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A recurring pink discoloration found at the bottom of polyethylene buckets containing embryos of hard clams (Mercenaria mercenaria) is produced by a red-pigmented pseudomonad. The pink discoloration itself is not a problem, but the number of bacterial cells present is cause for concern. This study showed that at concentrations below 103 cells per milliliter of culture of clam embryos the bacterium could produce the discoloration without being detrimental to the clams. Above this concentration, however, either embryonic development decreased or mortality occurred. Chloramphenicol and neomycin were used effectively in preventing the growth of the pigment-producing bacterium and the concomitant adverse effects on clam embryos.

Six intertidal populations ofTagelus plebeius, the stout razor clam, and associated macroinvertebrates were sampled in the North Inlet estuary, near Georgetown, South Carolina.T. plebeius inhabited only stable sediments composed of greater than 2.0 % silts and clays and which were covered by a visible surface film of benthic microalgae. Gut contents, gill morphology, and behavior all indicated that this clam functioned as a suspension feeder obtaining its nutrition by filtering suspended particles from the water column. Maintenance of the siphon tubes and burrows was important to the survival of this organism.T. plebeius was quantitatively an important member of the infuana within its habitat, composing 93.0% of the biomass, but only 3.2% of the total number of individuals. Sediment stability, in addition to affecting the distribution ofT. plebeius, also had a significant role in determining the structure of invertebrate communities inhabiting the intertidal sandbars sampled. The stable muddy-sand sediments of lagoon areas supported a more diverse faunal assemblage than did the less stable sandy sediments of fringe areas of the same sandbar.

Although scattered individuals ofJuncus roemerianus Scheele may be found northward in New Jersey, Long Island, New York, Connecticut and southward along the Laguna Madre in Texas, Mexico and on the Caribbean islands, the species is most prevalent along the south Atlantic and Gulf coasts of the eastern United States. Here there are approximately 3,174,333 hectares of salt marsh of which 72.9% occur on the Gulf coast and 27.1% on the Atlantic coast.Juncus roemerianus dominates 20.7% of the marsh in the south Atlantic states and 7.3% of the Gulf coast marshes, but covers more marsh area on the Gulf coast (170,067 hectares) than on the Atlantic coast (149,316 hectares). Thus, there are approximately 320,000 hectares of salt marsh dominated byJ. roemerianus in North America.

Schools of Atlantic menhaden, Brevoortia tyrannus, have measurable effects upon the estuarine waters of Narragansett Bay, Rhode Island by their feeding, respiration, and excretion. The concentrations of phytoplankton and oxygen decreased and ammonia increased within the immediate vicinity of schools.

Rates of photosynthesis were used to evaluate the response of phytoplankton when passed through the cooling system of a power generating facility. Photosynthesis was measured as the uptake of carbon. A factorial design permitted evaluation of heat input, total effect of passage, and degree of recovery. Six experiments measured response at a fixed time of day and at various times in a daily cycle. An increase in temperature of approximately 8.0 C stimulated photosynthesis when natural water tempratures were 16 C or cooler and inhibited photosynthesis when natural water temperatures were 20 C or warmer. Passage through the cooling system resulted in further inhibition when the water was warm and nullified thermal stimulation when the water was cool. No recovery was observed within a four hour period following passage. Photosynthesis in cooled effluent water was either unaffected or actually suppressed. The existence of daily synchrony in the algae was shown by a daily maximum of thermal stimulation at 0900. The rhythm is considered inherent and only amplified by warming.

This paper deals with studies on temperature, salinity, turbidity, phosphate, silicate, nitrate, chlorophylla and zooplankton in the Patuxent River Estuary for a 20-month period from July 1963 to February 1965. Temperatures ranged from less than 1 C to higher than 30 C; salinities ranged from 0.1 to 19.2% and showed higher values than earlier reported investigations. Turbidities ranged from 0 to 113 ppm and decreased downstream. Phosphates ranged from 0 to 2.1ug at/L and showed no marked seasonal or distributional patterns. Silicates decreased slightly downstream from a maximum of 135ug at/L at the uppermost station. Nitrates ranged from 0 to 14.5ug/L with an early spring maximum and highest values occurred at upstream stations. Chlorophylla determinations showed minimal winter and maximal spring and summer values; a spring chlorophylla peak closely followed a spring NO3 maximum. Zooplankton, sampled with a No. 2 net, showed lowest standing crops during summer and early fall (less than 100/m3) and highest during winter and early spring (greater than 7000/m3). By number, copepods comprised 98.1% of total zooplankton (excluding ctenophores and coelenterates). The major components of the zooplankton wereAcartia tonsa, A. clausii, andEurytemora affinis. Eurytemora dominated upriver in lower salinities, andA. tonsa dominated downriver in higher salinities except during March and April, when it was replaced byA. clausii.