Exogenous enzyme complex prevents intestinal soybean meal-induced enteritis in Mugil liza (Valenciennes, 1836) juvenile

ABSTRACT Four soybean meal-based diets containing increasing levels of an enzyme complex (E50, E100, E150 and E200 at 50, 100, 150 and 200 g ton-1, respectively) and one soybean meal-based diet without the enzyme complex (E0) were fed in triplicate to M. liza juveniles in a semi-static flow system with 20 fish per tank for 75 days. There were no differences between the treatments for animal performance parameters, but fish fed the enzyme complex treatment exhibited significantly (P<0.05) higher values of calcium bone retention compared with control fish. Although there was no relationship between bacterial counts in different sections of the gastrointestinal tract or enzyme levels, filamentous bacteria were increased in E50 compared with E150. All of the treatments resulted in higher bacterial counts in the stomach than in intestinal segments. Histological screening showed serious to moderate infiltration of inflammatory cells, modification in villus morphology and necrosis in some cases in fish fed the E0 diet. In addition, fish from the E0 treatment exhibited significantly (P<0.05) lower lipid deposition in the peritoneal cavity. Therefore, the use of low levels of exogenous enzyme is recommended in diets for M. liza when soybean meal is used as the main source of protein.

Exogenous enzyme complex prevents intestinal soybean meal-induced enteritis in Mugil liza (Valenciennes, 1836) juvenile.

Four soybean meal-based diets containing increasing levels of an enzyme complex (E50, E100, E150 and E200 at 50, 100, 150 and 200 g ton-1, respectively) and one soybean meal-based diet without the enzyme complex (E0) were fed in triplicate to M. liza juveniles in a semi-static flow system with 20 fish per tank for 75 days. There were no differences between the treatments for animal performance parameters, but fish fed the enzyme complex treatment exhibited significantly (P<0.05) higher values of calcium bone retention compared with control fish. Although there was no relationship between bacterial counts in different sections of the gastrointestinal tract or enzyme levels, filamentous bacteria were increased in E50 compared with E150. All of the treatments resulted in higher bacterial counts in the stomach than in intestinal segments. Histological screening showed serious to moderate infiltration of inflammatory cells, modification in villus morphology and necrosis in some cases in fish fed the E0 diet. In addition, fish from the E0 treatment exhibited significantly (P<0.05) lower lipid deposition in the peritoneal cavity. Therefore, the use of low levels of exogenous enzyme is recommended in diets for M. liza when soybean meal is used as the main source of protein.

Human activities and climate variability drive fast-paced change across the world's estuarine-coastal ecosystems.

Time series of environmental measurements are essential for detecting, measuring and understanding changes in the Earth system and its biological communities. Observational series have accumulated over the past 2-5 decades from measurements across the world's estuaries, bays, lagoons, inland seas and shelf waters influenced by runoff. We synthesize information contained in these time series to develop a global view of changes occurring in marine systems influenced by connectivity to land. Our review is organized around four themes: (i) human activities as drivers of change; (ii) variability of the climate system as a driver of change; (iii) successes, disappointments and challenges of managing change at the sea-land interface; and (iv) discoveries made from observations over time. Multidecadal time series reveal that many of the world's estuarine-coastal ecosystems are in a continuing state of change, and the pace of change is faster than we could have imagined a decade ago. Some have been transformed into novel ecosystems with habitats, biogeochemistry and biological communities outside the natural range of variability. Change takes many forms including linear and nonlinear trends, abrupt state changes and oscillations. The challenge of managing change is daunting in the coastal zone where diverse human pressures are concentrated and intersect with different responses to climate variability over land and over ocean basins. The pace of change in estuarine-coastal ecosystems will likely accelerate as the human population and economies continue to grow and as global climate change accelerates. Wise stewardship of the resources upon which we depend is critically dependent upon a continuing flow of information from observations to measure, understand and anticipate future changes along the world's coastlines.

A vigorous specialized microbial food web in the suboxic waters of a shallow subtropical coastal lagoon.

To examine the extent of the microbial food web in suboxic waters of a shallow subtropical coastal lagoon, the density and biomass of bacteria and protozooplankton were quantified under different dissolved oxygen (DO) levels. In addition, bottom waters of a stratified site were compared with bottom waters of a homogeneous site under periods of high and low biological oxygen production/consumption in the lagoon. At the stratified site, microbial biomass decreased with oxygen decline, from oxia to suboxia, with a recovery of the initial total biomass after a 20-day period of persistent suboxia. A peak in density and biomass of purple sulfur bacteria (PSB) (90 µg C L(-1)) occurred in the suboxic waters 20 days prior to the peak in biomass of ciliates >50 µm (Loxophyllum sp. of 150 µm) (160 µg C L(-1)), demonstrating a top down biomass control. Ciliates >50 µm were positively correlated with PSB and bacteriochlorophyll a (photosynthetic pigment of PSB). Total protozoan biomass reached 430 µg C L(-1) in the suboxic waters of the stratified site, with ciliates >50 µm accounting for 90% of the total ciliate biomass and of 55 % of biomass of protozoa. At the homogeneous site, total protozoan biomass was only 66 µg C L(-1), where flagellates and ciliates <25 µm were the dominant microorganisms. Therefore, as light is available for primary producers in the bottom waters of shallow stratified coastal lagoons or estuaries, one can expect that high primary production of PSB may favor a specialized microbial food web composed by larger microorganisms, accessible to zooplankton that tolerate low DO levels.

