Polonium-210 content of marine shrimp: Variation with biological and environmental factors

The concentrations of ²¹⁰Po and ²¹⁰Pb were determined in more than 30 species of marine shrimp. Samples were collected in the years 1977 to 1980; most were from the Mediterrancean Sea near Monaco, the remainder from Kuwait, South Africa, USA and Great Britain. The median ²¹⁰Po concentration was 8.0 pCi g^-1 dry wt in the whole shrimp and 85 pCi g^-1 dry in the hepatopancreas; the corresponding ²¹⁰Po:²¹⁰Pb activity ratios were 77 and 138, respectively. The range of concentrations covered more than two orders of magnitude for both nuclides. The variations in the levels of ²¹⁰Po, in particular, could be related to biological and environmental factors; thus, penaeid shrimp had ²¹⁰Po at median concentrations some three to four times higher than carid shrimp, and there was a steady increase in the median ²¹⁰Po concentration as one moved from estuarine to coastal to pelagic to deep-pelagic species. ²¹⁰Po levels were highest in 3 species of deep-pelagic penaeids, where a median ²¹⁰Po concentration in the whole shrimp of 43 pCi g^-1 dry wt was found. The natural radiation dose received by the hepatopancreas of such individuals will be of the order of 100 rem per yr. Elevated ²¹⁰Po was also found in 4 species collected near Kuwait. The ²¹⁰Po data are interpreted as indicating changes in the food regime of different shrimp; specifically it is suggested that ²¹⁰Po-rich items such as hepatopancreas, faecal pellets and organic particulates are likely to be important in the diet of shrimp which feed at depth in the ocean. It is suggested further that the ultimate availability of ²¹⁰Po to the foodchain depends on its form in sea water, and the need for information concerning the degree of organic binding of ²¹⁰Po in natural waters in stressed.     

Polonium-210 and lead-210 in marine food chains

²¹⁰Po and ²¹⁰Pb have been measured systematically in whole animals, muscle and hepatopancreas of crustaceans and of molluscan cephalopods representative of a pelagic and benthic food chain. The same nuclides were also measured in liver, pyloric caecum, stomach contents and muscle of tuna. The concentration factors from sea water to whole animals were approximately constant along both food chains, being of the order of 10⁴ for ²¹⁰Po and 10² for ²¹⁰Pb. The highest concentration factors were found in shrimp of the genus Sergestes. In muscle, the concentration factors were an order of magnitude less; in the hepatopancreas, they were an order of magnitude higher, reaching 10⁶ in shrimp of the genus Sergestes. Such concentrations imply alpha-radiation doses of the order of 10 rem per year and more in this organ, which contains about 50 to 90% of the ²¹⁰Po in the whole animal in the 11 species analyzed. A detailed study of the intracellular behaviour of ²¹⁰Po in the hepatopancreas is clearly indicated. ²¹⁰Po can be used as a sensitive natural tracer in biological systems. Thus, feeding Meganyctiphanes norvegica in the laboratory on food low in ²¹⁰Po led to an approximate value of about 61/2 days for the biological half-life of ²¹⁰Po in the hepatopancreas of this euphausiid. Furthermore, the data on ²¹⁰Po and ²¹⁰Pb in the cephalopod hepatopancreas allowed the time of conservation of frozen squid which had been bought at the market to be estimated.     

Polonium-210 in euphausiids: A detailed study

A detailed study of ²¹⁰Po, the predominant alpha-emitting nuclide found in most marine organisms, has been undertaken in a particular zooplanktonic species, the euphausiid Meganyctiphanes norvegica. The purpose was to obtain information concerning the origin, the localization and the flux of the nuclide in and through this organism. Measurements of ²¹⁰Po were made in euphausiids of different sizes, in dissected organs and tissues, and in excretion products. The results show higher concentrations in the smaller specimens; this fact cannot be explained on the basis of surface adsorption, but is probably related to the ingestion of food. Dissection results show that the distribution of ²¹⁰Po in euphausiids is not homogeneous, but that the majority is concentrated in the internal organs, the alimentary tract and the hepatopancreas in particular. The natural radiation dose received by these organs is in consequence much higher than that received by the whole animal. Use of a dynamic model allowed the flux of ²¹⁰Po through M. norvegica to be calculated. The calculations confirm that food is the principal source of ²¹⁰Po for this species, and clearly show that fecal pellets constitute the major elimination route. Extrapolation of the data to zooplankton in general leads to the conclusion that zooplankton metabolic activity plays an important role in transporting ²¹⁰Po from the surface layers of the ocean to depth.     

