Heterotrophic Feeding Research Articles

Epizoic acoelomorph flatworms impair zooplankton feeding by the scleractinian coral Galaxea fascicularis

SummaryMany scleractinian coral species host epizoic acoelomorph flatworms, both in aquaculture and in situ. These symbiotic flatworms may impair coral growth and health through light-shading, mucus removal and disruption of heterotrophic feeding. To quantify the effect of epizoic flatworms on zooplankton feeding, we conducted video analyses of single polyps of Galaxea fascicularis (Linnaeus 1767) grazing on Artemia nauplii in the presence and absence of symbiotic flatworms. 18S DNA analysis revealed that flatworms inhabiting G. fascicularis belonged to the genus Waminoa (Convolutidae), which were hosted at a density of 3.6±0.4 individuals polyp−1. Polyps hosting flatworms exhibited prey capture rates of 2.2±2.5, 3.4±4.5 and 2.7±3.4 nauplii polyp−1 30 min−1 at prey concentrations of 250, 500 and 1,000 nauplii L−1, respectively. Polyps that had their flatworms removed displayed prey capture rates of 2.7±1.6, 4.8±4.1 and 16.9±10.3 nauplii polyp−1 30 min−1. Significant main and interactive effects of flatworm presence and ambient prey concentration were found, reflected by the fact that flatworms significantly impaired host feeding rates at the highest prey density of 1,000 nauplii L−1. In addition, flatworms displayed kleptoparasitism, removing between 0.1±0.3 and 0.6±1.1 nauplii 30 min−1 from the oral disc of their host, or 5.3±3.3 to 50.0±2.1% of prey acquired by the coral. We suggest classifying the coral-associated Waminoa sp. as an epizoic parasite, as its presence may negatively affect growth and health of the host.

Controlling Effects of Irradiance and Heterotrophy on Carbon Translocation in the Temperate Coral Cladocora caespitosa

Temperate symbiotic corals, such as the Mediterranean species Cladocora caespitosa, live in seasonally changing environments, where irradiance can be ten times higher in summer than winter. These corals shift from autotrophy in summer to heterotrophy in winter in response to light limitation of the symbiont’s photosynthesis. In this study, we determined the autotrophic carbon budget under different conditions of irradiance (20 and 120 µmol photons m−2 s−1) and feeding (fed three times a week with Artemia salina nauplii, and unfed). Corals were incubated in H13CO3 −-enriched seawater, and the fate of 13C was followed in the symbionts and the host tissue. The total amount of carbon fixed by photosynthesis and translocated was significantly higher at high than low irradiance (ca. 13 versus 2.5–4.5 µg cm−2 h−1), because the rates of photosynthesis and carbon fixation were also higher. However, the percent of carbon translocation was similar under the two irradiances, and reached more than 70% of the total fixed carbon. Host feeding induced a decrease in the percentage of carbon translocated under low irradiance (from 70 to 53%), and also a decrease in the rates of carbon translocation per symbiont cell under both irradiances. The fate of autotrophic and heterotrophic carbon differed according to irradiance. At low irradiance, autotrophic carbon was mostly respired by the host and the symbionts, and heterotrophic feeding led to an increase in host biomass. Under high irradiance, autotrophic carbon was both respired and released as particulate and dissolved organic carbon, and heterotrophic feeding led to an increase in host biomass and symbiont concentration. Overall, the maintenance of high symbiont concentration and high percentage of carbon translocation under low irradiance allow this coral species to optimize its autotrophic carbon acquisition, when irradiance conditions are not favourable to photosynthesis.

Fatty acid composition as an indicator of possible sources of nutrition for soft corals of the genusSinularia(Alcyoniidae)

