Abiotic control on the dissipation of chlorpyrifos spiked in an Udic Ferrisol at a lower dosage

The dissipation routes of chlorpyrifos spiked in an Udic Ferrisol at the dosage of 400 ng g^?1, which represents a residual level after an agricultural application, were studied in a laboratory, using the natural soil under three moisture regimes, sterilised, and organic matter-free soils in the dark at 20°C. The obtained results showed that higher soil moisture caused faster dissipation, and the abiotic and biotic contributions to the total dissipated amount of the applied chlorpyrifos in the soil accounted for 77.3–85.2% and 14.7–22.7%, respectively. In the sterilised soil, the contribution of organic matter to chlorpyrifos dissipation was noticed to account for 95% in the earlier two weeks, and was nearly equal to that of soil minerals two weeks after the incubation.     

Isolation and characterisation of a carbofuran degrading Burkholderia sp. PCL3 from carbofuran-phytoremediated rhizosphere soil

A bacterial strain capable of degrading carbofuran as the sole carbon source was isolated from carbofuran-phytoremediated rhizosphere soil of rice. A 16S rRNA study identified the strain as Burkholderia sp. (isolate PCL3). Free cells of isolate PCL3 possessed inhibitory-type degradation kinetics with a q _max of 0.087 day^?1 and S _m of 248.76 mg·L^?1. Immobilised PCL3 on corncob and sugarcane bagasse possessed Monod-type degradation kinetics with a q _max of 0.124 and 0.098 day^?1, respectively. The optimal pH and temperature with the highest degradation rate coefficient of carbofuran were pH 7.5 and 35 °C, respectively.     

Bioactivity,adsorption and persistence of pretilachlor in paddy field soils

The effects of environmental factors on bioactivity, adsorption and persistence of pretilachlor were studied in the laboratory and greenhouse using cucumber (Cucumis sativus L.) as the bioassay species. The three soils studied viz. Bernam, Selangor and Sabrang series were chosen for their different characteristics. The half‐life of pretilachlor decreased from 10.24 to 4.90 days as temperature increased from 25°C to 35°C in the Selangor Series soil and from 10.86 to 7.63 days in the Bernam Series soil at 60% field capacity. At the same moisture level, an increase of temperature from 25°C to 35°C also reduced the half‐life of pretilachlor in Sabrang soil from 8.87 to 2.59 days. The half‐life of pretilachlor also decreased with increasing moisture levels in Selangor and Sabrang series but not in Bernam series soils. The greatest adsorption of pretilachlor was observed in Bernam series, followed by Selangor and Sabrang series. No phytotoxic residue of pretilachlor was detected in the supernatant after 10 h incubation. Since the residue was strongly adsorbed in Bernam series, its biological activity was less than in the other soils studied.     

Effect of light and temperature on the population dynamics of two toxic bloom forming Cyanobacteria – Microcystis ichthyoblabe and Anabaena aphanizomenoides

The effect of light and temperature on the growth of Microcystis ichthyoblabe and Anabaena aphanizomenoides, isolated from the subtropical Oued Mellah lake, Morocco (33°30′N–07°20′W), were investigated in batch culture. Growth rates at 66 light–temperature combinations were determined and fitted with different mathematical models. The results show that the two Cyanobacteria grow at all light intensities and temperatures, except at 10 °C for A. aphanizomenoides, where the growth was strongly limited. The μ_max of M. ichthyoblabe increased with temperature from 0.56 d^?1 at 10 °C to 1.32 d^?1 at 35 °C. At all tested temperatures, a relative photoinhibition within the studied range of irradiance was observed and the photosensitivity was thermodependent. For Anabaena, the obtained μ_max ranged between 0.07 d^?1 at 10 °C and 1.46 d^?1 at 35 °C, and a weak photoinhibition was observed at 15 °C. The positive correlation between μ_max and I_opt (r²≥0.93) indicates a close interaction between light and temperature on the cyanobacteria growth. The results obtained in this work suggest that the growth of these two species is possible under low light and low temperature.     

Wet oxidation of recalcitrant lignin water solutions: experimental and reaction kinetics

The purpose of the research was to study the behavior of lignin degradation under different conditions (T 110–190°C, pO₂ 0.5–1.5 MPa, pH 5, 9 and 12) and to develop a predictive model. Temperature increase improved lignin removal from 75% at 110°C to 100% at 190°C (experimental). Increasing the pH enhanced the lignin removal efficiency from 30 to 97% (experimental). The developed model predicted the lignin degradation and changes in COD, BOD and TOC. The model agreed well with the experimental data (R ² = 0.93 at pH 5 and 12).     