Polonium-210 and lead-210 in Antarctic marine biota and sea water

Concentrations of the naturally-ocurring radionuclides ²¹⁰Po and ²¹⁰Pb were measured in krill (Euphausia superba), mesozooplankton, phytoplankton and sea water collected during the South African SIBEX cruise to the Antarctic in autumn 1984. The data reported constitute the first substantial measurements on ²¹⁰Po and ²¹⁰Pb in such samples in the Antarctic Ocean. The concentrations of ²¹⁰Po in mesozooplankton and phytoplankton are unexceptional in comparison with those from other oceans. The SIBEX E. superba, however, have higher levels of ²¹⁰Po than usually found in euphausiids. The ²¹⁰Po data, combined with reasonable estimates of biological quantitites such as the fractional assimilation, are used to obtain information about the diet of E. superba. It is suggested that the higher ²¹⁰Po in the SIBEX E. superba reflects a change from an almost entirely phytoplanktonic diet in summer to a more omnivorous diet as winter approaches. The data show that there are allometric relationships between the ²¹⁰Po content of euphausiids and animal size; these are discussed briefly. The limited sea-water data presented are characterized by unusually high ²¹⁰Po:²¹⁰Pb activity ratios and need further investigation.     

210Po and 210Pb in zooplankton fecal pellets

²¹⁰Po and ²¹⁰Pb concentrations in fecal pellets from the zooplanktonic euphausiid Meganyctiphanes norvegica are reported. The ²¹⁰Po:²¹⁰Pb activity ratio is 2.2±0.3, a value in good agreement with that found in suspended particulate matter in surface seawater. Estimates of ²¹⁰Po and ²¹⁰Pb removal times from the mixed layer by fecal pellets alone yield values which are of the same order of magnitude as the removal times for these nuclides by all routes. It is suggested that there is a high probability that zooplanktonic fecal pellets play a significant role in the removal of both these nuclides from the surface layers of the ocean.     

210Pb as a dietary indicator in the Antarctic pelagic community

The naturally occurring radionuclide ²¹⁰Po is useful as a tracer of diets of marine organisms. Data for ²¹⁰Pb, the grandparent of ²¹⁰Po, are less abundant: we therefore report here ²¹⁰Pb concentrations in a substantial collection of marine biota obtained from the Antarctic Ocean during the SIBEX II cruise in 1985. The general levels of ²¹⁰Pb are within the range of previously published data but, as in the case of ²¹⁰Po, there are differences which can be associated with variations in the diet of the organism. The levels of ²¹⁰Pb in the krill Euphausia superba show seasonal changes which can be interpreted in terms of changing diet. In a simple classification of the pelagic food chain, the levels of ²¹⁰Pb tend to increase from omnivores to filter-feeders to predators.     

210Po content in sea water and its accumulation in southern Baltic plankton

This paper presents the results of an investigation from 1980 to 1985 on the content of ²¹⁰Po in sea water and its accumulation in southern Baltic plankton. The mean value of the ²¹⁰Po concentration in sea water has been determined to be about 0.5 mBq dm^-3, with the proportion of the dissolved forms being ca 80%. It has been proved that ²¹⁰Po is accumulated by plankton organisms. The mean ²¹⁰Po concentration factors calculated on the basis of its content in plankton fall within the range from 5×10³ to 4.2×10⁴ and increase as follows: phytoplankton210Po concentration in mesozooplankton collected at the Slupsk Trough and the Gdask Basin have been observed. The above differences have been related to intense blue-green alga blooming in the Gdask Basin.     

