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Evelyn J. Lessard

Bio: Evelyn J. Lessard is an academic researcher from University of Washington. The author has contributed to research in topics: Phytoplankton & Plankton. The author has an hindex of 31, co-authored 53 publications receiving 5145 citations. Previous affiliations of Evelyn J. Lessard include University of Rhode Island & University of Maryland, College Park.


Papers
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Journal ArticleDOI
TL;DR: Cellular carbon and nitrogen content and cell volume of nutritionally and morphologically diverse dinoflagellate species were measured to determine carbon to volume and nitrogen to volume relationships.
Abstract: Cellular carbon and nitrogen content and cell volume of nutritionally and morphologically diverse dinoflagellate species were measured to determine carbon to volume (C : vol) and nitrogen to volume (N : vol) relationships. Cellular C and N content ranged from 48 to 3.0 3 10 4 pgC cell 21 21 5

2,137 citations

Journal ArticleDOI
01 Jun 1995
TL;DR: The results temper recent assertions concerning the overwhelming importance of bacterial biomass in the oligotrophic Sargasso Sea but still support a major role for these microorganisms in the open ocean as repositories for carbon and nutrients.
Abstract: Seawater samples were collected from the euphotic zone of the Sargasso Sea near Bermuda in August of 1989 and March–April of 1990. Microbial population abundances, chlorophyll concentration, particulate carbon and particulate nitrogen were measured. Calculations were performed to establish the relative and absolute importance of the various microbial assemblages. The choice of conversion factors (g C and N cell −1 , or g C and N μm −3 ) for the microbial populations dramatically affected the estimation of “living” and “detrital” particulate material in the samples, and the relative importance of the various microbial groups. Averaged over all samples on either of the two cruises, microbial biomass constituted a greater proportion of the total particulate carbon and nitrogen during March–April (55% and 63%, respectively), than during August (≈24% and 30%, respectively) using “constrained” conversion factors that were derived. Accordingly, detrital material constituted the bulk of the particulate material during August, but was similar to the amount of microbial biomass during March–April. The bacterial assemblage constituted the largest single pool of microbial carbon (35%) and nitrogen (45%) in the water, and a significant fraction of the total particulate carbon (≈10–20%) and nitrogen (≈15–30%). Phototrophic nanoplankton (microalgae 2–20 μm in size) were second in overall biomass, and often dominated the microbial biomass in the deep chlorophyll maxima that were present during both cruises. The results temper recent assertions concerning the overwhelming importance of bacterial biomass in the oligotrophic Sargasso Sea but still support a major role for these microorganisms in the open ocean as repositories for carbon and nutrients.

262 citations

01 Jan 1991
TL;DR: A review of the existing data suggests that heterotrophic dinoflagellates can at times dominate the protozoan biomass in coastal and oceanic waters.
Abstract: (...) A review of the existing data suggests that heterotrophic dinoflagellates can at times dominate the protozoan biomass in coastal and oceanic waters. Food items of dinoflagellates include bacteria, flagellates, diatoms, other dinoflagellates and ciliates. An association between diatom blooms and heterotrophic dinoflagellates has been noted in many environments. Feeding rate measurements have indicated that heterotrophic dinoflagellates may be significant consumers of diatom biomass. (...)

231 citations

Journal ArticleDOI
TL;DR: It is concluded that heterotrophic dinoflagellates may have an equally important impact as microheterotrophic grazers of phytoplankton and bacteria in oceanic waters.
Abstract: A dual-isotope method was developed to measure grazing rates and food preferences of individual species of heterotrophic dinoflagellates from natural populations, collected from the Slope, Gulf Stream, and Sargasso Sea and from a transect from Iceland to New England, in 1983 The isotope method measures the grazing rates of microzooplankton which cannot be separated in natural populations on the basis of size Tritiated-thymidine and 14C-bicarbonate were used to label natural heterotrophic and autotrophic food, respectively Nine oceanic dinoflagellate species in the genera Protoperidinium, Podolampas, and Diplopsalis fed on both heterotrophic and autotrophic food particles with clearance rates of 04 to 80 μl cell-1 h-1, based on 3H incorporation, and 00 to 283 μl cell-1 h-1, based on 14C incorporation Two dinoflagellate species, Protoperidinium ovatum and Podolampas palmipes, fed only on 3H-labelled food particles Several species of dinoflagellates fed on bacteria (<1 μm) which had been prelabelled with 3H-thymidine The clearance rates of heterotrophic dinoflagellates and ciliates were similar and within the range of tintinnid ciliate clearance rates reported in the literature As heterotrophic dinoflagellates and ciliates can have comparable abundances in oceanic waters, we conclude that heterotrophic dinoflagellates may have an equally important impact as microheterotrophic grazers of phytoplankton and bacteria in oceanic waters