Fatty acids (FAs) composition of eight zooxanthellate soft corals,Sinularia leptoclados, S. flexibilis, S.aff.deformis, S. lochmodes, S. cf.muralis, S. densa, S. notandaandS. cruciatacollected in Van Phong Bay (Vietnam) were studied to identify possible origin of unsaturated FAs. The main FAs were 14:0, 16:0, 7-Me-16:1n-10, 16:1n-7, 16:2n-7, 18:0, 18:1n-9, 18:4n-3, 20:4n-6, 20:5n-3, 22:6n-3, 24:5n-6 and 24:6n-3. On the average, saturated, monounsaturated, and polyunsaturated FAs (PUFAs) contributed 35.6, 6.2 and 54.0% of total coral FAs, respectively. PUFAs of n-6 series predominated in all animals (n-6/n-3 > 1.6). The content of 20:4n-6 varied from 10.2 to 23.8%. The main n-3 PUFA was 18:4n-3 (on the average, 5.4%); the contribution of 20:5n-3 and 22:6n-3, typical PUFAs of marine organisms, was not more than 2.4 and 3.9%, respectively. InSinularia, PUFAs were produced by endosymbiotic dinoflagellates (zooxanthellae) and the coral host tissue, or obtained with food. Zooxanthellae can be considered as the source of C16PUFAs and 18:4n-3. The coral host synthesized 18:2n-7, 24:5n-6 and 24:6n-3 acids. The low content of 18:1n-7, saturated odd-chain FAs and saturated methyl-branched FAs indicated a negligible contribution of bacteria to total lipids ofSinularia. A comparison of the levels of diatom and dinoflagellate FA markers in coral and plankton lipids showed eukaryotic microalgae to play a secondary role in feeding ofSinularia. The high level of 20:4n-6 may be considered as an indicator of heterotrophic feeding ofSinularia.

Heterotrophic feeding as a newly identified survival strategy of the dinoflagellate Symbiodinium

Survival of free-living and symbiotic dinoflagellates (Symbiodinium spp.) in coral reefs is critical to the maintenance of a healthy coral community. Most coral reefs exist in oligotrophic waters, and their survival strategy in such nutrient-depleted waters remains largely unknown. In this study, we found that two strains of Symbiodinium spp. cultured from the environment and acquired from the tissues of the coral Alveopora japonica had the ability to feed heterotrophically. Symbiodinium spp. fed on heterotrophic bacteria, cyanobacteria (Synechococcus spp.), and small microalgae in both nutrient-replete and nutrient-depleted conditions. Cultured free-living Symbiodinium spp. displayed no autotrophic growth under nitrogen-depleted conditions, but grew when provided with prey. Our results indicate that Symbiodinium spp.'s mixotrophic activity greatly increases their chance of survival and their population growth under nitrogen-depleted conditions, which tend to prevail in coral habitats. In particular, free-living Symbiodinium cells acquired considerable nitrogen from algal prey, comparable to or greater than the direct uptake of ammonium, nitrate, nitrite, or urea. In addition, free-living Symbiodinium spp. can be a sink for planktonic cyanobacteria (Synechococcus spp.) and remove substantial portions of Synechococcus populations from coral reef waters. Our discovery of Symbiodinium's feeding alters our conventional views of the survival strategies of photosynthetic Symbiodinium and corals.

Distribution patterns and nutritional contributions of algal symbionts in the sea anemone Anthopleura xanthogrammica

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 453:79-94 (2012) - DOI: https://doi.org/10.3354/meps09602 Distribution patterns and nutritional contributions of algal symbionts in the sea anemone Anthopleura xanthogrammica Michael R. Levine*, Gisèle Muller-Parker Shannon Point Marine Center and Department of Biology, Western Washington University, Anacortes, Washington 98221, USA *Email: mrlevinevt@gmail.com ABSTRACT: The Pacific intertidal sea anemone Anthopleura xanthogrammica hosts 2 algal symbionts, zoochlorellae Elliptochloris marina and zooxanthellae Symbiodinium muscatinei, either alone or co-occurring. Previous studies have suggested that zoochlorellae and zooxanthellae represent ‘cool’ and ‘warm’ symbionts with respect to their field distributions, and that these symbionts may differ in their nutritional contributions to their host. We examined the seasonal distribution, density, and growth of these symbionts in A. xanthogrammica tentacles from tidepools and surge channels on the Olympic peninsula in Washington State, USA, measured temperature variation between these microhabitats, and estimated the contributions of zoochlorellae to A. xanthogrammica diet. Tentacles containing dense concentrations of zoochlorellae were found in both tidepools and surge channels at the lower intertidal limit of anemone occurrence. At the upper intertidal limit, tentacles containing primarily zoochlorellae were found in tidepools, and tentacles containing primarily zooxanthellae were found in surge channels. More extreme high temperatures in the upper surge channel may limit the distribution of zoochlorellae and favor a higher proportion of zooxanthellae in this microhabitat. Despite pronounced seasonal fluctuations in temperature, symbiont composition, density, and dietary carbon sources remained remarkably consistent. Stable isotope analysis showed that A. xanthogrammica received a greater proportion of dietary carbon from zoochlorellae (62−70%) than from heterotrophic feeding on Mytilus californianus mussels (31−38%). This study shows that dense concentrations of zoochlorellae are found in A. xanthogrammica tentacles in cooler microhabitats, and that this symbiont can contribute substantially to anemone nutrition. KEY WORDS: Zoochlorellae · Zooxanthellae · Temperate symbiosis · Anthopleura xanthogrammica Full text in pdf format PreviousNextCite this article as: Levine MR, Muller-Parker G (2012) Distribution patterns and nutritional contributions of algal symbionts in the sea anemone Anthopleura xanthogrammica. Mar Ecol Prog Ser 453:79-94. https://doi.org/10.3354/meps09602 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 453. Online publication date: May 07, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

