Biomass Gain Research Articles

Alpine shrub growth follows bimodal seasonal patterns across biomes – unexpected environmental controls

Under climate change, cold-adapted alpine ecosystems are turning into hotspots of warming. However, the complexity of driving forces of growth, associated biomass gain and carbon storage of alpine shrubs is poorly understood. We monitored alpine growth mechanisms of six common shrub species across contrasting biomes, Mediterranean and tundra, using 257 dendrometers, recording stem diameter variability at high temporal resolution. Linking shrub growth to on-site environmental conditions, we modelled intra-annual growth patterns based on distributed lag non-linear models implemented with generalized additive models. We found pronounced bimodal growth patterns across biomes, and counterintuitively, within the cold-adapted biome, moisture, and within the drought-adapted biome, temperature was crucial, with unexpected consequences. In a warmer world, the Mediterranean alpine might experience strong vegetation shifts, biomass gain and greening, while the alpine tundra might see less changes in vegetation patterns, minor modifications of biomass stocks and rather browning.

Efeito de diferentes tamanhos de pellets sobre o crescimento de juvenis de bijupirá (Rachycentron canadum)

ABSTRACT It is known that there is a close relationship between pellet feed size and fish growth. However, the magnitude of this relationship regarding an animals’ feed efficiency is not yet clear. Therefore, the present study conducted at the Virginia Tech - Virginia Seafood Agricultural Research and Extension Center (USA), investigated the effects of three different pellet feed sizes, 1.7mm (EP.1), 2.3 mm (EP.2) and 3.1 mm (EP.3), on the growth of Cobia (Rachycentron canadum) in a recirculating aquaculture system (RAS). Animals were farmed for 55 days in 77.5-liter tanks (6 fish with an initial density of 3.78 g L⁻¹) weighing approximately 41.83±1.24g. The results showed that during the 8-week culture period, there were no significant differences between the animal’s final weight over the different pellet feed sizes (EP.1 - 952.5±40.7g; EP.2 - 1014.5±26.6g; EP.3 - 1030.0±54.8g). However, biomass gain showed significant differences (EP.1 - 704.0±34+.3g; EP.2 - 763.0±27.8g; EP.3 -776.5±51.9g). Consequently, significant differences were also found in the feed conversion factors.

Dietary lipid and protein levels influence the growth and feed utilisation of large yellowtail kingfish (Seriola lalandi) at summer water temperatures

Yellowtail Kingfish (Seriola lalandi; YTK) have a fast growth rate, and as a result, a high energy demand that could be satisfied by dietary lipids. The aim of this experiment was to determine the optimum dietary protein and lipid levels for large YTK maintained during a summer growing season. In this 84-day experiment (2 × 3 factorial design), the growth, feed utilisation and health of YTK (initial weight 2.13 ± 0.02 kg, mean ± SE) fed two nominal lipid levels 25% crude lipid (CL) (20 MJ kg−1 energy) and 30% CL (21 MJ kg−1 energy) and three nominal crude protein (CP) levels (40, 44 and 48%) were investigated. The specific growth rate of fish was significantly affected by the interaction between dietary CP and CL level. The results indicate that fish fed the 25% CL diets grew better than those fed the 30% CL diets. The interaction effect was primarily driven by the significant increase in growth for fish fed diet 1 (40% CP × 25% CL) and diet 2 (44% CP × 25% CL) compared to their respective 30% CL diets, diet 4 (40% CP × 30% CL) and diet 5 (44% CP × 30% CL). The growth of fish fed diet 3 (48% CP × 25% CL) and diet 6 (48% CP× 30% CL) was not significantly different. Feed conversion ratio (FCR) was not significantly influenced by diet however, the fish fed the 25% CL diet series and 40% protein series consumed the most feed. Fish fed the 25% CL series increased their feed intake with decreasing dietary CP level, to potentially compensate for reduced dietary protein. In contrast, fish fed the 30% CL series did not. Crude protein intake was higher when fish were fed the 48% CP diets and was reduced when fed the 40% and 44% CP diets. This response was more pronounced in the 30% CL diet series. There were no negative health effects noted during the study for various analyses including blood biochemistry and haematology, and gastrointestinal tract morphology. Numerically, the highest final weight, biomass gain, SGR, and FCR were consistently observed in the fish fed diet 2, however these were not significantly different to diet 1. Based on the combined results for 2.1–3.5 kg YTK raised during summer, the diet should contain at least 42.9% CP and 25.3% CL (equivalent to diet 2) corresponding to 19.9 MJ kg−1 GE diet with and a CP: GE ratio of 21.6 g MJ−1. In terms of actual protein and energy intake required this corresponds to 5.2 g CP−1 kg BW−1 d−1 (4.5 g DP−1 kg BW−1 d−1) and 242 KJ−1 GE kg BW−1 d−1 (207 KJ−1 DE kg BW−1 d−1) which appears to be optimal. We do not recommend diet lipid levels of approximately 30% over summer periods, as demonstrated in this experiment.

