Abstract.-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 Bahía 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 (Z eu ). In situ primary production estimations were performed by 14C assimilation methodology. There were 2 basic assimilation ratios patterns; one with subsurface maxima during En mayo 2007, el máximo (13,23 mg C (mg Cla) -1 h -1 ) se asoció con la profundidad de la capa de mezcla. Al integrar la producción primaria (PP), se obtuvo un valor superior a los 350 g C m -2 año -1 , lo cual sugiere que la bahía es de carácter productivo alto. Se observó un incremento significativo en la PP al considerar el 0,1% de la irradiancia superficial como el límite inferior de la zona eufótica.Palabras clave: Eficiencia fotosintética, producción primaria, razón de asimilación, zona eufótica INTRODUCCIÓNAl igual que todos los ecosistemas, el sistema epipelágico del océano requiere de la entrada de carbono inorgánico para la síntesis de la materia orgánica a través de la fotosíntesis. En ésta transformación el fitoplancton tiene un papel primordial, ya que al ser consumido por el zooplancton y otros organismos planctónicos, los compuestos sintetizados son incorporados a la trama trófica marina. Esto implica además la transferencia o flujo de materia orgánica producida en la zona eufórica hacia zonas profundas del océano (Ducklowet al. 2001, BarocioLeón et al. 2007, al formar un vínculo entre el dominio planctónico y nectónico con el bentónico. A pesar de que el proceso fotosintético se genera principalmente en la zona eufótica (Z eu ), tradicionalmente definida por la
Resumen.-Se determinó la respuesta fisiológica del fitoplancton en la zona eufótica por medio de experimentos fotosíntesis-irradiancia realizada de junio del 2000 a junio del 2001 en la Bahía de La Paz, Golfo de California, México. Durante el periodo estratificado que comprende de junio a septiembre (índice de estratificación > 200 J m -3 ) el número de asimilación (P m ) 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 homogénea (índice de estratificación = 0 J m -3 ) fue de 9,2 mg C m -3 h -1 . La eficiencia fotosintética máxima 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 homogéneo fue de 0,063 mg C m. Los parámetros fotosintéticos (Pm y α) durante la mayor dinámica de la zona epipelágica evidencian la fotoaclimatación del fitoplancton a la irradiancia promedio en la zona eufótica. Valores altos de P m se relacionaron con la abundancia de diatomeas (Pseudo-nitzschia delicatissima, Chaetoceros compressus y Coscinodiscus perforatus), mientras que los valores menores de este parámetro se asociaron con el grupo de los dinoflagelados. Los valores promedio estimados para el parámetro de saturación de luz (E k ) fueron 334, 173 y 91 μmol cuanta m -2 s -1 para superficie, 10 y 1% de la zona eufótica, respectivamente. De manera general, la comunidad fitoplanctónica estuvo dominada por nanofitoplancton (2-20 μm) durante todo el periodo considerado. Palabras clave: Parámetros fotosintéticos, zona eufótica, Golfo de CaliforniaAbstract.-Phytoplankton physiologic response in the euphotic zone was determined by photosynthesis-irradiance experiments carried out between June 2000 and June 2001 at Bahia de La Paz, Gulf of California, Mexico. A stratified water column was present, from June to September (stratification index > 200 J m -3 ), with the assimilation number (P m ) represented by an average of 3.7 mg C m -3 h -1 , while for the period from November through February, the water column was homogeneous (stratification index = 0 J m -3 ) and the average was 9.2 mg C m -3 h -1 . The maximum photosynthetic efficiency at low irradiances (α) of 0.017 mg C m -3 h -1 (μmol quanta m -2 s -1 ) -1 was the representative average for the stratified period, while 0.063 mg C m -3 h -1 (μmol quanta m -2 s -1 ) -1 was the corresponding value for the homogeneous period. The photosynthetic parameters (P m and α) had an increase during mixing conditions, as result of phytoplankton photoacclimation to average irradiance in the euphotic zone. Diatom abundance (Pseudo-nitzschia delicatissima, Chaetoceros compressus and Coscinodiscus perforatus) were related with higher values of P m , while lowest values of this parameter are associated with the dinoflagellate group. Average values estimated for the light saturation parameter (E k ) were 334, 173 and 91 μmol quanta m -2 s -1 for the surface, 10 and 1% of the euphotic zone, respectively...
Understanding the susceptibility of coastal ecosystems to nutrient loads from anthropogenic sources and the extent of eutrophication in subtropical and tropical estuaries is still a challenge. This study assessed eutrophication in Guaymas Bay, a subtropical lagoon that receives nutrient-rich urban wastewater discharges. Eutrophication was evaluated by means of the Assessment of Estuarine Trophic Status model. Our results showed that the trophic status of Guaymas Bay was “good.” It is important to consider that: (1) the dissolved oxygen and chlorophyll a levels observed are indicative of a healthy ecosystem, and (2) the key factors explaining this finding are the high susceptibility to eutrophication of the lagoon and the dominance of macroalgae species that respond to nutrient enrichment. This implies that the Overall Eutrophic Condition Index of the Assessment of Estuarine Trophic Status model is a valuable tool for use as an eutrophication indicator based on the abundance of primary producers (macroalgae and phytoplankton). One source of uncertainty in the application of the model to this semi-arid coastal lagoon deals with estimating its susceptibility to eutrophication. The model showed that the lagoon is a highly sensitive ecosystem; however, significant factors are in place, such as an adequate water exchange, that reduce its susceptibility to eutrophication. In conclusion, the trophic status observed at Guaymas Bay is acceptable; however, an environmental management plan is necessary to prevent any adverse effects of eutrophication.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.