A high resolution δ13C record in a modern Porites lobata coral: Insights into controls on skeletal δ13C

δ13C was determined at a high spatial resolution by secondary ion mass spectrometry (SIMS) across a 1year section of a modern Porites lobata coral skeleton from Hawaii. Skeletal δ13C is dominated by large oscillations of 5–7‰ that typically cover skeletal distances equivalent to periods of ∼14–40days. These variations do not reflect seawater temperature and it is unlikely that they reflect variations in the δ13C of local seawater. We observe no correlation between skeletal δ13C and the pH of the calcification fluid (estimated from previous measurements of skeletal δ11B). We conclude that either the proportion of skeletal carbon derived from metabolic CO2 is not reflected by estimated ECF pH (as the [CO2] in the overlying coral tissue varies) and/or the δ13C composition of the metabolic CO2 is highly variable. We also observe no correlation between skeletal δ13C and previous δ18O SIMS measurements. Variations in skeletal δ13C and δ18O do not have a common timing, providing no evidence that skeletal δ13C and δ18O vary in response to a single factor. This suggests that skeletal δ13C is principally driven by variations in the δ13C composition of metabolic CO2 rather than by the abundance of metabolic CO2, which would also affect skeletal δ18O. The δ13C composition of metabolic CO2 reflects the processes of photosynthesis, heterotrophic feeding and respiration in the overlying coral tissue. Corals catabolise stored lipid reserves to meet energetic demands when photosynthesis conditions are sub-optimal. Variations in the amounts and types of reserves utilised could induce changes in the δ13C composition of metabolic CO2 and the resultant skeleton which are temporally offset from skeletal δ18O records.

The effects of symbiotic state on heterotrophic feeding in the temperate sea anemone Anthopleura elegantissima

The temperate sea anemone Anthopleura elegantissima is facultatively symbiotic with unicellular algae. Symbiotic A. elegantissima can supplement heterotrophic feeding with excess photosynthate from their algal partners, while asymbiotic individuals must rely solely on heterotrophy. A. elegantissima individuals were collected from Swirl Rocks, Washington (48°25′6″ N, 122°50′58″ W) in July 2010, and prey capture and feeding characteristics were measured to determine whether asymbiotic individuals are more efficient predators. Feeding abilities were then measured again after a 3-week exposure to full sunlight or shaded conditions. Freshly collected asymbiotic anemones had larger nematocysts, but symbiotic individuals showed greater nematocyte sensitivity. Sunlight enhanced digestion and reduced cnida density in all anemones regardless of symbiotic state. Results suggest that the phototropic potential of A. elegantissima, as influenced by symbiotic condition, has little effect on heterotrophic capacity. The anemones appear to maximize heterotrophic energy input independent of the presence or identity of their algal symbionts.

