26 Development of the cultivation of Laminaria Saccharina as the extractive inorganic component of an integrated aquaculture system and monitoring of therapeutants and phycotoxins

The development of sustainable integrated aquaculture systems requires combining fed aquaculture (finfish) with extractive inorganic aquaculture (seaweed) and extractive organic aquaculture (shellfish). With the support of AquaNet, the Network of Centers of Excellence in Aquaculture in Canada, we are developing such a system at an industrial pilot scale by co‐cultivating salmon (Salmo salar), kelp (Laminaria saccharina) and blue mussel (Mytilus edulis) at aquaculture sites in the Bay of Fundy, Canada. This presentation will focus on the development of the extractive inorganic component. The entire cycle of rearing Laminaria saccharina has been completed and improved, both in the laboratory and at the integrated sites: release in the laboratory of spores from mature macroscopic sporophytes, seeding of ropes, germination of microscopic gametophytes, sexual maturation of male and female gametophytes, development of zygotes into juvenile sporophytes, which are then transplanted to the sites for rapid grow‐out. Another aspect of the project, food safety monitoring of chemical therapeutants and phycotoxins in mussel and kelp cultured in proximity to salmon, will also be described. The productivity, nutrient absorption capacity, and role of the seaweed component are being analyzed so that its appropriate scale to the other components can be defined in order to develop responsible aquaculture practices in which metabolic/physiological processes of the different co‐cultured organisms counter‐balance each other within acceptable operational limits. Adopting polytrophic strategies will be key to the aquaculture industry to develop its environmentally and economically‐balanced diversification and increase its social acceptability within a broader coastal management framework.     

Identification and molecular characterisation of a fibrinogen binding protein from <Emphasis Type="Italic">Streptococcus iniae</Emphasis>.

Background  

Binding of serum components by surface M-related proteins, encoded by the emm genes, in streptococci constitutes a major virulence factor in this important group of organisms. The present study demonstrates fibrinogen binding by S. iniae, a Lancefield non-typeable pathogen causing devastating fish losses in the aquaculture industry and an opportunistic pathogen of humans, and identifies the proteins involved and their encoding genes.     

Evolution at the tip and base of the X chromosome in an African population of Drosophila melanogaster

Hitchhiking effects of advantageous mutations have been invoked to explain reduced polymorphism in regions of low crossing-over in Drosophila. Besides reducing DNA heterozygosity, hitchhiking effects should produce strong linkage disequilibrium and a frequency spectrum skewed toward an excess of rare polymorphisms (compared to the neutral expectation). We measured DNA polymorphism in a Zimbabwe population of D. melanogaster at three loci, yellow, achaete, and suppressor of forked, located in regions of reduced crossing-over. Similar to previously published surveys of these genomic regions in other populations, we observed low levels of nucleotide variability. However, the frequency spectrum was compatible with a neutral model, and there was abundant evidence for recombination in the history of the yellow and ac genes. Thus, some aspects of the data cannot be accounted for by a simple hitchhiking model. An alternative hypothesis, background selection, might be compatible with the observed patterns of linkage disequilibrium and the frequency spectrum. However, this model cannot account for the observed reduction in nucleotide heterozygosity. Thus, there is currently no satisfactory theoretical model for the data from the tip and base of the X chromosome in D. melanogaster.      

Overturn in a hypertrophic,warm, monomictic impoundment (Hartbeespoort Dam,South Africa)

A major decrease in air temperature with an increase in wind stress created thermal instability resulting in overturn. Surface oxygen values decreased from 12.6 (170% saturation) prior to overturn to 0.4 mg · l^–1 (5.7%) after overturn. Recovery of surface oxygen concentrations to supersaturation took approximately three months. Changes in the nitrogen balance after overturn indicated that extremely high rates of nitrification occurred. Little change in phosphorus concentration was observed. Surface chlorophyll concentrations decreased from 235 to approximately 2 mg · m^–3, resulting in very low primary production values (A_max = 12.4 mg C m^–3 h^–1). Reduced rates of primary production were maintained for several months after overturn, mainly owing to the low ratio of Z_eu/Z_m (0.17). No significant changes occurred in the total bacterial population other than a redistribution within the water column. Significant changes occurred in the distribution and density of the zooplankton population. No fish kills were observed although fish populations were oxygen-stressed.     

A diel study of carbon flow in the pelagic zone of a small lava-lakelet on Marion Island (sub-Antarctic)

Summary Various biotic and abiotic measurements were made over a 48-h period in a small lava-lakelet on the sub-Antarctic Marion Island. Typical oligotrophic conditions prevailed, with low biomass values and rates of productivity for the phytoplankton and bacteria. The bacteria and phytoplankton were subject to heavy zooplankton grazing pressures, which in turn were responsible for rapid carbon turnover rates in the lavalakelet. Diel cycles were observed in bacterial production and algal photosynthesis, with higher rates during the day time. No definite pattern could be seen for the zooplankton, either in terms of filtering rates or migratory activities. Phytoplankton productivity and zooplankton grazing and respiration were responsible for the greatest flow of carbon. Zooplankton occupied the top of the intermediate food chain and dominated the live organic carbon content of the water. A cycling index of 44% indicated a fairly closed system where most components were important in determining the overall structure of the system.     

