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1.
Abstract. A number of recent field‐based studies have investigated the possible functions of covering behaviour in a range of echinoid species. Some of these have found important relationships between covering behaviour and environmental factors, such as light (in particular, ultra‐violet light) and covering item availability. However, these studies have often shown considerable within‐species variation, thus making covering functionality both within and between species difficult to interpret. The present study experimentally investigates individual variability in covering behaviour characteristics of the sea urchin Paracentrotus lividus (Lamarck). Data were collected bimonthly over a 1‐year period at Lough Hyne, Ireland, by observing P. lividus in outdoor aquaria. Significant variations in covering behaviour characteristics were observed as a function of individual size and mobility but not as a function of sex. A significant relationship between water temperature, mobility and covering behaviour was also found and is hypothesized to have implications for grazing activity in P. lividus. In contrast to previous field studies of P. lividus at Lough Hyne, no summer ‘peak’ in the proportion of individuals covering was observed. However, there was a significant relationship between local solar radiation and ‘time to first cover’. Overall, these data highlight (i) the ecological significance of individual variation in P. lividus covering behaviour and (ii) the importance of investigating multiple factors as potential determinants of echinoid covering behaviour.  相似文献   

2.
Most of the studies on biological and ecological effects associated with brine discharge into the marine environment are related to the operation of desalination plants, for the production of freshwater. In this study we analysed the biological effects of a brine effluent from a completely different source, produced from the lixiviation of rock salt caves, for the creation of natural gas storage caverns. Lethal and sub-lethal endpoints following exposure to the brine were studied in a range of macrofauna species characteristic of the soft and hard bottom habitats in the vicinity of the discharge area, namely the isopod Eurydice pulchra, the annelids Sabellaria alveolata and Ophelia radiata, the sea-urchin Paracentrotus lividus and the bivalve Mytilus galloprovincialis. In a first series of experiments, brine, with salinity above 300, was diluted in distilled water to a salinity value close to that of the seawater in the discharge area (salinity 36) and, surprisingly, none of the exposed species was able to survive or develop into viable larvae. A second series of experiments exposed the species to brine diluted with seawater, simulating more realistic discharge circumstances. All the tested species at all the measured endpoints (adult survival, larval abnormal development, sperm fertilization success) showed negative biological effects in brine solutes always at a lower salinity than that of a salinity control obtained with concentrated seawater. The sub-lethal experiments with larval development of P. lividus, S. alveolata and M. galloprovincialis, and the fertilization success of P. lividus gave EC50 values for the brine solute with salinity in the range of 40.9–43.5, whereas the EC50 values for the concentrated seawater were in the range of salinity 44.2–49.0. It is hypothesised that differences in the ionic composition of the brine cause the inability of the species to tolerate the exposure to brine.  相似文献   

3.
Juvenile coho salmon, Onchorynchus kisutch, were exposed to 95mTc in both saltwater and freshwater to study the biokinetic behavior of this element in an anadromous fish. In freshwater, equilibrium whole-body concentration factors (CF5) ranged from 28 to 32 in two separate experiments, in sharp contrast to an equilibriumCF of < 5 in saltwater. While the uptake kinetics were unimodal in saltwater, in freshwater, biomodal uptake kinetics were observed.Technetium-95m retention was biphasic in freshwater depuration experiments, an initial rapid loss of 21% to 26% of the steady-state activity with an elimination half-life of 3 to 5 days was followed by a slower loss rate, with a whole-body elimination half-life ranging from 23 to 33 days. In saltwater, retention was monophasic with an elimination half-life of 5–16 days. Dramatic decreases in 95mTc body burdens when freshwater-labeled fish are transferred to Tc-labeled saltwater indicate that the changes in physiology accompanying saltwater acclimation lead to the loss of 95mTc.  相似文献   

