FUNGI OF THE CHESAPEAKE BAY AND ITS TRIBUTARIES. III. THE DISTRIBUTION OF WOOD‐INHABITING ASCOMYCETES AND FUNGI IMPERFECTI OF THE PATUXENT RIVER

The effects of changes in salinity and temperature on the distribution of wood-inhabiting Ascomycetes and Fungi Imperfecti in the Patuxent River were studied. Forty-one species of Ascomycetes and 83 species of Fungi Imperfecti were collected; Pyrenomycetes and dematiaceous Hyphomycetes predominated. Salinity was the most important factor affecting the distribution of fungi, and the major change in species composition occurred where freshwater and saltwater mix. The ratio of Ascomycetes to Fungi Imperfecti increased with increasing salinity, while the number of species collected generally decreased. Triadelphia lieterospora Shearer and Crane was collected only at low temperatures and appears to be the only regularly occurring species whose distribution was affected by temperature. The interaction of temperature and salinity did not affect the distribution of four species that occurred regularly at wide ranges of temperature and salinity. Species composition differed between two limnetic stations, one above and the other below the discharge points of two sewage treatment plants. SEVERAL INVESTIGATIONS of the distribution patterns of wood-inhabiting Ascomycetes and Fungi Imperfecti in estuaries have been made. Gold (1959) found that certain fungi originally described as marine species also occurred in water of low salinity and in freshwater in the Newport River, North Carolina. Distribution patterns of four species appeared to result from the interaction between salinity and temperature. These species occurred in highly saline waters only at high temperatures and, as the water temperatures declined, they occurred in less saline waters. This observation represents field confirmation of the laboratory study by Ritchie (1957), who demonstrated the combined effect of temperature and salinity on the radial growth of fungal colonies in agar culture. At temperatures higher than optimum (25 C), a Phoma sp. tolerated a higher salinity than it did when temperatures were below optimum; this phenomenon was designated the "Phoma pattern. " Hughes (1960) noted that the distribution of wood-inhabiting fungi in the Neuse-Newport Estuary, North Carolina, seemed to be determined primarily by salinity and, secondarily, by water temperature. He studied the distribution of seven 1 Received for publication 2 March 1972. Portion of a dissertation submitted to the Graduate School of the University of Maryland at College Park, in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Botany. The author is indebted to Dr. WV. Klarman for his guidance during the course of this study and to Dr. J. L. Crane for his assistance in the identification of many unusual species. Appreciation is expressed to Natural Resources Institute, University of Maryland, for partial financial support. commonly occurring species and found that only Lignicola laevis Hohnk exhibited the Phoma pattern. Dictyosporium elegans Corda and Pseudoeurotium indicum (Chattopadhyay and Das Gupta) Chattopadhyay exhibited reverse Phoma patterns by being more salt tolerant at low temperatures. Johnson (1967) found that 73 % of the woodinhabiting fungi collected from the Neuse-Newport Estuary were terrestrial species or were representatives of genera known to contain terrestrial species. Eighty-one percent of these were from water of less than 1800 salinity, 7 % were from the freshwater portion of the estuary, and 12% were from various parts of the estuary with salinities from 0-34%o0. Three Ascomycete species exhibited the Phoma pattern if only the fruiting structures on the wood blocks, immediately after removal from the water, were considered. If the blocks were incubated before examination, however, the Phoma pattern did not exist. Schauman (1968) found that 25 wood-inhabiting species in the Weser-Estuary, Germany, could be grouped according to the salinity ranges they could tolerate in the field: the holoeuryhaline species, the euryhaline species, the genuine brackish water species, and the stenohaline species. The distribution of wood-inhabiting Ascomycetes and Fungi Imperfecti in estuaries apparently is affected by salinity and temperature. There was a need for a distributional study in which field collections would be made regularly at short time intervals so that changes in species composition and distribution could be correlated with changes in environmental conditions. There was