Fatty Acid Profiles of Separated Host-Symbiont Fractions From Five Symbiotic Corals: Applications of Chemotaxonomic and Trophic Biomarkers

doi:10.21203/rs.3.rs-231226/v1

Download PDF

Research Article

Fatty Acid Profiles of Separated Host-Symbiont Fractions From Five Symbiotic Corals: Applications of Chemotaxonomic and Trophic Biomarkers

https://doi.org/10.21203/rs.3.rs-231226/v1

This work is licensed under a CC BY 4.0 License

You are reading this latest preprint version

Fatty acids (FAs) are the main components of lipids in corals. We examined FA profiles from five symbiotic coral species belonging to five different genera (Acropora, Pavona, Turbinaria, Favites and Platygyra) and four different families (Acroporidae, Agariciidae, Dendrophyllidae, Faviidae). We separated symbionts from coral host tissue to investigate the interaction of FA between symbionts and host tissue. After separation, we used FA profiles, in particular specific FAs (e.g. 16:0, 18:0, 18:3n-3, 20:5n-3, 22:6n-3) and their ratios (EPA:DHA, PUFA:SFA) as biomarkers to examine chemotaxonomic indication and trophic level (autotrophy vs. heterotrophy) of each coral species. Gas chromatography-mass spectrometry (GC-MS) was performed to identify and quantify FA. For quantification, the dry weight of total lipids was used to normalize FA concentration (μg mg^-1). We found that 1) FA profiles and their abundance in coral host tissue and symbionts are distinct (with the exception of autotrophic species) 2) our five different coral species are defined by species-specific FA profiles, 3) certain FAs are useful biomarkers to determine relative trophic strategies (i.e. autotrophy and/or heterotrophy, 4) the application of FA ratios to define trophic level requires caution in research application and data interpretation. Considering the limitations of FA ratios determined herein, we suggest it to be more appropriate if these FA ratios were only applied to examine response to environmental change within species. Going forward, our study provides important FA baseline data that builds the foundation to future investigations on impacts of environmental changes on nutrition and metabolism in symbiotic corals.

General Cell Biology & Physiology

Fatty Acid Profiles

Chemotaxonomic

Trophic Biomarkers

chromatography-mass spectrometry

Lipids are essential macromolecules in marine organisms and source of energy (Bergé and Barnathan 2005; Lee et al. 2006; Parrish 2013). In comparison to other macromolecules, protein and carbohydrates (ca. 17 kJ g^− 1 and 18 kJ g^− 1, respectively), lipids have the highest energy content (ca. 39 kJ g^− 1). Additionally, lipids are important components to maintain cell membranes, and they are related to antioxidants (tocopherol, pigments), hormone regulation (e.g. ecdysone), anti-inflammatory regulation and immune system response, as well as to achieve buoyancy (neutral lipids) (Ackman 1999; Tocher 2003; Lee et al. 2006; Parrish 2013). Thus, lipids play a crucial role in the physiology of marine organisms (e.g. respiration, cell renewal and reproduction) and therefore reflect the biochemical and ecological conditions of the marine environment (Arai et al. 1993; Ward 1995; Tarrant 2005; Wang et al. 2013). In particular, fatty acids (FAs) are the main components of lipids in most marine organism, and strongly correlated with environmental conditions (Budge et al. 2006). They are transferred throughout the food web without experiencing changes in different trophic levels, which encourages their use as effective biomarkers in ecological studies (Parrish et al. 2000; Alfaro et al. 2006). Indeed, many studies have applied FAs as biomarkers in respect to various marine organisms such as bacteria, diatoms, dinoflagellates, plankton, macroalgae, invertebrates, fishes, and marine mammals (Rajendran et al. 1993; Parrish et al. 2000; Falk-Petersen et al. 2002; Howell et al. 2003; Bergé and Barnathan 2005; Lee et al. 2006; Kelly et al. 2008; Shin et al. 2008; Ju et al. 2011; Sardenne et al. 2017).

Lipids are the main biochemical compounds in corals as well, where they are used for energy storage that take up 10–50 % of the dried coral tissue (Joseph 1979; Harland et al. 1992; Harland et al. 1993; Al-Lihaibi et al. 1998; Yamashiro et al. 1999; Oku et al. 2003b; Yamashiro et al. 2005; Seemann et al. 2013). FA profiles of different coral species have been used as chemotaxonomic indicator, since FA are often species-specific (Latyshev et al. 1991; Imbs et al. 2007; Imbs et al. 2010b; Imbs et al. 2016; Lopes et al. 2016). For example, octocorals can be identified by their synthesis of 24:5n-3 and 24:6n-6, as these FA are absent in hexacorals (Svetashev and Vysotskii 1998; Imbs et al. 2010a). Symbiotic corals can be identified by high level of 18:3n-6 (GLA) and 18:4n-3 (SDA), as these FAs are present in symbiotic algae, while they are very low in non-symbiotic corals (Papina et al. 2003; Imbs et al. 2007; Imbs et al. 2010b; Imbs 2013; Lopes et al. 2016). Imbs et al. (2007) classified five different families (Acroporidae, Faviidae, Fungidae, Pocilloporidae and Poritidae) of the scleractinian corals based on their specific polyunsaturated fatty acids (PUFAs), as they found that several FAs can only be detected in certain taxonomic groups of corals.

Most scleractinian corals have symbiotic relationships with dinoflagellates, namely the family Symbiodiniaceae (hereafter ‘symbionts’), which are photosynthetic microalgae conducting carbon dioxide fixation (Wooldridge 2014). Their photosynthesis contributes significantly to the supply of biomolecules used to feed themselves and the nutrients are also translocated to the coral host for growth, reproduction, and metabolism (Muscatine et al. 1981). The main photosynthates transferred from symbionts to the coral host tissue include lipids, glycerol, glucose and amino acids (Kellogg and Patton 1983; Gates et al. 1995; Papina et al. 2003; Whitehead and Douglas 2003; Reynaud et al. 2009), where lipids predominate (Patton and Burris 1983). Of the lipids, FA in particular, is one of the most important nutrient transferred across the plant-animal interface in the aquatic food web (Dalsgaard et al. 2003; Allan et al. 2010). It has been reported that photosynthetic organisms (e.g. plants, macro- microalgae, dinoflagellates etc.) produce omega-3 PUFAs (e.g. 18:3n-3, 18:4n-3, 20:5n-3, 22:6n-3) and omega-6 PUFAs (e.g. 18:2n-6, 18:3n-6), while animals rarely do so (Papina et al. 2003; Bachok et al. 2006; Revel et al. 2016). Thus, the PUFAs synthesized by symbionts can act as biomarkers to understand the coral-symbiont relationship among coral species.

On the other hand, certain essential FAs cannot be synthesized in higher trophic positions, although they are incorporated into heterotrophic species in the marine ecosystems (Arai et al. 2015). Moreover, FAs mirror nutritional input, making it possible to use them as biomarkers to trace diet and quantify feeding relationships (Dalsgaard et al. 2003; Bay et al. 2013; Mies et al. 2018). For example, 20:5n-3 is abundant in diatoms and 22:6n-3 is abundant in dinoflagellates. Both are highly conserved in the marine food web, which allows food source tracing (Viso and Marty 1993; Scott et al. 2002; Dalsgaard et al. 2003). The ratio of 20:5n-3 to 22:6n-3 (EPA:DHA) has been used to define trophic level (autotrophy or heterotrophy) and feeding type (herbivore, omnivore, carnivore) in zooplankton (Graeve et al. 1994; Dalsgaard et al. 2003). Additionally, carnivorous zooplankton tend to have higher PUFAs than herbivorous species, hence the PUFA:SFA ratio offers an index of carnivory (Cripps and Atkinson 2000; Dalsgaard et al. 2003; Stevens et al. 2004). A few coral studies successfully applied these FA indices to define trophic level in coral reef ecosystems (Tolosa et al. 2011; Seemann et al. 2013; Salvo et al. 2017; Radice et al. 2019; Rocker et al. 2019).