4.
Uptake and loss kinetics of Zn, Ag, Cd, 134Cs, and 241Am by shoots of the seagrass Posidonia oceanica and fronds of the green alga Caulerpa taxifolia were determined in controlled laboratory radiotracer experiments using low contaminant concentrations. The two species accumulated most of the elements efficiently. The only exceptions were 134Cs in both P. oceanica and C. taxifolia and Cd in C. Taxifolia (concentration factors 6.4). Steady state in uptake was reached in C. taxifolia for each element except Ag. In P. oceanica, steady state was noted for the uptake of Ag and 134Cs whereas Zn, Cd, and 241Am were linearly accumulated during the course of the experiment (15 d). With respect to relative metal bioavailability, the different compartments of P. oceanica shoots were generally ranked in the order: leaf epiphytes > adult LEAVES = intermediate leaves > leaf sheaths. The long-lived component of the loss kinetics for each element in P. oceanica was characterized by a relatively short biological half-life (Tb1/2 28 d). However, observations for the individual compartments indicated that adult leaves had a high retention capacity for Ag and 134Cs, with virtually 100% retained after 21 d in uncontaminated sea water. In C. taxifolia, the long-lived component of the loss kinetics for each element was characterized by a Tb1/2 value that was not significantly different from infinity, an observation which suggests that a substantial fraction of the metal or radionuclide incorporated during a contamination event would be irreversibly bound by this algal species.  相似文献   

5.
The fishery for the edible sea urchin Paracentrotus lividus is of great importance to many European regions, although in some of them this species has shown a wide scale decline in recent years. This paper reports on direct (on P. lividus) and indirect (on the co-occurring but not fished echinoid, Arbacia lixula) effects of sea urchin harvesting in shallow rocky reefs in North-western Sardinia (Italy, central-western Mediterranean Sea), where this activity is intensively practised. Density, size (test diameter), and biomass of both species were assessed in autumn 2004 at two locations impacted by P. lividus fishery, and at two controls within an adjacent Marine Protected Area. Density of P. lividus and A. lixula was significantly greater at the controls than at the exploited locations. The average test diameter of P. lividus was also significantly larger at the controls, where large-sized specimens (i.e. >5 cm) were notably more abundant. The average size of A. lixula did not significantly differ between the impacted locations and the controls. The average biomass of P. lividus was significantly greater at the controls than at the exploited locations, whereas no differences were detected for A. lixula. These results reveal the existence of a heavy fishing impact on P. lividus in North-western Sardinia and the need for regulation of its harvesting to prevent severe direct effects on its populations. Since no indirect effects on A. lixula have been detected, it could be hypothesized that this species did not benefit from P. lividus fishery due to an only moderate competition for habitat and resources between these two echinoids. Implications for management of edible sea urchin fishery are also discussed.  相似文献   

6.
The spatial and temporal distribution of cadmium (Cd) and phosphate in the Southern Ocean are related to biology and hydrography. During a period of 18 days between transects 5/6 and 11, a phytoplankton spring bloom developed in the Polar Frontal region. Upper water Cd concentrations were not depleted and ranged from 0.2 to 0.8 nM at about 10 m depth. These relatively high Cd concentrations are attributed to upwelling of Upper Circumpolar Deep Water (0.5–1.2 nM in the core) in combination with low biological productivity (0.2 to 0.3 mg m−3 chlorophyll-a, 0.3 g C m−2 d−1). Total particulate Cd concentrations at 40 m depth were between 0.02 and 0.14 nM with the maximum in concentration in the Polar Frontal region. Most of the particulate Cd at this depth (85–94%) was detected in the first phase of a sequential chemical leaching treatment which includes adsorbed Cd as well as Cd incorporated in algae. The Polar Frontal region was characterized by minima in Cd concentration and Cd/phosphate ratio of seawater at both transects; values were the lowest at transect 11 after development of the spring bloom which was dominated by diatoms. This decreasing Cd/phosphate ratio in seawater during spring bloom development was attributed to preferential Cd gross uptake which more than compensated the process of preferential Cd recycling. Within the Upper Circumpolar Deep Water, Cd showed a maximum in concentration similar to that of the major nutrients. Both the Cd concentration and the Cd/phosphate ratio of the deeper water increased in southern direction, from 0.4 to 0.7 nM and from 0.2 to 0.3 nM/μM, respectively. Antarctic Intermediate Water has a Cd concentration of 0.21 nM with a Cd/phosphate ratio of 0.10 nM/μM. In Antarctic Bottom Water, Cd concentrations ranged from 0.60 to 0.82 nM.  相似文献   