The effect of ration size, temperature and body weight on specific dynamic action of the common cuttlefish Sepia officinalis

The effect of meal size (shrimp Crangon crangon) [0.83–18.82% dry body weight (Dw)] on specific dynamic action (SDA) was assessed in cuttlefish Sepia officinalis (1.03–6.25 g Dw) held at 15 and 20°C. Cuttlefish <2 g significantly expended less energy in feeding and digesting their meal than cuttlefish >2 g when given the same quantity of food. Handling, eating and digesting a shrimp meal was temperature dependent with cuttlefish processing and digesting a similar sized shrimp meal faster at 20°C than at 15°C. The proportional increase in oxygen consumption (2.07 ± 0.02) was not correlated with feeding rate (FR) and was independent of temperature and cuttlefish size. The SDA peak was not correlated with FRs, and increased as cuttlefish size and temperature increased. The mean SDA coefficient was 0.87 ± 0.07% of the ingested energy; one of the lowest SDA values recorded amongst vertebrates and invertebrates. Daily energy requirements (KJ day⁻¹) for S. officinalis were calculated from laboratory estimates of energy losses due to standard (MO_{2 Standard}), routine (MO_{2 Routine}) and feeding (MO_{2 SDA}) oxygen consumption. Laboratory estimates of daily metabolic expenditures were combined with results from previous investigations to construct an energy budget for 1 and 5 g cuttlefish consuming a meal of 5 and 15% Dw at 20°C and the amount of energy available for growth was estimated to be between 35 and 80.3% of the ingested energy.     

Effects of two root-secreted phenolic compounds from a subalpine coniferous species on soil enzyme activity and microbial biomass

In order to evaluate the ecological consequences and potential mechanisms of specific C compounds on soil microbial processes under climate warming, we injected solutions of two modelled root exudates, 2,6-di-tert-butyl-4-methylphenol (BHT) and 1,2-benzenedicarboxylic acid, dibutyl ester (DBP), respectively, into soil at two concentrations (20 and 1000?µg?g^?1 soil). For all treatments, soils amended with the two phenolic compounds were incubated at two temperatures (20°C and 30°C) for 30 days. The responses of soil enzyme activity and microbial property to modelled root exudates to some extent depended on temperature regime, exudation component, and addition concentration. For example, the addition of BHT tended to decrease the soil enzyme activities. However, DBP addition generally increased the two metabolic enzyme activities at 30°C, and tended to decrease the two enzyme activities at 20°C, but a significant reduction was observed only at a high concentration at 20°C. The microbial biomass and enzyme activity were generally lower at 30°C compared to those at 20°C, when averaged across all treatment combinations. Taken together, our results indicated that the amounts and quality of liable root-derived C can differentially affect microbial processes, and various environmental changes will greatly complicate root–microbe–soil interactions in forests.     

Differential increment-deposition rate in embryonic statoliths of the loliginid squid Loligo vulgaris

 Apart from one study that reported growth of less than one increment per day in statoliths of the squid Alloteuthis subulata, most studies so far have presumed that one increment was laid down per day in the statoliths of the squid species they examined. The present study provides evidence of differential daily growth rates in embryonic statoliths of the squid Loligo vulgaris Lamarck, 1798, thus confirming a previous report for A. subulata. Incremental growth rates of L. vulgaris statoliths differ as a function of temperature. Squid embryos were incubated in the laboratory at three temperatures (12.0, 15.5 and 21.1 °C), and tetracycline staining was used to follow statolith growth. This growth slowed in squid exposed to the lowest temperature, but recovered when the squid were returned to warm conditions, indicating statolith adaptation. Statolith growth rate after incubation at 12 °C was 1.3% d⁻¹ and reached 6.1% d⁻¹ for squids exposed to 21.1 °C. Statoliths from embryos incubated at 15.5 °C yielded a rate of 1 increment d⁻¹ and a mean daily growth of 2.2 μm in the dorsal dome area of the statolith. In contrast, the slow growth of statoliths incubated at 12 °C yielded a mean daily growth of only 0.9 μm in the dorsal dome and the readings resulted in a less-than-daily increment-deposition rate. Received: 9 October 1999 / Accepted: 30 March 2000     

