| 英文摘要 |
This study aimed to investigate the changes of the nutrients and heavy metal surrounding Kueishan Island. Following three years survey, in waters surrounding Kueishan Island, the BOD and COD levels were releatoinship with Chlorophyll a and primary production. While hydrothermal vent gushed, the primary production increased from 48.6 mg/m2/day to 247 mg/m2/day. Nutrients like the nitrate, phosphate and silicate were changes by season. The data showed the lead and iron had the highest concentration in water and mud, respectively. Nevertheless, heavy metal concentrations were in normal range throughout this study. Comparative with these three years data, there was no gushed from the hydrothermal vent by measured the pH and sulfide. While the hydrothermal vent gushed, the DO decreased from 6.5 mg/l to 4.5 mg/l, pH decreased from 7.5 to 5.3, and the sulfide increased from non-detected to 53.2 μM.
This project includes 2 areas of investigation in the surroundings of Gueishan Island. The diversity and abundance of diatoms, dinoflagellates, and Trichodesmium spp. were evaluated by light microscopy. In addition, the species composition of the nitrogen-fixing cyanobacteria, Trichodesmium spp., was further studied by gene sequence analysis in order to solve some uncertainties in species identification based on colony morphology. During the funding period from 2004 to 2006, 9 cruises were conducted in waters surrounding Gueishan Island, and samples for phytoplankton identification and DNA extraction were collected. Based on microscope observation, the regional mean abundance of Trichodesmium spp. ranged from 2.5 to 224 trichomes L-1 with high values occurred in April and September, 2004, as well as in September, 2005. Diatom mean abundance ranged from 3.2×103 to 3.7×104 cells L-1, and high values occurred in April, 2004 and July, 2005. Abundance of dinoflagellates was usually one tenth of that of diatoms with the highest value at 4.0×103 cells L-1. In DNA analysis, the sequence of hetR gene was used to distinguish various species. The analysis indicated that Trichodesmium in the study area could be divided into 4 clusters. The first cluster is composed of T. thiebautii. The second cluster resembles sequences obtained from samples B49 and B51-3, both collected from equatorial Pacific Ocean. The third cluster is apparently a unique cluster for the Gueishan Island area, and the forth cluster is composed of T. erythraeum. From field samples containing mixed Trichodesmium trichomes, sequence analysis revealed that T. erythraeum occupied from 33 to 80% in the entire Trichodesmium communities. However, microscope observation indicated approximately equal amount of T. erythraeum and T. thiebautii in samples. Our results indicate that diversity of Trichodesmium in Gueishan Island area is higher than previously believed, and local Trichodesmium communities contain new taxonomical groups. The inconsistency between morphological identification and DNA sequence analysis is an area that needs further investigation.
In order to study the temporal and spacial distribution and the controlling factors of the oligotrich ciliate around the Yi-Lan Bay, we use the Ocean Research II to proceeding seven samplings during April 2004 to September 2005 to understand the spacial and temporal distribution of the oligitrich ciliate around the Yi-Lan Bay.
The average biomass of the ciliate is 2.1 – 18.6 × 104 cells m-3. There is no seasonal variation in the average of cell number of each season, excluding the highest value in May 2005, and the diversity is not, either. As a result, the number and diversity of ciliate there is stable.
Consequently, there is no apparent variation in the assemblage of the ciliate, but it will be influenced by the input of the fresh water and the upwelling.