Although FA profiles have shown to present excellent opportunities for chemotaxonomic and trophic biomarkers in symbiotic corals, applying FA profiles to corals and symbionts separately, as opposed to a two-organism unity, remains understudied. Specifically, symbiotic corals are able to obtain essential FAs either via autotrophy which are being translocated from symbionts, or via heterotrophy through external food sources, e.g. phytoplankton, zooplankton, particulate organic matter (Sebens et al. 1996; Ferrier-Pagès and Gattuso 1998; Anthony and Fabricius 2000; Yahel et al. 2004; Rocker et al. 2019). Furthermore, corals have a high trophic plasticity, switching between autotrophic and heterotrophic feeding strategies to cope with environmental changes (Goreau et al. 1971; Porter 1976; Muscatine et al. 1989; Anthony and Fabricius 2000; Ferrier-Pagès et al. 2003; Fabricius 2005). Therefore, their symbiotic relationship and trophic plasticity provide challenges to the application of FA biomarkers.

In this study, we characterized FA profiles from five symbiotic coral species belonging to five different genera (Acropora, Pavona, Turbinaria, Favites and Platygyra) and four different families (Acroporidae, Agariciidae, Dendrophyllidae, Faviidae). To do so, we firstly separated symbionts from coral host tissue, and then investigated the interaction of FA between symbionts and host tissue. After their separation, we used these FA profiles, in particular specific FAs and their ratios (EPA:DHA, PUFA:SFA) as biomarkers to examine chemotaxonomic indication and trophic level (autotrophy vs. heterotrophy) of each coral species. We applied only coral host tissue samples to exclude disturbance from symbionts. We tested the following hypotheses: 1) FA profiles of coral host tissue are distinctly different from those of their associated symbionts as FA profiles are organism-specific; 2) Symbiotic corals can be classified by FA profiles, as FA profiles are species-specific.; 3) Symbiotic corals have a specific trophic level which can be defined by certain FA biomarkers.

Coral sampling

In May 2016, five different symbiotic coral species (Acropora samoensis of the family Acroporidae, Pavona decussata of the family Agariciidae, Turbinaria peltata of the family Dendrophyllidae, Favites abdita and Platygyra carnosa of the family Faviidae) were collected from four mesocosm coral tanks at the Swire Institute of Marine Science (SWIMS) located at the marine reserve area of Cape d’Aguilar in Hong Kong SAR. Samples were collected in May 2016. Hong Kong has alternating wet/dry seasons; the wet season is from March to October, characterized by higher temperatures, and the dry season is from November to March. We collected our samples during the transition time between dry and wet season, with an average water temperature of 26.0 ℃. Branching and foliaceous corals (A. samoensis, P. decussata) were collected by scissors, and plate corals (T. peltata) or boulder corals (F. abdita, P. carnosa) were collected by hammer and chisel. Each nubbin was taken from different colonies (n = 4) in each tank. The collected samples were immediately rinsed with deionized water and kept frozen at -70 ℃ until further analyses. Open circulation flow-through tanks at SWIMS were used and seawater was supplied directly from the bay after a primary step of physical filtering (sand filter). The seawater included natural food sources such as plankton, particulate organic matter, hence additional feeding was not necessary. Seawater was kept running consistently through the tanks (≈ 5 l min^− 1).

Coral-Symbiont separation

For lipid analysis, the coral fragments were rinsed with buffer (5 mM EDTA), 20 µl ml^− 1 butylated hydroxytoluene in distilled water to prevent FA oxidation and development of artefacts. Coral tissue was extracted from the skeleton using an airbrush with the same buffer solution and collected in 50 ml tubes through a funnel. Slurry tissue, which included coral host tissue and symbionts was homogenized on ice with a tissue grinder for 30 s. The homogenate was centrifuged for 5 min at 4 ℃ at initially 300 rcf, increasing up to 800 rcf depending on tissue thickness, amount of mucus, and species (Table S1). The centrifugation separates symbionts (pellets) and coral tissue (supernatant). The supernatant is then transferred to another 50 ml tube and centrifuged in deionized water three times for 5 min at 4 ℃ with different velocity of centrifugation depending on the species, to eliminate any remaining symbionts. A drop of supernatant was observed under a microscope to verify no symbiotic cells remained in the coral host tissue sample. The pellet was resuspended in 20–30 ml of DI water and centrifuged at 10 rcf for 30 s to remove any carbonate residue. The supernatant was immediately transferred to another tube and then centrifuged three times for 5 min at 4 ℃ at varying velocity of centrifugation depending on species (Table S1). After the 3rd centrifugation, the pellet was recollected. Both coral host tissue and symbiont samples were kept in the freezer at -80 ℃. Prior to chemical analyses, the samples were freeze-dried and kept as powder.

Extraction lipid and fatty acids

Total lipid (TL) was extracted from dried samples of the coral host tissue and symbionts separately using Folch solution (2:1; methanol: chloroform). TL samples were spiked with internal standard (19:0; nonadecanoic acid, 1 µg l^− 1 in dichloromethane). Alkaline hydrolysis was performed at 70 ℃ in an oven for 60 min using aqueous 1 M potassium hydroxide (KOH) to release the esterified FA. The total FAs were then collected by liquid-liquid extraction using hexane:diethyl ether (9:1 v/v), and the solvent was evaporated immediately under nitrogen gas and derivatized with boron trifluoride (BF₃) at 70 ℃ for 30 min to form fatty acid methyl esters (FAMEs). FAMEs were extracted three times with hexane:diethyl ether (9:1 v/v) and then pooled. The extracted FAMEs were dried under nitrogen gas and re-suspended in dichloromethane for gas chromatography mass spectrometry (GC-MS) analysis set at electron ionization (EI) mode. A set of external standards (37 Component FAME mix, Supleco, USA) was used to identify and quantify each FAME. GC-MS (Agilent 5977A mass selective detector interfaced with an Agilent 7890B gas chromatograph) was performed using an SP-2560 capillary column (100 m x 0.25 mm, 0.2 µm film thickness, Sigma-Aldrich, USA) to detect the FA. Helium was used as the carrier gas with a flow rate of 1 ml min^− 1. A volume of 1 µl of the derivatized sample was injected into the GC with a split ratio of 1:100. The oven temperature was programmed to ramp from 100°C to 140°C at 10°C min^− 1 and from 100°C to 240°C at 4°C min^− 1. Each FAME was identified by using the target and qualifier ion listed in Table S3. FAMEs were quantified by relating the peak area of the individual FAME with the peak of the internal standard. For quantification, the dry weight of TL was used to normalize FAME concentration (µg mg^− 1).

Statistics

ANOVA test was performed using the software SPSS (ver. 19.0, IBM, NY, USA). Statistical differences among the five species were determined for TL and FA ratios by one-way analysis of variance (ANOVA) and Tukey’s post hoc test for pairwise comparison. Values of at least p < 0.05 were considered significant in the analysis. Further, we performed multivariate analyses on square root transformed value of the 19 FA profiles using the software PRIMER version 5. Hierarchical cluster analysis was conducted to assess the degree of similarity between symbionts and tissue of their coral hosts. FA profiles were compared among the five coral species by non-metric multidimensional scaling (nMDS) and analysis of similarity (ANOSIM) on the Bray-Curtis similarity index. The contribution of each fatty acid to these clusters was determined by similarity percent (SIMPER) analysis. A principal component analysis (PCA) was performed among coral species to highlight certain FA profiles.

Total lipid and fatty acids of 5 different coral species

Overall, TL in symbionts showed to be much higher than in host tissue of the five coral species (average 30.7 ± 4.2 % in symbionts, 13.5 ± 3.0 % in coral host tissue) (Fig. 1). TL of symbionts in P. carnosa showed the highest value (36.1 ± 5.5 %) compared to four other species, but it was not significantly different among the species (p > 0.05). There was no significant difference in TL of coral host tissue between A. samoensis (8.9 ± 1.4 %) and P. decussata (12.4 ± 3.9 %). TL in host tissue of A. samoensis was significantly lower compared to T. peltata (p < 0.05), F. abdita (p < 0.005) and P. carnosa (p < 0.005). There were no significant differences between P. decussata, T. peltata, F. abdita and P. carnosa.

