Comparative feeding ecology of two sympatric rockfish congeners,Sebastes caurinus (copper rockfish) and S. maliger (quillback rockfish)

Possible differences in the diet or metabolism of sympatric finback and humpback whales in the Gulf of St. Lawrence were investigated through analysis of their blubber fatty acids. Free-ranging finback (Balaenoptera physalus, n=19) and humpback (Megaptera novaeangliae, n=10) whales were sampled through biopsy during summer 1991. The two species differed in the chemical composition and stable carbon isotope distribution of fatty acids extracted from their outermost blubber layer. Finback blubber was slightly but significantly richer in its relative proportions of 12:0, 13:0, i14:0, 17:0, 18:1 n9, 18:1 n7, and 20:0 (probability of difference 99%), 18:2 n6, 18:0, and 19:0 (probability 95%), and 16:1 n5 and 16:0 (90%). The stable isotope ratio of finback total fatty acids averaged-25.5±0.4%. Humpbacks contained relatively more i16:0, 18:1 n5, 20:5 n3, and 22:6 n3 (probability 99%), 16:1 n7, i18:0, 20:4 n6, and 22:5 n3 (95%), and 20:4 n3 (>90%). Their fatty acid ¹³ averaged -25.8±0.5% (different from finbacks with a probability of 95%). There was no significant difference between the two species in the relative proportions of 14:1, 14:0, i15:0, a15:0, 15:0, i17:0, a17:0, 17:1, 20:1 n9, 20:1 n7, 22:1 n11, or 22:1 n9, which together made up one-third of total fatty acids. We used principal component and cluster analyses to integrate and visualize the differences in the chemometric data sets. The chemical and isotopic differences found in the present study are consistent with a slightly lower trophic position for humpbacks compared to finbacks in the Gulf of St. Lawrence, reflecting a difference in long-term, average diet.     

Phosphate acquisition in the giant clam-zooxanthellae symbiosis

The effect of phosphate on the giant clam Tridacna gigas and on its symbiotic dinoflagellate Symbiodinium sp. was compared with that on cultured Symbiodinium sp. originally isolated from the same clarn species. Incubation of whole clams in elevated phosphate (10 M) reduced their capacity for phosphate uptake, but the uptake capacity of the clam's zooxanthellae population was not influenced. In addition, there was no change in the zooxanthellae density and the N:P ratio, of these algae., On the other hand, cultured zooxanthellae were influenced by the phosphate regimen of their culture medium. Compared with controls (0 M P), addition of 10 M phosphate to the culture medium caused an increase of 100% in cell density and decreases of 50% in the N:P ratio, and 80% in the phosphate-uptake capacity of the zooxanthellae. Zooxanthellae freshly isolated from the clams exhibited properties similar to those of zooxanthellae cultured in the absence of phosphate. These results demonstrate that the zooxanthellae population of T. gigas have limited access to the inorganic phosphate in sea water and the phosphate reserves within the animal host.     

Genetic evidence for the occurrence of a cryptic species with the littoral nemerteans Lineus ruber and L. viridis (Nemertea: Anopla)

Lineus ruber and L. viridis are common intertidal heteronemerteans found on the coasts of northern Europe and the east coast of North America. The two species resemble each other morphologically and were synonymised for many years prior to being separated on the basis of larval development. In this study, specimens of L. ruber and L. viridis were collected from sites along the west and southwest coast of Britain, northern France and the east coast of North America. The external morphology and allele frequencies of isozymes of the two species were compared from all sites. The external morphology of L. ruber and L. viridis was similar but they could generally be separated by colour. Allele frequencies for up to 13 enzyme loci between sympatric populations of L. ruber and L. viridis indicated that these two species are genetically very different (Nei's genetic identity=0.090 to 0.083). Allele-frequency data also indicated the presence of a third genetic type occurring sympatrically with populations of both L. ruber and L. viridis on the coasts of Britain and France but not on the coast of North America. Fixed differences in allele frequencies between populations of the third genetic type and sympatric populations of L. ruber and L. viridis were observed across multiple loci. Genetic identity between the third genetic type and sympatric populations of L. ruber and L. viridis were extremely low (Nei's genetic identity =<0.078). Such large genetic differences between populations indicate a barrier to gene flow and reproductive isolation. The aberrant type, which exhibits sufficient morphological variation to prevent individuals being distinguished from those of both L. ruber and L. viridis, therefore represents a separate species. The low genetic identities found in intrageneric comparisons of species found in this study have been found in other studies on nemerteans. They may indicate systematic problems within these groups or other phenomena such as morphological stasis.     

