Effect of Hydrographic Variability on the Distribution of Microbial Communities in Taiwan Strait in Winter

This study investigated the spatial variation in the components of a microbial food web (viruses, picoplankton, nanoflagellates, and ciliates) in different hydrographic environments in the Taiwan Strait during winter. Water temperature and salinity varied spatially, with lower temperatures (15.3–22.8 °C) and salinities (32.2–33.4 psu) in the northern part of the Taiwan Strait, largely affected by runoff from the coast of China. Concentrations of nutrients and Chl a were significantly higher in the northern part than that in the southern part of the study area. Synechococcus spp., nanoflagellate, and ciliate abundance also varied significantly, with the northern strait having higher abundances of these communities. In contrast, a higher abundance of bacteria was found in the southern part of the Taiwan Strait. The results of this study, which describes two different ecosystems in the Taiwan Strait, suggest that during winter, a “viral loop” might play an important role in controlling bacterial production in the southern part of the Taiwan Strait, while nanofalgellate grazing of picophytoplankton may contribute mainly to the flux of energy in the northern part.

Sourcing the iron in the naturally fertilised bloom around the Kerguelen Plateau: particulate trace metal dynamics

The KEOPS2 project aims to elucidate the role of natural Fe fertilisation on biogeochemical cycles and ecosystem functioning, including quantifying the sources and processes by which iron is delivered in the vicinity of the Kerguelen Archipelago, Southern Ocean. The KEOPS2 process study used an upstream high-nutrient, low-chlorophyll (HNLC), deep water (2500 m), reference station to compare with a shallow (500 m), strongly fertilised plateau station and continued the observations to a downstream, bathymetrically trapped recirculation of the Polar Front where eddies commonly form and persist for hundreds of kilometres into the Southern Ocean. Over the Kerguelen Plateau, mean particulate (1–53 μm) Fe and Al concentrations (pFe = 13.4 nM, pAl = 25.2 nM) were more than 20-fold higher than at an offshore (lower-productivity) reference station (pFe = 0.53 nM, pAl = 0.83 nM). In comparison, over the plateau dissolved Fe levels were only elevated by a factor of ~ 2. Over the Kerguelen Plateau, ratios of pMn / pAl and pFe / pAl resemble basalt, likely originating from glacial/fluvial inputs into shallow coastal waters. In downstream, offshore deep-waters, higher pFe / pAl, and pMn / pAl ratios were observed, suggesting loss of lithogenic material accompanied by retention of pFe and pMn. Biological uptake of dissolved Fe and Mn and conversion into the biogenic particulate fraction or aggregation of particulate metals onto bioaggregates also increased these ratios further in surface waters as the bloom developed within the recirculation structure. While resuspension of shelf sediments is likely to be one of the important mechanisms of Fe fertilisation over the plateau, fluvial and glacial sources appear to be important to areas downstream of the island. Vertical profiles within an offshore recirculation feature associated with the Polar Front show pFe and pMn levels that were 6-fold and 3.5-fold lower, respectively, than over the plateau in surface waters, though still 3.6-fold and 1.7-fold higher respectively than the reference station. Within the recirculation feature, strong depletions of pFe and pMn were observed in the remnant winter water (temperature-minimum) layer near 175 m, with higher values above and below this depth. The correspondence between the pFe minima and the winter water temperature minima implies a seasonal cycle is involved in the supply of pFe into the fertilised region. This observed association is indicative of reduced supply in winter, which is counterintuitive if sediment resuspension and entrainment within the mixed layer is the primary fertilising mechanism to the downstream recirculation structure. Therefore, we hypothesise that lateral transport of pFe from shallow coastal waters is strong in spring, associated with snow melt and increased runoff due to rainfall, drawdown through summer and reduced supply in winter when snowfall and freezing conditions predominate in the Kerguelen region.

Sourcing the iron in the naturally-fertilised bloom around the Kerguelen Plateau: particulate trace metal dynamics

