Mercury in Florida Bay fish: spatial distribution of elevated concentrations and possible linkages to Everglades restoration

Health advisories are now posted in northern Florida Bay, adjacent to the Everglades, warning of high mercury concentrations in some species of gamefish. Highest concentrations of mercury in both forage fish and gamefish have been measured in the northeastern corner of Florida Bay, adjacent to the dominant freshwater inflows from the Everglades. Thirty percent of spotted seatrout (Cynoscion nebulosus Cuvier, 1830) analyzed exceeded Florida’s no consumption level of 1.5 μg g−1 mercury in this area. We hypothesized that freshwater draining the Everglades served as the major source of methylmercury entering the food web supporting gamefish. A lack of correlation between mercury concentrations and salinity did not support this hypothesis, although enhanced bioavailability of methylmercury is possible as freshwater is diluted with estuarine water. Stable isotopes of carbon, nitrogen, and sulfur were measured in fish to elucidate the shared pathways of methylmercury and nutrient elements through the food web. These data support a benthic source of both methylmercury and nutrient elements to gamefish within the eastern bay, as opposed to a dominant watershed source. Ecological characteristics of the eastern bay, including active redox cycling in near-surface sediments without excessive sulfide production are hypothesized to promote methylmercury formation and bioaccumulation in the benthos. Methylmercury may then accumulate in gamefish through a food web supported by benthic microalgae, detritus, pink shrimp (Farfantepenaeus duorarum Burkenroad, 1939), and other epibenthic feeders. Uncertainty remains as to the relative importance of watershed imports of methylmercury from the Everglades and in situ production in the bay, an uncertainty that needs resolution if the effects of Everglades restoration on mercury levels in fish are to be modeled and managed

A Brief History of the Study of Fish Osmoregulation: The Central Role of the Mt. Desert Island Biological Laboratory

The Mt. Desert Island Biological Laboratory (MDIBL) has played a central role in the study of fish osmoregulation for the past 80 years. In particular, scientists at the MDIBL have made significant discoveries in the basic pattern of fish osmoregulation, the function of aglomerular kidneys and proximal tubular secretion, the roles of NaCl cotransporters in intestinal uptake and gill and rectal gland secretion, the role of the shark rectal gland in osmoregulation, the mechanisms of salt secretion by the teleost fish gill epithelium, and the evolution of the ionic uptake mechanisms in fish gills. This short review presents the history of these discoveries and their relationships to the study of epithelial transport in general

Enzymatic processing of replication and recombination intermediates by the vaccinia virus DNA polymerase

Poxvirus DNA polymerases play a critical role in promoting virus recombination. To test if vaccinia polymerase (E9L) could mediate this effect by catalyzing the post-synaptic processing of recombinant joint molecules, we prepared substrates bearing a nick, a 3′-unpaired overhang, a 5′ overhang, or both 3′ and 5′ overhangs. The sequence of the 5′ overhang was also modified to permit or preclude branch migration across the joint site. These substrates were incubated with E9L, and the fate of the primer strand characterized under steady-state reaction conditions. E9L rapidly excises a mispaired 3′ strand from a DNA duplex, producing a meta-stable nicked molecule that is a substrate for ligase. The reaction was not greatly affected by adding an unpaired 5′ strand, but since such molecules cannot be processed into nicked intermediates, the 3′-ended strand continued to be subjected to exonucleolytic attack. Incorporating homology into the 5′ overhang prevented this and permitted some strand assimilation, but such substrates also promoted strand-displacement DNA synthesis of a type predicted by the 1981 Moyer and Graves model for poxvirus replication. Single-strand annealing reactions are used by poxviruses to produce recombinant viruses and these data show that virus DNA polymerases can process DNA in such a manner as to both generate single-stranded substrates for such reactions and to facilitate the final processing of the reaction products

Genomic analysis of vaccinia virus strain TianTan provides new insights into the evolution and evolutionary relationships between Orthopoxviruses

