Ignacio Sánchez-Rodríguez

Element Concentrations in Some Species of Seaweeds from La Paz Bay and La Paz Lagoon, South-Western Baja California, Mexico

La Paz Bay and La Paz Lagoon are water bodies of the Gulf of California that are influenced by waste water discharges from the City of La Paz and from activities of the phosphorite mining company “Rofomex”. Because seaweeds concentrate elements from the water and are used as effective indicators of contamination by metals, we investigated their usefulness in this region. Concentrations of certain major elements (Ca, Fe, K and Na) and trace elements (As, Ba, Co, Cr, Cs, Hf, Rb, Sb, Sc, Se, Sr, Ta, Th, U, Zn and Zr) were determined in 12 species of seaweeds from La Paz Bay and La Paz Lagoon using instrumental neutron activation analysis. The contents of trace elements of environmental importance (As, Co, Cr, Fe, Sb, Se and Zn) in all studied samples are within the range of typical levels for a pristine environment not subjected to anthropogenic impact. Somewhat higher concentrations of Cr (81mg kg−1), Hf (4mg kg−1), Rb (48mg kg−1), Sc (6.3mg kg−1), Ta (0.95mg kg−1), Th (6.8mg kg−1), U (33mg kg−1) and Zn (90mg kg−1) were found in the green seaweed species Ulva (formerly Enteromorpha) intestinalis, whereas such elements as As (77mg kg−1), Sb (1.4mg kg−1) and Se (1.8mg kg−1) were mainly concentrated in the species Sargassum sinicola, Codium cuneatum and Padina mexicana respectively. Because of their higher abundance and heterogeneity in elemental composition the seaweeds species Ulva intestinalis and Caulerpa sertularioides seem to be more suitable for further biomonitoring of heavy metal pollution of the coastal waters in this zone.

Efecto del alga marina Sargassum spp. sobre las variables productivas y la concentración de colesterol en el camarón café, Farfantepenaeus californiensis (Holmes, 1900)

La demanda de alimentos balanceados para camaron en cultivo tiene una tendencia creciente en el mundo, por lo que la busqueda de nuevos ingredientes no convencionales como las algas marinas, para la elaboracion de dichos alimentos cobra importancia, especialmente si estos pueden reducir la concentracion de colesterol en el camaron. El objetivo de este trabajo fue evaluar el efecto de una dieta que contiene 4% de harina de Sargassum spp. sobre los parametros productivos y concentracion de colesterol en el camaron cafe (Farfantepenaeus californiensis). Para ello se realizo un bioensayo con duracion de 45 dias, evaluando dos dietas: una comercial (tratamiento testigo) y otra que incluyo 4% de harina del alga Sargassum. Cuatro acuarios de 60 L fueron usados como replicas para cada tratamiento. Al concluir el bioensayo se seleccionaron muestras de tejido muscular de camarones de los dos tratamientos, se liofilizaron y se les determinaron los lipidos totales, colesterol, trigliceridos y proteinas. No se encontraron diferencias significativas (P>0,05) en cuanto a ganancia de peso, talla, tasa de supervivencia y factor de conversion alimenticia entre los dos tratamientos. La concentracion de colesterol en los camarones alimentados con la dieta que contenia Sargassum fue estadisticamente (P<0,05) menor (77 mg/100 g) que en los alimentados con la dieta testigo (110 mg/100 g). Los resultados obtenidos muestran que 4% de harina Sargassum puede ser incorporada a los alimentos balanceados para camaron cafe, sin causar efectos negativos en sus parametros productivos y reduce la concentracion de colesterol.

The stable isotope of nitrogen in an experimental culture of Ulva spp. and its assimilation in the nutrition of white shrimp Litopenaeus vannamei, Baja California Sur, Mexico

Stable nitrogen isotope ratios have been used to study the incorporation of nitrogen into the food webs of marine systems. Some species of algae can be cocultured with shrimp, resulting in a sustainable alternative to reduce or eliminate the use of commercial food. One option is the development of Ulva spp. in open-air ponds under a rigorous control of water quality. Recently, the coculture of Ulva spp. and juvenile shrimp (in aquaria and open-air ponds) has shown, under stereomicroscope observation, that the crustaceans were feeding on the Ulva spp. The consumption of commercial food and Ulva spp. by juvenile shrimp has been evaluated to establish the uptake of nitrogen into tissues of this crustacean. The muscle tissue of juvenile shrimp initially assimilated nitrogen from commercial feed and later the cocultured shrimp assimilated nitrogen from the Ulva spp., which demonstrated the potential application of live and fresh diets and the optimization of their use in diets containing very low levels or no commercial food.

Intertidal geothermal hot springs as a source of trace elements to the coastal zone: A case study from Bahía Concepción, Gulf of California

We investigated the influence of the intertidal geothermal hot spring (GHS) on the biogeochemistry of trace elements in Santispac Bight, Bahía Concepción (Gulf of California). The geothermal fluids were enriched in As and Hg mainly in ionic form. The suspended particulate matter of the GHS had elevated enrichment factor (EF) >1 of As, Bi, Cd, Co, Cu, Mn, Mo, Sb, Sn, Sr, Ti, U and Zn. The sediment core from GHS1 had high concentration of As, Hg, Corg, S, V, Mo, and U and the extremely high EF of these elements at 8cm of the core. The maximum bioaccumulation of As and Hg was in seaweeds Sargassum sinicola collected near the GHS2. The results confirm the input of trace elements to the coastal zone in Bahía Concepción from geothermal fluids and the evident modification of the chemical composition of the adjacent marine environment.