Low Salinity Seawater Research Articles

Effect of seawater salinity on pore-size distribution on a poly(styrene)-based HP20 resin and its adsorption of diarrhetic shellfish toxins

In the present study, okadaic acid (OA) and dinophysistoxin-1 (DTX1) were spiked into artificial seawater at low, medium and high estuarine salinities (9‰, 13.5‰ and 27‰). Passive samplers (HP20 resin) used for solid phase adsorption toxin tracking (SPATT) technology were exposed in these seawaters for 12-h periods. Adsorption curves well fitted a pseudo-secondary kinetics model. The highest initial sorption rates of both toxins occurred in the seawater of medium salinity, followed by seawater of low and high estuarine salinity. Pore volumes of micropores (<2nm) and small mesopores (2nm<diameter<10nm) of HP20 resin decreased after adsorption of toxins in seawater at high and low salinity but not in seawater at medium salinity, which demonstrated that the toxin molecules entered into micropores and mesopores (below 10nm in size) in seawaters of high and low salinity. More toxin or other matrix agglomerates were displayed on the surface of resin deployed in the seawater of medium salinity. Taking into consideration the pore-size distribution and surface images, it appears that intra-particle diffusion governs toxin adsorption in seawater at high salinity while film diffusion mainly controls the adsorption process in seawater at medium salinity. This is the first study to confirm that molecules of OA and DTX1 are able to enter into micropores (<2nm) and small mesopores (2–10nm) of HP20 resin in estuarine seawater with high salinity (∼27‰).

Flood Impacts in Keppel Bay, Southern Great Barrier Reef in the Aftermath of Cyclonic Rainfall

In December 2010, the highest recorded Queensland rainfall associated with Tropical Cyclone ‘Tasha’ caused flooding of the Fitzroy River in Queensland, Australia. A massive flood plume inundated coral reefs lying 12 km offshore of the Central Queensland coast near Yeppoon and caused 40–100% mortality to coral fringing many of the islands of Keppel Bay down to a depth of ∼8 m. The severity of coral mortality was influenced by the level of exposure to low salinity seawater as a result of the reef's distance from the flood plume and to a lesser extent, water depth and whether or not the reef faced the plume source. There was no evidence in this study of mortality resulting from pollutants derived from the nearby Fitzroy Catchment, at least in the short term, suggesting that during a major flood, the impact of low salinity on corals outweighs that of pollutants. Recovery of the reefs in Keppel Bay from the 2010/2011 Fitzroy River flood is likely to take 10–15 years based on historical recovery periods from a similar event in 1991; potentially impacting visitor numbers for tourism and recreational usage. In the meantime, activities like snorkeling, diving and coral viewing will be focused on the few shallow reefs that survived the flood, placing even further pressure on their recovery. Reef regeneration, restoration and rehabilitation are measures that may be needed to support tourism in the short term. However, predictions of a warming climate, lower rainfall and higher intensity summer rain events in the Central and Coastal regions of Australia over the next decade, combined with the current anthropogenic influences on water quality, are likely to slow regeneration with consequent impact on long-term reef resilience.

Post-operative care of implanted pearl oysters Pinctada fucata in low salinity seawater improves the quality of pearls

Current techniques for culturing the Akoya pearl oyster Pinctada fucata result in low yields of blemish-free, round pearls (high-quality pearls). We compared the effects of five factors on the proportion of high-quality pearls produced during culture using a generalized linear model (GLM). Two factors were physiological, shell-closing strength (SCS) and the whole wet weight of host pearl oysters, and three factors were procedural, post-operative care method, technician, and nucleus diameter. Our results suggest that post-operative care methods have the most significant effect on increasing the proportion of high-quality pearls. The proportion of high-quality pearls was five-fold higher in the group held in low salinity seawater than in the conventional treatment group. We propose a new post-operative care method in which oysters are immersed in low salinity seawater to increase the production of high-quality pearls.