Table 1

Fatty acid profiles in symbionts and their host tissue from five different coral species.
FA	Acropora samoensis		Pavona decussata		Turbinaria peltata		Favites abdita		Platygyra carnosa
FA	S	H	S	H	S	H	S	H	S	H
14:0	7.6 ± 1.3	3.6 ± 1.3	7.4 ± 2.6	2.9 ± 0.4	1.5 ± 0.6	0.6 ± 0.1	4.0 ± 0.5	1.0 ± 0.2	2.4 ± 1.0	1.2 ± 0.8
16:0	50.1 ± 9.7	42.0 ± 14.5	63.4 ± 24.0	46.4 ± 2.9	35.4 ± 3.5	20.7 ± 3.1	49.9 ± 2.2	30.9 ± 0.4	23.8 ± 6.1	35.3 ± 4.7
18:0	12.9 ± 5.1	19.4 ± 4.4	15.1 ± 2.4	16.9 ± 1.4	16.1 ± 1.4	23.2 ± 4.3	19.0 ± 1.8	19.7 ± 2.5	8.8 ± 2.3	17.8 ± 2.8
20:0	0.3 ± 0.1	0.8 ± 0.2	0.6 ± 0.1	0.6 ± 0.1	0.2 ± 0.02	0.1 ± 0.02	0.4 ± 0.05	0.3 ± 0.05	0.1 ± 0.02	0.5 ± 0.1
22:0	0.4 ± 0.1	0.2 ± 0.01	0.2 ± 0.04	0.2 ± 0.03	ND	ND	0.1 ± 0.0	ND	0.1 ± 0.0	ND
Σ SFA	71.2 ± 15.6	66.1 ± 20.1	86.7 ± 28.2	67.0 ± 2.1	53.1 ± 4.9	44.6 ± 5.2	73.5 ± 4.2	51.9 ± 2.3	35.2 ± 8.8	54.7 ± 5.0
16:1	5.2 ± 3.0	3.1 ± 0.5	6.5 ± 2.2	3.4 ± 0.3	1.9 ± 0.2	0.3 ± 0.02	2.0 ± 0.2	1.1 ± 0.2	1.8 ± 0.5	2.0 ± 0.8
18:1n-9	5.3 ± 1.2	3.6 ± 0.3	5.5 ± 1.9	3.9 ± 0.4	5.0 ± 0.5	2.0 ± 0.3	6.7 ± 0.3	4.0 ± 0.7	1.4 ± 0.4	2.1 ± 0.4
20:1n-9	1.1 ± 1.3	3.9 ± 0.1	ND	0.2 ± 0.04	1.3 ± 0.1	ND	0.6 ± 0.3	0.5 ± 0.1	ND	0.3 ± 0.04
22:1n-9	0.3 ± 0.1	0.3 ± 0.03	0.2 ± 0.1	0.2 ± 0.05	0.3 ± 0.1	0.2 ± 0.1	0.3 ± 0.03	0.3 ± 0.1	0.1 ± 0.02	0.1 ± 0.04
Σ MUFA	11.9 ± 4.0	11.0 ± 0.6	12.1 ± 4.1	7.7 ± 0.4	8.5 ± 0.7	2.5 ± 0.3	9.5 ± 0.4	6.0 ± 0.9	3.3 ± 0.9	4.5 ± 1.2
18:3n-3 (ALA)	5.3 ± 4.5	16.2 ± 3.7	0.3 ± 0.1	ND	5.8 ± 0.9	ND	2.8 ± 0.6	2.3 ± 0.4	ND	0.9 ± 0.4
18:4n-3 (SDA)	23.4 ± 7.3	1.7 ± 0.7	6.6 ± 2.7	0.6 ± 0.1	7.7 ± 1.3	0.8 ± 0.1	8.4 ± 1.3	0.3 ± 0.1	5.6 ± 3.5	0.7 ± 0.1
20:5n-3 (EPA)	30.9 ± 22.0	7.7 ± 4.2	6.7 ± 2.3	0.7 ± 0.1	17.7 ± 3.5	1.3 ± 0.3	11.1 ± 2.0	0.9 ± 0.3	4.2 ± 0.5	0.6 ± 0.2
22:5n-3 (DPA)	0.9 ± 0.4	1.3 ± 0.5	1.2 ± 0.8	1.2 ± 0.2	2.0 ± 0.2	0.4 ± 0.1	0.4 ± 0.2	0.2 ± 0.1	5.7 ± 2.3	6.3 ± 1.4
22:6n-3 (DHA)	44.1 ± 16.7	9.0 ± 1.3	11.6 ± 2.8	2.4 ± 0.8	22.7 ± 3.7	1.5 ± 0.2	27.2 ± 3.8	2.2 ± 1.1	11.9 ± 2.5	2.1 ± 0.4
Σ n-3 PUFA	104.6 ± 42.5	35.8 ± 9.6	26.4 ± 7.4	4.9 ± 0.8	56.0 ± 9.4	4.0 ± 0.6	49.9 ± 6.9	5.9 ± 0.8	27.4 ± 1.7	10.6 ± 1.0
18:2n-6 (LA)	2.1 ± 0.7	1.1 ± 0.1	3.8 ± 1.7	2.1 ± 0.2	1.4 ± 0.3	0.5 ± 0.1	4.8 ± 0.3	1.8 ± 0.2	1.7 ± 0.4	1.9 ± 0.4
18:3n-6 (GLA)	30.5 ± 10.7	7.4 ± 1.4	14.4 ± 5.2	4.6 ± 0.8	9.7 ± 1.7	0.8 ± 0.1	44.6 ± 6.2	4.8 ± 1.6	19.0 ± 3.9	4.1 ± 1.1
20:3n-6 (DGLA)	0.8 ± 0.4	1.4 ± 0.2	0.7 ± 0.4	0.8 ± 0.1	1.3 ± 0.3	0.5 ± 0.1	1.5 ± 0.1	1.1 ± 0.1	0.2 ± 0.1	0.6 ± 0.1
20:4n-6 (ARA)	2.9 ± 0.6	9.7 ± 1.3	2.8 ± 1.3	2.7 ± 0.3	17.4 ± 3.0	10.7 ± 2.7	9.3 ± 1.1	11.8 ± 4.1	3.7 ± 1.5	18.9 ± 4.1
22:4n-6 (AdA)	1.1 ± 0.2	2.7 ± 0.5	1.2 ± 0.1	2.3 ± 0.5	4.3 ± 0.3	1.9 ± 0.7	2.1 ± 0.3	2.1 ± 0.7	0.7 ± 0.3	2.7 ± 0.3
Σ n-6 PUFA	37.4 ± 11.9	22.3 ± 2.7	23.0 ± 7.6	12.5 ± 1.0	34.0 ± 3.8	14.3 ± 3.4	62.3 ± 7.6	21.6 ± 6.5	25.2 ± 5.9	28.2 ± 5.7
Σ PUFA	142.0 ± 38.0	58.1 ± 11.0	49.4 ± 13.7	17.4 ± 1.4	90.0 ± 12.9	18.3 ± 3.2	112.2 ± 14.2	27.5 ± 7.0	52.7 ± 7.1	38.8 ± 5.7
EPA:DHA	-	0.8 ± 0.4^a,b	-	0.3 ± 0.1^a,c	-	0.9 ± 0.1^b	-	0.5 ± 0.4^c,d	-	0.3 ± 0.04^a,b,d
PUFA:SFA	-	0.9 ± 0.2^a	-	0.3 ± 0.03^b	-	0.4 ± 0.1^c	-	0.5 ± 0.1^d	-	0.7 ± 0.1^e
Value given as mean ± SD, n = 4. FA concentration: µg mg^− 1.

Superscripts sharing different letters indicate significant differences (one-way ANOVA, Tukey’s test, p < 0.05) among five coral species.

S: symbionts, H: coral host tissue, ND: not detectable.

