Effects of essential fatty acids and N and P‐limited algae on the growth rate of tropical cladocerans

Abstract

SUMMARY 1. In this study, the effects of nutrient (N and P) deficiency and the importance of essential polyunsaturated fatty acids (PUFA) [eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)] to tropical cladocerans, growth and reproduction were determined in a growth bioassay. 2. The animals were fed N/P‐sufficient, N‐deficient and P‐deficient algae, and also N and P‐deficient algae supplemented with fish oil emulsions rich in EPA and DHA. 3. Cladocerans showed different responses to nutrient‐deficient algae and also to supplements of fish oil emulsions. Moina micrura was most sensitive to P‐deficient alga and, surprisingly, grew better and produced more eggs in N‐deficient alga than in N/P sufficient alga. Ceriodaphnia cornuta was less sensitive, growing well in both N and P‐deficient algae. This species, however, had a lower clutch size in N‐deficient alga. On the other hand, Daphnia gessneri was the most sensitive to mineral limitation, showing decreased growth and clutch size in both nutrient‐deficient algae. 4. The PUFA supplements to nutrient‐deficient algae increased growth rates only for M. micrura and C. cornuta, suggesting that these fatty acids are important food requirements for these species.

Driving forces of the diel distribution of phytoplankton functional groups in a shallow tropical lake (Lake Monte Alegre, Southeast Brazil)

“…Reductions in biomass of these groups were observed at night. Cryptophytes are extremely edible for zooplankton and contain high concentrations of PUFA (Polyunsaturated fatty acids; Ahlgren et al, 1992), and are an important food item of these herbivores (Gullati and DeMott, 1997;Ferrão-Filho et al, 2003a). An experimental study has suggested that high cryptophycean biomass in the summer may have contributed to increased growth of cladocerans in Lake Monte Alegre (Ferrão-Filho et al, 2003b).…”

Competição, predação e variação temporal de microcrustáceos planctônicos no Lago Monte Alegre

“…Esses aspectos foram confirmados em testes sobre qualidades mineral, bioquímica e morfológica do séston do Lago Monte Alegre (Fileto et al, 2007a, b) e sobre os efeitos da limitação de nutrientes sobre o crescimento dos cladóceros (Ferrão-Filho et al, 2003b). A produção secundária de microcrustáceos influenciada por ambos os fatores, alimento e temperatura, é variável entre as espécies e entre diferentes classes etárias, como já testado por Minto (2009).…”

“…A reprodução de D. gessneri é também a mais afetada pelas condições do séston no inverno em relação a outras espécies (Ferrão-Filho et al, 2003b;Fileto et al, 2007b), além de ser sensível à limitação mineral (Ferrão-Filho et al, 2003 a, b) e à presença de cianobactérias (Fileto et al, 2004). Provando a influência de cianobactérias sobre alguns daphnideos, a espécie Daphnia carinata, existente em um lago chinês, foi competitivamente inferior do que outros cladóceros pequenos na presença de altas concentrações das cianobactérias (Chen et al, 2007).…”

C and P in aquatic food chain: A review on C:P stoichiometry and PUFA regulation

“…Brett et al (2000) also concluded that phytoplankton food quality decreases as the C:P ratio of the algae increases above 300. Of course, at C:P > 1000, PUFAs can still be important and might not be limiting to herbivores (Ferrāo-Filho et al, 2003). At high light condition, though the rate of C fixation increases (resulting high C:P), it cannot be efficiently transferred to higher trophic level due to P-deficient food selectivity by herbivores.…”