178 citations


Cited by
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Journal ArticleDOI
TL;DR: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols used xiii 1.
Abstract: Preface to the Princeton Landmarks in Biology Edition vii Preface xi Symbols Used xiii 1. The Importance of Islands 3 2. Area and Number of Speicies 8 3. Further Explanations of the Area-Diversity Pattern 19 4. The Strategy of Colonization 68 5. Invasibility and the Variable Niche 94 6. Stepping Stones and Biotic Exchange 123 7. Evolutionary Changes Following Colonization 145 8. Prospect 181 Glossary 185 References 193 Index 201

14,171 citations

Journal ArticleDOI
TL;DR: Viruses are by far the most abundant 'lifeforms' in the oceans and are the reservoir of most of the genetic diversity in the sea, thereby driving the evolution of both host and viral assemblages.
Abstract: If stretched end to end, the estimated 1030viruses in the oceans would span farther than the nearest 60 galaxies. This reservoir of genetic and biological diversity continues to yield exciting discoveries and, in this Review, Curtis A. Suttle highlights the areas that are likely to be of greatest interest in the next few years. Viruses are by far the most abundant 'lifeforms' in the oceans and are the reservoir of most of the genetic diversity in the sea. The estimated 1030 viruses in the ocean, if stretched end to end, would span farther than the nearest 60 galaxies. Every second, approximately 1023 viral infections occur in the ocean. These infections are a major source of mortality, and cause disease in a range of organisms, from shrimp to whales. As a result, viruses influence the composition of marine communities and are a major force behind biogeochemical cycles. Each infection has the potential to introduce new genetic information into an organism or progeny virus, thereby driving the evolution of both host and viral assemblages. Probing this vast reservoir of genetic and biological diversity continues to yield exciting discoveries.

2,438 citations

Journal ArticleDOI
TL;DR: Cellular carbon and nitrogen content and cell volume of nutritionally and morphologically diverse dinoflagellate species were measured to determine carbon to volume and nitrogen to volume relationships.
Abstract: Cellular carbon and nitrogen content and cell volume of nutritionally and morphologically diverse dinoflagellate species were measured to determine carbon to volume (C : vol) and nitrogen to volume (N : vol) relationships. Cellular C and N content ranged from 48 to 3.0 3 10 4 pgC cell 21 21 5

2,137 citations

Journal ArticleDOI
TL;DR: In this article, applied linear regression models are used for linear regression in the context of quality control in quality control systems, and the results show that linear regression is effective in many applications.
Abstract: (1991). Applied Linear Regression Models. Journal of Quality Technology: Vol. 23, No. 1, pp. 76-77.

1,811 citations

Journal ArticleDOI
TL;DR: As the authors' demands upon the ocean increase, so does the need to understand the ocean as an ecosystem, and basic to the un-derstanding of any ecosystem is knowledge of its food web, through which energy and materials flow.
Abstract: Few of us may ever live on the seaor under it, but all of us are mak-ing increasing use of it either as asource of food and other materi-als, or as a dump. As our demandsupon the ocean increase, so doesour need to understand the oceanas an ecosystem. Basic to the un-derstanding of any ecosystem isknowledge of its food web, throughwhich energy and materials flow.(Pomeroy 1974, p. 499)

1,082 citations