Out of the 37 FAMEs, we evaluated 26 types of long chain FAs (> 16C) where a total of 19 were detected (Table 1). The most predominant FA in both symbionts and coral host tissue for all species was 16:0. The concentration of 16:0 in symbionts ranged from 23.8 ± 6.1 µg mg^− 1 (P. carnosa) to 63.4 ± 24.0 µg mg^− 1 (P. decussata). In the coral host tissue, it ranged from 20.7 ± 3.1 µg mg^− 1 (T. peltata) to 46.4 ± 2.9 µg mg^− 1 (P. decussata) (Table 1). The highest concentration of 16:0 was found in both symbionts and host tissue of P. decussata. The second most dominant SFA in both symbionts and coral host tissue for all species was 18:0 (ranging from 8.8 ± 2.3 µg mg^− 1 to 19.0 ± 1.8 µg mg^− 1 in symbionts, and from 16.9 ± 1.4 µg mg^− 1 to 23.2 ± 4.3 µg mg^− 1 in coral host tissue). The 16:0 in symbionts showed to be higher than the host tissue except for those of P. carnosa, whereas 18:0 constantly showed to be higher in the host tissue than in symbionts. The major MUFA for all species was 18:1n-9, followed by 16:1. The concentration of 18:1n-9 ranged from 1.4 ± 0.4 µg mg^− 1 (P. carnosa) to 6.7 ± 0.3 µg mg^− 1 (F. abdita) in symbionts, and from 2.0 ± 0.3 µg mg^− 1 (T. peltata) to 4.0 ± 0.7 µg mg^− 1 (F. abdita) in the coral host tissue. The highest concentration of 18:1n-9 was found in both symbionts and the host tissue of F. abdita.

A. samoensis was characterized by the highest concentration of total PUFA in both symbionts and the host tissue, 142.0 ± 38.0 µg mg^− 1 and 58.1 ± 11.0 µg mg^− 1 respectively (Table 1). However, P. decussata was characterized by the lowest value in both symbionts and host tissue, 49.4 ± 13.7 µg mg^− 1 and 17.4 ± 1.4 µg mg^− 1 respectively. In general, the major PUFAs were 18:4n-3, 20:5n-3, 22:6n-3, 18:3n-6 and 20:4n-6. PUFAs namely 18:4n-3, 20:5n-3, 22:6n-3 and 18:3n-6 in symbionts for all species showed higher concentrations than the coral host tissue. The highest concentrations of PUFAs (18:4n-3, 20:5n-3, 22:6n-3, 18:3n-6) except for 20:4n-6 in the host tissue were observed in A. samoensis (1.7 ± 0.7 µg mg^− 1, 7.7 ± 4.2 µg mg^− 1, 9.0 ± 1.3 µg mg^− 1 and 7.4 ± 1.4 µg mg^− 1 respectively). However, the lowest value of 18:4n-3 was found in F. abdita (0.3 ± 0.1 µg mg^− 1), for 20:5n-3 in P. carnosa (0.6 ± 0.2 µg mg^− 1), and for 22:6n-3 and 18:3n-6 in T. peltata (1.5 ± 0.2 µg mg^− 1, 0.8 ± 0.1 µg mg^− 1, respectively). The concentration of 18:4n-3, 20:5n-3 and 22:6n-3 in symbionts of A. samoensis showed a much higher value (23.4 ± 7.3 µg mg^− 1, 30.9 ± 22.0 µg mg^− 1 and 44.1 ± 16.7 µg mg^− 1 respectively) compared to the symbionts of other species (average 7.1 ± 2.2 µg mg^− 1, 9.9 ± 2.1 µg mg^− 1 and 18.4 ± 3.2 µg mg^− 1, respectively). In addition, 18:3n-3 in symbionts of A. samoensis showed to be the highest (16.2 ± 3.7 µg mg^− 1) although values for P. decussata and T. peltata were not detectable. The concentration of 20:4n-6 in the host tissue showed higher levels than 20:5n-3 and 22:6n-3 among all species. In particular, 20:4n-6 in the host tissue of T. peltata, F. abdita and P. carnosa had the highest concentration among all PUFAs (10.7 ± 2.7 µg mg^− 1, 11.8 ± 4.1 µg mg^− 1 and 18.9 ± 4.1 µg mg^− 1 respectively), where P. carnosa had the highest level among all species.

We applied FA ratios namely 20:5n-3 to 22:6n-3 (EPA:DHA) and PUFA:SFA as biomarkers for coral feeding or determining trophic level in this study. The ratio is an indicator for trophic level (higher value indicates relatively autotrophic, lower value indicates relatively heterotrophic feeding strategies) (Rocker et al. 2019). The ratio of EPA:DHA was significantly higher in T. peltata and A. samoensis (0.9 ± 0.1, 0.8 ± 0.4, respectively) compared to the other three species (Table 1). PUFA:SFA has been suggested as indicator for carnivory (higher value indicates relatively carnivorous, lower value indicates relatively herbivorous). PUFA:SFA showed the highest value in A. samoensis (0.9 ± 0.2), followed by P. carnosa (0.7 ± 0.1), F. abdita (0.5 ± 0.1), T. peltata (0.4 ± 0.1) while P. decussata had the lowest value (0.3 ± 0.03).

Multivariate analysis of coral host and symbiont fatty acid profiles

Cluster analysis was conducted on 19 different FAs (as noted in Table 1) to evaluate whether FA profiles from symbionts and their coral host tissue are statistically separated. As shown, two groups were formed at the 75 % similarity level (Fig. 2). Group I is composed of all coral host tissues except for host tissue from A. samoensis, whereas Group II is composed of the symbionts from the five species and including the host tissue of A. samoensis.

The nMDS plot based on the 19 FA profiles clearly revealed a distinct grouping among the five different species. ANOSIM analysis also confirmed a clear separation among the groups (R = 0.999; p < 0.05) (Fig. 3). SIMPER analysis showed that each group had high similarity (> 90 %) within the group (Table S4). In all species groups, two main FAs namely 16:0 and 18:0, explained 25.1–39.8 % of the group similarity. In the T. peltata, F. abdita and P. carnosa group, 20:4n-6 explained 13.4 %, 10.8 % and 13.5 % respectively of the group similarity. While in the A. samoensis group, 18:3n-3 explained 9.5 % of the group similarity (Table S5). Dissimilarity between A. samoensis and T. peltata showed to be the highest (30.3 %), which was explained by the contribution of the following FA, in decreasing order of importance: 18:3n-3, 20:1n-9, 16:0, 18:3n-6, 22:6n-3 (Table S5). Moreover, the dissimilarity between F. abdita and P. carnosa (same family: Faviidae) was the lowest (12.6 %), which is explained by the contribution of the following FAs, in decreasing order of importance: 22:5n-3, 20:4n-6, 18:3n-3, 18:1n-9.

In PCA, PC1, PC2, and PC3 accounted for 48.5 %, 17.7 % and 13.2 % respectively (only PC1 and PC2 are shown in Fig. 4). PC1 separated A. samoensis and P. decussata (positive scores) from the other species (negative scores), explaining 48.5 % of the variability between the FA profiles of all species. The main FAs driving this distinction for A. samoensis are 18:3n-3, 20:5n-3, 22:6n-3, 20:3n-6 and 20:1n-9 (Fig. 4). A. samoensis had the highest PC1 scores, whereas T. peltata had the lowest. In contrast, PC2 separated P. decussata (negative scores) from the other species (positive scores), explaining 17.7 % of the variation in FA profiles. In particular, P. decussata was characterized by 18:2n-6, F. abdita and P. carnosa were characterized by 20:4n-6.

Our results showed TL in holobionts (unity of symbionts and coral host tissue) ranged from 19 % to 26 % in average. Indeed, a similar trend was found in Okinawan corals (14–37 %), Caribbean corals (12–32 %) and Red Sea corals (12–32 %) (Harland et al. 1993; Yamashiro et al. 1999). TL in symbionts separated from coral holobionts were much higher (27–36 %) than in coral host tissue (9–16 %). Culture experiments on five different marine dinoflagellate taxa have shown that they store 6–16 % lipid, in particular Symbiodinium microdiriaticum, which is one of the symbiotic dinoflagellates associated with corals, contained 15 % TL (Mansour et al. 1999). Therefore, it is likely that TL contents in symbionts and in their coral host separately show distinct different values. However, there are no such studies comparing TL between symbionts and their coral host tissue. TL in corals are their main source of energy storage, and symbionts can translocate lipids to their coral host to contribute to the coral’s health (Harland et al. 1993; Papina et al. 2003; Treignier et al. 2009; Imbs et al. 2014). No significant species-specific differences in TL of symbionts from the five target species was found which indicates that symbionts are limited to contain lipids as energy storage regardless of coral host species. Furthermore, it is known that the same Symbiodiniaceae genus (C1) is hosted in all of our target coral species (Wong et al. 2016). Thus, we hypothesized that lipid production and capability of storage might not be different in symbionts from either coral species. However, TL in the host tissue of F. abdita and P. carnosa were significantly higher than in host tissue of other species, which can be explained by 1) these two species might be able to feed more than other species. In fact, fed corals showed to have higher lipid contents than unfed corals (Al-Moghrabi et al. 2008; Treignier et al. 2008); 2) these two species have a higher lipid translocation rate from symbiont to the host tissue compared to the other species. On the other hand, TL in A. samoensis has shown to be significantly lower than TL in T. peltata, F. abdita, P. carnosa, which reversely may indicate A. samoensis relies on relatively less feeding.

