Seasonal variations in the trophic relationship between the scyphomedusa Aurelia aurita s.l. and mesozooplankton in a eutrophic brackish-water lake, Japan

• Published in: Plankton & benthos research Vol. 4; no. 1; pp. 14 - 22
• Main Authors: Han, C.H.(Hiroshima Univ., Higashi-hiroshima (Japan)), Kawahara, M, Uye, S
• Format: Journal Article
• Language: English
• Published: Tokyo The Plankton Society of Japan, The Japanese Association of Benthology 2009; The Plankton Society of Japan and The Japanese Society of Benthology
• Subjects: AGUA SALOBRE; APPAREIL DIGESTIF; AURELIA AURITA; Bivalvia; BRACKISH WATER; CADENA ALIMENTARIA; CHAINE ALIMENTAIRE; COELENTERATA; DESARROLLO ESTACIONAL; DEVELOPPEMENT SAISONNIER; DIGESTIVE SYSTEM; EAU SAUMATRE; FOOD CHAINS; Freshwater; JAPAN; JAPON; LAC; LAGOS; LAKES; Marine; mesozooplankton; NIVEAU TROPHIQUE; NIVELES TROFICOS; Oithona davisae; predation impact; Scyphomedusa; SEASONAL DEVELOPMENT; seasonal occurrence; SISTEMA DIGESTIVO; TROPHIC LEVELS; ZOOPLANCTON; ZOOPLANKTON; Japan
• ISSN: 1880-8247; 1882-627X
• DOI: 10.3800/pbr.4.14

The seasonal variations in trophic relationship between the moon jelly Aurelia aurita s.l. and mesozooplankton were investigated in a brackish-water lake, Honjo District, Japan from June 2005 to August 2006. The medusae occurred abundantly (average abundance and biomass: 0.55 medusae/cubic m and 58.8 mgC/cubic m, respectively) during warm seasons (i.e. June-November, 2005), but were very scarce or absent during the remaining seasons. The mesozooplankton biomass fluctuated from 1.3 to 150mgC/cubic m (overall average: 60.5 mgC/cubic m) irrespective of the medusa biomass variation. Mesozooplankton were preyed upon by medusae almost non-selectively; the small copepod Oithona davisae and bivalve larvae were the predominant prey, comprising 52-99% (average: 85%) of the gastric pouch contents. The medusa population ingestion rate on mesozooplankton varied from 0.11 to 12.8 mgC/cubic m/d which corresponded to 0.6 to 29% of the mesozooplankton biomass per day and to 1.6 to 47% of mesozooplankton daily production rate. A. aurita medusae was certainly a key component of the zooplankton community, but they did not exert any significant top-down control as to suppress mesozooplankton biomass in this eutrophic lake.