Ambient Water Temperature Research Articles

Abundant post‐fire recruitment and rapid seedling maturity emphasise regular burning is beneficial for conserving the Vulnerable Purple‐flowered Wattle (Acacia purpureopetala)

SummaryPurple‐flowered Wattle (Acacia purpureopetala) has a Vulnerable status under the Queensland Nature Conservation Act (1992) and is listed as Critically Endangered under the Environment Protection and Biodiversity Conservation Act (1999). It grows in eucalypt woodlands of North Queensland. Its post‐fire response was examined to better understand its ecology and management requirements. Before and after fire surveys found Purple‐flowered Wattle is a fire‐killed ‘obligate seeder’ with abundant fire‐promoted germination, but limited recruitment in the absence of fire, highlighting the importance of regular burning for generating new plants. Nearly half of Purple‐flowered Wattle seedlings began producing seed in their second year, indicating a population tolerant of frequent burning. Combined, the abundant fire‐promoted recruitment and rapidly maturing seedlings suggest regular patchy fires that allow some mature plants to survive unburnt while promoting recruitment in burnt areas would benefit the population. A laboratory trial found percentage germination after 3 weeks was significantly higher for seeds treated by soaking in hot water for 5 minutes (31% germination), compared with those soaked in ambient temperature water (4% germination). However, by 5 weeks, germination differences between seed treatment were not statistically significant. The apparent discrepancy where unheated seeds eventually germinated in a laboratory setting, yet in situ germination was almost completely restricted to the post‐fire environment, warrants further investigation. It may be that successful germination and seedling establishment in woodlands requires the rapid removal of physical dormancy, or perhaps keeping unheated seed constantly moist for 5 weeks in a laboratory trial is simply an unnatural treatment producing a germination response not relevant to ecosystem function. The abundant fire‐triggered germination and rapid maturity of seedlings, combined with the known population number (>4,000 plants) and distribution range (850 km2), support existing recommendations that Purple‐flowered Wattle warrants a Vulnerable rather than Critically Endangered Environment Protection and Biodiversity Conservation Act (1999) status, as is current at the state level. Management that includes regular patchy burning with good soil moisture that reduces the extent and intensity of individual fires is likely to benefit the long‐term preservation of this restricted species and associated species of its ecosystems.

Cu incorporating into OMS-2 lattice creates an efficient Hg0 removal sorbent in natural gas with ambient-temperature H2S/H2O tolerance

Removing mercury in wet natural gas containing acidic components is essential to developing the natural gas purification industry and mitigating corrosion in aluminum heat exchangers. In this work, the Cu-doped manganese oxide octahedral molecular sieve (OMS-2) nanorods were designed for oxidation of Hg0 in wet natural gas. The Hg0 removal efficiency over Cu(0.05)-OMS-2 reached 98.2 % under a high space velocity of 24 × 104 h−1 and a complex atmosphere containing H2O, CO2, and H2S. Surface reactive oxygen species produced by strong electronic interactions owing to Mn-O-Cu hybridization was the main active sites for Hg0 oxidation. The reactive oxygen species on Cu(0.05)-OMS-2 reacted with H2S to form active sulfur species, which could combine with Hg0 to form HgS. Cu(0.05)-OMS-2 exhibited excellent ambient-temperature water resistance, which was attributed to the good redox properties caused by Cu incorporation. This work provided a new strategy for designing efficient sorbents to remove Hg0 from wet natural gas.