Tempo and mode of concerted evolution in the L1 repeat family of mice

A 300-bp DNA sequence has been determined for 30 (10 from each of three species of mice) random isolates of a subset of the long interspersed repeat family L1. From these data we conclude that members of the L1 family are evolving in concert at the DNA sequence level in Mus domesticus, Mus caroli, and Mus platythrix. The mechanism responsible for this phenomenon may be either duplicative transposition, gene conversion, or a combination of the two. The amount of intraspecies divergence averages 4.4%, although between species base substitutions accumulate at the rate of approximately 0.85%/Myr to a maximum divergence of 9.1% between M. platythrix and both M. domesticus and M. caroli. Parsimony analysis reveals that the M. platythrix L1 family has evolved into a distinct clade in the 10-12 Myr since M. platythrix last shared a common ancestor with M. domesticus and M. caroli. The parsimony tree also provides a means to derive the average half-life of L1 sequences in the genome. The rates of gain and loss of individual copies of L1 were estimated to be approximately equal, such that approximately one-half of them turn over every 3.3 Myr.      

Polymorphism and divergence at the 5' flanking region of the sex- determining locus, Sry, in mice

We have investigated patterns of evolution in the nonrecombining portion of the Y chromosome in mice by comparing levels of polymorphism within Mus domesticus with levels of divergence between M. domesticus and M. spretus. A 1,277-bp fragment of noncoding sequence flanking the sex determining locus (Sry) was PCR amplified, and 1,063 bases were sequenced and compared among 20 M. domesticus and 1 M. spretus. Two polymorphic base substitutions and two polymorphic insertion/deletion sites were identified within M. domesticus; nucleotide diversity was estimated to be 0.1%. Divergence between M. domesticus and M. spretus for this region (1.9%) was slightly lower than the average divergence of single-copy nuclear DNA for these species. Comparison of levels of polymorphism and divergence at Sry with levels of polymorphism and divergence in the mitochondrial DNA control region provided no evidence of a departure from the expectations of neutral molecular evolution. These findings are consistent with the presumed lack of function for much of the Y chromosome.      

A scaffoldless technique for self-generation of three-dimensional keratinospheroids on liquid crystal surfaces

We describe a new scaffold-free three-dimensional (3D) cell culture model using cholesteryl ester based lyotropic liquid crystal (LC) substrates. Keratinocytes were deposited randomly on the LC surface where they self-assembled into 3D microtissues or keratinospheroids. The cell density required to form spheroids was optimized. We investigated cell viability using dead/live cell assays. The adhesion characteristics of cells within the microtissues were determined using histological sectioning and immunofluorescence staining. Fourier transform infrared spectroscopy (FTIR) was used to characterize the biochemistry of the keratinospheroids. We found that both cells and microtissues could migrate on the LC surface. The viability study indicated approximately 80% viability of cells in the microtissues up to 20 days of culture. Strong intercellular adhesion was observed in the stratification of the multi-layered microspheroids using field emission-scanning electron microscopy (FE-SEM) and histochemical staining. The cytoskeleton and vinculins of the cells in the microtissues were expressed diffusely, but the microtissues were enriched with lipids and nucleic acids, which indicates close resemblance to the conditions in vivo. The basic 3D culture model based on LC may be used for cell and microtissue migration studies in response to cytochemical treatment.     

Seasonal variations of metabolically active bacteria in a hypertrophic lake (Hartbeespoort Dam,South Africa)

The number of metabolically active bacteria was measured with nalidixic acid over two annual cycles at three depths in the epilimnion of hypertrophic Hartbeespoort Dam, South Africa. Concurrent measurements were made of water temperature, DOC, phytoplankton production of dissolved (EDOC) and particulate organic carbon, chlorophyll a and the uptake of glucose (V_max). The objective was to determine the dominant factors correlated to the number of metabolically active bacteria and the relationship between active bacterial numbers and heterotrophic activity.The number of active bacteria was usually highest at the surface and ranged between 0.70 and 6.82 x 10⁶ cells ml^–1. The dominant factors correlated to the number of bacteria at the surface were water temperature (r = 0.65, n = 54, p<0.001), primary production (r = 0.53, n = 51, p<0.001) and EDOC (r = 0.37, n = 45, p = 0.005). Surface V_max for glucose ranged between 0.11 and 4.0 µgC 1^–1 h^–1 and was positively correlated to the number of active bacteria (r = 0.61, n = 53, p<0.001). The specific activity index (10^–12 µgC cell^–1 h^–1) varied between 80 and 2290 at the surface and was most strongly correlated to EDOC (r = 0.70, n = 48, p<0.001). Relationships between active bacterial numbers, water temperature, phytoplankton activity and glucose uptake were also found at two additional depths within the epilimnion. These data suggest that bacterial populations in nutrient enriched lakes contain a large number of metabolically active cells with high individual activity as a result of enhanced phytoplankton growth.