The present study used beam trawl net to collect crabs by Ocean Researcher III at four sites, Wanggong, Taisi, Cigu and Jiading, in western waters off Taiwan from July 2006 to October 2008. In total, 3205 crabs were obtained, including 11 families, 22 genus, 41 species and 6 unknown species. Among these families, Portunidae contained the most species (21 species, 45¢H), followed by families Majidae (4 species, 9%), Leucosiidae (3 species, 6%) and Dorippidae (3 species, 6%). Six dominant species were Portunus hastatoides (60.1%), Portunus argentatus (13.7%), Portunus sanguinolentus (7.2%), Matuta victor (3.8%), Charybdis truncata (3.0%) and Portunus pelagicus (2.1%) contributing 89.8% of the total catch. P. sanguinolentus (35.6%), P. pelagicus (16.3%), P. hastatoides (12.0%), Calappa philargius (11.5%), P. argentatus (8.0%) and Charybdis feriatus (3.1 %) were the six dominant species (86.5%) by biomass. Spatial distributions of the benthic crabs by number were significantly different. P. argentatus was the most dominant species in Cigu, whereas in the other three stations was P. hastatoide. Among the six species, P. sanguinolentus, P. pelagicus and C. feriatus are the most important species in terms of economic value. The former appeared in large numbers in Jiading and composed 35.6% in weight of the total catch from all sites, while the latter frequently occurred in the other three sites and contributed 16.3% to the overall sample weight. Moreover, P. sanguinolentus was the dominant species in terms of weight in Jiading, but the rest of three sites dominated by P. pelagicus. P. hastatoides occurred mostly in the substrate with very fine sand. P. sanguinolentus increased in number and weight with decreasing of salinity and water depth. P. argentatus had a narrowest optimum temperature range from 24.3 to 28.3¢J.

This thesis describes the results of an investigation into the population genetic structure of the blue swimmer crab, Portunus pelagicus, in Australian waters. P. pelagicus is an Indo-West Pacific species, with adults and juveniles that inhabit sheltered benthic coastal environments and a planktonic phase (of modest duration) in its life cycle. The investigation was done by examining the patterns of variation at six microsatellite loci and in a 342 bp portion of the cytochrome oxidase subunit I (COI) gene in the mitochondrial DNA in samples of Portunus pelagicus from a total of 16 different assemblages/waterbodies. Overall, the samples were collected from throughout the geographical range of this species in Australian waters, i.e. from the western seaboard, from the eastern seaboard, from Darwin on the north coast and from South Australia on the south coast. The samples sizes ranged from 4 to 57 individuals, depending on the sample and the genetic assay. The population genetic structure of P. pelagicus was analysed from both a traditional population structure perspective and from a phylogeographical and historical demography perspective. The traditional assessment of the population genetic structure of Portunus pelagicus indicates that this species exhibits a significant amount of genetic heterogeneity in Australian waters (e.g. FST for microsatellite data = 0.098; ¥èST for COI data = 0.375 and ¥ÕST for COI data = 0.492). This assessment also indicates that P. pelagicus exhibits varying degrees of genetic heterogeneity within and between geographical regions in Australian waters, as follows. (1) The genetic compositions of the samples from the different coastlines (i.e. north, south, east and west) invariably showed statistically significant differences for at least two microsatellite loci, although the differences between the samples from the eastern seaboard, Darwin and those from the western seaboard to the north of Port Denison were not as great as those within the western seaboard samples or within South Australian samples. (2) The genetic compositions of the samples from the assemblages on the eastern seaboard of Australia, which ranged from Mackay (21¨¬06¡ÇS) to Port Stephens (32¡Æ40¡ÇS), were essentially homogeneous. (3) The samples from the assemblages on the western seaboard of Australia, which ranged from Broome (17¡Æ58¡ÇS) to Geographe Bay (33¡Æ35¡ÇS), exhibited significant levels of genetic heterogeneity. Furthermore, those from south of Port Denison formed a highly distinctive (but not invariant) group compared to those from elsewhere. (4) The samples from South Australia were also highly genetically distinctive compared to those from elsewhere, although they also showed significant heterogeneity amongst themselves. The above findings were more or less suggested by both the microsatellite and COI markers, although the former generally provided a higher resolution picture of the population structure of P. pelagicus than did the latter. The main findings of the investigation into the phylogeography and recent demographic history of Portunus pelagicus in Australian waters were as follows. (1) A phylogeny constructed from COI sequence variation was shallow, with the lineages showing varied geographical distributions. (2) The results of a nested clade analysis of this variation indicate that range expansion has been a predominant influence on the historical demography of P. pelagicus in Australian waters. (3) The samples from the assemblages on the western seaboard to the south of Port Denison contained low levels of genetic diversity, a sub-set of the diversity present in the samples from lower latitude sites on the western seaboard, and microsatellite-based evidence of having coming from assemblages that have undergone a bottleneck (or founder effect) followed by an expansion in size. (4) The samples from the assemblages in South Australia contained low levels of genetic diversity, phylogenetic affinities with samples from the eastern seaboard, and microsatellite-based evidence of having coming from assemblages that have undergone a bottleneck (or founder effect) followed by an expansion in size. The two major interpretations to stem from the results of this investigation are as follows. (1) Overall, Portunus pelagicus has undergone a recent (in an evolutionary sense) range expansion, from a single source, within Australian waters. At a finer-scale, this species appears to have colonised south-western Australia from a lower latitude site(s) on the western seaboard and probably colonised South Australia from the southern margins of its range on the eastern seaboard. Regardless, there has been limited penetrance of genetic variation into temperate waters on the western seaboard and into South Australia, presumably due one or more of the barriers to gene flow listed below. (2) P. pelagicus experiences significant restrictions to gene flow within its present-day geographical range in Australian waters due to (i) geographic distance per se; (ii) discontinuities in the distribution of the sheltered coastal environments; (iii) hydrological barriers to dispersal and (iv) possibly low temperatures in the temperature margins of the range.

Phytoplankton growth is iron limited in at least 20% of the world’s oceans. Iron is an important nutrient required to synthesise enzymes necessary for photosynthesis, respiration, and nitrogen assimilation. Due to its low solubility in seawater, iron limitation of phytoplankton production has been the focus of much recent research. These organisms secrete ligands in order to solubilise the available iron, but not all of the iron dissolved in seawater is biologically available. In this study a molecular based approach was employed to investigate the acclimation of the marine haptophyte Coccolithus pelagicus to iron limitation. Using two dimensional electrophoresis, subtractive cDNA hybridisation, and RT real time PCR, changes in the proteome and in gene expression were examined. Iron limited cells were characterised by slower specific growth rates, lower chlorophyll a concentrations per unit biomass and less extensive calcification relative to iron replete cells. Addition of iron to iron limited cultures resulted in increased specific growth rates and increased chlorophyll a concentration per unit biomass. A subtracted cDNA library revealed seventeen identifiable sequences of which photosystem I protein E (PsaE), a fucoxanthin binding protein transcript, two chlorophyll binding proteins and a predicted membrane protein were shown to be up-regulated in iron-limited cells to varying extents. Two dimensional SDS PAGE revealed 11 differentially expressed proteins in iron limited cells and 1 highly expressed protein exclusive to iron replete cells. The potential utility of each of these as biomarkers of iron-limitation/iron sufficiency for natural populations of coccolithophorids like Coccolithus pelagicus is discussed.