Studies on metabolic balance in hermatypic corals have been unable to separate the analysis of animal’s respiration from that of plant. The objective of this research was to determine the metabolic balance in the mutualistic symbiosis polyp-algae through incubations in respirometric chambers of twelve fragments of coral. The species studied Porites panamensis (Scleractinia: Poritidae), Verrill, 1866 was collected near La Paz, Baja California Sur, México. Experiments were performed during fall 2009 and winter 2010. Water temperature, salinity, dissolved oxygen, pH, irradiance and photosynthetic pigments were measured every two hours during the incubation times. The concentration of pigments was determined through spectrophotometry. The maximum primary production was at 12:00 h, with 3.80 mg O2∙l-1∙h-1 for fall and 4.92 mg O2∙l-1∙h-1 for winter. According to the P : R (Production : Respiration) ratio of 1.90 for fall and 2.07 for winter, the mutualistic symbiosis in P. panamensis showed a predominantly autotrophic behavior. The relative quotients of chlorophyll concentrations (mg∙polyp-1), Chl a : Chl c2, were 1.0 : 0.69 for fall and 1.0 : 1.22 for winter; while ratio of concentrations chlorophyll a : carotenes , Chl a : carotenes (both in mg∙polyp-1), were 1.0 : 2.13 for fall and 1.0 : 1.88 for winter. The high relative concentrations of Chl c2 and carotenes with respect to Chl a is explained as an adaptive response to high irradiance. Balance metabólico en la simbiosis mutualista pólipo-alga en el coral hermatípico Porites panamensis en La Paz, Baja California Sur, México Estudios del balance metabólico en corales hermatípicos han sido incapaces de separar el análisis de la respiración animal y vegetal. El objetivo en este trabajo fue determinar el balance metabólico en la simbiosis mutualista alga-pólipo a través de incubaciones en cámaras respirométricas en doce fragmentos de coral. Los experimentos se realizaron en otoño del 2009 e invierno del 2010. La especie estudiada fue Porites panamensis (Scleractinia: Poritidae), Verrill, 1866, recolectada en La Paz, Baja California Sur, México. La temperatura del agua, salinidad, oxígeno disuelto, pH, irradiación y pigmentos fotosintéticos fueron registrados cada dos horas durante los tiempos de incubación. Los pigmentos fotosintéticos se determinaron mediante espectrofotometría. La producción primaria máxima fue a las 12:00 h, con 3.80 mg O2∙l-1∙h-1 para otoño y 4.92 O2∙l-1∙h-1 para invierno. De acuerdo con el cociente P : R (Producción : Respiración) con valor de 1.90 para el otoño, y 2.07 para el invierno, la simbiosis mutualista en P. panamensis muestra un comportamiento predominantemente autótrofo. Los cocientes relativos de concentración de clorofilas (mg ∙polyp-1), Cl a : Cl c2, fueron 1.0 : 0.69 para otoño y 1.0 : 1.22 para invierno, mientras que la relación de clorofila a : carotenos, Cl a : carotenos (ambos en mg∙polyp-1), fueron de 1.0 : 2.13 para otoño y 1.0 : 1.88 para invierno. Las altas concentraciones relativas de Cl c2 y carotenos con respecto a Cl a se explican como una respuesta adaptativa a una mayor irradiancia.
A B S T R A C TIntratidal variability and flux of salt, chlorophyll-a and suspended materials were evaluated in a shallow tropical tidal channel linking a coastal lagoon to the western Gulf of Mexico. Velocity, temperature and conductivity were used to calculate the fluxes. Data were recorded during three tidal velocity cycles (tvc) under extreme river discharge conditions. Chlorophyll-a and suspended materials were determined below the surface. In both seasons (dry and rainy), the flow was ebbdominated and with longer duration than when in flood. Maximum current velocities were 0.30 m s -1 in May (dry season) and 0.60 m s -1 in September (rainy season). In the dry season the mean chlorophyll-a export was of 7.56 Kg over tvc while the import was of 3.32 Kg. In the rainy season mean export (47.3 Kg) was 6 times greater than the import (7.93 Kg over tvc). Phytoplankton was dominated by organisms of marine origin. The mean of exported, suspended materials in the rainy season (111.3 Kg) was 4.6 times greater (859 Kg) than that in the dry season (184.7 Kg over tvc). Tidal velocity asymmetry is an effective mechanism of exportation, introducing relatively warm and saltier water into the river through the tidal channel. R E S U M OA variabilidade intramaré, o fluxo de salinidade, a clorofila-a e material em suspensão foram avaliados em um canal superficial de maré tropical em uma lagoa costeira ao oeste do Golfo do México. Os dados de velocidade, temperatura e condutividade foram usados para cálculo dos fluxos durante três ciclos de velocidades das marés (tvc) sob condições extremas de descarga. A Clorofila-a e material em suspensão foram determinados abaixo em subsuperfície. Em ambas as estações (seca e chuvosa), o fluxo dominante foi durante o refluxo e com duração maior durante o fluxo de entrada. A máxima velocidade encontrada foi 0.30 m s -1 em maio (estação seca) e 0.60 m s -1 em setembro (estação chuvosa). Durante a época seca foram exportadas 7.56 Kg de clorofila-a, enquanto a importação foi de 3.32 Kg. Durante a temporada de chuva a média exportada (47.3 Kg) foi seis vezes maior que a importada (7.93 Kg). A concentração media de material em suspensão exportado durante a época de chuvas (111.3 Kg) foi 4.6 vezes maior (859 Kg) que durante estação de seca (184.7 Kg). A assimetria das marés é um mecanismo efetivo de transporte, introduzindo no rio águas relativamente quentes e mais salinas através do canal de maré.
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