Modeling the cooling effect of urban green spaces: The neglected control variables of ‘soil moisture’ and ‘biotope types’

Cooling by plant evapotranspiration (ET) is a prominent ecosystem service provided by urban green spaces (UGSs). UGSs counteract the warming of cities during heat waves. This study presents a GIS model to quantitatively assess the cooling intensity (CI) of UGS units (biotope types) during heat waves at the landscape scale. We conceptualize the CI as a physical index based on the ET of UGSs. Cooling intensities are calculated using the ambient temperature, biotope types, soil characteristics, and initial soil water conditions at the beginning of a heat wave as inputs. We calibrated and validated the model against the surface temperature in the city of Bochum, Germany, based on the thermal band of an orthorectified and calibrated atmospheric-, temperature- and emissivity-corrected mosaic from an airborne hyperspectral scanner. The Nash-Sutcliffe efficiency coefficient of the calibrated model is 0.75. The initial soil water content in the urban area affected the modeled CI by up to 2.6 K, and under the same transpiration rate, whether the initial ambient air temperature was 27 or 37 °C had effects of up to 2 K on the CI. The CI increased by up to 1 K with area size up to 2.5 ha. The purpose of the model was to evaluate and compare the CI of current and planned spatial patterns of land units to mitigate urban heat islands. The similar range of the goodness-of-fit criteria of the uncalibrated model compared to the calibrated model indicated the robustness and transferability of the model.

Heat loss or heat uptake? Skin temperature in Antillean manatees (Trichechus manatus manatus, Sirenia: Trichechidae) in Belize

Introduction: The two subspecies of the West Indian manatee (Trichechus manatus), Florida manatees (T. m. latirostris) and Antillean manatees (T. m. manatus), face different environmental challenges. While Florida manatees have to cope with winter water temperatures below their lower critical temperature of ~ 20 °C and air temperatures below freezing, Antillean manatees live in year-round warm Caribbean waters. Sirenians lack effective thermal insulation and have limited capability of controlling peripheral heat loss. Although severe cold related health issues and mortality are primarily known in Florida manatees, it can be assumed that Antillean manatees and other extant sirenians share the cold-sensitivity, but hardly ever experience it. Contrarily, during summer, Antillean manatees may face the opposite form of thermal stress by being exposed to water temperatures close to their body temperature. However, the upper critical temperature of manatees is not known.
 Objective: To improve understanding of the impact of high ambient temperatures on manatee physiology.
 Methods: We measured skin temperature in six Antillean manatees in two different habitats in Belize, and compared the results to skin temperatures measured in two captive Florida manatees.
 Results: We found a similar temperature distribution pattern over the body surface in both subspecies, but significantly higher temperatures and larger temperature ranges among measuring points in Antillean manatees as compared to Florida manatees. In one Antillean manatee, skin temperature was consistently lower than ambient water temperature by up to 2.5 °C. This implies potential heat uptake from the environment, in contrast to the heat loss experienced by Florida manatees at low water temperatures, apparent in skin temperatures above ambient water temperature.
 Conclusions: Our findings suggest that heat stress may be a more likely risk for manatees in warm tropical waters. Despite the small sample size, our results present important findings towards understanding thermal tolerance and impact of high ambient temperatures on manatee physiology.

Numerical study on the performance of a solar-assisted heat pump coupled with a photovoltaic-thermal air heater

Solar-assisted heat pumps (SAHPs) with photovoltaic-thermal technologies are promising systems for efficiently converting solar energy into useful thermal energy. In this paper, the performance of a SAHP coupled with a novel photovoltaic-thermal air heater (PVTAH) was evaluated under various operating and geometrical parameters. The PVTAH used in this study has a triangular block to improve its thermal efficiency, which also increases the heat pump performance. Using the heat balance equations, a mathematical model was developed and validated through experimental results. With the developed model, the effects of the air mass flow rate, PVTAH area, solar intensity, ambient temperature, and inlet water temperature on the performance of the SAHP with a PVTAH were examined and discussed. The results indicate that the SAHP with PVTAH could operate independently without power from the grid under most conditions, as the PVTAH generates more power than the system requires. In addition, compared to the traditional air-source heat pump, the SAHP with PVTAH enhanced the coefficient of performance of the heat pump by 13.28 %. Consequently, the feasibility of the proposed system was confirmed and this hybrid system is worthwhile to promote and apply.