Concentration of enteric virus indicator from seawater using granular activated carbon

Fecal contamination of shellfish growing seawater with enteric viruses is often associated with human outbreaks of gastroenteritis. Male specific bacteriophage MS2 is correlated with those of enteric viruses in a wide range of water environments and has been used widely as a surrogate for pathogenic waterborne viruses. Since viruses in contaminated water are usually at low levels, the development of methods to concentrate viruses from water is crucial for detection purposes. In the present study, granular activated carbon was evaluated for concentration of MS2 from artificial seawater, and different parameters of the seawater were also compared. Recovery of MS2 from warm seawater (37°C) was found to be significantly greater than from cold seawater (4 and 20°C), and even greater than from fresh water (4, 20 and 37°C); the difference between seawater and fresh water became less profound when the temperatures of both were below 37°C. Although not of statistical significance, recovery of MS2 from low salinity seawater (10 and 20 parts per thousand, ppt) was greater than from high salinity seawater (30 and 40ppt). One gram of granular activated carbon was able to extract 6-log plaque forming units (PFU) of MS2 from 500ml seawater at 37°C. This study demonstrated that granular activated carbon can concentrate an enteric virus indicator from shellfish growing seawater effectively.

Effect of dietary potassium on growth, nitrogen metabolism, osmoregulation and immunity of pacific white shrimp (Litopenaeus vannamei) reared in low salinity seawater

An 8 weeks feeding experiment was conducted to determine the effect of dietary potassium on the growth and physiological acclimation of Pacific white shrimp (Litopenaeus vannamei) reared in diluted seawater (salinity 4). Six semi-purified practical diets containing 0.59, 0.96, 1.26, 1.48, 1.74, and 2.17 g potassium K+ per 100 g diet were formulated, respectively. The survival and feed conversion rate did not show significant difference among groups of shrimps given these diets (P>0.05). The shrimps fed the diets containing 0.96–1.48 g K+ per 100 g diet gained the highest weight, specific growth rate, and protein efficiency ratio. Their ammonium-N excretion rate as well as hemolymph concentration of Na+ and Cl− were significantly lower than those of the control (P<0.05), but a reverse trend was observed for their gill Na+/K+-ATPase. Moreover, the shrimps fed with 1.48 g K+ per 100 g diet were the highest in hemolymph urea level, and the phenoloxidase and lysozyme activities were significantly higher than those of the control (P<0.05). The growth and physiological response of the test shrimps suggested that diet containing 1.48 g K+ per 100 g diet improved the growth of L. vannamei in low-salinity seawater, and enhanced the physiological acclimation of the organism.

Technology Focus: EOR Performance and Modeling (January 2013)

Technology Focus Enhanced oil recovery (EOR) targets the approximately two-thirds of oil remaining in reservoirs after conventional recovery methods have been exhausted. More than 350 EOR papers were published from October 2011 to September 2012 because two major EOR meetings were held in Tulsa and Oman and a few international meetings had EOR sections as a primary topic, such as the International Petroleum Technology Conference in Thailand and the SPE Heavy Oil Conference Canada in Calgary. I categorized these EOR papers into the topics of EOR screening methodologies, reservoir problem identification and evaluation technologies, chemical EOR methods for conventional oil, chemical methods for heavy oil, gasflooding, conformance control using in-situ and preformed particle gels and foams, thermal EOR methods, smart-water flooding, nanofluid for EOR, EOR for shale oil, and new EOR technologies. Five papers were published to provide methods to screen EOR technologies. More than 20 papers published were related to EOR by altering water salinity and compositions, such as low-salinity waterflooding, seawater flooding, and tuning water salinity and ionic content. More than 10 papers were published to address one recent interest: using chemical methods to enhance heavy-oil recovery. The development of high-molecular-weight polymer and new types of polymer such as associated polymer has made some chemical methods such as polymer flooding feasible for some heavy oils. However, these three types of papers were not featured this time, either because the category was featured in the last couple of years or because the papers are too long or too complex to be synopsized. But these topics, along with some others, such as gas-flooding for shale oil and nanoparticle EOR, are selected to form the list of papers suggested to be read. I have selected the following four topics for the EOR feature this time: experience of alkaline/surfactant/polymer flooding in China, polymer flooding pilot in the Middle East, a review of mobility and conformance control for CO2 EOR, and a new correlation to predict optimum surfactant structure. Recommended additional reading at OnePetro: www.onepetro.org. SPE 141283 Full Barrel Analysis: A Simulation Model Interrogation Tool To Assess Sweep Efficiencies and Identify Targets for Improved Oil Recovery by M.S. Beckman, ExxonMobil, et al. SPE 155546 PDO’s EOR Screening Methodology for Heavy-Oil Fractured Carbonate Fields—A Case Study by Georg Warrlich, Shell, et al. SPE 154218 Four-Phase Equilibrium Calculations of CO2/Hydrocarbon/Water Systems Using a Reduced Method by Saeedeh Mohebbinia, The University of Texas at Austin, et al. SPE 154675 Viscosifying Surfactant Technology for Chemical EOR: A Reservoir Case by G. Degré, Rhodia, et al. SPE/CSUG 148971 Sweep Efficiency Improvement by Alkaline Flooding for Pelican Lake Heavy Oil by Mingzhe Dong, University of Calgary, et al.

