Petroleum ingestion reduces reproduction in Cassin's Auklets

Sublethal doses of petroleum reduced reproduction in a free-living seabird, Cassin's Auklet (Ptychoramphus aleuticus), nesting on Southeast Farallon Island, California. The proportion of birds laying eggs was reduced 9–13 days after ingestion by gelatin capsule of 300, 600 or 1000 mg bunker C fuel oil, or 1000 mg Prudhoe Bay crude oil. In addition, among those auklets that eventually laid eggs, hatching was reduced by doses of 1000 mg of bunker C but was unaffected by other treatments. Chick development after hatching was unaffected by any treatment. The total time of egg formation from onset of rapid yolk formation to laying was 13 days, and it is early in this period that auklets are vulnerable to petroleum.     

Hypoxia impairs embryo development and survival in black bream (Acanthopagrus butcheri)

Coastal environments are threatened by the increasing frequency, extent and severity of hypoxic events. Hypoxia affects vast areas around the world and often causes fish kills, reduced abundance, altered distribution, low benthic biomass and declines in fisheries. In Australia, many fisheries are based on sparid fishes and in the southern states black bream (Acanthopagrus butcheri) is important to both the recreational and commercial sectors. This species completes its entire life cycle in estuaries and annual recruitment is highly variable and very likely influenced by environmental conditions during the spawning season.In a laboratory-based experiment, fertilised black bream eggs (embryos) were exposed to five different levels of dissolved oxygen (DO). The DO levels were maintained in small test wells using nitrogen gas in a novel chamber design. Embryo development was assessed over a 2-day period and hatched larvae were observed until Day 2 post-hatch. Significant differences (p < 0.05) were observed in embryonic development and survival as a function of DO level. In severely hypoxic conditions (30% saturation) survival to 1 day was reduced and no hatching occurred. In moderately hypoxic conditions (45–55%S), both precocious and delayed hatching was observed and hatch rates were reduced, whilst the number of hatched larvae with deformities increased, resulting in reduced larval lengths. No larvae survived to Day 2 post-hatch when held in hypoxic conditions (<55%S). This study demonstrates the detrimental effect that severe hypoxia can have on the early development of black bream which could result in reduced recruitment and lowered abundance. Other species that share similar early life histories may also be at risk.     

Detrimental effects of reduced seawater pH on the early development of the Pacific abalone

The hatching process of the Pacific abalone Haliotis discus hannai was prolonged at a pH of 7.6 and pH 7.3, and the embryonic developmental success was reduced. The hatching rate at pH 7.3 was significantly (10.8%) lower than that of the control (pH 8.2). The malformation rates at pH 7.9 and pH 8.2 were less than 20% but were 53.8% and 77.3% at pH 7.6 and pH 7.3, respectively. When newly hatched larvae were incubated for 48 h at pH 7.3, only 2.7% of the larvae settled, while more than 70% of the larvae completed settlement in the other three pH treatments. However, most 24 h old larvae could complete metamorphosis in all four pH treatments. Overall, a 0.3-unit reduction in water pH will produce no negative effect on the early development of the Pacific abalone, but further reduction in pH to the values predicted for seawater by the end of this century will have strong detrimental effects.     

Effect of ammonium jarosite on early life stages of a saltwater fish,Cyprinodon variegatus

Embryos and juveniles of the sheepshead minnow (Cyprinodon variegatus), a saltwater fish, were exposed to ammonium jarosite, a waste product of the processing of zinc ore, during a 28-day posthatch, flow-through toxicity test. Exposure to measured ammonium jarosite concentrations ≤ 290 ppm had no significant effect on the hatching success of embryos. However, slight delays in hatching were observed in test concentrations ≥ 140 ppm. Although exposure to test concentrations ≥ 140 ppm significantly decreased the ability of juvenile fish to uncurl after hatching, juvenile mortality was significantly increased only in test concentrations ≥ 230 ppm. There was no effect on growth of juvenile fish in jarosite concentrations ≤ 230 ppm. The estimated maximum acceptable toxicant concentration (MATC), based on measured concentrations, was > 140< 230 ppm.     