AbstractVaccinia virus (VACV) strain TianTan was used for much of China's modern history to vaccinate against smallpox, however the only genome sequence contains errors. We have sequenced additional examples of TianTan to obtain a better picture of this important virus. We detected two different subclones. One (TP03) encodes large deletions in the terminal repeats that extend into both VEGF genes and create a small plaque variant. The second clone (TP05) encodes a nearly intact complement of genes in the terminal repeats, except for an insertion of sequences resembling the telomeric 69bp repeats. The TP05 genome spans 196,260bp and encodes 219 genes. The revised sequence documents the integrity of all the genes in the conserved virus core. Phylogenetic methods show that TianTan belongs to a unique clade of VACV, but probably also share a common origin with strains belonging to the Copenhagen/Lister lineage and distinct from the Wyeth/Dryvax lineage

Development of neuroendocrine components of the thyroid axis in the direct-developing frog Eleutherodactylus coqui: formation of the median eminence and onset of pituitary TSH production.

Direct-developing frogs lack, wholly or in part, a wide range of larval features found in metamorphosing species and form adult-specific features precociously, during embryogenesis. Most information on thyroid regulation of direct development relies on hormone manipulations; the ontogeny of many thyroid axis components has not been fully described. This analysis examines differentiation of the median eminence of the hypothalamus and production of thyroid-stimulating hormone (TSH) by the pituitary of the direct-developing frog Eleutherodactylus coqui. The median eminence is established two-thirds of the way through embryogenesis. Cells immunoreactive to human TSHb antibodies are first detected during embryogenesis and quantitative changes in TSHb-IR cells resemble those in metamorphosing amphibians. Formation of the median eminence of the hypothalamus and TSHb production by the pituitary precede or coincide with morphological changes during embryogenesis that occur during metamorphosis in biphasic anurans. Thus, while the onset of neuroendocrine regulation has changed during the evolution of direct development, it is likely that these thyroid axis components still mediate the formation of adult features

An Update on the Science of Acidification in the Adirondack Park

This paper provides a review of the science pertaining to all aspects of acidification in the Adirondack Park, updating an earlier review of the science (Cook et al. 2002). The review supports an ongoing social science investigation into the willingness to pay for ecological improvements that would result from reduced acid deposition. This paper builds a bridge between the physical science and social science by providing the background that will allow researchers to accurately summarize the crucial elements of ecological status and improvement in a stated preference survey.acid rain, acidification, stated preference, willingness to pay, benefit estimation

Characteristics and formation of bedrock mega-grooves (BMGs) in glaciated terrain: 1 - morphometric analyses

Bedrock mega-grooves (BMGs) are subglacial landforms of erosion that occur in glaciated terrain in various geological and (palaeo)glaciological settings. Despite a significant literature on BMGs, no systematic morphometric analysis of these landforms has been undertaken. This is a necessary step towards exploring BMG formation and has been successfully applied to other subglacial landforms of similar magnitude (e.g. mega-scale glacial lineations (MSGLs) and drumlins). In this study, BMGs from ten locations across the world are systematically mapped, sampled and measured. Based on the 10th–90th percentile of the aggregated global population (n = 1242), BMGs have lengths of 224–2269 m, widths of 21–210 m, depths of 5–15 m, elongation ratios of 5:1–41:1, and the spacing between adjacent grooves is 35–315 m. Frequency distributions for all metrics are unimodal, strongly suggesting that the sampled BMGs form a single landform population. This establishes the BMG as a geomorphic entity, distinctive from other subglacial landforms. The variability of the metrics and their correlations between and within sites most likely reflect site-specific geological characteristics. At sites which have been associated with fast-ice flow, BMGs display the largest dimensions (especially in terms of length, depth and width) but lowest elongation ratios, whereas BMGs formed under a primary geological control occupy smaller size ranges and have higher elongation ratios. Morphometrically, BMGs and MSGLs plot as different populations, with BMGs being on average 4 × shorter, 3.5 × narrower, 3.5 × more closely spaced and about 2 × deeper. It is suggested that future research focuses on numerical modelling experiments to test rates of erosion in different bedrock lithologies under varying glaciological conditions, and on adding to the body of existing field-derived empirical observations. The latter remains key to validating geological controls over BMG formation and assessing the efficiency of erosion mechanisms