绿原酸对凡纳滨对虾抗氧化系统及抗低盐度胁迫的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 绿原酸对凡纳滨对虾抗氧化系统及抗低盐度胁迫的影响 DOI: 10.5846/stxb201304160720 作者: 作者单位: 农业部水产品加工重点实验室 中国水产科学研究院 南海水产研究所,建明工业珠海有限公司,农业部海洋渔业可持续发展重点实验室 中国水产科学研究院 黄海水产研究所;农业部海洋渔业可持续发展重点实验室 中国水产科学研究院 黄海水产研究所,农业部水产品加工重点实验室 中国水产科学研究院 南海水产研究所,农业部水产品加工重点实验室 中国水产科学研究院 南海水产研究所,农业部水产品加工重点实验室 中国水产科学研究院 南海水产研究所,农业部水产品加工重点实验室 中国水产科学研究院 南海水产研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 中央级公益性科研院所基本科研业务费专项资金(2011TS05,2013TS03);农业部水产品加工重点实验室开放基金课题(nybjg201205) Effects of dietary chlorogenic acid supplementation on antioxidant system and anti-low salinity of Litopenaeus vannamei Author: Affiliation: Key Laboratory of Aquatic Product Processing,Kemin Industries Zhuhai Co,Ltd,Key Laboratory for Sustainable Development of Marine Fisheries,Key Laboratory of Aquatic Product Processing,Key Laboratory of Aquatic Product Processing,Key Laboratory of Aquatic Product Processing,Key Laboratory of Aquatic Product Processing Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:对绿原酸调节凡纳滨对虾(Litopenaeus vannamei)血淋巴抗氧化系统功能及抗低盐度胁迫的效果进行了评价。360尾凡纳滨对虾随机分为4组,分别投喂含有0、100、200和400 mg/kg绿原酸的饲料28 d,随后将对虾从盐度为32的天然海水直接转入至盐度为10的水中胁迫72 h。结果表明,在正常养殖条件下,绿原酸对凡纳滨对虾的成活率、血淋巴总抗氧化能力(Total antioxidative capacity, T-AOC)、超氧化物歧化酶(Superoxide dismutase, SOD)及过氧化氢酶(Catalase, CAT)活力均无明显影响,然而投喂含有绿原酸的饲料14 d,对虾血淋巴谷胱甘肽过氧化物酶(Glutathione peroxidase, GPx)活性和血淋巴细胞GPx和CAT基因表达水平均显著高于对照组(P<0.05);低盐度胁迫24 h,绿原酸组凡纳滨对虾的存活率较对照组提高10%,但各组之间无显著性差异(P>0.05);低盐度胁迫24 h,各组凡纳滨对虾血淋巴T-AOC、SOD和GPx活性与胁迫前相比均显著增加,说明低盐度胁迫条件下机体产生了抗氧化胁迫反应,同时绿原酸组对虾血淋巴GPx、CAT活性均显著高于对照组(P<0.05);低盐度胁迫72 h,绿原酸组对虾血淋巴T-AOC、GPx和CAT活性和血淋巴细胞GPx和CAT基因表达水平均明显高于对照组。上述结果表明绿原酸可有效调节凡纳滨对虾的抗氧化系统功能,增强对虾对于低盐度胁迫下的适应能力。 Abstract:Intensively-reared white shrimp Litopenaeus vannamei are subjected to various environmental stresses that can have severe effects on their physiology. For example, low salinity stress decreases the activity of antioxidant enzymes. How to reduce the adverse effects of multiple environmental stresses on shrimp has become a new challenge in aquaculture. Chlorogenic acid has been documented to effectively scavenge free radicals and improve antioxidant defenses in humans and animals. The objectives of this study were to evaluate the effects of chlorogenic acid on the antioxidant system of L. vannamei, and determine whether it protects the shrimp against low salinity stress. A total of 360 shrimps with an average initial body weight of about 6.7 g were divided randomly into four replicated (×3) treatments, and reared indoors in 500-L