Capitella Sp Research Articles

Influence of lowered salinity and elevated cadmium on the survival and metamorphosis of trochophores in Capitella sp. I

Abstract. It is well known that the competent larvae of many marine invertebrate species can be stimulated to metamorphose by exposing them to elevated concentrations of certain ions, neuroactive substances, and pharmacological agents. In this study we report that larvae of the euryhaline polychaete Capitella sp. I are induced to metamorphose within 24–48 h by reducing salinity from 30%‰ to 12–15%‰. At 10%‰, however, fewer larvae metamorphosed and the normal metamorphic response to sediment was inhibited; competence was restored within 3 h of transferring the larvae back to full strength seawater (30%‰). Larvae also metamorphosed within 24 h in response to increased external cadmium concentrations of 1000–2000 μg 1–1. Further understanding of how reduced salinity and elevated cadmium stimulate (or inhibit) metamorphosis may lead to a better understanding of signal perception and transduction in this and other species.

Metabolism of the polycyclic aromatic hydrocarbon fluoranthene by the polychaete Capitella capitata species I

Previous studies have shown that infaunal deposit feeders may enhance the loss of organic contaminants from sediments. However, the extent to which this occurs as a result of sediment microbial stimulation, porewater flushing, or biotransformation by infauna remains unclear. The purpose of this study was to determine whether the infaunal polychaete Capitella sp. I is able to metabolize the polycyclic aromatic hydrocarbon (PAH) fluoranthene and to provide an initial characterization of the metabolites produced. Our results showed that Capitella sp. I is able to metabolize fluoranthene to more hydrophilic products and that, after 24 h in clean sediment, fluoranthene could no longer be detected in worm tissues whereas a number of fluoranthene-derived metabolites were present. None of the metabolites released or retained by worms resembled known bacterial metabolites, suggesting that Capitella, and not bacteria associated with its gut or body surface, were responsible for the biotransformation of fluoranthene in our system. On the basis of ultraviolet maxima, peak shape, relative height, and order of elution, tentative identities of two metabolites (i.e., 3- and 8-hydroxyfluoranthene) are proposed. The results demonstrate that, in addition to their effects on sediment geochemical properties, infaunal polychaetes such as Capitella can enhance the degradation of sediment-associated contaminants by directly metabolizing them.

Effects of benthic fauna on organic matter mineralization in fish-farm sediments: importance of size and abundance

The effects of the polychaetes Nereis diversicolor and Capitella sp. I on organic matter mineralization in marine sediments collected under a fish farm were studied in vitro. The two species differ significantly in size, feeding, and burrowing activity. The presence of benthic fauna stimulated the total benthic metabolism (measured as O2 uptake, CO2 release, and SO 2 reduction) substantially compared to the microbial metabolism in an azoic sediment. Nereis and Capitella stimulated mineralization over a two-month period by 135% and 87%, respectively. The stimulation was primarily microbial (54%) in Capitella sediments. Sulphate reduction remained similar to azoic sediments, indicating that in particular the aerobic activity was enhanced. Microbial stimulation was less (23%) for Nereis sediments, while sulphate reduction was reduced (42%), indicating enhanced oxidation compared to azoic sediments. The faunamediated oxidation of the sediment probably causes increased removal of nitrogen through increased nitrification and denitrification and enhanced binding of phosphorus, thereby reducing nutrient fluxes to the water column. 2001 International Council for the Exploration of the Sea

Sediment processing in Capitella spp. (Polychaeta: Capitellidae): strain-specific differences and effects of the organic toxicant fluoranthene

