Reconciling Coulter Counter and laser diffraction particle size analysis for aquaculture monitoring.

The disaggregated inorganic grain size (DIGS) of bottom sediment analyzed with a Coulter Counter (CC) has been used to show that the fraction of sediment deposited in flocs (floc fraction) increased in both the near and far field after the introduction of open cage salmon aquaculture, altering benthic habitat and species composition. As a result, DIGS was identified as a potential indicator of regional environmental changes due to aquaculture. Laser diffraction is an attractive alternative to the CC because of its greater efficiency and larger size range. To determine if a laser diffraction instrument, Beckman-Coulter LS 13 320 (LS), could replace the CC within a Canadian national aquaculture monitoring program, the DIGS of 581 samples from five different regions in eastern Canada were analyzed with an LS and a CC. Results show that the LS could not be used to calculate floc fraction. Instead, % sortable silt and the volume % of inorganic particles < 16 µm were evaluated as alternative proxies for fine sediment properties. LS and CC values for these parameters were correlated, but they were significantly different and the relationship between the instruments was dependent on the area sampled. The LS did not capture variations between areas seen in the CC DIGS data. Where the DIGS from the CC found no sorting in the finest size classes, all the LS samples had similar size distributions characterized by smooth modal peaks. The LS and CC both return values that can be used to monitor changes in the deposition of fine-grained sediment, but the LS cannot determine changes in floc deposition and caution is required if comparing different sedimentary environments.

Relationship between in feed drugs, antibiotics and organic enrichment in marine sediments at Canadian Atlantic salmon aquaculture sites.

The presence of in-feed anti-sea lice drugs and their relationship with organic enrichment is poorly understood in sediment surrounding salmon farms. Using data from an aquaculture monitoring program (2018-2020), we describe this relationship at ten sites in four Canadian provinces. Three anti-sea lice pesticides (lufenuron, teflubenzuron, emamectin benzoate and metabolite desmethyl emamectin benzoate), and one antibiotic (oxytetracycline) were detected. Concentrations were often below limits of quantification. Values are also lower than those reported in other aquaculture salmon-producing countries. Highest concentrations, along with organic enrichment, were observed ~200 m of cages with lower concentrations detected up to 1.5 km away. Most samples had at least two drugs present: 75.2 % (British Columbia), 91.4 % (Newfoundland), and 54.8 % (New Brunswick/Nova Scotia) highlighting the potential for cumulative effects. Emamectin benzoate and oxytetracycline were detected four and three years respectively after last known treatments, demonstrating the need for research on overall persistence of compounds.

Contaminants at the sediment-water interface: implications for environmental impact assessment and effects monitoring.

Many contaminants in aquatic environments are associated with loosely packed aggregates of particulate material called flocs. Flocculation allows contaminants to accumulate at the sediment-water interface and it packages them in a form that is readily available for ingestion by filter feeding organisms. Unfortunately, most samplers being used for environmental assessment and monitoring suspend this material on impact and fail to sample this critical component of the seabed. In this study we use a slo-corer to collect seabed samples with an undisturbed surface layer and a Gust microcosm erosion chamber to erode the surface of the cores at increasing shear stresses. Results from two different sites, one impacted by tailings from historic gold mining and the other by open-pen salmon aquaculture, showed the levels of metals suspended at stresses below 0.24 Pa were greater than in the underlying sediment. Sampling this highly mobile surface layer is critical for determining the total contaminant load in bottom sediments and, more importantly, this layer represents the most readily available material for suspension. The loss of this layer during sampling could lead to inaccurate measurements of contaminant levels during environmental assessment and effects monitoring. A re-evaluation of the ISO standard for bottom sediment sampling is recommended.

The effect of nitrogen and carbon sources on proteinase production by Pseudomonas fluorescens.

Some factors influencing the production of an extracellular proteinase by Pseudomonas fluorescens NCDO 2085 were studied. Proteinase production was optimal at 20 degrees C and pH 6.9 in static culture when calcium was included in the medium. Proteinase was not detectable in basal medium but could be induced by organic nitrogen compounds. The proteinase was produced in the exponential phase of growth on protein substrates but not until early stationary phase during growth on amino acids. The organism did not utilize lactose, the most abundant carbohydrate in milk. Citrate was readily utilized as an energy source but had a strong repressive effect on proteinase production. A medium containing sodium caseinate and pyruvate supported good growth and enzyme production. All the amino acids utilized as a sole carbon source, with the exception of serine, could induce proteinase production. Asparagine was the most effective amino acid inducer. Particular combinations of amino acids could induce or repress proteinase production. The regulation of proteinase production by Ps. fluorescens NCDO 2085 appears to be based on a balance between induction by low concentrations of low molecular weight degradation products and sensitivity to end product catabolite repression. The results suggest that the function of the proteinase is to ensure a supply of carbon rather than amino acids for protein synthesis.