Growth and development of nauplii and copepodites of the estuarine copepod Acartia tonsa from southern Europe (Ria de Aveiro, Portugal) under saturating food conditions

A temperature-dependent growth model is presented for nauplii and copepodites of the estuarine calanoid copepod Acartia tonsa from southern Europe (Portugal). Development was followed from egg to adult in the laboratory at four temperatures (10, 15, 18 and 22°C) and under saturating food conditions (>1,000 μg C l⁻¹). Development times versus incubation temperature were fitted to a Belehradek’s function, showing that development times decreased with increasing incubation temperature: at 10°C, A. tonsa need 40.3 days to reach adult stage, decreasing to 8.9 days when reared at 22°C. ANCOVA (homogeneity of slopes) showed that temperature (P<0.001) and growth phase (P<0.01) had a significant effect on the growth rate. Over the range of temperatures tested in this study, highest weight-specific growth rates were found during naupliar development (NI–NVI) and varied from 0.185 day⁻¹ (10°C) to 0.880 day⁻¹ (22°C) with a Q ₁₀ equal to 3.66. During copepodite growth (CI–CV), the weight-specific growth rates ranged from 0.125 day⁻¹ (10°C) to 0.488 day⁻¹ (22°C) with a Q ₁₀ equal to 3.12. The weight-specific growth rates (g) followed temperature (T) by a linear relationship and described as ln g=−2.962+0.130 T (r ²=0.99, P<0.001) for naupliar stages and ln g=−3.134+0.114T (r ²=0.97, P<0.001) for copepodite stages. By comparing in situ growth rates (juvenile growth and fecundity) for A. tonsa taken from the literature with the temperature-dependent growth model defined here we suggest that the adult females of A. tonsa are more frequently food limited than juveniles.     

Irradiance and temperature regulation of oxygenic photosynthesis and O2 consumption in a hypersaline cyanobacterial mat (Solar Lake, Egypt)

 Short-term effects of temperature and irradiance on oxygenic photosynthesis and O₂ consumption in a hypersaline cyanobacterial mat were investigated with O₂ microsensors in a laboratory. The effect of temperature on O₂ fluxes across the mat–water interface was studied in the dark and at a saturating high surface irradiance (2162 μmol photons m⁻² s⁻¹) in the temperature range from 15 to 45 °C. Areal rates of dark O₂ consumption increased almost linearly with temperature. The apparent activation energy of 18 kJ mol⁻¹ and the corresponding Q ₁₀ value (25 to 35 °C) of 1.3 indicated a relative low temperature dependence of dark O₂ consumption due to mass transfer limitations imposed by the diffusive boundary layer at all temperatures. Areal rates of net photosynthesis increased with temperature up to 40 °C and exhibited a Q ₁₀ value (20 to 30 °C) of 2.8. Both O₂ dynamics and rates of gross photosynthesis at the mat surface increased with temperature up to 40 °C, with the most pronounced increase of gross photosynthesis at the mat surface between 25 and 35 °C (Q ₁₀ of 3.1). In another mat sample, measurements at increasing surface irradiances (0 to 2319 μmol photons m⁻² s⁻¹) were performed at 25, 33 (the in situ temperature) and 40 °C. At all temperatures, areal rates of gross photosynthesis saturated with no significant reduction due to photoinhibition at high irradiances. The initial slope and the onset of saturation (E _k = 148 to 185 μmol photons m⁻² s⁻¹) estimated from P versus E _d curves showed no clear trend with temperature, while maximal photosynthesis increased with temperature. Gross photosynthesis was stimulated by temperature at each irradiance except at the lowest irradiance of 54 μmol photons m⁻² s⁻¹, where oxygenic gross photosynthesis and also the thickness of the photic zone was significantly reduced at 40 °C. The compensation irradiance increased with temperature, from 32 μmol photons m⁻² s⁻¹ at 25 °C to 77 μmol photons m⁻² s⁻¹ at 40 °C, due to increased rates of O₂ consumption relative to gross photosynthesis. Areal rates of O₂ consumption in the illuminated mat were higher than dark O₂ consumption at corresponding temperatures, due to an increasing O₂ consumption in the photic zone with increasing irradiance. Both light and temperature enhanced the internal O₂ cycling within hypersaline cyanobacterial mats. Received: 30 November 1999 / Accepted: 11 April 2000     

The effects of temperature and salinity on egg production and hatching success of Baltic Acartia tonsa (Copepoda: Calanoida): a laboratory investigation