The effects of the widespread polycyclic aromatic hydrocarbon (PAH) fluoranthene on sediment-processing rates in the infaunal polychaete Capitella spp. were investigated by comparing five populations of this deposit-feeding species complex: Capitella sp. I from New York, USA; Capitella sp. M from Milos, Greece; Capitella sp. S from Sylt, Germany; and two unidentified Capitella populations from salmon farm sediments –Capitella population K from Kilmelford, Scotland and Capitella population C from Cranford, Ireland. Replicate worms from each strain were exposed to 0, 10, and 95 μg (g dry wt sediment)−1 fluoranthene (=μg/g fluoranthene) for a period of 16 days. Initial and final wet and dry weights (mg) of worms and worm-specific growth rates (WSGRs) were calculated. Sediment processing was measured as the sum of the total dry weight of pellets produced during the experiment, and we estimated size-specific processing rates (SSPRs) as a measure of sediment processed per mg worm dry weight per day. The five populations of Capitella spp. differed significantly in body size, WSGR, and sediment-processing rates. Capitella sp. I grew faster than all of the other populations. Capitella population C and Capitella population K from fish farm sediments, with the largest body lengths (up to 52.0 ± 27.2 mm), had the highest processing rates, whereas the small Capitella sp. S (up to 17.1 ± 5.6 mm) had the lowest. There were also significant differences in SSPR among populations with Capitella sp. I having a higher SSPR (about 12 × body wt/day) than Capitella population C (about 5 × body wt/day) and Capitella population K (3 × body wt/day). The fluoranthene concentrations used in the present study, while representing moderately to highly contaminated conditions, had only marginal effects on sediment-processing and growth rates of all of the Capitella populations examined. Processing of contaminated sediment by Capitella spp. may be important in the remediation of PAH-contaminated sediment.

Exploitation of a chemosynthetic food resource by the polychaete Capitella sp.

In organically enriched sediments of coastal areas, sulfate-reducing bacteria decom- pose organic matter anaerobically, producing high levels of hydrogen sulfide. Chemoautotrophic sul- fur-oxidizing bacteria proliferate at the sulfide/oxygen interface and use hydrogen sulfide as an elec- tron donor. A few species of small polychaete worms, including Capitella sp. I, often dominate the macrofaunal benthic communities in such sulfide-rich environments in the organically enriched sed- iments. In this study, we conducted 2 laboratory experiments to determine whether Capitella sp. I can benefit trophically through the exploitation of the organic matter chemosynthetically produced by sulfur-oxidizing bacteria. In the first experiment, we reared juveniles of Capitella sp. I with natural sediment of very low organic content, with no additional organic matter, under dark conditions, and exposed them to 3 different levels of sodium sulfide. The worms reared in the sulfide treatments showed better survival, enhanced growth and reproduction. They had lower δ 13 C values (-24.3‰, mean) than control worms (-20.1‰, mean) and the sediments in which the worms were cultured (-21.4‰, mean). The distinctive δ 13 C signature of the worms in the sulfide treatments indicates that they did not share the same carbon source as the control worms. The second experiment was done in the same manner as the first, but the carbonate in the water was replaced with 13 CO2 in order to trace the autotrophic fixation of carbon dioxide by chemosynthetic bacteria occurring within the sedi- ments. The results indicate that fixation of 13 CO2 was promoted in sediments with Na2S amendments, and further enhanced by the presence of Capitella sp. I. The worms in these sediments had extremely high δ 13 C values (+5218.2‰). The results of this study introduce the possibility of enhanced survival and growth of Capitella sp. I in sulfide-rich environments in the organically enriched sediments, facilitated by its utilization of a novel source of organic matter.

LOSS RATES OF POLYCYCLIC AROMATIC HYDROCARBONS FROM SEDIMENT AND DEPOSIT-FEEDER FECAL PELLETS

Deposit feeders modify sediment by aggregating individual particles into fecal pellets. Loss of contaminants may be either more (enhanced bacterial degradation) or less (hindered diffusion and desorption) rapid for sediment incorporated into pellets. We studied the loss of 10 polycyclic aromatic hydrocarbons (PAHs) from historically contaminated estuarine sediment and the same sediment after it had been pelletized by Capitella sp. I, a polychaete worm typically found in disturbed environments. Fecal pellets initially had higher concentrations of organic carbon and PAHs (enrichment factors 1.03–1.21) due to selective feeding. Over 60 d, desorption of PAHs was minimal, with an average loss of 4 to 5%. Biodegradation accounted for an additional 28% loss. A two-component model fit the data well and indicated that the slowly desorbing fraction was close to one for all PAHs. For low molecular weight PAHs, biodegradation rate constants were greater than desorption rate constants; for high molecular weight PAHs, the opposite was found. Desorption rate constants were similar for fecal pellets (0.0002–0.037/d) and sediment (0.0002–0.031/d). Biodegradation rate constants were also similar for fecal pellets (0.0006–0.022/d) and sediment (0.0002–0.018/d). Thus, incorporation of sediment into robust fecal pellets (half-life on the order of decades) did not affect the loss rates of PAHs.