Primary production in a subtropical stratified coastal lagoon--contribution of anoxygenic phototrophic bacteria.

Anaerobic anoxygenic phototrophic bacteria can be found in the suboxic waters of shallow stratified coastal systems, and may play important roles in the total primary production of subtropical stratified coastal lagoons. We investigated the spatiotemporal variability of light CO(2) fixation and net oxygen production in the stratified Conceição Lagoon (Brazil) in summer and fall of 2007, as well as the contribution of bacteriochlorophyll a (BChl a)-containing bacteria to photosynthetically driven electron transfer. Both chlorophyll a (Chl a) and BChl a varied in space, while only BChl a varied in time (three-fold increase from summer to fall). In summer, net oxygen production and light CO(2) fixation were correlated, with both having higher rates with higher Chl a concentrations in the enclosed region of the lagoon. In fall, CO(2) fixation was decoupled from oxygen production. Denaturing gradient gel electrophoresis revealed that bacterial communities of oxic site 12 and suboxic site 33 formed one cluster, different from other oxic samples within the lagoon. In addition, BChl a/Chl a ratios at these sites were high, 40% and 45%, respectively. Light acted as the main factor controlling the BChl a concentration and CO(2) fixation rates. High turbidity within the enclosed area of the lagoon explained high BChl a and decoupling between CO(2) fixation and oxygen production in oxygenated waters. Contribution of purple sulfur bacteria to total bacterial density in suboxic waters was 1.2%, and their biomass contributed to a much higher percentage (12.2%) due to their large biovolume. Our results indicate a significant contribution of anaerobic anoxygenic bacteria to the primary production of the "dead zone" of Conceição Lagoon.

Spatiotemporal variation of bacterial assemblages in a shallow subtropical coastal lagoon in Southern Brazil.

A study on the bacterioplankton of Conceição Lagoon (27 degrees 34' S-48 degrees 27' W), Southern Brazil, was carried out in July 2005 (austral winter) and January 2006 (austral summer) to characterize the bacterial spatiotemporal distribution and to determine the heterotrophic and photoautotrophic bacterial dominance in hypoxic/oxic stratified waters. Bacterial abundance increased significantly (p < 0.05) in summer with averages of coccus cyanobacteria (CCY) ranging from 1.02 x 10(5) (winter) to 3.21 x 10(6) cells mL(-1) (summer), heterotrophic coccus/rod-shaped (HCR) cells from 7.00 x 10(4) to 3.60 x 10(6) cells mL(-1), and heterotrophic filamentous (HF) bacteria from 2.90 x 10(3) to 2.74 x 10(5) cells mL(-1). Bacterial biovolumes also increased in summer with mean biovolumes of CCY ranging from 0.38 to 1.37 microm3, HCR cells from 0.31 to 1.12 microm3, and HF from 3.32 to 11.34 microm3. Principal component analysis showed that salinity, temperature, and light were the abiotic factors that better explained the temporal variability of bacterial assemblages. Bacterial heterotrophy dominated in the lagoon, excepted by the southern and part of central sector in January 2006, when autotrophic-dominated microbial community occurred. Spatially, bacterial assemblages were influenced by nutrient gradient, oxygen, and salinity with a positive relationship between biovolumes and nutrients and a negative relationship between abundance of coccus cyanobacteria and nutrients. The stratified [corrected] area revealed a singular temporal pattern with hypoxic bottom waters in winter and oxygen-rich waters appearing in summer related with the availability of light and predominant microbes. Thus, oxygen consumption/production is likely to be regulated by the amount of light reaching the bottom, stimulating the production of oxygen by oxygenic phototrophs.

Biomass distribution of heterotrophic and autotrophic microorganisms of the photic layer in Cuban southern oceanic waters

We measured the vertical and seasonal distribution of picoplankton (0.2-2 µm) and nanoplankton (2-20 µm) in the photic layer of Cuban southern oceanic and coastal waters. The concentration of the different fractions was estimated by epifluorescence microscopy. Heterotrophic components from the different fractions showed higher vertical stratification in the oceanic station in comparison to the coastal one. The autotrophic components showed an irregular vertical distribution pattern, both in coastal and oceanic stations. In all the analyzed stations, the heterotrophic bacteria showed an inverse correlation with the autotrophic (r= -0.98), and the heterotrophic nanoplankton (r= -0.96). Auto and heterotrophic nanoplankton probably regulate bacteria abundance by predation, although autotrophic nanoplankton may represent a source of organic matter for microorganisms. Rev. Biol. Trop. 55 (2): 449-457. Epub 2007 June, 29.

