Life history of a dominant polychaete, <Emphasis Type="Italic">Polygordius jouinae</Emphasis>, in inner continental shelf sands of the Mid-Atlantic Bight,USA

The life history of the polychaete Polygordius jouinae Ramey, Fiege, and Leander 2006 was studied in the sandy sediments of the LEO-15 research area off the coast of Tuckerton, New Jersey (39°27.69′N, 74°15.81′W). Divers collected sediment cores biweekly, from February 2004 to November 2005 to examine the temporal patterns of abundance and size–frequency distributions of P. jouinae. These parameters were also examined (for the first time) for P. jouinae in samples taken in ambient sediments and in three reciprocal 3 to 5-day sediment transplant experiments that were part of a previous, unrelated study at coarse sand and muddy sand sites (∼3 km apart) at LEO-15 in the summers of 1994 and 1995. Analysis of these previous data along with the current data provided a larger set of values for P. jouinae, as well as further insight into the life history, habitat selection, and dispersal of P. jouinae (not considered in previous studies). Polygordius jouinae is gonochoristic and the population was mostly composed of sexually mature individuals in late May 2004 and 2005. The reproductive period usually occurs from May to August and individuals that spawn generally have a 1-year life span. Non-spawning individuals of P. jouinae could potentially live longer than 1 year and therefore the population may sometimes consist of individuals of two generations. Recruitment begins no later than July as recently settled individuals (≤9 mm body length), which were not present during the first week of June 1995, 2004, and 2005, first appeared in July in all 3 years. The smallest individual was 2.01 mm long and 0.07 mm wide and this provides the first estimate of size at initial recruitment. Although some worms in sediment trays likely settled as larvae, most worms were recently settled juveniles (length categories 6 and 9 mm) transported in from the surrounding sediments, presumably as a consequence of re-suspension or bed load transport. As expected, larger individuals were present later in September. Although it is unknown whether P. jouinae were transported actively or passively these data suggest that recently settled juveniles are capable of habitat selection (prefer sand over mud) and show that post-settlement transport and selection influence community structure.     

Ecological simulation model of Los Angeles Harbor

A quasi-steady state numerical ecosystem model was designed to help evaluate the potential impact of various scenarios of effluent treatment and of a landfill on the distribution of phytoplankton and inorganic nutrients in Los Angeles and Long Beach harbors Formulations included (a) tidal circulation, (b) phytoplankton growth and oxygen production as a function of temperature, light, and nutrients, (c) grazing by zooplankton, (d) respiration and nutrient regeneration by the benthos, (e) biochemical oxidation of organics, and (f) nitrification Phytoplankton nitrogen, ammonium, nitrate, and oxygen were the state variables, which were simulated with diel and spatial variability for a range of seasonal conditions. Physical circulation was indicated to be a primary factor governing the distribution of state variables, and the landfill resulted in significant alterations. Simulated phytoplankton stocks approximated the upper range of reported concentrations, indicating a satisfactory prediction of bloom conditions. The model indicated that while light may usually regulate maximum phytoplankton levels, under bloom conditions nutrient limitation may also be important Most of the outer Los Angeles Harbor was affected by the effluent, as shown by comparison to the case with zero input Simulations for secondary versus primary treatment converged a short distance from the outfall in response to high BOD oxidation rates. In general, total phytoplankton crop was not greatly affected by the change from primary to secondary treatment, and predation on phytoplankton was small     

A three-trophic level estuarine model: Synergism of two mechanistic simulations

Few numerical simulations have attempted to include a high degree of biological detail for several trophic levels. Typically, in planktonic ecosystem models, if the dynamics of nutrients, phytoplankton and herbivorous zooplankton are formulated with ecological complexity, then carnivores are ignored, forced or modeled in an extremely simplified manner. Extensive mechanistic detail for important carnivores is difficult to represent because reliable and relevant ecological data are rarely available for appropriate species and local populations. Further, the wide temporal and spatial differences between life histories of lower plankton and carnivores may be technically difficult to model.In Narragansett Bay, Rhode Island, the ctenophore Mnemiopsis leidyi is an important carnivore to which these objections do not apply. A detailed carbon-based simulation model of this population of ctenophores was developed independently from an ecosystem model of Narragansett Bay which included detailed interactions between phytoplankton, primarily herbivorous zooplankton and nutrients. The interfacing of these two models without changing any of the formulations or values of the coefficients provided a test of the commonly used practice of forcing certain components. Both models were originally constructed with the biomass of a critical compartment forced according to observed data; in the plankton model, ctenophores were forced, and in the ctenophore model, zooplankton were forced.Predicted biomasses for zooplankton and ctenophores in the combined model were similar to the results of the two parent models, but improved relative to the actual field observations. From the findings it appears that the strategy of forcing is valid provided the forced patterns are appropriate and reasonable.     

