Phytoplankton communities and stoichiometry are interactively affected by light, nutrients, and fish

Abstract

We examined the separate and interactive effects of light, nutrients, and zooplanktivorous fish on phytoplankton nutrient stoichiometry, taxonomic richness, community composition, and the associations among these variables. We manipulated light supply, nutrient supply, and zooplanktivorous fish (presence or absence), in a factorial design using mesocosms containing regional phytoplankton and zooplankton assemblages. C : N and C : P were highest under high nutrients and high light. We observed interactive effects on the relative abundance of major phytoplankton taxa. Chlorophytes were most abundant in the majority of the treatments, although cyanobacteria dominated under high light, low nutrients, and with fish present. Cryptomonads were rare in all but the low-light, high-nutrient treatment. Relative abundance of diatoms was negatively affected by light, but only in the presence of fish. Chlorophyte relative abundance (% chlorophytes) was positively correlated with seston C : P, while relative abundances of diatoms and cryptomonads were negatively correlated with C : P. Phytoplankton taxon richness was positively associated with both % chlorophytes and seston C : P, and the number of chlorophyte taxa increased disproportionately with total taxon richness. Assemblage-level stoichiometric responses may be driven not only by direct responses to resource supply ratios, but also by algal community response. In particular, factors that increase taxonomic richness and both the richness and biomass of chlorophytes also result in increased seston C : P. Our results suggest strong feedbacks between phytoplankton community composition and stoichiometry, induced by interactive effects of light, nutrients, and predators.

Supplemental effects of mixed ingredients and rice bran on the growth performance, survival and yield of Nile tilapia, Oreochromis niloticus reared in fertilized earthen ponds

“…The present findings are corroborated by results reported by Degefu et al (2011), Mette et al (2011), Ssanyu et al (2011) and Shahabuddin et al (2012). The results further showed statistically comparable phytoplankton biomass and abundance between the ponds under MI and RB treatments.…”

Intra‐ and interspecific differences in nutrient recycling by European freshwater fish

“…Furthermore, whereas for most fish species, biomass-standardised excretion rate tends to decrease with increasing fish mass (i.e. All these potential effects of diversity in fish nutrient excretion rates and community structure on nutrient recycling need to be experimentally tested using in situ (Taylor, Flecker & Hall, 2006;Schaus et al, 2010) or mesocosm experiments (Kohler et al, 2011;Mette et al, 2011), or modelling approaches (Tarvainen et al, 2002;McIntyre et al, 2007). More importantly, few species showed an increasing biomass-standardised excretion rate with fish mass (i.e.…”

Carnivore identity mediates the effects of light and nutrients on aquatic food‐chain efficiency

“…Food chain efficiency (FCE), i.e. In aquatic ecosystems, primary production, algal stoichiometry and species composition, and hence energy flow to higher trophic levels, are often constrained by light and/or nutrient supply (Sterner et al, 1997;Urabe et al, 2002;Dickman et al, 2008;van de Waal et al, 2010;Mette et al, 2011;Rowland et al, 2015), thus it is important to understand how these environmental drivers may impact FCE. In aquatic ecosystems, primary production, algal stoichiometry and species composition, and hence energy flow to higher trophic levels, are often constrained by light and/or nutrient supply (Sterner et al, 1997;Urabe et al, 2002;Dickman et al, 2008;van de Waal et al, 2010;Mette et al, 2011;Rowland et al, 2015), thus it is important to understand how these environmental drivers may impact FCE.…”