Hierarchical cluster analysis confirmed that FA profiles and their abundance in coral host tissue and symbionts are significantly different, with the exception of A. samoensis host tissue, which categorized in the group with symbionts. Indeed, FA profiles in A. samoensis showed subtle differences between the host tissue and symbionts. In addition, PUFAs in symbionts of A. samoensis showed much higher concentration compared to symbionts of other species, since PUFAs are the main FAs that are being transferred from symbionts to the coral host tissue (Ward 1995; Papina et al. 2003; Al-Moghrabi et al. 2008). As a result, we suggest that A. samoensis relies relatively on FA from symbionts rather than on external feeding. Indeed, the Acropora species has been found to be relatively autotrophic in studies assessing FA profiles and stable isotopic values (Seemann 2013; Seemann et al. 2013; Conti-Jerpe et al. 2020). Moreover, among the studies on photosynthesis in corals found that the genus Acropora exhibited a higher maximum quantum yield (F_v/F_m) than other genera, which is indicative of higher photosynthesis efficiency (McIlroy et al. 2019). PUFAs in corals are directly coupled with photosynthesis of in hospite symbionts of corals (Oku et al. 2003a). Thus, high concentration of PUFAs in A. samoensis host tissue provides further evidence that this species is autotrophic.

Although our target species are associated with the same genus of symbionts (Wong et al. 2016), higher concentration of major PUFAs in symbionts of A. samoensis when compared to the other species could potentially be explained by different physiology that depends on the species of coral host due to specific coral morphology (i.e. growth rate, tissue thickness, polyp size) and the absence of disturbances of light penetration (i.e. particulate matter or sedimentation) in our coral tanks, which is beneficial to autotrophic species. Theoretically, symbionts in A. samoensis perform the best biochemistry via photosynthesis, where surplus FA can be transferred to the host tissue. In fact, the concentration of each FA in symbionts and the host tissue alike was very similar to each other in this species. Therefore, we confirm that A. samoensis is the most autotrophic species among the five target species. However, the PUFA:SFA ratio, which is an indicator of carnivory, was the highest in A. samoensis, which contrasts our above interpretation. Although the highest PUFA was observed in A. samoensis, SFA did not vary within the five species. This indicates that PUFA is the determinant for the high value of PUFA:SFA ratio in A. samoensis which in turn, is responsible for the contradicting indications on trophic level. Therefore, applying FA ratios to determine trophic level in corals has its limitations due to the mixture of possible food sources.

The diversity of FA profiles exhibited by our five target coral species is in accordance with previous coral FA studies (Imbs et al. 2007; Imbs et al. 2010b; Imbs et al. 2014). These studies confirmed that hard corals can be distinguished on family or subclass level on the basis of PUFA profiles. In this study, we took this even further and managed to clearly separate all our five corals on genus level by multivariate analyses using19 FA profiles including not only PUFAs but also SFAs and MUFAs. However, we should be careful when interpreting data since FA profiles in corals can be modulated by external nutritional input (Parrish et al. 2000; Dalsgaard et al. 2003; Alfaro et al. 2006), as well as by environmental factors, such as season, site, depth, and temperature (Imbs 2013; Seemann et al. 2013; Rocker et al. 2019). Furthermore, our coral samples were collected in flow mesocosm tanks, where sea water comes from the marine protected area of Hong Kong after being primarily filtered through a sand filtration system to remove suspended matter and sedimentation. This implies, coral colonies are exposed to more stable environmental conditions when compared to wild corals in the bay. Regarding season, we sampled in May that falls within the transition period between dry and wet season when it is climatically less extreme. In addition, the average water temperature was 25.7 ℃, which is close to the all-year-average water temperature (26.0 ℃ in 2016). In contrast, Imbs et al. (2007) collected their coral samples in the shallow waters of Vietnam in the South China Sea. Despite the same sampling region, season, depth etc. as our set-up, FAs in corals from natural habitats can be influenced by a variety of food sources (Imbs et al. 2010b). Therefore, we believe that the consistent and stable environmental condition in our coral tanks was the key to distinguish distinct groups among the five coral species.

The five distinct species groups are associated to 16:0 and 18:0 which are known to be transferred from glucose, symbionts and dietary sources (Imbs et al. 2011; Revel et al. 2016). Numerous studies on FA profiles of hard corals have also documented that these FAs are the most abundant FAs since their first report by Meyers (1977) (Latyshev et al. 1991; Harland et al. 1993; Yamashiro et al. 1999; Imbs et al. 2007; Imbs et al. 2010b; Imbs 2013). The 16:0 in host cnidarian tissue can be de novo synthesized from symbiont photosynthesis-driven glucose (Oku et al. 2003a; Revel et al. 2016), while a high 16:0 in symbionts is originated from their photosynthesis products. In P. decussata, 16:0 in both symbionts and their host tissue showed the highest concentration, suggesting 16:0 in this species relies on symbionts. However, 16:0 in host tissue can be originated from both symbionts and dietary sources, such as zooplankton which is known to have abundant 16:0 (Lee et al. 2006). An elevated concentration of 16:0 in the P. carnosa host tissue than in its symbionts, as oppose to the other four species, suggests that P. carnosa obtains additional 16:0 from external food sources. Upon obtaining 16:0, the biosynthesis pathway 16:0 → 18:0 → 18:1n-9 can be consistently metabolized in both symbionts and their coral host tissue (Treignier et al. 2009; Revel et al. 2016). However, the coral host cannot synthesize further from 18:1n-9 to 18:2n-6, which is the precursor of n-6 PUFA pathway, due to the lack of ∆¹²-desaturase enzyme (Dunn et al. 2012; Matthews et al. 2018). Therefore, we assume that the coral host stores energy in the form of 16:0 or 18:0 in lipids, but it is species-specific and depends on the coral’s nutrition.

Although, F. abdita and P. carnosa belong to the same family (Faviidae), their FA profiles differed. The dissimilarity between FA profiles of F. abdita and P. carnosa was the lowest (12.6 %), which indicated that these two species have comparable FA profiles relative to any other combination of species. Both species were also characterized by the highest concentration of 20:4n-6, and further exhibited the highest concentration among all the PUFAs. Unfortunately, there are very few studies on 20:4n-6 in corals. Rocker et al. (2019) documented that symbiont density has a negative correlation with 20:4n-6 concentration, which implies that this FA in the coral host tissue might not be derived from symbionts, hence 20:4n-6 suggest to be a potential indicator of coral feeding. Accordingly, a few studies surmised that 20:4n-6 in corals might originate from external food sources e.g. phytoplankton and/or herbivorous zooplankton (Seemann et al. 2013; Imbs et al. 2016). Indeed, high 20:4n-6 content in phytoplankton has been documented (Jónasdóttir 2019) Subsequently, higher 20:4n-6 in P. carnosa, F. abdita and T. peltata than in other species show that these species are more heterotrophic. In addition, P. decussata is characterized by a negative relationship with 20:4n-6, which confirms the relative autotrophy of this species.