Purification and characterization of the extracellular proteinase of Pseudomonas fluorescens NCDO 2085.

Pseudomonas fluorescens NCDO 2085 produced a single heat-stable extracellular proteinase in Na caseinate medium at 20 degrees C and pH 7.0. The proteinase was purified to electrophoretic homogeneity using chromatofocusing, gel filtration and ion-exchange chromatography. The purification procedure resulted in a 158-fold increase in the specific activity and a yield of 3.5% of the original activity. The enzyme is a metalloproteinase containing Zn and Ca, with an isoelectric point at 5.40 +/- 0.05 and a mol. wt of 40 200 +/- 2100. It is heat-stable having D-values at 74 and 140 degrees C of 1.6 and 1.0 min respectively; 40 and 70% of the original activity remained after HTST (74 degrees C/17 s) and ultra high temperature (140 degrees C/4 s) treatments respectively. The amino acid composition of the proteinase was determined and compared with those from other Pseudomonas spp.

Comparative peptide specificity of cell wall, membrane and intracellular peptidases of group N streptococci.

Solubilized cell walls of group N streptococci contain two electrophoretically distinct peptidases, one of which hydrolysed trileucine only, while the second hydrolysed a wide range of di- and tripeptides. Neither enzyme possessed leucine aminopeptidase or endopeptidase activity. Four and three peptidases, respectively, were separated in intracellular extracts of Streptococcus lactis subsp. lactis and Strep. lactis subsp. cremoris produced by osmotic lysis of spheroplasts. In contrast with the cell-wall extracts, two of the peptidases had broad specificites, though only one of these hydrolysed trileucine. Purified membranes of Strep. lactis subsp. lactis contained only one electrophoretically distinct peptidase of very narrow specificity. There were small differences between the numbers of peptides hydrolysed by cell wall preparations from milk-grown or broth-grown cells.

Effect of chest wall vibrations on pulmonary function in chronic bronchitis.

Manual chest wall vibration is one physiotherapeutic technique frequently employed in the management of respiratory disease. A clinical study was undertaken to examine the effects of manual chest wall vibrations on pulmonary function and arterial oxygen saturation in patients with chronic bronchitis. Twelve patients participated in a three-day experimental design where the factors of three different days and three different treatments were randomized and balanced. On one day, deep-breathing exercises were given; on another, deep-breathing exercises with vibrations; and on the remaining day, no treatment was given. Lung volumes were measured before and after each maneuver, and arterial oxygen saturation was monitored continuously. There was a significant decrease in the expiratory reserve volume (ERV) immediately following the deep-breathing exercises alone, which remained constant after the 15-minute rest period (p = 0.032). The remaining outcome parameters do not appear to be significantly affected. Chest wall vibrations do not decrease the ERV in patients with chronic bronchitis.

Proteolytic systems in lactic acid bacteria.

The proteolytic systems of lactic acid bacteria are important as a means of making protein and peptide N available for growth and as part of the curing or maturation processes which give foods their characteristic rheological and organoleptic properties. The proteolytic systems of lactic acid bacteria are described in relation to their growth and their functions in protein-rich foods. Their role in the manufacture of milk products is discussed.

Peptide utilization by group N streptococci.

The rate of glycylleucine uptake by Group N streptococci varied widely. One strain of Streptococcus cremoris did not transport the dipeptide or utilize tripeptides. In peptide-utilizing strains, amino acid, dipeptide and tripeptide transport were distinct, although dipeptides inhibited tripeptide utilization. Specificity determinants for peptide transport and utilization were similar to those reported in Gram-negative bacteria. Peptide utilization in S. lactis was not completely dependent on the transport of intact peptides.

Influence of the heat treatment of human milk on some of its protective constituents.

Human milk was subjected to heat treatments of graded severity and examined for its content of immunoglobulins, lactoferrin, lysozyme, vitamin B12-and folate-binder proteins, and lactoperoxidase. Holder pasteurization (62.5degrees C 30 minutes) reduced the IgA titer by 20%, and destroyed the small content of IgM and most of the lactoferrin. Lysozyme was stable to this treatment, but with an increase in temperature there was progressive destruction, to near 100% at 100degrees C. The same was broadly true of the capacity of milk to bind folic acid and potect it against bacterial uptake; with vitamin B12 the binder was more labile at 75degrees C than at 100degrees C. The milk contained no detectable lactoperoxidase.