Effect of rotifers fatty acid composition on the occurrence of skeletal deformities in red porgy Pagrus pagrus (Linnaeus, 1758)

Red porgy has been proposed as a candidate for diversification of marine aquaculture production (Hernández-Cruz et al., 1999). However, limited larval survival together with the elevated levels of skeletal deformities occurrence (over 50% of the population), under intensive or semi-intensive systems constitute the major bottlenecks for the production of this species at commercial scale (Roo et al., in press). Essential fatty imbalances on early life stages, may alter the osteological development of reared larvae (Cahu et al., 2003). The objective of this study was to determine the effect of rotifers enrichment, particularly on DHA, on growth, survival and occurrence of skeleton deformities in red porgy.

Use of different commercial Artemia sp. Enrichements in Octopus Vulgaris, paralarval rearing at initial planctonic phase: effects on growth, survival and fatty acid composition of the paralarvae

[EN] Octopus "paralarvae", are planktonic, swim actively and have high metabolic rates, requiring large quantities of live prey of adequate motility and nutritional quality ( Iglesias et al., 2000; Navarro and Villanueva, 2000, 2003). During the planktonic phase, they undergo strong morphological changes, after which the octopuses start settling to the bottom. The potential of Octopus vulgaris as candiadate for diversification of marine aquacultures are mainly due to its high food conversion rate and fast growth.( Iglesias et al 2006). Despite the research effort taken until now, paralarval rearing of O. vulgaris still suffers high mortalities which limited the industrial culture of this species. The main problems in the paralarval rearing stages are the high mortality rates and poor growth. These are attributed to the lack of standardized culture techniques and nutritional deficiencies in the diet of paralarvae, especially in n-3 highly unsaturated fatty acids (n-3 HUFA). The objective if this experience was to test different commercial live prey enrichment to improve nutritional quality of the artemia.

Growth and fatty acid composition of Octopus vulgaris fed different diets based on bogue (Boops boops) in comparison to wild individuals

[EN] Octopus vulgaris is a suitable candidate to diversify marine aquaculture (Iglesias et al., 2000; Vaz Pires et al. 2004). Actually, wild sub-adults are on-growing in floating cages showing promising results (Chapela et al., 2006; Rodríguez et al., 2006). Even though octopus industrial development is still limited, mainly associated to the dependence of wild catch individuals for ongrowing (Iglesias et al., 2007) and a lack of an appropriate formulated diet (García García and Cerezo, 2006). In addition, essential macronutrient requirements for this species are still not well known. Used of discarded bogue as single food for Octopus on-growth results in similar growth than co-fed diets with the crab (Portunus pelagic). FA content of Muscle and DG showed important ARA content, suggesting the important functions of this FA in this specie.

The effects of supplementation of decapod zoea to Artemia basal diet on the digestive gland histology and the fatty acid composition in common octopus (Octopus vulgaris) paralarvae.

[EN]The present study aimed to evaluate the effect of the supplementation of different crab zoeas to enriched Artemia basal diet for O. vulgaris paralarvae during the first month of life. Paralarvae were fed using: enriched Artemia nauplii alone and Artemia co-fed with either first zoea stages of Grapsus adscensionis or Plagusia depressa. The experiment was carried out over a period of 28 days, in 0.12 m3 tanks with a flow-through rearing system. Growth in dry weightas well as mantle length and width were assessed weekly. Additionally, prey and paralarvae fatty acid composition and digestive gland (DG) histology were evaluated.

Fatty acid composition, element concentration and isotope ratios of sea ice algae sampled in Rijpfjorden, Svalbard

The accelerating decrease of Arctic sea ice substantially changes the growth conditions for primary producers, particularly with respect to light. This affects the biochemical composition of sea ice algae, which are an essential high-quality food source for herbivores early in the season. Their high nutritional value is related to their content of polyunsaturated fatty acids (PUFAs), which play an important role for successful maturation, egg production, hatching and nauplii development in grazers. We followed the fatty acid composition of an assemblage of sea ice algae in a high Arctic fjord during spring from the early bloom stage to post bloom. Light conditions proved to be decisive in determining the nutritional quality of sea ice algae, and irradiance was negatively correlated with the relative amount of PUFAs. Algal PUFA content decreased on average by 40 % from April to June, while algal biomass (measured as particulate carbon, C) did not differ. This decrease was even more pronounced when algae were exposed to higher irradiances due to reduced snow cover. The ratio of chlorophyll a (chl a) to C, as well as the level of photoprotective pigments, confirmed a physiological adaptation to higher light levels in algae of poorer nutritional quality. We conclude that high irradiances are detrimental to sea ice algal food quality, and that the biochemical composition of sea ice algae is strongly dependent on growth conditions.

Lipid, carbon and nitrogen content and fatty acid composition of Temora longicornis females and different food species during the experiment