Effects of elevated CO2 on the reproduction of two calanoid copepods

Some planktonic groups suffer negative effects from ocean acidification (OA), although copepods might be less sensitive. We investigated the effect of predicted CO₂ levels (range 480–750 ppm), on egg production and hatching success of two copepod species, Centropages typicus and Temora longicornis. In these short-term incubations there was no significant effect of high CO₂ on these parameters. Additionally a very high CO₂ treatment, (CO₂ = 9830 ppm), representative of carbon capture and storage scenarios, resulted in a reduction of egg production rate and hatching success of C. typicus, but not T. longicornis. In conclusion, reproduction of C. typicus was more sensitive to acute elevated seawater CO₂ than that of T. longicornis, but neither species was affected by exposure to CO₂ levels predicted for the year 2100. The duration and seasonal timing of exposures to high pCO₂, however, might have a significant effect on the reproduction success of calanoid copepods.     

The effect of CO2 acidified sea water and reduced salinity on aspects of the embryonic development of the amphipod Echinogammarus marinus (Leach)

We investigated the effect of CO₂ acidified sea water (S = 35, 22 and 10_PSU) on embryonic development of the intertidal amphipod Echinogammarus marinus (Leach). Low pH, but not low salinity (22_PSU), resulted in a more protracted embryonic development in situ although the effect was only evident at low salinity. However reduced salinity, not pH, exerted a strong significant effect, on numbers and calcium content of hatchlings. Females exposed to low salinity (10_PSU) did not carry eggs through to hatching. There was no significant difference in the number of viable hatchlings between females cultured in 22 and 35_PSU but the exoskeleton of the juveniles at 22_PSU contained significantly less calcium. Ocean acidification may affect aspects of E. marinus development but exposure to realistic low salinities appear, in the short term, to be more important in impacting development than exposure to CO₂ acidified sea water at levels predicted for 300 years time.     

The Influence of the Incubation Temperature on the Body Length and the Yolk Sac Volume of Coregonus albula (L.) Eleutheroembryos

Eggs of Coregonus albula were incubated at temperatures of 1.1, 2.0, 4.9, 6.6, 8.4 and 9.9 °C. The successful hatching is optimum with 61 % at 4.9 °C; incubation time and period of hatching decrease significantly with rising temperature. The length of eleutheroembryos decreases with rising temperature, the yolk sac volume increases. Between the incubation time till hatching and the body length a significantly positive regression exists in the range of 4.9… 8.4 °C, for the yolk sac volume the regression is negative, it is significant in the range of 2.9… 6.6 °C; at the same time a negative regression exists between the yolk sac volume and the body length. Thus, low temperatures cause a delay of hatching, higher temperatures accelerate hatching and at the same time result in a reduced utilization of the yolk reserves. Besides these influences of temperature on the rate of ontogenetic processes, some autoecological consequences of the influence of temperature result, which have to be taken into account in further investigations.     

Why are hatching and emergence success low? Mercury and selenium concentrations in nesting leatherback sea turtles (Dermochelys coriacea) and their young in Florida

Leatherback sea turtles (Dermochelys coriacea) have low hatching and emergence success compared to other sea turtle species. Postmortem examinations of hatchlings showed degeneration of heart and skeletal muscle that was similar to that found in other neonates with selenium deficient mothers. Selenium deficiency can result from elevated concentrations of bodily mercury. Ingested mercury is detoxified by the liver through mercury-selenium compound formation. In animals persistently exposed to mercury, the liver’s ability to detoxify this element may decrease, especially if dietary selenium is insufficient. We measured mercury and selenium concentrations in nesting female leatherbacks and their hatchlings from Florida and compared the levels to hatching and emergence success. Both liver selenium and the liver selenium-to-mercury ratio positively correlated with leatherback hatching and emergence success. This study provides the first evidence for the roles of mercury and selenium in explaining low reproductive success in a globally imperiled species, the leatherback sea turtle.     

