Digestive enzymes in juvenile green abalone,Haliotis fulgens,fed natural food

Enzymes responsible for the digestion of food protein by juvenile green abalone (Haliotis fulgens) were studied when fed algae or a sea grass (Phyllospadix torreyi) naturally occurring in the habitat. The effect of food on the composition and activity of the enzymes was also evaluated. Acid, serine proteinases and aminopeptidases, as confirmed by pH profile of activity, specific inhibition and synthetic substrate hydrolysis were found in the digestive organs of juvenile green abalone. Algae and sea grass differentially affected the digestive system in abalone.     

Effect of nutrient availability on understory algae during El Ni?o Southern Oscillation (ENSO) conditions in Central Pacific Baja California

An experimental study of the effect of artificial nutrient supply on understory algae was made during 1997 El Ni?o Southern Oscillation (ENSO) at the Mexican Pacific coast of Baja California. Twelve quadrats of 1 m² were placed on the sea bed. Six quadrats were used as controls, and six were treatments with added artificial nutrients. Nutrients were supplied using polyvinyl chloride (PVC) pipes filled with slow-release inorganic fertilizer. The algae species composition and cover in each quadrat were estimated using the random point quadrat method. The percent of cover was tested using a multifactorial analysis of variance, and significant differences were obtained by post hoc Tukey’s HSD test. The analysis was carried out annually, seasonally, and seasonal and monthly for each species. The seawater temperature was recorded, and compared with historical data. The bottom and surface seawater nitrate concentration were measured. Twenty-five species of macroalgae and one seagrass were identified. The most abundant species was Corallina vancouveriensis (−N = 19.8% and +N = 26.6% average cover). The other species had lower than 10% cover. Significant differences of species percent cover between experimental groups (+N and −N) were detected in the annual analysis (p = 0.059). Seasonal analysis did not showed significant differences for any season. Monthly analysis showed significant differences in average percent cover when nutrients were added in eight species in different months: Bossiella orbigniana (August); Colpomenia sinuosa (June); Corallina officinalis (August); C. vancouveriensis (June); Dictyota flabellata (September); Eisenia arborea (June); Gracilaria marcialana (June); Macrocystis pyrifera (October), and the seagrass Phyllospadix torreyi (September and December). In conclusion, not all seaweed species are sensitive to nutrient addition during the ENSO years. In this research, we found eight species and one seagrass that had a positive reaction to the nutrients during the most severe stage (summer) of the ENSO.     

Efficiency of copper removal by Sargassum sinicola in batch and continuous systems

The efficiency of batch and continuous systems of copper removal by Sargassum sinicola was studied. The effects of flow rate, initial metal concentration, and bed density on the capacity of the continuous system were also recorded. In batch systems, the maximum biosorption capacity was calculated as 49.63?±?0.88 mg g^?1; in the continuous system, under the following conditions: flow rate of 10 mL min^?1, initial solution of 200 mg Cu L^?1, bed density of 150 g L^?1, and higher copper removal of 62.39?±?1.91 mg g^?1 was achieved. The Thomas model can be used to predict the breakthrough curves, but it underestimated breakthrough time.     

Affinities of the marine flora of the Revillagigedo Islands,Mexico

The benthic algal flora reported for the Revillagigedo Islands comprises 205 specific infraspecific taxa: 42 Chlorophyta, 29 Phaeophyta and 134 Rhodophyta. This insular flora shares 131 taxa (54%) with other regions of the Mexican Pacific and 74 (36%) are restricted apparently to the islands. One hundred three taxa (50%) are shared with areas of the Mexican tropical Pacific, 69 (34%) with warm temperate Pacific Mexico and 66 (32%) with La Paz, the transitional zone between tropical and warm temperate Pacific Mexico. Considering more general regions, the Revillagigedo Islands flora includes apparently restricted distribution (34 spp., 16.6%), exclusively tropical (51 spp., 25%) and widely distributed eastern Pacific (33 spp., 16%) taxa. Even though we consider that the inventory of the Revillagigedo Islands and to a lesser degree the eastern tropical Pacific flora is still incomplete and in need of further taxonomic study, the floristic comparison shows a greater affinity of the Revillagigedo Islands flora with the Mexican tropical Pacific than with any other part of Mexico.     

Concentrations of trace elements in sea urchins and macroalgae commonly present in <Emphasis Type="Italic">Sargassum</Emphasis> beds: implications for trophic transfer

The aim of the study was to evaluate the dynamic of cadmium, lead, copper, zinc, and iron among lower trophic levels, sea urchins and macroalgae. Diets and isotopic values were used in combination to explore trophic positions and potential transference of metals from primary producers to consumers. Concentrations of trace elements were measured in two species of sea urchin (Tripneustes depressus and Eucidaris thouarsii) and nine macroalgae that are usually used as food in four Sargassum beds, one of which is close to a phosphorite mine. Specimens were collected when Sargassum fronds were at their greatest (winter) and lowest (summer) abundance. Highest concentrations of Cd, and Cu in both urchin species were recorded in winter at the site near the phosphorite mine. Concentrations of Pb in T. depressus were below the detectable limit, whereas E. thouarsii, which in addition to a high concentration of Pb, had high amounts of Cu and Zn. Gut content analysis, indicates that the diet of both sea urchins at the four sites and two collection dates is mainly macroalgae. The δ ¹⁵N isotopic values in sea urchins in a typical Sargassum bed were in good agreement with a diet dominated by macroalgae, with T. depressus having herbivorous habits and E. thouarsii having omnivorous habits in this environment. We found macroalgae important in the dynamics of metals in food webs, potentially contributing to transferring Cd, Cu, and Zn to key invertebrate species, such as sea urchins, indicating connectivity of food webs and ecological structuring of marine environments.