The importance of nutrient ratios in determining elevations in geosmin synthase (geoA) and 2-MIB cyclase (mic) resulting in taste and odour events.

Geosmin synthase (geoA) and 2-MIB cyclase (mic) are key biosynthetic genes responsible for the production of taste and odour (T&O) compounds, geosmin and 2-MIB. These T&O compounds are becoming an increasing global problem for drinking water supplies. It is thought that geosmin and 2-MIB may be linked to, or exacerbated by, a variety of different environmental and nutrient triggers. However, to the best of our knowledge, no studies to date have evaluated the combined effects of seasonality, temperature, and nutrient concentrations on geoA and mic copy numbers in conjunction with T&O concentrations. In this study, environmental triggers behind geosmin and 2-MIB production were investigated in nine reservoirs across Wales, U.K. between July 2019 - August 2020. The abundance of geoA and mic were quantified through quantitative Polymerase Chain Reaction (qPCR). Temporal changes in geoA and geosmin concentrations revealed geoA to be an indicator of monthly geosmin concentrations, although only when geosmin concentrations exceeded 100 ng L-1. Model analysis of a reservoir with elevated geosmin concentrations revealed geoA to be significantly associated with mean temperature (p < 0.001) and the nutrients dissolved reactive silicate (p < 0.001), dissolved iron (p < 0.001), total inorganic nitrogen to phosphorous ratio (TIN:TP) (p < 0.001) and ammonium to nitrate ratio (NH4+:NO3-) (p < 0.001). Sulphate also demonstrated a significant positive linear relationship with geoA (p < 0.001). For mic analysis, NH4+:NO3- was significantly associated with mic (p < 0.05) and an association with dissolved reactive silicate was also observed (p = 0.084). Within this study we also report extreme variance in gene copy numbers between the study seasons. No consistent relationship could be determined for mic copy numbers mL-1 and 2-MIB (ng L-1). The findings from this study indicate that TIN:TP and NH4+:NO3- serve as good predictors for elevated geoA and mic, along with negative linear relationships observed for mean temperature and dissolved reactive silicate. Overall, our findings demonstrate the importance of nutrient concentrations, nutrient ratios and temperature for evidence based predictive capacity of taste and odour events in drinking water reservoirs.

Managing taste and odour metabolite production in drinking water reservoirs: The importance of ammonium as a key nutrient trigger.

Taste and odour (T&O) compounds (most commonly 2-MIB and Geosmin) in drinking water are becoming an increasingly global problem for water management. Here, the trigger(s) for 2-MIB and Geosmin production were investigated in Plas Uchaf reservoir (North Wales, UK) with detailed water sample analysis between 2015 and 2016. Historical abstraction data from this reservoir and 4 reservoirs in Somerset (England, UK) were compared statistically using Self-Organising Map (SOM) analysis. In-reservoir measurements (2015-2016) revealed an 85% reduction in ammonium from the primary external loading source led to lower 2-MIB and Geosmin concentrations, with peak concentrations of 2-MIB declining from 60 to 21  ng l-1 and Geosmin declining from 140 to 18  ng l-1. No other measured water chemistry parameter showed a significant difference between years. The SOM results support the in-reservoir findings, revealing 2-MIB and Geosmin to be associated with high ammonium relative to nitrate for all 5 reservoirs. We conclude that ammonium is key for stimulating cyanobacterial productivity and production of T&O compounds. Whilst it is well understood that adequate availability of phosphorus is required for rapid growth in cyanobacteria, and hence should still be considered in management decisions, we suggest that monitoring sources and concentrations of ammonium is key for managing T&O outbreaks in drinking water reservoirs.

Three decades of longlining in Bimini, Bahamas, reveals long-term trends in lemon shark Negaprion brevirostris (Carcharhinidae) catch per unit effort.

