Abstract
AIM: We evaluated the composition and community attributes of invertebrates associated to Eichhornia azurea at Cascalho Lagoon, Upper Paraná River, Mato Grosso do Sul State, Brazil, over a hydrological cycle, as well the possible influence of abiotic factors upon these attributes. METHODS: The samplings were conducted during 2010 in the rainy and dry periods at stands of E. azurea. The attributes evaluated were abundance, richness, diversity, evenness and dominance. The abiotic factors, temperature, dissolved oxygen, pH and turbidity were summarized by a Principal Component Analysis (PCA). In order to verify possible differences between the mean values of the community attributes and the scores of the PCA axis in different periods, we employed null models analysis of variance. The influence of abiotic factors on each attribute was evaluated through Pearson correlations. RESULTS: We captured 3,052 individuals, distributed into 32 taxa, belonging to the phyllum Mollusca, Annelida, Nematoda and Arthropoda. Among the assessed attributes, only abundance and richness varied significantly between periods, with higher values during the rainy period. Chironomidade was dominant in both periods, whereas Notonectidae and Cyclopoida were rare in the rainy, and Bivalve, Decapoda, Haliplidae, Trichoptera and Pyralidae, in the dry period. A temporal distinction was evident only for the PCA axis 1, which represented gradients in temperature, dissolved oxygen and pH. Among the community attributes, only abundance was significant and negatively correlated with this axis. CONCLUSION: We attested that: i) the rainy period should add favorable conditions for invertebrates' higher richness and abundance in this macrophyte; ii) only the later attribute was influenced by limnological gradients.
Highlights
Lentic environments, marginal lagoons, usually possess at their littoral regions extensive macrophyte stands (Schreiber and Brauns, 2010), which constitute abundant substrate for aquatic invertebrates (Albertoni et al, 2007; Ohtaka et al, 2011)
The margins are colonized by grass and other aquatic macrophytes, such as Eichhornia crassipes, Utricularia gibba, Salvinia sp. and, mostly, Eichhornia azurea
The most abundant taxa were Chironomidae (1,541.6 ind/100 g) and Gastropoda (474.1 ind/g) that together corresponded to 55.2% of the total collected
Summary
Marginal lagoons, usually possess at their littoral regions extensive macrophyte stands (Schreiber and Brauns, 2010), which constitute abundant substrate for aquatic invertebrates (Albertoni et al, 2007; Ohtaka et al, 2011). The association of invertebrates to aquatic macrophytes creates numerous benefits for these, as direct or indirect obtaining of food, shelter, oxygen and other favorable conditions for their growth (Padial et al, 2009; Ohtaka et al, 2011) Compounding this type of vegetation, Eichhornia azurea Kunth, a rooted aquatic macrophyte with long stems and emerged floating leaves (Padial et al, 2009), stands out by the efficiency in colonizing lentic waters, and is frequently pointed out as abundant in Brazilian lakes (Esteves, 1998; Thomaz et al, 2004). The maintenance of this community structure is essential for the balanced functioning of aquatic environments
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