Ecological Biodiversity of Marine Nematodes in Samples from Temperate, Tropical, and Deep-Sea Regions

Little is known about the biodiversity of free-living nematodes. We have attempted to provide baseline information about the natural diversities (those not influenced by pollution) that might be expected in six biotopes. Seventeen marine nematode data sets consisting of 197 samples were standardized to allow a comparison of alpha diversity, or sample diversity, from temperate estuarine, tropical sublittoral, temperate sublittoral, bathyal, abyssal, and hadal biotopes, which were selected on criteria of depth and latitude. The diversity analysis methods we employed were rarefaction curves; three weighted diversity indices of species richness, SR, H', and ES(X); and two equitability indices, J' and V. Diversity was significantly different in the six biotopes. The weighted indices of species richness were more capable of resolving differences between the biotopes than were the equitability indices, whose large standard errors suggested that they were more influenced by local, small-scale ecological factors. This suggests that species richness is a better measure than equitability for large-scale comparisons of biotopes or regions. The ES(X), which is robust to sample size variations, was more efficient than the weighted indices of species richness, which were easily influenced by sample size. There was a nonlinear relationship between depth and diversity with the bathyal and abyssal biotopes displaying the highest diversity. The tropical sublittoral biotope was not more diverse than the temperate sublittoral biotope. The lowest diversities were found in the physically challenging temperate estuarine and hadal biotopes.     

Marble wastes and pig slurry improve the environmental and plant-relevant properties of mine tailings

Poor soil fertility is often the biggest challenge to the establishment of vegetation in mine wastes deposits. We conducted field trials in the El Gorguel and El Lirio sites in SE Spain, two representative tailing ponds of similar properties except for pH, to understand the environmental and plant-relevant benefits of marble waste (MW) and pig slurry (PS) applications to mine tailings. Low pH (5.4) tailings (El Lirio) exhibit reduction of up to fourfold in bio-availability of metals as shown by the DTPA-Zn, Pb, water-soluble Zn, Pb and up to 3× for water-soluble Cd. Tailings in El Gorguel have high pH (7.4) and did not exhibit significant trends in the reductions of water-extractable Zn, Pb, Cd and Cu. Improvements to the edaphic (plant-relevant) properties of tailings after the amendments are not as sensitive to pH compared to the environmental characteristics. The two sites had increases in aggregate stability, organic matter (total N and organic C) although total N is higher in the El Gorguel (up to 212 μg N kg^?1) than the El Lirio (up to 26 μg N kg^?1). However, cation exchange capacities are similar in both sites at 15.2 cmol(+) kg^?1. We conclude that the characteristics, especially pH, of tailing materials significantly influence the fate of metals but not improvements to plant-relevant properties such as cation exchange capacity and aggregate stability 1 year after the application of MW and PS amendments.     

Deconstructing an assemblage of “turtle” barnacles: species assignments and fickle fidelity in Chelonibia

Barnacles in the genus Chelonibia are commensal with a variety of motile marine animals including sea turtles, crustaceans, and sirenians. We conducted a worldwide molecular phylogenetic survey of Chelonibia collected from nearly all known hosts to assess species relationships, host-fidelity, and phylogeographic structure. Using DNA sequences from a protein-coding mitochondrial gene (COI), a mitochondrial rRNA gene (12S), and one nuclear rRNA gene (28S), we found that of four species, three (C. testudinaria, C. patula, and C. manati) are genetically indistinguishable. In addition, we show each utilizes a rare androdioecious mode of reproduction involving complemental males. In contrast, the fourth species (C. caretta), which is hermaphroditic and specializes on turtles, is genetically distinct—leading to the conclusion that the three former taxa are morphotypes of the same species and should be synonymized under C. testudinaria. Phylogenetic analysis resulted in three geographic clades (Atlantic, Indian Ocean/western Pacific, and eastern Pacific) with haplotype parsimony networks revealing no shared haplotypes among geographic regions. Analysis of molecular variance detected significant differences among sequences by region (p < 0.005); conversely, there were no significant differences among sequences when grouped by host or taxonomic designation. Average pairwise genetic distances were lower between the eastern Pacific and Atlantic clades (0.053 ± 0.006) than between the eastern Pacific and Indian Ocean/western Pacific clades (0.073 ± 0.008), suggesting Atlantic and eastern Pacific populations were connected more recently, perhaps until the rise of the Isthmus of Panama. Host use by Chelonibia morphotypes is discussed along with speculation on possible ancestral hosts and support for a “turtle-first” hypothesis.     

