Ostracoda in Texas Bays Wand Lagoons: an Ecologic Study
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CHARLES E. KIj Ostracoda in and LOUIS S. KORMCKER Texas Bays Wand Lagoons: An Ecologic Study SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY • 1970 NUMBER 24 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 not strictly professional." This keynote of basic research has been adhered to over the years in the issuance of thousands of titles in serial publications under the Smithsonian imprint, commencing with Smithsonian Contributions to Knowledge in 1848 and continuing with the following active series: Smithsonian Annals of Flight Smithsonian Contributions to Anthropology Smithsonian Contributions to Astrophysics Smithsonian Contributions to Botany Smithsonian Contributions to the Earth Sciences Smithsonian Contributions to Paleobiology Smithsonian Contributions to ^oology Smithsonian Studies in History and Technology In these series, the Institution publishes original articles and monographs dealing with the research and collections of its several museums and offices and of professional colleagues at other institutions of learning. These papers report newly acquired facts, synoptic interpretations of data, or original theory in specialized fields. Each publica- tion is distributed by mailing lists to libraries, laboratories, institutes, and interested specialists throughout the world. Individual copies may be obtained from the Smith- sonian Institution Press as long as stocks are available. S. DILLON RIPLEY Secretary Smithsonian Institution SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY NUMBER 24 Charles E. King Ostracoda in and Louis S. Kornicker rr> -t-j lexas Bays and Lagoons: An Ecologic Study SMITHSONIAN INSTITUTION PRESS CITY OF WASHINGTON I97O ABSTRACT Charles E. King and Louis S. Kornicker. Ostracoda in Texas Bays and Lagoons: An Ecologic Study. Smithsonian Contributions to Zoology, 24:1-92, 1970.—Ostracods were collected monthly for about one year in Copano Bay, Redfish Bay, and the Laguna Madre, Texas, along a salinity gradient that ranged from 9.7 to 50.0 parts per thousand. This study describes the ostracods encountered and analyzes the environ- mental factors influencing their distribution. 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 : 1970 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price $1.00 (paper cover) Charles E. King Ostracoda in and Louis S. Kornicker Texas Bays and Lagoons: An Ecologic Study Introduction the bottom are periodically exposed by wind tides as- sociated with "northers" or other strong fronts or This report is based on collections of living benthic disturbances. ostracods from Copano Bay, Redfish Bay, and the The Upper Laguna Madre is about 56 km long and Upper Laguna Madre of the central Texas coast (Fig- varies in width from 3 to 8 km. This long, narrow, shal- ure 1). The investigation was designed to emphasize low coastal lagoon extends from Corpus Christi Bay such aspects of ecologic interest as seasonal changes in southward to a sand fill which partly separates it from population size and composition and effects of salinity, the Lower Laguna Madre that extends to Port Isabel, temperature, and substrate. Texas. It varies in depth from approximately 0.3 m REGIONAL SETTING.—Copano Bay, Redfish Bay, and near Corpus Christi Bay to about 2.4 m near Baffin Bay the Upper Laguna Madre are part of a complex of at its southern end. Sandbars and a solid-fill causeway bays and lagoons termed the Aransas Hydrographic almost completely separate the Upper Laguna Madre System by Collier and Hedgpeth (1950). Copano Bay from Corpus Christi Bay. is approximately 19 km long and 8 km wide, with its SALINITY.—Salinities in the study area are con- main axis more or less parallel to the gulf coastline. It trolled mainly by evaporation, which is high during has an area of approximately 181.3 km2 and a maxi- summer months, by influx of fresh water as direct pre- mum depth of about 2.44 m. (See contour map of bot- cipitation, or from creeks and rivers entering Copano tom topography in Shephard and Moore, 1960, Figure Bay, Corpus Christi Bay, and San Antonio Bay to the 4.) Oyster reefs extend in a north-south direction at northeast, and by intermixing with marine water enter- right angles to the main current moving through the ing through Aransas Pass opposite Redfish Bay, Callavo bay. Fresh water enters the bay from a few small Pass near San Antonio Bay, and