Biological test of plankton by in situ adaptability and ballast water treatment system

Abstract

Possible introduction of foreign species through ship ballast water and the survivorship of natural population of plankton after treatment of electrochemical reactor were investigated to regulate and manage the ship ballast water discharge in the natural environment. Phyto- and mesozooplankton were sampled by vertical hauls with the standard type net (20 and 200 µm mesh, respectively) through manhole type ballast water tanks of five bulk carriers in Incheon port dock of Korea in 2005. Most identified planktons were similar to the seasonally occurring species around Korean waters except symbiotic copepod. Even though the phytoplankton is not foreign species, it can pose negative effect on the endemic plankton community when facing with their preferring environment. Therefore, recovery experiments were conducted by injection of ballast water originated phytoplankton into two types of media such as Incheon port sea water filtered through 0.2 µm mesh filter paper and F/2 media. Following time series incubation, it was evident that some species like Skeletonema costatum and Leptocylindrus danicus can grow fast in the natural seawater after being discharged rather than in F/2 media. Following the treatment of electrochemical reactor, the survivorship of planktonic zooplankton was assessed immediately through direct observations, while phytoplankton and bacteria survivorship were assessed by immediate observations through green filter and through 48h incubations. Under the condition 5 tons/h, 2.8-3.0 V, 75 ampere (NaOcl: 10 ppm), dominant phytoplankton, S. costatum, Ceratium fusus, Thalassionema nitzschioides, turned from red into green after they passed the reactor, indicating no live chlorophyll-a remained. And no live E. coli and coliform bacteria were remained after being passed through the reactor. With respect to zooplankton, live copepods were not observed in the post-reactor samples. The remove efficiency of phytoplankton and copepods was up to 100% b