Gilberto Gaxiola-Castro

Plankton response to El Niño 1997–1998 and La Niña 1999 in the southern region of the California Current

Abstract The IMECOCAL Program began in 1997, with the objective of sampling plankton systematically in the Mexican region of the California Current. We present results of chlorophyll a concentrations and zooplankton displacement volumes for the eight cruises from September 1997 to October 1999. The abundance of 22 zooplankton groups was also analyzed for the first four cruises. The response of plankton to the 1997–1998 El Nino was atypical. From September 1997 to January 1998, chlorophyll a and zooplankton volume were at typical values (median integrated chlorophyll was 27 mg/m 2 and zooplankton 100 ml/1000 m 3 in 9801/02). After the peak of El Nino, the system shifted to cooler conditions. Integrated chlorophyll gradually increased to a median of 77 mg/m 2 in April 1999. In contrast, zooplankton volumes decreased from October 1998 onward, despite favorable phytoplankton availability in 1999. Zooplankton structure was dominated by copepods and chaetognaths through the ENSO cycle, but interannual changes were evident. In the fall of 1997 there was a higher proportion of copepods, chaetognaths, and other minor groups, while the fall of 1998 zooplankton was richer in salps and ostracods. Historical data from previous Baja California CalCOFI cruises indicated that zooplankton volumes measured during the IMECOCAL cruises were above the long-term mean for the period 1951–1984. This suggests a differential response of plankton to the El Nino of 1997–1998 compared to the El Nino of 1957–1959. Regional differences in zooplankton volumes were also found, with central Baja California having 41% higher biomass than northern Baja California. Volumes from both regions were larger than those recorded by CalCOFI off southern California during 1997–1998, but the situation was reversed in 1999. The higher biomasses in the 1997–1998 El Nino can be attributed to high abundance of salps, which showed an affinity with warm, saline water.

Winter water masses and nutrients in the northern Gulf of California

Hydrographic data (salinity, temperature, O2, PO4, NO3 and SiO2) collected in the northern Gulf of California between February 27 and March 3, 1988, reveal that bottom water formation took place that winter. North of 30.5°N, salinity increased with depth from ∼35.30 practical salinity units (psu) at the surface to 35.57 psu at the bottom of the 200-m deep Wagner Basin; below ∼25 m, temperature was almost homogeneous, at ∼15°C (±0.4°C), with some inversions. The TS diagrams and the distribution of dissolved oxygen and nutrients suggest that the most likely origin of this bottom water is the shallow coastal region ( 2.2 μM; nitrate, >22 μM; and silicate, >35 μM) indicate the presence of oceanic water from Guaymas Basin, probably Subsurface Subtropical Water. The boundary between the two regimes was ∼18 km wide, with clearly defined bottom fronts and intrusions at all depths. Of the several late-winter hydrographic data sets available, only that from March 1973 presents a similar distribution of high-salinity bottom water. Therefore interannual variability (not necessarily El Nino-Southern Oscillation (ENSO) related) can have a profound effect on vertical convection, which can occur both in ENSO and non-ENSO years. An important and as yet unexplained difference between the two data sets is that there was more Gulf of California Water in the northern Gulf of California in 1973 than in 1988.

Spatial distribution of chlorophyll α and primary productivity in relation to winter physical structure in the Gulf of California

The spatial distribution of chlorophyll α and productivity of phytoplankton and their relation with stratification was studied during winter of 1990 in the Gulf of California. According to the stratification parameter of the water column (Ф) we can distinguish three different zones during winter: one with strong turbulence (5<Ф<10 J m−3) close to the islands; the second zone with moderate turbulence (15<Φ<30 J m−3) in the central Gulf, and the third with high stratification (40<Ф<60 J m−3) in the southern Gulf. The lowest stratification was registered in the area near to Angel de la Guarda and Tiburon Islands, associated with low surface temperature (14–15°C), high surface chlorophyll a concentration (2.0–4.0 mg m 3) and low primary productivity (1.0–2.5 mgC m−3 h −1). Higher integrated values of chlorophyll a and primary productivity were measured in the central-southern area, related to moderate turbulence or stratification. Spring tides and wind stress appeared to be the principal physical factors for the high productivity in the central Gulf during winter. Moderate turbulence in the central-southern Gulf allows phytoplankton growth, however high turbulence in the area close to the large islands result in low primary productivity values.

Photosynthetic parameters of northern gulf of California phytoplankton

Abstract At the end of autumn, 1981, and end of spring-beginning of summer, 1982, we generated photosynthesis-irradiance curves for phytoplankton from five locations, in each cruise, of the northern Gulf of California. In general, photosynthetic parameters, phytoplankton abundance and chlorophyll a had large vertical changes within the euphotic zone, even in cases where thermohaline vertical homogeneity indicated high instability. Nutrient concentrations were very high. The assimilation number ( P m B ), in general, decreased with depth due to conditioning of phytoplankton to lower irradiances. Surface ( P m B ) values had a range of 2–15 mg C ( mg Chla) −1 h −1 . Where the bottom of the euphotic zone was within the thermocline, P m B was 4–15% of the values for surface waters; and where it was within the mixed layer, P m B was 25–85% of the values for surface waters. This was due to greater residence time of phytoplankton at depth in the first case. Very strong turbulence by storm winds caused relatively low P m B values in a December station, possibly because of mixing of the near-surface phytoplankton with relatively deep populations conditioned to low irradiances. Our data indicate that in the Gulf moderate turbulence causes higher P m B values than strong turbulence or stratification.

Oceanographic conditions over the continental shelf off Magdalena Bay (Mexico) in 2011–2012

Resumen en: The hydrophysical results obtained during six oceanographic cruises in 2011 (February, April, July, and October) and 2012 (February and April) over a 50-...