glass-fiber tanks containing 300 L of natural seawater. The shrimp were fed one of four diets, a control diet without chlorogenic acid, and three diets containing different levels (100, 200, 400 mg/kg diet) of chlorogenic acid. Shrimps in each treatment were hand-fed one of the four diets to apparent satiation three times daily; uneaten food and feces were removed by siphoning. Prior to the beginning of the feeding trial, all shrimps were acclimatized for one week. Each tank was continuously oxygenated using an air pump, and 30% of the seawater was renewed daily. During the experimental period, water temperature, salinity, pH and other water quality parameters were kept stable. After being fed for 28 days, all shrimps were subjected to acute low salinity stress in which salinity was decreased rapidly from 32 to 10 for 72 h. The results indicated that at normal salinity (32), there were no significant differences in the survival, the total antioxidant status (T-AOC), superoxide dismutase (SOD) and catalase (CAT) activities of the hemolymph of white shrimps that were fed diets with or without chlorogenic acid. However, the glutathione peroxidase (GPx) activity and gene expression of GPx and CAT of shrimp hemolymph increased significantly (P<0.05) when shrimps were, for 14 days, fed diets containing different concentrations of chlorogenic acid. After exposure to low-salinity seawater for 24 h, survival of shrimps fed diets supplemented with chlorogenic acid increased by 10% compared with the control treatment, although the difference between the control and treatments was not significant (P>0.05). Activities of T-AOC, SOD and GPx of shrimp hemolymph in all treatments increased significantly after 24 h of low salinity stress, which suggests that low salinity induced an antioxidant stress response in the shrimps. Moreover, GPx and CAT activities of hemolymph in shrimp fed diets supplemented with chlorogenic acid were significantly higher than those fed the control diet after 24 h of low salinity stress (P<0.05). Over a period of 72 h of exposure to low salinity, activities of T-AOC, GPx and CAT, along with gene expression of GPx and CAT of hemolymph in white shrimp fed dietary chlorogenic acid, were significantly higher than those measured in the control animals. In conclusion, the findings of this study suggest that chlorogenic acid can serve as an effective antioxidant to regulate the antioxidant defense system of white shrimp and improve resistance against low salinity stress. 参考文献 相似文献 引证文献