Chronic exposure of adults and embryos of Pandalus borealis to oil causes PAH accumulation, initiation of biomarker responses and an increase in larval mortality

Adult shrimps (Pandalus borealis) and their embryos were exposed to an oil-water dispersion (OWD) at concentrations of 0.015, 0.06 and 0.25 mg/L using a continuous flow system. Lysosomal membrane stability was analysed in haemocytes using the neutral red retention assay and an alkaline unwinding assay was used to measure DNA damage in hepatopancreas tissue. Exposure to oil induced concentration and time dependent biomarker responses in adult shrimps together with the accumulation of PAH in their tissues. Oil exposure of shrimp embryos caused increased mortality in the resultant larvae, even if the larvae were kept in clean water after hatching. There were minor differences observed in larval stage development times in the first part of the experiments. The fatty acid composition of embryos exposed to oil was different to that of non-exposed larvae. PAH tissue concentration and biomarker responses correlated to the reduced survival of the shrimp larvae.     

A mesocosm experiment investigating the effects of substratum quality and wave exposure on the survival of fish eggs

In a mesocosm experiment, the attachment of bream (Abramis brama) eggs to spawning substrata with and without periphytic biofilm coverage and their subsequent survival with and without low-intensity wave exposure were investigated. Egg attachment was reduced by 73% on spawning substrata with a natural periphytic biofilm, compared to clean substrata. Overall, this initial difference in egg numbers persisted until hatching. The difference in egg numbers was even increased in the wave treatment, while it was reduced in the no-wave control treatment. Exposure to a low-intensity wave regime affected egg development between the two biofilm treatments differently. Waves enhanced egg survival on substrata without a biofilm but reduced the survival of eggs on substrata with biofilm coverage. In the treatment combining biofilm-covered substrata and waves, no attached eggs survived until hatching. In all treatments, more than 75% of the eggs became detached from the spawning substrata during the egg incubation period, and <1% of these detached eggs survived within the substratum interstices. Hence, detached eggs contributed little to the reproductive success we observed. The implications of these results on the spawning success of fish species that use freshly inundated spawning substrata in shallow waters are discussed.     

Effects on hatching in Littorina littorea after an oil spill

One year after an accidental spill of approx. 2000 t of Iranian crude oil on the west coast of Norway, specimens of the gastropod Littorina littorea were collected from the oil polluted shore and allowed to spawn in the laboratory. Snails were also collected from an unpolluted reference site. The oil contamination seemed to have no detectable effects on fertilization. However, the hatching success of the veliger larvae was significally less in the ‘oil polluted’ population. Some highly abnormal eggs were also observed in this egg population.     

Hypoxia impairs embryo development and survival in black bream (Acanthopagrus butcheri)

Coastal environments are threatened by the increasing frequency, extent and severity of hypoxic events. Hypoxia affects vast areas around the world and often causes fish kills, reduced abundance, altered distribution, low benthic biomass and declines in fisheries. In Australia, many fisheries are based on sparid fishes and in the southern states black bream (Acanthopagrus butcheri) is important to both the recreational and commercial sectors. This species completes its entire life cycle in estuaries and annual recruitment is highly variable and very likely influenced by environmental conditions during the spawning season.In a laboratory-based experiment, fertilised black bream eggs (embryos) were exposed to five different levels of dissolved oxygen (DO). The DO levels were maintained in small test wells using nitrogen gas in a novel chamber design. Embryo development was assessed over a 2-day period and hatched larvae were observed until Day 2 post-hatch. Significant differences (p < 0.05) were observed in embryonic development and survival as a function of DO level. In severely hypoxic conditions (30% saturation) survival to 1 day was reduced and no hatching occurred. In moderately hypoxic conditions (45–55%S), both precocious and delayed hatching was observed and hatch rates were reduced, whilst the number of hatched larvae with deformities increased, resulting in reduced larval lengths. No larvae survived to Day 2 post-hatch when held in hypoxic conditions (<55%S). This study demonstrates the detrimental effect that severe hypoxia can have on the early development of black bream which could result in reduced recruitment and lowered abundance. Other species that share similar early life histories may also be at risk.     