Water Flow Affects Zooplankton Feeding by the Scleractinian CoralGalaxea fascicularison a Polyp and Colony Level

Several factors may affect heterotrophic feeding of benthic marine invertebrates, including water flow rate and polyp context (i.e., the presence of neighbouring polyps). We tested the interactive effects of water flow rate and polyp context on zooplankton feeding by the scleractinian coralGalaxea fascicularis. Single polyps and colonies were incubated in a flow cell for 30 minutes with an ambientArtemianauplii concentration of 10,000 L−1and water flow rates ranging from 1.25 to 40 cm s−1. Water flow rate and polyp context showed significant main and interactive effects on feeding rates ofG. fascicularispolyps. More specifically, feeding rates were optimal at flow rates of 1.25 cm s−1for single polyps and 5 to 10 cm s−1for polyps inhabiting colonies. The presence of epizoic acoelomorph flatworms may have negatively affected the observed feeding rates, especially at high flow. Our results demonstrate that water flow affects coral feeding and thus heterotrophic nutrient input at both a polyp and colony level. These findings are of relevance to our understanding of how biotic and abiotic factors interact on coral heterotrophy and may serve to optimise coral aquaculture.

Influence of heterotrophic feeding on the survival and tissue growth rates of Galaxea fascicularis (Octocorralia: Occulinidae) in aquaria

The propagation and growth of scleractinian corals under aquaculture conditions could reduce the pressure of extractive fishing for ornamental species. To fulfil their growth requirements, corals rely on a combination of photosynthetic products translocated from symbiotic zooxanthellae, and particulate heterotrophic sources. In aquaculture, the latter is provided by Artemia sp. nauplii as they provide adequate nutrition and promote optimal growth and survival. In this study, we evaluated feeding rates and estimated growth rates of cultured scleractinian corals. Polyp and colonial nubbins of the coral Galaxea fascicularis were randomly assigned to each of three tanks within three naturally lit systems under standard conditions. Corals were subjected to three feeding treatments: i) fed once or ii) three times weekly, or iii) unfed until the end of the trial (two months). The survival rates were 98.7% and 100% for the colonial and polyp forms, respectively. Ingestion rates of Artemia salina nauplii between the three feeding treatments were significantly higher for specimens fed 3-times a week compared to those two treatments involving a lower feeding frequency (individual prey items polyp−1 20min−1: 8 vs. ≤ 4, respectively), but growth rates of colonial and polyp forms were not significantly different with respect to feeding frequency. Mean rate of new polyp growth was ca. 4 polyps nubbin−1 week−1 for colonial form and ca. 1 polyp polyp−1 week−1 for the polyp form. The high survival and growth rates of G. fascicularis, coupled with an apparent low heterotrophic prey requirement, make this species an ideal candidate for commercial propagation in aquaculture.

Zooplanktivory ameliorates the effects of ocean acidification on the reef coral Porites spp

I tested the hypothesis that the effects of high pCO2 and temperature on massive Porites spp. (Scleractinia) are modified by heterotrophic feeding (zooplanktivory). Small colonies of massive Porites spp. from the back reef of Moorea, French Polynesia, were incubated for 1 month under combinations of temperature (29.3°C vs. 25.6°C), pCO2 (41.6 vs. 81.5 Pa), and feeding regimes (none vs. ad libitum access to live Artemia spp.), with the response assessed using calcification and biomass. Area‐normalized calcification was unaffected by pCO2, temperature, and the interaction between the two, although it increased 40% with feeding. Biomass increased 35% with feeding and tended to be higher at 25.6°C compared to 29.3°C, and as a result, biomass‐normalized calcification statistically was unaffected by feeding, but was depressed 12–17% by high pCO2, with the effect accentuated at 25.6°C. These results show that massive Porites spp. has the capacity to resist the effects on calcification of 1 month exposure to 81.5 Pa pCO2 through heterotrophy and changes in biomass. Area‐normalized calcification is sustained at high pCO2 by a greater biomass with a reduced biomass‐normalized rate of calcification. This mechanism may play a role in determining the extent to which corals can resist the long‐term effects of ocean acidification.