In Bimini, Bahamas, the consistent employment of longlines, beginning in 1982, provided a rare opportunity to explore population trends for large resident sharks. This study assessed three shallow water longline survey periods at this location; 1982-1989, 1992-2002 and 2003-2014, with the aim of determining trends in annual catch per unit effort (CPUE) for an IUCN listed near-threatened species, the lemon shark Negaprion brevirostris. A general additive model (GAM) was used to analyse the non-linear annual CPUE values over the entire 32-year research period. The GAM displayed high variability of annual CPUE, with a peak value of 0·026 N. brevirostris per hook day (hooks day(-1) ) in 2000. The temporal pattern of CPUE indicated an abundance trend with a complete cycle, from trough to trough, occurring over a period of approximately 18 years. The 1982-1989 survey period saw the highest proportion of mature individuals (19·8%) and the smallest average pre-caudal length (LPC ; 124·8 cm). The 1992-2002 survey period had the highest average annual CPUE (0·018 hooks day(-1) ), while the 2003-2014 research period saw largest average LPC size (134·8 cm) and the lowest average CPUE values (0·009 hooks day(-1) ) of the entire research period. The long-term trend identified in this study provides a baseline for future assessment.

Microspatial variability in community structure and photophysiology of calcified macroalgal microbiomes revealed by coupling of hyperspectral and high-resolution fluorescence imaging.

Calcifying coralline macroalgae provide biogenic habitats colonised by epiphytic microalgae that contribute significantly to community productivity. Georeferenced hyperspectral and high-resolution fluorescence imaging were coupled to microspatially mapped community composition and relative biomass of macroalgal host and epiphyte microalgal groups, and their weighted contributions to productivity within host fronds of Corallina officinalis on upper and lower zones of a rocky shore were determined. Lower shore epiphytes were dominated by filamentous diatoms (Bacillariophyta), confined to the apex of the frond structure, which were low light acclimated but retained a high capacity for photoprotective down regulation and contributed up to 51% of total community productivity. Upper shore epiphytes were dominated by green algae (Chlorophyta) and single-celled diatoms (principally Cocconeis spp.), which were high light acclimated but present at far lower relative biomass and contributed negligibly to productivity. The host, C. officinalis was the main primary producer. Variation in light environment resulting from differences in shore height and shading within the host macroalga, likely play a large role in determining patterns in epiphyte community structure, biomass and productivity observed. Additionally, microspatial gradients in photophysiological parameters along the host macroalga likely resulted from age-dependent variation in pigments as well as the gradient in light environment.

Monitoring Migration and Measuring Biomass in Benthic Biofilms: The Effects of Dark/far-red Adaptation and Vertical Migration on Fluorescence Measurements.

Pulse modulated fluorescence has increasingly been used as an ecological tool to examine changes in the vertical distribution of microphytobenthic cells within the upper layers of estuarine sediments (most often using the minimum fluorescence yield F(o)) as well as to indicate the health of the community (using the maximum PS II quantum efficiency F(v)/F(m)). However, the practicalities of in situ measurements, often dictates that short dark adaptation periods must be used ( approximately 15 min). The use of far-red light as an alternative to dark adaptation was investigated in natural migratory microphytobenthic biofilms and artificial non-migratory biofilms. Prolonged periods of darkness ( approximately 24 h) were not adequate to achieve 'true' measurements of F(o) and F(v)/F(m), which require complete oxidation of Q(A) and full reversal of non-photochemical quenching (NPQ). In some instances, stable values were only achieved using far-red light. Prolonged exposure to dark/far-red light led to a downwards migration of cells in natural assemblages, as seen by a reduction in both F(o) and the maximum fluorescence yield (F(m)). In non-migratory biofilms, F(m) increased in the dark and far-red treatments, indicating a reversal of NPQ, whereas F(o) decreased in far-red light but increased in the dark. It is suggested that far-red light and darkness differentially affected the balance between NPQ reversal and Q(A) oxidation that lead to the measured F(o) yield. The use of far-red light as an alternative to dark adaptation is discussed and the implications of short (e.g., 15 min) dark adaptation times used in situ are discussed with reference to the vertical migration of cells within sediment biofilms.