A new way to understand migration routes of oceanic squid (Ommastrephidae) from satellite data

AbstractVisible Infrared Imaging Radiometer Suite (VIIRS) Boat Detection (VBD) data have been widely used to study the patterns of fishing grounds and their linking to fishery targets, particularly species mainly caught by jiggers. In line with most species in the Ommastrephidae family, the population of Todarodes pacificus is made up of various splinter cohorts concerning the timing and location of hatching. Therefore, the satellite‐recorded fishing grounds consist of groups with complex age structures and different migration directions within cohorts. This study examined the age composition of harvestable stocks (age spectrum) of T. pacificus in the Japan Sea based on an early life history individual‐based model of T. pacificus and VBD data. Using the age spectrum, we analysed the relationship between fishery effort and the age of the target group. It was found that jiggers most prefer individuals around 310 ± 20 days. Furthermore, the correlation between ambient water temperature and fishing effort revealed that T. pacificus migrated to colder waters, reaching the coldest waters at 250 ± 7.5 days before moving back towards warmer waters. We discussed a possible way to use the age‐temperature relationship to analyse the flow of VBD distributions to record the movements related to the migration of the fishing target. The results show migration‐like trajectories, which are initially parallel to the isotherm, gradually deflect towards lower temperature sides over several months, sharply turn for about a month and then move back with a slight angle to the isotherms. The method provides a potential framework to improve our understanding of the active migration of oceanic squid.

The effects of coolant mass flow rate and atmospheric indicators in a PV/T system with experimental and ANN’s models

In this study, the effects of the mass flow rate of coolant and other atmospheric and positional variables on the performance and efficiency of a PV/T system have been experimentally researched and modeled with ANN’s models. Mass flow rate, irradiance, ambient temperature, wind speed, wind direction, relative humidity and coolant water inlet temperature have been measured while solar azimuth angle and solar elevation angle have been calculated. These parameters have been selected as the input parameters (independent variables), mainly having the preliminary focus on the mass flow rate of the coolant. The performance parameters namely, electrical power production, thermal energy production, total energy production, temperature decrease on the PV module, electrical efficiency increase, surface temperature of the PV module and water outlet temperature for the PV modules have been experimentally measured. They were also computed by ANN models, as the output variables (dependent variables) with the most robust estimation of FBPANN based models depending on the real measurement data set from the experimental works. The relevance of the dependability of each targeted variables were revealed by statistical indicators in order to maintain the sensitivity of the ANN calculations. Among all the dependent parameters that were predicted by the ANN models, the strictest predictions were found for electrical power production by the FFANN1 model with the R value of 99.985% and the R2 value of 99.971%. Also, all of the performance parameters have robustly been predicted by the FFANN models. Besides, the order of importance of the predictors that effects dependent variables has been found. The mass flow rate has been determined to be highly effective on electrical efficiency increase, surface temperature of the PV module, electrical power production, thermal energy production and total energy production. The benefit of the present work is that the effects of daily working parameters such as mass flow rate of coolant with respect to the other atmospheric indicators on instantaneous electrical and thermal performance of a PV or PV/T system can be robustly predicted with their order of importance with the developed ANN models. It will make the investors to easily manage their systems.

High temperature transcritical CO2 heat pump with optimized tube-in-tube heat exchanger

CO2 heat pump operating on tanscritical cycle is widely adopted to provide hot water whose temperature is as high as about 90 °C. Recently, it is recognized that high temperature heat pump has promising application in various industries such as papermaking, chemical, automotive, and metallurgical. Then, in this paper a model of a tube-in-tube heat exchanger was established, and its parameters including tube length, fin height, fin number, fin thickness and helix angle are optimized through simulation to enhance its heat transfer performance, Accordingly, a transcritical CO2 heat pump system which can provide about 100 °C pressurized hot water is proposed and investigated. Subsequently, an experimental setup is constructed and operated under ambient temperatures, inlet and outlet temperatures of cooling water to demonstrate the feasibility of obtaining hot water at 100 °C. When the ambient temperature and inlet water temperatures are 40 °C and 9 °C respectively, the highest COP of 3.64 is obtained in experiments and the corresponding simulated value is 3.87. When the ambient temperature is 40 °C, inlet and outlet water temperatures are 9 °C and 85 °C, respectively, the study recorded the highest COP of 4.47. It is worth noting that both the heating capacity and COP increase with rising ambient temperature.