7.
The bivalve molluscs Mytilus californianus and Crassostrea gigas were exposed to filtered seawater containing the isotope 95mTc added as pertechnetate (TcO4?) to study the biokinetic behaviour of this element. Whole body concentration factors for both organisms at equilibrium were small (CF = 1·3–1·5); individual organ concentration factors were highest for the visceral mass in both. Loss rates determined both in the laboratory and under field conditions were biphasic for both molluscs; initial loss of Tc was rapid with slightly more than 50 % of the initial label being lost within 10 days. Thereafter, loss rates decreased and whole body biological half-lives ranged from 80 to 134 days. Neither I? nor IO3? affected the uptake of Tc by M. californianus even when concentrations of these anions exceeded those normally present in seawater by two orders of magnitude.  相似文献   

8.
《Marine Chemistry》2001,74(1):65-85
Here it is demonstrated that both Porphyra spp. and Enteromorpha spp. of macro-algae display similar and very marked seasonal variations in their concentration factor (CF) of Cu, Pb, Cd and Hg in field conditions. The CF variations are specific for each metal and reproducible over several years. The way variations in the biological activity affect the equilibrium and kinetics of the interaction between trace metals and live algae was studied in vitro. Natural seawater was used as the culture medium. Voltammetry was used for the determination of natural organic ligands and trace metals except Hg, which was determined by mercury cold vapour after on-line pre-concentration. Titrations with the relevant metal demonstrated that the maximum binding capacity of the algae was not significantly dependent on the season for Pb (ca. 100 μmol gdry algae−1), Cd (ca. 50 μmol g−1) and Hg (80–100 μmol g−1). Marked seasonal variations were observed for Cu (ca. 40 μmol g−1 in January; 70 μmol g−1 in May; and 100 μmol g−1 in August). The conditional stability constants of metal–algae complexation sites were seasonally independent and similar for both algae: logKMS′=8.5±0.3 (Cu), 5.6±0.2 (Pb), 5.3±0.2 (Cd) and 18.0±0.3 (Hg). Exudates with a strong Cu complexing capacity (logK′CuL=12.47±0.06) were determined in cultures with added Cu, Pb or Cd concentrations, and identified by cathodic stripping voltammetry (CSV) as cysteine or glutathione. All the tested metals promoted the liberation of exudates, both cysteine- and glutathione-like ligands were exuded in the presence of Cu, only cysteine-like ligands in the presence of Pb, and only glutathione-like ligands in the presence of Cd, the rise depending of the season of the year, particularly for Cu. Highest levels were produced in the presence of added Pb. When exposed to either 1- or 100-μM total dissolved metal concentrations, the metal uptake, and its rate, varied with the season and the algae.  相似文献   

9.
Cadmium is a biologically important trace metal that co-varies with phosphate (PO43− or Dissolved Inorganic Phosphate, DIP) in seawater. However, the exact nature of Cd uptake mechanisms and the relationship with phosphate and other nutrients in global oceans remain elusive. Here, we present a time series study of Cd and PO43− from coastal Antarctic seawater, showing that Cd co-varies with macronutrients during times of high biological activity even under nutrient and trace metal replete conditions. Our data imply that Cd/PO43− in coastal surface Antarctic seawater is higher than open ocean areas. Furthermore, the sinking of some proportion of this high Cd/PO43− water into Antarctic Bottom Water, followed by mixing into Circumpolar Deep Water, impacts Southern Ocean preformed nutrient and trace metal composition. A simple model of endmember water mass mixing with a particle fractionation of Cd/P (αCd–P) determined by the local environment can be used to account for the Cd/PO43− relationship in different parts of the ocean. The high Cd/PO43− of the coastal water is a consequence of two factors: the high input from terrestrial and continental shelf sediments and changes in biological fractionation with respect to P during uptake of Cd in regions of high Fe and Zn. This implies that the Cd/PO43− ratio of the Southern Ocean will vary on glacial–interglacial timescales as the proportion of deep water originating on the continental shelves of the Weddell Sea is reduced during glaciations because the ice shelf is pinned at the edge of the continental shelf. There could also be variations in biological fractionation of Cd/P in the surface waters of the Southern Ocean on these timescales as a result of changes in atmospheric inputs of trace metals. Further variations in the relationship between Cd and PO43− in seawater arise from changes in population structure and community requirements for macro- and micronutrients.  相似文献   

