Plankton Investigation in Inlet Waters Along the Coast of Japan -Xvi. The Plankton of Tokyo Bay in Relation to the Water Movement-

Spatiotemporal distribution of planktonic copepod communities in Tokyo Bay whereOithona davisaeFerrari and Orsi dominated in mid-1980s

“…Field surveys were conducted on 1 July, 25 August, 27 October, 24 December 1986 and 19 February 1987 at 17 stations located in the inner and central area (the area north of the line linking the Capes-Kannonzaki and Futtsumisaki) in the bay, and at two additional stations in the outer area ( Figure 1). Plankton samples were collected by vertical tows from the bottom to the surface of Kitahara's quantitative net (Japan meteorological agency 1970; mouth diameter, 22.5 cm; mesh opening, 100 μm) which is same Hensen-type net as in Yamazi (1955). Although mounting a flow meter on this net is difficult due to its small mouth, a large filtering ratio can be ensured by fitting the canvas headpiece with a hoop.…”

“…To compare with results in 1948 (Yamazi 1955), copepod abundance per unit area (ind. m −2 ) was converted into abundance per unit volume of water (ind.…”

“…Although the distribution of the community of planktonic copepods, which play an important role as the primary consumers in the bay, was investigated in the whole bay area in 1948 (Yamazi 1955), there was no additional information for c.20 years after that study. Since 1970, many scientists have studied seasonal fluctuations (Anakubo and Murano 1991;Itoh and Aoki 2010;Tachibana et al 2013), vertical distribution (Anakubo and Murano 1991;Itoh et al 2011) and long-term fluctuations (Marumo and Murano 1973;Nomura 1993), but such studies were conducted at a few restricted stations.…”

“…Tokyo Bay extends 80 km north to south, and is an estuarine environment due to discharge from the Tamagawa River, Arakawa River and Edogawa River, etc., in the innermost area and connects with the Pacific oceanic environment via the entrance area. Although investigation of the whole bay is necessary for understanding this diverse bay ecosystem, previous studies were restricted to data obtained in July 1948 (Yamazi 1955), November 1970 (Yamazi 1973) and August 1989 (Uye 1994).…”

“…In order to get basic information for monitoring, we investigated the horizontal distribution of planktonic copepod communities in Tokyo Bay in summer, autumn and winter on the basis of samples collected during July 1986-February 1987, applying the same sampling method as in Yamazi (1955). We also compared species composition and copepod abundance patterns between 1948 and 1986 and discussed seasonal differences in relation to environmental factors.…”