Upper-ocean temperature characteristics in the subantarctic southeastern Pacific based on biomarker reconstructions

Abstract. As remnants of living organisms, alkenones and isoprenoid glycerol dialkyl glycerol tetraether lipids (isoGDGTs) are widely used biomarkers for determining ocean water temperatures from the past. The organisms that these proxy carriers stem from are influenced by a number of environmental parameters, such as water depth, nutrient availability, light conditions, or seasonality, which all may significantly bias the calibration to ambient water temperatures. Reliable temperature determinations thus remain challenging, especially in higher latitudes and for undersampled regions. We analyzed 33 sediment surface samples from the southern Chilean continental margin and the Drake Passage for alkenones and isoGDGTs and compared the results with gridded instrumental reference data from the World Ocean Atlas 2005 (WOA05) and previously published data from an extended study area covering the central and western South Pacific towards the Aotearoa / New Zealand continental margin. We show that for alkenone-derived sea surface temperatures (SSTs), the widely used global core-top calibration of Müller et al. (1998) yields the smallest deviation of the WOA05-based SSTs. On the contrary, the calibration of Sikes et al. (1997), determined for higher latitudes and summer SSTs, overestimates modern WOA05-based SSTs in both the annual mean and summer. Our alkenone SSTs show a slight seasonal shift of ∼ 1 ∘C at the southern Chilean margin and up to ∼ 2 ∘C in the Drake Passage towards austral summer SSTs. Samples in the central South Pacific, on the other hand, reflect an annual mean signal. We show that for isoGDGT-based temperatures, the subsurface calibration of Kim et al. (2012a) best reflects temperatures from the WOA05 in areas north of the Subantarctic Front (SAF). Temperatures south of the SAF are, in contrast, significantly overestimated by up to 14 ∘C, irrespective of the applied calibration. In addition, we used the GDGT [2]/[3] ratios, which give an indication of the production depth of the isoGDGTs and/or potential influences from land. Our samples reflect a subsurface (0–200 m water depth) rather than a surface (0–50 m water depth) signal in the entire study area and show a correlation with the monthly dust distribution in the South Pacific, indicating terrigenous influences. The overestimation of isoGDGT surface and subsurface temperatures south of the SAF highlights the need for a reassessment of existing calibrations in the polar Southern Ocean. Therefore, we suggest a modified Southern Ocean tetraether index (TEX86)-based calibration for surface and subsurface temperatures, which shows a lower temperature sensitivity and yields principally lower absolute temperatures, which align more closely with WOA05-derived values and also OH–isoGDGT-derived temperatures.

Improvement of Geothermal Power Plants by Utilizing Hydrogen Steam Superheating: A Review

The rapid growth of geothermal power plants is due to their great potential and environmentally friendly energy source. In its development, hydrogen is used as energy storage for several intermittent renewable energy sources. Hydrogen Steam Superheating utilizing hydrogen products can pressure steam as additional fuel to operate steam turbines. The electrolysis method with high-temperature water fluid produces more hydrogen content and is more efficient than ambient temperature water; therefore, it is suitable for producing superheating hydrogen steam by electrolysis using geothermal power plants. A combined cycle (flash & binary) geothermal power plant with additional hydrogen steam superheating can increase the power 8 - 9 MW using the mixed working fluid R-31-10 and RC-318 in a binary cycle power plant and improve the thermal efficiency of flash cycles by up to 12.3%. Thus, the application of adding hydrogen steam superheating is a method that can be utilized to increase the power capacity of geothermal power plants, replacing the current conventional method of drilling to open steam production wells.

