THOMAS E. BOWM The Distribution of Calanoid Copepods off r the Southeastern W United States Between Cape Hatteras and j Southern Florida SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY NUMBER 96 SERIAL PUBLICATIONS OF THE SMITHSONIAN INSTITUTION The emphasis upon publications as a means of diffusing knowledge was expressed by the first Secretary of the Smithsonian Institution. In his formal plan for the Insti- tution, Joseph Henry articulated a program that included the following statement: "It is proposed to publish a series of reports, giving an account of the new discoveries in science, and of the changes made from year to year in all branches of knowledge." 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These publications are distributed by subscription to libraries, laboratories, and other in- terested institutions and specialists throughout the world. Individual copies may be obtained from the Smithsonian Institution Press as long as stocks are available. S. DILLON RIPLEY Secretary Smithsonian Institution SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY NUMBER 96 Thomas E. Bowman The Distribution of Calanoid Copepods off the Southeastern United States Between Cape Hatteras and Southern Florida SMITHSONIAN INSTITUTION PRESS CITY OF WASHINGTON 1971 ABSTRACT Bowman, Thomas E. The Distribution of Calanoid Copepods off the Southeastern United States Between Cape Hatteras and Southern Florida. Smithsonian Contri- butions to Zoology, number 96, 58 pages, 1971.—About 100 species of epipelagic calanoid copepods occur in waters off the southeastern coast of the United States. From inshore waters seaward the species diversity increases from less than 10 species/station in coastal waters to more than 40 species/station in some oceanic stations. The species composition changes concomitantly, and, using the Fager- McGowan index of association, coastal, shelf, and oceanic associations have been identified, each with characteristic indicator species. The seaward gradient in diversity is explained by Sanders' stability-time hypothesis. The calanoid fauna south of Cape Hatteras is compared with the fauna north of Cape Hatteras. Two species of Paracalanus, P. quasimodo, new species, and P. indicus, new rank (=P. parvus var. indicus), both formerly referred to P. parvus, are described and compared with the more northern P. parvus. Taxonomic remarks are given concerning Rhincalanus cornutus, Pleuromamma gracilis and P. piseki, and Heterorhabdus papilliger. Official publication date is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Smithsonian Year. UNITED STATES GOVERNMENT PRINTING OFFICE WASHINGTON: 1971 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 • Price 65 cents (paper cover) Thomas E. Bowman The Distribution of Calanoid Copepods off the Southeastern United States Between Gape Hatteras and Southern Florida Introduction modations for eight scientists and ten crew, made In Atlantic waters along the east coast of the United a series of nine cruises over the station grid between States much less attention has been given to the January 1953 and December 1954, making oceano- plankton in the region south of Cape Hatteras than graphic measurements and plankton collections at to that in the region north of Cape Hatteras. South of each station. Cape Hatteras the species of chaetognaths and their distribution have been discussed by Bumpus and Pierce (1955) and Pierce and Wass (1962), and the association of pteropod species with the three water masses off Cape Hatteras has been analyzed by Chen and Hillman (1970). Investigations of planktonic copepods have been for the most part taxonomic studies, especially of Florida Current species (sum- marized in Owre and Foyo 1967) or analyses of vertical movements (e.g., Moore and O'Berry 1957). An overall survey of the patterns of copepod dis- tribution was not possible until an adequate pro- gram of plankton sampling could be carried out. Owing to interests in the relatively unexplored area south of Cape Hatteras by the U. S. Fish and Wildlife Service, the Navy Hydrographic Office, and the Office of Naval Research, a program to in- vestigate these waters was developed in the early STATION POSITIONS 1950s. A pattern of 16 transects forty miles apart, REGULAR O each transect containing 3-6 stations twenty miles SPECIAL Li] apart, was established (Figure 1). The lines ex- tended seaward beyond the axis of the Gulf Stream, and 9 special stations were set up farther offshore. The 97-foot vessel Theodore N. Gill, with accom- Thomas E. Bowman, Division of Crustacea, National Museum IT 76- 75" of Natural History, Smithsonian Institution, Washington, D.C. 20560. FIGURE 1.