Zooplankton studies in the Cox Bay, Texas area, before and during early operation of an electric power plant

Abstract

Zooplankton investigations were conducted from November 1969 through September 1971 in the Cox Bay area, part of the Matagorda 3ay System on the central Gulf coast of Texas. Four hundred seventy-- four plankton samples were collected with a Clark-Bumpus sampler (#20 net, repeated oblique tows) approximately every three weeks at 21 stations during an 18-month "before" period and a 5-- month "after" period (May 1971 to September 1971, through initial simmer operation of the Ennis S. Joslin Generating Station, Point Comfort, Texas). During the entire study period, observations were made in the study area on tides, winds, surface water movements, percent composition and distribution of sediments, water temperature, thermal plume movements, precipitation, salinity, dissolved oxygen, pH, turbidity, and chlorophyll a levels. At least 165 species were noted. Arthropods dominated the list (68, including 32 copepods and 12 decapods), followed by annelids (21), coelenterates (19), chordates (13) and protozoans (10). The spatial and seasonal distribution and abundances for most species are discussed in detail, with emphasis on the Cope-- poda. Relatively few species or groups contributed the largest segment of the zooplankton community, with euryhaline forms dominating. Copepods (nauplii, copepodids and adults) constituted the most important group, accounting for 56.3% of total standing crop. Other groups exceeding 1% of the total population were rotifers (9.5%), tintinnids (8.7%), mollusc larvae (7.1%), barnacle nauplii (6.9%), invertebrate eggs (5.0%) and annelid larvae (2.4%). Holoplankton comprised 82% of total zooplankton; the meroplankton forms had their highest percent occurrences during late winter and spring..