Exceptions to the temperature–size rule: no Lilliput Effect in end‐Permian ostracods (Crustacea) from Aras Valley (northwest Iran)

AbstractThe body size of marine ectotherms is often negatively correlated with ambient water temperature, as seen in many clades during the hyperthermal crisis of the end‐Permian mass extinction (c. 252 Ma). However, in the case of ostracods, size changes during ancient hyperthermal events are rarely quantified. In this study, we evaluate the body size changes of ostracods in the Aras Valley section (northwest Iran) in response to the drastic warming during the end‐Permian mass extinction at three taxonomic levels: class, order, species. At the assemblage level, the warming triggers a complete species turnover in the Aras Valley section, with larger, newly emerging species dominating the immediate post‐extinction assemblage for a short time. Individual ostracod species and instars do not show dwarfing or a change in body size as an adaptation to the temperature stress during the end‐Permian crisis. This may indicate that the ostracods in the Aras Valley section might have been exceptions to the temperature–size rule (TSR), using an adaptation mechanism that does not involve a decrease in body size. This adaptation might be similar to the accelerated development despite constant instar body sizes that can be observed in some recent experimental studies of ostracod responses to thermal stress.

A time series based machine learning strategy for wastewater-based forecasting and nowcasting of COVID-19 dynamics

Monitoring COVID-19 infection cases has been a singular focus of many policy makers and communities. However, direct monitoring through testing has become more onerous for a number of reasons, such as costs, delays, and personal choices. Wastewater-based epidemiology (WBE) has emerged as a viable tool for monitoring disease prevalence and dynamics to supplement direct monitoring. The objective of this study is to intelligently incorporate WBE information to nowcast and forecast new weekly COVID-19 cases and to assess the efficacy of such WBE information for these tasks in an interpretable manner. The methodology consists of a time-series based machine learning (TSML) strategy that can extract deeper knowledge and insights from temporal structured WBE data in the presence of other relevant temporal variables, such as minimum ambient temperature and water temperature, to boost the capability for predicting new weekly COVID-19 case numbers. The results confirm that feature engineering and machine learning can be utilized to enhance the performance and interpretability of WBE for COVID-19 monitoring, along with identifying the different recommended features to be applied for short-term and long-term nowcasting and short-term and long-term forecasting. The conclusion of this research is that the proposed time-series ML methodology performs as well, and sometimes better, than simple predictions that assume available and accurate COVID-19 case numbers from extensive monitoring and testing. Overall, this paper provides an insight into the prospects of machine learning based WBE to the researchers and decision-makers as well as public health practitioners for predicting and preparing the next wave of COVID-19 or the next pandemic.

Evolution of biomass particles during pelletization process

Pulverizing is an essential unit operation in co-firing biomass with coal. Pulverizers are only compatible with pellet forms of fibrous biomass materials and crush them down to their original forming particle sizes. That is why the data on the size distribution of the particles forming a biomass pellet is crucial to achieving optimum combustion conditions. The current study determines the internal particle size distribution of pellets after wet disintegration, following ISO 17830 standard, and aims to suggest improvements to the mentioned standard based on new measured evidence. Experiments were carried out on white wood pellets (no bark) and brown wood pellets containing bark at four water temperatures: 20, 40, 60, and 95 °C, with or without stirring. The particle size distribution of the pre-pelletizer wood particles was also measured and compared with particles in the formed pellets. Ambient water temperature of 20 °C was found to be adequate for the complete disintegration of pellets, and no mechanical stirring was required. About 30% of particles in the disintegrated pellets were 0.5–1.0 mm. Pelletization changes the particle size distribution to smaller particles. The disintegrated bark pellets contained more fines than white pellets.

