Intra-Colonial Functional Differentiation-Related Modulation of the Cellular Membrane in a Pocilloporid Coral Seriatopora caliendrum

Lipid profiling differentiates the effect of ambient microenriched copper on a coral as an advanced tool for biomonitoring

Copper can be beneficial or harmful to coral at environmentally relevant levels, making environmental monitoring a challenging. Membrane lipids make the cell a dynamic environment according to the circumstances; thus, the lipid profile should be indicative of an environmental/physiological state. To gain more insight into the copper effect on coral health and be a basis of biomonitoring, glycerophosphocholine profiling of coral exposed to microenriched copper levels was conducted in this study. The copper microenrichments resulted in a diacritical effect of decreasing carbonic anhydrase activity, following a supplementation effect, on coral lipid metabolism. Microdifferences in copper levels are critical to determine the coral metabolic state and were therefore included in this study. In addition, an excellent quantitative model correlating the coral lipid variation with the exposed copper levels or the induced physiological effect was obtained to demonstrate its performance for biomonitoring.

Comparative lipidomic analysis of phospholipids of hydrocorals and corals from tropical and cold-water regions

To expand our knowledge of lipid and fatty acid (FA) biosynthesis in marine cnidarians, polar lipidomes of hydrocorals were studied for the first time and then compared with those of soft corals from tropical and boreal regions. The structure and content of FAs and molecular species of ethanolamine, choline, serine, and inositol glycerophospholipids (PE, PC, PS, and PI, respectively), and ceramide aminoethylphosphonate (CAEP) in tropical hydrocorals (Millepora platyphylla, M. dichotoma) and the cold-water hydrocoral Allopora steinegeri were determined by chromatography and mass spectrometry. All soft corals and cold-water hydrocorals are characterized by a considerable amount of C₂₀ polyunsaturated FAs (PUFAs) elongated into C₂₂ PUFAs. In the Millepora species, the high level of 22:5n-6 and 22:6n-3 against the background of the extremely low level of C₂₀ PUFAs may be explained by a high activity of rare Δ4 desaturase. In contrast to hydrocorals, soft corals are able to elongate and further desaturate C₂₂ PUFAs into C₂₄ PUFAs. Allopora and soft corals use C₂₀ PUFAs mainly for the synthesis of PE and PC. The molecular species of PS of soft corals concentrate C₂₄ PUFAs, while in Allopora and Millepora the PS molecules are mainly based on 22:4n-6 and 22:5n-6 acyl groups, respectively. Short acyl groups (C₁₄) dominate the CAEP molecules of Allopora. In all the animals compared, most molecular species of PE and PC are ether lipids, but diacyl molecular species dominate PI. Hydrocorals and tropical soft corals contain diacyl and ether PS molecules, respectively, whereas cold-water soft corals contain a mixture of these PS forms. The high similarity of the alkyl/acyl compositions indicates a possible biosynthetic relationship between PS and PI in hydrocorals. The data obtained in our study will provide a resource to further investigate the lipid metabolism in marine invertebrates.

Using lipidomic methodology to characterize coral response to herbicide contamination and develop an early biomonitoring model

The use of omics technologies to profile an organism's systemic response to environmental changes can improve the effectiveness of biomonitoring. In cell physiology, the dynamic characteristics of membranes can be used to identify lipid profiles that detect environmental threats and assess the health problems associated with them. The efficacy of this approach was demonstrated by profiling glycerophosphocholines (GPCs, a major membrane lipid class) in the coral Seriatopora caliendrum after exposure to Irgarol 1051. A quantitative biomonitoring model for this photosystem II herbicide was developed by correlating variations in coral lipid profile with herbicide exposure levels and degree of photoinhibition. After 4 days of exposure, the predominant changes correlated with photoinhibition were an increase in lyso-GPCs and saturated GPCs and a decrease in phosphatidylcholines with unsaturated C18 chains or a polyunsaturated C22 chain. A time-course experiment showed that most of these lipid changes occurred opposite to the initial response and that the persistent changes can be attributed to photosynthetic shortages and the membrane accommodation of photoinhibition-induced oxidative conditions. These changes can help predict risk factors leading to coral bleaching. In this study, the application of a lipidomic methodology to characterize the adaptation of coral to ambient contamination serves as a basis for advancing environmental monitoring and assessment.

