Depth Analysis of Fatty Acids in Two Caribbean Reef Corals
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Marine Biology 49, 197-202 (1978) MARINE BIOLOGY by Springer-Verlag 1978 Depth Analysis of Fatty Acids in Two Caribbean Reef Corals P.A. Meyer=l, J.W. Porter2 and R.L Chad ]* 1Department of AtmoRdleric and Oceanic Science, The Univerd'ry of Michigan; Ann Arbor, Michigan, USA and 2Department of Zoology, Unlver=ity of Georgia; Athen=, Georgia, USA Ab~ Total fatty acid compositions of colonies of two hermatypic, reef-building corals collected during the day-time over a depth range of 21 m were determined to assess the effect of depth-related environmental factors upon the lipid content of these organisms. No systematic changes were found, suggesting a steady-state balance be- tween algal and animal lipogenesis in these symbiotic partnerships. Stephanocoenia michelinii, a day and night feeder, contained lipids indicative of external dietary sources such as copepods, whereas Montastrea annularis, a night feeder, did not. I nlaroduction labeled animal-tissue lipid was deacy- lated, 14C was detected only in the glyc- Hermatypic reef corals are characterized erol moiety suggesting animal synthesis by a mutualistic association between of these lipids from simpler components. host cnidarians and their dinoflagellate Recent evidence, however, suggests an symbionts. A feature of this relation- algal origin for some lipid synthesis ship is the translocation of photosyn- (Patton et al., 1977), and it has been thetic products from the algae to their speculated that coral fatty acid compo- animal parters. Carbon fixed by the al- sitions are to a large extent controlled gae can appear in the host in a variety by algal biosynthesis, and that much of of forms. To date, synthesis and move- the fatty acid content of the host ani- ment has been demonstrated for sugars, mal is derived unaltered from the zoo- primarily glucose and glycerol (Musca- xanthellae (Meyers, 1977; Patton et al., tine, 1967; Muscatine and Cernichiari, 1977). 1969; Lewis and Smith, 1971; Trench, Since fatty acids can be photosynthe- 1971a, b); amino acids, for instance tically derived, whether as direct prod- alanine or leucine (Muscatine and Cerni- ucts of translocation or indirect prod- chiari, 1969; Lewis and Smith, 1971); ucts of animal synthesis from algal com- proteins (Young et al., 1971); chitin ponents, their production might be a (Young et al., 1971) ; and lipids, primari- function of depth-related changes in ly triglycerides (Muscatine and Cerni- light intensity or spectral quality. chiari, 1969; Young et al., 1971; Patton Other parameters show such trends. For et al., 1977). Von Holt and Von Holt instance, with increasing depth, light- (1968) demonstrated with the Caribbean controlled, stable carbon isotopic compo- coral Scolymia lacera (Pallas) that roughly sitions of Caribbean reef corals become one-half of all CO 2 fixed during photo- progressively lighter in 13C in both tis- synthesis and translocated into water- sues (Land et al., 1975) and in the car- soluble or alcohol-soluble extracts is bonate skeletons (Weber et al., 1976). located in the lipid fraction. This Further, colonies of the Pacific coral amount fixed into animal lipid repre- Pavona praetorta (Dana) from depths of 10 sents almost 20% of all the CO 2 fixed and 25 m show distinctive oxygen produc- during photosynthesis. Muscatine and tion and consumption rates indicative of Cernichiari (1969) found that when this physiological adaptations to their indi- vidual light regimes (Wethey and Porter, *Present address: Department of Biology, Uni- 1976a, b). These photoadaptation pat- versity of South Florida, Tampa, Florida 33612, terns reoccur in the Caribbean coral Mon- USA. tastrea annularis (Ellis and Solander) from 0025-3162/78/0049/0197/S01.20 198 P.A. Meyers et al. : Depth Analysis of Coral Lipid Jamaica (Davies, 1977; Wethey and Porter, plankton for lipid analysis for periods in preparation). This species also shows up to 9 months (Morris, 1972). a close correlation between ambient Water temperature was measured at light conditions and skeletal morphology each collection location and was found (Graus and Macintyre, 1976). to be isothermal at 26.O~ over the en- tire depth range. Salinity was deter- In view of these observed depth- mined by taking samples of water from related variations in coral composition, each depth back to the laboratory, for we were interested in determining if measurement with an American Optical Com- there existed changes in coral fatty pany Refractometer Salinometer. A small acid content with increasing depth. If salinity increase of 2~ was found