Abrupt water temperature increases near seafloor during the 2011 Tohoku earthquake

We investigated temperature records associated with seafloor pressure observations at eight stations that experienced the 2011 Mw 9 Tohoku earthquake near its epicenter. The temperature data were based on the temperature measured inside the pressure transducer. We proposed a method to estimate ambient water temperature from the internal temperature using an equation of heat conduction. The estimated seafloor water temperature showed remarkable anomalies, especially increases several hours after the Mw 9 earthquake. A station of P03 (sea depth of 1.1 km) showed an abrupt temperature increase of + 0.19 °C that occurred ~ 3 h after the earthquake, which lasted for several hours. At stations of GJT3 (sea depth of 3.3 km) and TJT1 (sea depth of 5.8 km), there were abrupt temperature anomalies of + 0.20 °C and + 0.10 °C that began to occur 3–4 h after the earthquake. These anomalies both decayed to their original levels over a few tens of days. During the decay processes, only TJT1 showed several intermittent temperature rises. A water temperature anomaly within + 0.03 °C was found up to ~ 500 m above TJT1 2 weeks after the earthquake. There was no significant anomaly at the other five stations. Processes to cause these seafloor temperature anomalies were discussed. The temperature anomaly of P03 was reasonably caused by a tsunami-generated turbidity current, as also suggested by a previous study. Meanwhile, we proposed a scenario that the abrupt temperature anomalies of GJT3/TJT1 and the intermittent anomalies of TJT1 were caused by warm water discharges from the subseafloor. The pathways of the warm water were probably composed of the branch normal fault between GJT3 and TJT1, the reverse fault near TJT1, the backstop interface, and perhaps reverse faults at the frontal prism. The proposed scenario was almost compatible with other studies based on epicentral observations. We estimated the heat properties of the initial temperature anomalies of GJT3/TJT1. The estimated heat source might be explained by that most of the geothermal fluids trapped in those fault pathways were discharged to the seafloor immediately after the earthquake. The onsets of the subsequent intermittent anomalies of TJT1 were possibly activated by low or falling ocean tidal loading.

Bivalent Carbon Dioxide Heat Pump for Heating Multi-Storey Buildings

The aim of the work is to analyze the operation of a hybrid heat pump that simultaneously uses the heat of the return network water and outdoor air for heating multi-storey buildings. To achieve this goal, the following tasks are solved: the influence of influences on the temperature of the return network water, air temperature and their compensation on the operation of the product is considered, intermediate circuits at the evaporator and gas cooler are considered for transferring a variable heat load to the heat pump and from the heat pump. The most significant results are the hydraulicaerodynamic scheme of the heat pump, the schemes of the intermediate circuits before the evaporator and the gas cooler. The significance of the results obtained lies in the establishment of such technical solutions for the CHP - heat pumps system, which allow saving gas consumption at the CHP, the cost of heat consumers to pay bills. The use of a working fluid cooler before the gas cooler of the heat pump to control the temperature of the direct network water of the heating system of the building allows you to select such a compressor pressure at which the amount of heat given off by the heat pump to the building will correspond to the temperature curve. In this case, it is desirable to install an air-torefrigerant heat exchanger after the compressor before the gas cooler. It has been established that a PI controller can be used to control the temperature at the outlet of the gas cooler through the inlet air channel.of various parameters, including solar radiation, ambient temperature, compressor speed and initial water temperature, have been simulated and analyzed on the thermal performance of the system.