Determinamos la distribución vertical y estacional del picoplancton (0.2-2 µm) y el nanoplancton (2-20 µm) en la capa fótica de las aguas oceánicas y costeras al sur de Cuba. La concentración de las diferentes fracciones fue estimada mediante microscopía de epifluorescencia. Los componentes heterotróficos de las diferentes fracciones mostraron una elevada estratificación vertical en la estación oceánica en comparación con la estación costera. Por otro lado, los componentes autotróficos presentaron un patrón de distribución vertical irregular tanto en la estación costera como en la oceánica. En los análisis realizados las bacterias heterótrofas mostraron una correlación inversa con el nanoplancton autótrofo (r= -0.98), y con el nanoplancton heterótrofo (r= -0.96). Estos resultados sugieren que el nanoplancton (autótrofo y heterótrofo) probablemente regula la abundancia de bacterias mediante la depredación, además que el nanoplancton autótrofo pudiera representar una fuente de materia orgánica para los microorganismos.

Biomass distribution of heterotrophic and autotrophic microorganisms of the photic layer in Cuban southern oceanic waters.

We measured the vertical and seasonal distribution of picoplankton (0.2-2 microm) and nanoplankton (2-20 microm) in the photic layer of Cuban southern oceanic and coastal waters. The concentration of the different fractions was estimated by epifluorescence microscopy. Heterotrophic components from the different fractions showed higher vertical stratification in the oceanic station in comparison to the coastal one. The autotrophic components showed an irregular vertical distribution pattern, both in coastal and oceanic stations. In all the analyzed stations, the heterotrophic bacteria showed an inverse correlation with the autotrophic (r= -0.98), and the heterotrophic nanoplankton (r= -0.96). Auto and heterotrophic nanoplankton probably regulate bacteria abundance by predation, although autotrophic nanoplankton may represent a source of organic matter for microorganisms.

Antioxidant properties of the mucus secreted by Laeonereis acuta (Polychaeta, Nereididae): a defense against environmental pro-oxidants?

Polychaeta species like Laeonereis acuta (Nereididae) usually secrete great amounts of mucus that wrap the animal inside. Taking into account that fungi action in the sediment and UV radiation acting on dissolved organic matter in the water produces reactive oxygen species (ROS) like hydrogen peroxide (H(2)O(2)), it was considered that the mucus secretion could represent an antioxidant defense against environmental ROS. Antioxidant enzymes (catalase-CAT; superoxide dismutase-SOD; glutathione peroxidase-GPx and glutathione-S-transferase-GST) and total antioxidant capacity (TOSC) were determined in worms and mucus secretion. Higher (p<0.05) CAT, GPx and TOSC values were registered in mucus samples respect worms, SOD activity was similar (p>0.05) in both kind of samples, and absence of GST activity was observed in mucus samples, suggesting absence of catalyzed phase II reactions. In assays conducted with hepatoma cell lines exposed to H(2)O(2), it was verified that: (1) mucus co-exposure significantly (p<0.05) lowered DNA damage induced by H(2)O(2); (2) ROS production was significantly (p<0.05) reduced when cells were exposed simultaneously with mucus samples and H(2)O(2) respect H(2)O(2) alone. It can be concluded that the mucus production contributes substantially to the antioxidant defense system of the worm against environmental ROS through the interception or degradation of H(2)O(2), peroxyl and hydroxyl radicals.

Antioxidant mechanisms of the Nereidid Laeonereis acuta (Anelida: Polychaeta) to cope with environmental hydrogen peroxide.

Hydrogen peroxide (H(2)O(2)) is a naturally occurring prooxidant molecule, and its effects in the macroinvertebrate infauna were previously observed. The existence of a gradient of antioxidant enzymes activity (catalase [CAT], glutathione peroxidase [GPx], superoxide dismutase [SOD], and glutathione-S-transferase [GST]) and/or oxidative damage along the body of the estuarine polychaeta Laeonereis acuta (Polychaeta, Nereididae) was analyzed after exposure to H(2)O(2). Because this species secretes conspicuous amounts of mucus, its capability in degrading H(2)O(2) was studied. The results suggest that L. acuta deal with the generation of oxidative stress with different strategies along the body. In the posterior region, higher CAT and SOD activities ensure the degradation of inductors of lipid peroxidation such as H(2)O(2) and superoxide anion (O(2)(.-)). The higher GST activity in anterior region aids to conjugate lipid peroxides products. In the middle region, the lack of high CAT, SOD, or GST activities correlates with the higher lipid hydroperoxide levels found after H(2)O(2) exposure. Ten days of exposure to H(2)O(2) also induced oxidative stress (lipid peroxidation and DNA damage) in the whole animal paralleled by a lack of CAT induction. The mucus production contributes substantially to H(2)O(2) degradation, suggesting that bacteria that grow in this secretion provide this capability.