Jellyfish modify the response of planktonic assemblages to nutrient pulses

Abstract

The short-term effects of pulses of nutrients and jellyfish Catostylus mosaicus on planktonic assemblages were investigated in field-based experiments using 3 m 3 mesocosms. Experiments ran for 5 d and were repeated in autumn and spring at Lake Illawarra, a coastal lagoon in New South Wales, Australia. Experiments consisted of 2 orthogonal treatments, addition/non-addition of nutrients and presence/absence of jellyfish, and were designed to determine how bottom-up (i.e. addition of nutrients) and top-down (i.e. predation by jellyfish) processes influence planktonic assemblages, both independently and in combination. During both experiments, nutrients stimulated primary production and caused changes in phytoplankton assemblages. Nutrients also stimulated production of large tintinnids, suggesting that bottom-up processes may influence 2 trophic levels. Mesozooplankton were consistently depleted in mesocosms containing jellyfish. Jellyfish also caused changes in microzooplankton assemblages, indicating that top-down processes also cascade to at least 2 trophic levels. In mesocosms to which both nutrients and jellyfish were added during spring, concentrations of the red-tide forming, heterotrophic dinoflagellate Noctiluca scintillans were 20 times greater than in mesocosms to which nutrients were added alone. We hypothesize that addition of nutrients stimulated production of centric diatoms, the main prey of N. scintillans, but that a bloom of N. scintillans only formed when jellyfish were also present because jellyfish grazed on populations of herbivorous mesozooplankton (particularly the calanoid copepod Gladioferens), which generally out-competed N. scintillans for diatom prey. These data provide the first empirical evidence linking jellyfish to the formation of red tides.

Seasonal changes and population dynamics of the ctenophore Mnemiopsis leidyi after its first year of invasion in the Kiel Fjord, Western Baltic Sea

“…Although M. leidyi has been traditionally considered as strictly carnivore, empirical investigations have shown that all size classes of M. leidyi larvae and postlarvae consumed nano-and microplankton in excess of their minimum food requirement, which may represent a main nitrogen source for population growth (Sullivan and Gifford 2004). This can have important ecological implications since by exerting high predation pressures on ciliates a potential impact on the structure of microzooplankton assemblages may favour in some cases the formation of red tides, as shown by Pitt et al (2007) in mesocosms experiments. Moreover, we cannot exclude cannibalism and predation on other gelatinous zooplankton, as suggested by the high concentrations of jellyfish planula larvae in the gut content of M. leidyi in summer (Javid Pour, personal observation).…”

Are Jellyfish Taking Over The World?

“…Early action against the jellyfish could be crucial to avoid large scale alterations to the pelagic ecosystems. Concern for 3rd world countries dependant on fish to provide daily nutrients and protein should be paramount, as with an expanding human population, developing countries dependant on the ocean could be faced with challenging situations within marine environments in future years [1,51,52].…”

“…Palomares et al [52] Populations grow exceptionally under favourable conditions Medusae shrink when starved and resume normal growth and reproduction within days of feeding…”

Spatial and seasonal variations of large tintinnid ciliates in Shenhu Bay of China

“…copepods, larval fish) and competitors (e.g. aloricate ciliates, rotifers) (Miyaguchi et al 2006, Pitt et al 2007, Sato et al 2010. The tintinnid community may also be affected by other abiotic factors, such as temperature, salinity, turbulence, the nutrient level (Capriulo & Carpenter 1983, Sanders 1995, Wang et al 2013.…”