Western South Atlantic seasonal variability recorded in a mid-deglacial bivalve from the outer Uruguayan continental shelf

The oceanographic dynamics on the continental shelf off southeastern South America are primarily controlled by the southward-flowing warm Brazil Current, converging with the northward-directed cold Malvinas (Falkland) Current, and interacting with the continental discharge of the Plata River. The seasonally reversing regional wind field together with the seasonal cycle of riverine discharge, determines which of these three components provides the dominant forcing. The Uruguayan shelf is thus located in a transitional zone that extends from the region influenced by the Brazil-Malvinas Confluence (BMC) in the open ocean to the Subtropical Shelf Front (STSF) on the continental shelf. Understanding how the resulting oceanic seasonal variability responded to different climatic boundary conditions may shed light on its future behavior. This study presents the first reconstruction of mid-deglacial seasonal hydrographic variability on the continental shelf off southeastern South America in seasonal resolution based on stable oxygen and carbon isotopes (δ18O, δ13C) from a thick-walled shell of a long-living bivalve. The mid-deglacial (14.3 cal ka BP; Bølling-Allerød interstadial) Retrotapes exalbidus bivalve shows a mean δ18O of 3.27 ± 0.42‰ (2.50 ± 0.42‰ when corrected for changes in global ice volume) and a seasonal δ18O amplitude of 1.69‰ for raw isotopic excursions. Moreover, the δ13C exhibits abrupt negative peaks coincident with more negative δ18O values that indicate seasons of elevated freshwater discharge. Finally, the growth rate of the bivalve suggests that the specimen was closer to the metabolically optimum than modern individual of this species from southern South America. Combining biogeographic and ecologic information with these isotopic data, the results point to colder waters and a slightly lower mid-deglacial seasonal amplitude in temperature compared with modern conditions at this shelf site. Because of the northward-displaced Plata River mouth during deglacial times, negative δ13C peaks are expected to reflect an influence of non-point freshwater sources in the form of small fluvial distributaries along the paleo-coast. Most of this signal may, however, be driven by seasonal metabolic effects associated with low ambient water temperatures related to a shallow-water environment located closer to the respective paleo-coastline due to the low sea level at those times.

How do ambient conditions and management actions affect manatee movements and habitat use?

AbstractKings Bay in northwest Florida, USA, is an important winter home of the largest aggregation of Florida manatee (Trichechus manatus latirostris), and the only location in the United States where visitors legally swim and interact with manatees. In addition to ambient conditions, visitors to the area and management actions have the potential to influence manatee behaviors. We tracked 32 manatees with satellite‐linked global position system (GPS) telemetry tags in Kings Bay from 2006 to 2018. Also, personnel at Crystal River National Wildlife Refuge collected manatee counts at Three Sisters Springs from 2014 to 2017. Our objectives were to document the use of springs and other habitat components in Kings Bay relative to ambient water temperature, time of day, tide stage, and management actions within Three Sisters Springs and other manatee sanctuaries in the bay. Manatees that we tagged in Kings Bay spent a median 87% of the winter within the local study area, compared to 47% for animals that we tagged in the Florida Panhandle. Manatees showed preferences for King and Magnolia springs basins at low tide, indicating that they function as tidal refuges, when other locations may be less accessible; we also recorded within spring basin movements. Magnolia Spring Basin showed a significant diel pattern overall, and within basins, King Spring, Tarpon Hole, and Three Sisters Springs were used more during the night than during the day. All areas outside Kings Bay were used more at warmer ambient gulf water temperatures, while all of the springs basins were used more when gulf temperature was colder, especially Three Sisters Springs Basin. Management of Three Sisters Springs had an influence on manatee use during times of cold ambient gulf water temperatures; manatees used the springs more when the spring was closed to visitors, versus when the springs were completely open or when the spring lobes alone were closed. Manatee decisions were consistent with avoiding human interactions.

