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Concentrations of Co, Cu, Fe, Mn, Ni, Pb and Zn in four macroalgae species ( Ulva lactuca , Chondracanthus squarrulosus , Sargassum sinicola and Gracilariopsis lemaneiformis ) were obtained for the first time from the central part of the west coast of the Gulf of California. Generally, no differences in metal concentrations were found among the different seaweed species, although spatial differences were apparent. Iron, Mn and Cu exhibited higher concentrations at the stations located in front of Angel de la Guarda Island, probably because of high vertical mixing processes present in the zone. The results were compared with dissolved metal concentrations reported for the Gulf of California (Cd, Mn and Fe) and the North Pacific Ocean. The resulting linear regression of the results vs. North Pacific Ocean concentrations indicated that the levels of Cu, Ni and Zn measured in this study were within its 95% confidence level. Furthermore, this comparison was capable of detecting dissolved Fe and Mn enrichments in Gulf of California waters relative to the North Pacific Ocean concentrations. Calculations of total masses of metals associated with algal biomass on the west coast of the Gulf of California indicated that the lowest masses were represented by Cu (108 ± 25 kg) and Ni (184 ± 52 kg), whereas Pb (1.1 ± 0.6 ton) and Fe (10.9 ± 8.5 ton) were the elements with the highest associated masses.

Macroalgae and filamentous turf algae (FTA) are abundant on degraded coral reefs, and the reproductive responses of corals may indicate sub-lethal stress under these conditions. The percentage of gametogenic stages (PGS) and the maximum diameter of eggs (MDE; or egg size) of Orbicella annularis were used to evaluate the effect of long- (7–10 months) and short-term (2.5 months) FTA removal (treatments T1 and T2, respectively) at both the beginning (May) and the end (August) of gametogenesis. Ramets (individual lobes of a colony) surrounded by FTA (T3) or crustose coralline algae (CCA; T4) were used as controls. The removal of FTA enhanced the development of gametes (i.e., a larger and higher percentage of mature gametes (PMG)) of O. annularis for T1 vs. T3 ramets in May and T1 and T2 vs. T3 ramets in August. Similar values of PGS and MDE between gametes from T3 and T4 in both May and August were unexpected because a previous study had shown that the same ramets of T4 (with higher tissue thickness, chlorophyll a cm-2 and zooxanthellae density and lower mitotic index values) were less stressed than ramets of T3. Evaluating coral stress through reproduction can reveal more sensitive responses than other biological parameters; within reproductive metrics, PGS can be a better stress indicator than egg size. The presence of turf algae strongly impacted the development of gametes and egg size (e.g., PMG in ramets with FTA removal increased almost twofold in comparison with ramets surrounded by FTA in August), most likely exerting negative chronic effects in the long run due to the ubiquity and permanence of turf algae in the Caribbean. These algae can be considered a stressor that affects coral sexual reproduction. Although the effects of turf algae on O. annularis are apparently less severe than those of other stressors, the future of this species is uncertain because of the combined impacts of these effects, the decline of O. annularis populations and the almost complete lack of recruitment.

