## 3 Results
### Density of Growth-Limiting Bacteria  
The densities of growth-limiting bacteria (GLB: the sum of algicidal bacteria (AB) and growth-inhibiting bacteria (GIB)) detected from seawater, and macroalgal samples at Stns.1 and 2, were shown in Table 2 and Figures 4 and 5. GLB targetting at least one HAB species were detected both in seawater and _U. pertusa_ samples collected at Stn. 1 (Figure 4). The densities of GLB showed that activities against _Chattonella antiqua_ were \(3.5\times 10^{2}\) CFU mL\({}^{-1}\) in FLB and \(1.9\times 10^{2}\) CFU mL\({}^{-1}\) in PAB (Figure 4a,b). GLB against _Heterocapsicularisquama_ and _Karenia mikimotoi_ were detected only in PAB with densities of \(1.9\times 10^{2}\) CFU mL\({}^{-1}\) and 93 CFU mL\({}^{-1}\), respectively (Figure 4b). AB targeted _C. antiqua_, and _H. circularisquama_ were detected from _U. pertusa_ on the pumice stone with the same density of \(5.9\times 10^{6}\) CFU g\({}^{-1}\) wet weight (Figure 4c). GIB targeted _H. circularisquama_ was detected from _U. pertusa_ on the floating cage at a concentration of \(1.5\times 10^{6}\) CFU g\({}^{-1}\) wet weight (Figure 4d). There were no GLB negatively affecting the growth of _Alexandrium catenella_ and _Heterosigna akashiwo_ at Stn. 1. GLB targeting at least one HAB species were also detected from all samples collected at Stn. 2 (Figure 5). The density of GLB showed that the activity against _H. circularisquama_ was detected in FLB with a density of 69 CFU mL\({}^{-1}\) (Figure 5a). GLB isolated from PAB at Stn. 2 had a wide range of activities affecting four HAB species except for _A. catenella_ with densities ranging between \(1.1\times 10^{2}\) CFU mL\({}^{-1}\) and \(7.9\times 10^{2}\) CFU mL\({}^{-1}\) (Figure 5b). GLB affecting the growth of _A. catenella_, _H. circularisquama_, and _K. mikimotoi_ were found from the _S. duplicatum_ biofilm with densities of \(4.0\times 10^{5}\) CFU g\({}^{-1}\) wet weight, \(2.4\times 10^{6}\) CFU g\({}^{-1}\) wet weight and \(4.0\times 10^{5}\) CFU g\({}^{-1}\) wet weight, respectively (Figure 5c). GLB affecting _C. antiqua_, and _H. circularisquama_ were detected from _G. elegans_ biofilm with densities of \(7.6\times 10^{5}\) CFU g\({}^{-1}\) wet weight and \(1.5\times 10^{6}\) CFU g\({}^{-1}\) wet weight, respectively (Figure 5d). GLB isolated from _C. ohkuboana_ targetted four HAB species, except _K. mikimotoi_, with densities of \(1.0\times 10^{6}\) CFU g\({}^{-1}\) wet weight for _A. catenella_, \(5.0\times 10^{5}\) CFU g\({}^{-1}\) wet weight for _C. antiqua_, \(5.0\times 10^{5}\) CFU g\({}^{-1}\) wet weight for _H. akashiwo_, and \(4.0\times 10^{6}\) CFU g\({}^{-1}\) wet weight for _H. circularisquama_,  
Figure 3: The densities of culturable bacteria (**a**): seawater, (**b**): macroalgal biofilms and total bacteria directly counted with DAPI staining (**c**): seawater, (**d**): macroalgal biofilms and at Stns. 1 and 2. Total (\(\Circinus\)) shown on (**a**) and (**c**) are expressed as the sum of particle-associated bacteria (PAB) and free-living bacteria (FLB). A to F are macroalgal samples used to enumerate the densities.  
respectively (Figure 5e). GLB were found in _U. pertusa_ with densities of \(3.0\times 10^{6}\) CFU g\({}^{-1}\) wet weight for _A. catenella_, \(6.0\times 10^{6}\) CFU g\({}^{-1}\) wet weight for _H. circularisquama_ and \(2.0\times 10^{6}\) CFU g\({}^{-1}\) wet weight for _K. mikimotoi_, respectively (Figure 5f). GLB negatively affecting the growth of all five HAB species were detected at the natural macroalgal bed (Stn. 2).  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Date**} & \multirow{2}{*}{**Station**} & \multirow{2}{*}{**Sample Name**} & \multirow{2}{*}{**Sample Type**} & \multicolumn{6}{c}{**The Density of GLB against Five Different HAB Species**} \\  & & & & & \multicolumn{2}{c}{**(CFU mL\({}^{-1}\) or g\({}^{-1}\) Wet Weight)**} \\ \cline{6-1