The functional response of the aspects of reproductive success of a southwestern Baltic population of Acartia tonsa (Copepoda: Calanoida) was quantified in the laboratory using wide ranges in temperatures and salinities. Specifically, daily egg production (EP, # female⁻¹ day⁻¹) was determined for 4 or 5 days at 18 different temperatures between 5 and 34°C and the time course and success of hatching were evaluated at 10 different temperatures between 5 and 23°C. The effect of salinity (0 to 34 psu) on egg hatching success was also examined. The highest mean rates of EP were observed between 22 and 23°C (46.8–50.9 eggs female⁻¹ day⁻¹). When studied at 18 psu, hatching success of eggs increased with increasing temperature and was highest (92.2%) at 23°C. No hatching was observed for eggs incubated at low temperatures (≤12°C) that were produced by females acclimated to temperatures ≤10°C indicating a possible thermal threshold between 10.0 and 13.0°C below which only the production of diapause (or low quality) eggs exists in this population. When tested at 18°C, the hatching success of eggs incubated at 15 different salinities increased asymptotically with increasing salinity and was maximal (81.4–84.5%) between 17 and 25 psu. The high reproductive success observed over wide ranges in temperatures and salinities in this Baltic population demonstrates one of the mechanisms responsible for the cosmopolitan distribution of this species within productive, estuarine and marine habitats.     

Decomposition of perfluorooctanoic acid by microwaveactivated persulfate: Effects of temperature, pH, and chloride ions

Microwave-hydrothermal treatment of persistent and bioaccumulative perfluorooctanoic acid (PFOA) in water with persulfate (S₂O ₈ ^2? ) has been found effective. However, applications of this process to effectively remediate PFOA pollution require a better understanding on free-radical scavenging reactions that also take place. The objectives of this study were to investigate the effects of pH (pH = 2.5, 6.6, 8.8, and 10.5), chloride concentrations (0.01?C0.15 mol·L^?1), and temperature (60°C, 90°C, and 130°C) on persulfate oxidation of PFOA under microwave irradiation. Maximum PFOA degradation occurred at pH 2.5, while little or no degradation at pH 10.5. Lowering system pH resulted in an increase in PFOA degradation rate. Both high pH and chloride concentrations would result in more scavenging of sulfate free radicals and slow down PFOA degradation. When chloride concentrations were less than 0.04 mol·L^?1 at 90°C and 0.06 mol·L^?1 at 60°C, presence of chloride ions had insignificant impacts on PFOA degradation. However, beyond these concentration levels, PFOA degradation rates reduced significantly with an increase in chloride concentrations, especially under the higher temperature.     

Effect of sub-lethal damage to juvenile colonies of massive Porites spp. under contrasting regimes of temperature and water flow

In this study, juvenile colonies of massive Porites spp. (a combination of P. lutea and P. lobata) from the lagoon of Moorea (W 149°50′, S 17°30′) were damaged and exposed to contrasting conditions of temperature and flow to evaluate how damage and abiotic conditions interact to affect growth, physiological performance, and recovery. The experiment was conducted in April and May 2008 and consisted of two treatments in which corals were either undamaged (controls) or damaged through gouging of tissue and skeleton in a discrete spot mimicking the effects of corallivorous fishes that utilize an excavating feeding mode. The two groups of corals were incubated for 10 days in microcosms that crossed levels of temperature (26.7 and 29.6°C) and flow (6 and 21 cm s⁻¹), and the response assessed as overall colony growth (change in weight), dark-adapted quantum yield of PSII (F _v/F _m), and healing of the gouged areas. The influence of damage on growth was affected by temperature, but not by flow. When averaged across flow treatments, damage promoted growth by 25% at 26.7°C, but caused a 25% inhibition at 29.6°C. The damage also affected F _v/F _m in a pattern that differed between flow speeds, with a 10% reduction at 6 cm s⁻¹, but a 4% increase at 21 cm s⁻¹. Regardless of damage, F _v/F _m at 21 cm s⁻¹ was 11% lower at 26.7°C than at 29.6°C, but was unaffected by temperature at 6 cm s⁻¹. The lesions declined in area at similar rates (4–5% day⁻¹) under all conditions, although the tissue within them regained a normal appearance most rapidly at 26.7°C and 6 cm s⁻¹. These findings show that the response of poritid corals to sub-lethal damage is dependent partly on abiotic conditions, and they are consistent with the hypothesis that following damage, calcification and photosynthesis can compete for metabolites necessary for repair, with the outcome affected by flow-mediated mass transfer. These results may shed light upon the ways in which poritid corals respond to biting by certain corallivorous fishes.     