BOOSTING BIOMASS GAIN AND MEAT QUALITY OF RAINBOW TROUT Oncorhynchus mykiss (Walbaum, 1792) - AN APPROACH FOR FOSTERING ROMANIAN AQUACULTURE

Rainbow trout Oncorhynchus mykiss (Walbaum, 1792) is one of the most widely cultured fish species, with a high market value. Although in the Black Sea there is a well-established tradition of cage farming in Turkish waters, in Romania rainbow trout farming has been limited to inland mountain areas. Whereas there is an increasing interest of Romanian economic operators to engage in sea cage farming, this research aimed at testing the adaptation of rainbow trout to the Romanian Black Sea marine environment, determining its growth rate, establishing the optimal size for transfer to saltwater, and increasing meat quality. The research was performed for 7 months, during the cold season, and comprised two batches of O. mykiss individuals transferred to marine water from a mountain trout farm (with initial mean biomasses of approximately 300 g and 180 g, respectively). Upon completion of the experiment, growth parameters showed values much higher compared to freshwater culture, and the biomass gain was remarkable in both batches (reaching final biomasses of approximately 1,700 g and 1,600 g, respectively), the results indicating smaller fish as best fitted for transfer to marine water. The carotenoid-enriched feed provided to the fish resulted in a highly nutritious meat, with the much-appreciated pink colorization

The effect of stocking density on sterlet Acipenser ruthenus (Linnaeus, 1758) larvae in the recirculating aquaculture system

Increasing the number of fish stocked might optimize the efficiency of intensive aquaculture systems however at the same time might have a negative impact on fish welfare and growth parameters. In the current study, three different stocking densities were evaluated in duplicated tanks to investigate the effect of different stocking densities on the survival and growth of sterlet larvae from hatching until the end of weaning, during the 30-day trial. Tested densities were 5, 10, and 20 larvae L−1 in the low (L), medium (M), and high (H) density group, respectively. Freshly hatched larvae (1250, 2500, 5000 larvae per duplicated tanks) were divided into three treatment groups in 250 L raceway larval rearing tanks. The fish biomass gain was significantly higher in each group of higher stocking densities (0.2 ± 0.0 g L−1; 0.4 ± 0.0 g L−1 and 0.8 ± 0.1 g L−1 respectively, r = .990, p < .001). The L group showed a tendency towards better growth during the first 3 weeks, however, at the end of the trial, no significant differences were observed. The highest mortality at the start of exogenous feeding was noticed in group H (12.77% ± 1.3%) and was significantly different from the two lower density groups (5.16% ± 1.3% in L, 7.94% ± 1.3% in M), however, the overall mortality at the end of the trial did not differ among groups. Results on both growth and mortality during the later periods are suggesting the adaptability of sterlet larvae to the more intensive rearing conditions. Thus, it can be stated that the application of a stocking density of 20 larvae L−1 is appropriate in the initial period of larval rearing in the sterlet.