10.
Numerous studies of interactions between urchins and algae in temperate areas have shown an important structuring effect of sea urchin populations. These studies focused almost wholly on the effect of high urchin densities on laminarian forests. In contrast, algal communities below 5–6 m depth in the northwestern Mediterranean are characterised by low sea urchin densities (<5 ind m−2) and the absence of laminarian forests. No previous research has addressed sea urchin/algal interactions in this type of community. To determine the effect of the most abundant echinoid species, Paracentrotus lividus, on well-established algal communities in this area, we performed a removal–reintroduction experiment in rocky patches located between 13 and 16 m depth in the northwestern Mediterranean, where sea urchin densities ranged between 0.9 and 3.4 ind m−2. After 6 months, the cover of non-crustose algae was significantly higher in the plots from which sea urchins had been removed than in control plots (84 vs 67% cover). These removal plots reverted to their original state upon reintroduction of sea urchins. The non-crustose algae consisted of turfing and frondose forms, with the former representing some 70% of the non-crustose algal cover. Change in the cover of turfing algae was responsible for the significant increase in algal development in the sea urchin removal plots. The response of frondose algae to the treatment varied between algal species. It is concluded that grazing by P. lividus exerts a significant effect on habitat structure, even in communities with low sea urchin densities, such as those found in vast areas of the Mediterranean sublittoral.  相似文献   

11.
Accumulation and elimination of cadmium was investigated in the tellinid clam, Macoma balthica (L.). Accumulation of Cd was linear in soft tissues (0·35 μg g−1 day−1 dry weight) throughout a 29-day exposure period at 100 μg Cd litre−1. Loss of Cd, measured after transfer of experimentally-contaminated clams to clean seawater, was exponential and relatively slow (biological half-time, 70 days). In contrast, Cd uptake onto the shell of Macoma was characteristic of saturation kinetics, indicative of physical adsorption processes. Amounts of Cd accumulated by the shell were low, and the elimination rate rapid (half-time, 7 days) compared with soft tissues.Gel chromatographic profiles of cytosol extracts from control and experimental groups of M. balthica revealed that most of the Cd was bound to high molecular weight ligands, an unusual feature in bivalve molluscs. Although the proportion of cytosolic Cd associated with very low molecular weight ligands is small (< 15%) this pool may be important in regulating Cd fluxes in Macoma during uptake and elimination phases. No evidence was found of metallothionein (or similar metal-binding protein) involvement in Cd accumulation and storage in either field or laboratory exposed clams.The metabolism of Cd in M. balthica is different from that reported for other bivalve groups in several respects. In particular, the relatively slow rate of Cd accumulation in Macoma may be an important adaptive advantage for survival in contaminated areas and may compensate for the absence of a recognised detoxifying (MT) system in this species.  相似文献   

12.
Experiments on the uptake of Zn and Cd by synthetic hydrous Mn oxides were carried out in an ionic medium at pH 3.5 and at pH 4. A slight preference for uptake of Cd2+ over Zn2+ was observed with both birnessite and nsutite, the Cd/Zn ratio being different for each mineral. Subsequently, the desorption of Zn and Cd from the obtained products in artificial seawater was studied. In this medium Cd is desorbed from the Mn oxides to a much higher extent than is Zn. The latter observations can be satisfactorily explained by the large difference of complex formation for the two metals in seawater, slightly counteracted by the preferential uptake of Cd2+ over Zn2+. The order of magnitude of the Zn/Cd ratio in natural manganese nodules is compatible with the ratio calculated on the basis of experimental results, taking fair estimates of the actual inorganic Zn/Cd ratio in seawater and of the pH of deep ocean water.  相似文献   