Polybrominated diphenyl ethers do not affect metamorphosis but alter the proteome of the invasive slipper limpet Crepidula onyx

Man-made polybrominated diphenyl ethers (PBDEs) used as flame retardants in various consumer products may be harmful to marine organisms. Larvae of some marine invertebrates, especially invasive species, can develop resistance to PBDEs through altered protein expression patterns or proteome plasticity. This is the first report of a proteomics approach to study BDE-47 induced molecular changes in the invasive limpet Crepidula onyx. Larvae of C. onyx were cultured for 5 days (hatching to metamorphosis) in the presence of BDE-47 (1 μg L⁻¹). Using a 2-DE proteomics approach with triple quadrupole and high-resolution TOF-MS, we showed that BDE-47 altered the proteome structure but not the growth or metamorphosis of C. onyx larvae. We found eight significant differentially expressed proteins in response to BDE-47, deemed the protein expression signature, consisting of cytoskeletal, stress tolerance, metabolism and energy production related proteins. Our data suggest C. onyx larvae have adequate proteome plasticity to tolerate BDE-47 toxicity.     

Differences in life table demography among eight geographic populations of Brachionus calyciflorus (Rotifera) from China

Eight geographic populations of Brachionus calyciflorus collected from China in August 2007 were cultured at 18 °C, 23 °C and 28 °C with 3.0×10⁶ cells mL⁻¹ of alga Scenedesmus obliquus to investigate their differences in life table demography. The results showed that the response in each of the life table demographic parameters (age-specific survivorship and fecundity, life expectancy at hatching, generation time, net reproductive rate, intrinsic rate of population increase and proportion of sexual offspring) to increasing temperature differed with geographic population. Life expectancy at hatching, generation time, net reproductive rate and intrinsic rate of population increase were all significantly influenced by temperature, geographic population and their interaction and indirectly affected by the changes in body size and egg volume of the rotifers; however, the proportion of sexual offspring produced by the rotifers was markedly influenced only by geographic population. Among all the combinations of temperature and geographic population, the generation times of Guangzhou and Hainan populations at 18 °C were the longest, and the intrinsic rate of population increase of the Tai’an population at 18 °C was the lowest. Among all the eight geographic populations, the proportion of sexual offspring produced by Xuzhou population was the highest. Although the higher proportions of sexual offspring produced by all the geographic populations of rotifers (9.7-41.1%) might lead to higher resting egg productions, and thus to wide spread of the rotifers among the eight geographic populations, their differences in life table demography might be regarded as the results of adaptation to the different environmental conditions faced by them in the field.     

Hypoxia impairs embryo development and survival in black bream (Acanthopagrus butcheri)

Coastal environments are threatened by the increasing frequency, extent and severity of hypoxic events. Hypoxia affects vast areas around the world and often causes fish kills, reduced abundance, altered distribution, low benthic biomass and declines in fisheries. In Australia, many fisheries are based on sparid fishes and in the southern states black bream (Acanthopagrus butcheri) is important to both the recreational and commercial sectors. This species completes its entire life cycle in estuaries and annual recruitment is highly variable and very likely influenced by environmental conditions during the spawning season. In a laboratory-based experiment, fertilised black bream eggs (embryos) were exposed to five different levels of dissolved oxygen (DO). The DO levels were maintained in small test wells using nitrogen gas in a novel chamber design. Embryo development was assessed over a 2-day period and hatched larvae were observed until Day 2 post-hatch. Significant differences (p<0.05) were observed in embryonic development and survival as a function of DO level. In severely hypoxic conditions (30% saturation) survival to 1 day was reduced and no hatching occurred. In moderately hypoxic conditions (45-55%S), both precocious and delayed hatching was observed and hatch rates were reduced, whilst the number of hatched larvae with deformities increased, resulting in reduced larval lengths. No larvae survived to Day 2 post-hatch when held in hypoxic conditions (<55%S). This study demonstrates the detrimental effect that severe hypoxia can have on the early development of black bream which could result in reduced recruitment and lowered abundance. Other species that share similar early life histories may also be at risk.     

