Efecto de microorganismos con potencial probiótico en la calidad del agua y el crecimiento de camarón Litopenaeus vannamei (Decapoda: Penaeidae) en cultivo intensivo / Microorganisms effect with probiotic potential in water quality and growth of the shrimp Litopenaeus vannamei (Decapoda: Penaeidae) in intensive culture

The use of probiotics has gained acceptance in aquaculture, particularly in maintaining water quality and enhancing growth in organisms. This study analyzed the effect of the commercial (EM TM, Japan) natural product composed by (Rhodopseudomonas palustris, Lactobacillus plantarum, Lactobacillus casei and Saccharomyces cerevisiae) added to the water, in order to determine its effect in water quality, sediment and growth of L. vannamei under intensive culture. The evaluation included three treatments with a weekly addition of EM: i) tanks without probiotics (C), ii) tanks with a dose of 4L/ha (EM1) and iii) tanks with a dose of 10L/ha (EM2). The treatment C was carried out three times, while treatments EM1 and EM2 were carried out four times. A total of 4 350 shrimps were measured for total length and weight, to calculate total and porcentual weight gain, daily weight gain, specific growth rate (TCE), and food conversion factor (FCA); besides, the survival rate was estimated. The use of probiotics allowed a shorter harvest time in treatments EM1 (90d) and EM2 (105d) with relation to the treatment C (120d). Treatments EM1 and EM2 were within the recommended intervals for culture, with respect to treatment C. The use of probiotic bacteria significantly regulated pH (EM1, 8.03±0.33; EM2, 7.77±0.22; C, 9.08±0.35) and reduced nitrate concentration (EM1, 0.64±0.25mg/L; EM2, 0.39±0.26mg/L; C, 0.71mg/L). Water pH mostly explained the variance with respect to the treatments. Treatment EM2 presented the greatest removal of organic matter (1.77±0.45%), whereas the contents of extractable phosphorus increased significantly in treatment EM1 with 21.6±7.99mg/kg and in treatment EM2 with 21.6±8.45mg/kg with control relation (14.3±5.47). The shrimp growth was influenced by dissolved oxygen, salinity and pH in the sediment, establishing that salinity was the most important variable in the weight with a negative association. Treatment EM1 recorded an improved TCE (2.69±0.35%/d) and FCA (1.46±0.20) with relation to the control treatment (TCE, 1.88±0.25%/d; FCA, 2.13±0.48). Survival was significantly greater in treatments containing probiotics with 61±8.76% and 60±10.5% for EM1 and EM2, respectively. This study indicated the positive effect obtained with the use of this commercial probiotic, to improve culture conditions and growth parameters in an intensive culture of L. vannamei.

Los probióticos han ganado aceptación en la acuicultura para mantener la calidad del agua y aumentar el crecimiento de los organismos. En este estudio se analizó el efecto de una mezcla comercial de microorganismos eficientes (EM) (Rhodopseudomonas palustris, Lactobacillus plantarum, Lactobacillus casei y Saccharomyces cerevisiae) sobre la calidad del agua, sedimento y el crecimiento en un cultivo intensivo de camarón L. vannamei. La evaluación consistió en tres tratamientos: i) estanques sin EM (C), ii) estanques con dosis de 4L/ha (EM1) y iii) estanques con dosis de 10L/ha (EM2). Los resultados demostraron menor tiempo de cosecha en los tratamientos EM1 (90d) y EM2 (105d). Los tratamientos EM1 y EM2 mantuvieron significativamente regulados los valores del pH (EM1, 8.03±0.33; EM2, 7.77±0.22) y redujeron las concentraciones de nitrato (EM1, 0.64±0.25mg/L; EM2, 0.39±0.26mg/L). El tratamiento EM2 presentó la mayor remoción de materia orgánica (1.77±0.45%). El tratamiento EM1 mejoró la TCE (2.69±0.35%/d) y FCA (1.46±0.20). Los tratamientos EM1 y EM2 presentaron mayor supervivencia con 61±8.76% y 60±10.5%, respectivamente. Este estudio demostró el efecto benéfico del uso de la mezcla comercial en los parámetros ambientales y de crecimiento en un cultivo intensivo de L. vannamei.

Impact of logging on a mangrove swamp in south Mexico: cost/benefit analysis

Environmental changes caused by logging in a mangrove swamp were studied in Barra de Tecoanapa, Guerrero, Mexico. Original forest included Rhizophora mangle, Laguncularia racemosa, Avicennia germinans and halophytic vegetation, and produced wood (164.03 m3/ha) and organic matter (3.9 g/m2/day). A total of 3.5 tons of wood per year were harvested from this area. Later, an average of 2,555 kg of maize per planting cycle were obtained (market value of 88 USD). Succession when the area was abandoned included strictly facultative and glycophyte halophytes (16 families, Cyperaceae and Poaceae were the best represented). After logging, temperatures increased 13 degrees C in the soil and 11 degrees C in the air, whereas salinity reached 52 psu in the dry season. These modified soil color and sand content increased from 42.6 to 63.4. Logging was deleterious to species, habitat, biogeochemical and biological cycles, organic matter production, seeds, young plants, genetic exchange conservation of soil and its fertility, coastal protection, and aesthetic value; 3,000 m2 had eroded as the river advanced towards the deforested area (the cost/benefit analysis showed a ratio of 246:1). There was long-term economic loss for the community and only 30 of the site has recovered after five years.