Larval rearing of barramundi ( Lates calcarifer) in saline groundwater

Barramundi ( Lates calcarifer) larvae were reared from 2 to 25 days post hatch in 14‰ saline groundwater with either no potassium supplementation (38% K-equivalence) or full potassium supplementation (100% K-equivalence). Growth, survival and swimbladder inflation of these larvae were compared against those grown in control treatments of seawater (32‰) and seawater diluted to 14‰. Those reared in saline groundwater with 38% K-equivalence exhibited complete mortality within 2 days, while those held in groundwater with full supplementation survived at a rate equal to both control treatments (pooled average 51.1 ± 0.5%). At 25 days post hatch, there was no significant difference in larval length or dry weight between those grown in the 14‰ control treatment and those in the saline groundwater with full potassium supplementation. There were no significant differences in swim bladder inflation between any of the surviving treatments (average 93.3 ± 2.5%). This is the first description of rearing barramundi larvae both in low salinity seawater and in saline groundwater and demonstrates that the requirement for potassium by larval barramundi is higher than for juveniles of the same species.

Interaction of short-term testosterone treatment with osmotic acclimation in the gilthead sea bream Sparus auratus

To assess the interaction between testosterone (T) treatment and acclimation to different salinities, seawater-acclimated gilthead sea bream (Sparus auratus) were implanted with slow-release coconut oil implants alone (control) or containing T (5 μg/g body mass). After 5 days, eight fish of control and T-treated groups were sampled. The same day, eight fish of each group were transferred to low salinity water (LSW, 6 ppt, hypoosmotic test), seawater (SW, 38 ppt, control test) and high salinity water (HSW, 55 ppt, hyperosmotic test) and sampled 9 days later. Gill Na+, K+-ATPase activity increased in HSW-acclimated fish with respect to SW- and LSW-acclimated fish in both control and T-treated groups. Kidney Na+, K+-ATPase activity was also enhanced in HSW-acclimated fish, but only in T-treated group. From a metabolic point of view, most of the changes observed can be attributed to the action of salinity and T treatment alone, since few interactions between T treatment and osmotic acclimation to different salinities were observed. Those interactions included in treated fish: in the liver, decreased capacity in using glucose in fish acclimated to extreme salinities; in the gills, decreased capacity in using amino acids in HSW; in the kidneys increased capacity in using amino acids in extreme salinities; and in the brain, decreased glycogen and acetoacetate levels of fish in LSW.

Effects of Salinity on Spawning and Early Development of the Tube-Building PolychaeteHydroides elegansin Hong Kong: Not Just the Sperm's Fault?

Ambient salinities drop dramatically during monsoon season in Hong Kong coastal waters, posing a number of problems for externally fertilizing species like the polychaete Hydroides elegans. In this study, we investigated (1) whether adults would retain their gametes when external salinity dropped to levels too low to support fertilization and development, and (2) whether failure of development at low salinity reflects a failure of fertilization or a failure of fertilized eggs to cleave. Adults released eggs and sperm in the laboratory even at the lowest salinity tested, a practical salinity (S) of 5, and yet very few eggs cleaved at salinities below about 22. By mixing gametes at high salinity and then transferring the fertilized eggs to low-salinity seawater, we found that salinities below about 22 reduced the percentage of fertilized eggs that cleaved. Similarly, mixing gametes at salinities as low as 15 and then transferring the eggs to full-strength seawater (S = 30) rescued a substantial number of eggs, many more of which cleaved after their transfer to the higher salinity. The results suggest that failure of early development at low salinity in this species in large part reflects an inability of newly fertilized eggs to complete meiosis and cleave, rather than simply a failure of fertilization.

Effect of dietary bovine lactoferrin on growth response, tolerance to air exposure and low salinity stress conditions in orange spotted grouper Epinephelus coioides

Lactoferrin (LF), which is known as a functional glycoprotein originated from mammalian fluid, was orally administrated to juvenile orange spotted grouper (initial wt = 3.0 g) to investigate its effects on growth response, mucus secretion, tolerance to air exposure and response in heat shock protein under low salinity condition. Test diets containing four different concentrations of LF (0, 400, 800 and 1200 mg LF/kg diet) were fed to the juvenile groupers for 30 days. At the termination of feeding trial, amounts of secreted mucus on body surface were measured, while fish were exposed to the air for 60 min to examine the recovery from respiratory distress condition. Furthermore, fish were exposed to low salinity (3.5 ppt) seawater for 0 and 6 h, respectively. After low salinity seawater exposure, the quantitative levels of heat shock protein 70 family (HSP70s) in branchial lamellae were measured. Dietary LF did not affect growth rate of this species under the condition applied in this study. Mucus secretion significantly increased in all LF supplemented groups compared to that in LF-free group. Recovery rate from air exposure stress test increased with increasing dietary LF level. Under the low salinity exposure, significantly higher levels of HSP70s were detected in 800 and 1200 mg LF supplemented groups than that in LF-free group in both 0 and 6 h exposure. These results demonstrated that dietary LF enhances tolerance to air exposure stress and low salinity stress together with increasing the level of HSP70s in branchial lamellae of orange spotted grouper juvenile.

