AME 41:131-143 (2005) - doi:10.3354/ame041131
Feeding by red-tide dinoflagellates on the cyanobacterium Synechococcus
Hae Jin Jeong1,*, Jae Yeon Park1, Jae Hoon Nho2, Myung Ok Park1, Jeong Hyun Ha1, Kyeong Ah Seong1, Chang Jeng3, Chi Nam Seong4, Kwang Ya Lee5, Won Ho Yih6
ABSTRACT: We investigated the feeding by 18 red-tide dinoflagellate species on the cyanobacterium Synechococcus sp. We also calculated grazing coefficients by combining the field data on abundances of the dinoflagellates Prorocentrum donghaiense and P. micans and co-occurring Synechococcus spp. with laboratory data on ingestion rates obtained in the present study. All 17 cultured red-tide dinoflagellates tested (Akashiwo sanguinea, Alexandrium catenella, A. minutum, A. tamarense, Cochlodinium polykrikoides, Gonyaulax polygramma, G. spinifera, Gymnodinium catenatum, G. impudicum, Heterocapsa rotundata, H. triquetra, Karenia brevis, Lingulodinium polyedrum, Prorocentrum donghaiense, P. minimum, P. micans, and Scrippsiella trochoidea) were able to ingest Synechococcus. Also, Synechococcus cells were observed inside the protoplasms of P. triestinum cells collected from the coastal waters off Shiwha, western Korea, during red tides dominated by the dinoflagellate in July 2005. When prey concentrations were 1.1 to 2.3 × 106 cells ml1, the ingestion rates of these cultured red-tide dinoflagellates on Synechococcus sp. (1.0 to 64.2 cells dinoflagellate1 h1) generally increased with increasing size of the dinoflagellate predators (equivalent spherical diameters = 5.2 to 38.2 µm). The ingestion rates of P. donghaiense and P. micans on Synechococcus sp. increased with increasing mean prey concentration, with saturation occurring at a mean prey concentration of approximately 1.1 to 1.4 × 106 cells ml1. The maximum ingestion and clearance rates of P. micans on Synechococcus sp. (38.2 cells dinoflagellate1 h1 and 4.3 µl dinoflagellate1 h1) were much higher than those of P. donghaiense on the same prey species (7.7 cells dinoflagellate1 h1 and 2.6 µl dinoflagellate1 h1). The ingestion rates of red-tide dinoflagellates on Synechococcus sp. were comparable to those of the heterotrophic nanoflagellates and ciliates on Synechococcus spp., so far reported in the literature. The calculated grazing coefficients attributable to small Prorocentrum spp. (P. donghaiense + P. minimum) and P. micans on co-occurring Synechococcus spp. were up to 3.6 and 0.15 h1, respectively. The results of the present study suggest that red-tide dinoflagellates potentially have a considerable grazing impact on populations of Synechococcus.
KEY WORDS: Cyanophyte · Grazing · Harmful algal bloom · Ingestion · Marine · Protist · Red tide
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