De febrero de 1993 a febrero de 1994 se estudio mensualmente una poblacion intermareal de la carragenofita de importancia economica Chondracanthus canaliculatus (Harvey) Guiry, localizada en la costa noroccidental de Baja California, Mexico. Se determino, en cada muestra de 450 plantas recolectadas al azar, el tamano del talo (medido como la talla de la fronda mas larga) y la presencia o ausencia de cistocarpos y de soros tetrasporangiales. El maximo de talla promedio, 25.02 cm, se registro en junio y el minimo, 11.22 cm, en octubre. Las clases de tamano de la 4 a la 8 (10 a 19.9 cm) fueron dominantes durante casi todo el ano, excepto en junio y julio cuando las clases de tamano de la 10 a la 14 (22 a 3 1.9 cm) alcanzaron sus valores maximos, por lo que se sugiere que la clase 8 sea la minima de cosecha. Se presentaron dos periodos con altas tasas de crecimiento: el primero en junio y julio en clases de talla mayores y el segundo en diciembre y enero en clases de talla menores. Si se consideran unicamente las plantas maduras, las cistocarpicas fueron mas abundantes en los meses frios (noviembre a abril) y las tetrasporicas en los meses calidos (mayo a octubre). Sin embargo, debido al alto porcentaje de plantas inmaduras, se plantea la necesidad de desarrollar un metodo para determinar la caracteristica haploide o diploide de esta alga. An intertidal population of Chondracanthus canaliculatus (Harvey) Guiry, a commercial carrageenophyte, was studied monthly from February 1993 to February 1994 on the northwestern coast of Baja California, Mexico. The thallus size (measured as maximum frond length) and the presence of cystocarps and tetrasporangial sori were determined for each sample of 450 thalli randomly collected at monthly intervals. The maximum average thallus size of 25.02 cm was recorded in June and the minimum average size of 11.22 cm was recorded in October. Size classes 4 to 8 (10 to 19.9 cm) were dominant throughout the year, except in June and July when size classes 10 to 14 (22 to 31.9 cm) reached their greatest values. We therefore propose class 8 as the minimum harvest size. There were two periods with high growth rates: the first in June and July in the larger size classes and the second in December and January in the smaller size classes. Cystocarpic thalli were more abundant in colder months (November to April) and tetrasporic thalli in warmer months (May to October). There is a high percentage of immature plants, so it is necessary to develop a method to determine the haploid or diploid characteristics of this alga.

The biomass of Ulva lactuca beds on the west coast of the Gulf of California was evaluated in 1995, 1996, 1998 and 2000. The total biomass was estimated at four localities, for a total of 12 km of the coastline and a total Ulva bed area of 2.2 km2, and amounted to > 350 tonnes dry weight per year. The pristine conditions of the area make this biomass particularly suitable for commercial utilization as food, food ingredients and fodder. Lower biomass in 1998 apparently reflects an ENSO event.

[1] The Ballenas-Salsipuedes Channel (BSC) is considered an oceanographic province on its own within the Gulf of California. In this region, tidal mixing is modulated by quarterdiurnal, semidiurnal, diurnal, and fortnightly frequencies, producing a strong outcropping of cold and nutrient-rich waters. In this work we analyze the temporal and spatial variability of sea surface temperature (SST) data recorded simultaneously over a period of 1 year in six bays along the BSC. Minimum mean SST differences ( 2.5°C) were recorded in June. The monthly SST anomaly showed that from late October to late January, the channel behaved as a very well mixed region. In contrast, SST anomalies of up to 2.2°C among bays were observed from May to September, indicating intense heat gain in summer and highlighting spatial heterogeneity in the intensity of vertical mixing. Besides the seasonal temperature cycle, influenced by solar irradiation, four main periods (0.25, 0.5, 1, and 15 days) were identified, corresponding to the main timescales of variability induced by the tides. This work demonstrates that the main source of temporal SST variability in BSC is the tide-induced fortnightly modulation, suggesting the possibility of a pulsation mechanism in the outcropping of nutrient-rich waters reaching the surface layer throughout the channel; this could play a crucial role in explaining the exceptionally high biological production of this region.