Pearl Millet (Pennisetum glaucum) Seedlings Transplanting as Climate Adaptation Option for Smallholder Farmers in Niger

Pearl millet is the most widely grown cereal crop in the arid and semi-arid regions of Africa, and in Niger in particular. To determine an optimized management strategy for smallholder farmers in southern Niger to cope with crop production failure and improve cropping performance in the context of climate change and variability, multi-site trials were conducted to evaluate the impacts of transplanting on pearl millet growth and productivity. Eight treatments viz. T1-0NPK (100% transplanting without NPK), T1-NPK (100% transplanting + NPK), T2-0NPK (100% transplanting of empty hills without NPK), T2-NPK (100% transplanting of empty hills + NPK), T3-0NPK (50% transplanting of empty hills without NPK), T3-NPK (50% transplanting of empty hills + NPK), T4-0NPK (farmer practice without NPK), and T4-NPK (farmer practice + NPK) were included in the experiment. Compared to farmer practice, transplanting significantly reduced time to tillering, flowering, and maturity stages by 15%, 27%, and 11%, respectively. The results also revealed that T1-NPK significantly increased panicle weight, total biomass, grain yield, and plant height by 40%, 38%, 27%, and 23%, respectively. Farmers’ evaluations of the experiments supported these findings, indicating three substantial advantages of transplanting, including higher yield (37.50% of responses), larger, more vigorous and more panicles (34.17% of responses), and good tillering (28.33% of responses). An economic profitability analysis of the system revealed that biomass gain (XOF 359,387/ha) and grain gain (XOF 324,388/ha) increased by 34% and 22%, respectively, with T1-NPK. Therefore, it can be inferred that transplanting is a promising strategy for adapting millet cultivation to climate change and variability in southern Niger.

Effect of water level and salinity on the growth of Annona glabra L. seedlings

During the last century the mean sea level has been increasing at a rate of 0.2–0.4 mm·year−1, and that rate is expected to accelerate during this century. Coastal wetland ecosystems are sensitive to the potential changes and impacts resulting from a rise in sea level. In the coastal region of the Gulf of Mexico, freshwater swamps are wetlands located further inland than mangroves, and while influenced by the tides, maintain freshwater conditions. Due to their location, the rise in sea level could increase the levels of flooding and salinity in these ecosystems. The objective of this study was to evaluate, under greenhouse conditions, the effect of nine flood and salinity treatments on the survival, growth, and increase in the biomass of Annona glabra (pond apple) seedlings (average height: 18.6 ± 1.61 cm). The treatments combined two factors: water level (Saturation, Flood, Flood-Drought) and salinity (0, 5 and 15‰). Seedling survival was greater under freshwater conditions. Increases in height and diameter, and leaf and biomass gain, were more significant under saturation and freshwater conditions. Based on our results, we conclude increased flood levels and salinity will negatively affect the natural establishment of A. glabra seedlings in freshwater swamps under a scenario of rising sea level.

Impact of mangrove planting on forest biomass carbon and other structural attributes in the Rufiji Delta, Tanzania

