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.     

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.     

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 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.     

Selective predation on mature male Byblis japonicus (amphipoda: Gammaridea) by the barface cardinalfish,Apogon semilineatus

Ontogenetic change of habitat depths of Nautilus pompilius in the Philippines (Tañon Strait) and Fiji is considered by comparing ¹⁸O/¹⁶O ratios in septa and cameral fluid of live-caught specimens and ambient sea-water. ¹⁸O values of cameral liquid become heavier with decreasing volume within a chamber, which may be due to isotopic fractionation during discharge across the siphuncular wall. All of the seven Philippine and Fiji specimens analyzed show a distinct change in ¹⁸O from light values in the first seven septa to heavier values in the succeeding septa. Two different isotopic temperature scales are obtained for the Fiji and Philippine populations, suggesting a differential vital effect of metabolism between them. Sightly light ¹⁸O values in Septa 1 to 7 and hatching at relatively high temperatures in aquaria both suggest that N. pompilius hatch at the shallowest depths within their inhabitable vertical range. Depths of postembryonic animals in the Philippines and Fiji waters estimated from the isotopic temperature-depth diagrams range from 120 to 160 m and from 440 to 520 m, respectively, both of which correlate well with capture records. More than several tens of small-scale ¹⁸O cycles are detected in the sequence of nacreous layers within the single septum of a submature Philippine specimen. This can be interpreted as reflecting daily vertical migration.     

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 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.     

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     

Natural tracers in dietary studies: data for 210Po and 210Pb in decapod shrimp and other pelagic organisms in the Northeast Atlantic Ocean

Measurements of the concentrations of the naturally-occurring radioactive nuclides ²¹⁰Po and ²¹⁰Pb in a large number of pelagic organisms from the Atlantic Ocean made in the spring/summer of 1984 and 1985 are reported. Marine shrimp are particularly well represented, and in many cases data were obtained for shrimp hepatopancreas, stomach-contents, and posterior intestine plus contents, as well as for whole individuals. The wide ranges found in ²¹⁰Po concentrations group into categories: the shrimp, for example, divide into four categories, two penaeid and two carid. These groupings are explained on the basis of variations in diet between the different categories. A clear difference was also observed between the ²¹⁰Po levels in shrimp of similar species and size from opposite sides of an oceanographic front; this difference too can be explained plausibly in terms of a change in certain penaeid shrimp, and attention is drawn to the need for investigation of cytological and/or genetic effects which could possibly be caused by the very high natural radiation doses to which such organisms are exposed.     

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.     

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.     

Variations in time budget of the polychaete Nereis virens as a function of density and acclimation after introduction to a new burrow

Behavioural patterns of Nereis virens (Sars) were monitored in the laboratory to determine variations in the time budget (i.e., percentage of time spent in various activities) as a function of density and acclimation period (number of days following the introduction of worms into experimental enclosures). Experiments were carried out from 17 June to 13 August 1989, using worms collected from intertidal sand flats of l'Anse à l'Orignal in the lower Saint Lawrence estuary, Canada. Inactivity, locomotion and irrigation were, in that order, the most frequent behaviours for solitary individuals. Correlations between the time spent in the various activities and time of day indicated a general increase in activity during the night (21.00 to 06.00 hrs). Locomotory activity increased at night, inactivity during the daytime. A general sequence of behaviour of N. virens was revealed. Inactivity, locomotion and irrigation were still the most frequent activities for individuals observed in high-density conditions, but their respective importance differed significantly (locomotion, irrigation and inactivity, in that order). There was also less variability in the time spent for each behaviour in the high-density aquarium. Comparisons between behaviour and time of day suggested fewer correlations among the different components of the time budgets under conditions of high density. Finally, the time budget varied but little over time (number of days alloved for acclimation) in the low-density aquarium as opposed to the high-density aquarium. Our study revealed that population density and acclimation are important in determining behavioural patterns of N. virens.     

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.     

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.     

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.     

Sediment accumulation and bio-diffusion mixing rates derived from excess <Superscript>210</Superscript>Pb and <Superscript>137</Superscript>Cs profiles in sediment cores of Mumbai Harbor Bay

Bio-diffusion mixing rates (D_b) were estimated from depth profiles of excess ²¹⁰Pb and ¹³⁷Cs in three sediment cores collected from Mumbai Harbour Bay (MHB) using a steady state vertical advection - diffusion model. The mean of ²¹⁰Pb and ¹³⁷Cs derived D_b values along the studied area were obtained to be about 23 and 36 cm²y^?1 respectively. These derived values were within the range of literature values reported for other equivalent environment internationally. The relatively higher D_b values for ¹³⁷Cs profiles demonstrated that particles have diffused more intensely within the surface layer of sediments over 1 year. Conversely, low D_b values for ²¹⁰Pb indicate slow mixing rates in the sediment profile which might be resulted from low ²¹⁰Pb flux and diffusion of ²²²Rn to the seafloor. The significant differences between ²¹⁰Pb and ¹³⁷Cs derived D_b values among cores indicate that there appeared to be as regional differences in sediment properties and local variability in the intensity of seafloor mixing. Furthermore, D_b values also depend on differences in characteristic time and depth scales of radionuclides in cores, benthic fauna abundances, organic carbon flux to the sediments and primary production in overlying surface waters. Comparison of ²¹⁰Pb derived D_b values with those calculated from ¹³⁷Cs distributions reveals better agreement for core 2 than core 1 and 3. The agreement may be fortuitous because ¹³⁷Cs appears significantly deeper than ²¹⁰Pb in all cores. It was also observed that D_b values increases as sediment accumulation rate increases for both radionuclide.     

