Enrique Valenzuela-Espinoza

Protein, carbohydrate, lipid and chlorophyll a content in Isochrysis aff. galbana (clone T-Iso) cultured with a low cost alternative to the f/2 medium

Growth, proximate composition and chlorophyll a content was estimated in static cultures of Isochrysis aff. galbana (clone T-Iso) to compare the quality and quantity of the biomass produced with an agricultural fertilizer medium versus f/2 medium. Culture of microalgae was done with controlled temperature, air flux of 4.5 l min−1, salinity of 33‰ and an irradiance of 110±3 μmol m−2 s−1. Daily samples from the cultures were taken to estimate cellular density, proximate composition and chlorophyll a content during 7 days. Mean cellular density from samples with f/2 medium and with agricultural fertilizer were similar (no significance at P≤0.05), and mean growth rates of 0.62 and 0.61 doubling per day, respectively. Maximum similar values of protein content of 7.3 and 7.6 pg per cell were estimated on the 5th day in f/2 and agricultural fertilizer medium, respectively. Carbohydrate and lipid content decreased during the first 5 days corresponding to the exponential growth in both experiments. Higher content of carbohydrate (no significance at P≤0.05) was found in both media during the first 2 days, after 4 days the carbohydrates reduced three times theirs concentrations. Generally lipid contents in the cultures with agricultural fertilizer were significantly higher (P≤0.05) than f/2 medium. The chlorophyll a content increased exponentially during the culture, and its concentration was similar in both experiments. In conclusion, the cellular density and the biochemical constituents were similar when using either media. This fertilizer can be used in the production of I. galbana (T-Iso) employed in aquaculture.

Biomass production and nutrient uptake by Isochrysis aff. galbana (Clone T-ISO) cultured with a low cost alternative to the f/2 medium

Abstract Biomass production and uptake of nitrate, phosphate and ammonium were determined in batch culture of the marine microalgae Isochrysis aff. galbana (Clone T-ISO) for 7 days comparing an agricultural fertilizer media with the f/2 media. The average cellular density obtained with the f/2 media and the agricultural fertilizer showed no significant difference ( P >0.05) (average growth rate of 0.43 and 0.42 per day, respectively). During the first 4 days, the phosphate in the agricultural fertilizer media was consumed ten times faster than in the f/2 media. When nitrate and ammonium were added together, the ammonium was consumed eight times faster than the nitrate in a period of 5 days. Below concentrations of 1.36 μM of ammonium, nitrate began to be consumed. The nitrate uptake in the f/2 media increased substantially (to 555 μM) from the fourth to the seventh day of culture. The cost of the f/2 media is eight times more expensive than that prepared with agricultural fertilizer. We conclude that agricultural fertilizer did not have a negative effect compared to f/2 on the growth rate of I. aff. galbana (Clone T-ISO), produced the same amount of biomass as the f/2 media, and was much cheaper. The alternate media shows great potential for use in aquaculture for I. aff. galbana (Clone T-ISO) production.

GROWTH, SURVIVAL, AND FEEDING RATES FOR THE GEODUCK PANOPEA GLOBOSA DURING LARVAL DEVELOPMENT

ABSTRACT Developmental larval stages of the geoduck Panopea globosa (Dall, 1898) are described for the first time. Growth rate, survival, and the length—size relationship were also assessed at 22°C in five independently reared cohorts. Clearance rates (CR), ingestion rates (IR), dry weight, and organic weight of select larval stages were quantified in two additional runs. Clearance rates and IR were evaluated as a function of cell concentration (50, 100, 200 and 300 cells/µL) of the chrysophyte Isochrysis sp. (clone T-ISO) using static systems. Conspicuous larval stages appeared after 20 h (trochophore), 24 h (straight hinge or “D”), 5–6 day (early umboned), 9–10 days (intermediate umboned), 11–12 days (late umboned), and 12–14 days (pediveliger). The larval period for P. globosa lasted between 12 days and 14 days, and the shell length recorded at settlement ranged from 332–356 µm (mean, 343 ± 4.2 µm). The overall average gross growth rate of the five larval cohorts was ∼20 µm/day. The relationship between larval shell length (in micrometers) and organic weight (in micrograms) followed a power function with an exponent value of 2.43, whereas the relationship between dry weight and organic weight was linear. Survival rate was approximately 50% in three larval cohorts and 20% in two cohorts. Clearance rates were inversely related to microalgal concentration regardless of larval size, and ranged from 0.3–1.5 µL/h (D larvae) to 15–59 µL/h (pediveliger, 330µm). On the other hand, IR increased with increasing algal concentration, and reached maximum values at 200 cells/µL, except in D-hinge larvae, which exhibited a maximum IR at all concentrations tested. At the highest concentration (300 cells/µL), premetamorphic larvae inhibited their IR. Overall, IR increased from 57–85 cells/h (D-hinge larvae) to 40- or 50-fold when larvae reached the premetamorphic stage. The current study revealed that P. globosa has a short larval period and high survival rate, and withstands a wide range of food concentrations without inhibiting its IR. Therefore, this species appears to be an excellent candidate for hatchery production.