A study of patients discharged improved who returned for further treatment to the Veterans Administration Mental Hygiene Clinic.

Thesis (M.S.)--Boston Universit

Invertebrates and their dormant eggs transported in ballast sediments of ships arriving to the Canadian coasts and the Laurentian Great Lakes

The most effective strategy for managing nonindigenous species (NIS) is through prevention of their transport via regulation of introduction vectors. We sampled 135 ships arriving to three different regions of Canada to assess abundance and species richness of invertebrates and their dormant eggs transported in ballast sediments. By sampling ships that followed particular pathways, we were able to compare vector strength to different regions, the invasion risk of transoceanic vs. coastal vessels, and the effect of midocean exchange, length of voyage, and amount of sediment on the richness and abundance of species inside ballast tanks. Although standardized ballast management regulations have been implemented across Canada, the resulting invasion risk is not uniform across regions. Ships arriving to the Atlantic region carried a greater sediment load with correspondingly higher abundance and species richness than those arriving to the Pacific and Great Lakes regions. Abundance and species richness of invertebrates and their dormant eggs associated with transoceanic ships did not differ from that of ships operating along coastal areas of North America. Similarly, midocean exchange did not reduce either abundance or species richness of invertebrate dormant eggs in ships. Finally, the length of voyage did not influence taxonomic composition or abundance of invertebrate dormant eggs but was directly related to survival of active macroinvertebrates. Ballast sediments could introduce new NIS to some regions of Canada despite requirements to manage ships' ballast by midocean exchange. Minimizing sediment accumulation may be the only effective management option for this vector

Are genetic databases sufficiently populated to detect non-indigenous species?

Correct species identifications are of tremendous importance for invasion ecology, as mistakes could lead to misdirecting limited resources against harmless species or inaction against problematic ones. DNA barcoding is becoming a promising and reliable tool for species identifications, however the efficacy of such molecular taxonomy depends on gene region(s) that provide a unique sequence to differentiate among species and on availability of reference sequences in existing genetic databases. Here, we assembled a list of aquatic and terrestrial non-indigenous species (NIS) and checked two leading genetic databases for corresponding sequences of six genome regions used for DNA barcoding. The genetic databases were checked in 2010, 2012, and 2016. All four aquatic kingdoms (Animalia, Chromista, Plantae and Protozoa) were initially equally represented in the genetic databases, with 64, 65, 69, and 61 % of NIS included, respectively. Sequences for terrestrial NIS were present at rates of 58 and 78 % for Animalia and Plantae, respectively. Six years later, the number of sequences for aquatic NIS increased to 75, 75, 74, and 63 % respectively, while those for terrestrial NIS increased to 74 and 88 % respectively. Genetic databases are marginally better populated with sequences of terrestrial NIS of plants compared to aquatic NIS and terrestrial NIS of animals. The rate at which sequences are added to databases is not equal among taxa. Though some groups of NIS are not detectable at all based on available data—mostly aquatic ones—encouragingly, current availability of sequences of taxa with environmental and/or economic impact is relatively good and continues to increase with time

Backcasting and forecasting biological invasions of inland lakes

Human introduction of nonindigenous species constitutes a serious threat to many ecosystems, particularly lakes. Recent attempts to predict invasions have focused on the supply of propagules of nonindigenous species to recipient ecosystems from source populations. Here we develop a spatially explicit “gravity” model to test this concept for Bythotrephes longimanus, a crustacean waterflea from Eurasia that is rapidly invading lakes in Ontario, Canada. The gravity model predicted spread of Bythotrephes based upon seven identified risk factors (e.g., use of contaminated fishing or boat anchor line) that may allow dispersal of either live individuals or their resting eggs from invaded to noninvaded lakes, as well as based on the spatial arrangement of invaded and noninvaded lakes in Ontario. Discriminant analysis of lake gravity scores successfully identified invasion status for 74% of 170 inland lakes. A retrospective analysis of 31 invaded lakes revealed that the order in which lakes were invaded was directly related to the magnitude of vector inflows from invaded sources. Analysis of the dominant vector inflow to each invaded lake revealed a “stepping stone” pattern in which at least five lakes were sequentially invaded from the source population in Lake Huron. One invaded lake (Muskoka) apparently served as an invasion “hub,” resulting in up to 18 additional direct and 17 indirect invasions. Species spread occurred via a combination of dominant, local diffusion (median distance 12.5 km) and rare, long-distance (\u3e100 km) dispersal. Eleven of 131 lakes that were not invaded in 2000 were reported invaded in 2001. Gravity scores of these lakes were significantly higher than those of other noninvaded systems, indicating that susceptibility to invasion can be related to the magnitude of vector inflows. A GIS model based on gravity scores indicated that distribution of Bythotrephes is expected to expand to eastern and northwestern Ontario, although most new invasions are expected to occur in the central region of the province. Our results indicate that quantitative analysis of human dispersal vectors provides a robust starting point with which to assess vulnerability of discrete ecosystems to invasion. Management efforts focused on reducing the number and magnitude of human-mediated dispersal vectors may reduce the rate of invasion of new ecosystems

