Search

Quantitative polymerase chain reaction studies have detected Vibrio parahaemolyticus virulence genes (hemolysins tdh and trh) in Rhode Island oysters and waters. Illness caused by V. parahaemolyticus is currently rare in Rhode Island; however, there is concern over Increasing aquaculture and water temperatures. The aim of this study was to characterize further the genetic diversity of V. parahaemolyticus in Rhode Island to determine disease risk. The genetic profile of pathogenic (tdh+ and/or trh+) strains and environmental (tdh-/trh-) strains of V. parahaemolyticus isolated from Rhode Island oyster and water samples was compared with pandemic and clinical strains using repetitive extragenic palindromic polymerase chain reaction. Of the 291 V. parahaemolyticus colonies isolated, 27 were pathogenic strains, with 25 of 291 (9.0%), tdh-/trh+; 1 of 291 (0.3%), tdh+/trh+; and 1 of 291(0.3%), tdh+/trh-. Rhode Island isolates did not cluster closely with pandemic or clinical strains. Isolates containing tdh and/or trh genes from Rhode Island waters were predominantly tdh-/trh+, in contrast with a predominance of tdh+/trh- or tdh+/irh+ strains in Alaska, the Pacific Northwest, and the Gulf of Mexico. Similar to other studies in the United States, a high level of genetic diversity in pathogenic and environmental strains of V. parahaemolyticus was seen. This study clarified the diversity and virulence gene content (tdh and trh status) of V. parahaemolyiicus isolates from Rhode Island waters. [ABSTRACT FROM AUTHOR]

The emergence of epizootic shell disease in the American lobster (Homarus americanus) has been devastating to the fishing industry in southern New England. In response, research was initiated to understand the roles of the environment, pathogens, and pollutants in the ecology and etiology of the disease. A comprehensive project was initiated in which tissues and hemolymph from 100 lobsters were collected from an endemic area of disease, Narragansett Bay, Rl. The project has moved forward with the purpose of compiling, synthesizing, and propagating the findings from the "100 Lobsters" Project. The resulting tissue bank and Web-based data repository and instructional tools serve as a nascent demonstration project to both the scientific community working on this disease as well as to members of the lobster industry. [ABSTRACT FROM AUTHOR]

To determine if population density in areas closed to fishing in Narragansett Bay is causing differences in the reproductive potential of the organisms, this study used two approaches to determine the reproductive condition of the animals. The first approach consisted in employing a gravimetric condition index (Cl) to evaluate the general condition of quahogs from nine different sites, 3 sites open conditionally for fishing (conditional areas) and 6 sites closed to fishing. The second approach was a determination of gonadal index (GI) of a subset of the sample sites, by histological observation of gonadal tissue sections. Initial sampling included determination of Cl only, and lasted from March 25 to Sep. 22, 2005. The subset of six of the Sites was sampled the next year (2006), every three weeks from April 15 until Sep. 28 to determine Cl and the gonadal index (GI). Results show that there is a significant difference between the Cl of northern quahogs from conditional areas and quahogs from closed areas (P < 0.001). There is a significant difference in GI between sites at (P < 0.10). The Cl in conditional areas was consistently higher than in closed sites indicating that maturation and reproductive stages are more prevalent in conditional areas than in closed sites. When sites were separated into three categories: conditional fishing sites; coves; and Providence River sites, the GI and Cl of the conditional areas were always higher than the Cl and GI of all the other sites. The coves had intermediate indices, and the Providence River sites always had the lowest indices. The results indicate that the populations of quahogs in the closed sites sampled are not completing the gonadal cycle as expected and that the reproductive capability of the quahogs in conditional areas is higher than those in closed areas. Possible explanations to this condition include lower water quality in the closed areas, low dissolved oxygen concentration especially during the summer, poor bottom conditions and high population density. Although, not one single characteristic of the environment is solely responsible for the reproductive condition of the quahog population, density appears to have significant effect. [ABSTRACT FROM AUTHOR]

The power of sclerochronology as a tool for interpreting the life history of aquatic organisms and the marine environment they inhabited lies in the occurrence of periodic and repeating structures within the skeletal parts of these organisms. Previous work examining the internal growth patterns of northern quahog (=hard clams), Mercenaria mercenaria (L.), along the Atlantic Coast has established their periodicity; however, the two existing descriptions of the annual growth pattern for hard clams from Narragansett Bay, RI are not consistent with one another. One study identified a translucent slow growth band in the summer and the winter, whereas the other study identified a translucent slow growth band only in the winter. To facilitate future sclerochronological analyses using Narragansett Bay hard clams, variations in the existing descriptions of the annual growth pattern were clarified. We found high variability in the annual growth pattern of M. mercenaria collected during the summers of 2005 and 2006. In approximately half the mature individuals observed, the winter growth breaks were separated by three bands, an opaque band of rapid growth in the spring, a translucent slow growth band in the summer, and a second opaque band of rapid growth in the fall. As these individuals approached senility, the pattern became compressed into two seasonal bands, a single opaque band of rapid growth in the spring and a single translucent band of slow growth encompassing both summer and fall. Growth in the remainder of the samples exhibited only two seasonal bands throughout the mature and senile period, an opaque band of rapid spring growth and a translucent band of slow growth throughout the summer and fall. To confirm the patterns observed, we analyzed δ18O from a subsample of shells. After placing the earlier descriptions and the current description of growth in Narragansett Bay hard clams in chronological order, it appears as though the changing environment of Narragansett Bay was reflected in the growth pattern of these clams. This study emphasizes the importance of validating annual growth patterns even in a region where the periodicity of the species has been confirmed. Changes in the marine environment may alter the patterns in the skeletal structures of aquatic organisms as well as their growth rates. [ABSTRACT FROM AUTHOR]

Studies were undertaken to determine the relationship between size of northern quahogs Mercenaria mercenaria and the rate at which they transport aspartic acid. Quahogs ranging from 25 to 103 mm valve length were collected in Narragansett Bay and placed in seawater aquaria (27 ppt, 20 °C) and allowed to pump water actively. Uptake experiments were carried out using 1 μmol/L C14 radiolabeled aspartic acid. Aspartate transport rates in μmol/h can be related to valve length by the allometric equation with a = 24.32 and b = 0.905 when valve length is in mm. In May 1990, near-bottom samples of seawater were taken from five locations in Narragansett Bay for analysis of dissolved free amino acids (DFAA) by high-pressure liquid chromatography (HPLC). Results showed that the mean total DFAA concentration was 667.6 nmol/L ± 167.3 SD, with the top five being serine, alanine, aspartic acid, glutamic acid, and glycine. A simple spreadsheet model was used to assess the relative importance of the uptake of DFAA vis-à-vis the filtration of particulate organic matter by M. mercenaria. In the model, environmental DFAA concentrations and uptake rates by quahogs determined in this study are compared with literature values for particulate organic nitrogen concentrations and filtration rates by quahogs. On an annual basis, uptake of DFAA can account for about 14% of the total organic nitrogen uptake by quahogs. Uptake of DFAA by these benthic filter feeders may be a pathway of benthic-pelagic nutrient coupling that is often overlooked in coastal ecosystem analyses. [ABSTRACT FROM AUTHOR]