Artificial light at night: implications for early life stages development in four temperate freshwater fish species

Flora and fauna have both evolved under a natural cycle of light and dark. But especially in urban areas, the night is now increasingly disturbed by artificial light. Many traits and behaviours in fish are triggered by a circadian clock, for example hatching and swim bladder inflation, which predominantly take place at dusk or night. As lighting becomes brighter and extends farther into rural areas, the distinction between day and night becomes increasingly blurred. Therefore, the loss of diurnal trigger by artificial light at night was hypothesized having deleterious effects on these traits and impact fish reproduction. To assess these effects, eggs of four native freshwater fishes, Eurasian perch Perca fluviatilis, roach Rutilus rutilus, bleak Alburnus alburnus and chub Leuciscus cephalus, were incubated under two different light conditions: a photoperiod of 14 h light:10 h darkness (LD) and continuous illumination (LL). The time to hatch and swim bladder inflation was recorded. The species showed inconsistent reactions to the light treatments. In roach and bleak, the time to 50% hatch was longer in LL, whereas continuous lighting had an accelerating effect in chub. Incubation in LL elongated the hatching period in perch and roach and, in perch, the onset of darkness seemed to trigger hatching. The swim bladder inflation was significantly promoted by continuous light in chub and bleak but was not affected in roach. In conclusion, nocturnal artificial illumination could have an effect on hatching and initial swim bladder filling by masking the day–night-change and thereby diminish the trigger effect. However, the reactions were species specific and the increase in variation indicated a lack of diurnal triggering, whilst a general deleterious effect of artificial light at night has not been identified on early life stages.     

Incubation,hatching and survival of eggs of Atlantic salmon (Salmo salar) in spawning redds influenced by groundwater

Many west coastal and northern Norwegian rivers run through deep, confined valleys with permeable layers of glacial and alluvial deposits. Groundwater flows through these permeable layers and enter lakes and rivers as underwater seepage and springs. Groundwater inflow to inland Norwegian rivers may constitute 40–100% of total water discharge during low flow periods in late summer and winter. Juvenile salmonids may take advantage of groundwater upwellings and actively seek out such patches. In regulated rivers groundwater influx may create refuges during low flow or hydropeaking episodes. The importance of groundwater for salmon redd site selection and egg survival is also clear, although less known and documented in regulated rivers.Eggs of Atlantic salmon (Salmo salar) are deposited in redds in river bed gravels lacking fine sediments and with high oxygen levels. Egg development is therefore dependent on the interaction of a number of environmental factors such as groundwater influx, oxygen and temperature. Atlantic salmon in the regulated River Suldalslågen, Western Norway, spawn relatively late compared to other Norwegian rivers, with a peak in early January. Newly emerged fry are found from the end of May to the beginning of June, i.e. “swim up” one month earlier than expected using models for egg and alevin development and river water temperatures. The most plausible explanation is that groundwater has a higher and more stable temperature than surface river water. In field experiments, fertilized salmon eggs were placed in boxes close to natural spawning redds in the river bed at sites influenced and those not influenced by groundwater. A difference of up to 40 days in 50% hatching was found, and “swim up” occurred at the end of May in boxes influenced by groundwater.Preliminary studies have revealed that groundwater also plays an important role in survival of salmon eggs in the River Suldalslågen when dewatered in winter. Eggs placed in boxes in groundwater seepage areas during winter in the dewatered river bed survived even when covered by ice and snow. The survival from fertilization until 30 April, one month before hatching, was 91%, the same survival as found for eggs placed in boxes in the wetted river bed. However, mortality from fertilization to hatching was higher compared to the eggs placed in wetted river bed, 57 and 91% respectively.Groundwater creates a horizontal and vertical mosaic of temperatures in spawning redd areas leading to potentially greater variation in spawning sites, time of hatching and “swim up”. This is likely to increase egg survival during low flow periods in regulated rivers. In conclusion, the interaction between groundwater and surface river water should therefore be considered when managing fish populations in regulated rivers.     

