Original paper

Interactions between submerged and floating plant species with different types of nutrient uptake in sand and fertile sediments

Cao, Qian-Jin; Wang, Ling

Abstract

Interactions between submerged and floating plants are generally related to nutrient levels in aquatic ecosystems, but few studies have compared species with different types of nutrient uptake. We hypothesize that, under nutrient-limited conditions, species that take up nutrients from both the sediment and the water column would have superior growth than species with similar life forms that absorb nutrients only from the water column but that their superiority would disappear under eutrophic conditions. We cultivated six different species pairs (pairwise combinations of the following four species: submerged Myriophyllum spicatum L. and floating Hydrocharis dubia (Bl.) Backer, which absorb nutrients from both the sediment and the water column, and submerged Ceratophyllum demersum L. and floating Spirodela polyrhiza (L.) Schleid, which take up nutrients only from the water column in sand and fertile sediments). In sand, rooted M. spicatum had a more significant advantage over floating plants than did unrooted C. demersum, and the submerged plants had less significant negative effects on H. dubia than on S. polyrhiza. In fertile sediment, however, no advantage of the submerged species was observed in mixtures with S. polyrhiza, and even the submerged species demonstrated significant disadvantages against co-cultured H. dubia. Our results imply that differences in types of nutrient uptake among aquatic species may play an important role in determining their relative competitive ability.

Keywords

competitionmacrophytephosphorus limitationmyriophyllumspirodelahydrocharisceratophyllum