Use of detrital foods and assimilation of nitrogen by coastal detritivores

Two killifish common in east coast U.S.A. salt marshes,Cyprinodon variegatus Lacepede andFundulus heteroclitus Walbaum, differ in their ability to assimilate nitrogen from and grow on detritus.C. variegatus grew on a diet of detritus ofSpartina alterniflora Loisel, whileF. heteroclitus did not. In addition, when the fish were fed¹⁵N-labeledS. alterniflora detritus,¹⁵N:¹⁴N ratios inC. variegatus were higher than were ratios inF. heteroclitus. Therefore, even though both species ingest large amounts of detritus,C. variegatus makes more effective use of this portion of its diet. These dietary differences are corroborated by anatomical differences that suggest thatC. variegatus should make better use of detrital or plant tissues thanF. heteroclitus. In the label experiment, the degree of label in both fish was directly proportional to the degree of label in the food treatments. In previously published experiments designed to compare plant substrate with attached microbes as nitrogen sources for detritivores, %¹⁵N incorporated by a polychaete was also directly proportional to %¹⁵N in the detrital food. Therefore, it is difficult to distinguish between plant substrate and microbes as nitrogen sources for this detritivore.     

Acid mine drainage contaminates groundwater of a Tennessee watershed

Water samples were collected from 18 natural springs within the West Fork of the Obey River watershed. Overton County, Tennessee, to determine if groundwater was adversely affected by runoff from abandoned surface coal mines Six springs were found to be affected severely and deemed unfit as a source of potable water Water quality of the remaining springs was essentially unaffected it appeared that proximity to surface mines, elevation at the outflow, and geology of the surrounding strata determined the quality of the groundwater The unit is jointly supported by Tennessee Technological University, the Tennessee Wildlife Resource Agency, and the US. Fish and Wildlife Service     

Cell parameters of thermally treated anorthite. Al,Si configurations in the average structures of the high temperature calcic plagioclases

Thermal treatments of anorthite carried out at up to 1,547° C show that the unit cell parameter changes as a function of the treatment temperature. The best fit curve found by non-linear least squares analysis is: =91.419-(0.327·10^-6)T ²+(0.199·10^-12)T ⁴-(0.391·10)T ⁶. The results obtained support significant Al,Si disorder (Al0.10, where Al=t ₁(0)-1/3 [t ₁(m)+t ₂(0)+t ₂(m)], Ribbe 1975), in anorthite equilibrated near the melting point and confirm a high temperature series differentiated from the low temperature series for calcic plagioclases in the An₈₅–An₁₀₀ range also. In the plot vs. An-content the high and low temperature curves intersect at An₈₅ composition and progressively diverge in the An₈₅–An₁₀₀ range. The trends of the high and low temperature curves in this range are interpretable on the basis of the degree of Al, Si order in the average structures of calcic plagioclases.     

Changes in current regime and turbidity in response to a freshwater pulse in the eastmain estuary

In September 1984, the freshwater input to the Eastmain River (James Bay, Canada) was increased by a factor of 50 over a 6-d period during a controlled reservoir discharge. Changes to the current, salinity and turbidity regimes were monitored during the peak runoff. Estuarine salinity values fell rapidly with increasing mean flow, as did the amplitude of the semi-diurnal tidal currents. A large increase in bottom shear stress dispersed the settled suspension layer into the water column, raising concentrations of suspended matter in the estuary by a factor of 4 in 3 d. The peak values exceeded 150 mg I^?1. This led to erosion of the river silt deposits, with the export of an estimated 6 × 10⁴ metric tons of sediments. After the reduction of discharge, current values returned to their normal range within a day, whereas upstream salinity intrusion occurred at a slower rate. Horizontal diffusivities of about 100 m² s^?1 were required to match the observed lag.     

Occurrence of juvenile Atlantic sturgeon,Acipenser oxyrhynchus,in the upper tidal Delaware River

Eighty-nine juvenile Atlantic sturgeon,Acipenser oxyrhynchus oxyrhynchus, including 10 recaptures, were collected, tagged and released in the upper tidal Delaware River between July 1981 and December 1984. All were captured in the river channel between Roebling and Trenton, New Jersey, using bottom-set experimental gill nets during daylight hours. The species was present from July through December and collected in increased numbers in the past two years. The fork lengths ranged from 284 to 862 mm (mean±SD = 516 mm±106 mm) and the weights from 140 to 4,250 g (mean±SD = 1,369 g±815 g). Ten juvenile Atlantic sturgeon were recaptured between September 1983 and December 1984 and were at large from one to 418 d. Recapture data suggest that these sturgeon utilize this area annually from July through December, possibly as a nursery. Juvenile Atlantic sturgeon appear to utilize the upper tidal portion of the Delaware River for a much longer period of time and at lower temperatures than in other river systems.     

Seasonal control of the Saint-Lawrence maximum turbidity zone by tidal-flat sedimentation

The core of the turbidity maximum zone in the Saint-Lawrence Estuary is located in the North Channel and oscillates in front of the large (3×10⁶ m²) intertidal flats and marshes of Cap Tourmente. It is shown that seasonal fluctuations in the intensity and the position of this core are mainly determined by suspended sediment exchanges between the channel and the marshes. Fine sediments, most of them found 20 km downstream in the channel off Cap Maillard in late winter and early spring, are advected upstream over the flats during the summer months by the tide. The deposition, favored by marsh plant growth, reaches 5×10⁵ metric tons in three months. A period of intense erosion, at a mean rate of 4,500 metric tons per tide, coincides with the destruction of the plant cover by migratory geese. The material removed fills up the Chenal de l’Île d’Orléans upstream and is flushed back into the water column during the next spring freshette. This rotating seasonal sediment circulation, although very localized, exerts a major influence on the distribution and storage time of suspended particles in the upper estuary.     

Occurrence and distribution of shortnose sturgeon,Acipenser brevirostrum,in the upper tidal Delaware River

Sampling in the upper tidal Delaware River between Trenton, New Jersey, and Philadelphia, Pennsylvania, from July 1981 through December 1984 demonstrated the existence of a significant population of shortnose sturgeon. The sturgeon aggregate in the river channel during daylight hours, especially in the area between Trenton and Florence, New Jersey (river km 211.8 to 198.8). Occurrence in the river downstream of Florence appears to be restricted by poor water quality during summer months. Sturgeon were present in the study area throughout the year, but largest numbers were collected from May though November. No spawning was observed during this study, but presence of males with milt suggests that spawning possibly occurs in the Trenton area. Preliminary population estimates (Peterson, Schnabel and Seber-Jolly) indicate an adult population of approximately 6,000–14,000 shortnose sturgeon occupying the upper tidal Delaware River.