Toxigenic Pfiesteria species—Updates on biology, ecology, toxins, and impacts

The genus Pfiesteria includes two toxigenic species, Pfiesteria piscicida and Pfiesteria shumwayae, that are thinly thecate dinoflagellates with apparently cosmopolitan distribution, especially in shallow, poorly flushed, eutrophic estuaries. They are heterotrophic prey generalists that typically feed via phagotrophy and prefer live fish or their fresh tissues as food. They can also engage in limited mixotrophy through temporary retention of kleptochloroplasts from algal prey. Toxicity is highly variable among strains, ranging from apparently nontoxic to highly toxic. Some strains produce a group of hydrophilic toxins with metal-mediated free radical production. Various metals can be involved in the toxin congeners, and the purified toxins are highly labile. These toxins can adversely affect mammalian cells as well as fish. Toxic strains are capable of killing fish by both toxins and physical attack from feeding upon epidermis and other tissues. Non-inducible strains do not produce sufficient toxin to kill fish, but some are capable of causing larval fish death by physical attack. From 1991 to 1998, Pfiesteria spp. were linked to major kills of juvenile Atlantic menhaden ( Brevoortia tyrannus), mostly at densities of ≥4(3) × 10 2 to 10 3 (rarely, 10 4) flagellate cells mL −1. These kills mainly occurred in the second largest and largest estuaries on the U.S. mainland, especially two main tributaries of the Albemarle-Pamlico Estuarine System, following decades of hurricane-free conditions. Between kills, Pfiesteria abundance was low in surface waters (<10 cells mL −1), and the available evidence suggests that the populations were mostly in the lower water column and within surficial sediments. Apparently highly sensitive to scouring effects from major storms, Pfiesteria populations have been sparse in the affected estuaries since several hurricanes struck the Albemarle-Pamlico in the late 1990s. Recent research highlights include characterization of a novel group of Pfiesteria toxins, culture of a toxigenic strain on a sterile fish cell line, axenic culture on a semi-defined medium, the discovery of a new mode of heterotrophic feeding in dinoflagellates as manifested by Pfiesteria, and other advances in understanding the nutritional ecology and prey acquisition of these harmful dinoflagellates.

Summer autotrophy and winter heterotrophy in the temperate symbiotic coral Cladocora caespitosa

Carbon and nitrogen isotope ratios (δ13C and δ15N) were determined in the zooxanthellae, host tissue, and whole symbiotic association of the symbiotic temperate coral Cladocora caespitosa, as well as in the different components of the coral's potential food sources (plankton, particulate organic matter in seawater and in the sediment). Data were collected both in winter and summer at three different locations, to assess the extent of auto‐ and heterotrophy in this species and get a better understanding of the functioning of temperate symbioses. There was a marked seasonal difference in the signature of the zooxanthellae and host tissue, highlighting two clear feeding patterns. In summer, δ13C signatures of the coral host and the zooxanthellae were similar (‐17‰) and very different from the signature of the food sources (from ‐21‰ to ‐25‰), suggesting that corals were relying on autotrophy for the acquisition of carbon. δ15N values also suggested that nitrogen was not acquired through feeding. Conversely, in winter, the δ13C signature of the host decreased by ca. ‐23‰ to ‐28‰, and was more comparable to the signature of the external food sources (between ‐24‰ and ‐25‰), suggesting a substantial reliance of C. caespitosa on external food sources during this season. There was also a 3‰ enrichment between the δ15N signatures of the food (4‐5‰) and the signature of the symbiotic association (7‐8‰), suggesting that nitrogen was also acquired through feeding. Overall, these results give evidence that C. caespitosa and temperate corals in general derive a large fraction of their energy from heterotrophic feeding in winter.

Epizoic acoelomorph flatworms compete with their coral host for zooplankton

Satisfying nutrient requirement of corals is still a major constraint for maintaining corals in marine aquariums. Corals are polytrophic in nature. Heterotrophic feeding on zooplankton is one of the corals’ strategies to overcome nutrient deficiency. Artemia salina nauplii are commonly used as biocarriers for many fish larvae in aquaculture and can also serve as a biocarrier for coral in aquariums, provided coral acceptability, optimal feeding rate, and digestibility of the nauplii are well understood. Feeding rate and digestibility of coral fed on A. salina nauplii at 100, 2,000, 4,000, 6,000, and 10,000 ind. l-1 under light and dark conditions was assessed in this study. The maximum feeding rates of Galaxea fascicularis under light and dark conditions was 113.6 ind. polyp-1 h-1 and 76.9 ind. polyp-1 h-1, respectively. The daily feeding rates of G. fascicularis varies and depends on nauplii density. Light plays an important role in coral feeding. Nevertheless, the quantity of A. salina nauplii consumed by the coral under light and dark conditions was not significantly different (P > 0.05). A. salina nauplii are well accepted by G. fascicularis. Complete nauplii digestion was observed after 180 min. Digestibility of A. salina nauplii by G. fascicularis was positively correlated with digestion time.