Assimilation of 210Po by the mussel Mytilus edulis from the alga Isochrysis galbana

Marine invertebrates are thought to accumulate ²¹⁰Po primarily from their food. In this study, a pulse-chase methodology was used to examine the assimilation and depuration of ²¹⁰Po by Mytilus edulis from the common marine alga Isochrysis galbana. The digestion of ²¹⁰Po from I. galbana occurred via a biphasic process, characteristic of a rapid (extracellular) and slow (intracellular) digestion typical of marine bivalves. The mantle/gill and foot have no known digestive role, yet their ²¹⁰Po specific activities increased after 24 h. It is proposed that this increase in ²¹⁰Po specific activity was related to ²¹⁰Po being incorporated into these tissues from ²¹⁰Po assimilated from I. galbana during extracellular digestion. It is proposed that the linear loss of ²¹⁰Po previously accumulated by control mussels was related to the continual state of renewal and replacement of cellular proteins, with ²¹⁰Po turnover and metabolism governed by protein turnover and metabolism. M. edulis' assimilation efficiency of ²¹⁰Po from the ²¹⁰Po-labelled alga was calculated to be 17.2 ± 2.1%, and thus similar to that of Ag, Cd, Co, Se and Zn by bivalves from other marine algae species. It is proposed that the assimilation efficiency of ²¹⁰Po is a function of protein assimilation. Received: 27 August 1998 / Accepted: 3 September 1999     

Effect of Cd on accumulation and loss of 210Po in the mussel Mytilus edulis

As a result of ²¹⁰Po's previously identified association with sulphur-rich proteins, metallothioneins could have a significant effect on the behaviour and fate of ²¹⁰Po in molluscs. Starved control and cadmium-exposed mussels, Mytilus edulis, were fed ²¹⁰Po-labelled algae (Isochrysis galbana) for 5 d and then allowed to depurate in clean sea water. Cadmium-exposed M. edulis accumulated less ²¹⁰Po in the digestive gland and the remainder of the tissue than control mussels, although this was due to a decrease in tissue weight. More than 40% of ²¹⁰Po was identified as being associated with high molecular weight and heat-treated cytosol proteins in M. edulis. Mussels in a starved state are known to recycle as much as 90% of their amino acids. It is proposed that ²¹⁰Po associated with these and other proteins is recycled, explaining why no significant loss of ²¹⁰Po was observed from the remainder of the tissue in either control or Cd-exposed mussels. Cadmium-induced metallothioneins had no effect on the distribution of ²¹⁰Po in M. edulis; <5% associated with the cytosolic fraction was considered to principally contain metallothioneins. It is suggested that ²¹⁰Po's apparent relationship with metallothioneins is coincidental rather than connected with its role in the regulation of metals. Received: 30 March 1998 / Accepted: 3 August 1998     

Tissue and sub-cellular distribution of Fe,Cu, Zn and 210Po in the abalone Haliotis rubra

The tissue and sub-cellular distribution of Fe, Cu, Zn and the naturally occurring radionuclide polonium-210 was determined in the gastropod mollusc Haliotis rubra collected from Western Port Bay, Australia, between March and July 1988. The highest concentrations of the metals, with the exception of Cu, were found in the digestive gland. Copper was more uniformly distributed, with tissues that are more vasculated having higher concentrations. Ultrastructural examination of the digestive gland, gill and kidney showed dense membrane-bound granules within the cytoplasm. Elemental analysis of the granules by electron probe x-ray microanalysis indicated that the granules in the digestive gland and gill contained high concentrations of iron, with small amounts of copper and zinc. In contrast, the metal-containing granules in the kidney were predominantly composed of iron, copper and phosphorus, with variable contributions of sodium potassium, and calcium. Homogenisation and fractionation of the digestive gland by differential centrifugation confirmed that approximately 80, 10, 90 and 50% of the total homogenate Fe, Cu, Zn and ²¹⁰Po, respectively, sedimented at 1200xg. In the haemolymph, all the elements studied were associated with the soluble high molecular weight component of the serum, not with the amoebocytes. ²¹⁰Po was present in the mucus-secreting hypobranchial glands at about half the concentration found in gill tissue.     