Variability in reproductive mode and larval development within the Capitella capitata species complex

Summary A comparative analysis was carried out of reproductive mode, larval development pattern, and larval growth rate under identical conditions of three members of the Capitella capitata species complex: Capitella sp I from New York, US, Capitella sp M from shallow hydrothermal vents off Milos, Greece, and Capitella sp S from an intertidal flat on Sylt, Germany. In addition, three populations from salmon farms, Capitella K (Kilmelford, Scotland), Capitella Cm and Capitella Ct (Cranford, Ireland), are described for the first time. Three development patterns were observed: planktotrophic (Capitella K and Ct populations), lecithotrophic (Capitella spp I, M and Cm populations), and direct development (Capitella sp S). Experiments with planktotrophic larvae from the Capitella K population at different temperatures, in the presence and absence of light and with several kinds of substrate were not successful in inducing settlement, although differences in the duration of larval survival were observed. Overall, major differences in reproductive modes and larval development patterns were observed among representatives of different species and populations reared under identical culture conditions. In contrast, such modes and patterns are consistent across generations. Whereas larval type and developmental mode appear to be determined largely by genetic factors, environmental conditions have an important influence on the timing of key developmental processes, such as settling and growth.

Effects of reduced salinity on survival, growth, reproductive success, and energetics of the euryhaline polychaete Capitella sp. I.

Physiological adjustment to water of reduced salinity requires energy expenditure. In this study we sought to determine the fitness costs associated with such adjustment in the euryhaline polychaete Capitella sp. I, and the extent to which such costs could be explained by increased rates of energy expenditure. In a series of experiments conducted at 20 degrees C, salinity was reduced from 30 per thousand to either 25, 20, 15, 12, or 10 per thousand within 72 h after the larvae had been induced to metamorphose. Juveniles were reared on fine, organic-rich sediment. Over the next 15-30 days, we determined survival, growth, fecundity, and rates of respiration and feeding (via fecal pellet production). Larval salinity tolerance was also determined. Juvenile survival at salinities as low as 12-15 per thousand was comparable to that at 30 per thousand. The lower limit of salinity tolerance was 10-12 per thousand at 20 degrees C for both larvae and juveniles. Juveniles grew significantly more slowly at 12-15 per thousand in six of the seven experiments. Fecundity, however, was generally highest at intermediate salinities of 20-25 per thousand, and comparable at 30 and 15 per thousand. No individuals released embryos at 12 per thousand over the approximately 30-day observation periods in any of the three experiments in which the worms were reared at this low salinity. Reduced growth rates were not explained by differences in rates of respiration at different salinities: at reduced salinity, respiration rates were either statistically equivalent to (P>0.10) or significantly below (P<0.05) those recorded for animals maintained at 30 per thousand. Lower growth rates at lower salinities were best explained by reduced feeding rates. Further studies are required to determine whether digestive efficiency, growth hormone concentrations, or reproductive hormone concentrations are also altered by low salinity in this species.

Halogenated metabolites in two marine polychaetes and their planktotrophic and lecithotrophic larvae

