Application of arsenic baselines in the assessment of soil contamination in Finland

In Finland, a new Government Decree on the Assessment of Soil Contamination and Remediation Needs (214/2007) came into force on 1 June 2007. According to the Decree, natural baseline concentration levels should be taken into account when assessing potential soil contamination and the need for remediation. This applies particularly in the case of toxic metallic elements, since baseline concentrations may naturally be rather high. The new decree prescribes soil screening values for 52 substances or groups of substances. The natural baseline concentrations have been taken into account in the definition of the screening values for inorganic pollutants. The Geological Survey of Finland (GTK) carried out a nation-wide geochemical mapping of till on a reconnaissance scale in 1983 and on a regional scale during 1984–1992. These surveys have provided information on natural elemental distribution in subsoils of the glacial till. However, some important trace elements in regional mapping such as arsenic are missing from the analysis, and subsoil samples do not reflect the diffuse anthropogenic input. Thus, GTK has continued the survey work by determining geochemical baselines around suburban areas. Samples have been taken from humus, topsoil and subsoil layers, and the soil parent material has covered sandy soils, glacial tills and fine-grained sediments. According to the studies, a regional difference in the levels of arsenic and some other trace elements can be clearly seen, especially in minerogenic soils. The results illustrate the importance of information on regional baseline concentrations while assessing potential soil contamination.     

Genetic heterogeneity in a single year-class from a panmictic population of adult blue rockfish (<Emphasis Type="Italic">Sebastes mystinus</Emphasis>)

We used microsatellite genetic markers to investigate adult population structure and the formation of a new year-class in Sebastes mystinus (blue rockfish). Since S. mystinus may live as long as 45 years and reach reproductive age at approximately 5 years, the adult population may contain as many as eight generations of reproductive adults. We investigated whether the juveniles of the 2000 year-class and the adult population were genetically homogeneous along the California coast. We sampled approximately 100 juveniles from three sites, two sites along the Monterey Peninsula (Carmel and Monterey) in central California and one at Fort Ross in northern California, and approximately 50 adult S. mystinus from five sites throughout the population center. The adult sampling spanned approximately 700 km from the northern Channel Islands to Fort Bragg. The juveniles showed significant heterogeneity in allele frequencies among distant locations and genetic homogeneity among adjacent locations. In contrast, the adults showed genetic homogeneity over large distances (San Miguel Island to Fort Bragg), indicating little limitation of gene flow in this region. Allele frequencies of juveniles differed from adult samples and in some cases reduced genetic diversity indicative of sweepstakes recruitment (small sample of the adult reproductive potential). The genetic structure of the 2000 year-class suggests that despite a genetically homogenous adult population, settled juveniles can be genetically heterogeneous along the California coast. The results also suggest that the adults, with several year-classes, are capable of maintaining a panmictic population despite the genetic distinctiveness of individual year-classes.     

Accumulation of cadmium and zinc in <Emphasis Type="Italic">Evodiopanax innovans</Emphasis>

The use of tree species for phytoremediation of contaminated soil offers the advantage of a large biomass in which to store contaminants. We investigated the cadmium (Cd) and zinc (Zn) accumulation ability of Evodiopanax innovans, a common deciduous tree species belonging to the Araliaceae family and widely found in secondary forests in Japan. Sampling was conducted at an old silver mine. Leaf samples were collected from nine tree species, including E. innovans. The seasonal variation of metal concentrations in the leaves and the detailed distribution of metals in the leaves and twigs of E. innovans were measured. We also analyzed the contents of organic acids in the leaves. The highest concentration of Cd in the leaves of E. innovans was 118 μg/g, which exceeds the threshold level for being considered a Cd hyperaccumulator (100 μg/g). For Zn, the highest value was 1040 μg/g in leaves, which is less than required to qualify as a Zn hyperaccumulator. Both Cd and Zn were found to accumulate in the petioles and veins of leaves and the bark of twigs. Since the oxalic acid content of leaves showed a weak correlation with Cd concentration, oxalic acid may play an important role in the accumulation of Cd. Taking both the Cd concentration level and the biomass of this woody plant into consideration, it may be possible to use E. innovans for the phytoremediation of Cd-contaminated soils.     

Fiddler crab burrowing affects growth and production of the white mangrove (<Emphasis Type="Italic">Laguncularia racemosa</Emphasis>) in a restored Florida coastal marsh

Positive plant–animal interactions are important in community ecology, but relatively little attention has been paid to their effect on the production of mangroves, dominant halophytic trees in tropical coastal marshes. Here, the role of fiddler crab (Uca spp.) burrowing on the growth and production of the white mangrove, Laguncularia racemosa (<2 years old), was examined in a restored marsh in Tampa Bay, Florida (27°41.65 N, 82°30.34 W) with manipulative experiments from June 2006 to May 2007. Fiddler crab burrowing significantly increased mangrove height by 27%, trunk diameter by 25%, and leaf production by 15%, compared to mangroves in crab exclusion enclosures. Additionally, the exclusion of fiddler crabs significantly increased interstitial water salinity from 32.4 to 44.2, and decreased the oxidation–reduction potential of the low organic sediments, but did not affect soil pH or sulfide concentration. Mangrove height, trunk diameter, and leaf production along a transect that varied in crab burrow density were positively associated with the number of crab burrows. Further, the density of sympatric Spartina alterniflora shoots was positively correlated with crab burrow density along the transect. As in temperate marshes, fiddler crabs can have significant ecological effects on mangrove communities, serving as ecological engineers by modulating the amount of resources available to marsh plants, and by altering the physical, chemical, and biological state of these soft sediment communities. In restored coastal systems that typically have very poor sediment quality, techniques such as soil amendment could be used to facilitate a more natural interaction between crabs and mangroves in ecosystem development.     