in the such changes were found, they might in- top 14 m. At depths below this, salinity dicate variations in the dependence of did not vary from 35~. coral on an algal source of coral lipids, Total fatty acids in the combined cor- and hence an increasing or decreasing al and algal tissue were prepared for dependence on heterotrophically derived analysis by the procedure of Meyers et al. food over depth ranges of decreasing (1974), as modified by Meyers (1977). Ex- light supply. Differences in total fatty tracted fatty acids were converted to acid composition might also indicate their methyl esters as described by variations in the amount of translocated Meyers et al. (1974) using a procedure photosynthates with depth. adapted from that of Metcalfe et al. (1966). Analysis of these esters was by gas-liquid chromatography (Meyers, 1977). Materiels and Methods Individual components of the total fatty acid composition were identified by com- Coral samples from the seaward edge of parison of their retention times to the fringing-barrier reef at Discovery those of authentic standards. Replicate Bay, Jamaica, were hand-collected be- analyses yielded coefficients of varia- tween 10.OO and 13.OO hrs using SCUBA in tion of less than 3%. March, 1976. Small pieces of colonies of two hermatypic species, Montastrea annula- ris and Stephanocoenia michelinii (Milne- Results Edwards and Haime), were obtained at depths ranging from 3 to 24 m. S. ann~a- Fatty acid compositions for the 9 indi- ris was one of the first scleractinian vidual tissue samples of Montastrea annu- corals in which the movement of photosyn- laris from various depths are listed in thetically fixed carbon was experimental- Table I. Single samples from 4 entirely ly demonstrated (Goreau and Goreau, separate colonies of M. ann~aris were col- 1960), and, as cited above, has been the lected at 9 m in order to assess vari- object of a variety of physiological ability between colonies of this species studies, many of them being conducted at from one depth. The most abundant compo- Discovery Bay. It is a major frame build- nent in the composition of these 4 repli- er, with colonies at Discovery Bay oc- cate samples from 9 m is palmitic acid curring from sea level to 80 m (Goreau (16:O) with a mean weight percent of 61% and Wells, 1967). It is a capable plank- and a coefficient of variation of 11.3% ton feeder, expanding at night and con- of the mean. The second-most abundant tracting during the day (Porter, 1974). fatty acid is oleic (18:1). Its mean s. michelinii is similar in many respects contribution is 11.7% in these 4 samples, in size, overall shape, and depth range and its coefficient of variation is on the reef, but differs in position on 15.O% of the mean. The other major acids, the substrate and in activity periods. defined as contributing I% or more to S. mi~alinii generally grows closer to the to~al composition, show considerable the substrate, often in the understory variability. The data from these 4 sam- layer with numerous branching coral spe- ples support the findings of Meyers et al. cies overtopping it. It too is a capable (in preparation) from analysis of 8 planktivore, but most colonies are ex- replicate samples of Manicina areolata (Lin- panded fully both day and night instead naeus). Acids comprising 20% or more of of just at night. The result of this be- the total composition have considerably havior is that it is probably feeding less variability than lesser components, continuously on ambient plankton sup- and such acids may be useful in compara- plies. tive studies of the type reported here. The samples were frozen immediately No systematic change with depth of at -20~ and remained frozen until anal- collection was observed in the total fat- ysis was started in July 1976. Freezing ty acid composition of the samples of at -30~ has been shown to be a satis- Montastrea annularis analyzed in this study. factory method for preservation of zoo- Furthermore, there appeared to be no sig- P.A. Meyers et al.: Depth Analysis of Coral Lipid 199 Table i. Montastrea annularis. Fatty acid weight percent compositions of colonies from various depths Major acid Depth (m) 3 6 9 9 9 9 12 18 24 Myristic (14:O) 2.5 3.8 1.0 0.8 2.4 1.6 2.5 0.9 1.8 Palmitic (16:O) 65.4 62.5 59.6 52.0 64.5 67.8 66.4 72.3 70.3 Palmitoleic (16:1) 4.2 5.1 4.3 0 0.9 2.8 4.8 2.6 0 Stearic (18:0) 12.2 8.2 2.7 18.5 5.5 6.6 9.4 12.1 18.8 Oleic (18:1) 8.8 12.4 11.6 12.5 9.3 13.4 10.3 7.8 7.0 Linoleic (18:2) i.i 1.6 2.5 0.3 3.1 1.9 i.i 0.6 0.6 Arachidic (20:0) 0.i 0.5 0 0.5 O 0 0.5 1.0 O Eicosenoic (20:1) 0.i O O 2.4 0 0 2.0 2.8 1.5 Docosahexaenoic (22:6) O 2.2 2.6 O 3.1 0 O O 0 Table 2.