This study investigated the occurrence and ontogenetic changes of halogenated secondary metabolites in planktotrophic and lecithotrophic larvae and adults of two common, infaunal polychaetes, Streblospio benedicti (Spionidae) and Capitella sp. I (Capitellidae), with different life-history traits. S. benedicti contains at least 11 chlorinated and brominated hydrocarbons (alkyl halides) while Capitella sp. I contains 3 brominated aromatic compounds. These halogenated metabolites are potential defense compounds benefiting both larvae and adults. We hypothesized that: (1) planktotrophic larvae contain halogenated metabolites because they are not protected by adult defenses, (2) quantitative and qualitative variation of planktotrophic larval halogenated metabolites parallels that of adults, and (3) brooded lecithotrophic larvae initiate the production of halogenated metabolites only after metamorphosis. To address these hypotheses, volatile halogenated compounds from polychaete extracts were separated using capillary gas chromatography and identified and quantified using mass spectrometry with selected ion monitoring. All four life stages (pre- and post-release larvae, new recruits, adults) of both S. benedicti and Capitella sp. I contained the halogenated metabolites previously identified from adults. This is the first report of halocompounds identified and quantified in polychaete larvae. Allocation of potential defense compounds to offspring varied as a function of species, feeding type and developmental stage. Pre-release larvae of S. benedicti with planktotrophic development contained the lowest concentration of total halogenated metabolites (1.75 ± 0.65 ng mm−3), post-release and new recruits contained intermediate concentrations (8.29 ± 1.72 and 4.73 ± 2.63 ng mm−3, respectively), and planktotrophic adults contained significantly greater amounts (28.9 ± 9.7 ng mm−3). This pattern of increasing concentrations with increasing stage of development suggests synthesis of metabolites during development. Lecithotrophic S. benedicti post-release larvae contained the greatest concentrations of halometabolites (71.1 ± 10.6 ng mm−3) of all S. benedicti life stages and developmental types examined, while the amount was significantly lower in new recruits (34.0 ± 15.4 ng mm−3). This pattern is consistent with a previously proposed hypothesis suggesting a strategy of reducing potential autotoxicity during developmental transitions. Pre-release lecithotrophic larvae of Capitella sp. I contained the highest concentration of total halogenated metabolites (1150 ± 681 ng mm−3), whereas the adults contained significantly lower total amounts (126 ± 68 ng mm−3). All concentrations of these haloaromatics are above those known to deter predation in previously conducted laboratory and field trials. As a means of conferring higher larval survivorship, lecithotrophic females of both species examined may be expending more energy on chemical defenses than their planktotrophic counterparts by supplying their lecithotrophic embryos with more of these compounds, their precursors, or with energy for their synthesis. This strategy appears common among marine lecithotrophic larval forms.

Confidence intervals for population growth rate of organisms with two‐stage life histories

Although life histories can be modelled with great generality using projection matrices, for organisms with life histories that can be accurately described by a simplified set of parameters, e.g. when adult fecundity and mortality are independent of age, more accurate estimates of life table parameters and of population growth rate and its standard error can be readily obtained. Here an analytic method for calculating approximate confidence intervals for population growth rate is given for two‐stage life histories that can be described by four variables representing age at first breeding, fecundity per unit time, and juvenile and adult survivorships per unit time. The method is applied to experimental data on Capitella sp. I obtained by Hansen et al., and quite good agreement is found between the analytic and bootstrap estimates of the standard error of Λ. The analytic estimates were a little conservative, probably because of the way the action of mortality was modelled. Alternative life‐history models are briefly discussed, and the desirability of formulating life‐history models so that the variables involved are independent of each other is stressed. Analytic estimates of Λ may be biassed if an inappropriate model is chosen or if variables are not independent and the correlations between them are not measured. To allow for these possibilities, where necessary a conservative approach should be taken to significance testing using the analytic method.

Effects of fluoranthene and ambient oxygen levels on survival and metabolism in three sibling species of Capitella (Polychaeta)

