Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

This study provides information on the combined effect of light quality and photon fluence rates (light intensity) on growth efficiency and pigment content of the coastal plankton diatoms Chaetoceros sp., Skeletonema costatum and Thalassiosira pseudonana. The relative growth efficiencies of the three species were significantly higher at 210 µE m-2s-1, under mixed bluegreen light for Chaetoceros sp. and S. costatum, and with white light for T. pseudonana. The chlorophyll a contents of the three species grown under blue-green light, alone or mixed with white light, were significantly higher (P < 0.001) than those with white light and, in all cases, contents were lower at high photon fluence rates, while carotenoids showed inverse trends. The relative growth efficiencies of the three species were significantly different (P < 0.001). There were also changes in the relative pigment concentrations associated with the growth phase, probably due to autoshading.

 During the late-fall, an experiment was performed in the midriff island region of the Gulf of California to study the internal wave effect on primary production and phytoplankton biomass temporal variability. A spot east of the Ángel de la Guarda Island was monitored during 48 hours, and water samples were taken for measuring pH, dissolved oxygen, inorganic nutrients (NO3 and PO4) and chlorophyll a. Photosynthesis-irradiance curves were generated for phytoplankton collected from depths corresponding to 50% and 1% light levels. With spring tides, internal waves altered significantly the water column structure, with a change in the stratification field. Nutrient concentrations at depths > 20 m increased by as much as two-fold, with addition of > 1.0 µM for PO4 and > 7.0 µM for NO3. Chlorophyll a increased by more than 40%, between the surface and the deep chlorophyll maximum, during the same period. The assimilation number, P*m, for the 50%Eo depth decreased to near 20% of its initial value, without an apparent change in this parameter for the phytoplankton collected from the 1%Eo level. Our data support the hypothesis that P*m decreased as a result of vertical advection in the area, transporting photoacclimated phytoplankton from deeper waters toward the surface. The importance of taking these phenomena into consideration when calculating primary production for such dynamic areas using remote sensing data and chlorophyll-light models is discussed.

 Concordance analysis, a multicriteria technique, was used as a decision-making tool. To exemplify the use of this tool, five closure options were evaluated to decrease incidental catch of mahi-mahi or dolphin-fish, Coryphaena spp., by the Mexican eastern Pacific tuna fishery using log-sets. The options consist of combinations of spatial and temporal strata subject to closures, and were evaluated using four eco-biologic and techno-economic criteria. A set of solutions was generated using 286 parametric representations of the weights-vector due to the difficulty of knowing the real preferences of decision-makers. The option with the highest probability of being chosen (almost 0.6) closes three large areas throughout the year for log-sets. This option would reduce mahi-mahi incidental catch in just over 85%, and almost 92% that of other species. However, this option represents the highest cost in terms of lost gross revenues and leaves only eight strata open for the log-set fishery.

The alkali treatment used previous to agar extractions from the Gracilaria genus reduces, among other reactions, the sulphate content and improves the gel strength; however, at an industrial level it requires expensive effluent processing to reduce its polluting charge. The red alga Gracilaria cornea was cultivated under dark and salinity treatments to replace this alkali treatment. The different treatments tested were: (a) darkness and 33‰ salinity for 8 days, [dark treatment]; (b) darkness and 50‰ salinity for 4 days, followed by darkness and 25‰ salinity for 4 days, [4+4]; and (c) darkness and 50‰ salinity for 8 days, followed by darkness and 25‰ salinity for 4 days, [8+4]. The treatment [4+4] increased the agar yield in 26% (from 36.6 to 46.1%). All treatments reduced the sulphate content of the agar in approximately 24% when compared with agar obtained without any treatment. For G. cornea the [4+4] treatment might become in the future an additional treatment to a mild alkali treatment using less alkaline reagents for agar extraction.

The extraction as well as the chemical and physical characterization of the carrageenan of the red algae Chondracanthus pectinatus (Dawson) L. Aguilar and R. Aguilar was performed from field samples collected in three seasons of the year and three reproductive phases. The highest yield of carrageenan was in winter (72%) while the lowest was in summer (66%). Tetrasporic plants showed the lower percentages of 3,6 anhydrogalactose (9%), whereas the maximum was obtained from sterile spring plants (26%). An inverse relationship was observed in the sulfate content. The infrared spectrum showed that the carrageenan of C. pectinatus belongs to the hybrid kappa-iota (κ-ι) in carposporic and sterile samples but to lambda type (λ) in tetrasporic ones.

