par- 3 février 2009
mardi 3 février à 13h00
Influence of jellyfish blooms on nutrient cycling and plankton production
Kylie Pitt (Australian Rivers Institute – Coast and Estuaries, Griffith University, Australia) présentera un séminaire le mardi 3 février à 13h00 en salle de réunion du COM à Luminy :
Due to their boom and bust population dynamics and the enormous biomasses they can attain, jellyfish can have a very large influence on the cycling of C, N and P in the systems they inhabit. Like corals, some jellyfish contain photosynthetic symbiotic zooxanthellae and the presence of zooxanthellae has a major influence on the way in which jellyfish acquire and recycle C, N and P. Non-zooxanthellate jellyfish accumulate C, N and P predominantly through predation on zooplankton and recycle N and P to the water column via excretion which may, in turn, stimulate phytoplankton production. In contrast zooxanthellate jellyfish derive part of their C from the translocation of photosynthetic products from their zooxanthellae and, exhibit no or minimal net release of N and P and may actively compete with phytoplankton for dissolved inorganic nutrients. Here I review the contrasting roles of zooxanthellate and non-zooxanthellate jellyfish in C, N and P cycling, report on an empirical experiment on the influence of zooxanthellate and non-zooxanthellate jellyfish on primary production and planktonic assemblages and examine the influence of decomposing jellyfish blooms on sediment oxygen demand and nutrient dynamics.