Limnetica 34

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The phenology of wetland submerged macrophytes related to environmental factors

Sara Calero, William Colom & Maria A. Rodrigo
2015
34
2
425-438
DOI: 
10.23818/limn.34.32
Citation: 

Little 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 València 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 degree-days (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.

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