Modeling the effects of Irgarol 1051 on coral using lipidomic methodology for environmental monitoring and assessment

Coral is commonly selected as a bioindicator of detecting a variety of adverse factors such as photosystem II herbicide Irgarol 1051, through measuring pan-type biomarkers. To improve the effectiveness of biomonitoring, omic technologies have recently been applied to model the systemic changes in an organism. Membrane lipids create a dynamic cell structure based on the physiological state, which offers a distinct lipid profile to specifically detect environmental threats and assess the associated health risk. To demonstrate the potential of a lipidomic methodology for biomonitoring, the glycerophosphocholine (GPC) profiles of the coral Seriatopora caliendrum were observed during 3 days of Irgarol (0.1-2.0 μg/L) exposure. The lipid profile variations were modeled based on the Irgarol dose and the coral photoinhibition levels to develop an excellent quantitative model. The predominant changes correlated with the photoinhibition, decreasing the lyso-GPCs and GPCs with lower unsaturated chains and increasing GPCs with highly polyunsaturated chains, can be related to the consequence of blocking the photosynthetic electron flow based on the associated physiological roles. Other dose-specific lipid changes led to the partial exchange of PC(O-16:0/20:5) for PC(16,0/20:5) as a first-line response to counteract the membrane opening caused by Irgarol. Increased levels of the GPCs with 20:4 or 22:6 chains, which can promote mitochondrial functionality, confirmed an elevated respiration level in the coral exposed to Irgarol levels of >0.5 μg/L. Notably, plasmanylcholines with 20:4 or 22:6 chains and phosphatidylcholines with 22:6 or 22:5 chains, which can alter their membrane material properties to mitigate organelle pre-swelling and swelling in different ways, formed in the coral exposed to the 0.5 and 2.0 μg/L Irgarol levels. Such coral adaptations further predict the health risks associated with altered physiological conditions. In this study, the lipidomic methodology is demonstrated as a potential tool for environmental monitoring and assessment.

Intra-colonial diversity in the scleractinian coral, Acropora millepora: identifying the nutritional gradients underlying physiological integration and compartmentalised functioning

Scleractinian corals are colonial organisms comprising multiple physiologically integrated polyps and branches. Colonialism in corals is highly beneficial, and allows a single colony to undergo several life processes at once through physiological integration and compartmentalised functioning. Elucidating differences in the biochemical composition of intra-colonial branch positions will provide valuable insight into the nutritional reserves underlying different regions in individual coral colonies. This will also ascertain prudent harvesting strategies of wild donor-colonies to generate coral stock with high survival and vigour prospects for reef-rehabilitation efforts and captive husbandry. This study examined the effects of colony branch position on the nutritional profile of two different colony sizes of the common scleractinian, Acropora millepora. For smaller colonies, branches were sampled at three locations: the colony centre (S-centre), 50% of the longitudinal radius length (LRL) (S-50), and the colony edge (S-edge). For larger colonies, four locations were sampled: the colony centre (L-centre), 33.3% of the LRL (L-33), 66.6% of the LRL (L-66), and the edge (L-edge). Results demonstrate significant branch position effects, with the edge regions containing higher protein, likely due to increased tissue synthesis and calcification. Meanwhile, storage lipid and total fatty acid concentrations were lower at the edges, possibly reflecting catabolism of high-energy nutrients to support proliferating cells. Results also showed a significant effect of colony size in the two classes examined. While the major protein and structural lipid sink was exhibited at the edge for both sizes, the major sink for high-energy lipids and fatty acids appeared to be the L-66 position of the larger colonies and the S-centre and S-50 positions for the smaller colonies. These results confirm that the scleractinian coral colony is not nutritionally homogeneous, and while different regions of the coral colony are functionally specialised, so too are their nutritional profiles geared toward meeting specific energetic demands.

Membrane lipid profiles of coral responded to zinc oxide nanoparticle-induced perturbations on the cellular membrane

Zinc oxide nanoparticles (nZnOs) released from popular sunscreens used during marine recreation apparently endanger corals; however, the known biological effects are very limited. Membrane lipids constitute the basic structural element to create cell a dynamic structure according to the circumstance. Nano-specific effects have been shown to mechanically perturb the physical state of the lipid membrane, and the cells accommodating the actions of nZnOs can be involved in the alteration of the membrane lipid composition. To gain insight into the effects of nanoparticles on coral, glycerophosphocholine (GPC) profiling of the coral Seriatopora caliendrum exposed to nZnOs was performed in this study. Increasing lyso-GPCs, docosapentaenoic acid-possessing GPCs and docosahexaenoic acid-possessing GPCs and decreasing arachidonic acid-possessing GPCs were the predominant changes responded to nZnO exposure in the coral. A backfilling of polyunsaturated plasmanylcholines was observed in the coral exposed to nZnO levels over a threshold. These changes can be logically interpreted as an accommodation to nZnOs-induced mechanical disturbances in the cellular membrane based on the biophysical properties of the lipids. Moreover, the coral demonstrated a difference in the changes in lipid profiles between intra-colonial functionally differentiated polyps, indicating an initial membrane composition-dependent response. Based on the physicochemical properties and physiological functions of these changed lipids, some chronic biological effects can be incubated once the coral receives long-term exposure to nZnOs.