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Acid and alkaline phosphatase activities (E.C.3. 1.3.2 and E.C.3. 1.3.1, respectively) were measured in seawater and sediments from different sites of a salt-pond of the Bay of Cádiz. The profiles of enzymatic activity relative to depth were also analysed. Initially, the optimum conditions (pH, temperature, substrate concentration and amount of sample) for determining enzymatic activities were studied. The apparent activation energies for alkaline phosphatase activity in seawater and sediments were 53.8 and 48.6 kJ mol-1, respectively. The Km and Vmax were 10.6 mM and 89 μg of 4-nitrophenol g-1 h-1 and 8.42 mM and 145 μg of 4-nitrophenol L-1 h-1 for sediments and seawater, respectively. Both types of enzymatic activity reached high values in seawater and sediments; in the confined areas of the salt-pond the values were around 100 μg of 4-nitrophenol L-1 h-1 for seawater and higher for sediments. In general, clear seasonal evolutions for both types of enzymatic activity were found in the seawater, with maxima at the end of summer and minima in winter. No seasonal pattern. was evident in the sediment. Stratification of phosphorus regeneration was observed in the sediment column but there was no stratification at depths greater than 15 cm. [ABSTRACT FROM AUTHOR]

In this work, we compared the proportion of proteins, lipids, carbohydrates and fatty acids in populations of Artemia sp. from the Araya saltworks in northeastern Venezuela, during two stages (nauplii and metanauplii) of their development. The population of Artemia franciscana from San Francisco Bay (USA) was used as reference because of its wide use in aquaculture. The organisms of both populations showed significant differences in protein, lipid, carbohydrate and phospholipid contents between both stages; however, no significant differences were established between both populations. The highest protein concentrations were found in metanauplii: 67% for Araya and 56% for San Francisco. The highest concentrations of lipids (22% and 24%), carbohydrates (17% and 11%) and phospholipids (26% and 35%) were found in nauplii for both populations. Cholesterol esters, cholesterol, triglycerids, and n-3 and n-6 fatty acids were significantly different between stages and between populations. Cholesterol esters, and n-3 and n-6 fatty acids were higher in San Francisco metanauplii, with values of 37%, 11% and 7%, respectively. The highest triglycerid concentration (39%) was found in San Francisco nauplii and the highest cholesterol concentration in Araya metanauplii (50%). The results suggest that the Artemia population from the Araya saltworks contains the necessary elements to cover the nutritional requirements of fish larvae and marine crustaceans under culture. [ABSTRACT FROM AUTHOR]