Las extensas playas localizadas cerca de la frontera México-E.U.A. juegan un papel importante en la economía del municipio de Playas de Rosarito, México. Durante el invierno de 1998, se observó una intensa erosión de las playas de la localidad como resultado de un régimen de oleaje muy energético asociado al evento de El Niño (ENSO) en combinación con altos niveles de marea. La severidad de estas condiciones causó inundaciones y destrucción de varias residencias ubicadas en la posplaya y las capacidades recreacionales y de protección de la playa disminuyeron significativamente. Mediante la comparación de los perfiles de playa se observó que el máximo volumen de arena removido de la playa subaérea fue de 66.9x10-3 m3/m/día y un retroceso promedio de la berma de 2.3 m/día. El desplazamiento máximo hacia tierra de la berma durante el período en estudio fue de 66 m. La altura del perfil final fue de hasta 3.5 m más bajo que el inicial, por lo que es posible que se requiera de un período más prolongado de oleaje bajo para que se restaure la altura del perfil inicial. Es necesario evaluar el papel que juega el dinámico depósito de grava que se observa en la parte norte del área estudiada. La importancia que tiene la playa en la economía local justifica el desarrollo de un programa observacional continuo.doi: sin doi

Se estudió el efecto de El Niño 1997-1998 sobre la biomasa y tamaño de los mantos de Ulva lactuca L. en la costa noroeste del Golfo de California, del lado opuesto al Canal de Ballenas. Las evaluaciones se realizaron en el mes de mayo (primavera) de 1998 y se compararon con años previos (mayo 1995, 1996 y 2000). La investigación muestra que El Niño 1997-1998 tuvo un efecto negativo sobre el área y biomasa de los mantos estudiados. El área se redujo en 70% y la biomasa en 80% respecto a años previos. Se detectó un recobro completo de estos mantos para el año 2000. Se estudió el crecimiento de esta alga bajo condiciones controladas de laboratorio, pero no se detectó un efecto significativo de la irradiancia sobre el crecimiento. Sin embargo, la temperatura afectó significativamente su crecimiento. A 18°C se detectó el óptimo crecimiento y temperaturas de 14°, 22° y 26°C lo redujeron. Temperaturas de 30°C fueron letales para U. lactuca.doi: sin doi

The seasonal variation of the biomass of Gracilariopsis lemaneiformis (Bory) Dawson, Acleto et Foldvik was measured for 18 months in Bahia de las Animas. Maximum biomass per unit area (11.1 kg wet wt m−2) occurred in the spring of 1995 and most of the biomass was lost by summer. Agar gel strength and yield were 891 g cm−2 and 14%, respectively for spring samples. Biomass per unit area was also evaluated during spring from all the beds of G. lemaneiformis in 850 km of the west coast of the Gulf of California. The total biomass estimated in 1995 was 5751 ± 404 dry t. The total biomass for spring of 1996 was about 30% less (4060 ± 246 dry t). Commercial exploitation of G. lemaneiformis started in the west coast of the Gulf of California in 1995.

De febrero de 1993 a febrero de 1994 se estudió mensualmente una población intermareal de la carragenofita de importancia económica Chondracanthus canaliculatus (Harvey) Guiry, localizada en la costa noroccidental de Baja California, México. Se determinó, en cada muestra de 450 plantas recolectadas al azar, el tamaño del talo (medido como la talla de la fronda mas larga) y la presencia o ausencia de cistocarpos y de soros tetrasporangiales. El máximo de talla promedio, 25.02 cm, se registró en junio y el mínimo, 11.22 cm, en octubre. Las clases de tamaño de la 4 a la 8 (10 a 19.9 cm) fueron dominantes durante casi todo el año, excepto en junio y julio cuando las clases de tamaño de la 10 a la 14 (22 a 3 1.9 cm) alcanzaron sus valores máximos, por lo que se sugiere que la clase 8 sea la mínima de cosecha. Se presentaron dos periodos con altas tasas de crecimiento: el primero en junio y julio en clases de talla mayores y el segundo en diciembre y enero en clases de talla menores. Si se consideran únicamente las plantas maduras, las cistocarpicas fueron más abundantes en los meses fríos (noviembre a abril) y las tetraspóricas en los meses cálidos (mayo a octubre). Sin embargo, debido al alto porcentaje de plantas inmaduras, se plantea la necesidad de desarrollar un método para determinar la característica haploide o diploide de esta alga.