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

Abstract

The spatiotemporal distributions of the planktonic copepod communities in Tokyo Bay in 1986-1987, when it was in a more eutrophicated condition than at present, were examined using zooplankton samples collected by vertical hauls of Kitahara's quantitative net (mesh opening, 0.1 mm) from 19 stations in July, August, October, December 1986 and February 1987. The total abundance of copepods ranged from 3 × 10 4 to 2750 × 10 4 ind. m −2 with peaks in July and August and a remarkable decrease in October. Oithona davisae dominated most samples with the subdominant species Acartia omorii in the inner and central areas in December and February, and Paracalanus parvus s.l. in the outer area in October, December and February. The copepod communities in the inner and central areas were classified into 2-4 groups in July, August and October, whereas they mostly comprised a single group in December and February. These differences in distribution pattern might be related to seasonal changes in environmental factors such as river discharge, intrusion of high-salinity outer-bay water, and hypoxic water. In comparison with the community in July 1948, the area of dominance of O. davisae had expanded to the whole bay and A. omorii had decreased in the inner area in July 1986, while other copepods such as P. parvus s.l. and Microsetella norvegica had decreased in the whole bay.

Response of marine copepods to a changing tropical environment: winners, losers and implications

“…The increased abundance and occurrence particularly of non-calanoid species explains the increased copepod taxonomic distinctness observed after impact. A similar change in community structure from a community dominated by Acartia to one dominated by Oithona has been reported from colder regions (e.g., Itoh & Nishida, 2015 ; Rice, Dam & Steward, 2015 ; Uye, 1994 ; Winder & Jassby, 2011 ). The decline of once-dominant Acartia species over decades seems to be a global manifestation, attributed not just to sea warming but also to other anthropogenic impacts.…”

“…The decline of once-dominant Acartia species over decades seems to be a global manifestation, attributed not just to sea warming but also to other anthropogenic impacts. Factors implicated include SST rise due to global warming; e.g., A. clausii ( Conversi, Peluso & Fonda-Umani, S, 2009 ) and A. tonsa ( Kimmel, Boynton & Roman, 2012 ); eutrophication or/and hypoxia, e.g., A. tonsa ( Kimmel, Boynton & Roman, 2012 ) and A. omori ( Itoh & Nishida, 2015 ; Uye, 1994 ); the combined effects of the above factors, e.g., A. tonsa ( Kimmel, Boynton & Roman, 2012 ), and shifts in food web structure, e.g., Acartia spp. ( Winder & Jassby, 2011 ).…”

“…The other small copepod species such as the paracalanids are broadcast spawners which were neither impacted by the power plant nor other anthropogenic activities in Klang Strait. However, it has been reported that the small paracalanids decreased in eutrophicated waters elsewhere due to hypoxic condition ( Itoh & Nishida, 2015 ; Uye, 1994 ). Consequently, if paracalanids in Klang Strait suffer high mortality due to anthropogenic impacts, this must be compensated for by their continuous reproduction and fast growth rate throughout the year in high temperature and excess food environments (see Escribano et al, 2013 ; Liang & Uye, 1996 ).…”

Effects of temperature and phytoplankton community composition on subitaneous and resting egg production rates of Acartia omorii in Tokyo Bay

“…Finally, the possible effect of prey availability on the small-scale horizontal distribution of A. omorii in Tokyo Bay should be noted. Itoh and Nishida 67 reported that the abundance of A. omorii was higher on the east side of Tokyo Bay than on the west side. Chlorophyll a concentration was generally higher on the west side of Tokyo Bay in summer; however, on the east side of Tokyo Bay, it was higher in winter 68 .…”

Change in zooplankton community in Onagawa Bay, northeastern Japan after the Tohoku Earthquake and tsunami in 2011 off the Pacific coast of Japan

“…6 and 8, not shown). In Tokyo Bay, this species occurs also mainly in the central and outer areas (Itoh & Nishida 2015). The distributional depth of M. norvegica was found in the mid-deeper layer in Tokyo Bay by water bottle samplings (Anakubo & Murano 1991).…”