Mangrove forests provide important ecosystem services to the human society and nature including mitigation of climate change. The quality and quantity of ecosystem services offered by mangrove forests are however at risk when mangroves are degraded. The restoration of mangrove areas is considered as a natural solution to recover lost ecosystem services such as securing of carbon stocks. This study was set to assess the extent to which mangrove planting activities compensate for the loss of biomass carbon stocks and other structural attributes in Rufiji Delta-Tanzania through analysis of biomass carbon loss and gain as a result of conversion of mangroves forest into rice farms and planting of mangroves respectively. Circular sampling plots were established in good, degraded and restored mangrove areas where total tree heights and Diameter at Breast Height (DBH) of all standing trees were measured and recorded by species and used to compute biomass carbon stock. The mangrove species composition changed from 7 in 1989 to 2 species in degraded plots in 2016. The species dominance changed from Avicennia marina in 1989 to Rhizophora mucronata in 2016 in good mangrove plots and from A. marina and Sonneratia alba to an invasive Baringtonia racemosa in degraded plots. Bruguiera gymnorrhiza was the only mangrove species used for restoration through planting in the delta and the overall survival rate was 37%. The above-ground carbon (AGC) and below-ground carbon (BGC) for the good natural mangrove plots ranged from 28.18 to 299.43 and 16.00–164.51 Mg C ha−1 respectively compared to 0–150.88 and 0–967.01 Mg C ha−1 in the degraded plots. The total biomass carbon stock in the good natural mangrove plots ranged from 44.14 to 463.94 Mg C ha−1 while for the degraded plots the range was 0–247.89 Mg C ha−1. The carbon stocks in 5, 10 and 15 year old planted mangroves were 13.65, 20.13 and 57.53 Mg C ha−1 respectively. The biomass loss of 172.91 Mg C ha−1 was estimated in a period of 25 years (1989–2016), equivalent to an annual loss rate of 6.9 Mg C ha−1year−1, demonstrating that degradation has a significant contribution to loss of carbon stocks. Nevertheless, an average of 3.8 Mg C ha−1year−1 was stocked by 15 years old planted mangroves, demonstrating that there is potential for the planted mangroves to compensate for the lost carbon if the anthropogenic drivers such as rice farming is controlled. These findings call for urgent collective actions among stakeholders to consider and improve the integrated management of the delta.

Production of Nutrient-Enriched Vermicompost from Aquatic Macrophytes Supplemented with Kitchen Waste: Assessment of Nutrient Changes, Phytotoxicity, and Earthworm Biodynamics

Vermicompost is an organic fertilizer rich in nutrients, beneficial microbes, and plant growth hormones that not only enhances the growth of crops but also contributes to the improvement in the physicochemical and biological properties of the soil. However, its lower nutrient content makes it less preferable among farmers and limits its applicability. Here, we investigate, for the first time, nutrient enrichment of vermicompost by supplementing the free-floating macrophyte biomass with cow manure and organic nutrient supplements (eggshell, bone meal, banana peel, and tea waste). Free-floating macrophytes are aquatic plants that are found suspended on the water surface, playing a significant role in the structural and functional aspects of aquatic ecosystems. However, uncontrolled proliferation of these macrophytes endangers these ecosystems, having both economic and ecological implications; therefore, they need to be managed. Results showed an enhanced total nitrogen (2.87%), total phosphorus (0.86%), total potassium (3.74%), and other nutrients in vermicompost amended with cow manure and nutrient supplements. Highest biomass gain (710–782 mg), growth rate (11.83–13.04 mg), and reproduction rate (3.34–3.75 cocoons per worm) was also observed, indicating that amending bulking agent and nutrient supplements not only enhance the nutrient content of the final product but also improve overall earthworm activity. The stability and maturity of vermicompost, as indicated by C/N (&lt;20) and Germination Index (&gt;80), indicates that vermicompost obtained is suitable for agricultural applications. The study concluded that amendment of cow manure and organic nutrient supplements results in producing mature and nutrient-enriched vermicompost suitable for sustainable agricultural production.

Functional plasticity of Capsicum annuum var. glabriusculum through multiple traits

The diversity of functional traits still has not been studied enough in model plant species, even less so in little-known species. This experiment was carried out under the extreme heat of Sonoran Desert, using shading nets and under conditions where the availability of water and nutrients was not a stress factor. We evaluated how the low, intermediate and high sunlight regimes impact survival and promote multiple alterations on phenological and ecophysiological response of cultivated Capsicum annuum var. glabriusculum plants. Extremely warm temperatures promoted a high heat sum in degrees days throughout plants development. Most plants grown in high sunlight regimes did not survive; under intermediate sunlight regimes survival was high and plants developed vegetative and reproductively; but under low sunlight regimes plants survival was high; however, they developed just vegetatively. Photosynthetic response to light suggests that plants are physiologically acclimated to low and intermediate irradiance, whereas the CO2 assimilation curves suggest contrasting photosynthetic capacity traits. Under the intermediate sunlight regimes, plants strengthened their performance through multiple functional traits (e.g. CO2 and water diffusion traits, photosynthetic capacity, respiration, among others). Consequently, their biomass gain was faster and proportionally higher by 76 % with an investment of 14 % in fruits development. The principal components analysis extracted the main explanatory functional traits: photosynthetic nitrogen allocation, stomatal limitation, mesophyll conductance, Rubisco maximum carboxylation velocity, among others. In conclusion, phenological response and multiple functional traits determine plants acclimation to sunlight regimes and extremely warm temperatures in short term.