Timing of septal formation in two species of Nautilus based on radiometric and aquarium data

Growth rates of four Nautilus scrobiculatus Lightfoot and three N. pompilius Linnaeus captured in Papua New Guinea in 1985 were measured using a chronology based on the naturally occurring radionuclides ²¹⁰Pb and ²¹⁰Po. The age of the las septum in mature specimens of both species was more than one year, whereas the time of septal formation in a submature specimen of N. pompilius was ca 180 d. The ²¹⁰Po/²¹⁰Pb method was also used to determine the growth rates of four immature N. pompilius captured in the Philippines in 1983 before and after introduction into an aquarium. Introduction into the aquarium was marked by a dramatic decrease in the activity of ²¹⁰Pb of the septa, the formation of a black line on the exterior of the shell, and a reduction in the spacing of adjacent septa in two specimens. Based on the number of septa formed in the aquarium, the average time of septal formation ranged from 50 to 80 d. These estimates were consistent with those calculated from the ²¹⁰Po/²¹⁰Pb activity ratios of the septa that formed in the aquarium, thus providing a check on the radiometric method. The average time of septal formation just prior to introduction into the aquarium appears, within the uncertainty of the radioactive measurements, to have been similar to that in the aquarium, indicating no dramatic alteration in the growth rate of these specimens.     

Lead-210 and Beryllium-7 in the Aerosol Particles Around Taiwan Off-Shore Areas

Abstract

Distributions of ²¹⁰Pb and ⁷Be in the aerosol particles of different size fractions were measured around Taiwan offshore areas from October, 1994 to October, 1995. the size distribution and abundance of the aerosol particles showed both spatial and temporal variations. the particle concentrations off northwestern Taiwan were more than twice as those off northeastern Taiwan both in November and March, and the values were much higher in November than in March for both areas. the measured particle concentrations, except for one sample with an unusually high value, ranged from 10 to 83 μOgm ^?3 in the study areas. the ²¹⁰Pb concentrations in the aerosol particles filtered from the air mass varied between 20 × 10^?3 and 72 × 10^?3 dpm m^?3 (1dpm = 0.45 pCi). the ²¹⁰Pb concentrations in the area off southwestern Taiwan appeared somewhat higher than in other areas and were probably contributed by the land air from Taiwan which contains higher ²¹⁰Pb in winter. the ²¹⁰Pb concentrations off northern Taiwan were low in November when the aerosol concentrations were high, but they were high in March when the aerosol concentrations were low.

Based on the ⁷Be monitoring records of 20 years on the aerosol particles of the island by the Taiwan Radiation Monitoring Center, the mean settling rate averaged 0.91, 0.79 and 0.68 cm s^?1, respectively, in northern, central and southern Taiwan. with these values and the ²¹⁰Pb concentrations in the aerosols, the ²¹⁰Pb flux was determined to be between 0.58 and 2.30 dpm cm^?2y^?1, with an average of 1.19 dpm cm^?2y^?1. Excluding the highest value due to its extremely high ²¹⁰Pb and aerosol concentrations, the average is reduced to 1.05 dpm cm^?2y^?1. the activity median diameters (AMD) for ²¹⁰Pb in the study areas were between 0.69 and < 0.49 μM with a mean of 0.5 öm based on ²¹⁰Pb distributions in different particle size fractions. Thus, ²¹⁰Pb was preferentially adsorbed on to the submicron particles. ⁷Be in the study areas showed a good correlation with ²¹⁰Pb in total activity although the two nucides had different sources.     