Influence of Artifact Removal on Rare Species Recovery in Natural Complex Communities Using High-Throughput Sequencing

Large-scale high-throughput sequencing techniques are rapidly becoming popular methods to profile complex communities and have generated deep insights into community biodiversity. However, several technical problems, especially sequencing artifacts such as nucleotide calling errors, could artificially inflate biodiversity estimates. Sequence filtering for artifact removal is a conventional method for deleting error-prone sequences from high-throughput sequencing data. As rare species represented by low-abundance sequences in datasets may be sensitive to artifact removal process, the influence of artifact removal on rare species recovery has not been well evaluated in natural complex communities. Here we employed both internal (reliable operational taxonomic units selected from communities themselves) and external (indicator species spiked into communities) references to evaluate the influence of artifact removal on rare species recovery using 454 pyrosequencing of complex plankton communities collected from both freshwater and marine habitats. Multiple analyses revealed three clear patterns: 1) rare species were eliminated during sequence filtering process at all tested filtering stringencies, 2) more rare taxa were eliminated as filtering stringencies increased, and 3) elimination of rare species intensified as biomass of a species in a community was reduced. Our results suggest that cautions be applied when processing high-throughput sequencing data, especially for rare taxa detection for conservation of species at risk and for rapid response programs targeting non-indigenous species. Establishment of both internal and external references proposed here provides a practical strategy to evaluate artifact removal process

Minimizing invasion risk by reducing propagule pressure: a model for ballast-water exchange

Biological invasions are a major and increasing agent of global biodiversity change. Theory and practice indicate that invasion risk can be diminished by reducing propagule pressure, or the quantity, quality, and frequency of introduced individuals. For aquatic invasions, the primary global invasion pathway is ballast-water transport, and the primary risk reduction strategy is currently open-ocean exchange. Exchange was developed with shipping between freshwater ports in mind, but the majority of shipping connects brackish and marine ports. A worldwide convention, adopted in 2004 by the International Maritime Organization, now mandates ballast-water exchange (or equivalent management) for its 164 member states. Will exchange be as effective in reducing invasion risk for euryhaline species (those capable of tolerating a wide range of salinity levels) in salt-water ports? Here we develop a simple mathematical framework for optimizing ballast-water exchange in terms of exchange level, timing, and species salinity tolerance. Our model shows that when species survival is worse in the post-exchange than in the pre-exchange water, exchange is always effective. However, when survival is equal or better following exchange, a critical level and timing are required for effective exchange. We illustrate the model\u27s applications with a variety of introduced marine and estuarine organisms

Influence of Feeding Habits on Organochlorine Contaminant Accumulation in Waterfowl on the Great Lakes