Fish Oil Replacement by a Blend of Vegetable Oils in Diets for Juvenile Tench (Tinca tinca Linnaeus, 1758): Effects on Growth Performance and Whole-Body Composition.

Simple SummaryFish oil (FO) can be totally replaced by a blend of vegetable oils (30% linseed oil, 20% corn oil, and 50% olive oil) in diets for juvenile tench (Tinca tinca Linnaeus, 1758) without negative effects on survival rate and growth performance. Diets affected the composition of juveniles so that lipid content was significantly lower in animals fed diets without FO. Moreover, the content of linolenic acid (18:3n-3) increased as FO substitution did, being significantly higher with respect to control diet (without vegetable oils) from 40% or higher FO replacement diets. No differences in saturated, monounsaturated, and polyunsaturated fatty acids were found in the fish whole-body. Nutritional indices can be considered within optimal values for healthy foods.Among freshwater species, tench (Tinca tinca Linnaeus, 1758) is considered as a promising species for the diversification of aquaculture, but the intensification of techniques is necessary to promote and consolidate its culture. Adequate feeding in early growth phases is essential to face further grow-out. Fish oil (FO) is the main source of lipids in fish diets, but its production is unsustainable, and thus, alternative oils should be considered. A 90-day experiment was performed to evaluate the effects of partial and total replacement of cod liver oil (FO) by a blend of vegetable oils (VO) in juvenile tench. Six isonitrogenous and isolipidic diets with different levels of a VO blend containing 30% linseed oil, 20% corn oil, and 50% olive oil were tested: 0% (control), 20%VO, 40%VO, 60%VO, 80%VO, and 100%VO. With all diets, survival was 100%, and there were not differences in growth performance (total length (TL); weight (W); specific growth rate (SGR); feed conversion ratio (FCR); and biomass gain (BG)). Compared to the control group, whole-body lipid content decreased significantly in the 100%VO group. No differences in total saturated (SFA), monounsaturated (MUFA), and polyunsaturated (PUFA) fatty acids were found in the whole-body. The content of linolenic acid (ALA) in the whole-body increased as FO substitution did, being significantly higher with respect to control diet from 40% FO replacement diets. Nutritional indices, such as ΣPUFA/ΣSFA and Σn-6/Σn-3 ratios, tended to increase with increasing VO content, whereas the EPA + DHA showed an opposite trend. A total replacement of FO by the blend of VO did not affect the growth performance and fatty acid profile of juvenile tench. Further research on the effects of VO diet on nutritional quality in tench reared to commercial size should be performed.

Enrichment in a Fish Polyculture: Does it Affect Fish Behaviour and Development of Only One Species or Both?

Physical enrichment of structures has been used for the last decades in aquaculture to improve fish production and welfare. Until now, this enrichment has been practiced in fish monoculture but not in fish polyculture. In this study, we developed a polyculture of two freshwater species (pikeperch and sterlet) in recirculated systems (tank of 2.4 m3) with or without physical structures for enrichment. Two types of structures were used: a cover plank on a part of the tank decreasing the light intensity and vertical pipes modifying the water flow. The experiment was conducted in triplicate for a three-month period with juvenile fishes (143 ± 41 g and 27.3 ± 2.2 cm for pikeperch and 133 ± 21 g and 32.8 ± 1.6 cm for sterlet). Behavioural (space occupation and abnormal behaviours) and morphological (total length, final weight, Fulton condition factor, coefficient of variation of the final weight, percentage of biomass gain and specific growth rate) traits were measured. The pikeperch changed their space occupation and showed a preference for low light areas. Sterlet also changed their space occupation: they did not use the cover and occurred mainly in the part of the tank without enrichment. There was no difference for the frequency of abnormal behaviours for pikeperch and sterlet between the two sets (with or without enrichment). There was no statistical difference between the two sets for all the morphological and growth parameters no matter the species and the rearing modality.