Temora longicornis, a dominant calanoid copepod species in the North Sea, is characterised by low lipid reserves and high biomass turnover rates. To survive and reproduce successfully, this species needs continuous food supply and thus requires a highly flexible digestive system to exploit various food sources. Information on the capacity of digestive enzymes is scarce and therefore the aim of our study was to investigate the enzymatic capability to respond to quickly changing nutritional conditions. We conducted two feeding experiments with female T. longicornis from the southern North Sea off Helgoland. In the first experiment in 2005, we tested how digestive enzyme activities and enzyme patterns as revealed by substrate SDS-PAGE (sodium dodecylsulfate polyacrylamide gel electrophoresis) responded to changes in food composition. Females were incubated for three days fed ad libitum with either the heterotrophic dinoflagellate Oxyrrhis marina or the diatom Thalassiosira weissflogii. At the beginning and at the end of the experiment, copepods were deep-frozen for analyses. The lipolytic enzyme activity did not change over the course of the experiment but the enzyme patterns did, indicating a distinct diet-induced response. In a second experiment in 2008, we therefore focused on the enzyme patterns, testing how fast changes occur and whether feeding on the same algal species leads to similar patterns. In this experiment, we kept the females for 4 days at surplus food while changing the algal food species daily. At day 1, copepods were offered O. marina. On day 2, females received the cryptophycean Rhodomonas baltica followed by T. weissflogii on day 3. On day 4 copepods were again fed with O. marina. Each day, copepods were frozen for analysis by means of substrate SDS-PAGE. This showed that within 24 h new digestive enzymes appeared on the electrophoresis gels while others disappeared with the introduction of a new food species, and that the patterns were similar on day 1 and 4, when females were fed with O. marina. In addition, we monitored the fatty acid compositions of the copepods, and this indicated that specific algal fatty acids were quickly incorporated. With such short time lags between substrate availability and enzyme response, T. longicornis can successfully exploit short-term food sources and is thus well adapted to changes in food availability, as they often occur in its natural environment due seasonal variations in phyto- and microzooplankton distribution.

Occurrence of metazoans, and gut pigments and fatty acid composition of Acartia bifilosa in ice and under-ice water samples from Santala Bay

A field study was conducted in Santala Bay with weekly samplings during February and March 2000. Ice thickness was 20-28 cm, snow cover 0-1 cm. The under-ice water column was stratified with a cold (-0.3 - 0.2°C) and less saline (S = 2.1-4.9) interface layer. Concentrations of particulate organic carbon (0.5-5.8 mg POC/l) and algal pigments (0.3-18.2 µg chlorophyll a/l) were higher in the ice than in the water (0.2-0.5 mg POC/l, 1.6-7.1 µg chlorophyll a/l) and peaked mostly in the bottom part of the ice. The thin ice and almost lacking snow cover had favoured an early ice-algal and phytoplankton bloom. The diversity of metazoans was low, with six species in the ice and eight species in the under-ice water. The rotifer Synchaeta cf. littoralis dominated both in ice and water, with maximum abundances of 230 individuals/l in the bottom part of the ice. Rotifer eggs were also observed in the ice. Baltic sea ice seems to be a suitable habitat for rotifers. Nauplii and copepodids of the calanoid Acartia longiremis in the under-ice water showed some herbivorous feeding (<0.1-0.23 ng gut pigment/individual), but analysis of fatty acids, fatty alcohols and biomarker ratios indicated a more omnivorous/carnivorous diet. Despite low temperatures, this copepod showed growth and development below the ice, doubling in numbers (mainly CI, CII) from 118 to 230 individuals m during the third week of March.

Biometrics, fatty acid composition and stable isotopic ratios of five seabird species from Kongsfjorden, Svalbard

Marine birds are important predators in the marine ecosystem, and dietary studies can give useful information about their feeding ecology, food webs and oceanographic variability. The aim of this study was to increase our understanding of the diet and trophic level of the seabirds breeding in Kongsfjorden, Svalbard. We have used fatty acids and stable isotopes, both of which integrate diet information over space and time, to determine trophic relationships in marine food webs. Fatty acid compositions of muscle from Little auk (Alle alle), Brünnich's guillemot (Uria lomvia), Black-legged kittiwake (Rissa tridactyla), Northern fulmar (Fulmarus glacialis) and Glaucous gull (Larus hyperboreus) were determined and compared with their prey species. Canonical analysis (CA) showed that fatty acid composition differed among the five seabird species. Little auk, Black-legged kittiwake and Northern fulmar had high levels of the Calanus markers 20:1n9 and 22:1, indicating that these seabirds are a part of the Calanus food chain. Brünnich's guillemot differed from the other species with much lower levels of 20:1n9 and 22:1. Brünnich's guillemot is a pursuit diver feeding on fish and amphipods deeper in the water column, below 30 m. Glaucous gull also differed from the other seabird species, with a larger variation in the fatty acid composition indicating a more diverse diet. Trophic level analysis placed Little auk at the lowest trophic level, Brünnich's guillemot and Black-legged kittiwake at intermediate levels and Glaucous gull and Northern fulmar at the highest trophic level.

Fatty acid composition, and bacteria and meiofauna abundance in sediment cores PS71/013 and PS71/085 during POLARSTERN cruise ANT-XXIV/2

During the RV Polarstern ANT XXIV-2 cruise to the Southern Ocean and the Weddell Sea in 2007/2008, sediment samples were taken during and after a phytoplankton bloom at 52°S 0°E. The station, located at 2960 m water depth, was sampled for the first time at the beginning of December 2007 and revisited at the end of January 2008. Fresh phytodetritus originating from the phytoplankton bloom first observed in the water column had reached the sea floor by the time of the second visit. Absolute abundances of bacteria and most major meiofauna taxa did not change between the two sampling dates. In the copepods, the second most abundant meiofauna taxon after the nematodes, the enhanced input of organic material did not lead to an observable increase of reproductive effort. However, significantly higher relative abundances of meiofauna could be observed at the sediment surface after the remains of the phytoplankton bloom reached the sea floor. Vertical shifts in meiofauna distribution between December and January may be related to changing pore-water oxygen concentration, total sediment fatty acid content, and pigment profiles measured during our study. Higher oxygen consumption after the phytoplankton bloom may have resulted from an enhanced respiratory activity of the living benthic component, as neither meiofauna nor bacteria reacted with an increase in individual numbers to the food input from the water column. Based on our results, we infer that low temperatures and ecological strategies are the underlying factors for the delayed response of benthic deep-sea copepods, in terms of egg and larval production, to the modified environmental situation.