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.

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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.]]>

Changes in the distribution, surface canopy, biomass, and standing crop of Sargassum beds (Phaeophyceae) along the southeastern coast of the Baja California Peninsula (Mexico) are described and compared with previous estimates. Also, Sargassum biomass was correlated with latitude. Species were identified and surface canopy, biomass, standing crop, and length structure were estimated for 72 Sargassum beds in 3 localities in 2006. The extent of each bed was determined using GPS. The perimeter of each bed was drawn and its canopy area was calculated. The average biomass was estimated, using quadrats that were randomly distributed over the beds. The highest average biomass was found at Mulegé, with significant differences in the other 2 study areas (Concepción and La Paz bays). The largest bed, surface canopy area, and standing crop were recorded in Concepción Bay. Coverage area, location, and seasonal changes in surface canopy, standing crop, and biomass of Sargassum beds along the southeastern coast of the Baja California Peninsula were compared with the different phenological stages of Sargassum thalli, variations in the available rocky sea floor, and oceanographic characteristics. These aspects must be considered to maintain sustainable exploitation of this potential resource.

The beds of Macrocystis pyrifera (L.) C. Agardh of the west coast of the Baja California peninsula were assessed during the summer of 1986, employing aerial photography with infrared film to determine areas and field samplings in five localities to estimate surface biomass. The total yield was estimated through the statistical analysis for a stratified random sampling. In the northern zone as far as Punta San Antonio, B.C., the distribution of the beds increased slightly compared to spring 1986 (Hernández et al., 1989b). There is a discontinuity from this point to Islas San Benito, where the beds reappear and extend to Punta San Pablo, B.C.S. The area between this last site and Punta San Hipólito, B.C.S., continued without beds of Macrocystis pyrifera. A bed covering of 18,682,018 m2 and a yield of 97,804 ± 6,331 tons were calculated in the summer of 1986. Of this yield, 67.74% was located to the north of the discontinuity of Bahía Vizcaíno, B.C., and 35.23% was located to the South. Seasonal variations of the resource for each study zone and global seasonal variation were analyzed, finding that the most productive seasons are spring and summer.

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