The combined effect of salinity,temperature and oil on the growth pattern of embryos of the killifish, Fundulus heteroclitus Walbaum

Embryos of the estuarine teleost, Fundulus heteroclitus, were exposed during development to different concentrations of the water-soluble fractions (WSF) of a No. 2 fuel oil under various temperature-salinity combinations. Temperatures and salinities were, respectively: 20, 25 or 30°C and 10, 20 or 30%S. The WSF were extracted from No. 2 fuel oil daily and diluted to concentrations of 15, 20 or 25% of the original mixture. Controls were exposed to seawater without WSF at each temperature-salinity combination.The length of eleutheroembryos was markedly decreased by exposure to WSF. Temperature exerted an effect on growth at low WSF concentrations (0 and 15% WSF) but not at higher ones. The two highest WSF concentrations had a predominant effect on growth that was not further modified by physical factor influences. Conversely, as the WSF exposure increased, the yolk diameter increased, indicating a decreased utilisation of yolk material during development. The mean number of vertebrae in the eleutheroembryos decreased at high WSF concentrations and at high temperatures. Morphological abnormalities consisted predominantly of spinal deformations (scoliosis and lordosis). The data indicate that the survivors of chemical toxicity during embryo development exhibit sublethal responses which would reduce their survival potential in later life.     

Vitellogenin-associated maternal transfer of exogenous and endogenous ligands in the estuarine fish, Fundulus heteroclitus

Sequestration of large quantities of vitellogenin (VTG) is critical for proper oocyte development in most oviparous vertebrates. While previous studies have shown a general correlation between oocyte growth and the accumulation of various exogenous and endogenous ligands, few studies have attempted to elucidate the role VTG plays in this maternal transfer. In the present study, we have demonstrated that oocytic accumulation of [³H]-2,3,7,8-tetrachlorodibenzo-p-dioxin (³H-TCDD) and [¹⁴C]-benzo(a)pyrene (¹⁴C-BaP) by gravid Fundulus heteroclitus is directly correlated with oocyte maturational status. A positive correlation was observed between oocyte maturational state (size) and both total quantity (total pmoles) as well as concentration (pmoles/g tissue) of TCDD and BaP. Further, the bi-phasic accumulation of both TCDD and BaP mirrors that previously observed for protein sequestration by cultured Fundulus oocytes. Additionally, both TCDD and BaP were associated with VTG in vivo. HPLC analysis of serum extracts has shown that VTG associates with both parent BaP and BaP metabolites. Studies with ¹²⁵I-T₄ (thyroxine) also suggest that this critical hormone also associates with VTG in vivo. Ongoing studies are examining the VTG-associated transport and oocytic sequestration of ¹²⁵I-T₄ in gravid Fundulus.     

Liver cadmium uptake,catalase inhibition and cadmium thionein production in the killifish (Fundulus Heteroclitus) induced by experimental cadmium exposure

Liver catalase activity was used as an index of cadmium poisoning in the killifish, Fundulus heteroclitus, and was found to be inhibited following both in vivo and in vitro exposure to dissolved cadmium at a concentration greater than 1 mg/litre. Pre-exposure at 1 mg Cd/litre prevented catalase inhibition at higher subsequent doses of cadmium. Comparison of the effects of in vivo and in vitro exposure showed in vivo exposure to cadmium to result in greater catalase inhibition.Cadmium and copper binding was determined by gel chromatography and found to occur at three distinct liver cytosol fraction peaks. Both metals showed enhanced cytosol concentrations with cadmium exposure and relative changes in peak levels as related to cadmium exposure regimes. Cadmium thionein (molecular weight of 7–10,000) was found in the killifish liver and was correlated with adaptive responses in liver catalase activity. High molecular weight cadmium binding was found to be a better index of cadmium toxicity to liver catalase than total liver cadmium concentration.     

Effects of mercury on the feeding behavior of the mummichog, Fundulus heteroclitus from a polluted habitat

Fish living in contaminated environments may exhibit reduced growth which may be due, in part, to the impact of toxicants on prey capture ability. We studied the effects of methylmercury (meHg) and mercuric chloride (Hg) on feeding of Fundulus heteroclitus from Piles Creek, a polluted habitat in Linden, New Jersey. We found that exposure to 0·01 mg/liter of meHg for one week had less impact on the prey capture rate than exposure to a similar concentration of Hg. Exposure to 0·01 mg/liter for two weeks or to 0·02 mg/liter for one week, of either meHg or Hg, produced significant reductions in feeding rate, compared to controls. In general, the fish were affected to a greater degree by exposure to Hg than to meHg. This is the reverse of the usual order of toxicity, but is in keeping with previous observations on this population, in which we have noted that gametes and embryos had developed tolerance to meHg, but were more susceptible to Hg.     