Vertical infiltration of fuel oil hydrocarbons in an agricultural soil

The influence of rainfall, air temperature and soil moisture on the vertical mobility in the soil of fuel oil hydrocarbons (HC) was investigated in a field experiment. A controlled spreading of fuel oil (nC10‐nC25) was performed at a rate of 5 L HCm^‐2 on an agricultural soil in summer and in winter. Concentration, chemical composition of HC and soil moisture were regularly determined at different soil depths between 0 and 140 cm, 1 h, 3, 8and 15 days (d) after the spreading of oil. Sorption of hydrocarbons onto the organo‐mineral matrix of the soil was studied in laboratory experiments. The results showed that in summer, with an air temperature of 24°C and without water leaching in the soil profile, 65% of the initial HC remained trapped in the 0–140 cm soil layer, about 20% of the HC volatilized and around 15% migrated deeper. A vertical selective migration of the lightest (nC10‐nC15) HC (naphthas) was shown lSd after the spreading of fuel oil. Naphthas progressively reached the 120–140 cm soil layers whereas the heavy fractions of oil (nC17‐nC25) migrated and concentrated in the 0–60 cm soil layers. In winter, when soil was regularly watered by rainfalls and at low air temperatures, only 47% of the initial HC remained in the 0–140 cm profile after 15 d. A fast vertical infiltration of naphthas occurred within the first 3 d. After 15 d, all HC were detected in the same relative amounts as in the initial oil in the whole profile. Volatilization was negligible in winter and an increase in the migration of total oil at depth in the soil profile was shown. As inferred from the laboratory experiments, the high soil moisture led to the decrease in HC sorption on the organo‐mineral matter of the soil.     

Bioenergetics of ephyra larvae of the scyphozoan jellyfish Aurelia aurita in relation to temperature and salinity

The body mass of Aurelia aurita ephyrae was better correlated with the diameter of the central disc than with the distance between opposite rhopaliae or distance between opposite lappet tips. Body dry weight (y, in μg) related to the disc diameter (x, in mm) through the equation y = 22.33 x ^1.99. The exponent 1.99 was significantly lower than that for the medusa stage, indicating a tendency to grow in diameter rather than in weight through the ephyra stage. The average ash-free dry weight (AFDW) of ephyrae was 38.0% of the dry weight. The AFDW/diameter relationship was used to convert measured diameters to body AFDW and calculate succession in body mass, daily ration, daily growth rate and gross growth efficiency. Effects of temperature (6, 9.5, 12, 15 and 18 °C) and salinity (17.5, 22, 26, 30.5 and 35 PSU) on these parameters and feeding were studied at saturated prey concentration (222 Artemia nauplii l⁻¹ initial concentration) by daily measurements over 10 d. There was a strong effect of temperature for total ingestion, growth rate, growth efficiency and final body mass of individual ephyrae, whereas the daily ration was not significantly different between the different temperatures. The experimental group kept at the highest temperature (18 °C) diverged the most, and ephyrae at this temperature ingested 2.7 times more and increased in weight 5.4 times more than at 6 °C. The average daily growth rate and gross growth efficiency of these ephyrae were 34.5% and 25.1%, respectively, significantly higher than at 6, 9.5 and 15 °C. Significant effects of salinity were shown for total ingestion, daily ration, daily growth rate and final weight, although only total ingestion and daily ration diverged sufficiently to show effects in a post-hoc test. This test showed that total ingestion was significantly different for all salinities except between 22 and 35 PSU and between 17.5 and 26 PSU. The daily ration for 35 PSU diverged from all other salinities, whereas none of the other salinities showed any significant differences. Thus, provided food in excess A. aurita can double its weight every 2 to 4 d, dependent on temperature and can therefore develop to the medusa stage in short time. Differences in environmental salinity in the range 17.5 to 35 PSU have little or no effect on growth rate and growth efficiency, whereas our results indicate that the full seawater salinity (35 PSU) causes significantly higher ingestion rate compared to lower salinities. Received: 11 January 1999 / Accepted: 11 May 1999     

