Nested spatial and temporal modeling of environmental conditions associated with genetic markers of Vibrio parahaemolyticus in Washington state Pacific oysters

The Pacific Northwest (PNW) is one of the largest commercial harvesting areas for Pacific oysters (Crassostrea gigas) in the United States. Vibrio parahaemolyticus, a bacterium naturally present in estuarine waters, accumulates in shellfish and is a major cause of seafood-borne illness. Growers, consumers, and public-health officials have raised concerns about rising vibriosis cases in the region. V. parahaemolyticus genetic markers (tlh, tdh, trh) were estimated using an MPN-PCR technique in Washington State Pacific oysters regularly sampled between May and October from 2005 to 2019 (N=2,836); environmental conditions were also measured at each sampling event. Multilevel mixed-effects regression models were used to assess relationships between environmental measures and genetic markers as well as genetic marker ratios (trh:tlh, tdh:tlh, and tdh:trh), accounting for variation across space and time. Spatial and temporal dependence were also accounted for in the model structure. Model fit improved when including environmental measures from previous weeks (1-week lag for air temperature, 3-week lag for salinity). Positive associations were found between tlh and surface water temperature, specifically between 15°C and 26°C, and between trh and surface water temperature up to 26°C. tlh and trh were negatively associated with 3-week lagged salinity in the most saline waters (> 27 ppt). There was also a positive relationship between tissue temperature and tdh, but only above 20°C. The tdh:tlh ratio displayed analogous inverted non-linear relationships as tlh. The non-linear associations found between the genetic targets and environmental measures demonstrate the complex habitat suitability of V. parahaemolyticus. Additional associations with both spatial and temporal variables also suggest there are influential unmeasured environmental conditions that could further explain bacterium variability. Overall, these findings confirm previous ecological risk factors for vibriosis in Washington State, while also identifying new associations between lagged temporal effects and pathogenic markers of V. parahaemolyticus.

Compound hot temperature and high chlorophyll extreme events in global lakes

An emerging concern for lake ecosystems is the occurrence of compound extreme events i.e., situations where multiple within-lake extremes occur simultaneously. Of particular concern are the co-occurrence of lake heatwaves (anomalously warm temperatures) and high chlorophyll-a extremes, two important variables that influence the functioning of aquatic ecosystems. Here, using satellite observations, we provide the first assessment of univariate and compound extreme events in lakes worldwide. Our analysis suggests that the intensity of lake heatwaves and high chlorophyll-a extremes differ across lakes and are influenced primarily by the annual range in surface water temperature and chlorophyll-a concentrations. The intensity of lake heatwaves is even greater in smaller lakes and in those that are shallow and experience cooler average temperatures. Our analysis also suggests that, in most of the studied lakes, compound extremes occur more often than would be assumed from the product of their independent probabilities. We anticipate compound extreme events to have more severe impacts on lake ecosystems than those previously reported due to the occurrence of univariate extremes.

Does glacial retreat impact benthic chironomid communities? A case study from Rocky Mountain National Park, Colorado

The aim of this study was to determine which environmental variables are responsible for modern benthic chironomid distributions in a glacial setting. The chironomid communities from nine alpine lakes were assessed, and forty-three individual taxa were extracted and identified. Surface water temperature and nitrate were strongly and negatively correlated (−0.82, p = 0.007), suggesting that glacial meltwater (the driver that explains both surface water temperature (SWT) (°C) and nitrate (NO3 + NO2-N)) is the environmental variable that explains the most variance (15%). On average, lakes receiving glacial meltwater were 2.62 °C colder and contained 66% more NO3 + NO2-N than lakes only receiving meltwater from snow. The presence of taxa from the tribe Diamesinae indicates very cold input from running water, and these taxa may be used as a qualitative indicator species for the existence of glacial meltwater within a lake catchment. Heterotrissocladius, Diamesa spp., and Pseudodiamesa were present in the coldest lakes. Chironomus, Diplocladius, and Protanypus were assemblages found in cold lakes affiliated with the littoral zone or alpine streams. The modern benthic chironomid communities collected from the alpine of subalpine lakes of Rocky Mountain National Park, Colorado, represent a range of climatic and trophic influences and capture the transition from cold oligotrophic lakes to warmer and eutrophic conditions.

Fluxes of Physicochemical Parameters in The Cross River Estuary, Nigeria

Study on the fluxes of physicochemical parameters and nutrients in the Cross River estuary ecosystem was under taken between June, 2016 and April, 2017. Field data were collected bimonthly at five stations and analysed both insitu and in the laboratory using standard methods. The monthly mean surface water temperature ranged from 26.68±0.74 OC in June 2016 to 33.6±7.84 OC in October 2016, salinity ranged from 0.10±0.12 ‰ in October 2016 to 10.20±2.80 ‰ in March 2017, and DO from 2.740±0.563 mg/l in June 2016 to a maximum of 5.340±2.152 mg/l in January 2017. Values obtained for PO4 , SO4 , NO3 , DO, and BOD in this study were below the permissible limits [1]. There was significant (p < 0.05) temporal variation in all the parameters studied (PO4 , NO3 , SO4 , DO, BOD5 , salinity, temperature and transparency). There was no significant (p > 0.05) spatial variation in PO4 , NO3 , SO4 , temperature and transparency. Parameters studied showed both positive and negative correlations. The implications of these findings are discussed.

Physico-chemical Attributes Study from Different Sources of Freshwater Bodies in and around Barishal University Campus, Barishal, Bangladesh

This study measured surface water temperature, water pH, TDS, EC, DO, nitrate, ammonium, sulphate and DIP as water physico-chemical properties of four freshwater reservoirs from Barishal Sadar upozilla. The surface water temperature was recorded highest (22.4 °C) in station 4 and loest was in station 1. Water pH, nitrate, ammonium and sulphate showed almost same results among the four reservoirs. TDS and EC values range from 188 to 215 mg/l and 195 to 225 µS/cm, respectively. DO level was almost similar in all the stations except station 1 which showed comparatively lowest amount (4.55 mg/l). DIP ranges from 3.20 to 4.15 mg/l. Among the four reservoirs, comparatively newly established BU pond (station 4) showed poor results than the others.