Original paper

Seasonal changes in tissue nutrient concentrations of macroalgae and aquatic angiosperms in Mediterranean ponds (North-Western Spain)

Fernández-Aláez, Camino; Fernández-Aláez, Margarita


Seasonal changes in nitrogen and phosphorus content in two aquatic angiosperm species (Myriophyllum alterniflorum and Potamogeton natans) and two species of macroalgae (Chara fragilis and Nitella translucens) were investigated in three ponds located in north-western Spain. The aim of the study was to determine whether nutrient contents exhibit species-specific seasonal variation, and whether the macronutrient levels are related to the respective growth phase of the species. We hypothesized that angiosperms, due to a more developed root system contribute more to the retention of nutrients. Above-ground biomass was usually collected once a month between May 1996 and June 1997, and water samples were collected seasonally. Total nitrogen and total phosphorus in the sediment and the concentration of orthophosphate in sediment interstitial water were measured in July 1996. Both angiosperms and macroalgae presented lowest nutrient levels in summer and highest contents before or at the beginning of the growing season. In all three ponds, seasonal changes in the standing stock of nutrients were consistent with biomass development. Changes in biomass over time was the principal factor affecting the seasonal variation in macrophyte nutrient content. Macrophyte growth form and the presence of rhizoids in charophytes, in contrast to a well developed root system in angiosperms, affected the nutrient content of the different macrophyte species. We showed that in the Mediterranean ponds studied the angiosperms were able to accumulate a greater quantity of phosphorus in their biomass than the macroalgae, despite the fact that some Charophytes prolonged their growth into winter. The greater production of biomass by the angiosperms, particularly P. natans, and the greater capacity of M. alterniflorum to take up phosphorus suggests that charophytes act less as nutrient sinks in these Mediterranean ponds.


macrophytesseasonal changesnutrientsnutrient standing stockmediterranean ponds