In vitro Methylation of Arsenite in Flemish giant rabbit Cytosol

The formation of ⁷⁴As‐monomethyIarsonic acid and ⁷⁴As‐dimethylarsinic acid from carrier‐free radiolabelled ⁷⁴As‐arsenite was evaluated in an assay mixture containing 17.6% liver cytosol from the Flemish Giant rabbit. The optimal incubation temperature and pH were respectively, 39°C and 7.6. After a 2h incubation about 90% of ⁷⁴As was protein bound. Protein bound ⁷⁴As was released by hot 2 M HNO₃ (1 min, 110°C). The treatment did not destroy methylated As‐species. Up to 70% of the carrier‐free ⁷⁴As‐arsenite was methylated. Liver cytosol was stored, without loss of activity, in liquid nitrogen in the presence of 2 mM glutathione. The optimal s‐adenosyl‐methionine concentration was 1.7mM. Formation of ⁷⁴As‐monomethylarsonic acid and ⁷⁴As‐dimethylarsinic acid increased up to a glutathione concentration of respectively 10 and 20 mM. Methylation also went through in the presence of other reducing agents and proved to be ATP dependent.     

The effects of temperature and salinity on reproductive success of <Emphasis Type="Italic">Temora longicornis</Emphasis> in the Baltic Sea: a copepod coping with a tough situation

At specific locations within the Baltic Sea, thermoclines and haloclines can create rapid spatial and temporal changes in temperature (T) and salinity (S) exceeding 10°C and 9 psu with seasonal ranges in temperature exceeding 20°C. These wide ranges in abiotic factors affect the distribution and abundance of Baltic Sea copepods via species-specific, physiological-based impacts on vital rates. In this laboratory study, we characterized the influence of T and S on aspects of reproductive success and naupliar survival of a southwestern Baltic population of Temora longicornis (Copepoda: Calanoida). First, using ad libitum feeding conditions, we measured egg production (EP, no. of eggs female⁻¹ day⁻¹) at 12 different temperatures between 2.5 and 24°C, observing the highest mean EP at 16.9°C (12 eggs female⁻¹ day⁻¹). Next, the effect of S on EP and hatching success (HS, %) was quantified at 12°C for cohorts that had been acclimated to either 8, 14, 20 or 26 psu and tested at each of five salinities (8, 14, 20, 26 and 32 psu). The mean EP was highest for (and maximum EP similar among) 14, 20 and 26 psu cohorts when tested at their acclimation salinity whereas EP was lower at other salinities. For adults reared at 8 psu, a commonly encountered salinity in Baltic surface waters, EP was relatively low at all test salinities—a pattern indicative of osmotic stress. When incubated at 12°C and 15 different salinities between 0 and 34 psu, HS increased asymptotically with increasing S and was maximal (82.6–84.3%) between 24 and 26 psu. However, HS did depend upon the adult acclimation salinity. Finally, the 48-h survival of nauplii hatched and reared at 14 psu at one of six different temperatures (10, 12, 14, 16, 18 and 20°C) was measured after exposure to a novel salinity (either 7 or 20 psu). Upon exposure to 7 psu, 48-h naupliar mortality increased with increasing temperature, ranging from 26.7% at 10°C to 63.2% at 20°C. In contrast, after exposure to 20 psu, mortality was relatively low at all temperatures (1.7% at 10°C and ≤26.7% for all other temperatures). An intra-specific comparison of EP for three different T. longicornis populations revealed markedly different temperature optima and clearly demonstrated the negative impact of brackish (Baltic) salinities. Our results provide estimates of reproductive success and early survival of T. longicornis to the wide ranges of temperatures and salinities that will aid ongoing biophysical modeling examining climate impacts on this species within the Baltic Sea.     

Importance of cysts in the population dynamics of the red tide flagellate Heterosigma akashiwo (Raphidophyceae)