13.
The present investigation focuses on population structure analysis of the purple sea urchin Paracentrotus lividus across the African Mediterranean coast, with the main aim of assessing the influence of the Siculo-Tunisian Strait on gene flow disruption in this highly dispersive echinoid species. For this purpose, patterns of morphological and genetic variation were assessed among its populations from the western and eastern Mediterranean coasts. A total of 302 specimens from seven Tunisian sites were collected and examined for morphometric variability at twelve morphometric traits. Concordant results, inferred from CDA (canonical discriminant analyses), pairwise NPMANOVA (non parametric multivariate analysis of variance) comparisons and MDS (multidimensional scaling) plot, unveiled significant inter-population differences in the measured traits among the studied populations. Furthermore, the combined use of the one way ANOSIM (analysis of similarities) and the Discriminant/Hotelling analysis allowed unravelling two morphologically differentiated groups assigned to both western and eastern Mediterranean basins. The SIMPER (similarity percentages) routine analysis showed that total dry weight, test diameter and spine length were major contributors to the morphometric separation between locations and between groups. Pattern of phenotypic divergence discerned in P. lividus across the Siculo-Tunisian Strait is interestingly in congruence with that inferred from the genetic investigation of the purple sea urchin populations from the same region based on the analysis of the mtDNA COI (cytochrome oxidase I) gene in 314 specimens from nineteen locations covering a wider geographic transect, streching westward to the Algerian coast and eastward to the Libyan littoral. The specific haplotypic composition characterizing each Mediterranean basin, as inferred from the minimum spanning network, confirmed the geographic partioning of genetic variation, as revealed by F-statistics and AMOVA (analysis of molecular variance) analyses, yielding significant genetic differentiation between eastern and western Mediterranean populations. The newly detected phylogeographic patterns, observed for the first time in P. lividus throughout the explored distribution range, suggest the involvement of different biotic and abiotic processes in shaping such variation, and provide evidence that a large and geographically exhaustive dataset is necessary to unveil phylogeographic structure within widespread marine species, previously cathegorized as panmictic in part of their distribution range.  相似文献   

14.
The effect of harvesting on the diversity and structure of benthic assemblages is nowadays a relevant component of fishery management. Invertebrate harvesting is increasing worldwide and sea urchins are one of the main invertebrate target species. However, current knowledge about the effects of sea urchin harvesting on benthic assemblages is still poor. The aim of this study is to evaluate the influence of Paracentrotus lividus (Lamark, 1816) harvesting on tide pool assemblages from intertidal rocky shores. To achieve this objective, a field removal experiment was done for 10 months. Results of univariate and multivariate analyses showed that P. lividus harvesting had a significant effect on the number of taxa and structure of the benthic assemblage. Assemblages from pools where P. lividus were removed showed significant differences against controls; namely, where P. lividus were eliminated, pools showed higher number of taxa than control pools. This result contrasts with previous studies assessing effects of invertebrate harvesting that generally have found a biodiversity reduction in the exploited habitat. Despite this apparently positive effect of P. lividus harvesting, we should be cautious because effects of P. lividus harvesting on higher trophic levels or during long periods of time remain unexplored.  相似文献   

15.
The sea urchin Paracentrotus lividus is common in the Mediterranean in shallow subtidal rocky habitats and in Posidonia oceanica beds. The aim of this study is to investigate whether protection has the same effect on the population structure of P. lividus occurring in rocky reef habitats and in P. oceanica beds. These results are important to generate hypotheses about the influence of human harvesting, predatory pressure and migration processes on P. lividus in the two habitats.  相似文献   

16.
Radiolabelled experiments were carried out to measure necessary parameters in the development of a biodynamic ecotoxicological simulation model of Cd accumulation in the barnacle biomonitor Balanus amphitrite. The Cd uptake rate constant from the dissolved phase, the Cd assimilation efficiency (AE) from suspended particulate matter (SPM) and the efflux rate constant were obtained using 109Cd. A Cd uptake rate constant from the dissolved phase (ku) of 0.0072 L g−1 h−1 was determined for the barnacle under environmentally realistic dissolved Cd concentrations (maximum of 400 ng L−1). Cd AE from SPM was determined from the barnacle feeding on SPM with low and high chl a concentrations, resulting in AEs of 39.0% and 48.7%, respectively, and an efflux rate of 0.0072 d−1. The difference between the AEs resulted from differences in chl a:SPM ratios suggesting a general tendency of higher AE when SPM is enriched with chl a. These results reinforce that the accuracy of ecotoxicological models for metal accumulation in organisms depends on how representative the selected food items are of the organism’s natural diet.  相似文献   