ASSESSMENT OF THE TOXIC POTENTIAL OF A MIXTURE OF ASPARTAM AND SORBIC ACID WITH BIOASSAY

The biomarkers of the subchronic toxicity of binary mixtures of food additives sorbic acid and aspartame in concentrations of 50, 100 mg/l and 500, 1000 mg/l, respectively, were studied using plant biotests. A comparative analysis of the indicators such as biomass gain, a level of production of the oxidative stress marker, malondialdehyde (MDA), and dynamics of accumulation of proliferative and cytogenetic disorders was carried out after incubation of Allium cepa roots in the aqueous solutions of these compounds. A significant delay in the root growth (more than 60%) was observed in the combinations of sorbic acid and aspartame of 50/1000 and 100/500 mg/l compared to the control. However, significant differences in the effects on root mass gain were not revealed after analysis of the results of treatment with additives individually and with their mixture. It was found that upon treatment with the mixture of additives, only sorbic acid influenced root mass gain, while the interaction of these compounds was insignificant. An effect of the combined impact of sorbic acid and aspartame on the proliferative activity of meristem cells was more negative than upon treatment in the mono-mode in the similar concentrations. This indicator was affected by both sorbic acid and aspartame; however, the preserving agent again played the leading role. Moreover, the level of proliferation also depended on the effect of the interaction between these additives. The antagonistic effect in regard to the indicator of the oxidative stress was not recorded when treating with the mixture of these additives; although, the MDA level in roots increased more than twice upon individual treatment with sorbic acid, while aspartame, on the contrary, reduced its level by half. The obtained results can be used to monitor and predict early consequences of effects of combinations of sorbic acid and aspartame in the food composition.

Effects of stocking density on productive performance, economic profit and muscle chemical composition of pacu ( Piaractus mesopotamicus H) cultured in floating cages

The present 360-day study aimed to evaluate the productive performance, economic profit and meat quality of pacu cultured in floating cages at different stocking densities. A total of 2880 juvenile pacu, initial weight 50 ± 0.9 g, were reared in eight floating cages of 18.375 m3. Two stoking densities were used: high stocking density (HSD; 26 fish/m3) and low stocking density (LSD; 13 fish/m3). On days 0, 90, 180, 270 and 360, 100 fish per group were used to determine the growth performance, productive indices and total economic profit. The total economic profit was calculated by indices that include the fish price, feed conversion ratio and diet cost, among others. On day 360, the chemical composition and fatty acid profile of the muscle tissues were determined. The LSD group had higher final biomass and weight gain than the HSD group (p = 0.0001 and p < 0.0001 respectively), which was probably associated with the higher protein efficiency ratio obtained in the LSD group (p < 0.05). Additionally, the economic profit from LSD on day 360 was 1.2 times higher than that from HSD (p < 0.0001). More protein and lipid contents were obtained from LSD (p = 0.0035 and p < 0.0001 respectively) while more moisture was obtained from the HSD (p < 0.0001) group. In addition, more eicosapentaenoic (EPA) (p = 0.0013), docosapentaenoic (DPA) (p = 0.0001) and docosahexaenoic (DHA) (p = 0.0003) fatty acids were obtained from LSD. We concluded that when pacu are cultured in floating cages, 13 fish/m3 density produce fish with more weight and better muscle chemical composition, improving the economic profit and the nutritional quality.