Hepatic histopathology in two populations of the mummichog, Fundulus heteroclitus

The pollution-tolerant mummichog, Fundulus heteroclitus, inhabits a heavily contaminated estuary, Piles Creek (PC), in Linden, NJ. PC contaminants include PAHs, PCBs and many metals, including high Hg and Pb. PC mummichog livers and kidneys were compared with those from a pristine estuary in Tuckerton (TK), NJ, by standard histopathological methods, with quantification by computerized image analysis. PC livers had>2× the lipid ratios of TK livers. Cell sizes and shapes were not different between populations. TK livers had a 25% incidence of basophilic areas and an age-related 30% incidence of macrophage aggregates; PC livers had none of these lesions. PC livers had a 100% incidence of necrotic foci, compared with 55% of TK livers. Inflammation was noted in 50% of TK livers but only 27% of PC livers. Curiously, the TK livers had a 45% incidence of metacercarial cysts of a digenetic trematode, while none were found in the PC livers. The TK focal necrosis and macrophage aggregates coincided with parasite infestation. There were no observed kidney lesions in either population. Positive biomarkers in this species thus included high hepatic lipid content, possibly necrosis, but no other lesions. The lack of trematode cysts in PC livers may reflect the lack of an intermediate host in this low biodiversity estuary.     

长时间微塑料环境暴露对肉芝软珊瑚的影响

目前海洋微塑料对海洋生物的生存及人类的健康已经造成了严重的影响。为探究微塑料对我国海南岛近海珊瑚礁常见珊瑚肉芝软珊瑚的影响,本实验将肉芝软珊瑚长时间暴露于微塑料环境中,测定在此过程中的虫黄藻密度,叶绿素含量,以及部分关键酶的活性。结果显示:在微塑料胁迫后,共生虫黄藻的密度在第1天开始显著下降,并在15天后达到最低值(1.52±0.06)×106cell/cm2(P0.05);叶绿素含量在50天内显著下降,在第50天时达到最低值3.45±0.35μg/cm2; SOD活性和CAT活性在3天内显著升高,并在第三天达到最高值,分别为34.39±1.33 U/mg prot和34.80±1.51 U/mg prot,此后显著下降;同样GST活性也迅速上升,在第1天和第15天出现两个峰值,分别是1.22±0.04U/mgprot和1.33±0.04 U/mg prot;而ACP与AKP活性也有迅速下降趋势。本实验为研究微塑料环境对珊瑚礁的影响提供数据支持。     

The responses of the estuarine bivalve mollusc Scrobicularia to the first hydrolytic product of the insecticide Sevin®

The effects of 1-naphthol, the first hydrolytic product of the insecticide Sevin^®, have been studied on the estuarine bivalve Scrobicularia. Median lethal times for 5 and 10 mg l^?1 1-naphthol were 15 and 9 days respectively. Final concentrations of 1, 5, 10 and 20 mg l^?1 of 1-naphthol resulted in the immediate contraction of the isolated siphon. The contractions were more pronounced at higher concentrations. Application of the same range of concentrations of 1-naphthol to intact Scrobicularia resulted in valve closure and bradycardia. The similarity between the results of median lethal time experiments and the isolated siphonal and behavioural responses of Scrobicularia indicates the feasibility of the use of the isolated siphon preparations to make rapid assessments of environmental stress conditions.     

In vitro simulation of oxic/suboxic diagenesis in an estuarine fluid mud subjected to redox oscillations