17.
The chemical forms of Cd, Pb and Cu in seawater have been examined using a novel scheme which permits the quantification of up to seven different species of one metal. The concentration of each species was calculated from measurements using anodic stripping voltammetry of labile and total metal in samples which were (a) untreated, (b) UV irradiated, (c) passed through a chelating resin column, and (d) UV irradiated then passed through a chelating resin column. In the sample studied, the major proportion of Cd, Pb and Cu was found to be associated with organic and inorganic colloidal species. Less than half of the bound Pb and Cu was readily exchangeable with added 210Pb and 64Cu.  相似文献   

18.
Sea urchins can alter the composition and dynamics of algal communities by grazing. Changes in their displacement capability can influence their grazing and thus their effect on algal communities. The daily and monthly movement of Paracentrotus lividus inside and outside a marine reserve in the NW Mediterranean Sea was studied in order to determine the role of predation in sea urchin movements and its potential grazing impacts. During the 3‐month study, the total distance travelled by sea urchins ranged from 71.8 to 673.6 cm (mean = 379.2 cm, SD = 221.3). Home ranges (distances from the initial position) were between 50 and 302 cm (mean = 150.7 cm, SD = 99.4). Movements were not directional but random, with a mean of 150 cm around the initial position. The activity of Paracentrotus lividus was significantly higher at night than during daylight. Total displacement at the end of the experiment was significantly higher in the unprotected area than in the reserve, as was the home range. The linear distance travelled in a 24‐h period ranged between 6 and 220 cm with a mean home range of 51 cm. These results agree with those of other authors, and allow us to rule out major migratory processes of sea urchin populations in this area. Nevertheless, these results underline the role of predatory fishes in reducing herbivory pressure by trophic cascades, reinforcing the evidence that sea urchin escape behaviour may be an important factor in structuring algal communities.  相似文献   

19.
Despite the large body of work published in the last two decades on the reproduction of the sea urchin Paracentrotus lividus, the reproductive aspects linked to hydrodynamic conditions and their influence on gonad production remain poorly understood. The present paper aims to evaluate the effect of hydrodynamism on the reproductive cycle of P. lividus. Variability in the gonadosomatic index (GSI) of P. lividus was estimated seasonally from 2007 to 2008 at two shallow sub-littoral flat basaltic areas at Ustica Island (Western Mediterranean). GSI was higher in the sites characterized by low hydrodynamism than in those with high hydrodynamism. Results also suggest a possible role for hydrodynamism in triggering processes of resource limitation (food shortage), probably by interfering with P. lividus feeding activity.  相似文献   

20.
We examined whether adults of three species of sea urchins species (Diadema antillarum, Arbacia lixula, and Paracentrotus lividus) exhibit a consistent depth-dependent partitioning pattern on rocky reefs of the Canarian Archipelago (eastern Atlantic). Hydrodynamic experiments were carried out to quantify the resistance to flow-induced dislodgement in these three species. We tested the model that different morphology can result in habitat partitioning among these sea urchins. Abundances of D. antillarum increased with depth. In contrast, A. lixula and P. lividus showed the opposite zonation pattern, coexisting in high abundances in the shallowest depths (<5 m), and occurring in low densities in the deepest part of reefs (>7 m). Both A. lixula and P. lividus had greater adhesion-surface to body-height ratios than D. antillarum. Similarly, A. lixula and P. lividus showed a greater ability to resist flow-induced dislodgement compared with D. antillarum. The mean “velocity of dislodgement” was 300% and 50% greater for A. lixula and P. lividus, respectively, relative to D. antillarum, for any particular size. As a result, A. lixula and P. lividus are better fitted to life in high-flow environments than D. antillarum. We conclude that the risk of dislodgement by water motion likely play a relevant role in the vertical distribution patterns of these sea urchins in the eastern Atlantic.  相似文献   

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