Prospects and opportunities for mussel Mytilus trossulus farming in the southern Baltic Sea (the Gulf of Gdańsk)

In the Baltic Sea, where osmotic stress limits the growth of marine organisms, mariculture is driven primarily by the need to improve the status of the environment. To this end, several mussel farms have been attempted in selected areas, except the southern Baltic. The pilot culture of Mytilus trossulus was carried out with the use of a modified long-line system in the Gulf of Gdańsk in 2009–2012, providing the first evaluation of the mussel farming potential in this area. The growth rate of mussels (3.0–6.7 mm year-1) in the gulf was in the low range, but the mean wet biomass gain (1.50 kg m-1 normalized culture rope) was among the highest in the Baltic. After a two-year growth period, one tonne of mussels fixed in their soft tissues from 93 to 98 kg N t-1 and 11 kg P t-1. The cost-benefit analysis revealed a negative budget balance of production for human consumption, with a total income covering only 12.0% of the cumulative costs. Mussel farming in the gulf can therefore only be justified to improve the environmental quality if additional funding mechanisms are put in place to support farming activity.

Warming and Salt Intrusion Affect Microcystin Production in Tropical Bloom-Forming Microcystis.

The Vietnamese Mekong Delta is predicted to be one of the regions most impacted by climate change, causing increased temperature and salinity in inland waters. We hypothesized that the increase in temperature and salinity may impact the microcystin (MC) production of two Microcystis strains isolated in this region from a freshwater pond (strain MBC) and a brackish water pond (strain MTV). The Microcystis strains were grown at low (27 °C), medium (31 °C), high (35 °C) and extremely high (37 °C) temperature in flat photobioreactors (Algaemist). At each temperature, when cultures reached a stable state, sea salt was added to increase salinity to 4‰, 8‰, 12‰ and 16‰. MC concentrations and cell quota were reduced at high and extremely high temperatures. Salinity, in general, had comparable effects on MC concentrations and quota. At a salinity of 4‰ and 8‰, concentrations of MC per mL of culture and MC cell quota (based on chlorophyll, dry-weight and particle counts) were higher than at 0.5‰, while at the highest salinities (12‰ and 16‰) these were strongly reduced. Strain MBC produced five MC variants of which MC-RR and MC-LR were most abundant, followed by MC-YR and relatively low amounts of demethylated variants dmMC-RR and dmMC-LR. In strain MTV, MC-RR was most abundant, with traces of MC-YR and dmMC-RR only in cultures grown at 16‰ salinity. Overall, higher temperature led to lower MC concentrations and cell quota, low salinity seemed to promote MC production and high salinity reduced MC production. Hence, increased temperature and higher salinity could lead to less toxic Microcystis, but since these conditions might favour Microcystis over other competitors, the overall biomass gain could offset a lower toxicity.

Effect of photoperiod on the biomass and survivorship of juvenile scorpions Jaguajir rochae (Scorpiones, Buthidae)

Photoperiod is an important environmental characteristic involved in the regulation of circadian physiological processes in living organisms. This experiment verified the effect of photoperiod on biomass gain and mortality in juvenile scorpions of the species Jaguajir rochae (Borelli, 1910). We maintained the juvenile scorpions under two different photoperiod conditions; group A under a light and dark cycle (LD) 12L:12D (n = 36), and group B (n = 35) was subjected to a total dark cycle 0L:24D. Each juvenile was fed cockroaches twice a week and weighed every 15 days until 120th day. We analyzed the relationship between body mass and time, as well as the mortality between groups. Our results showed that group B had a lower biomass gain than that did group A, and no difference in mortality between the two groups was found. Since the locomotory activity of scorpions is associated with a decrease in luminosity, we suggest that group B had a lower gain in biomass due to a higher locomotor activity, resulting in greater energy expenditure. Though our data showed high mortality across both groups, it was not attributed to the photoperiod but to the high mortality rate of the scorpions of this genus during their initial instars and to them being R-strategist organisms. Thus, this study is important for understanding the relationship between photoperiod and biomass gain in invertebrates, especially in scorpions

Effect of feedings with different protein levels and dietary supplemental rElGH on culture performances of sex reversed Oreochromis niloticus (Linnaeus, 1758)