Cedar Bayou opposite creeks and the Mission and Aransas Rivers. Copano Bay. Water occasionally moves from Baffin Redfish Bay is roughly triangular, about 4 km wide Bay into the southern part of the Upper Laguna from base to apex and approximately 16 km long. The Madre. The hydrographic conditions in the area have bay is more or less an extension of the eastern end of been discussed by Collier and Hedgpeth (1950), Corpus Christi Bay and is rather effectively separated Parker (1959), Shepard and Moore (1960), Behrens from Aransas Bay to the northeast by a chain of low- (1966), Hedgpeth (1967), Odum (1967), and others. lying islands. The bay has an area of 43.5 km2 and A salinity gradient exists from metahaline Copano is very shallow, being less than 1.5 m at its deepest Bay to hyperhaline Upper Laguna Madre. Salinities re- part (Collier and Hedgpeth, 1950). Large areas of corded during the period of collecting ranged from 9.7%O to 50%o as shown in the T-S diagrams presented Charles Edward King, Department of Earth Sciences, East in Figure 2 and Tables 9-19. In Copano Bay, the Texas State University, Commerce, Texas 75428. Louis S. Kornicker, Department of Invertebrate Zoology, Smithsonian salinity ranged from 9.7%O in February 1959 to 18.2%o Institution, Washington, DC. 20560. in September 1959. In Redfish Bay the lowest salinity 1 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY 28*30' 27*30' — 27*00" 27»IO' FIGURE 1.—Locality map. NUMBER 24 COPANO BAY REDFISH BAY LAGUNA MADRE .-•*•--. A 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 FIGURE 2.—Salinity-temperature diagrams (by months) for Copano Bay (Station 15), Redfish Bay (Station 1; January missing), and the Laguna Madre (Station 12). recorded was 15.9%o in December 1959 and the highest fine sandy silt; the percentage of shells over 2<f>, not in- was 37.7%o in July 1959. In the Upper Laguna Madre, cluded in the above descriptive terms, ranged from 7 salinities ranged from 22.7%o in February 1959 to to 44. At stations in the Upper Laguna Madre, the 50%o in August and September 1959. Salinities ob- substrate consisted of very fine sandy mud, clayey fine tained during collections are in Tables 9-19. sand, silty fine to very fine sand, and clayey fine sand According to the salinity classification adopted by a with oolite; percent of shells over 2<f> ranged from 3 to symposium on the classification of brackish waters held 40. Sediment characteristics are presented in Table 1. in Venice in 1958 (see Pubblicazioni Stazione Zoo- During the operation of picking ostracods from wet logica di Napoli, 1964, vol. 33 suppl., 611), Copano sediment samples, it was observed that all samples from Bay is classified as Metahaline, Redfish Bay as Poly- Redfish Bay, as well as samples from Stations 11-14 in haline-Euhaline, and the Upper Laguna Madre as the Upper Laguna Madre and from Station 16 over an Polyhaline-hyperhaline. oyster reef in Copano Bay, contained abundant fecal TEMPERATURE.—Temperatures in Copano Bay, pellets. Redfish Bay, and the Laguna Madre are quite similar. MARINE PLANTS.—Bottom grasses and algae are The temperature recorded during the present study known to form the substrate for some ostracod species ranged from 10.5°C. in Copano Bay in November 1959 as well as being a direct or indirect food source. Grasses to 33.5°C. in Redfish Bay in August 1959. Tempera- and algae are an important part of the biota of Redfish tures obtained during collections are in Tables 9-19. Bay and the northern part of the Upper Laguna SUBSTRATE.—Stations in Copano Bay were on a gray Madre but are less important in Copano Bay and the to black mud, an oyster reef, and intertidal fine sand. southern part of the Upper Laguna Madre (Table 2). In Redfish Bay, stations were on fine to very fine sandy Odum and Hoskins (1958) reported that in Redfish clay, very fine sandy mud, muddy fine sand, and very Bay and the northern part of the Upper Laguna Madre, SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY TABLE 1.—Characteristics of sediments at sampling stations % over 2<j> % sand % silt % clay Mean size 2 Standard 3 3 Area Station (shells) microns deviation Sorting Description (remainder of sediment)1 0 Redfish Bay 1 7 46 15 39 6.0 16 4.60 extra poor fine to very fine sandy clay 2 47 19 19 62 4.2 54 6.30 extra poor fine to very fine sandy clay 3 33 10 49 41 4.9 34 5.70 extra poor very fine sandy mud 4 29 15 45 40 5.0 31 5.60 extra poor very fine sandy mud 5 22 15 45 40 5.5 22 6.