Heterotrophic and autotrophic assimilation of fatty acids by two scleractinian corals, Montastraea faveolata and Porites astreoides

We determined the source of fatty acids in scleractinian corals by separately measuring and comparing the δ13C values of fatty acids in zooxanthellae and coral hosts from two scleractinian coral species (Montastraea faveolata and Porites astreoides) from reefs of the Florida Reef Tract. Using an isotopic mass balance approach, we show that zooxanthellae are the dominant source of fatty acids and that in many colonies heterotrophic feeding can be an important and significant source of essential ω3 fatty acids for corals. There is considerable variability in feeding behavior within species, between species, and within single reef sites. In individual colonies, essential ω3 fatty acids and energy resources such as triglycerides can be acquired from separate dietary sources, showing the importance of resource partitioning within the coral animal. Consistently, individual coral colonies acquire most of their energy‐rich saturated fatty acids from their symbiotic zooxanthellae. The particular feeding mode by which corals acquire their fatty acids appears to be specific to each coral colony. The ability of corals to modulate their feeding modes under different environments may provide an adaptive mechanism to sustain growth under stressful conditions.

Optimizing microalgal biomass for biofuel production: the impact of glucose feeding on lipid and fatty acid profiles in Chlorella zofingiensis

Evaluation of: Liu J, Huang J, Sun Z et al. Differential lipid and fatty acid profiles of photoautotrophic and heterotrophic Chlorella zofingiensis: assessment of algal oils for biodiesel production. Bioresour. Technol. 102(1), 106–110 (2011) (In press).The production of environmentally friendly biofuels has become a major focus of scientists and politicians since the detrimental effects of fossil fuel combustion have become increasingly apparent. One of the established technologies today in this field is the production of biodiesel derived from plant lipids. The study of Jin Liu et al. investigated the differential lipid and fatty acid profiles of the microalga Chlorella zofingiensis in dependence of photoautotrophic or heterotrophic culturing conditions, respectively. The work showed that heterotrophic glucose feeding leads to far higher lipid yields and a strong increase of the relative amount of neutral lipids such as triacylglycerol. The fatty acid profile indicates that oil from heterotrophic C. zofingiensis cells should be of a similar quality as oil from crop plants. The authors conclude that heterotrophic culturing of C. zofingiensis could have a great potential for profitable biodiesel production in the future.

Influence of heterotrophic feeding on the sexual reproduction of Pocillopora verrucosa in aquaria

Recent research has shown that heterotrophic feeding has a strong effect on both maintenance and growth of corals by providing mainly a nutritional source of nitrogen and phosphorus. Nevertheless, no study has yet been undertaken on the interactions between feeding and sexual reproduction in corals. This study examines the effects of heterotrophic feeding on the sexual reproduction of Pocillopora verrucosa in aquaria. Rotifers were used as a live food source at two concentrations ((LFC = low feed colonies) = 5 × 10 2 organisms l − 1 ; (HFC = high feed colonies) = 15 × 10 2 organisms l − 1 ) with an unfed control (UC = unfed colonies). Three replicates of five colonies were used for each treatment. Rotifers were distributed among the nine aquaria four times per week for 3 h. Histological sections of coral polyps were prepared to monitor the development of gametogenic stages and the fecundity of the colonies. The number and size of oocytes, sperm sacs and gonad stages were determined in each polyp. Both fed and starved colonies of P. verrucosa proved to be simultaneous hermaphrodites and broadcast spawners. The gametogenesis period was short (3 months) and occurred from October to December 2007. No spawning event was observed in the aquaria. However, the disappearance of mature oocytes in samples collected in January 2008 suggested that spawning took place between December 2007 and January 2008. Heterotrophic feeding appeared to have a negative effect on reproduction in P. verrucosa. The results showed that both the proportion of polyps with gametes and the reproductive effort were lower in the fed than in starved colonies. It is likely that an energetic trade-off occurred between reproduction and other metabolic functions. However, oocytes were bigger in fed corals compared with the unfed controls. Several hypotheses are proposed to explain these metabolic/energy distribution patterns.