This study aims to evaluate the culture performance of tilapia (Oreochromis niloticus) that have been treated with 17α-methyltestosterone (MT) and without MT (w-MT), feed with different protein levels (20, 24, and 28%) and recombinant Epinephelus lanceolatus growth hormone (rElGH)-diet. The research was conducted in 9 treatments and triplicate. Tilapia larvae were soaked twice, totaling 500 larvae, at the age of 10 days after hatching (DAH) and the age of 14 DAH was soaked for 4 hours using 1/l MT 2 mg/l solution. Fish maintenance was conducted in an aquarium of 1.0x0.5x0.5 m3 in the first month, and three months later in net cages (2.0x2.0x1.5 m3). Daily growth rate (DGR) and biomass gain (BG) were increased in line with increasing feed protein content and rElGH supplementation. The highest DGR and BG values were MT+28+rElGH (P 0.05) treatment. The highest feed consumption and the lowest feed conversion ratio were also obtained in the MT+28+rElGH treatment (P 0.05). Fish survival was ranged from 79.89 to 90.28% (P 0.05). The highest profit potential was found in the MT+28+rElGH treatment. The efficient aquaculture can be obtained by feeding sex-reversed tilapia at a protein level of 28% and a diet supplemented with rElGH.Keywords:Feed conversion ratioGrowth hormoneProtein retention17α-methyltestosterone

Evolutionary game of life-cycle types in marine benthic invertebrates: Feeding larvae versus nonfeeding larvae versus direct development

Many marine invertebrates have a benthic adult life with planktonic long feeding larval stages (planktotrophy). In other species, planktonic larvae do not eat, and after a rather short period, they settle and initiate their benthic stages (lecithotrophy). Still other species skip planktonic larval stages altogether, and adults produce benthic offspring (direct development). In this paper, we develop an evolutionary game among different life-cycle types and examine the conditions for each life-cycle type to win in a seasonal environment. The growth rate and mortality of benthic individuals are the same among all three life-cycle types, the local habitat (patches) for benthic individuals have a finite longevity, and adults may engage in a limited dispersal just before breeding. Planktotrophy evolves if the planktonic stages are more efficient in terms of biomass gain than benthic life. Otherwise, lecithotrophy or direct development should evolve. Among them, direct development is more advantageous than lecithotrophy if the cost of having planktonic larvae is large, the habitat for benthic individuals is stable, and adults engage in some dispersal.

Brazilian biomes distribution: Past and future

The Last Glacial Maximum (LGM, 26.5–19 ka) was marked by atmospheric cooling, in contrast to the current warming climate, which will probably continue in the coming decades, according to climate models projections. The LGM to pre-industrial transition provides an opportunity to test the vegetation response to a very large temperature change that can then be applied to project pre-industrial to end-of-century changes. In order to explore the changes in Brazilian biomes due to temperature change, we projected potential vegetation for both past and future scenarios. We compared biome projections with a compilation of 149 published LGM reconstructions of climate and vegetation within Brazil and adjacent areas. In addition, we evaluated the particular effects that changes in precipitation, temperature and CO2 had on vegetation by performing sensitivity experiments. Our results suggest that biomes in the western and central portions of the Amazon forest remained largely unchanged during the LGM mainly due to negative temperature anomalies, while a decrease in past precipitation was responsible for the shift from tropical evergreen forest to tropical seasonal forest in the eastern portion of the Amazon. These results are consistent with proxy reconstructions. LGM model projections and proxy reconstructions suggest expansion of grassland in the southern Brazilian highlands. Under future warming scenarios, biome changes are mostly forced by decreasing precipitation and increasing temperatures, which counteract potential biomass gain from the positive CO2 fertilization effect. Under future warming, our simulations show an expansion of Savanna/Cerrado and a reduction of tropical seasonal forest and Caatinga, with potential large impacts over biodiversity and regional climate. • Past precipitation anomalies and vegetation patterns are validated with an updated compilation of 149 reconstructions • LGM simulations show expansion of grassland in agreement with proxy records • Substantially lower CO2 and temperatures are the main controlling factors over vegetational changes during the LGM • +4 °C simulations show expansion of Savanna/Cerrado and a strong dependence of biome shifts on future precipitation changes