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 194:169-177 (2000) - doi:10.3354/meps194169 Effects of fluoranthene and ambient oxygen levels on survival and metabolism in three sibling species of Capitella (Polychaeta) Inez Linke-Gamenick1,*, Bent Vismann2, Valery E. Forbes1 1Department of Life Sciences and Chemistry, Roskilde University, Postbox 260, 4000 Roskilde, Denmark 2Marine Biological Laboratory, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark *E-mail: ipklinke@aol.com ABSTRACT: The successful persistence of Capitella spp. in disturbed and/or oil-polluted habitats is widely known, but demographic adaptations might be only part of the explanation and little is known about differences among species. The present study investigates ecophysiological effects of the common PAH (polycyclic aromatic hydrocarbon) fluoranthene (FLU) on juvenile and adult survival, comparing 3 sibling species of Capitella (Polychaeta; Capitellidae). Subsequently, the influence of FLU on the aerobic and anaerobic metabolism in the most Œsensitive¹ species, Capitella sp. S, and most Œtolerant¹ species, Capitella sp. I, was assessed. Oxygen uptake and internal succinate concentration (an indicator of anaerobic metabolism) were measured after short-term (7 h) and long-term (2 wk) FLU pre-exposure (100 µg g-1). FLU exposure reduced mean survival times of juveniles (4 d old) of all sibling species, but tolerance varied among the 3 species of Capitella adults. Capitella sp. S, originally collected from Œclean¹ oxygen-rich North Sea intertidal sediments, was most sensitive and Capitella sp. M, and Capitella sp. I, which is the most opportunistic of the sibling species described to date, were most tolerant. In Capitella sp. S, O2 uptake decreased at lower ambient oxygen levels and increasing FLU concentrations increased oxygen consumption. Similarly, O2 uptake decreased at lower ambient oxygen levels in Capitella sp. I; however, FLU concentrations had no effect on oxygen uptake. For both species, anaerobic metabolism increased with declining ambient oxygen levels, and was influenced by FLU exposure in Capitella sp. S, but not in Capitella sp. I. Part of the explanation for the success of Capitella sp. I in oil-polluted habitats may be that this species is able to channel energy into vital processes without a measurable increase in energy expenditure. We conclude that these 3 Capitella species are ecophysiologically diverse in their responses to toxicant exposure. Our results suggest that toxicant tolerance differences among sibling species have a genetic basis and that increased aerobic and anaerobic metabolic rates in response to toxicant exposure can have negative survival consequences. This has to be considered when using these species as pollution indicators or to improve sediment quality. KEY WORDS: Polychaete · Sibling species · Fluoranthene · Tolerance · Oxygen consumption · Succinate Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 194. Publication date: March 17, 2000 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 2000 Inter-Research.

Effects of chronic fluoranthene exposure on sibling species of Capitella with different development modes

Toxic effects of the polycyclic aromatic hydrocarbon fluoranthene (FLU) on life-history traits and their demographic consequences were investigated in 3 non-interbreeding Capitella sib- ling species with different physiological tolerances and developmental modes: sensitive Capitella sp. S from oxygen-rich intertidal sediments of the North Sea (Germany); tolerant Capitella sp. M from sediments near shallow hydrothermal vents off Milos (Greece), a habitat low in organic matter with steep abiotic gradients and high sulfide concentrations; tolerant Capitella sp. I from New York (USA), known to dominate eutrophicated/polluted environments. Both Capitella spp. M and I can develop into hermaphrodites and have lecithotrophic larval development. In contrast, Capitella sp. S appears to be dioecious and has direct development with benthic juveniles. In life-table-response experi- ments (LTRE), juveniles from the 3 species were raised under different FLU concentrations (0 to 95 µg g -1 FLU), and data on age-specific survival, growth and life-history parameters were recorded at weekly intervals. Under control conditions, the 3 Capitella species differed markedly in a number of life-history traits and population growth rates (λ), with Capitella sp. S showing the lowest λ (1.05), and Capitella sp. M the highest (1.42). Chronic exposure to inreasing FLU concentrations also revealed species-specific differences in individual- and population-level toxic responses. Highest FLU con- centrations (95 µg g -1 ) markedly reduced juvenile survival and completely inhibited reproduction in Capitella sp. S, whereas individual life-history traits in Capitella spp. M and I were affected little, if at all. At the population level, the highest FLU exposures resulted in λ values of effectively zero in Capitella sp. S, whereas λ of Capitella spp. M and I remained >1. In conclusion, the combination of opportunistic life-history features, reproductive flexibility, and physiological adaptations enables Capitella spp. M and I to colonize habitats rapidly after local disturbance and to persist in stressed and unpredictable environments; whereas in Capitella sp. S, population extinction under toxicant stress mainly results from its physiological sensitivity.