Estuarine turbidity maxima (ETMs) are sites of intense mineralisation of land-derived particulate organic matter (OM), which occurs under oxic/suboxic oscillating conditions owing to repetitive sedimentation and resuspension cycles at tidal and neap-spring time scales. To investigate the biogeochemical processes involved in OM mineralisation in ETMs, an experimental set up was developed to simulate in vitro oxic/anoxic oscillations in turbid waters and to follow the short timescale changes in oxygen, carbon, nitrogen, and manganese concentration and speciation. We present here the results of a 27-day experiment (three oxic periods and two anoxic periods) with an estuarine fluid mud from the Gironde estuary. Time courses of chemical species throughout the experiment evidenced the occurrence of four distinct characteristic periods with very different properties. Steady oxic conditions were characterised by oxygen consumption rates between 10 and 40 μmol L⁻¹ h⁻¹, dissolved inorganic carbon (DIC) production of 9–12 μmol L⁻¹ h⁻¹, very low NH₄⁺ and Mn²⁺ concentrations, and constant NO₃⁻ production rates (0.4 - 0.7 μmol L⁻¹ h⁻¹) due to coupled ammonification and nitrification. The beginning of anoxic periods (24 h following oxic to anoxic switches) showed DIC production rates of 2.5–8.6 μmol L⁻¹ h⁻¹ and very fast NO₃⁻ consumption (5.6–6.3 μmol L⁻¹ h⁻¹) and NH₄⁺ production (1.4–1.5 μmol L⁻¹ h⁻¹). The latter rates were positively correlated to NO₃⁻ concentration and were apparently caused by the predominance of denitrification and dissimilatory nitrate reduction to ammonia. Steady anoxic periods were characterised by constant and low NO₃⁻ concentrations and DIC and NH₄⁺ productions of less than 1.3 and 0.1 μmol L⁻¹ h⁻¹, respectively. Mn²⁺ and CH₄ were produced at constant rates (respectively 0.3 and 0.015 μmol L⁻¹ h⁻¹) throughout the whole anoxic periods and in the presence of nitrate. Finally, reoxidation periods (24–36 h following anoxic to oxic switches) showed rapid NH₄⁺ and Mn²⁺ decreases to zero (1.6 and 0.8–2 μmol L⁻¹ h⁻¹, respectively) and very fast NO₃⁻ production (3 μmol L⁻¹ h⁻¹). This NO₃⁻ production, together with marked transient peaks of dissolved organic carbon a few hours after anoxic to oxic switches, suggested that particulate OM mineralisation was enhanced during these transient reoxidation periods. An analysis based on C and N mass balance suggested that redox oscillation on short time scales (day to week) enhanced OM mineralisation relative to both steady oxic and steady anoxic conditions, making ETMs efficient biogeochemical reactors for the mineralisation of refractory terrestrial OM at the land-sea interface.     

Choice chamber experiments to test the attraction of postflexion Rhabdosargus holubi larvae to water of estuarine and riverine origin

Although the recruitment of larvae and juveniles of marine fishes into estuaries has been well documented, little is known about the factors governing the immigration of estuary-associated marine fishes into estuaries. Fishes have a well-developed sense of smell and it has been suggested by several workers that olfactory cues of freshwater or estuarine origin serve as stimuli, attracting larvae and juveniles of estuary-associated species into estuaries. Attraction of postflexion Rhabdosargus holubi larvae to estuary and river water from the Kowie estuarine system, South Africa, was measured using a rectangular choice chamber. In experiments, conducted during peak recruitment periods, larvae selected estuary and river water with a significantly higher frequency than sea water. This study, the first to assess the possible role of olfaction in the recruitment process of an estuary-associated marine fish species, demonstrates that larvae are able to recognise water from different origins, probably based on odour.     

Feeding preferences of estuarine mysids Neomysis integer and Rhopalophthalmus tartessicus in a temperate estuary (Guadalquivir Estuary,SW Spain)

Mysid shrimps are an important component of estuarine food webs because they play a key role in energy transfer as intermediate prey. We investigated the seasonal, tidal and depth specific variation in the diet of the estuarine mysids Neomysis integer and Rhopalophthalmus tartessicus and explored its implications for the planktonic community structure of a temperate estuary (Guadalquivir Estuary, SW Spain). Neomysis integer is an opportunistic omnivore feeding mainly on mesozooplankton and on members of the detrital–microbial loop, shifting prey seasonally according to availability. In contrast, R. tartessicus showed a more carnivorous diet and shifted its target prey during seasons of low resource availability. Despite statistically significant differences in diet composition, both species shared prey of similar size, particularly juvenile Mesopodopsis slabberi, the most abundant mysid species in this estuary, and copepods. Although these similarities imply inter-specific resource competition, their co-existence is achieved by niche partitioning and spatial segregation: the higher osmoregulatory capacity and foraging plasticity of N. integer confers a broader niche breadth for this species allowing N. integer to inhabit the more stressful oligohaline region of the estuary where R. tartessicus cannot survive. We propose that this mechanism relaxes the potential for competition between N. integer and R. tartessicus.     

