Brian Wysor

Back to Brian's Homepage | C.V.

ABSTRACTS

---

Taxonomic delimitation of three morphological variants of Desmarestia in the eastern North Pacific.

Friday Harbor Laboratories, University of Washington
Molecular Population Biology and Ecology

Summer 1998

Taxonomic delimitation in the genus Desmarestia has traditionally been assessed on the basis of morphology. In more recent times, investigations of molecular markers in the Desmarestiaceae have provided independent tests of morphological phylogenies and have enhanced resolution in phylogenetic studies because many of the morphological characters used in earlier studies have since been determined to be highly plastic. In this study, the internal transcribed spacer-2 (ITS2) region of the ribosomal DNA (rDNA) was sequenced to test the genetic similarity of three morphological variants which have been described variously as varieties of a single species or as distinct species. The results nest well with available molecular phylogenies and support a species level designation.

(L-R) Desmarestia foliaceae, D. munda, D. ligulata

(all images approximately same scale)

 

Back to C.V.

---

Taxonomic and nomenclature confusion in the widely distributed red alga, Laurencia obtusa

Smithsonian Institution, National Museum of Natural History
Research Training Program

Summer 1996

Diverse, unique chemistries reported from the natural products of the red alga reported as Laurencia obtusa (Rhodomelaceae) suggest that several species may have been identified as "L. obtusa." This species has a long published history of taxonomic and nomenclature confusion and, as currently understood (misunderstood?), is widely reported from temperate to tropical waters of the Atlantic, Indian and Pacific Oceans and the Australian, Caribbean and Mediterranean Seas. In this study we address the question of several specimens identified as L. obtusa by testing the hypothesis that only a single species exists. An encompassing set of characters was established to evaluate the taxonomic status of L. obtusa from the Caribbean. Comparative morphological studies were conducted on the vegetative and reproductive structures in marine algae from the type locality (England) and the Caribbean Sea (Belize and Puerto Rico) to resolve the taxonomic features of both groups of algae. Subtle differences were observed between English and Caribbean species with regard to cortical cell arrangement, protrusion of cortical cells, relative abundance of secondary pit connections and tetraspore development. The taxonomy of this alga remains obscure, however, ontogenetic studies may prove promising in resolving taxonomic features of this marine alga.

Back to C.V.

A Photomicrographic Survey of the Springtime Phytoplankton Assemblage in Southampton Waters

Southampton College

Spring 1996

 

The following is a small photomicrographic collection of phytoplankton common to the Northeastern coast of the United States and specifically to Long Island. In addition to the marine representatives of the spring phytoplankton assemblage of Southampton waters, there is a small section detailing a few freshwater species. It should be noted, however, that, while organisms have been split into marine and freshwater genera based on the site of collection they are not necessarily limited to such distribution. Many of the genera presented are common to both marine and freshwater environments.

 

All collections were made within the township of Southampton, NY using a 63( mesh plankton net thrown from shore and drawn in by hand. The freshwater site was Big Fresh Pond, a spring-fed kettle pond, and various marine sites included the Ponquogue Bridge, Shinnecock Canal and Shinnecock Inlet. All of the marine sites are located on Shinnecock Bay which is a well-mixed, shallow water estuary connected to the Atlantic ocean via the Shinnecock Inlet and to the Peconic Bay estuary via the Shinnecock Canal. These sites provided excellent diversity in that freshwater, estuarine and oceanic species could be obtained.

 

The goal of this study was twofold: to document some of the local species of phytoplankton and to institute various photomicrographic techniques to achieve good resolution in cellular detail. The Microflex HFX-II photomicrographic attachment and Nikon FX-35A camera were used in conjunction with the Nikon Optiphot biological microscope to accomplish these tasks. Phase contrast, dark and bright field as well as fluorescence microscopy were employed to enhance various cellular features. Details of the microscopy setup are described in the caption of each image.

 

Back to C.V.

An ecological survey of the Oyster Pond Reef Laminaria saccharina bed, Orient Pt., NY

Southampton College

Fall 1995

An ecological survey of the Oyster Pond Reef Laminaria saccharina bed at Orient Pt., NY was completed. Species composition was determined throughout the bed and on randomly selected L. saccharina sporophytes. The system is characterized by high species diversity and high productivity, however substrate appears to be a limiting factor. Total kelp bed production appears to be substantially supplemented by epiphytic production. Over 25% of the ecosystem flora was epiphytic while 50% of the faunal composition was strongly associated with the kelp. This survey serves as a pilot study providing a basic foundation from which future quantitative studies can be directed.

Back to C.V.

A comparison of calculated pCO2, based on total alkalinity and total carbon dioxide measurements, to gas chromatographic determination of pCO2

Southampton College/Brookhaven National Laboratory

Fall 1995

Surface water measurements of total alkalinity (AT) and total carbon (CT) were made in the Eastern Indian Ocean aboard R/V Knorr during the period 1 December 1994 to 19 January 1995. AT and CT values were subsequently used to calculate the partial pressure of CO2 (pCO2) using thermodynamic equations which interrelate the four carbonate system parameters. Calculated values of pCO2 compared well with measured values based on gas chromatographic determination at the beginning of the cruise, however, values became largely divergent in the latter part of the cruise. Further experimentation is required to validate the trends observed in this study, however, these results illustrate that the use of thermodynamic equations to estimate other carbonate system parameters is plausible.