Reduction in photosynthetic efficiency of Cladophora glomerata, induced by overlying canopies of Lemna spp.

The duckweeds Lemna minor L. and L. minuscula Herter reduced PSII quantum efficiency (F'q/F'm) of the filamentous green alga Cladophora glomerata Kützing by up to 42% over seven days when floating above mats of C. glomerata in containers. Dissolved oxygen (DO) increased by 23% at 30 degrees C in containers with C. glomerata over controls. But when the water surface in the containers was covered with Lemna spp. floating above C. glomerata, DO was 83% lower at 30 degrees C over seven days than in control samples with no duckweed or alga. Dissolved oxygen was lower beneath a thick mat (1 cm) of either Lemna spp. covering the surface than under a thin layer (single-frond canopy). PAM fluorimetry showed that maximum PSII efficiency (Fv/Fm) of C. glomerata in containers was reduced under a canopy of L. minor by 17% over seven days, and under L. minuscula by 22%. F'q/F'm of C. glomerata in containers exposed to 51 micromol m(-2) s(-1) PPFD decreased under a canopy of L. minor by 16% over seven days, and under L. minuscula by 19% compared to controls. When light response curves were compared, F'q/F'm was significantly reduced under canopies of L. minor at the highest temperatures tested (28 degrees C and 30 degrees C). L. minor significantly reduced relative electron transport rate (rel. ETR) of the controls by up to 71% at 30 degrees C. Relative electron transport rate did not reach light saturation point (Esat) except at 28 degrees and 30 degrees C under mats of L. minor. Whereas the highest rate of production (rel. ETRmax) and Esat increased with temperature in controls, under a canopy of Lemna, decreases were observed. It is suggested that, during periods of high summer temperature and irradiance, shading inhibits oxygenic photosynthesis in mats of C. glomerata beneath canopies of Lenma spp. This results in less oxygen being produced by the C. glomerata (oxygen produced by Lemna spp. is not released into the water), and this may further inhibit the C. glomerata by limiting oxygen-dependent electron transport and/or photorespiration. This feedback loop could lead to the eventual senescence of the C. glomerata. The combination of low oxygen, high temperature and stressed filamentous algae, particularly in slow or standing water, may help to explain sudden collapses in DO concentration, with detrimental effects on water quality downstream.

The potential for phosphorus release across the sediment-water interface in an eutrophic reservoir dosed with ferric sulphate.

Alton Water, Suffolk, UK is a pumped storage reservoir that has a history of cyanobacterial blooms. Dosing of the input water with ferric sulphate to control external phosphorus loading has occurred since 1983. A detailed study of the sediment chemistry of the site was carried out between May 1995 and July 1997. Sequential phosphorus fraction analysis indicated a decrease along the length of the reservoir in sediment labile phosphorus content from 0.62 to 0.08 mg P g-1 dw and iron-bound phosphorus content from 3.22 to 0.46 mg P g-1 dw. These gradients positively correlated with water column chlorophyll a concentrations reported in a parallel study. Labile and iron-bound sediment phosphorus contents were in a dynamic equilibrium due to diffusional release, contributing to internal loading to the water column. Equilibrium phosphorus concentrations (EPC) determined from phosphorus adsorption capacity (PAC) experiments were lower inside the bunded region (0.01-0.03 mg P-PO4 l-1) where iron content was greatest compared to outside the bund (0.15-0.20 mg P-PO4 l-1) suggesting greater potential for diffusional release of phosphorus at the latter site. PAC experiments indicated that anaerobic and pH-mediated loadings were of less importance than diffusional release, although the latter may have contributed to internal loading in the main reservoir. Sulphate concentrations may act to increase the potential for anaerobic internal loading near to the pumped input in microstratified sediment. Sediment iron content decreased from 250 +/- 13.1 to 51 +/- 4.0 mg Fe g-1 dw across the line of a constructed bund at the north-west end near to the pumped input, which indicated successful control of dispersal of the fine ferric floc. The management implications with regard to phosphorus loadings indicated by these results are discussed.

