Variation of Phytoplankton and Zooplankton Communities in a Sea Area, with the Building of an Artificial Upwelling Structure

Abstract

In this study, we investigated changes in the standing crop, species composition, and ecological index ofphytoplankton and zooplankton caused by the installation of an artificial upwelling structure in the sea area. Thestanding crop of phytoplankton and zooplankton in 2009, when the artificial upwelling structure was completed,increased 50-fold and 2.3-fold, respectively, from 2005 when the artificial upwelling structure was installed. Duringthe investigation period, however, the correlation between the standing crop of zooplankton and the standing crop ofphytoplankton did not show significant difference (SPSS, p 0.05). Phytoplankton and zooplankton species showeda 2.47-fold increase in a total of 94 species and a 1.68-fold increase in a total of 27 species, respectively, from 2006 to2009. During the study period, the dominant species of phytoplankton were Chaetoceros didymus (16.5%),Chaetoceros pseudocrinitus (8.5%), Copelatus anastomosans (7.6%), and Skeletonema costatum (6.0%), and thedominant species of zooplankton were Paracalanus parvus (21.6%), Evadne tergestina (6.6%), Paracalanus aculeatus(6.1%), Lucifer intermedius (5.7%), and Sinocalanus tenellus (5.4%), and copepods accounted for the majority ofzooplankton. Phytoplankton species diversity index and richness index increased significantly from 1.68 to 2.45 andfrom 1.61 to 3.65, respectively, in the period from 2006 to 2009, but dominant species index decreased from 0.55 to0.40 in the same period. It was known that bigger artificial upwelling structures caused a gradually rising upwellingeffect and that in the study area, from 2006 to 2009, the ecosystem was changing to a more stable one where a varietyof species habitat gradually.