Back to C.V.

Effects of light intensity and nutrient concentration on growth of the toxic, marine dinoflagellate, Alexandrium tamarense

Woods Hole Oceanographic Institution
Summer Student Fellowship

Summer1995

 

The combined effects of light intensity and nutrient concentration were investigated with regard to the growth and photosynthetic physiology of the toxic, marine dinoflagellate, Alexandrium tamarense. Results indicate that A. tamarense is extremely tolerant to highly variable light conditions; light inhibition was achieved at ca. 550 uE m-2 s-1 in one experiment while cells were light limited below 30 uE m-2 s-1. Maximal growth constants were not effected by altering phosphate or nitrate concentrations in the culture media, however, higher nutrient concentrations generally yielded greater biomass. Under conditions of variable light intensity and variable nutrient concentration light was the primary limitation on growth at the levels of light intensity investigated (ca. 30, 100 and 500 uE m-2 s-1). The combined effect of light and nutrient stress appears to be a slightly lower growth constant in cases of extreme nutrient conditions at either high (ca. 500 uE m-2 s-1) or low (ca. 30 uE m-2 s-1) light intensities. Pigment protein complexes are currently being assayed in order to detect differences in the photosynthetic machinery which can be directly linked to the combined influences of both light and nutrient concentration. Results are discussed with regard to the application of these light harvesting pigment-protein complexes as physiological indicators of the cellular, light and nutrient history.

Back to C.V.

 

---

Classical merotomy and grafting experiments in Acetabularia (Dasycladales, Dasycladaceae)

Southampton College

Spring 1995

Merotomy and grafting experiments, pioneered by Hammerling in the 1930s, illustrated the regenerative capability of Acetabularia.. Two species of laboratory strain Acetabularia, a unicellular green alga, were used in intra- and interspecific grafts. Additionally, segments of the unicell were allowed to regenerate. The longevity of morphogenetic substances, first described my Hammerling, was not illustrated by regeneration in the segmented portions, however, development of caps in the grafting experiments showed the tremendous morphogenetic potential of Acetabularia..

click the image to see more

Back to C.V.

Diel periodicity of photosynthesis in the marine diatom Thalassiosira weissflogii

Southampton College
Spring 1994

Net oxygen production was measured as a function of photosynthesis in the marine diatom Thalassiosira weissflogii to verify the presence of a circadian rhythm. While there was rhythmic behavior displayed it can only be credited to a light stimulated response. This behavior persisted through the initial two day L:D period but was not otherwise evident throughout the six day experiment. During the 2-3 days of continuous illumination data was not available due to off-scale dissolved oxygen measurements and through the final two days of L:D a steady decrease in dissolved oxygen was observed. Because of the lack of data during continuous illumination circadian periodicity cannot be confirmed, however, it must be noted that such a rhythm was not necessarily absent.

Back to C.V.

Ingestion rates of an estuarine copepod, Acartia tonsa, in laboratory mesocosms

University of Maryland, Horn Point Environmental Laboratory
Research Experience for Undergraduates

Summer 1994

 

Ingestion rates of the estuarine and calanoid copepod Acartia tonsa were estimated from samples collected at the MEERC (Multiscale Experimental Ecosystem Research Center), a 2700 sq. ft. laboratory housing 27 multicosms under naturally simulated conditions. Zooplankton was sampled twice a week from three mesocosms of the constant depth series; each mesocosm having a constant depth of 1 m and a volume of .1, 1 or 10 m3. The study was part of a collaborative effort on the larger, interdisciplinary project of the MEERC designed to assess scale-dependant variability as it relates to ecosystem health. Copepods were individually selected from collection filters and levels of gut fullness determined using the gut fluorescence method. Ingestion rates were determined according to the equation I = KG, where I is the ingestion rate of A. tonsa in ng chlorophyll a copepod-1, K is the instantaneous gut evacuation rate constant according to the empirical formula of Dam and Peterson (J. Exp. Mar. Biol. Ecol. 124: 1-14, 1988) with units of time-1 and G is the level of gut fullness in ng chlorophyll a. Ingestion rate data was plotted against time and compared to phytoplankton pigment concentrations and copepod densities to assess trophic relationships in each mesocosm. Results suggest that scale does not effect rates of ingestion in A. tonsa; however, the effect of scale may be apparent in lower trophic levels.

 

1.0 cubic meter mesocosms in the MEERC Laboratory

Back to C.V.

The effects of salinity on growth in Laminaria saccharina sporophytes

Southampton College

Fall 1993

Laminaria sporophytes, like all kelps, have extremely high growth rates. An outer layer of cells called the meristoderm is responsible for new cell production. While it covers the entire thallus, cell production is most active in the transition zone, the junction of blade and stipe. It is possible to follow growth in Laminaria sporophytes and consequently determine an average growth rate using a series of punched holes as markers in the blade. Measurements between consecutive holes were taken to determine the growth pattern in various regions of the thallus. The effect of salinity on growth was observed by placing thalli in solutions of different salinities. The fastest growth rate occurred in the hypo saline solution and the slowest growth occurred in the controlled salinity solution of 28.267 parts per thousand, 10 parts per thousand greater than the former solution.

Back to C.V.

TOP

Back to Brian's Homepage