## 3 Results
### Assessment of Biogeochemical Characteristics in Gwangyang Bay  
The clustering analysis using the SOM characterized biogeochemical features of Gwangyang Bay into four distinct patterns. The four clusters determined by the SOM shaped spatiotemporal heterogeneity of the data samples at Gwangyang Bay (Figure 4 and Appendix B). It is remarkable to discern the spatiotemporal pattern that cluster 1 included site 1 to site 6 of June, cluster 2 site 7 to site 15 of June, cluster 3 site 1 to site 8 of September, and cluster 4 site 9 to site 15 of September as well as site 14 and site 15 of June (Figure 4a). In addition, the estimate of neighboring distances among the clusters indicated that the clusters were firstly separated as top (cluster 3 and cluster 4) and bottom (cluster 1 and cluster 2). As a consequence, the clustering result manifested that plankton community of Gwangyang Bay was primarily characterized by seasonal influences between early and late summer (i.e., June and September at Gwangyang Bay), and then was spatially distinguished. Strictly speaking, site 14 and site 15 of June were grouped as cluster 4 which represented the outer bay of late summer, \begin{table}
\begin{tabular}{c c c} \hline
**Site** & **eDNA Metabarcoding** & **CMI** \\ \hline GY1 & _Acropora_, _Candacia_, _Capella_, _Orzias_ & _Acartia_, _Paracalamus_ \\ GY2 & _Acropora_, _Candacia_, _Capella_, _Corophilum_, _Oryzias_ & _Acartia_, _Corycaus_, _Centropages_, _Corycaus_, _Oithona_, _Paracalamus_, _Sagitta_ \\ GY3 & _Acartia_, _Centropages_ & _Acartia_, _Noctiluca_, _Oithona_, _Paracalamus_, _Sagitta_ \\ GY4 & _Acartia_, _Acropora_, _Carpella_, _Corophilum_ & _Acartia_, _Corycaus_, _Noctiluca_, _Oithona_, _Paracalamus_, _Sagitta_ \\ GY5 & _Acartia_, _Acropora_, _Centropages_ & _Acartia_, _Noctiluca_, _Paracalamus_, _Sagitta_ \\ GY6 & _Acropora_, _Hematodinium_ & _Paracalamus_, _Sagitta_ \\ GY7 & _Acartia_ & _Centropages_, _Noctiluca_ \\ GY8 & _Acropora_, _Carpella_, & _Centropages_, _Noctiluca_ \\ GY9 & _Acartia_, _Acropora_, _Candacia_, _Centropages_, & _Centropages_, _Noctiluca_ \\ GY10 & _Acropora_, _Thalassisira_ & _Centropages_, _Corycaus_, _Sagitta_ \\ GY11 & _Candacia_, _Carpella_, _Centropages_ & _Centropages_ \\ GY12 & _Centropages_, _Hematodinium_, & _Centropages_, _Paracalamus_ \\ GY13 & _Candacia_, _Centropages_ & _Centropages_, _Paracalamus_ \\ GY14 & _Hematodinium_ & _Oithona_ \\ GY15 & _Hematodinium_ & _Oithona_ \\ \hline \end{tabular}
\end{table} 
Table 2: Dominant plankton groups observed during the summer season (June and September) in Gwangyang Bay. but they were placed on the bottom of cluster 4, which was characterized as the outer bay of early summer. Namely, these two sites appear to represent similar features on coastal plankton community, regardless of temporal changes in summer. Several water quality parameters delineated ambient physicochemical conditions associated with plankton community in Gwangyang Bay (Figure 4b). Water temperature was relatively lower in cluster 2 and higher in cluster 3 among the four groups. The higher salinity of the outer bay matched well with cluster 2 and cluster 4. Cluster 3 represented the inner bay of the summer, exhibiting lower salinity was higher water temperature. Concerning nutrient concentration, total phosphorus (TP) concentrations were higher in June (cluster 1 and cluster 2 in Figure 4) than in September (cluster 3 and cluster 4 in Figure 4). In the spatial scale, TP was higher at the inner bay (cluster 1 and cluster 3 in Figure 3) than at the outer bay (cluster 2 and cluster 4 in Figure 4). In addition to TP, total nitrogen (TN) concentrations were conspicuously high in cluster 3, which represented the inner bay in late summer. Total carbon (TC) concentrations displayed opposite patterns against TN. Among the four clustering groups, chlorophyll \(a\) (Chl-_a_) concentrations were highest at the inner bay in early summer, while were lowest at the outer bay in late summer.