Aveneu Park, Starling, Australia

10-fold al. 2002). Sommer et al. (2002)

10-fold in the Mar Menor, Spain, while wastewatertreatment decreased phosphate by one-tenth; theseconditions were associated with annual blooms of 2rhizostome scyphomedusae, Cotylorhiza tuberculataand Rhizostoma pulmo, since 1993 (Pérez-Ruzafa et al.2002). These examples suggest that high nitrogenratios may favor jellyfish blooms. Other modificationsof these coastal environments have also occurred, andare discussed below in ‘Construction’.Eutrophication also causes complex changes in thefood web. Greve & Parsons (1977) first hypothesized2 parallel food paths in the oceans, a diatom-basedpath that ends with large consumers having ‘highenergy’ requirements (e.g. whales), and a flagellatebasedpath that ends with ‘low energy’ consumers (e.g.jellyfish). Shifts from the diatom- to the flagellatebasedpath could result from pollution, eutrophicationor climate changes. This hypothesis has been elaboratedover time (Smayda 1993, Parsons & Lalli 2002,Sommer et al. 2002). Sommer et al. (2002) proposed3 types of nutrient regimes: (1) upwelling systems, withhigh ratios of silica (Si) to nitrogen (N) and phosphate(P) plus diatoms and flagellates; (2) oligotrophicoceanic systems with low nutrients and predominatedby picoplankton (5 to 10 ?m); and (3) eutrophicatedcoastal systems, with elevated N and P and summerblooms of inedible algae (often large dinoflagellates).High N:P ratios shift the phytoplankton communityaway from diatoms towards flagellates and jellyfish(Nagai 2003). Eutrophication also is connected withsize reduction of the zooplankton community (Uye1994); the zooplankton in eutrophic Tokyo Bay isalmost entirely very small Oithona davisae copepods,which primarily feed on small flagellates (Uchima1988). Thus, nutrient enrichment may change thelower trophic structure towards a microplanktonbasedfood web. This size-reduction of the lowertrophic levels is thought to be detrimental to fish, mostof which are visual predators that prefer large zooplankton,thereby benefiting jellyfish, which are notvisual and consume small as well as large prey.


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