The northwest waters off Taiwan are one of the most productive neritic fishing grounds associated with favorable environment for marine community. Copepods have been generally considered to be the keystone species in marine environment. This study is to investigate the community structure of copepods in this region. Eight cruises (CR1186, CR1204, CR1224, CR1250, CR1278, CR1297, CR1306 and CR1320) and 68 plankton net samplings with CTD observation were conducted from Ocean Researcher No.2 during 2004 to 2005. In total, 159 species of copepods belonging to 62 genera and 28 families were identified in this study. MDS analysis divided the sampling stations into 3 groups: outer, middle, and inner. Outer group had the lowest mean abundance of copepods but the highest Shannon-Weaver species diversity and evenness index. Conversely, the highest mean abundance was found in middle group and the lowest diversity and evenness were found in inner group. The result of ANOSIM analysis showed that the typical species of tropical copepods, such as Oncaea venusta and Undinula vulgaris, were highly abundant in outer group. While, the copepods of Temora turbinata, Canthocalanus pauper, and Paracalanus aculeatus were highly abundant in middle group. Than, the typical coastal copepods, such as Corycaeus (Onchocorycaeus) agilis and C. (Ditrichocorycaeus) dahli were highly abundant in inner group. These results suggest that the distribution, abundance, and species composition of copepods are associated with different water masses in the waters off northeastern Taiwan.
Topographic and oceanic features in the surrounding water of Kueishan Island are very complex. This study investigated the variation of biodiversity and spatial-temporal distribution of larval fish correlated to the hydrographic environment. Hydrographic environment showed seasonal variations, especially in the salinity, it was lower in summer and spring. Temperature and salinity with highest variation in the southernmost transect, especially in the eastern waters. In this study, 2,537, 2,198, 3,538, 1,448 and 2,594 individuals of larval fish were collected in May, July, September and November of 2005, and May of 2006, respectively. From the result of species identification, in 2005, there have 146 taxa belonging to 70 families in May, 137 taxa belonging to 66 families in July, 157 taxa belonging to 71 families in September, 129 taxa belonging to 87 families in November. In 2006, have 148 taxa belonging to 95 families in May. The cluster analysis indicated three groups under the 30% similarity, the winter group, the mixing group of spring, summer and autumn, and the I-Lan Ridge group. The average abundance of larval fish was higher in Spring. And the diversity and evenness reveal seasonal progression. According to the hydrographic environment and the cluster analysis, the larval fish community structure was influenced by salinity and depth in the surrounding water of Kueishan Island.
Species composition and occurrence of juvenile fish in by-catches used for animal feed (BcAF) were examined based on the bi-weekly samplings taken from trawlers operated in Guei-San Island, northeastern Taiwan from May to Oct. 2006. Results indicated that bony fish comprised most of the by-catch, while crustacean and elasmobranches could also seasonally, accounted for a substantial % of the catch. In total, 93 families consisting more than 251 species were found for bony fishes. Juvenile by-catch averaged at about 32% of the BcAF, and was highest in the fall. No of species, species richness and diversity examined also were the highest during the fall, but variations by individual vessels were high. The cluster and MDS analyses have showed May, June-August, and Aug.-Oct. assemblages, similar to those reported last year. Analyses based on samples taken from sampling vessels have shown that water depth, instead of the distance away from the shore, was one of the most important factors structuring the demersal fish assemblages in the region. But, influences of the habitat types were less clear. These observations were more evident when only juvenile data were considered. Highest juvenile by-catch in the fall coincide with higher number of species caught and high juvenile richness and evenness, and species diversity indicating that season and depth should be serious considered when close seasons or areas are to be implemented for the management of demersal fish resources in the region.
This study is to elucidate the large crustacean diversity at the Kueishan Island fishing ground. Sampling were maing done by examination the catches of commercial fishing boats of the Dasi fishing port in Yilan County. Moreover, 13 hauls were carried out by using a 2.5 m wide French beam trawl on the general fishing ground and vent area with in the Kueishan Island fishing ground. Altogether 51 families 124 genera 227 species of large crustacean were found, with a composition of 44% of macrurans, 31% of brachyurans, 18% of anomurans , and 7% of stomatopods. Moreover, most are rare and uncommon species (ie. less than 49% occurrence only). 67 species or 32% are economical species. Common and economical species only represented 12% of the total species. This implies that the high biodiversity at the Kueishan Island fishing ground is under critically fishing pressure. As the slope of the species cumulative curve is still not leveled off in the present sampling and more species can be found by using a different collecting gear. The large crustacean diversity in the Kueishan Island fishing ground should be higher. |