Using species spectra to evaluate plant community conservation value along a gradient of anthropogenic disturbance

The aim of this study was to assess the impact of anthropogenic disturbance on the partitioning of plant communities (species spectra) across a landcover gradient of community types, categorizing species on the basis of their biogeographic, ecological, and conservation status. We tested a multinomial model to generate species spectra and monitor changes in plant assemblages as anthropogenic disturbance rise, as well as the usefulness of this method to assess the conservation value of a given community. Herbaceous and arborescent communities were sampled in five Azorean islands. Margins were also sampled to account for edge effects. Different multinomial models were applied to a data set of 348 plant species accounting for differences in parameter estimates among communities and/or islands. Different levels of anthropogenic disturbance produced measurable changes on species spectra. Introduced species proliferated and indigenous species declined, as anthropogenic disturbance and management intensity increased. Species assemblages of relevance other than economic (i.e., native, endemic, threatened species) were enclosed not only in natural habitats, but also in human managed arborescent habitats, which can positively contribute for the preservation of indigenous species outside remnants of natural areas, depending on management strategies. A significant presence of invasive species in margin transects of most community types will contribute to an increase in edge effect that might facilitate invasion. The multinomial model developed in this study was found to be a novel and expedient tool to characterize the species spectra at a given community and its use could be extrapolated for other assemblages or organisms, in order to evaluate and forecast the conservation value of a site.     

Occurrence of triclosan in plasma of wild Atlantic bottlenose dolphins (Tursiops truncatus) and in their environment

The presence of triclosan, a widely-used antibacterial chemical, is currently unknown in higher trophic-level species such as marine mammals. Blood plasma collected from wild bottlenose dolphins (Tursiops truncatus) in Charleston, SC (CHS) (n = 13) and Indian River Lagoon, FL (IRL) (n = 13) in 2005 was analyzed for triclosan. Plasma concentrations in CHS dolphins ranged from 0.12 to 0.27 ng/g wet weight (mean 0.18 ng/g), with 31% of the sampled individuals having detectable triclosan. The mean IRL dolphin plasma concentrations were 0.072 ng/g wet weight (range 0.025–0.11 ng/g); 23% of the samples having detectable triclosan. In the CHS area, triclosan effluent values from two WWTP were both 190 ng/L and primary influents were 2800 ng/L and 3400 ng/L. Triclosan values in CHS estuarine surface water samples averaged 7.5 ng/L (n = 18) ranging from 4.9 to 14 ng/L. This is the first study to report bioaccumulation of anthropogenic triclosan in a marine mammal highlighting the need for further monitoring and assessment.     

How do weaponless male fiddler crabs avoid aggression?

Mimicry of females enables weaker males in many species to avoid intrasexual aggression. In fiddler crabs (Uca annulipes), males use their major claw in aggressive interactions to acquire and defend a territory. Males that have autotomised their major claw will be disadvantaged in fighting, but might use their temporary resemblance to females to avoid costly aggressive encounters with other males. We investigated whether: (1) courting males mistake clawless male fiddler crabs for females; (2) clawless males are able to acquire, defend and retain territories as successfully as intact males; and (3) clawless males are more cautious than intact males. Clawless and intact males differed in burrow acquisition methods and fighting behaviour, but were equally successful at acquiring and retaining burrows. While courting males treated clawless males as female, we found no evidence that clawless males mimic the behaviour of females, or that they exploit the advantage of their mistaken identity. Clawless males further appear to avoid male aggression by altering their territorial strategies to minimise the potential for conflict.