Feeding, growth, and fecundity of Capitella sp. I in relation to sediment organic concentration

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 205:229-240 (2000) - doi:10.3354/meps205229 Feeding, growth, and fecundity of Capitella sp. I in relation to sediment organic concentration Debra L. Linton*, Gary L. Taghon Institute of Marine and Coastal Sciences, Rutgers, the State University of New Jersey, 71 Dudley Road, New Brunswick, New Jersey 08901-8521, USA *E-mail: elinton@rci.rutgers.edu ABSTRACT: In marine soft-bottom benthic habitats, the disappearance of opportunistic species as succession proceeds following an enrichment or disturbance event is thought to be due to the exhaustion of a food resource. To further investigate this hypothesis, feeding rate, growth rate, and reproductive output (measured as embryo number and size) of the opportunistic deposit-feeding polychaete Capitella sp. I were measured in sediments with different protein concentrations but the same protein source. Feeding rates progressively increased as protein concentration increased over the range of 0.2 to 4.7 mg g-1; thereafter, feeding rate was constant up to a sediment protein concentration of 8.1 mg g-1, the highest used in these experiments. This response is not consistent with the predictions of optimal foraging theory, as applied to deposit feeders. Growth rate showed a similar pattern, progressively increasing then reaching a plateau at ~23% d-1 in sediments with 4.6 to 4.7 mg protein g-1. Capitella sp. I showed decreased fecundity and longer generation times (embryo sizes were not significantly different) in sediments with lower protein concentrations and did not reproduce in sediments containing <1 to 2 mg g-1. These results support the hypothesis that the disappearance of Capitella sp. I as succession proceeds is due to decreased fitness in sediments with lower food concentrations and an inability to reproduce in sediments below a threshold protein concentration. Systematically documenting how variations in sediment protein concentration affect the acquisition (feeding rate) and utilization (growth rate, reproductive output) of food resources by benthic invertebrates with different life-history strategies will help to elucidate important factors influencing the distribution of individuals and species in the benthos. KEY WORDS: Capitella sp. I · Deposit-feeding · Feeding rate · Functional response · Growth rate · Opportunistic species · Polychaetes · Sediment organic concentration Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 205. Online publication date: October 19, 2000 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2000 Inter-Research.

Effects of contaminated sediments on particle size selection by the polychaete Capitella sp. I

Capitellid polychaetes are generally considered opportunistic species, characteristic of or- ganically enriched and disturbed habitats. The feeding behavior of capitellids dramatically affects physical properties of sediments by repackaging sediment particles into large fecal pellets that persist for years. Particle size selection by Capitella sp. I was quantified using two approaches. Organic-rich sediments from four locations subjected to varying degrees of anthropogenic disturbance were used in the first approach. Sediment contamination, measured as the con- centrations of selected polycyclic aromatic hydrocarbons (PAHs) varied from 0.08 to 31 ppm. The median size of mineral particle ingested was 4 mm for all sediments. Worms selectively ingested the smallest particles in the most contaminated sediment. Because of potential ambiguity in obtaining accurate measurements of in situ particle sizes of natural sediments, a second experiment used glass beads as tracers added to natural sediment. Treatments consisted of phenanthrene added at six concentrations, from 0.07 to 13 ppm. Worms preferentially fed on small beads (most preferred particle size 1764 mm) in all treatments, and selection was unaffected by phenanthrene concentrations. Selective feeding on the finest sediment particles and their incorporation into long-lived fecal pellets may affect the persistence of organic contaminants in sediments. © 1999 Elsevier Science B.V. All rights reserved.

Relationship between sediment organic content, metamorphosis, and postlarval performance in the deposit-feeding polychaete Capitella sp. I

Chemical cues induce metamorphosis for the larvae of many benthic marine invertebrate species. These cues help to place organisms into habitats that will allow for rapid growth and increased reproductive success. This study was designed to examine the correspondence between induction of metamorphosis and post-metamorphic success in the deposit feeding polychaete Capitella sp. I. Larvae were offered substrates with organic content reduced by 50, 75, 90 or 95% to examine inductive ability. Post-metamorphic success was assessed as juvenile growth rate, time to first brood production, and fecundity. Larvae did not consistently choose the substrate with the highest organic content, and often metamorphosed sooner in response to substrates with insufficient organic material for optimal growth and reproductive success. These findings suggest that, while the cue for metamorphosis is probably organic and bound to fine particulates, the larvae of Capitella sp. I cannot assess the concentration of organic material necessary to support subsequent growth and development.

