchiid squid had over 25% wax esters. Fish species not previously analyzed containing more than 10% wax esters included three myctophids and members of the As,troncsthidae, Cheilodipteridae, Gonostomatidae, Paralepididac, Scopelosauridae, and Stcrrioptychiclac. In previous studies of the occurrence and importance of reserve lipids in marinc zooplankton ( Lee et al. 1970, 1971, 1973) we have shown that copepods from the upper 500 m in polar and temperate latitudes had a higher lipid content than did copcpods from subtropical latitudes and that at an oceanic, subtropical station mcsopelagic and bathypclagic copepods (bw Carroll 1965; Gunstone 1967). We confirmed by direct mcal Travel funds and ship time were provided by the Marinc Life Research Group and National Science Foundation Grant GB 12413. This work was supported by National Science Foundation Grant Cl3 24834 and Marine Life Research Croup Gcncral Funds. surcments on zooplankton the hypothesis of Lewis ( 1967)) based on the observed increases in percentage by weight of oleic acid, that wax esters would be increasingly important in decpcr-dwelling pelagic animals. Nevenzcl et al. (1965, 1966) had shown that olcic acid is an important constitucnt fatty acid in wax cstcrs of the fishes Ruvettus pretiosus and Latimeria chalumnae. Morris (1971a) showed that in the tropical Atlantic the mesopelagic copepods Paraeuchaeta sarsi and Megacalanus princeps contained wax esters. Hcrc we report lipid data on fish and several dominant zooplankton groups collcctcd at a tropical station in the central South Pacific (24” S, 154” W) about 700 km southwest of Tahiti. Based on previous work ( Lee ct al. 1971)) WC hypo thcsizcd that tropical zooplankton from the near-surface waters would have little USC for lipid as a rcscrvc storage material because they have sufficient supplies of food and relatively small variations in the abiotic and biotic components of the cnvironmcnt; however, the deep-living zooplankton and nekton would tend to LIMNOLOGY AND OCEANOGRAPIIY 227 MARCH 1973, V. 18(Z) 228 RICHARD F. LEE AND JED HIROTA store lipid as a reserve because of the relatively lower concentrations of food and greater temporal and spatial variations in the rate of supply, Our objectives here arc fourfold: to determine whether the taxonomic and bathymetric patterns of the distribution of lipids in tropical zooplankton and nekton are similar to those previously observed at higher latitudes (over a third of the total ocean area lies between 20” N and S : Svordrup et al. 1942); to test the hypothesis that tropical epipclagic copepods have a lower average lipid content than those similar groups from higher latitudes; to determine whether the patterns of lipid distribution in copepods smaller than 2 mm in body length remain unchanged (all our previous data were for species larger than 2 mm); and to summarize existing data on the geographical distribution of total lipid content, wax ester, and triglyceride percentagcs in marine copepods. The chief scientist of the Aries III Expedition was J. A. McGowan, and his help in securing samples is greatly appreciated. We also thank R. J, LcBrasseur and J. D. Fulton for providing temperate water copepods; Arctic copepods were provided by H. Kobayashi and H. Fcrnandcz; and Antarctic copepods were provided by 0. Holm-Hansen. We thank A. A. Benson, in whose laboratory the lipid analyses were carried out, for his support and advice. WC gratefully acknowlcdgc the assistance of D. C, Judkins, T. Antczana, R. L. Wisner, and R. K. Johnson for their identification of dccapods, euphausiids, and fish. WC thank E. L. Vcnrick, J. A. McGowan, and A. W. Mantyla for kindly allowing us to use their unpublished data. J. C. Nevenzel made many helpful suggestions concerning analytical techniques. R. G. Ackman and I-1. P. Jeffrics reviewed the manuscript and improved it considerably with their comments. METHODS WC collected zooplankton and micronekton on Aries III Expedition, RV T. Washington ( March 1971)) using a 3-m Isaacs-Kidd midwater trawl cquippcd with a l-m net of 0.505-mm mesh attached to the end ring of the trawl. The samples were collected at a station in the central South Pacific (24” S, 154” W). A 2,500m time-depth recorder was used to detcrmine the depth interval sampled with the trawl (most sampled from O-l,000 m); however, the depth at which a given organism was captured is unknown because the trawl hasno closing device. We were unable to obtain a good vertical series of samples from known depth intervals with bongo nets, because of the high diversity and low densities of the plankton, A neuston net of 0.333-mm mesh was used to collect animals in the upper 20 cm of the sea surface. Organisms were sorted at sea under a dissecting microscope to divide them into homogeneous groups of species, stage, or sex as soon as possible after capture. WC placed the animals into four groups : copepods, crustaceans other than copepods, molluscs and chaetognaths, and fish. WC attempted to collect and analyze most of the groups of copepods taken in the series of trawls and neuston samples; they were identified according to Brodskii ( 1950 ) , Grice ( 1963)) Hiilsemann ( 1966)) Mori ( 1964)) Rose ( 1933)) and Sewell (1947). Lipids were extracted from live organisms in chloroform : methanol ( 2 : 1 v/v) aboard ship; all subsequent work was carried out Lmder nitrogen. Some individuals of each group were preserved for later identification ( except when the identification was easy, e.g. Gaussia princeps), and the remainder were used for lipid extraction, After weighing the lipids, they were separated by thin-layer chromatography, and the amounts of wax esters and triglycerides were determined spectrophotometrically by the procedure of Armenta ( 1964) using dichromate digestion and measurement at 350 rnp. Wax ester and triglyceride were then exprcsscd as percent of total lipid. Five replicate analyses of the lipid of several zooplankton speDISTRLBUTION OF WAX ESTERS IN PELAGIC FAUNA 229 Table 1. Lipid composition. of copepods collected during the Aries III expedition of the RV T. Washington. A is tipid per individual (mg); B is lipid (% drv weight); C is trigtyceride (% total lipid}; D is wax ester (OJO total lipid)

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1973.18.2.0227

Wax esters in tropical zooplankton and nekton and the geographical distribution of wax esters in marine copepods1

Two pelagic copepods, Calanus helgolandicus and Gaussia princeps, contained wax esters with 28 to 44 carbon atoms as major lipid constituents. In laboratory cultures of the former species, changes in nutrition (amount or species of diatoms fed) affected both the amount of total lipid and the composition of the wax esters. Thus, the wax esters serve as a reserve energy store in this organism.

https://science.sciencemag.org/content/sci/167/3924/1510.full.pdf

Wax esters in marine copepods.

Many of the common calanoid copepods in the sea contain large amounts of an unusual lipid, the wax esters (fatty acids esterified to long chain alcohols). They serve as reserve energy stores which are used during long periods of starvation, e.g. "over-wintering", and for production of eggs. Upper-water copepods have wax esters high in unsaturation, reflecting the high unsaturation of the fat ty acids of their phytoplankton diet, while deep-water copepods have more saturated wax esters.

Richard F. Lee

Papers

Importance of wax esters and other lipids in the marine food chain: Phytoplankton and copepods

Petroleum Hydrocarbons: Uptake and Discharge by the Marine Mussel Mytilus edulis

Wax esters in tropical zooplankton and nekton and the geographical distribution of wax esters in marine copepods1

Wax esters in marine copepods.

The presence of was esters in marine planktonic copepods