On the other hand, the most dissimilar species coupling with P. carnosa and/or F. abdita was A. samoensis. This species was determined by the predominance of 16:0 and 18:0, followed by 18:3n-3. Especially, 18:3n-3 in A. samoensis was the most abundant of all the PUFA, and it should be noted 18:3n-3 plays a key role in further synthesizing essential n-3 PUFA. However, this FA cannot be biochemically synthesized by coral hosts due to their lack of ∆¹⁵-desaturase enzyme, indicating that 18:3n-3 originate from symbionts via photosynthesis and subsequently transferred to the coral host. Moreover, the high concentration of 18:3n-3 in the host tissue of A. samoensis indicates that this species is heavily dependent on autotrophy through its symbionts. The highest dissimilarity (30.3 %) of FA profiles among the five coral species was in between A. samoensis and T. peltata, and 18:3n-3 contributed to this separation the most. In contrast to the high concentration of 18:3n-3 in A. samoensis, no 18:3n-3 could effectively be detected in T. peltata. In previous studies, on a different species of the same genus, T. reniformis, no 18:3n-3 was observed in representatives under starvation conditions, but the concentration was high in corals fed with zooplankton (Artemia salina nauplii) (Tolosa et al. 2011). Although we did not quantify the extent of food availability in our coral tanks, a lack of zooplankton is possible. However, T. peltata showed a high concentration of 20:4n-6, which is an indicator of heterotrophic feeding (mainly phytoplankton) as previously discussed. This incompatible result is due to the abundance of different food sources (here, zooplankton vs. phytoplankton), which causes a variation of 18:3n-3 and 20:4n-6 in this species. On the other hand, symbionts of T. peltata showed the highest concentration of 18:3n-3 among all five species indicating a low translocation rate from symbionts to host tissue in this species might be responsible for our finding and unique characteristic of T. peltata. Exceptional values of 18:3n-3 due to species-specific characteristics have been reported by Papina et al. (2003). They observed low 18:3n-3 in Montipora digitata and postulated species-specific differences are responsible.

Besides a high concentration of 18:3n-3, A. samoensis is also characterized by high concentrations of 20:5n-3 and 22:6n-3. These FAs are known to be essential PUFAs in marine organisms, including corals, as they act as functional FAs for growth, reproduction, and health (Wacker and von Elert 2001; Pernet et al. 2002; Figueiredo et al. 2012). It is known 22:6n-3 is highly conserved through the food web (Scott et al. 2002; Dalsgaard et al. 2003), whereas 20:5n-3 is the dominant FA in symbionts and transferred to the coral host tissue (Revel et al. 2016). Thus, the ratio of 20:5n-3 to 22:6n-3 (EPA:DHA) has been applied to define trophic level (low value means heterotrophy, high value means autotrophy) (Rocker et al. 2019). According to the EPA:DHA ratio, A. samoensis and T. peltata are defined as relatively autotrophic, whereas P. decussata, F. abdita and P. carnosa. are relatively heterotrophic species. This ratio confirms our previous conclusions drawn from FA profiles that A. samoensis is autotrophic, F. abdita and P. carnosa are heterotrophic. However, this ratio contrasts with P. ducussata and T. peltata when compared to our findings, as well as to investigations from previous studies (Treignier et al. 2008). We may explain this controversy with the fact that corals are polytrophic, thus they can switch their trophic strategies depending on specific environmental conditions such as food sources and amount or symbiont density influenced by water quality (Dalsgaard et al. 2003; Seemann et al. 2013; Rocker et al. 2019). Thus, the most plausible reason is that not only 20:5n-3, but also 22:6n-3 in coral host tissue can be either transferred from symbionts (Revel et al. 2016) or taken up externally through planktonic food sources (20:5n-3 enriched in diatom, 22:6n-3 enriched in dinoflagellate) (Dalsgaard et al. 2003; Figueiredo et al. 2012; Revel et al. 2016).

In summary, TL and FA profiles proved a powerful tool as chemotaxonomic indicators on genus level of symbiotic corals, especially when host tissue and symbionts are investigated separately. This confirms our first two hypotheses, 1) FA profiles being distinctly different between coral host tissue and associated symbionts, and 2) FA profiles being species-specific, enabling a classification of symbiotic corals. In addition, our study provides new insights into the interaction of coral-symbionts endosymbiosis and species-specific trophic strategies. We hypothesized that the trophic level of symbiotic corals can be deduced from specific biomarkers. However, we realized that interpretation based on the accepted and widely used FA ratio indicators: EPA:DHA or PUFA:SFA to define specific trophic levels needs to be handled with more caution in research application and data interpretation. Since FA in coral host tissue can be driven by different sources such as symbionts and external food sources, interpretations may not be as straight forward as currently applied. Hence, our third hypothesis is true only when rephrased as certain FA biomarkers giving indications on the relative trophic level of symbiotic corals. Given these limitations of FA ratios, we suggest that it to be more appropriate if these FA ratios were only applied to examine response to environmental change within species. Going forward, our study provides important FA baseline data that builds the foundation to future investigation on impacts of environmental changes on nutrition and metabolism in symbiotic corals.

TL	Total lipids
FA	Fatty acid
SFA	Saturated fatty acid
MUFA	Monounsaturated fatty acid
PUFA	Polyunsaturated fatty acid
PA	Palmitic acid (16:0)
SA	Stearic acid (18:0)
OA	Oleic acid (18:1n-9)
LA	Linolenic acid (18:2n-6)
ALA	α-linolenic acid (18:3n-3)
SDA	Stearidonic acid (18:4n-3)
EPA	Eicosapentaenoic acid (20:5n-3)
DPA	Docosapentaenoic acid (22:5n-3)
DHA	Docosahexaenoic acid (22:6n-3)
LA	Linoleic acid (18:2n-6)
GLA	γ-Linolenic acid (18:3n-6)
DGLA	Dihomo-γ-linolenic acid (20:3n-6)
ARA	Arachidonic acid (20:4n-6)
AdA	Adrenic acid (22:4n-6)

Acknowledgments

We are grateful to the technical support of HKU and SWIMS staff. This study was supported by General Research Fund No.17303615 (Research Grants Council Hong Kong).

Conflict of interest

The authors declare that they have no conflict of interest.

Ackman RG (1999) Comparison of lipids in marine and freshwater organisms. In: Arts MT (ed) Lipids in Freshwater Ecosystems. Springer Science+Business Media, New York, pp263-298

Al-Lihaibi SS, Al-Sofyani AA, Niaz GR (1998) Chemical composition of corals in Saudi Red sea coast. Oceanol Acta 21:495–501

Al-Moghrabi S, Allemand D, Couret JM, Jaubert J (2008) Fatty acids of the scleractinian coral Galaxea fascicularis: effect of light and feeding. J Comp Physiol B 165:183-192

Alfaro AC, Thomas F, Sergent L, Duxbury M (2006) Identification of trophic interactions within an estuarine food web (northern New Zealand) using fatty acid biomarkers and stable isotopes. Estuar Coast Shelf Sci 70:271-286

Allan EL, Ambrose ST, Richoux NB, Froneman PW (2010) Determining spatial changes in the diet of nearshore suspension-feeders along the South African coastline: Stable isotope and fatty acid signatures. Estuar Coast Shelf Sci 87:463-471

Anthony KRN, Fabricius KE (2000) Shifting roles of heterotrophy and autotrophy in coral energetics under varying turbidity. J Exp Mar Biol Ecol 252:221-253

Arai T, Amalina R, Bachok Z (2015) Fatty acid composition indicating diverse habitat use in coral reef fishes in the Malaysian South China Sea. Biol Res 48

Arai T, Kato M, Heyward A, Ikeda Y, Iizuka T, Maruyama T (1993) Lipid composition of positively buoyant eggs of reef building corals. Coral Reefs 12:71-75

Bachok Z, Mfilinge P, Tsuchiya M (2006) Characterization of fatty acid composition in healthy and bleached corals from Okinawa, Japan. Coral Reefs 25:545-554

Bay LK, Guerecheau A, Andreakis N, Ulstrup KE, Matz MV (2013) Gene expression signatures of energetic acclimatisation in the reef building coral Acropora millepora. PLoS One 8:e61736

Bergé JP, Barnathan G (2005) Fatty acids from lipids of marine organisms: molecular biodiversity, roles as biomarkers, biologically active compounds, and economical aspects. Adv Biochem Engin/Biotechnol 96:49-125

Budge SM, Iverson SJ, Koopman HN (2006) Studying trophic ecology in marine ecosystems using fatty acids: a primer on analysis and interpretation. Mar Mamm Sci 22:759-801