Venoms from six species of marine fish: lethal and hemolytic activities and their neutralization by commercial stonefish antivenom

A specimen of the stonefish Synanceja verrucosa was captured in Okinawa in March 1988. Live specimens of the scorpionfish Inimicus japonicus were purchased from the Tokyo Central Wholesale Market in November 1988 and those of four species of zebrafish Pterois lumulata, P. volitans, P. antennata and Dendrochirus zebra from an aquarium in December 1988. Crude venoms were extracted from dorsal spines of the six species. All venoms exhibited lethal activity against mice and hemolytic activity specific for rabbit erythrocytes. The lethal activity (or hemolytic activity) of each venom was very unstable to freezing, lyophilization and heating. Both lethal and hemolytic activities of S. verrucosa venom were remarkably neutralized by the commerical stonefish (Synanceja trachynis) antivenom. This antivenom was also effective, to some extent, in counteracting the other venom activities. The neutralizing capacities of the antivenom were calculated to be 7310 LD₅₀ ml^-1 for S. verrucosa venom and 1 220 to 2 990 LD₅₀ ml^-1 for the other venoms. Results of neutralization tests suggest that venoms from the six species were comparable in terms of antigenecity.     

Human teeth as historical biomonitors of environmental and dietary lead: some lessons from isotopic studies of 19th and 20th century archival material

The lead isotopic composition of various sections (crown, crown base, root) of teeth was determined in specimens collected from 19th century skulls preserved in museum collections and, upon extraction or exfoliation, from humans of known ages residing in Scotland in the 1990s. For most 20th century samples, calculation of accurate crown-complete or root-complete dates of tooth formation ranging from the 1920s to the 1990s enabled comparison of ²⁰⁶Pb/²⁰⁷Pb ratios for teeth sections (crown base root) with corresponding decadally averaged data for archival herbarium Sphagnum moss samples. This showed that the teeth sections had been significantly influenced by incorporation of non-contemporaneous (more recent) lead subsequent to the time of tooth formation, most probably via continuous uptake by dentine. This finding confirmed that separation of enamel from dentine is necessary for the potential of teeth sections as historical biomonitors of environmental (and dietary) lead exposure at the time of tooth formation to be realised. Nevertheless, the mean 19th century value of 1.172±0.007 for the ²⁰⁶Pb/²⁰⁷Pb ratio in teeth was very similar to the corresponding mean value of 1.173±0.004 for 19th century archival moss, although relative contributions from environmental sources – whether direct, by inhalation/ingestion of dust contaminated by local lead smelting (²⁰⁶Pb/²⁰⁷Pb~1.17) and coal combustion (²⁰⁶Pb/²⁰⁷Pb~1.18) emissions, or indirect, through ingestion of similarly contaminated food – and drinking/cooking water contaminated by lead pipes of local origin, cannot readily be determined. In the 20th century, however, the much lower values of the ²⁰⁶Pb/²⁰⁷Pb ratio (range 1.100–1.166, mean 1.126±0.013, median 1.124) for the teeth collected from various age groups in the 1990s reflect the significant influence of imported Australian lead of lower ²⁰⁶Pb/²⁰⁷Pb ratio (~1.04) and released to the environment most notably through car-exhaust emissions arising from the use of alkyl lead additives (²⁰⁶Pb/²⁰⁷Pb~1.06–1.09) in petrol in the U.K. from ca. 1930 until the end of the 20th century.     

DNA fingerprints of Caulerpa taxifolia provide evidence for the introduction of an aquarium strain into the Mediterranean Sea and its close relationship to an Australian population

The occurrence of Caulerpa taxifolia in the Mediterranean Sea was reported for the first time in 1984. Since then the alga has spread rapidly and is now considered to be a potential threat to sublittoral ecosystems. Two hypotheses on the origin of the Mediterranean strain of C. taxifolia have been discussed in the literature. One hypothesis assumed migration of the alga from the Red Sea, the other introduction via a public aquarium. The hypothesis of a descent from an aquarium strain has been supported strongly by recent studies based on DNA sequences. The DNA fingerprints of C. taxifolia presented here also provide evidence for the descent of the Mediterranean C. taxifolia from an aquarium strain. Furthermore, the present study shows that a strain of C. taxifolia from Manly Harbour/Moreton Bay (Australia) is closely related to the aquarium/Mediterranean strain. The feasibility of detecting similar genotypes by restriction digests of total DNA is demonstrated, which will facilitate the ongoing search for further relatives of Mediterranean C. taxifolia. Received: 20 June 2000 / Accepted: 27 September 2000