Risk assessment of heavy metal contamination in shrimp farming in Mai Po Nature Reserve, Hong Kong

An ecological survey was carried out to determine the sediment concentrations of nutrients and heavy metals and bioaccumulation of heavy metals in fish and shrimp including tilapia (Oreochromis mossambicus×O. nilotica), grey mullet (Mugil cephalus), gei wai shrimp (Metapenaeus ensis) and caridean shrimp (Macrobrachium nipponensis) in the traditional tidal shrimp ponds (gei wais) of Mai Po Nature Reserve, Hong Kong. The sediments collected from the landward sites contained higher nutrient contents, as well as zinc (Zn), chromium (Cr), copper (Cu), nickel (Ni) and cadmium (Cd) than those collected from the seaward sites, but vice versa for lead (Pb) and mercury (Hg). However, the concentrations of all metals were exceptionally high in the two sites located outside the reserve, suggesting that waters from Deep Bay might be the possible source of metal contamination affecting the reserve. All metals studied seemed to accumulate in the viscera of fish. Body size was the determining factor for the accumulation of heavy metals in caridean shrimp and gei wai shrimp but not fish. Concentrations of the metals studied in tissues of grey mullet and gei wai shrimp were found to be safe for human consumption. Concentrations of Cr in tilapia whole body (0.68–1.10 mg kg⁻¹ wet weight) were close to or over the guideline value of 1 mg kg⁻¹ set by the Food Adulteration (Metallic Contamination) Regulations of Hong Kong. Tilapia flesh and small caridean shrimp collected from gei wais were contaminated by Cr and Pb but still fit for human consumption. Caution is required if large caridean shrimp is to be consumed in large amounts continuously because the concentration of Pb exceeded the maximum permitted concentration (6 mg kg⁻¹). The rather high Cr concentrations in tilapia whole body should not be overlooked as the fish will serve as a food source for migratory birds visiting the site.     

In vivo accumulation of radioactive polonium by the giant kelp Macrocystis pyrifera

The in vivo accumulation rate of ²¹⁰Po by Macrocystis pyrifera (L) Ag. has been determined by the tagging of specific parts of young, growing lamina in La Jolla kelp beds and their subsequent collection for ²¹⁰Po analysis. The rates of accumulation for observed and growth-corrected data were, respectively, 0.78x10^-9 pCi/cm² sec (1.73x10^-9 dpm/cm² sec) and 1.17x10^-9 pCi/cm² sec (2.60x10^-9 dpm/cm² sec). Invert, but biologically foulable, glass-slide surfaces exposed to the kelp bed environment yielded ²¹⁰Po accumulation rates of 0.64x10^-9 pCi/cm² sec (1.42x10^-9 dpm/cm² sec), slightly less than those of M. pyrifera. Distinction is made between observed net accumulation rate and gross rates or total flux. Several factors contributing to the final net accumulation rate are discussed.     

Ground water contamination with 238U, 234U, 235U, 226Ra and 210Pb from past uranium mining: cove wash,Arizona

