The introduced bivalve Limnoperna fortunei boosts Microcystis growth in Salto Grande reservoir (Argentina): evidence from mesocosm experiments

Abstract

In order to assess the effects of the introduced bivalve Limnoperna fortunei on watercolumn properties of Salto Grande reservoir, experiments were conducted using six 400 L mesocosms: 2 with 100 mussels, 2 with 300 mussels, and 2 controls (without mussels). At 0, 1, 2, 3, 7, 14, 21, 28, and 35 days we measured nutrient and chlorophyll a concentrations, counted and identified the phytoplankton, and estimated the density, size, and number of cells of the colonies of Microcystis spp. Cumulative periphyton growth and total accumulated sediments were assessed in all enclosures at the end of the experiment. Throughout the experiment, in the controls ammonia and phosphates dropped to near zero, whereas in the mesocosms with L. fortunei they increased two-to tenfold. Nitrates decreased in all mesocosms. In the presence of the mussel, chlorophyll a and algal cells dropped until day 3 increasing thereafter, whereas in the controls they increased from day 0. Periphyton growth and sediment accumulation were significantly higher in the mesocosms with mussels that in the controls. Cell density, proportion of colonial cells and colony size of Microcystis spp. increased in all enclosures, but these increases were dramatically (and very significantly) higher in enclosures with 100 and, especially, with 300 mussels, than in the controls. Our results indicate that L. fortunei modifies nutrient concentrations and proportions, and promotes aggregation of solitary Microcystis spp. cells into colonies; both these effects can favor blooms of this often noxious cyanobacteria.

Differential impact of Limnoperna fortunei-herbicide interaction between Roundup Max® and glyphosate on freshwater microscopic communities

“…Differences between this and our study may be explained by differences in the mesocosm dimensions, in the characteristics of the water and the type of formulation applied. Cataldo et al (2012b) reported enhanced growth of periphyton in mesocosm experiments with L. fortunei, which is consistent with our results. Moreover, Pizarro et al (2015a) observed that the active ingredient and L. fortunei acted synergistically on an already established periphytic community (mussels alone and technical-grade glyphosate alone induced a significant increase in periphytic chlorophyll a).…”

“…Three mesocosms had two cages of plastic mesh with 5-mm pore size containing 100 mussels, which were suspended below the water surface (treatment M). Thus, mussel density lies within the range recorded for natural water-bodies (Boltovskoy et al 2009) and is high enough to observe the effect of mussels, as previously assessed in experimental studies with mesocosms (Cataldo et al 2012b;Pizarro et al 2015b). Three mesocosms were treated with technical-grade glyphosate acid (gly) at 6 mg L −1 (≥95 % purity; CAS: 1071-83-6) (treatment G).…”

“…For example, it increases water transparency and decreases suspended matter (Boltovskoy et al 2009;Cataldo et al 2012a), enhances the abundance and richness of benthic invertebrates (Sylvester et al 2007), and represents an important food supply for larval and adult fishes (Paolucci et al 2007(Paolucci et al , 2010aCataldo 2015). Studies involving mesocosms revealed that, in the presence of L. fortunei, there was a decrease in particulate matter and algal density, an increase in ammonium, nitrates and phosphates in water, enhanced periphyton growth (Cataldo et al 2012a, b) and frequent toxic cyanobacterial blooms (Cataldo et al 2012b). Pizarro et al (2015a), who studied the combined effect of technical-grade glyphosate and L. fortunei using outdoor mesocosms, observed that the mussel accelerated the dissipation of glyphosate promoting the availability of phosphorus for the microscopic communities.…”

Feeding selectivity of the invasive mussel Limnoperna fortunei (Dunker, 1857) on a natural phytoplankton assemblage: what really matters?

“…Our results indicate that this mussel primarily fed on particles between 500 and 40 9 10 3 lm 3 , which is consistent with the observation made by Rojas Molina et al (2010). In view of the importance of high biovolume algae as a food item, we expect that the feeding activity of the mussel in its natural environment will lead to an over-dominance of small biovolume algae or even encourage the development of algae that aggregate in mucilaginous colonies as a strategy to avoid mussel predation (Cataldo et al 2012).…”

Acumulação de microcistinas no mexilhão dourado Limnoperna fortunei e riscos para a biota aquática

“…Em virtude da expansão do mexilhão dourado em rios da América do Sul, são reportados inúmeros prejuízos na esfera ambiental dos ecossistemas aquáticos colonizados, como indícios de alterações nas concentrações e proporções de nutrientes, mudanças na estrutura das comunidades fitoplanctônicas e favorecimento da manutenção de florações de cianobactérias (CATALDO et al, 2012). Alguns autores também relatam que a presença de L. fortunei nos ambientes colonizados já o torna parte da dieta alimentar de algumas espécies de peixes do rio Paraná e do Rio da Prata (CANTANHÊDE et al, 2008;VERMULM JUNIOR & GIAMAS, 2008;PAO-LUCCI et al, 2010).…”