Clearance rate (CR) measurements in Mytilus galloprovincialis were determined over 16 experiments in which the mussels were exposed to diets characterized by variable chlorophyll content (0.28–104.88 µg Chla L–1) in order to: (1) establish the lower trigger level and the saturation reduction, (2) elucidate whether these thresholds were controlled by an on/off switch or by a progressive response, and (3) determine whether the experimental time exerted an effect on the CR measurement under extreme conditions, quantified in terms of chlorophyll content. The results demonstrated that time exerted a significant effect on CR, which varied throughout the experiment in different diets. The CR response differed fundamentally in the significant reduction of CR after prolonged exposure to low and high chlorophyll-content diets compared with the medium ones. Taking into account the data from the sixth hour onwards, a sharp lower trigger level threshold was established at 2.08 µg Chla L–1, showing an on/off CR response. The threshold for saturation reduction was about 26.91 µg Chla L–1 and showed a progressive response to chlorophyll concentration

Field data collected during June 2005 were used to determine the relationship between the second fluorescence maximum (FMax), the top of the oxygen minimum zone (OMZ), and physical processes (coastal currents, eddies, and upwelling) in the northern region of the Eastern Tropical Pacific off Mexico (ETPM). A recurrent second FMax was observed in the ETPM, which was formed only when the upper limit of the OMZ (9.0 µmol L–1) overlapped with the 1% downwelling blue irradiance depth (Ed490). The presence of the second FMax increased the total integrated water column chlorophyll from 20% to 40%. The second FMax was absent from areas where oxygenated California Current Water (CCW) deepened the upper limit of the OMZ below 1% Ed490. The poleward Mexican Coastal Current carried less oxygenated Subtropical Subsurface Water into the area, and enabled the formation of the second FMax. The variability of the second FMax driven by mesoscale physical processes was related to coastal upwelling and cyclonic eddies only in areas not influenced by CCW

A description is given of the purification of B-phycoerythrin (B-PE) from the red microalga Rhodosorus marinus. Initially, phycobiliproteins were released from the microalgal cells by manual cellular fragmentation and sonication. B-PE was extracted with ammonium sulfate precipitation, and purified by anionic and size exclusion chromatography. Its purity was tested using indexes and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Spectroscopic characterization of B-PE was performed by UV-visible spectroscopy, fluorescence spectroscopy, and circular dichroism. Rhodosorus marinus showed three types of phycobiliproteins: phycoerythrin, phycocyanin, and allophycocyanin. The purified B-PE showed a purity ratio(A545/A280) of 4.8, characteristic peaks at 540 and 562 nm with a shoulder at 498 nm, fluorescence emission maximum at 578 nm, and a secondary structure almost stable with pH changes. B-PE was found to be the predominant pigment in R. marinus and this red microalga could be a viable option for the recovery of this chromoprotein.

Species of the family Lutjanidae constitute an important fishery resource in tropical marine areas worldwide and are intensely exploited because of their excellent commercial value and quality. In Colombia, the lane snapper Lutjanus synagris is considered vulnerable to overfishing due to its biological characteristics, habitat deterioration, and historical decrease in catch rates in regions where it used to comprise the highest percentage of the landings. In order to generate more biological information needed to make effective fishery management decisions and policies, the genetic structure of L. synagris was analyzed in three areas of the Colombian Caribbean (Santa Marta, Rosario Islands, and Capurganá) using microsatellite-type molecular markers. Fourteen primers reported for two phylogenetically close species (Rhomboplites aurorubens and Lutjanus campechanus) were analyzed, eight of which were polymorphic and informative for the species under study. All loci were found to depart from Hardy-Weinberg equilibrium due to marked heterozygote deficiency in all the populations studied. Both the analysis of molecular variance (total population FST = 0.006, P = 0.022) and spatial analysis of molecular variance showed a slight statistically significant population structure (best FCT = 0.003, FST = 0.007, P = 0.0001) that separated the Capurganá population from those of the other areas with no evidence of isolation by distance (Mantel test Rxy = 0.023, P = 0.057). The results suggest that the life history of the species and the regional oceanographic conditions play an important role in determining the genetic structure and the existence of two different genetic stocks that should be managed according to their population structure

