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The phenology of wetland submerged macrophytes related to environmental factors

2015; Volume: 34; Issue: 2 Linguagem: Inglês

2660-8537

Sara Calero, William Colom, María A. Rodrigo,

Coastal wetland ecosystem dynamics

espanolExiste poca informacion disponible sobre la fenologia (el ritmo de los eventos recurrentes de los ciclos vitales) de las plantas acuaticas sumergidas, a pesar de que desempenan una importante funcion en los humedales. Con el objetivo de establecer una serie temporal larga sobre la fenologia de las plantas acuaticas, estamos monitorizando una laguna somera creada en una depresion interdunar en el Parque Natural Albufera de Valencia, que presenta una diversidad de macrofitos moderada: dos angiospermas (Potamogeton pectinatus y Utricularia australis) y cuatro carofitos (Nitella hyalina, Chara aspera, Chara vulgaris y Chara hispida). Hemos monitorizado de forma continua la temperatura subacuatica, en dos zonas de distinta profundidad, mediante el uso de sondas con registradores de datos. Hemos medido mensualmente otras variables acuaticas. Las muestras de los macrofitos se recolectaron frecuentemente y se registro la aparicion y maduracion de flores/semillas en angiospermas y de organos sexuales/oosporas en carofitos. Las caracteristicas fenologicas se relacionaron con la temperatura del agua mediante el calculo de la “suma termica-grados dia” (GD). C. hispida mostro diferente ritmo en la aparicion y maduracion de sus organos sexuales (anteridios y oogonios) en funcion de la profundidad: ambos maduraron con 70 GD en las aguas someras (donde parece que la reproduccion no se interrumpio), mientras que en aguas mas profundas los anteridios y los oogonios maduraron tras 270 y 325 GD, respectivamente. Las oosporas necesitaron el doble de calor para madurar en las aguas mas profundas. Aunque N. hyalina presento una fenologia similar, necesito mas tiempo y calor acumulado para ser fertil: mas de 1000 GD para madurar los organos sexuales y oosporas. La reproduccion de C. vulgaris se detecto en primavera, mientras que los ejemplares de C. aspera permanecieron fertiles durante todo el ano. Las dos angiospermas estudiadas florecieron a principios de primavera y mediados de verano. P. pectinatus produjo frutos a los 900 GD, mientras que no se detecto ningun fruto o semilla en U. australis. Estos datos iniciales suponen una primera imagen del ciclo de vida de los macrofitos sumergidos de esta laguna, asi como de las condiciones ambientales basicas que afectan a su fenologia, las cuales estan influidas por el cambio climatico. Este representa el primer estudio detallado de la fenologia de carofitos mediterraneos de humedales y establece las bases para nuestras proximas investigaciones. EnglishLittle information is available about the phenology (i.e., the timing of recurrent events in life cycles) of submerged aquatic plants although they play a key role in wetlands. To establish a long-term data series concerning the phenology of aquatic plants, we are monitoring an artificial shallow pond in a depression between sand dunes in Albufera de Valencia Natural Park (Spain). The macrophyte diversity in the pond is moderate: two angiosperms (Potamogeton pectinatus and Utricularia australis) and four charophytes (Nitella hyalina, Chara aspera, Chara vulgaris and Chara hispida). We continuously monitored the underwater temperature, at two sites and depths, through the use of probes with data-loggers. Other water variables (such as sestonic chlorophyll a, salinity, pH and oxygen) were monitored monthly. Samples of macrophytes were collected frequently to record the emergence and maturation of flowers/seeds in angiosperms, and sexual organs/oospores in charophytes. The relationship of phenological features to water temperature was tracked by calculating growing degreedays (GDD). The timing of the emergence and maturation of the sexual organs (antheridia and oogonia) of C. hispida was dependent on the water depth: both sexual organs had already ripened by 70 GDD in shallower water (where there was no clear interruption of sexual reproduction), whereas in deeper water antheridia achieved this at 270 GDD, oogonia at 325 GDD. Oospores required twice as much heat to ripen in deeper water as in shallower water. Although N. hyalina had a similar phenology, it required more time and accumulated heat to become fertile: more than 1000 GDD were needed to ripen the sexual organs and oospores. C. vulgaris’ sexual reproduction was detected in spring, whereas C. aspera specimens remained fertile during the whole year. Both studied angiosperms flowered in late spring and mid-summer. P. pectinatus produced fruits at 900 GDD, whereas neither fruits nor seeds were detected for U. australis. These initial data represent a first glance at the life cycle of the submerged macrophytes inhabiting this pond as well as at the basic environmental conditions that affect their phenology and which, in turn, are also influenced by climate change. It represents the first detailed study of the phenology of Mediterranean charophytes from wetlands, and it lays the foundation for our forthcoming research.