Plasma membrane vesiculation in 3T3 and SV3T3 cells. I. Morphological and biochemical characterization.

3T3 and SV3T3 mouse embryo cells and a variety of other monolayer cell lines can be induced to form and shed plasma membrane vesicles by exposure to sulphydryl blocking agents including formaldehyde and N-ethyl malemide. Morphological studies show that multiple vesicles are formed and released from individual cells and that the vesicle membrane is continuous with the plasma membrane of the cell. Vesicles measure from o.1 to 15 micrometer in diameter and are free of detectable contamination with cytoplasmic membranes and organelles. Vesicles also show a 10-fold enrichment in the plasma membrane marker enzyme 5'-nucleotidase and are devoid of detectable NADH-cytochrome C reductase and succinic dehydrogenase activity which are marker enzymes for endoplasmic reticulum and mitochondria, respectively. Vesicles have a high cholesterol: phospholipid ratio and show enrichment in sphingomyelin content. They contain receptors for Con A and WGA, approximately 20 size class polypeptides and intramembranous particles. These results suggest that vesicles are derived from and have the general characteristics of plasma membranes.

Differences in the phospholipid, cholesterol, and fatty acyl composition of 3T3 and SV3T3 plasma membranes.

An analysis of the phospholipid, cholesterol, and phospholipid fatty acyl composition of isolated plasma membranes of 3T3 and SV3T3 mouse mebryo cells has been performed. The results show that the plasma membrane of SV3T3 cells contain relatively less phosphatidylethanolamine and sphingomyelin and more cholesterol than 3T3 plasma membranes. The fatty acyl composition of individual phospholipid classes as determined by gas liquid chromatography also showed differences between 3T3 and SV3T3 plasma membranes. The plasma membranes of SV40 transformed 3T3 cells contain: (a) a higher percentage of 18:1 and less 20:3 and 20:4 in phosphatidylethanolamine; (b) a higher percentage of 18:1 in phosphatidylserine; and (c) a higher percentage of 18:2 and 20:4 in phosphatidylinositol.

Plasma membrane phospholipid, cholesterol and fatty acyl composition of differentiated and undifferentiated L6 myoblasts.

The lipid composition of plasma membranes isolated from differentialted and undifferentiated L6 myoblasts have been compared. In general, the plasma membranes of differentiated L6 myoblasts have a higher cholesterol to phospholipid molar ratio than plasma membranes of undifferentiated cells. Differentiated L6 myoblasts have increased relative amounts of phosphatidylethanolamine and phosphatidylcholine ine in their plasma membrane and a decreased relative amount of sphingomyelin when compared with the plasma membranes of undifferentiated myoblasts. In addition, preliminary results show that differentiated L6 myoblasts plasma membrane phospholipid shows differences in the fatty acyl composition, specifically there appears to be relatively more 17:0 and 24:1 and less 16:1 and 18:1 than in plasma membrane phospholipids of undifferentiated L6 myoblasts. These observations indicate that significant changes in plasma membrane lipid composition occur during myoblast differentiation. The role that changes in lipid composition play in control of cellular differentiation, however, remains to be elucidated.

Major lipid classes in plasma membrane isolated from liver of rats fed a hepatocarcinogen.

More phosphatidylethanolamine and less phosphatidylinositol were present in the lipid of plasma membrane isolated from the liver of rats fed a diet containing the hepatocarcinogen, N-2-fluorenylacetamide than were present in the lipid of plasma membrane isolated from the liver of rats fed the basal diet. Phosphatidylcholine, phosphatidylethanolamine, and sphingomyelin from the former membranes had relative amounts of 18 : 1 in their fatty acyl profiles that were 1.5--1.7 times the relative amount of 18 : 1 in the same phospholipid from the latter membranes. Furthermore, the former membranes contained 1.3 times more cholesterol and 1.35 times more sphingomyelin than the latter membrames.