The objectives of the study are to present a critical review of the ²³⁸U, ²³⁴U, ²³⁵U, ²²⁶Ra and ²¹⁰Pb levels in water samples from the EPA studies (U.S. EPA in Abandoned uranium mines and the Navajo Nation: Red Valley chapter screening assessment report. Region 9 Superfund Program, San Francisco, 2004, Abandoned uranium mines and the Navajo Nation: Northern aum region screening assessment report. Region 9 Superfund Program, San Francisco, 2006, Health and environmental impacts of uranium contamination, 5-year plan. Region 9 Superfund Program, San Franciso, 2008) and the dose assessment for the population due to ingestion of water containing ²³⁸U and ²³⁴U. The water quality data were taken from Sect. “Data analysis” of the published report, titled Abandoned Uranium Mines Project Arizona, New Mexico, Utah–Navajo Lands 1994–2000, Project Atlas. Total uranium concentration was above the maximum concentration level for drinking water (7.410–1 Bq/L) in 19 % of the water samples, while ²³⁸U and ²³⁴U concentrations were above in 14 and 17 % of the water samples, respectively. ²²⁶Ra and ²¹⁰Pb concentrations in water samples were in the range of 3.7 × 10^?1 to 5.55 × 102 Bq/L and 1.11 to 4.33 × 102 Bq/L, respectively. For only two samples, the ²²⁶Ra concentrations exceeded the MCL for total Ra for drinking water (0.185 Bq/L). However, the ²¹⁰Pb/²²⁶Ra ratios varied from 0.11 to 47.00, and ratios above 1.00 were observed in 71 % of the samples. Secular equilibrium of the natural uranium series was not observed in the data record for most of the water samples. Moreover, the ²³⁵U/^totalU mass ratios ranged from 0.06 to 5.9 %, and the natural mass ratio of ²³⁵U to ^totalU (0.72 %) was observed in only 16 % of the water samples, ratios above or below the natural ratio could not be explained based on data reported by U.S. EPA. In addition, statistical evaluations showed no correlations among the distribution of the radionuclide concentrations in the majority of the water samples, indicating more than one source of contamination could contribute to the sampled sources. The effective doses due to ingestion of the minimum uranium concentrations in water samples exceed the average dose considering inhalation and ingestion of regular diet for other populations around the world (1 μSv/year). The maximum doses due to ingestion of ²³⁸U or ²³⁴U were above the international limit for effective dose for members of the public (1 mSv/year), except for inhabitants of two chapters. The highest effective dose was estimated for inhabitants of Cove, and it was almost 20 times the international limit for members of the public. These results indicate that ingestion of water from some of the sampled sources poses health risks.     

Confirmation of longevity in Sebastes diploproa (Pisces: Scorpaenidae) from 210Pb/226Ra measurements in otoliths

Fish ages are often estimated by assuming an annual frequency of the band-like, growth-zones recorded in the largest of their otoliths, the sagittae. The total number of growth-zones are normally determined either by counting external growth-zones (whole otolith technique) or by examining otolith cross-sections (otolith section technique). The two techniques do not always yield the same age, however, particularly in older specimens of certain fishes. To resolve this problem, otoliths of the splitnose rockfish Sebastes diploproa were examined morphologically and were assayed for their natural radionuclide concentrations. Four age groups of otoliths were identified based on growth-zone counting; in the first three, whole otolith and otolith section age estimates agreed, while in the fourth, the otolith section age substantially exceeded the whole otolith age. Radiometric analysis demonstrated that all otoliths were deficient in ²¹⁰Pb activity relative to ²²⁶Ra activity with the deficiency decreasing with increasing number of growth-zones. The magnitude of the ²¹⁰Pb/²²⁶Ra radioactive disequilibrium in each otolith group, when compared to the number of growth-zones and the otolith weight histories derived with the two techniques, identifies the growth-zones revealed by otolith sections as annual features. Thus when otolith section age exceeds whole otolith age (usually occurring after 20 to 25 yr of age for this species), the otolith section technique is the correct method of age determination. Estimates of longevity in the genus Sebastes near 80 yr are therefore confirmed.     

Toxicity and distribution of Aroclor® 1254 in the pink shrimp Penaeus duorarum

The polychlorinated biphenyl Aroclor^® 1254 was released in an accidental leakage of heat-exchange fluid from an industrial plant, into the Escambia River, near Pensacola, Florida, USA. This material was carried downstream, and is now found in the fauna of Escambia Bay and its contiguous waters, prime nursery areas for fishes and invertebrates such as penaeid shrimp. The significance of pollution by this chemical was assessed by establishing toxicity levels, determining routes of entry, and investigating its movement and distribution in various tissues of shrimp under controlled conditions in the laboratory. Aroclor 1254 added to the water was toxic to the juvenile pink shrimp Penaeus duorarum at a concentration of 1.0 part per billion within 15 days, but was less® Registered trademark, Monsanto Company, St. Louis, Missouri, Mention of commercial products does not constitute endorsement by the Environmental Protection Agency.Contribution No. 128, Gulf Breeze Laboratory.     