Zebra mussels (Dreissena polymorpha) are an important component of benthic communities in the Great Lakes and are exploited by a host of predators, including waterfowl. In this study, we analyze diet content and stable isotope and organochlorine contaminant patterns in Lesser Scaup (Aythya affinis), Greater Scaup (Aythya marila), Bufflehead (Bucephala albeola), Redhead (Aythya americana), Canvasback (Aythya valisineria), and Mallard (Anas platyrhynchos) collected from three sites (Fighting Island, western Lake Erie, Big Creek) in the lower Great Lakes. Lesser and Greater Scaup from Fighting Island were classified as either zebra mussel ( ≥ 67% of diet) or macrophyte ( ≥ 85% of diet) consumers. Bufflehead, Canvasback, Mallard, and Redhead consumed mainly ( ≥ 89%) macrophyte at Fighting Island. Zebra mussel was the principal food of Lesser Scaup ( \u3e 99%), Greater Scaup (97%), and Bufflehead (72%) in western Lake Erie. Stable isotope analysis revealed enrichment of δ15N in Lesser Scaup ( ≥ 2.24‰), Greater Scaup ( ≥ 1.28‰), and Bufflehead ( ≥ 0.63‰) that exploited mussels relative to conspecifics with macrophyte diets and relative to mussel prey. Representative contaminants of low (hexachlorobenzene [HCB]), moderate (PCB [polychlorinated biphenyl] 153), and high (PCB 180) hydrophobicity were examined in waterfowl. Lipid-normalized concentrations of PCBs 153 and 180 were significantly higher in scaup and Bufflehead that consumed Dreissena than in individuals that ate mainly macrophytes. Among taxa that consumed primarily Dreissena concentrations of PCBs 153 and 180 were significantly higher in individuals from Lake Erie than in those Fighting Island. Principal components analysis revealed broad differences in contaminant patterns of waterfowl based principally on diet. Results from this study illustrate that Dreissena has become a primary food source of some waterfowl in the lower Great Lakes and serves as an effective conduit for transfer of persistent organic contaminants to higher trophic levels

Seasonal and Vertical Distribution, Food Web Dynamics and Contaminant Biomagnification of Cercopagis pengoi in Lake Ontario

During the early growth season of 1999 to 2001, Cercopagis abundance in offshore waters of Lake Ontario remained low (less than 30 individuals/m3). From late July, its abundance increased rapidly until it peaked during August. After first appearing in 1998, maximum offshore abundance in Lake Ontario decreased each year since 1999 (1999:1759/m3; 2000: 679/m3; 2001: 355/m3). Cercopagis appears not to migrate below the thermocline and is restricted to the epilimnion. A comparison of pre- and post-invasion average abundance of Daphnia retrocurva, Bosmina longirostris and Diacyclops thomasi suggests that Cercopagis is having a major effect on zooplankton composition and abundance in Lake Ontario. Abundance of all three species has decreased significantly in the offshore waters since the invasion of Cercopagis. Preliminary results also suggest that insertion of Cercopagis pengoi into the Lake Ontario food web will not elevate levels of hydrophobic organic compounds in salmonids through biomagnification

Invasion risk of active and diapausing invertebrates from residual ballast in ships entering Chesapeake Bay

ABSTRACT: We examined the invasion risk posed by active invertebrates and their diapausing stages (e.g. resting eggs, quiescent adults) carried in residual sediment and water of non-ballasted ships to Chesapeake Bay. Many taxa were recorded that are not native to Chesapeake Bay, supporting the contention that residual ballast represents an invasion vector of some risk to marine systems. Composition and propagule supply differed relative to that in ships entering the Laurentian Great Lakes (e.g. marine taxa dominated in Chesapeake Bay ships), indicating that risk varies geographically. Average abundances of active invertebrates in residual sediment (1002.1 ind. kg–1) and water (2.7 ind. l–1), and diapausing eggs in sediments (779.4 eggs kg–1), were typically low relative to those in ships entering the Great Lakes (1322.5 ind. kg–1, 10.9 ind. l–1 and 3650.0 eggs kg–1, respectively). However, due to high variability among ships, differences were not statistically significant. The major cause of composition and abundance differences is dissimilar trade routes between each system, with vessels entering Chesapeake Bay primarily originating from marine rather than freshwater ports, and because diapausing stages are less commonly found among marine invertebrates. Low propagule supplies, predominant intra-continental ship movements, and salinity disparity between the upper (20 to 28‰) and lower (3 to 8‰) regions of Chesapeake Bay (where ballast water is loaded and offloaded) may greatly reduce invasion risk and be a contributing factor to the bay’s low invasion rate: invasion risk from non-ballasted ships here may be low relative to hull fouling or ballast water discharge. Other marine coastal areas may be at greater risk from this vector