Salinity tolerance and osmotic response of the estuarine hermit crab Pagurus maclaughlinae in the Indian River Lagoon,Florida

Pagurus maclaughlinae is the most common hermit in the Indian River Lagoon System. Wide variations in lagoonal salinity make it likely that P. maclaughlinae is euryhaline and that other hermit species in the area are more stenohaline, at least in some stages of their life histories. In a study of salinity tolerance, crabs were held unfed at salinities of 5–50 (25 control) for up to 30 days. Based on survivorship curves, P. maclaughlinae tolerated acute exposure to salinities of 10–45 for up to 18 days, and survivorship up to 30 days at 20–45 equaled or exceeded survivorship of the control. In a study of acclimation, the osmotic pressure of hemolymph was measured after crabs were held in the laboratory for 12, 48, and 96 h acutely exposed to salinities of 10–45. Paired t-tests revealed that the crabs weakly hyperregulated their hemolymph at 45–154 mOsmol above the external medium at all salinities and sampling times, and the osmotic differential of their hemolymph was fully acclimated by 96 h. In a third study, acclimatization of hemolymph was studied on crabs at four field sites that differed in their recent salinity histories. Field-collected crabs weakly regulated their hemolymph 72–84 mOsmol above the external medium at all sites sampled. Performance did not differ by site. The range of salinity tolerance and acclimation of hemolymph of P. maclaughlinae partly explain their wide distribution, and the consistent osmotic differential of its hemolymph indicates that the osmoregulatory ability of this small-bodied species is conserved in populations throughout the lagoon. Although some other larger-bodied hermit species in the region are euryhaline as adults, their tendency to hyperregulate strongly at low salinities possibly adds an energetic burden that, along with their less euryhaline long-lived larvae, might exclude them from the lagoon. Salinity tolerance of larval P. maclaughlinae has yet to be studied.     

24-表油菜素内酯对龙须菜抗高温胁迫的研究

本研究采用不同浓度24-表油菜素内酯处理海洋红藻龙须菜,研究热激胁迫后龙须菜的生长速率、叶绿素荧光参数、抗氧化酶活性、甘露醇、丙二醛、藻胆蛋白含量,以及HSP70、PE、GR基因的相对表达水平变化规律。结果显示,0.1mg/L 24-表油菜素内酯的处理组生长速率最大,显著高于其他处理组及对照组;叶绿素荧光参数Fv/Fm、qP和ΦPSⅡ均随高温逆境时间延长呈现下降趋势,荧光参数NPQ随着高温逆境时间延长呈现先上升后下降的趋势,且处理组各项荧光参数值均高于对照组;处理组的抗氧化酶(SOD和POD)的酶活显著高于对照组;甘露醇及藻胆蛋白含量均在0.1mg/L处理组最高,在第三天达到最大值,而丙二醛含量则在0.1mg/L处理组最低,在第三天达到最小值;处理组HSP70、PE、GR基因的相对表达量均高于对照组,且0.1mg/L处理组各基因表达量最高。以上结果表明24-表油菜素内酯能提高龙须菜的抗高温能力,且0.1mg/L处理组效果最好。     

Sub-lethal effects of metal exposure: physiological and behavioural responses of the estuarine bivalve Macoma balthica

Variation in glycogen concentration, condition index (CI) and filtration activity were measured in the bivalve Macoma balthica buried in sediment and experimentally exposed to cadmium (Cd). The stress due to elevated but sub-lethal concentrations (300 ppb Cd) affected the overall fitness of the organism as all parameters monitored responded significantly. Lower concentrations tested (10, 30 and 100 ppb) only induced a significant decrease in filtration activity, which may play a protective role, enabling the organism to slow down its metabolic activity and preserving the integrity of its reserves (reflected by stable CI and glycogen levels). Hence, the various endpoints selected show different thresholds. Our results also demonstrate that under high exposure, small individuals loose proportionally more glycogen per unit of weight than larger ones, thus confirming the higher sensitivity of small individuals to metal contamination. Furthermore, exposure to intermediate concentration (30 ppb) seems to be beneficial to the small individuals as indicated by their high CI values compared to the control. These results showed thus that non-sigmoidal concentration–response relationship and sizes of individuals should be considered in monitoring programmes and risk assessment.     

