National Ocean Service

About: National Ocean Service is a government organization based out in Silver Spring, Maryland, United States. It is known for research contribution in the topics: Algal bloom & Population. The organization has 500 authors who have published 643 publications receiving 46096 citations.

The occurrence of mtDNA heteroplasmy in multiple cetacean species.

Abstract: In population genetics and phylogenetic studies, mitochondrial DNA (mtDNA) is commonly used for examining differences both between and within groups of individuals. For these studies, correct interpretation of every nucleotide position is crucial but can be complicated by the presence of ambiguous bases resulting from heteroplasmy. Particularly for non-model taxa, the presence of heteroplasmy in mtDNA is rarely reported, therefore, it is unclear how commonly it occurs and how it can affect phylogenetic relationships among taxa and the overall understanding of evolutionary processes. We examined the occurrence of both site and length heteroplasmy within the mtDNA of ten marine mammal species, for most of which mtDNA heteroplasmy has never been reported. After sequencing a portion of the mtDNA control region for 5,062 individuals, we found heteroplasmy in at least 2% of individuals from seven species, including Stenella frontalis where 58.9% were heteroplasmic. We verified the presence of true heteroplasmy, ruling out artifacts from amplification and sequencing methods and the presence of nuclear copies of mitochondrial genes. We found no evidence that mtDNA heteroplasmy influenced phylogenetic relationships, however, its occurrence does have the potential to increase the genetic diversity for all species in which it is found. This study stresses the importance of both detecting and reporting the occurrence of heteroplasmy in wild populations in order to enhance the knowledge of both the introduction and the persistence of mutant mitochondrial haplotypes in the evolutionary process.

Spatial Interpolation of Tidal Data in Irregularly-shaped Coastal Regions by Numerical Solution of Laplace's Equation

Abstract: A method was developed for spatially interpolating tidal constituent amplitude and phase data using the numerical solution of Laplace's equation. The solution matches the input data values at ‘ internal boundaries ’, i.e., locations that represent observation stations. The boundary condition at land-water interfaces assumes that the normal derivative is proportional to the spatially-averaged value of the derivative in the normal direction. By adjusting the constant of proportionality at land boundaries, realistic distributions were obtained. An equivalent solution field can also be reconstructed by generating a set of weighting functions, thereby minimizing the number of solution fields needed. The method was tested in a simple basin and the solution was evaluated for a variety of parameters such as cell size, grid orientation, and boundary proportionality constant. The method was then applied to San Francisco Bay and distributions of tidal constituent amplitudes and epochs were compared with those generated by a numerical circulation model.

Decadal Declines of Mercury in Adult Bluefish (1972-2011) from the Mid-Atlantic Coast of the U.S.A.

Abstract: Concentrations of total mercury were measured in muscle of adult bluefish (Pomatomus saltatrix) collected in 2011 off North Carolina and compared with similar measurements made in 1972. Concentrations of mercury decreased by 43% in the fish between the two time periods, with an average rate of decline of about 10% per decade. This reduction is similar to estimated reductions of mercury observed in atmospheric deposition, riverine input, seawater, freshwater lakes, and freshwater fish across northern North America. Eight other studies between 1973 and 2007 confirm the decrease in mercury levels in bluefish captured in the Mid-Atlantic Bight. These findings imply that (1) reductions in the release of mercury across northern North America were reflected rather quickly (decades) in the decline of mercury in adult bluefish; (2) marine predatory fish may have been contaminated by anthropogenic sources of mercury for over 100 years; and (3) if bluefish are surrogates for other predators in the Mid-Atlantic Bight...