Sea Surface Temperature Influence on Terrestrial Gross Primary Production along the Southern California Current

Some land and ocean processes are related through connections (and synoptic-scale teleconnections) to the atmosphere. Synoptic-scale atmospheric (El Niño/Southern Oscillation [ENSO], Pacific Decadal Oscillation [PDO], and North Atlantic Oscillation [NAO]) decadal cycles are known to influence the global terrestrial carbon cycle. Potentially, smaller scale land-ocean connections influenced by coastal upwelling (changes in sea surface temperature) may be important for local-to-regional water-limited ecosystems where plants may benefit from air moisture transported from the ocean to terrestrial ecosystems. Here we use satellite-derived observations to test potential connections between changes in sea surface temperature (SST) in regions with strong coastal upwelling and terrestrial gross primary production (GPP) across the Baja California Peninsula. This region is characterized by an arid/semiarid climate along the southern California Current. We found that SST was correlated with the fraction of photosynthetic active radiation (fPAR; as a proxy for GPP) with lags ranging from 0 to 5 months. In contrast ENSO was not as strongly related with fPAR as SST in these coastal ecosystems. Our results show the importance of local-scale changes in SST during upwelling events, to explain the variability in GPP in coastal, water-limited ecosystems. The response of GPP to SST was spatially-dependent: colder SST in the northern areas increased GPP (likely by influencing fog formation), while warmer SST at the southern areas was associated to higher GPP (as SST is in phase with precipitation patterns). Interannual trends in fPAR are also spatially variable along the Baja California Peninsula with increasing secular trends in subtropical regions, decreasing trends in the most arid region, and no trend in the semi-arid regions. These findings suggest that studies and ecosystem process based models should consider the lateral influence of local-scale ocean processes that could influence coastal ecosystem productivity.

Pelagic Ecosystem Response to Climate Variability in the Pacific Ocean off Baja California

Gilberto Gaxiola-Castro1, Bertha E. Lavaniegos1, Antonio Martinez2, Ruben Castro2, T. Leticia Espinosa-Carreon3 1Centro de Investigacion Cientifica y Educacion Superior de Ensenada. Departamento de Oceanografia Biologica. Carretera Ensenada-Tijuana No. 328. Fracc. Zona Playitas. Ensenada, Baja California, Mexico. C.P. 22860. 2Universidad Autonoma de Baja California. Facultad de Ciencias Marinas. Kilometro 107 carretera Tijuana-Ensenada. Ensenada, Baja California, Mexico. C.P. 22810. 3Centro Interdisciplinario de Investigacion para el Desarrollo Integral Regional (CIIDIR) Unidad Sinaloa-IPN. Blvd. Juan de Dios Batiz Paredes #250. Col. San Joachin. C.P. 81101. Guasave, Sinaloa, Mexico.

Phytoplankton photosynthetic parameters from the Gulf of California southern region

Se determino la respuesta fisiologica del fitoplancton en la zona eufotica por medio de experimentos fotosintesis-irradiancia realizada de junio del 2000 a junio del 2001 en la Bahia de La Paz, Golfo de California, Mexico. Durante el periodo estratificado que comprende de junio a septiembre (indice de estratificacion > 200 J m-3) el numero de asimilacion (Pm) estuvo representado por un valor promedio de 3,7 mg C m-3 h-1, mientras que de noviembre a febrero, cuando la columna de agua fue homogenea (indice de estratificacion = 0 J m-3) fue de 9,2 mg C m-3 h-1. La eficiencia fotosintetica maxima a baja irradiancia (α) tuvo un valor promedio de 0,017 mg C m-3 h-1 (µmol cuanta m-2 s-1)-1 representativo del periodo estratificado, mientras que durante el periodo homogeneo fue de 0,063 mg C m-3 h-1 (µmol cuanta m-2 s-1)-1. Los parametros fotosinteticos (Pm y a) durante la mayor dinamica de la zona epipelagica evidencian la fotoaclimatacion del fitoplancton a la irradiancia promedio en la zona eufotica. Valores altos de Pm se relacionaron con la abundancia de diatomeas (Pseudo-nitzschia delicatissima, Chaetoceros compressus y Coscinodiscus perforatus), mientras que los valores menores de este parametro se asociaron con el grupo de los dinoflagelados. Los valores promedio estimados para el parametro de saturacion de luz (Ek) fueron 334, 173 y 91 µmol cuanta m-2 s-1 para superficie, 10 y 1% de la zona eufotica, respectivamente. De manera general, la comunidad fitoplanctonica estuvo dominada por nanofitoplancton (2-20 µm) durante todo el periodo considerado.

Nutrientes inorgánicos y producción del fitoplancton en una laguna costera subtropical de México

Resumen es: La variabilidad temporal de los datos hidrograficos, nutrientes, clorofila a del fitoplancton y la tasa de produccion primaria fueron analizados en la La...

Producción primaria y eficiencia fotosintética en Cuenca Alfonso, Bahía de La Paz, Golfo de California, México

Quantification of photosynthetic efficiency and productive capacity of the phytoplankton community was the objective of the surveys that were conducted in December 2005, May and August 2006; and February, May and November 2007 in Bahia de La Paz (Cuenca Alfonso). Samples of water were collected from 7 levels of surface irradiance (100, 55, 33, 10, 3, 1 and 0.1%), of the euphotic zone (Zeu). In situ primary production estimations were performed by 14C assimilation methodology. There were 2 basic assimilation ratios patterns; one with subsurface maxima during February and May 2007 and other with a tendency of increasing values as the lower limit of the Zeu was approached (December 2005; May and August