Relative importance of estuarine nurseries for species of the genus Diplodus (Sparidae) along the Portuguese coast

The relative importance of estuarine nursery areas for species of the genus Diplodus and their relations with several environmental variables was evaluated along the Portuguese coast. Nine estuarine systems were sampled with beam trawl surveys. Species of the genus Diplodus were only present in estuaries south of the Ria de Aveiro (40°38′). A latitudinal gradient of increasing species richness and abundance towards the south was found. Estuarine nurseries of Diplodus vulgaris, Diplodus sargus and Diplodus puntazzo were characterized by mud substrate, lower salinity and lower dissolved oxygen, with the exception of Ria Formosa. Diplodus bellottii was associated with estuaries with large areas and high volumes, the Tejo and the Sado. Diplodus bellottii nursery grounds were characterized by low depth. Diplodus annularis was associated with seagrass and saltmarsh habitats, certainly because it is the only species of the genus Diplodus which recruits exclusively to seagrass meadows. Diplodus annularis nursery grounds were also characterized by sand substrate, higher salinity and higher dissolved oxygen. Niche breath varied widely amongst species and location. Diplodus vulgaris generally presented the highest values of niche breath, except when D. bellottii was present. Niche overlap was not high, the highest value being that between D. vulgaris and D. sargus in the Mira estuary, with 76% spatial niche overlap. Considerations were made on these species progress towards the north in a climate warming context, taking into account the habitat associations described here.     

Effects of long-term exposure to silver or copper on growth, bioaccumulation and histopathology in the blue mussel Mytilus edulis

The purpose of this study was to determine the long-term accumulation of either silver or copper from low concentrations in seawater by blue mussels, Mytilus edulis. Mussels raised from eggs in the laboratory to the age of 2·5 months (approximately 4·5 mm in length) were continuously exposed to 0, 1, 5 and 10μg/liter of either silver (nitrate) or copper (chloride) and sampled at 12, 18 and 21 months for growth studies, measurements of metal accumulation and histopathological examination.Whole-body soft tissues were analyzed for the presence of both silver and copper, as background levels of copper in the incoming seawater averaged 2–4 μg/liter. Mussels exposed to silver had accumulated significant amounts of silver only at the highest test concentration (10 μg/liter Ag) after 12 months, but at 18 and 21 months significant levels were accumulated at all three test concentrations. Mussels exposed to copper accumulated significant amounts of copper at 5 and 10 μg/liter Cu after all three sampling periods, but not at 1μg/liter. Silver-exposed animals also accumulated significantly greater amounts of copper than control animals.In a comparative study, field-collected juvenile mussels (approximately 16·1 mm in shell length) and adult mussels (approximately 53·4 mm in shell length) were exposed for 12 months to 0, 5, 25 and 50 μg/liter silver only and subsequently sampled for metal-accumulation analyses and growth measurements. Juvenile mussels accumulated significant amounts of silver at all test concentrations, with the exception of mussels exposed to 5 μg/liter Ag for 6 months. Copper accumulation in the silver-exposed juveniles was significant only at 50 μg/liter Ag after 6 months, but at all test concentrations after 12 months. Adult mussels exposed to silver accumulated significant levels of both silver and copper, but at somewhat lower levels than juveniles.In the growth study, silver had no effect on laboratory reared mussels at the highest concentration of 10 μg/liter tested, whereas copper at 10 μg/liter did appear to affect growth as early as 4 months after the start of experimental exposure. Field-collected juvenile mussels did show inhibition in growth after 6 months' exposure to 25 and 50 μg/liter Ag, with some growth occurring after 12 months. Adults also showed inhibition in growth after 6 months but not at 12 months.Histopathological examination of mussels exposed to either 5 or 10 μg/liter of copper for 18 months showed changes in the digestive diverticula, gastrointestinal tract, reproductive tract and muscle tissues. These changes were more noticeable in mussels exposed to 5 μg/liter Cu than in those exposed to 10 μg/liter. Mussels exposed to silver for 21 months showed yellowish to black particulate deposition in the basement membrane and connective tissue of the various organs and tissues. Silver deposition increased with increasing test concentration.     

Simulating a heavy metal spill under estuarine conditions: Effects on the clam Scrobicularia plana

We describe the effect of heavy metals Zn, Cd, Pb and Cu on the induction of methallothioneins on the clam Scrobicularia plana along a salinity gradient simulated under laboratory conditions. The clams were exposed to constant heavy metal concentrations in a dynamic estuary simulator during a 15-day assay to investigate possible induction of metal-binding proteins in them. The concentration of heavy metals in water was analysed. Clams were analysed for methallothionein concentrations. The speciation of Zn, Cd, Pb and Cu along the salinity gradient was modelled. Zn showed the highest concentrations and its prevalent species was the free ion. Intersite differences have been observed in methallothionein concentration and related to the salinity gradient. It seems that synthesis of methallothioneins is the result of physiological forces acting in concert with the changes in the chemical speciation of metals, owing to the trace metals uptake is controlled by means of an interaction of physiology and physicochemistry.