The coastal marine sediments near Santa Rosalía on the eastern coast of the Baja California Peninsula (Mexico) are heavily polluted by metals due to copper mining and smelting over the past century (up to 1984). The present study compares the accumulation of metals in the brown seaweed Padina durvillaei from the central segment of the coast of Santa Rosalía (polluted by Co, Cu, Mn and Zn) and from two segments north and south of the known "hot spot". The seaweed samples were collected in May and August 2004 and June 2005 at 13 stations located along the Santa Rosalía mining region. Heavy metal concentrations were measured by instrumental neutron activation analysis (Co and Fe) directly in dried homogenized subsamples or by flame atomic absorption spectrophotometry (Cd, Cu, Mn, Ni, Pb and Zn) after complete strong acid digestion of sub-samples. The means and standard deviations of the concentrations in dry tissues of Padina durvillaei specimens for all the studied metals and stations lie in the following sequence: Cd (3.6±1.6 mg kg −1 ) < Co (6.5±6.1 mg kg −1 ) < Pb (7.8± 6.2) < Ni (9.96±5.28 mg kg −1 ) < Cu (53±38 mg kg −1 ) < Zn (63±43 mg kg −1 ) < Mn (295±269 mg kg −1 ) < Fe (2243±2325 mg kg −1 ). This increase of the average concentrations was statistically significant. Principal Component Analysis showed that Factor 1 (36.46%) displays high positive loadings for Co, Cu, Mn and Zn, reflecting the influence of local anthropogenic pollution on the seaweed composition, while Factor 2 (26.91%) is important for Co, Fe and Ni and probably corresponds to the adsorption or accumulation of terrigenous elements of the regional origin, while Factor 3, with a high positive loading for Pb and a high negative loading for Cd, is probably controlled by local and regional anthropogenic input of Pb and episodic supply of Cd by local upwellings. The results of ANOVA for each element do not show any significant differences between the average concentrations for Cd, Fe, Ni and Pb in the seaweed of the three segments, or between the central and southern segments for Cu, Mn and Zn. Cobalt contents in the seaweed from the northern and central segments are, however, significantly different from the southern segment. This indicates that element concentrations in Padina durvillaei generally do not follow the drastic increases and gradients of Cu, Co, Mn and Zn contents detected in surface sediments. The apparent contradiction could be explained by a low geochemical mobility of these metals in the polluted sediments, composed mainly of stable residues of smelter wastes, with very low content of organic matter usually driving diagenetic mobilization of some metals into interstitial waters and then to the overlying water.

No abstract

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 (81 mg kg −1 ), Hf (4 mg kg −1 ), Rb (48 mg kg −1 ), Sc (6.3 mg kg −1 ), Ta (0.95 mg kg −1 ), Th (6.8 mg kg −1 ), U (33 mg kg −1 ) and Zn (90 mg kg −1 ) were found in the green seaweed species Ulva (formerly Enteromorpha) intestinalis, whereas such elements as As (77 mg kg −1 ), Sb (1.4 mg kg −1 ) and Se (1.8 mg 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.

The seaweed Sargassum (Sargassaceae) as tropical alternative for goats' feeding. The nutritive value of seaweed (Sargassum spp.) was studied in Baja California Sur, Mexico. Twenty female Nubian goats (43-weeks old) were randomly distributed into two groups of 10 goats each and were housed in individual pens. One group was fed with a control diet and the other with a diet supplemented with 25% of Sargassum spp. Feed and water intake were recorded daily and individually for 60 days. The weight of each goat was recorded every 15 days. The nutritional content of Sargassum spp. was 89% dry mater, 8% crude protein, 31% ash, 2% ether extract, and 39% carbohydrates. Fiber fractions, minerals, vitamins, fatty acids, and antinutritional factors were also determined. There were no significant differences in body weight (8.6 kg control and 9 kg experimental), feed intake (1.3 kg control and 1.6 kg experimental), and feed conversion rate (11.1 control and 12.6 experimental). Water consumption was greater in the goats that ate the Sargassum diet (5.3 l). From these results, Sargassum spp. can be considered as an alternative feedstuff for goats. Rev. Biol. Trop. 54(1): 83-92. Epub 2006 Mar 31.

0,05) en cuanto a ganancia de peso, talla, tasa de supervivencia y factor de conversión alimenticia entre los dos tratamientos. La concentración de colesterol en los camarones alimentados con la dieta que contenía Sargassum fue estadísticamente (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 camarón café, sin causar efectos negativos en sus parámetros productivos y reduce la concentración de colesterol.]]>