Relation of ice growth rate to salt segregation during freezing of low-salinity sea water (Bothnian Bay, Baltic Sea)

AbstractSalt segregation and isotopic fractionation during sea-ice formation can be parameterized as a function of the ice growth rate. We performed a study to investigate if the salt segregation models derived for saline sea-ice studies are pertinent during the growth of Baltic Sea ice in brackish water. We used a time series of ice-salinity profiles and modeled growth rates to examine the relationship between effective salt segregation and growth rate. The results show that models derived for saline sea water are not directly applicable for use in the brackish waters of the Baltic Sea. We derived a simple model for the effective salt segregation in relation to ice growth rate, for a wide range of growth rates, pertinent for use in low-salinity Baltic Sea conditions and in the future development of a Baltic Sea ice salinity model.

Effects of hypo-osmosis on the coral Stylophora pistillata: nature and cause of 'low-salinity bleaching'

The response of the scleractinian coral Stylophora pistillata to short-term (min to h) and long-term (d) exposure to reduced-salinity seawater was examined. Pulse Amplitude Modulated (PAM) chlorophyll fluorescence techniques were used to assess the photosynthetic efficiency of the symbiotic dinoflagellates (dark-adapted F/F) in the coral tissues (in hospite) before, during and after exposure. Exposure to reduced-salinity seawater caused a marked reduction in efficiency (the ratio of variable [F] to maximal [F] fluorescence), and there was an apparent link between a reduction in dark-adapted F/F and a loss of symbiotic dinoflagellates from the corals. The reduction in F/F of the symbiotic algae and subsequent dissociation of the coral-algal symbiosis (coral bleaching) occurred during exposure to reduced-salinity seawater in either the light or dark. The results demonstrate that bleaching in response to low-salinity seawater is a truly sublethal response, contrary to a recent suggestion. The study also suggests that bleaching of corals in response to low-salinity seawater may not involve the passive loss of algal symbionts and that an impairment of the capacity of the algal symbionts for photosynthesis represents a common 'cue' initiating the dissociation of the coral-algal symbiosis during exposure to sub-optimal conditions. This study demonstrates how exposure to low-salinity seawater alone can cause some of the symptoms commonly attributed to temperature anomalies and anthropogenic pressures on coral reefs.

The components of an inorganic physiological buffer for Penaeus chinensis.

Shrimp Penaeus chinensis, 5--8 cm in body-length were held in laboratory aquaria after collection from culture ponds at Laoshan in Qingdao in 1992. The osmotic pressure and the concentration of inorganic components of hemolymph in the shrimp were measured. The optimum pH and osmolarity of the buffer were determined from tests on primary cultures of hepatopancreatocytes in vitro. The results indicate that the hemolymph is homoiosmotic to 27 ppt seawater at 870 mOsm/L; osmotic regulation of shrimp is strong in low-salinity seawater, but weak in high-salinity seawater; the concentration of Mg(2+) ions in hemolymph is much less than that in seawater, while [K(+)] and [Ca(2+)] are much higher; hepatopancreatocytes in vitro have optimal survival at osmolarity range of 780-1, 100 mOsm/L and pH 6.5. Accordingly, an inorganic physiological buffer for P. chinensis (PPB, Penaeid Physiological Buffer) was prepared and contains NaCl, 23.0 g/L; K(2)SO(4), 1.1 g/L; CaCl(2), 1.6 g/L; MgSO(4).7H(2)O, 1.6 g/L; NaH(2)PO(4).2H(2)O, 0.35 g/L; NaHCO(3), 0. 05 g/L; pH 6.5; osmolarity, 867.9 mOsm/L. For storage of PPB, 4 stock buffers are made: 1) 10x PPB-A, which contains 230 g/L NaCl, 11 g/L K(2)SO(4), and 3.5 g/L NaH(2)PO(4).2H(2)O; 2) 40x PPB-B, which contains 64 g/L MgSO(4).7H(2)O; 3) 40x PPB-C, which contains 64 g/L CaCl(2); and 4) 100x PPB-D, which contains 50 g/L NaHCO(2). In order to increase the buffering capacity, PPB may be modified (to His-PPB), in which 5 g/L Histidine.HCl is used as the buffer reagent in place of NaH(2)PO(4) and NaHCO(3).