To elucidate roles of cysts in occurrences of Heterosigma akashiwo blooms, cyst dynamics were studied in northern Hiroshima Bay, the Seto Inland Sea of Japan, where H. akashiwo regularly forms red tide in June. Monthly measurements of seasonal changes in the densities of vegetative cells of H. akashiwo and their germinable cysts in surface sediments (top 1-cm layer) were made for 2 years at three stations. Vegetative cells of H. akashiwo could be detected from April through December throughout the water column, and the existence of vegetative cells was confirmed in surface waters even in winter after incubation of sampled seawater in culture medium. Germinable cysts, enumerated by the extinction dilution method, existed in sediments in all seasons, even before and after the seasonal bloom. The effects of incubation temperature on the germination of natural cysts of H. akashiwo in sediments were examined. Germination was not observed at 5 °C, was low at 10 °C, while it increased at 15 °C, and maintained a high level to 25 °C. The bottom water temperature reached 15 °C (suitable for the germination of cysts) and the surface about 18 °C or more (suitable for the growth of vegetative cells) 2 to 3 weeks before the blooms. The dark survival of H. akashiwo cysts was tested, and it was found that the cysts were viable for at least 650 d at 11 °C, and for 165 d at 25 °C, indicating a significant role of cysts in the survival during winter and summer seasons. The cysts presumably also play an important role in seeding primary populations into water columns when the bottom water reaches a suitable temperature (around 15 °C); thereafter the populations develop with great annual regularity to bloom in June. These results suggest that initiation of H. akashiwo red tides in the Seto Inland Sea could be triggered by bottom water temperature. Received: 3 July 1998 / Accepted: 12 January 1999     

Enhanced desorption of fluoxetine from polyethylene terephthalate microplastics in gastric fluid and sea water

There are concerns that microplastics act as a vector of pharmaceuticals in the aquatic environment. Most studies have focussed on pharmaceutical adsorption and have not investigated desorption in the various matrices that microplastics enter. Therefore we studied the desorption of the antidepressant drug fluoxetine from polyethylene terephthalate (PET) microplastics in river water, sea water, and simulated gastric and intestinal fluids. We found that most desorption occurred rapidly, within a few hours of exposure. Fluoxetine desorption fitted well to the Freundlich isotherm with r² values ranging from 0.97 to 0.99. Desorption decreased in the following order: gastric fluid at 20 °C and 37 °C; sea water at 20 °C; intestinal fluid at 20 °C and 37 °C; then river water at 20 °C. The little difference in desorption in gastrointestinal fluids at 20 °C and 37 °C suggests a similar exposure risk to cold- and warm-blooded organisms following PET microplastic ingestion. Total desorption following sequential incubation 2 h in gastric fluid then 4 h in intestinal fluid to mimic gastrointestinal digestion was 37% at 20 °C and 41% at 37 °C. Interestingly, higher desorption of 18–23% occurred in sea water compared to river water, of 4–11%. Under a worst-case scenario, more than 44 mg kg⁻¹ body weight d⁻¹ or more than 52 mg kg⁻¹ body weight d⁻¹ of PET microplastics from river water or sea water, respectively, need to be consumed to exceed the mammalian acceptable daily intake for fluoxetine. Further studies are needed on microplastic ingestion and the bioavailability of adsorbed pharmaceuticals to a range of exposed aquatic organisms.

     

Temperature cues gametogenesis and larval release in a tropical sponge

Determining the reproductive processes of benthic invertebrates is central to our understanding of their recruitment and population dynamics. Sexual reproduction of the gonochoric and viviparous Great Barrier Reef sponge, Luffariella variabilis (Poléjaeff 1884) was quantified from histological samples collected over two reproductive seasons (2004 and 2005). Gametogenesis commenced for females at a water temperature of 21°C, the lowest water temperature of the year. Spermatogenesis occurred above 22.5°C with sperm asynchronously developed and released from August or September to October. Oocytes developed asynchronously from July to September, embryos from September to December, and larvae from November to December. Female reproduction terminated in December (after larval release) prior to the highest mean annual water temperature of 30°C in January. There was a significant (35%) decrease in female reproductive output in 2005 compared to 2004, as measured by the reproductive index (0.68 ± 0.12 female reproductive propagules mm⁻² of mesohyl in 2005 compared with 1.05 ± 0.10 mm⁻² in 2004). This corresponded with delayed oogenesis and spermatogenesis, and a shortened larval development cycle corresponding with a delayed minimum temperature (21°C) in August of 2005 compared with July 2004. Accordingly, the maximum percentage of the mesohyl occupied by female reproductive propagules (eggs, embryos and larvae) was also reduced by 60% in 2005 (overall mean of 13.04% in October 2004 compared with 5.35% in October 2005). However, the mean sizes of individual female propagules remained the same from year to year. Males in contrast, showed no overall difference in either reproductive index or percentage occupation of the mesohyl between 2004 and 2005. The lowered reproductive output (∼35%) of females of L. variabilis associated with delayed minimum water temperatures may have important implications for population reproductive success where oogenesis and spermatogenesis and larval release are cued by minimum and maximum water temperatures, respectively.