Flight initiation distance decreases during social activity in lizards (<Emphasis Type="Italic">Sceloporus virgatus</Emphasis>)

Flight initiation distance, the predator–prey distance when escape begins, is predicted by escape theory to decrease if fleeing entails loss of benefits. Shortening of flight initiation distance during social interactions is known only in males and only in a few species. In a previous study, male, but not female, Sceloporus virgatus lizards had shorter flight initiation distance when interacting with tethered conspecifics. Females in that study were not gravid or close to ovulating. I predicted that flight initiation distance would be shorter in gravid females that perform sidle-hopping displays to reject courtship than in lone females. I tested this prediction and examined effects of social interactions by males with free-ranging conspecifics to ensure that previous findings were not artifacts of tethering and experimental introduction of conspecifics. Flight initiation distance was shorter in females when interacting with males than when alone; it was also shorter in males interacting with either sex. Thus, when beneficial for reproductive reasons, social interaction affects flight initiation distance in females, but at other times, it does not. Lesser shortening of flight initiation distance in females than males may be a consequence of greater social benefit to males and protection of reproductive investment by females.     

Impacts associated with the recent range shift of the aeolid nudibranch <Emphasis Type="Italic">Phidiana hiltoni</Emphasis> (Mollusca,Opisthobranchia) in California

In 1977, Phidiana hiltoni (O’Donoghue in J. Entomol Zool (Pomona College, Claremont, California) 19:77–119, 1927) began spreading northward from Monterey, California. By 1992, it had reached Duxbury Reef (37° 53′ 23″ N, 122° 41′ 59″ W), 100 km to the north, where other nudibranchs subsequently appeared to decline. The role of P. hiltoni in this decline was investigated through diet analysis, feeding trials, and comparison of historical and recent abundance data. In the wild, P. hiltoni preyed largely on hydroids, but also showed evidence of predation on nudibranchs. In the laboratory, P. hiltoni attacked most of the dendronotid and aeolid nudibranchs presented to it, ingesting small individuals whole. The pooled abundance of nudibranchs vulnerable to attack by P. hiltoni declined an average of two-thirds at Duxbury Reef since its arrival, compared to (1) no change in the non-vulnerable species and (2) no change in either group at two other sites where P. hiltoni was one to two orders of magnitude less abundant. Phidiana hiltoni therefore appears to have caused this decline, likely through a combination of direct predation and competition for prey. A brief larval period, combined with cyclonic re-circulation in the lee of Point Reyes, may be driving self-recruitment of P. hiltoni at Duxbury Reef, as well as hindering further northward spread.     

Age,experience and reproductive performance in a long-lived bird: a hormonal perspective

The ultimate factors influencing age-specific reproductive performance in birds have been widely discussed, and several hypotheses have been suggested to explain why young/inexperienced breeders have lower reproductive success than older individuals. In comparison, proximate factors and, particularly, hormonal mechanisms influencing age-related reproductive performance have received lesser attention. In this paper, we examined how baseline levels of corticosterone and prolactin, two hormones involved in reproduction, changed with age and experience in a long-lived bird, the Black-browed albatross (Thallasarche melanophris) during the brooding stage. Corticosterone levels were not linked to age, whereas prolactin levels increased until individuals reached 15 years of age. First-time breeders had higher corticosterone levels and lower prolactin levels than experienced ones. Corticosterone levels were not correlated with breeding experience among experienced birds, whereas prolactin levels slightly increased with advancing experience. Among experienced breeders, there was no effect of individual quality on corticosterone and prolactin levels. Baseline corticosterone and prolactin levels were respectively, positively and negatively correlated to time spent fasting/brooding on the nest. Moreover, the probability of successfully fledging a chick was negatively related to corticosterone levels, but not to prolactin levels. Elevated corticosterone levels in first time breeders may serve as evidence for depleted body reserves resulting from lower foraging/brooding capabilities and therefore support the constraint hypothesis. Low prolactin levels in young/inexperienced birds may be interpreted either as evidence for their lower breeding capacities (constraint hypothesis) or for their limited breeding investment (restraint hypothesis). Finally, we report, for the first time, the hormonal changes associated with the onset of senescence. The very old and most experienced birds, which had the lowest probability of successfully fledging a young, displayed elevated corticosterone levels and low prolactin levels, possibly indicating a degradation of breeding skills and/or a disruption of the endocrine system in senescent birds.