Blueback herring (Alosa aestivalis), American shad (Alosa sapidissima), and striped bass (Morone saxatilis) larvae from the Chesapeake Bay region were subjected in the laboratory to time-excess temperature histories typical of those experienced by organisms entrained by power plants with a variety of design and operating criteria. The maximum excess temperature ranged from 7° to 20°C above the base temperature (the average surface water temperature on the spawning grounds); the time of exposure to a maximum excess temperature from 4 to 60 minutes; and the period of cooling to the final temperature from 60 to 300 minutes. An excess temperature of 20°C resulted in virtually total mortality of larvae of all three species. Striped bass larvae were the most tolerant of the, three species and could withstand excess temperatures of up to 10°C with no significant increase in mortality. The response patterns of the other two species were more complicated.
Annual U.K. production of chlorine stands at around 106 tonnes. Less than 1.5% (15,000 tonnes) finds direct application as a biocide, of which 10,000 tonnes (1976 estimate) is used by the C.E.G.B. (England and Wales) for the control of bacterial slimes and marine fouling in power station cooling circuits. This compares with 4000 tonnes used for treating domestic water supplies. Indirect biocidal application via chlorinated hydrocarbon pesticides never exceeded 300 tonnes per annum. It is not standard practice in the U.K. to use chlorine in sewage treatment.
Anilocra acuta (Isopoda: Cymothoidae), previously known from Georgia and from Tampa Bay, Florida, is recorded from the lower Ochlockenee River and from Alligator Harbor, Florida, from Louisiana, and from the lower Hudson River, New York. New hosts areLepisosteus spatula, Bairdiella chrysura, andExox niger.
During the course of faunistic investigations of estuarine Amphipoda in North Carolina (Fox and Bynum, 1975), several undescribed species have been found. Six of these, in the generaGammarus, Maera, Stenothoe, Lembos andMicrodeutopus, are described here.
Historical records indicate that Flax Pond, a smallSpartina alterniflora marsh located on the north shore of Long Island, New York, was opened to marine waters in 1803. This opening is recorded in the sediments by a sharp transition from sedge (brackish or fresh water) peat toSpartina (salt marsh) peat. This dated horizon was used to calculate an average net rate of vertical accretion of 2.5 mm/yr and a maximum net rate of 4.7 mm/yr. These estimates may serve to predict the rate at whichSpartina marshes are able to recover from physical disturbance. *** DIRECT SUPPORT *** A00BY066 00002
This paper contains the first published radiometrically determined contemporary sedimentation rate, a rate characteristic of the past few decades, for any part of the Chesapeake Bay estuarine system. Cores collected from a station in the main body of the Chesapeake Bay off Tilghman Island (38°41′30″N, 76°24′00″W) were analyzed for Pb210, organic carbon, nitrogen, and selected metals. A mean sedimentation rate of between 0.09–0.12 cm/y was inferred from the Pb210 data. The distributions of C and N are typical of many areas of the Bay. The distributions of extractable Ni, Cr, Cu, and Pb increased in the upper 10–15 cm of the core. The increases in metal concentrations over the past century or so may be a result of man’s activities.
Allozyme genetic variation in larvae and adults of the crabsRhithropanopeus harrisii, Sesarma cinereum, andS. reticulatum was investigated. InRhithropanopeus from North Carolina, Maryland, and Maine essentially no geographic variability was detected at 15 allozyme gene loci, all but perhaps one of which was monomorphic in the samples utilized. There was also no life cycle variability in enzyme expression among zoeae, megalopa, and adults other than assay differences. The two species ofSesarma, all collected in North Carolina, also showed no life-cycle variation. Three of 13 loci were polymorphic inS. reticulatum, 0 of 13 inS. cinereum, and 0 or 1 of 15 inR. harrisii.
A simple, inexpensive 2″ Hand Corer has been developed for efficiently sampling most types of shallow water sediments. The corer consists of a Lexan plastic core tube, 1-1/2″-check valve unit, and polyvinyl chloride tube handle.
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.
A simple two-dimensional numerical model has been developed to represent the observed vertical structure of tidal and nontidal currents and tidal elevations along a reach of the lower Potomac River Estuary. The model is based on a linearized longitudinal momentum equation and a laterally averaged continuity equation. It incorporates the effects of a naturally varying channel cross-section through the continuity equation, and a seaward increase in density through the pressure gradient term in the momentum equation. The observed distribution of density in the reach is used to evaluate the horizontal pressure gradient relative to the water surface. The model utilizes a coefficient of vertical eddy viscosity which varies both vertically and longitudinally. With but two adjustable parameters associated with the eddy viscosity, good agreement is obtained between the computed and observed tidal and nontidal currents.
A study of the macrobenthos of the tidal Delaware River between Burlington and Trenton, New Jersey, included measurements of density and biomass for common species. Tubificidae (Limnodrilus) were dominant, comprising over 90% of all organisms taken in the 3-year study period. Density seemed to be a function of water temperature (20–25 C, optimal) and was greatest in late spring and early summer. Other common species were larvalProcladius culiciformis (Chironomidae) andCorbicula manilensis (asiatic clam).Procladius was most abundant in late summer just prior to and during emergence. The asiatic clam was in the process of colonizing the area and growth data have been calculated. Potential relationships between numbers and standing crop of the common organisms with sediment type, and seasonal changes were explored.
While most gymnolaemates are restricted to waters of normal salinity, at least 3–6% are able to penetrate some distance into mixohaline water. Of this group, which includes 9 species of cyclostomes, 35 species of ctenostomes, 55 species of anascan and 21 species of ascophoran cheilostomes, the cyclostomes and the ascophorans are least tolerant of diluted salinities, the ctenostomes and the anascans are most tolerant. Like many other groups of benthic organisms, ectoprocts show a decrease in numbers of species with decreasing salinity. Only 5 species can penetrate into waters of less than 3‰. About 20 species can be considered truly brackish-water organisms, being most abundant in mixohaline waters. Apparently these species possess some means of active osmoregulation, probably at the tissue level.
Recent investigations have shown the pelagic distribution of plastic particles in the ocean to be widespread; and their source and fate have been the subject of considerable discussion in the United States. In the waters of Block Island Sound there is a seasonal fluctuation in their abundance. Their source appears to be Long Island Sound, probably originating from the rivers on the Connecticut Shore. They are transported out to sea by the action of the tidal currents in the upper 10–15 meters of the water column.
