Species-specific response of phytoplankton to zooplankton grazing in tropical eutrophic reservoirs

Abstract

Aim To test the hypothesis that zooplankton changes the structure of phytoplankton in tropical reservoirs by reducing the biomass of algal species susceptible to herbivory. Methods We experimentally evaluated the species-specific responses of phytoplankton to zooplankton within eutrophic reservoirs with different phytoplankton community structure in northeastern of Brazil. Water samples were collected from the subsurface in coastal regions of the Apipucos and Mundaú reservoirs in January/2012 and November/2014, respectively, and transported to the laboratory. The experiments were performed in Erlenmeyer flasks (1 liter) filled with water from the sample sites and were maintained for five days in the laboratory conditions. Two treatments were maintained (1) with phytoplankton and the presence of the native zooplankton and (2) without native zooplankton. Results Zooplankton proved to be an important factor, modifying the structure of the phytoplankton community, especially in the Apipucos reservoir. In this reservoir, we observed a significant reduction of biomass in diatom Cyclotella meneghiniana, and the chlorophyte Chlamydomonas sp., and an increase in the biomass of Raphidiopsis raciborskii. In the Mundaú reservoir, we observed a significant reduction of C. meneghiniana and R. raciborskii, while cyanobacteria Microcystis aeruginosa increased their biomasses in the presence of zooplankton. Conclusions These results show the importance of the microalgae community structure in phytoplankton-zooplankton interactions for food webs in tropical environments, as well as support the role of zooplankton in fostering cyanobacterial growth and maintain algal blooms.

Isolated and combined effects of a submerged macrophyte and a cladoceran on the interactions between Microcystis aeruginosa (Cyanobacteria) and Raphidocelis subcapitata (Chlorophyta)

“…In tests with the addition of cladocerans, we observed that the cyanobacterial biomass was significantly reduced from the fourth day and the green alga was stimulated on the eighth day, differing statistically from the control. This result differs from previous findings in the literature, where zooplankton are assumed to select the palatable food source in co-cultures, and thus stimulate cyanobacterial growth (Leitão et al, 2018;Severiano et al, 2021). However, in experimental studies, Guo and Xie (2006) found that populations of M. micrura pre-exposed to toxic strains M. aeruginosa may become more resistant to cyanobacteria metabolites compared to other large cladocerans, enabling the predation of cyanobacteria.…”

“…Among the main bloom-forming genera, Microcystis stands out with wide geographical distribution and several microcystin-producing morphospecies (Harke et al, 2016;O'Neil et al, 2012;Wiegand & Pflugmacher, 2005). To control algal blooms, laboratory and in situ studies using aquatic plants (e.g., Amorim et al, 2019a;) and zooplankton organisms (e.g., Amorim et al, 2019b;Diniz et al, 2019;Severiano et al, 2018;Severiano et al, 2021) have been carried out in tropical regions, specifically in the Northeastern region of Brazil. In that region, the biomanipulation of fish to control eutrophication and phytoplankton blooms can show negative (Menezes et al, 2010), positive or no effects (e.g., Dantas et al, 2019;Okun et al, 2008).…”

“…Moreover, cyanotoxins can affect more seriously larger zooplankton than small organisms, however, the former ones can graze more efficiently on phytoplankton (Guo & Xie, 2006). With that, some zooplankton species can select palatable phytoplankton organisms, which can, in turn, increase cyanobacterial biomass (Leitão et al, 2018;Severiano et al, 2021).…”

Surface Temperature Influences the Population of Limnothrissa miodon in Lake Kariba

“…Cynaphytes are associated with the production of toxins [7,8] and are often unigestible, indigestible, or nutritionally poor [9,10]. Many species of Chlorophytes are less palatable due to long splines and long processes [11]. In Lake Kariba, Limnothrissa miodon mainly feeds on zooplankton, especially the Cladoceran species Bosmina longirostris [12,13].…”