Co-variation between autotrophy and heterotrophy in the Mediterranean coral Cladocora caespitosa

This study quantifies the relative contributions of autotrophy and heterotrophy to the energy budget of the temperate scleractinian species Cladocora caespitosa Linnaeus 1767. Colonies were incubated under different light and feeding regimes, and changes in carbon acquisition through photosynthesis and feeding were measured during a 2-month time period. This approach allowed us to quantify the rate at which adjustments to physiology occurred, as well as the magnitude of up- or downregulation of both feeding modes. In addition, we explored how shifts in carbon acquisition mode influenced tissue biomass (protein content), energy stores (lipid content) and colony growth (calcification). Increases in feeding capacity during prolonged exposure to darkness were correlated with decreases in photosynthetic capacity. However, feeding effort did not decrease when photosynthesis was high. In fact, feeding was maximal under high light conditions when food was not available. During starvation, colonies used their lipid stores to partially meet their metabolic requirements. Colonies kept in low light used nutrients from feeding to supplement calcification, whereas those kept at high light converted carbon from feeding into tissue biomass. This work provides the first estimates of rates of adjustment of heterotrophic feeding capacity in a Mediterranean scleractinian coral. For the study species, flexibility in carbon acquisition through heterotrophy was approximately equal to flexibility in photosynthesis both in magnitude and in the rate at which physiological adjustments occurred. The ability to alter feeding effort rapidly and strongly may explain the wide depth distribution of C. caespitosa, and its ability to survive in turbid coastal waters where light is often limited.

Phytoplankton assemblages and characterization of a Dinophysis acuminata population during an upwelling–downwelling cycle

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 58:273-286 (2010) - DOI: https://doi.org/10.3354/ame01372 Phytoplankton assemblages and characterization of a Dinophysis acuminata population during an upwelling–downwelling cycle Sonsoles González-Gil1,3,*,**, Lourdes Velo-Suárez1,**, Patrick Gentien2, Isabel Ramilo1, Beatriz Reguera1 1Instituto Español de Oceanografía, Centro Oceanográfico de Vigo, Aptdo. 1552, 36200 Vigo, Spain 2IFREMER, Centre de Brest, DYNECO, Pointe du Diable BP70, 29280 Plouzané, France 3Present address: Instituto Español de Oceanografía, Orense 58, 7ª planta, 28020 Madrid, Spain *Email: sonsoles.gonzalez@md.ieo.es**These authors contributed equally to this work ABSTRACT: The distributions of Dinophysis acuminata, its potential prey Myrionecta rubra, and the microplankton populations associated with them, were studied in Ría de Pontevedra (NW Spain) during a 2 wk cruise that covered an upwelling–downwelling cycle, and during intensive sampling over 21 h at the end of the cruise. Special attention was focused on the characterization and physiological condition of D. acuminata. There was vertical segregation between a phytoplankton assemblage that was dominated by upwelling-promoted diatoms and another assemblage that was dominated by small dinoflagellates located in the warmer surface layer (0 to 5 m) where D. acuminata was observed. High spatio-temporal variability was observed in the frequency of cells containing starch granules (indicating photosynthetic activity) and digestive vacuoles (indicating heterotrophic feeding); this pattern corresponded with the apparent availability of M. rubra cells. Populations of D. acuminata and M. rubra have their own niches and distinct responses to physical forcing, but both are located in common water masses and occasionally meet. Changes in vacuolation of D. acuminata were followed by a substantial increase (~35%) in cellular volume. D. acuminata did not exhibit daily migratory behaviour, and expressed a high division rate (0.51 d–1) under downwelling conditions. This work sheds new light on the relation between D. acuminata populations and its potential prey, and on its ecophysiology; it also questions previous assumptions about the environment that is suitable for its development. KEY WORDS: Harmful algal blooms · Plankton communities · Dinophysis acuminata · Myrionecta rubra · Predator–prey interactions Full text in pdf format PreviousNextCite this article as: González-Gil S, Velo-Suárez L, Gentien P, Ramilo I, Reguera B (2010) Phytoplankton assemblages and characterization of a Dinophysis acuminata population during an upwelling–downwelling cycle. Aquat Microb Ecol 58:273-286. https://doi.org/10.3354/ame01372 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 58, No. 3. Online publication date: February 11, 2010 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2010 Inter-Research.