 A simple recursive algorithm for the estimation of the friction velocity as a function of the air-sea temperature difference and the wind speed measured at 10-m height above the sea surface, without needing of drag coefficient, is presented. Numerical results are discussed in terms of atmospheric stability and compared to historical records of sea surface microwave backscattering. The friction velocity behavior, as a function of the temperature difference, with constant wind velocity, is found to be similar to that of the sea-surface microwave backscattering. This information implies a functional relationship between the surface wind stress and the sea-surface microwave backscattering.

The calcareous reef building Polychaeta Ficopomatus enigmaticus is considered an invader species in Argentina. First mentioned in 1943, it has shown an important expansion up to date. At present, living parts of reefs are the most important refuge to grapsid crab Cyrtograpsus angulatus juveniles in Mar Chiquita, a brackish coastal lagoon in Buenos Aires Province, Argentina. This work assessed the reef|00E2|??s role in C. angulatus recruitment, by estimating the total volume of living reef and the number and biomass of recruits and juveniles that can inhabit it. Total volume of living reef estimated in 1999 was 353,849 m3, 50% more than the estimate made in 1975. The maximum number of juvenile crabs that reefs can host yearly was estimated from the juvenile density in reefs, the number of massive recruitment peaks and the total volume of living reef, in 1.68 |00C3|? 1010, or 1,946 t, expressed as biomass. It is shown that the presence of F. enigmaticus has a high impact on the populational biology of C. angulatus by increasing refuge availability and recruitment success. This impact is extended to the whole community being this crab a key species in the Mar Chiquita Lagoon.

 The yield of the Pacific sardine Sardinops sagax caeruleus from Bahía Magdalena, B.C.S., was analyzed using a stockrecruitment model. The model was stochastic, and it used the hypotheses of process error (H1) in the model, and observation error (H2) in the data. The results showed a positive bias in the management quantities and the parameters of the model. Confronting both hypotheses with a Monte Carlo simulation resulted in evidences of the effect of the observation error in the measurement of the adult stock of the sardine population. Statistical analysis supported in the Bayes theorem showed that the probabilities estimated from a maximum likelihood model for hypothesis H1 are informative enough as prior probability. In this way, the maximun sustainable yield (MSY) of the fishery was 14,400 t with uMSY = 0.35. The decision table showed that parameters of the model have a probability > 0.80 for α (density-independent parameter) between 0.040 and 0.058, while β (density-dependent parameter) varies between 1.6 and 2.2 with a probability > 0.85. The joint distribution of both parameters allowed a yield 10,100 t < MSY < 20,200 t per fishing season.

 P. sterna oocytes cannot be fertilized in vitro unless they are obtained by inducing spawning. The present work was undertaken to develop a simple method to induce germinal vesicle breakdown that would enable the oocytes to be fertilized without prior spawning. We found that Pteria sterna oocytes removed from the ovaries are induced to undergo germinal vesicle breakdown (GVBD) by 10 mM NH4Cl in seawater, and proceed to metaphase I of meiosis, at which stage they can be fertilized and will develop at least as far as "D" larvae. On the other hand, ovarian oocytes exposed to 2 × 10–5 M serotonin in seawater remained in prophase and did not undergo GVBD. Ammonium chloride treatment provides a simple, inexpensive procedure that can be useful in studies of fertilization and development, and for attempts to repopulate this exploited species.

In most birds egg volume has been recorded directly dependant on clutch sequence. Furthermore, the egg size has been also considered as dependent on the size of its predecessor, thus, they are constantly analyzed with non-parametric statistics, given the independency required by the parametric one. We studied the Heermann's gull (Larus heermanni) colony at El Callo Islet (south of San José Island, B.C.S.) during its reproductive season (1996). Twenty-seven nests were followed and identified with plastic flags. The eggs were marked (according to their appearance) and measured (length and width), in order to calculate their volume. The analysis of the volume of 66 eggs showed normality and homocedasticity (in all cases α = 0.05). The volume comparison by clutch sequence evidenced that the first and second eggs were similar, but both differed from third eggs ( x- ± SE: 57.59 ± 1.52, 56.62 ± 1.75 and 52.66 ± 2.48 cm3, respectively). Furthermore, three simple linear correlations were performed (first-second, first-third and second-third), in order to evidenciate the supposed size-dependence on previous eggs. No relationship could be established in either comparisons (r = 0.143, 0.08 and 0.291; d.f.= 23, 14 and 14, P = 0.502, 0.784 and 0.313, respectively). This means that the egg volume depends on the clutch sequence, but not necessarily on the volume of previous eggs, indicating the need of testing such dependency and, consequently, the type of statistical analysis to be used.