Conti-Jerpe IE, Thompson PD, Wong CWM, Oliveira NL, Duprey NN, Moynihan MA, Baker DM (2020) Trophic strategy and bleaching resistance in reef-building corals. Sci Adv 6:eaaz5443

Cripps GC, Atkinson A (2000) Fatty acid composition as an indicator of carnivory in Antarctic krill, Euphausia superba. Can J Fish Aquat 57:31-37

Dalsgaard J, John MS, Kattner G, Muller-Navarra D, Hagen W (2003) Fatty acid trophic markers in the pelagic marine environment. Adv Mar Biol 46:225-340

Dunn SR, Thomas MC, Nette GW, Dove SG (2012) A lipidomic approach to understanding free fatty acid lipogenesis derived from dissolved inorganic carbon within cnidarian-dinoflagellate symbiosis. PLoS One 7:e46801

Fabricius KE (2005) Effects of terrestrial runoff on the ecology of corals and coral reefs: review and synthesis. Mar Pollut Bull 50:125-146

Falk-Petersen S, Dahl TM, Scott CL, Sargent JR, Gulliksen B, Kwasniewski S, Hop H, Millar R-M (2002) Lipid biomarkers and trophic linkages between ctenophores and copepods in Svalbard waters. Mar Ecol Prog Ser 227:187-194

Ferrier-Pagès C, Gattuso J (1998) Biomass, Production and Grazing Rates of Pico- and Nanoplankton in Coral Reef Waters (Miyako Island, Japan). Microb Ecol 35:46-57

Ferrier-Pagès C, Witting J, Tambutté E, Sebens KP (2003) Effect of natural zooplankton feeding on the tissue and skeletal growth of the scleractinian coral Stylophora pistillata. Coral Reefs 22:229-240

Figueiredo J, Baird AH, Cohen MF, Flot JF, Kamiki T, Meziane T, Tsuchiya M, Yamasaki H (2012) Ontogenetic change in the lipid and fatty acid composition of scleractinian coral larvae. Coral Reefs 31:613-619

Gates RD, Hoegh-Guldberg O, McFallngai MJ, Bil KY, Muscatine L (1995) Free amino acids exhibit anthozoan host factor activity - they induce the release of photosynthate from symbiotic dinoflagellates in-vitro. Proc Natl Acad Sci USA 92:7430-7434

Goreau TF, Goreau NI, Yonge CM (1971) Reef corals: autotrophs or heterotrophs? Biol Bull 41:247-260

Graeve M, Kattner G, Hagen W (1994) Diet-induced changes in the fatty acid composition of Arctic herbivorous copepods: Experimental evidence of trophic markers. J Exp Mar Biol Ecol 182:97-110

Harland AD, Davies PS, Fixter LM (1992) Lipid content of some Caribbean corals in relation to depth and light. Mar Biol 113:357-361

Harland AD, Navarro JC, Davies PS, Fixter LM (1993) Lipids of some Caribbean and Red Sea corals: total lipid, wax esters, triglycerides and fatty acids. Mar Biol 117:113-117

Howell KL, Pond DW, Billett DSM, Tyler PA (2003) Feeding ecology of deep-sea seastars (Echinodermata: Asteroidea): a fatty-acid biomarker approach. Mar Ecol Prog Ser 255:193–206

Imbs AB (2013) Fatty acids and other lipids of corals: Composition, distribution, and biosynthesis. Russ J Mar Biol 39:153-168

Imbs AB, Yakovleva IM, Pham LQ (2010a) Distribution of lipids and fatty acids in the zooxanthellae and host of the soft coral Sinularia sp. Fish Sci 76:375-380

Imbs AB, Demidkova DA, Dautova TN (2016) Lipids and fatty acids of cold-water soft corals and hydrocorals: a comparison with tropical species and implications for coral nutrition. Mar Biol 163

Imbs AB, Demidkova DA, Latypov YY, Pham LQ (2007) Application of Fatty Acids for Chemotaxonomy of Reef-Building Corals. Lipids 42:1035-1046

Imbs AB, Latyshev NA, Dautova TN, Latypov YY (2010b) Distribution of lipids and fatty acids in corals by their taxonomic position and presence of zooxanthellae. Mar Ecol Prog Ser 409:65-75

Imbs AB, Yakovleva IM, Latyshev NA, Pham LQ (2011) Biosynthesis of polyunsaturated fatty acids in zooxanthellae and polyps of corals. Russ J Mar Biol 36:452-457

Imbs AB, Yakovleva IM, Dautova TN, Bui LH, Jones P (2014) Diversity of fatty acid composition of symbiotic dinoflagellates in corals: evidence for the transfer of host PUFAs to the symbionts. Phytochemistry 101:76-82

Jónasdóttir SH (2019) Fatty acid profiles and production in aarine phytoplankton. Mar Drugs 17:151

Joseph JD (1979) Lipid composition of marine and estuarine invertebrates: porifera and Cnidaria. Prog Lipid Res 18:1–30

Ju SJ, Ko AR, Lee CR (2011) Latitudinal Variation of Nutritional Condition and Diet for Copepod Species, Euchaeta sp. and Pleuromamma spp., from the Northwest Pacific Ocean Using Lipid Biomarkers. Ocean Polar Res 33:349-358

Kellogg RB, Patton JS (1983) Lipid droplets, medium of energy exchange in the symbiotic anemone Condylactis gigantea: a model coral polyp. Mar Biol 75:137-149

Kelly JR, Scheibling RE, Iverson SJ, Gagnon P (2008) Fatty acid profiles in the gonads of the sea urchin Strongylocentrotus droebachiensis on natural algal diets. Mar Ecol Prog Ser 373:1-9

Latyshev NA, Naumenko NV, Svetashev VI, Latypov YY (1991) Fatty acids of reef-building corals. Mar Ecol Prog Ser 76:295-301

Lee RF, Hagen W, Kattner G (2006) Lipid storage in marine zooplankton. Mar Ecol Prog Ser 307:273-306

Lopes AR, Baptista M, Rosa IC, Dionísio G, Gomes-Pereira J, Paula JR, Figueiredo C, Bandarra N, Calado R, Rosa R (2016) “Gone with the wind”: Fatty acid biomarkers and chemotaxonomy of stranded pleustonic hydrozoans (Velella velella and Physalia physalis). Biochem Syst Ecol 66:297-306

Mansour MP, Volkman JK, Jackson AE, Blackburn SI (1999) The fatty acid and sterol composition of five marine dinoflagellates. J Phycol 35:710-720

Matthews JL, Oakley CA, Lutz A, Hillyer KE, Roessner U, Grossman AR, Weis VM, Davy SK (2018) Partner switching and metabolic flux in a model cnidarian-dinoflagellate symbiosis. Proc Royal Soc B 285:20182336

McIlroy SE, Thompson PD, Yuan FL, Bonebrake TC, Baker DM (2019) Subtropical thermal variation supports persistence of corals but limits productivity of coral reefs. Proc Royal Soc B 286:20190882

Meyers PA (1977) Fatty Acids and Hydrocarbons of Caribbean Corals. The third International Coral Reef Symposium, Miami, U.S.A.