Effects of chronic metal exposure and sediment organic matter on digestive absorption efficiency of cadmium by the deposit‐feeding polychaete Capitella species I

AbstractOrganic matter such as humic acid and bacterial slime exopolymer are common in estuarine and coastal sediments, where they are ingested by animals that process particulate detritus. Both humic acid (HA; refractory) and exopolymer (EPS; easily digestible) bind metals and therefore might represent a source of particulate‐bound metals to deposit‐feeding organisms. This study examined how cadmium preexposure (3 and 30 μg Cd/g dry wt. sed.), gut passage time (GPT), and quality and quantity of the organic coating on sediment particles interact to determine cadmium absorption efficiency (Cd‐AE) in Capitella sp. I. Pulse‐chase experiments using 109Cd and 51Cr were used to determine Cd‐AE in individual worms. Worms were given a pulse of carbon‐cleaned, HA‐coated or EPS‐coated sediment particles. The third treatment was divided into three EPS concentrations (high, medium, and low). A 5‐d preexposure to cadmium did not affect the egestion rates during either the preexposure period or the chase phase. Worms given a pulse of carbon‐cleaned particles exhibited higher egestion rates during the chase phase than worms given a pulse of organic‐coated particles, and no differences were seen in egestion rate between worms exposed to HA‐ and high‐EPS‐coated particles. Egestion rates decreased with increasing EPS concentration. The presence of refractory organic material decreased the absorption efficiency of cadmium from sediment relative to Cd‐AE from carbon‐cleaned sediment but not relative to Cd‐AE from sediment coated with a high concentration of EPS. The Cd‐AE increased linearly with increasing exopolymer coating on sediment particles. Overall, Cd‐AE increased with increasing gut passage time in worms that were not preexposed, although Cd‐AE from HA‐coated particles was independent of gut passage time. Preexposure to cadmium reversed the relationship between gut passage time and cadmium absorption efficiency. Thus, the implications are that sedimentary organic matter and worm physiology might be especially important in controlling metal bioavailability in deposit‐feeding organisms and should be considered in sediment quality approaches.

EFFECTS OF 4-n-NONYLPHENOL ON LIFE-HISTORY TRAITS AND POPULATION DYNAMICS OF A POLYCHAETE

A Life-Table-Response Experiment lasting 78 d was performed to investigate the toxic effects of sediment-associated 4-n-nonylphenol (NP) on growth, reproduction, and survivorship of isolated hermaphrodites of the infaunal polychaete Capitella sp. I. Demographic effects were evaluated using both a fully age-classified and a simple two-stage model to estimate population growth rates (λ). Decomposition analysis was performed to explore the contributions of each of the affected life-history traits to the effects observed on λ. Elasticity analysis was applied to examine the relative sensitivity of λ to changes in each of the different life-history traits under different exposure levels. In the lowest NP treatment (14 μg NP/g dry mass of sediment) significant stimulatory effects were observed for both asymptotic body volume and average brood size, but these did not result in a significant effect on λ. Negative effects on brood size, volume-specific fecundity, time to first reproduction, and individual growth ra...

Using elasticity analysis of demographic models to link toxicant effects on individuals to the population level: an example

1. A simple two‐stage population model was applied to data from a previously published life‐table response experiment (LTRE), which examined the toxicity of 4‐n‐nonylphenol to life‐history traits of the polychaete Capitella sp. I. Population growth rates (λ) and the relative sensitivities (= elasticities) of λ to changes in each of the individual life‐history traits were calculated. 2. In the present study, the life‐history parameters measured in laboratory‐reared individuals were manipulated to simulate potential effects of competition and predation on fecundity, time to reproductive maturity and juvenile survival to explore how such factors might influence the sensitivity of population growth rate to toxicant‐caused changes in individual life‐history traits. 3. Dramatic changes in elasticity patterns among simulations indicate that population growth rates may respond very differently to toxicant exposure depending on the extent to which other demographically limiting factors (e.g. competitors and/or predators) are operating on the population. 4. Effectively predicting the population‐level consequences arising from toxicant effects measured on individuals can be improved by exploring the elasticity pattern of λ for the population over a range of realistic ecological situations.