Dissolved and Particulate Organic Carbon in Chesapeake Bay

We measured dissolved and particulate organic carbon (DOC and POC) in samples collected along 13 transects of the salinity gradient of Chesapeake Bay. Riverine DOC and POC end-members averaged 232±19 μM and 151±53 μM, respectively, and coastal DOC and POC end-members averaged 172±19 μM and 43±6 μM, respectively. Within the chlorophyll maximum, POC accumulated to concentrations 50–150 μM above those expected from conservative mixing and it was significantly correlated with chlorophylla, indicating phytoplankton origin. POC accumulated primarily in bottom waters in spring, and primarily in surface waters in summer. Net DOC accumulation (60–120 μM) was observed within and downstream of the chlorophyll maximum, primarily during spring and summer in both surface and bottom waters, and it also appeared to be derived from phytoplankton. In the turbidity maximum, there were also net decreases in chlorophylla (−3 μg l−1 to −22 μg l−1) and POC concentrations (−2 μM to −89 μM) and transient DOC increases (9–88 μM), primarily in summer. These occurred as freshwater plankton blooms mixed with turbid, low salinity seawater, and we attribute the observed POC and DOC changes to lysis and sedimentation of freshwater plankton. DOC accumulation in both regions of Chesapeake Bay was estimated to be greater than atmospheric or terrestrial organic carbon inputs and was equivalent to ≈10% of estuarine primary production.

Effect of environment and gibberellins on the early growth and development of the red mangrove, Rhizophora mangle L.

Seedlings of the red mangrove, Rhizophora mangle L., were subjected to a variety of salinity, light, and plant growth regulator treatments to examine the influence of these factors on early development. Stem, leaf, and root growth were significantly enhanced in both low salinity seawater and under reduced intensities of solar radiation. Semi-quantitative analyses of GAs by enzyme-linked immunoabsorbant assays (ELISA) suggest that under these conditions the early 3/13 hydroxylation GA1 biosynthetic pathway is predominant in R. mangle. Concentrations of GA1 and GA19-like substances were highest in propagules exhibiting enhanced development. Attempts to identify the endogenous GAs by GC-MS were unsuccessful, most likely due to undetermined impurities present in mangroves. Exogenous applications of GA3 to R. mangle were moderately successful in alleviating shoot growth inhibitions observed at higher salinities and light levels. The role of gibberellins is discussed in terms of metabolic responses to the external environment and possible impacts upon the distribution of this species.

Plasma cortisol and secondary stress responses of cultured red drum ( Sciaenops ocellatus) to several transportation procedures