Distribution and abundance of penaeid shrimps in a hypersaline lagoon in northwestern Mexico,emphasizing the brown shrimp <Emphasis Type="Italic">Farfantepenaeus californiensis</Emphasis> life cycle

Life histories of penaeid shrimp have been classified according to the preferred habitats of postlarval, juvenile, and adult stages, ranging from exclusively estuarine to exclusively offshore waters. Brown shrimp Farfantepenaeus californiensis migrate to an offshore habitat at the juvenile stage or even a smaller body size. This paper presents results of monthly samplings from 24 stations over 1 year in the Agiabampo Lagoon complex, a hypersaline lagoon in northwestern Mexico. Five species of penaeid shrimp were identified, with brown shrimp the most abundant during the year of sampling. Results suggest that residency of brown shrimp inside this lagoon is longer than reported in previous studies. An interaction between length and environmental variables (near-surface temperature, salinity, and rainfall) appear to be cues concerning migration.

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Delivery of dietary components to larval shrimp (Penaeus vannamei) by means of complex microcapsules

Efficient delivery of nutrients is necessary for the successful study of aquatic larval nutrition. Conventional artificial food particles for larval shrimp (Penaeus vannamei) have poor water stability and poor nutrient retention or both. We developed a novel food particle type that retained low-molecular weight, water-soluble nutrients (vitamins and glucose) within lipid-wall microcapsules embedded with dietary ingredients in particles of gelled alginate-gelatin. The combination of lipid-wall microcapsules (LWMs) embedded in gelled food particles was termed complex microcapsules (CXMs). Eighty-five percent of ¹⁴C-activity associated with encapsulated ¹⁴C-glucose was retained by CXMs (after 18 h of suspension in seawater). Bioavailability of CXM-encapsulated molecules was demonstrated by release of encapsulated dye marker into the gut lumen of larval shrimp, and by uptake of ¹⁴C from encapsulated ¹⁴C-glucose. Minimum ingestion rates, calculated from ¹⁴C-uptake for larval shrimp (Mysis-1 through Postlarva-2) fed CXMs, ranged from 48 to 99 g dry wt larva^-1 d^-1, and were similar to literature values reported for ingestion of live rotifers by penaeid larvae. Complex microcapsules described in this study will be a valuable new tool for studying nutrition of suspension-feeders in that both micro-and macronutrients can be delivered to these animals by one particle type.     

Lethal and sublethal effects of a simulated salt brine effluent on adults and subadults of the shrimps Penaeus setiferus and P. aztecus

Lethal and certain sublethal effects of salt brines on adults and subadults of two species of penaeid shrimps, Penaeus setiferus and P. aztecus, were examined to evaluate the potential impact of ocean disposal of brine from solution mining of salt domes. Brines, prepared from dome salt or synthetic sea salt diluted with Brazos River (Texas, USA) water or deionized water, were mixed with seawater and dalivered from a proportional diluter to shrimp held (usually) at 25°C. For each combination of species, salt, and diluent, 90-individual trials were conducted in the fall and spring. The effects of temperature were evaluated separately. Median lethal time was strongly dose-dependent: Median lethal concentrations at 48 and 96 h were 654±42 (95% confidence interval) and 540±41 mOsm kg^-1 above ambient seawater, respectively, well above the worst-case predictions for the brine-disposal area. Salt type, diluent type, season or species did not significantly affect brine lethality. Mortality was higher for both species at 30°C and lower for P. setiferus and higher for P. aztecus below 25°C. Lethal brine doses produced tachycardia after 6 (P. setiferus) or 12 h (P. aztecus) of brine exposure. Opacity of abdominal muscles increased with brine concentration. Lethal brine concentrations evoked hyperactivity after 0.75–1.5 h of exposure, significant failure to orient after 6 h and a reduction in general activity after 12 h. Behavior and osmoregulation suggest higher sensitivities to brines made with dome salt or river water and in shrimp tested during the cool seasons.