EFFECTS OF CHRONIC METAL EXPOSURE AND SEDIMENT ORGANIC MATTER ON DIGESTIVE ABSORPTION EFFICIENCY OF CADMIUM BY THE DEPOSIT-FEEDING POLYCHAETE CAPITELLA SPECIES I

Organic matter such as humic acid and bacterial slime exopolymer are common in estuarine and coastal sediments, where they are ingested by animals that process particulate detritus. Both humic acid (HA; refractory) and exopolymer (EPS; easily digestible) bind metals and therefore might represent a source of particulate-bound metals to deposit-feeding organisms. This study examined how cadmium preexposure (3 and 30 μg Cd/g dry wt. sed.), gut passage time (GPT), and quality and quantity of the organic coating on sediment particles interact to determine cadmium absorption efficiency (Cd-AE) in Capitella sp. I. Pulse-chase experiments using 109Cd and 51Cr were used to determine Cd-AE in individual worms. Worms were given a pulse of carbon-cleaned, HA-coated or EPS-coated sediment particles. The third treatment was divided into three EPS concentrations (high, medium, and low). A 5-d preexposure to cadmium did not affect the egestion rates during either the preexposure period or the chase phase. Worms given a pulse of carbon-cleaned particles exhibited higher egestion rates during the chase phase than worms given a pulse of organic-coated particles, and no differences were seen in egestion rate between worms exposed to HA- and high-EPS-coated particles. Egestion rates decreased with increasing EPS concentration. The presence of refractory organic material decreased the absorption efficiency of cadmium from sediment relative to Cd-AE from carbon-cleaned sediment but not relative to Cd-AE from sediment coated with a high concentration of EPS. The Cd-AE increased linearly with increasing exopolymer coating on sediment particles. Overall, Cd-AE increased with increasing gut passage time in worms that were not preexposed, although Cd-AE from HA-coated particles was independent of gut passage time. Preexposure to cadmium reversed the relationship between gut passage time and cadmium absorption efficiency. Thus, the implications are that sedimentary organic matter and worm physiology might be especially important in controlling metal bioavailability in deposit-feeding organisms and should be considered in sediment quality approaches.

Importance of bioturbation and feeding by the polychaete Capitella sp. I in the degradation of di(2-ethylhexyl)phthalate (DEHP)

A microcosm study of the effect of Capitella sp. I (Polychaeta) population density on the mineralization of a pulse addition of the plasticizer DEHP (di[2-ethylhexyl]]phthalate) demonstrated a 2-fold increase in mineralization (cumulative 14 CO 2 production) when worms were present. An additional experiment investigated the fate of ingested particle-bound 14 C-DEHP and measured the loss of ingested 14 C-DEHP into 14 CO 2 , DO 14 C and PO 14 C pools. Less than 1% of 14 C consumed during a 1 h ingestion period was ultimately respired as 14 CO 2 , while 10% was excreted as DO 14 C and 89% as PO 14 C, Approximately 1% of ingested 14 C was retained in worm tissue 20 h after ingestion. Assuming density-independent feeding rates, worm respiration could account for 4.5% to 19.1% of the total microcosm 14 CO 2 production, suggesting that microbial respiration to 14 CO 2 was the dominant process. Pre-exposure of worms to DEHP (10 μg g -1 sediment dry wt) for 1 wk had no effect on the fate of ingested DEHP and distribution into the respective pools. Worms exerted a strong effect on ultimate DEHP degradation ( 14 CO 2 production) but the effect was manifest at the lowest worm density and did not increase with increasing population size. The lack of an increased effect at greater population densities may be due to population density-dependent factors acting to decrease such important parameters as individual worm ventilation and feeding rates. A density-dependent decrease in feeding rate is supported by the observation that measured 14 C body burdens were highest at lowest worm densities.