Extracts from 27 marine algal species (14 Rhodophyta, 5 Phaeophyta, and 8 Chlorophyta) from the Yucatán Peninsula (Mexico) were evaluated for cytotoxic and antiproliferative activity by 3(4,5-dimethylthiazole-2-yl)-2,5 diphenyltetrazolium bromide (MTT) and sulforhodamine B (SRB) assays, respectively. To determine the specificity of cytotoxic activity against tumor cells, the selective index (SI) was also calculated. The following cancer cell lines were employed: normal canine kidney (MDCK) cells, human laryngeal carcinoma (Hep-2) cells, human cervical adenocarcinoma (HeLa) cells, and human nasopharyngeal carcinoma (KB) cells. The results indicated that 44% and 51% of the algal species tested showed cytotoxic and antiproliferative activity, respectively. Most of the cytotoxic extracts were from species of Chlorophyta, with Udotea flabellum and U. conglutinate showing the highest cytotoxic activity against all the cancer cell lines. For Rhodophyta, the Bryothamnion triquetrum extract showed outstanding selective cytotoxicity against Hep-2 cells (CC50 8.29 µg mL–1, SI = 12.04). Two of the five species of Phaeophyta tested (Lobophora variegata and Dictyota caribaea) showed high cytotoxicity activity against the KB cell line. The data show that these species are a potential source of compounds for the treatment of certain cancer diseases

The population structure of the jumbo squid (Dosidicus gigas) is complex, containing several cohorts and three groups defined by their size (small, medium, and large) and by differences in maturation, growth, and life span. Several authors have indicated the possibility of such groups representing discrete genetic units even at level subspecies or species in statu nascendi. Genetic divergence was tested in samples from the Gulf of California (Mexico) and Peruvian Sea by estimation of population divergence statistics, an exact test of homogeneity of allele frequencies, analysis of molecular variance, and genealogical trees applied to data obtained with two molecular markers: RAPDs and mtDNA sequences identified by SSCPs. Neither significant values of ? (FST) nor significant heterogeneity in allele frequencies were detected. Lack of evidence does not imply complete lack of differentiation among the groups but supports the fact that a geographically spread population can have different size groups without relevant genetic differentiation, implying that the hypothetical genetically differentiated groups can occur in different ecological niches.

Eddies and fronts created by geostrophic balance between counter-rotating currents are hydrodynamic processes that concentrate or dilute plankton and suspended material by physical processes of accumulation, retention, or dispersion. Over Campeche Canyon, in the southern Gulf of Mexico, observations revealed an anticyclonic eddy, a cyclonic current off the continental shelf, and an associated thermal front in their common boundary. Along this front there was high Trichodesmium spp. occurrence. Three water masses were found in the upper 120 m layer: Caribbean Tropical Surface Water (CTSW), Caribbean Subtropical Underwater (CSUW), and Gulf Common Water (GCW). The frontal zone between the warm core and cyclonic circulation was observed below the hot summertime mixed layer. The presence of Trichodesmium spp. was associated with the front, indicating its influence on the distribution of this diazotrophic cyanobacterium that enters the Campeche Canyon region via modified CTSW. The associated phytoplankton was dominated by tropical oceanic species of diatoms and dinoflagellates, especially species of Ceratium

Sharks show high biological fragility and, given the intense fishing regimes to which they are exposed in the Gulf of California, it is necessary to establish a conservation and management strategy providing for the protection of their nursery areas. We reviewed the literature concerning shark reproductive biology to determine priority management areas in the Gulf of California by complementarity analysis and different selection criteria. Four levels of management and conservation priority were determined for six quadrants: level 1 corresponded to the area off Mazatlán (Sinaloa) and the area of El Sargento, La Ventana, and Punta Arenas (Baja California Sur); level 2 to the areas of Teacapán (Sinaloa) and Seri (Sonora); level 3 to the areas of San Francisquito-El Barril (Baja California) and Kino Bay (Sonora); and level 4 to the area of La Manga (Sonora). Analysis of space-time variables in a geographic information system indicated that 71% of the commercially important shark species concentrate in coastal zones, mainly in bays, coastal lagoons, estuaries, and wetlands (central and southern Gulf of California) during spring and summer (May–August), except for Prionace glauca, Isurus oxyrinchus, Alopias pelagicus, and Squatina californica that reproduce in winter and spring. The protection of recruitment areas (critical habitats) during peak breeding periods should be an essential part of any resource management plan.