Mies M, Güth AZ, Tenório AA, Banha TNS, Waters LG, Polito PS, Taniguchi S, Bícego MC, Sumida PYG (2018) In situ shifts of predominance between autotrophic and heterotrophic feeding in the reef-building coral Mussismilia hispida: an approach using fatty acid trophic markers. Coral Reefs 37:677-689

Muscatine L, McCloskey LR, Marian RE (1981) Estimating the daily contribution of carbon from zooxanthellae to coral animal respiration. Limnol Oceanogr 26:601-611

Muscatine L, Porter JW, Kaplan IR (1989) Resource partitioning by reef corals as determined from stable isotope composition I. δ¹³C of zooxanthellae and animal tissue vs depth. Mar Biol 100:185-193

Oku H, Yamashiro H, Onaga K (2003a) Lipid biosynthesis from [¹⁴C]-glucose in the coral Montipora digitata. Fish Sci 69:625-631

Oku H, Yamashiro H, Onaga K, Sakai K, Iwasaki H (2003b) Seasonal changes in the content and composition of lipids in the coral Goniastrea aspera. Coral Reefs 22:83-85

Papina M, Meziane T, van Woesik R (2003) Symbiotic zooxanthellae provide the host-coral Montipora digitata with polyunsaturated fatty acids. Comp Biochem Physiol B, Biochem Mol Biol 135:533-537

Parrish CC (2013) Lipids in Marine Ecosystems. ISRN Oceanography 2013:1-16

Parrish CC, Budge TAASM, Helleur RJ, Hudson ED, Pulchan K, Ramos C (2000) Lipid and Phenolic Biomarkers in Marine Ecosystems: Analysis and Applications. In: P.Wangersky (ed) The Handbook of Environmental Chemistry. Springer, Berlin Heidelberg, pp193-223

Patton JS, Burris JE (1983) Lipid synthesis and extrusion by freshly isolated zooxanthellae (symbiotic algae). Mar Biol 75:131-136

Pernet V, Gavino V, Gavino G, Anctil M (2002) Variations of lipid and fatty acid contents during the reproductive cycle of the anthozoan Renilla koellikeri. J Comp Physiol B 172:455-465

Porter JW (1976) Autotrophy, heterotrophy, and resource partitioning in Caribbean reef-building corals. Am Nat 110:731-742

Radice VZ, Brett MT, Fry B, Fox MD, Hoegh-Guldberg O, Dove SG (2019) Evaluating coral trophic strategies using fatty acid composition and indices. PLoS One 14:e0222327

Rajendran N, Suwa Y, Urushigawa Y (1993) Distribution of phospholipid ester-linked fatty acid biomarkers for bacteria in the sedirnent of Ise Bay, Japan. Mar Chem 42:39-56

Revel J, Massi L, Mehiri M, Boutoute M, Mayzaud P, Capron L, Sabourault C (2016) Differential distribution of lipids in epidermis, gastrodermis and hosted Symbiodinium in the sea anemone Anemonia viridis. Comp Biochem Physiol Part A Mol Integr Physiol 191:140-151

Reynaud S, Martinez P, Houlbrèque F, Billy I, Allemand D, Ferrier-Pagès C (2009) Effect of light and feeding on the nitrogen isotopic composition of a zooxanthellate coral: role of nitrogen recycling. Mar Ecol Prog Ser 392:103-110

Rocker MM, Willis BL, Francis DS, Bay LK (2019) Temporal and spatial variation in fatty acid composition in Acropora tenuis corals along water quality gradients on the Great Barrier Reef, Australia. Coral Reefs 38:215-228

Salvo F, Hamoutene D, Hayes VEW, Edinger EN, Parrish CC (2017) Investigation of trophic ecology in Newfoundland cold-water deep-sea corals using lipid class and fatty acid analyses. Coral Reefs 37:157-171

Sardenne F, Kraffe E, Amiel A, Fouché E, Debrauwer L, Ménard F, Bodin N (2017) Biological and environmental influence on tissue fatty acid compositions in wild tropical tunas. Comp Biochem Physiol Part A Mol Integr Physiol 204:17-27

Scott CL, Kwasniewski S, Falk-Petersen S, Sargent JR (2002) Species differences, origins and functions of fatty alcohols and fatty acids in the wax esters and phospholipids of Calanus hyperboreus, C. glacialis and C. finmarchicus from Arctic waters. Mar Ecol Prog Ser 235:127–134

Sebens KP, Vandersall KS, Savina LA, Graham KR (1996) Zooplankton capture by two scleractinian corals, Madracis mirabilis and Montastrea cavernosa, in a field enclosure. Mar Biol 127:303-317

Seemann J (2013) The use of ¹³C and ¹⁵N isotope labeling techniques to assess heterotrophy of corals. J Exp Mar Biol Ecol 442:88-95

Seemann J, Sawall Y, Auel H, Richter C (2013) The use of lipids and fatty acids to measure the trophic plasticity of the coral Stylophora subseriata. Lipids 48:275-286

Shin PKS, Yip KM, Xu WZ, Wong WH, Cheung SG (2008) Fatty acid as markers to demonstrating trophic relationships among diatoms, rotifers and green-lipped mussels. J Exp Mar Biol Ecol 357:75-84

Stevens CJ, Deibel D, Parrish CC (2004) Species-specific differences in lipid composition and omnivory indices in Arctic copepods collected in deep water during autumn (North Water Polynya). Mar Biol 144:905-915

Svetashev VI, Vysotskii MV (1998) Fatty acids of Heliopora coerulea and chemotaxonomic significance of tetracosapolyenoic acids in coelenterates. Comp Biochem Physiol B, Biochem Mol Biol 119B:73–75

Tarrant AM (2005) Endocrine-like signaling in Cnidarians: current understanding and implications for ecophysiology. Integr Comp Biol 45

Tocher DR (2003) Metabolism and functions of lipids and fatty acids in teleost fish. Rev Fish Sci Aquac 11:107-184

Tolosa I, Treignier C, Grover R, Ferrier-Pagès C (2011) Impact of feeding and short-term temperature stress on the content and isotopic signature of fatty acids, sterols, and alcohols in the scleractinian coral Turbinaria reniformis. Coral Reefs 30:763-774

Treignier C, Grover R, Ferrier-Pagès C (2008) Effect of light and feeding on the fatty acid and sterol composition of zooxanthellae and host tissue isolated from the scleractinian coral Turbinaria reniformis. Limnol Oceanogr 53:2702-2710

Treignier C, Tolosa I, Grover R, Reynaud S, Ferrier-Pagès C (2009) Carbon isotope composition of fatty acids and sterols in the scleractinian coral Turbinaria reniformis: Effect of light and feeding. Limnol Oceanogr 54:1933-1940

Viso A-C, Marty J-C (1993) Fatty acids from 28 marine microalgae. Phytochemistry 34:1521-1533

Wacker A, von Elert E (2001) Polyunsaturated fatty acids: evidence for non-substitutable biochemical resources in Daphnia galeata. Ecology 82:2507-2520

Wang LH, Lee HH, Fang LS, Mayfield AB, Chen CS (2013) Fatty acid and phospholipid syntheses are prerequisites for the cell cycle of Symbiodinium and their endosymbiosis within sea anemones. PLoS One 8:e72486

Ward S (1995) Two patterns of energy allocation for growth, reproduction and lipid storage in the scleractinian coral Pocillopora damicornis. Coral Reefs 14:87-90

Whitehead LF, Douglas AE (2003) Metabolite comparisons and the identity of nutrients translocated from symbiotic algae to an animal host. J Exp Biol 206:3149-3157

Wong JCY, Thompson P, Xie JY, Qiu J-W, Baker DM (2016) Symbiodinium clade C generality among common scleractinian corals in subtropical Hong Kong. Reg Stud Mar Sci 8:439-444

Wooldridge SA (2014) Differential thermal bleaching susceptibilities amongst coral taxa: re-posing the role of the host. Coral Reefs 33:15-27

Yahel R, Yahel G, Genin A (2004) Near- bottom depletion of zooplankton over coral reefs: I: diurnal dynamics and size distribution. Coral Reefs 24:75-85

Yamashiro H, Oku H, Onaga K (2005) Effect of bleaching on lipid content and composition of Okinawan corals. Fish Sci 71:448-453

Yamashiro H, Oku H, Higa H, Chinen I, Sakai K (1999) Composition of lipids, fatty acids and sterols in Okinawan corals. Comp Biochem Physiol B, Biochem Mol Biol 122:397-407

MBKimSupplement.docx

Download PDF

Reviews received at journal
18 Mar, 2021
Reviewers invited by journal
14 Feb, 2021
Editor assigned by journal
11 Feb, 2021
First submitted to journal
10 Feb, 2021

You are reading this latest preprint version

Fatty Acid Profiles of Separated Host-Symbiont Fractions From Five Symbiotic Corals: Applications of Chemotaxonomic and Trophic Biomarkers

Status:

Version 1

Abstract

Figures

Introduction

Materials and Methods

Coral sampling

Coral-Symbiont separation

Extraction lipid and fatty acids

Statistics

Results

Total lipid and fatty acids of 5 different coral species

Multivariate analysis of coral host and symbiont fatty acid profiles

Discussion

Abbreviations

Declarations

References

Supplementary Files

Status:

Version 1