Date Awarded
1968
Document Type
Thesis
Degree Name
Master of Arts (M.A.)
Department
Virginia Institute of Marine Science
Abstract
Surface plankton samples were collected weekly over a 14-month period from the York River at Gloucester Point, Virginia. All dinoflagellates collected were identified to the species level when possible, and the relative abundance of each form was noted. The local dinoflagellate flora was examined with attention being given to environmental factors which might influence its composition. Special emphasis was placed on "red water" blooms.
One hundred eighteen separable forms, representing 20 genera of Pyrrhophyta, were collected. Of these, 84 were identified to the species level with reasonable certainty. Five of the 118 belonged to the class Desmophyceae, the remainder to the class Dinophyceae. In general, thecate Dinophyceae dominated the dinoflagellate flora, except during warmer months when blooms of certain unarmored species occurred. Of the 84 identified species, 43 had not been recorded previously from Chesapeake Bay. Fifty-four species were considered major components of the dinoflagellate flora.
Species occurrence exhibited definite seasonality. Five major floras were recognized: ubiquitous or "year round"; "winter" or cold water; "summer" or warm water; and "spring" and "fall", periods of temperature transition.
Most species were found within moderately restricted temperature and salinity ranges. These species occurred in the plankton only when their requirements for both factors were satisfied. Temperature alone appeared to be limiting for many "summer" species, including most red water forms. Salinity alone had little correlation with dinoflagellate occurrence.
Eight species were dominant in "red water" blooms during the sampling period. Major bloom components were usually accompanied by lesser numbers of other species. Blooms in the York River occurred during summer months when water temperature and salinity were high, although Peridinium triquetrum produced "red water" in the nearby James River in April. Temperature appeared most important in initiating blooms, with windless weather and stable water important in formation and maintenence of discolored water.
The seasonal distribution of the 54 major species is discussed, and illustrations of each are provided.
DOI
https://dx.doi.org/doi:10.25773/v5-t9vz-7s49
Rights
© The Author
Recommended Citation
Mackiernan, Gail Brown, "Seasonal Distribution of Dinoflagellates in the Lower York River, Virginia" (1968). Dissertations, Theses, and Masters Projects. William & Mary. Paper 1539617405.
https://dx.doi.org/doi:10.25773/v5-t9vz-7s49