Predation effects of benthivorous fish on grazing and shredding macroinvertebrates in a detritus-based stream food web

We investigated lethal and sublethal predation effects of the benthivorous gudgeon (Gobio gobio) on the grazing mayfly Rhithrogena semicolorata and the shredding amphipod Gammarus pulex over 21 months in a largely detritus-based small stream. We hypothesised that shredders are generally less vulnerable to fish predation and therefore less likely to be predation-controlled than grazers, because the latter are visible to the predators during their feeding on stone surfaces, while shredders may hide between leaves during foraging.The hypothesis was tested in two 400 m experimental reaches of a natural stream, which were manipulated in order to contain and to lack fish, respectively. Biomass of G. pulex was significantly reduced in the fish section while that of R. semicolorata was not. Since approximately 91% of the annual production of G. pulex but only 12% of R. semicolorata production was consumed by gudgeon, the observed biomass difference of G. pulex is likely due to a lethal predation effect. However, no sublethal predation effects such as reduced concentration of storage components (triglycerides, glycogen) or reduced reproductive success were observed for both species. Lower mean body length of the R. semicolorata larvae in the fish section did not result in a lower number of eggs in the abdomen of the last instar larvae. Hence, in contrast to our initial hypothesis, in the studied stream the shredder was top-down-controlled, while the grazer was not. It is concluded that top-down control depends on the ecological characteristics of a specific predator-prey pair rather than on trophic guild of the prey.     

The influence of egg size and thermal conditions of incubation on the body length and the yolk sac volume of vendace (Coregonus albula L.) eleutheroembryos

Eggs of C. albula were incubated at 1.5 ° and acclimated for different times to 10 °. This procedure caused a varying delay in their hatching. The percentage of normal hatch and the eleutheroembryos' body length and yolk sac dimensions (height and length) were measured, and the yolk sac volume was calculated. The number of days of hatching delay was positively correlated with the total length of embryos and inversely correlated with their yolk sac volume. Dimensions of vendace embryos emerging from eggs of different size were compared. Larger eggs produced longer embryos equipped with larger yolk sacs, and differences in the yolk sac volume were far more pronounced than differences in the body length.     

A 40-year perspective of an alpine lake: Is everything the same?

Mountain lakes are the most affected by climate change; however, few of these lakes are regularly sampled because of their remoteness. We discussed limnological data (e.g. water temperature, light transparency, and plankton diversity) of Lake Campo (1944 m above sea level, Adamello Mountains, Italy) scattered over almost forty years in the light of climate change. Specifically, occasional samplings in 1980, 1988, 2016, 2017, and 2018 and more extensive surveys in 1997 and 2015 were carried out. Among the investigated years, 2015 was the warmest. Inter-year variability in water temperature was quite marked in Lake Campo. Water temperature profiles of July (1980, 1997, 2015) showed increased surface warming, while the deeper layers (> 15 m) were always isothermal at around 5 °C. Hypolimnetic dissolved oxygen never decreased below 50 % saturation. Secchi disk depth was not substantially different among years. Summer profiles of light transparency showed discontinuous light attenuation, which was tentatively attributed to algae located in deeper layers. In cluster analysis of phytoplankton and zooplankton data, differences between seasons but not years were found. The autumn decline of Bacillariophyta and the increase of mixotrophic Cryptophyta was linked to decreasing silica concentrations towards autumn. Apart from this general pattern, several observations (e.g. high abundance of Tovellia sanguinea, requiring warmer temperatures and thermal stratification to compete with Bacillariophyta; a spatially extended metalimnetic oxygen maximum in July 2015) showed the effects of particularly warm conditions of 2015 compared to 1997. The continuous presence of crustacean males and first generation of rotifers (Polyarthra f. aptera) hatching from sexual eggs indicated the importance of sexual reproduction in the lake. Length measurements of Daphnia gr. longispina before (1997) and after (2015) non-native fish removal and Arctic char introduction were similar and indicated no apparent change in predation pressure. Studies like this, despite scattered data, can provide valuable insights into the changes mountain lakes undergo through time.