The effects of an abnormal decrease in temperature on the Eastern Pacific reef-building coral Pocillopora verrucosa

Coral bleaching events are associated with abnormal increases in temperature, such as those produced during El Niño. Recently, a breakdown in the coral–dinoflagellate (genus Symbiodinium) endosymbiosis has been documented in corals exposed to anomalously cold-water temperatures associated with La Niña events. Given the ecological significance of such events, as well as the threat of global climate change, surprisingly little is known about the physiological response of corals to cold stress. This study evaluated some physiological effects of continuous temperature decline in colonies of the eastern Pacific reef-building coral Pocillopora verrucosa. Twenty days of incubation at 18.5–19.0 °C resulted in a substantial decrease in holobiont lipid and Chla content, as well as an increase in Symbiodinium density. These observations suggest a combination of symbiont acclimation due to the temperature decline and reallocation of carbon toward algal growth as opposed to translocation to the host coral. With a decreased availability of symbiont-derived carbon, the coral likely catabolized storage lipids in order to survive the stress event. Despite this stress and some tissue necrosis, no mortality was noted and corals recovered quickly when returned to the ambient temperature. As these results are in marked contrast to similar studies investigating elevated temperature on this coral from this same location, Pocillopora in the Mexican Central Pacific may be more prone to long-term damage and mortality during periods of ocean warming as opposed to ocean cooling.     

Human health risk from Pb in urban street dust in northern UK cities

The presence of Pb in the environment can cause significant health problems. These issues are exasperated when the lead is in a more amenable form for potential ingestion. This study investigates the potential human health risk from Pb in urban street dusts. The lead levels in urban street dust in major city centres in northern UK have been compared to levels determined in 35 cities around the world. With a few exceptions, it was noted that the mean Pb levels in this study exceeded those found in other cities worldwide. Samples (n = 15) of urban street dust were collected across five city centres, and specifically in areas in which pedestrians are likely to concentrate, as well as near historical buildings. Typical total lead concentrations across all sampling sites ranged from 306 to 558 mg/kg. The human health risk was assessed using oral bioaccessibility testing of the urban street dust. The mean oral bioaccessibility data, irrespective of site and sample location, were in the range 43 ± 9 %. The total and bioaccessible concentrations of lead were compared to the estimated tolerable daily intake (TDI_oral) values based on unintentional soil/dust consumption. It is noted, in all cases, that the maximum estimated lead daily intake exceeded the TDI_oral. An alternative approach for assessing the daily intake is proposed based on the actual measured air quality in selected cities on the same day as the sampled urban dust.     

Density dependence in social behaviour: home range overlap and density interacts to affect conspecific encounter rates in a gregarious ungulate

Sociality is poorly understood in the context of population processes. We used wild, female elk (Cervus canadensis) equipped with proximity-logging radio collars (n?=?62) from Manitoba, Canada (2007–2009), to test for modifying effects of population density (two areas: 0.42 and 0.22 animals/km²) on the relationship between two measures of sociality. This included the rate at which collared individuals encountered one another per year (encounters logged as animals ranging to within 1.4 m of each other) and the extent to which animals overlapped in annual home range (proportion of shared minimum convex polygon ranges). Overlap was significantly greater in the high density area compared to that of the low, but not if we only considered individuals that directly encountered each other, implying that familiar individuals will maintain a constant degree of range overlap regardless of density. Encounter rate was nonlinearly related to home range overlap. This relationship was also density-dependent, exhibiting negative density dependence at high proportions of overlap, primarily in the high density subpopulation. Sociality, as defined by two interacting measures of behaviour—encounter rate and home range overlap—exhibits a complex nonlinear relationship; we discuss the implications of these results as they pertain to sociobiology, resource competition, and pathogen transmission.