—Basic station plan. SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY Methods Pierce (1955), Pierce and Wass (1962), and Gray and Cerame-Vivas (1963), hence only a brief sum- The basic physical biological and chemical data, mary is given here. together with procedures and methods, have been The dominant offshore feature is the Gulf Stream published for each cruise. This paper is limited to (Florida Current), which has an average velocity Cruises 1-4 (February-November 1953), for which greater than 150 cm/sec. West of this lies the Caro- the relevant information is given by Anderson, linian Coastal water, composed of Florida Current Gehringer, and Cohen (1956a, 1956b), and Ander- water plus river-runoff water, which extends from son and Gehringer (1957a, 1957b). Cape Hatteras to off Daytona Beach or at times to Plankton tows were made during Cruises 1 and off Cape Kennedy. Carolinian Coastal water is more 2 with a standard half-meter no. 1 silk net with an saline than most coastal water, because (1) there is Atlas-type current meter suspended in the mouth less runoff, (2) the runoff enters from sounds rather to measure the amount of water filtered. During than from river mouths, and (3) the Florida Cur- Cruises 3 and 4 (and later cruises) tows were made rent frequently makes broad excursions over the with the all-metal, half-meter Gulf III sampler shelf. (Arnold and Gehringer 1952), except when adverse Between Cape Hatteras and Cape Cod the shelf sea conditions made it unsafe to tow the Gulf III water is known as Virginian Coastal water and is and the silk net was substituted. Nets were towed colder and less saline than Carolinian Coastal obliquely starting at 70 m (100 m of cable out), or water. It drifts slowly southward along the coast at less in shallow water, and retrieved at the rate neces- about 3-20 miles/day, due to a dynamic current in- sary to bring them to the surface in about 20 min- utes. The silk net was towed at 1-2 knots, the Gulf duced by the addition of fresh water from river III at 5-6 knots. Plankton samples were preserved in runoff. Such a south-flowing dynamic current is 5 percent buffered formalin. very transient in Carolinian Coastal water; it is restricted to a very narrow portion of the shelf Aliquots of 40 ml, comprising 10 percent of the and develops only during periods of substantial run- total sample, were sent to me by William W. Ander- off. There is usually little motion, mostly a drift son, Director of the Bureau of Commercial Fisher- to the northeast. ies, South Atlantic Fisheries Investigations, Bruns- There is no regular communication between the wick, Georgia. Subsamples of the aliquots were re- two coastal waters, but Virginian water may be moved with a 2 ml Stempel pipet and placed in a plastic, rectangular counting chamber for enumera- driven around Cape Hatteras by the northeast tion of the calanoid copepod species. Depending winds which are common from November to May. on the abundance of the plankters, from 1-3 2 ml Between the Gulf Stream and the Virginian subsamples (0.5 to 1.5 percent of the entire sample) Coastal water is a slowly revolving (about 10 cm/ were enumerated. Usually 100 or more, sometimes sec) gyre of slope water. This water has essentially several hundred, copepods were counted and iden- the same characteristics as Gulf Stream water but tified, the number depending on the species diver- has a slightly lower salinity, due to admixture with sity. The number of each species counted was cor- coastal water. No slope water intervenes between rected to the number per 100 m3 of water strained. the Gulf Stream and Carolinian Coastal water. The remainder of the original 40 ml aliquot was The eastern border of the Florida Current merges examined and species not present in the subsample with the Sargasso Sea, without any sharp boundary. were noted. T-S curves are not distinctive enough to separate Both the 40 ml aliquots and the counts of calan- the two water masses in the boundary zone, but oids made from them are permanently stored in they can be distinguished by plotting dissolved 02 the Division of Crustacea, Smithsonian Institution, against sigma-t. The special stations show intrusion where they are available to interested investigators. of Sargasso Sea water, while the regular stations near the axis of the Gulf Stream do not. In the up- Circulation per 100 meters the two water masses cannot be dis- tinguished on any basis, and analysis of the Gill The circulation in the area surveyed by the Gill samples has not brought to light any consistent dif- has been discussed by Bumpus (1955), Bumpus and ferences in the calanoid fauna.