Transportation procedures induced rapid elevations in plasma cortisol and glucose concentrations (100–160 ng/ml and 60–140 mg/100 ml, respectively) within 15–30 min of capture and loading in cultured juvenile red drum. The elevations were transient and plasma levels of cortisol returned to baseline levels during the 5.5 h transport, suggesting that capture and loading are the most traumatic procedures. Plasma glucose concentrations had returned to baseline values within 1–2 days of transport. Plasma osmolality increased during transportation in 32 ppt seawater and decreased during transport in 4 ppt seawater. Survival ranged from 96 to 100%, indicating that despite the trauma associated with initial transport procedures, juvenile red drum can be transported successfully in seawater or low salinity seawater. Anesthesia with MS-222 (80 mg/l) prior to capture, coupled with the use of sedating doses (5 and 25 mg/l MS-222) in the transport tanks, did not decrease the magnitude of the stress responses. On the contrary, the corticosteroid stress response was augmented in fish transported in 25 mg/l MS-222. Laboratory tests showed that long-term (30–90 min) exposure to sedating doses of the anesthetic caused a dose-dependent increase in plasma cortisol levels, whereas anesthetization of red drum with MS-222 prior to capture and transport in anesthetic-free seawater markedly reduced the plasma corticosteroid response after capture/loading and at the end of transport. Plasma glucose levels and osmolality were also lower in those fish anesthetized prior to capture. These results suggest that acute exposure to immobilizing doses of an anesthetic, MS-222, is an effective method of reducing endocrine and metabolic disturbances during transportation of red drum.

Microgrowth patterns in the shell of the Malaysian cockle Anadara granosa (L.) and their use in age determination

Marked specimens of the Malaysian cockle Anadara granosa (L.) were placed in buried cages (filled with sediment from the surrounding substratum) which were located in intertidal and subtidal environments in an area between Penang Island and mainland West Malaysia. In the majority of cockle shells examined the number of growth bands deposited was close to the number of tidal periods. Bands in the shells of intertidal animals were more strongly defined than those in shells continuously immersed. The banding pattern in shells from the subtidal environments showed narrow increments during spring tides alternating with a few wider increments during neap tides. The growth increments between bands correspond to tidal periods so they can be used to record growth rates and provide estimates of the ages of the shells. Samples of cockles collected from four sites in a commercial cockle-culture area off the coast of West Malaysia were aged. Two of the sites were located in an estuary where the cockles were periodically exposed to fluctuating salinities during the intermonsoon period. Cockles from the other two sites were situated away from the estuary and experienced full strength sea water. There was good agreement between the calculated estimates of the ages determined from the tidal bands and their known ages. Shells of cockles from the estuary had characteristically marked banding patterns which may be related to shell deposition during the intermonsoon period when the cockles were exposed to sea water of low salinity. Cockle shells collected outside the estuary did not display these patterns.

Ability of some gastropod egg capsules to protect against low-salinity stress

The ability of the egg capsules of three intertidal gastropod species to protect embryos against low-salinity stress was examined. Encapsulated embryos of Ilyanassa obsoleta (Say), Nucella lamellosa (Gmelin), and N. lima (Gmelin) were far more tolerant of transfer to water of reduced salinity than were embryos which had been prematurely removed from egg capsules and transferred to low-salinity sea water directly. However, the walls of N. lamellosa and N. lima capsules were found to be permeable to salts and at least to small carbohydrate molecules (glucose). Correspondingly, indirect evidence for all three species and direct evidence for N. lamellosa indicates that the osmotic concentration of intracapsular fluid declines to near ambient after transfer of egg capsules to dilute medium. Experiments conducted using embryos of N. lamellosa suggest that the egg capsules may protect embryos by reducing the rate at which the osmotic concentration of intracapsular fluid decreases rather than by reducing the magnitude of the decrease.

The Influence of Temperature and Salinity Upon the Acute Toxicity of Heavy Metals to the Banana Prawn (Penaeus merguiensisde Man)

Abstract Bioassays were conducted to determine the effects of temperature and salinity on the acute toxicity of mercury, copper, cadmium, zinc, nickel and lead to juvenile banana prawns (Penaeus merguiensis de Man). Tests were conducted at all combinations of 35, 30 and 20°C with 36 and 20° salinity over 96 h. The general rank order of metal toxicity was Hg > (Cu, Cd, Zn) > Ni > Pb. The toxicity of all metals increased with increased temperature. This was most noticeable in the high salinity treatments, particularly for copper and zinc. Salinity appeared to influence the toxicity of all metals tested although significant differences were only found for copper and lead at 20°C. At this temperature prawns were markedly more susceptible to both metals in low salinity sea water. The data are compared with lethal concentrations found for other crustaceans and are discussed in relation to existing water quality criteria.