The KEOPS2 project aims to elucidate the role of natural Fe fertilisation on biogeochemical cycles and ecosystem functioning, including quantifying the sources and processes by which iron is delivered in the vicinity of the Kerguelen Archipelago, Southern Ocean. The KEOPS2 process study used an upstream HNLC, deep water (2500 m), reference station to compare with a shallow (500 m), strongly fertilised plateau station and continued the observations to a downstream, bathymetrically trapped recirculation of the Polar Front where eddies commonly form and persist for hundreds of kilometres into the Southern Ocean. Over the Kerguelen Plateau, mean particulate (1–53 μm) Fe and Al concentrations (pFe = 13.4 nM, pAl = 25.2 nM) were more than 20-fold higher than at an offshore (lower-productivity) reference station (pFe = 0.53 nM, pAl = 0.83 nM). In comparison, over the plateau dissolved Fe levels were only elevated by a factor of ∼2. Over the Kerguelen Plateau, ratios of pMn/pAl and pFe/pAl resemble basalt, likely originating from glacial/fluvial inputs into shallow coastal waters. In downstream, offshore deep-waters, higher pFe/pAl, and pMn/pAl ratios were observed, suggesting loss of lithogenic material accompanied by retention of pFe and pMn. Biological uptake of dissolved Fe and Mn and conversion into the biogenic particulate fraction or aggregation of particulate metals onto bioaggregates also increased these ratios further in surface waters as the bloom developed within the recirculation structure. While resuspension of shelf sediments is likely to be one of the important mechanisms of Fe fertilisation over the plateau, fluvial and glacial sources appear to be important to areas downstream of the island. Vertical profiles within an offshore recirculation feature associated with the Polar Front show pFe and pMn levels that were 6-fold and 3.5-fold lower respectively than over the plateau in surface waters, though still 3.6-fold and 1.7-fold higher respectively than the reference station. Within the recirculation feature, strong depletions of pFe and pMn were observed in the remnant winter water (temperature-minimum) layer near 175 m, with higher values above and below this depth. The correspondence between the pFe minima and the winter water temperature minima implies a seasonal cycle is involved in the supply of pFe into the fertilized region. This observed association is indicative of reduced supply in winter, which is counterintuitive if sediment resuspension and entrainment within the mixed layer is the primary fertilising mechanism to the downstream recirculation structure. Therefore, we hypothesise that lateral transport of pFe from shallow coastal waters is strong in spring, associated with snow melt and increased runoff due to rainfall, drawdown through summer and reduced supply in winter when snowfall and freezing conditions predominate in the Kerguelen region.

age and growth in a temperate euryhaline notothenioid, eleginops maclovinus from the falkland islands

falkland islands' mullet (eleginops maclovinus) were aged successfully using whole sagittal otoliths from 1403 individuals. marginal increment analysis indicated that one opaque and one translucent zone were laid down annually. unvalidated daily ring counts confirmed what was thought to be the first translucent zone. the translucent zones were found to form earlier in juveniles than in adults. juveniles over winter in the creeks and inlets whereas adults are more common in deeper inshore waters where there is a one month lag in the minimum winter water-temperature. the maximum observed age was found to be 11 years. the calculated von bertalanffy growth model (lt=124.41(1−e−0.14/year(t-0.01years))) showed that e. maclovinus is a fast-growing fish, growing on average 10.2 cm/year for the first six years of its life.

Effects of Elevated Winter Temperature on Seawater Adaptability, Sexual Rematuration, and Downstream Migratory Behaviour in Mature Male Atlantic Salmon Parr (Salmo salar)

In experiments with two different salmon (Salmo salar) stocks, elevated winter temperatures (Celsius) 4–9° above the ambient increased the degree of testicular resorption in previously mature male Atlantic salmon parr. Two-summer-old mature male parr maintained at a temperature 9° over the ambient for 5 mo (January–May) showed an increase in hypoosmoregulatory ability when challenged in seawater at the time of smoltification whereas parr kept at elevated temperature for various 2-mo periods (January–February, February–March, or March–April) failed to show this improvement. Furthermore, previously mature males kept at an elevated winter water temperature for either 2 or 5 mo showed a lower incidence of sexual rematuration, and consequently a higher mean growth rate, after one summer in sea pens. A river release experiment showed that rearing previously mature males at 4–7° above the ambient water temperature from December to April increased the number of downstream migrating fish to a level similar to that of immature smolts. We suggest the use of a simple method for enhancing the potential yield of ranched and cultured salmon from early maturing males by removing them from the stock population and rearing them over winter in heated water.

Finite element prediction of temperature gradients in walls of cylindrical concrete storage structures

Aboveground concrete cylindrical storage tanks must be designed for temperature differences between inside and outside faces of the wall. The stresses in the cylinder wall are a linear function of the temperature difference. A number of transient heat transfer finite element analyses were carried out to determine reasonable design values for this temperature difference. Extreme summer and winter conditions for southern Ontario were assumed in the analyses. It was found that for water stand-pipes supplied by groundwater the temperature difference can be as high as 25 °C, based on a summer water temperature of 10 °C. The maximum winter temperature difference was also 25 °C, based on a winter water temperature of 5 °C. For farm tower silos, a design temperature difference of 15 °C is probably more appropriate. Storage structures for other liquids can be judged if the temperature of the contained liquid is known. Key words: standpipes, structural design, temperature load, water reservoir, finite element prediction.