Stress Response of European Common Frog (Rana temporaria) Tadpoles to Bti Exposure in an Outdoor Pond Mesocosm

The biocide Bacillus thuringiensis var. israelensis (Bti) is applied to wetlands to control nuisance by mosquitoes. Amphibians inhabiting these wetlands can be exposed to Bti multiple times, potentially inducing oxidative stress in developing tadpoles. For biochemical stress responses, ambient water temperature plays a key role. Therefore, we exposed tadpoles of the European common frog (Rana temporaria) three times to field-relevant doses of Bti in outdoor floodplain pond mesocosms (FPM) under natural environmental conditions. We sampled tadpoles after each Bti application over the course of a 51-day experiment (April to June 2021) and investigated the activity of the glutathione-S-transferase (GST) and protein carbonyl content as a measure for detoxification activity and oxidative damage. GST activity increased over the course of the experiment likely due to a general increase of water temperature. We did not observe an effect of Bti on either of the investigated biomarkers under natural ambient temperatures. However, Bti-induced effects may be concealed by the generally low water temperatures in our FPMs, particularly at the first application in April, when we expected the highest effect on the most sensitive early stage tadpoles. In light of the global climate change, temperature-related effects of pesticides and biocides on tadpoles should be carefully monitored - in particular since they are known as one of the factors driving the worldwide decline of amphibian populations.

Reducing dietary wild derived fishmeal inclusion levels in production diets for large yellowtail kingfish (Seriola lalandi)

Further research to understand the effect of dietary wild derived fishmeal (WD-FM) substitution with commercially relevant alternative ingredients for large yellowtail kingfish (Seriola lalandi; YTK) was investigated. This 36-week study was designed to replace dietary inclusions of WD-FM with alternative protein ingredients including poultry meal, soy protein concentrate and by-product fishmeal (PM, SPC and BP-FM) and measure the effect on the growth performance, feed utilisation, and health of large YTK (2.5 kg initial weight) at ambient water temperatures (average 16.6 °C). Six diets were formulated on a digestible basis to contain 39% digestible protein (∼45–46% crude protein), 23% digestible lipid (∼24–25% crude lipid), and a digestible energy level of 17 MJ kg−1 (∼19 MJ kg−1 gross energy level). Fish were fed to apparent satiation once daily at 10:00 h. Substitution of fish meal with alternative ingredients did not significantly impact fish growth, feed utilisation, gastrointestinal health, blood haematology or measured biochemistry indices. Results from the current study will allow reductions to the dietary WD-FM inclusion levels, with tangible sustainability benefits. The inclusion of the alternative protein sources resulted in improvements in the fish in-fish out ratios of up to 35.1%. This study suggests formulation criteria for large YTK should include a minimum of 10% WD-FM. Further to this, at least 30% of the diet should consist of a combination of poultry meal, soy protein concentrate and fishmeal (both wild and by-product). Our data further support the use of BP-FM up to ∼20% inclusion, while PM and SPC should be limited to ∼10% inclusion until further data is available on these raw materials in YTK feeds. These recommendations will facilitate formulation flexibility for large YTK feeds, enabling formulators to adapt to changes to extrinsic factors such as raw material availability, and sustainability while minimising cost and performance impacts.

Experimental evaluation of the transient and steady state performance of an air-cooled square minichannel heat exchanger

Transient and steady state performance of an air-cooled square minichannel heat exchanger was experimentally evaluated. 82 minichannels of square cross section, 11 cm long and 2 mm width, were manufactured on AISI 316 L. Heat sinks made of aluminium were attached to each side of the heat exchanger. Natural and forced air convection were investigated, while the hot fluid was flowing in the downward counterflow direction. Two other variables were changed: inlet water temperature, from 34.8 to 75.4 °C, and water flow rate, from 5.7 to 29.1 kg/h, while in the case of forced air convection its velocity was fixed at 0.75 m/s. Ambient air temperature and water temperature and pressure at the inlet and outlet were measured. Results obtained include the thermal resistances and heat capacities in the different parts of the heat exchanger, the transient time, the residence time of water inside the heat exchanger and the time constant of the device. Correlations were obtained to predict the duration of the transient period in the natural and forced convection cases. Additionally, a lumped mass heat transfer model was developed to estimate the time evolution of the average water temperature in the heat exchanger.