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Plant Zonation Changes in the Tidal Portion of the Delaware River
Alfred E. Schuyler, Sarah B. Andersen and Valerie J. Kolaga
Proceedings of the Academy of Natural Sciences of Philadelphia
Vol. 144 (1993), pp. 263-266
Published by: Academy of Natural Sciences
Stable URL: http://www.jstor.org/stable/4065010
Page Count: 4
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Shoreline plant species that usually grow in brackish conditions now extend farther upstream in the Delaware River than they did earlier in the 20th century. Eleocharis parvula and Sagittaria calycina have the most pronounced upstream extensions, from New Castle County, Delaware, and Salem County, New Jersey, upstream to Bucks County, Pennsylvania, and Burlington County, New Jersey. Other species (Lilaeopsis chinensis and Spartina alterniflora) now occur farther upstream in the state of Delaware than they did in the past. Conversely, common shoreline species usually associated with freshwater conditions (Cyperus bipartitus, Juncus acuminatus, and Zizania aquatica) have not been found as far downstream as they have been in the past. These upstream and downstream distributional changes indicate that an increase in dissolved solids and chlorides has occurred in the Delaware River. There is evidence that some freshwater shoreline and submerged species have been eliminated from the downstream portions of their ranges in Delaware or from the entire estuary because of environmental degradation. Six submergents (Ceratophyllum demersum, Potamogeton crispus, Potamogeton epihydrus, Potamogeton nodosus, Potamogeton spirillus, and Ranunculus longirostris), that used to occur in the vicinity of Wilmington during the late 19th century, probably will not return to this area because conditions apparently are more brackish now than they were then. A few freshwater shoreline species may return to northern Delaware above Wilmington with improved habitat quality.
Proceedings of the Academy of Natural Sciences of Philadelphia © 1993 Academy of Natural Sciences