Light intensity influences the production and translocation of fatty acids by zooxanthellae in the jellyfish Cassiopea sp.

The influence of light intensity on the fatty acid profiles of the scyphozoan jellyfish Cassiopea sp. and its endosymbiotic zooxanthellae was investigated using a manipulative experiment. The aims of the study were to: 1) identify changes related to light intensity in the fatty acid profiles of the host jellyfish and zooxanthellae; 2) determine if jellyfish exposed to low light intensities compensated for reduced rates of photosynthesis by increasing heterotrophic feeding; and 3) determine if concentrations of zooxanthellae and chlorophyll a (chl a) increased in jellyfish exposed to reduced light intensity. Jellyfish were collected from an artificial urban tidal lake in southeast Queensland, Australia. Two were frozen for immediate analysis and 15 were randomly allocated to each of nine mesocosms. Three replicate mesocosms were then randomly allocated to each of three light treatments: 100%, 25%, and 10% PAR. The mesocosms were supplied with unfiltered, continuous flowing seawater and jellyfish fed on natural zooplankton, supplemented with frozen Mysis shrimp. Three jellyfish were sampled, with replacement, from each mesocosm 3, 15, 22, 39 and 69 days after the experiment commenced. Fatty acids as methyl esters in the host tissue (mesoglea) and zooxanthellae were determined separately using gas chromatography and verified by mass spectrometry. The fatty acid profiles of the host jellyfish and zooxanthellae remained unchanged in the 100% PAR treatment throughout the experiment but varied in the lower light treatments. A decrease in light intensity caused a reduction in the concentrations of some polyunsaturated fatty acids such as 18:1ω9 and 18:4ω3 in the zooxanthellae, the latter being abundant in dinoflagellates. Concomitantly, the concentrations of these fatty acids increased in the host tissues, suggesting a possible transfer of zooxanthellate fatty acids to the jellyfish. Jellyfish in the 10% PAR treatment shrank during the experiment and their fatty acid profiles did not reflect any shift towards increased heterotrophy. On days 22 and 69 concentrations of chl a, zooxanthellae and [chl a] zooxanthella − 1 were determined. [chl a] and [chl a] zooxanthella − 1 , initially increased in the lower light treatments but decreased by the end of the experiment indicating that jellyfish may adapt to reduced light intensity in the short-term but that long-term exposure to reduced light results in compromised performance.

Microarray analysis reveals transcriptional plasticity in the reef building coral Acropora millepora

We investigated variation in transcript abundance in the scleractinian coral, Acropora millepora, within and between populations characteristically exposed to different turbidity regimes and hence different levels of light and suspended particulate matter. We examined phenotypic plasticity by comparing levels of gene expression between source populations and following 10 days of acclimatization to a laboratory environment. Analyses of variance revealed that 0.05% of genes were differentially expressed between source populations, 1.32% following translocation into a common laboratory and 0.07% in the interaction (source population-dependent responses to translocation). Functional analyses identified an over-representation of differentially expressed genes associated with metabolism and fluorescence categories (primarily downregulated), and environmental information processing (primarily upregulated) following translocation to a lower light and turbidity environment. Such metabolic downregulation may indicate nonoxidative stress, hibernation or caloric restriction associated with the changed environmental conditions. Green fluorescent protein-related genes were the most differentially expressed and were exclusively downregulated; however, green fluorescent protein levels remained unchanged following translocation. Photophysiological responses of corals from both locations were characterized by a decline when introduced to the common laboratory environment but remained healthy (F(v)/F(m) > 0.6). Declines in total lipid content following translocation were the greatest for inshore corals, suggesting that turbid water corals have a strong reliance on heterotrophic feeding.