Cascading effects of the ctenophore Mnemiopsis leidyi on the planktonic food web in a nutrient-limited estuarine system

Abstract

Increasing biomasses of gelatinous zooplankton presumably have major implications for the structure and function of marine food webs at large; however, current data on lower trophic levels are scarce, as most studies have focused on the immediate effects on zooplankton and fish larvae only. We examined the short-term impact of larvae and adults of the invasive ctenophore Mnemiopsis leidyi on a summer planktonic food web in the estuarine southern Baltic Sea, with special emphasis on the microbial loop. Grazing by M. leidyi reduced the mesozooplankton biomass, followed by increased dinoflagellate biomass in treatments with M. leidyi. While chlorophyll a increased most in the treatments with M. leidyi, small phytoplankton and ciliates decreased in all treatments. M. leidyi had a slight effect on bacterial abundance, but not on bacterial production, ectoenzymatic activities, or community composition. Undetectable levels of phosphate and a gradual accumulation of dissolved organic carbon during the experiment suggested a malfunctioning microbial loop scenario. The experiment shows that direct and indirect short-term effects of M. leidyi on the estuarine food web are limited to higher trophic levels and indicates that top-down and bottom-up consequences of M. leidyi expansions on the microbial loop will likely depend on local nutrient conditions.

Ciliates in Planktonic Food Webs: Communication and Adaptive Response

“…Biomanipulation was mainly applied at the height of the eutrophication but is still being used occasionally (e.g., Ha et al 2013;Peretyatko et al 2012). This method was supported by the finding that predator control at a higher trophic level may 'cascade down' to the lower levels of the food web (Carpenter et al 1985;Dinasquet et al 2012).…”

Identifying the drivers of abundance and size of the invasive ctenophore Mnemiopsis leidyi in Northwestern Mediterranean lagoons

“…The relationship between M. leidyi abundance and chlorophyll-a is probably indirect as high chlorophyll-a values suggest low grazing pressure from the mesozooplankton which is retrieved from the water column by M. leidyi predation Riisgård et al, 2012b;McNamara et al, 2013). This is supported by Dinasquet et al (2012) mesocosm experiments during which they found an increase of chlorophyll-a concentration in all the treatments due to M. leidyi reduction of the mesozooplankton biomass which was followed by an increase of dinoflagellates biomass. Additional factors, not taken into account in this model, may contribute shaping the abundance variability of M. leidyi in the Northwestern Mediterranean Sea as observed in other basins: e.g.…”

Stimulated bacterioplankton growth and selection for certain bacterial taxa in the vicinity of the ctenophore Mnemiopsis leidyi

“…While it is well documented that this voracious predator (Colin et al, 2010) may graze upon a variety of plankton taxa (Granhag et al, 2011) and elicit cascading food web effects (Dinasquet et al, 2012), bottom-up effects associated with presence and activity of M. leidyi have received less attention.…”