Phytoplankton in a temperate-zone salt marsh: Net production and exchanges with coastal waters

Phytoplankton production and associated variables were measured in Flax Pond, a 52 ha salt marsh on the north shore of Long Island, New York, from July 1972 to October 1973. Measurements made up to five times per day, once per week, yielded a mean annual net primary production, determined by the ¹⁴C technique, of 20.5 mg C/m³/h; daily means were as high as 60.0 mg C/m³/h. However, when productivity was calculated for the entire marsh ecosystem, the shallow water in the salt marsh produced only 11.7 g C/m² of marsh/year. There was a net flux of phytoplankton from the coastal waters into the marsh; during the summer up to 0.2 g chlorophy 11/m² of marsh was carried in with the tides daily and remained in the marsh. Analysis of the productivity data, as well as variables associated with productivity (pH, standing crop, nutrients, extinction coefficient), indicated that the aquatic portion of the marsh behaved more as a net consumer rather than a net producer of phytoplankton.Research carried out at Brookhaven National Laboratory, supported by the U.S. Atomic Energy Commission and the National Science Foundation under Grant No. AG-375.     

Natural variability in distribution of an intertidal population of Macoma balthica subject to potential oil pollution at Port Valdez,Alaska

Natural variability in the abundance of an intertidal population of the lamellibranch Macoma balthica (Linnaeus, 1758) was measured during 1971 and 1972 in a study area near the proposed oil storage and tankship loading facility at the southern terminus of the Trans-Alaska pipeline in Port Valdez, Alaska. M. balthica were divided for analysis into a large and a small size category. Small temporal changes in population densities throughout the entire study area were detected for both size categories over several of the 7 sampling times of the 2-year period. Large and persistent differences in density were found among elevation contour intervals for either size category; however, variations in the density profiles on elevation occurred among sampling times. Large M. balthica became more equitably distributed and the small category less equitably distributed among elevation contours over the 2-year period. Densities of both size categories were more stable at the higher elevations of the study site. Large M. balthica were more homogeneously distributed along a given elevation contour interval than the small category. Mobility and time available to redistribute at a horizontal location would explain the more homogeneous distribution of large M. balthica if competition for food resources exists.     

Etude des variations du poids sec et de la constitution chimique élémentaire de Tisbe holothuriae (Copepoda: Harpacticoïda) élevé sur différents régimes artificiels

Dry weight and body composition of C, H and N were investigated in male and female Tisbe holothuriae Humes fed 7 artificial compound diets and a living algal diet (Nannochloris sp.) over the whole biological cycle. No correlation was found between the respective proportion of C, H and N in the food and in the copepod body. Food quality had a significant effect on dry weight. Carbon content varied between 35.35 and 42.32% of body dry weight in females, and between 25.10 and 26.84% in males. Nitrogen values were 9.11 to 10.00% and 6.79 to 6.99%, respectively, varying with different diets. The C:N ratio varied between 3.74 and 4.28 in females and between 3.70 and 3.87 in males. Some diets had a significant effect on this ratio. In some experiments, three different temperatures were tested using the same diet. Body dry weight was inversely correlated with temperature, but no clear relation appeared between C:N and temperature. C:N variations were directly related to C concentration and seemed independent of N concentration. It is suggested that C variations correspond to different levels in lipid content under different trophic conditions. The relation between elementary chemical composition and fecundity in T. holothuriae fed different diets is discussed.     

Observations of heterotrophic activity on photoassimilated organic matter

The natural heterotrophic utilization of released and particulate photoassimilated compounds by natural phytoplankton populations was followed during the summer of 1975 in the Kiel Bight (Western Baltic Sea). Phytoplankton exudates (2 to 21% of primary production) seem to represent an important substrate for heterotrophic bacteria: uptake rates between 8 and 17,5%/h were observed. Samples incubated with antibiotics indicated that the heterotrophic uptake of phytoplankton exudates during photosynthesis could lead to underestimation of the release rate. Production of 14_{CO 2}was used as an estimate of the mineralization of particulate photoassimilated matter. The mineralization rates measured were in the range of 6 to 20% after 20 h. In order to confirm the quantitative measurements, micro-autoradiographic examinations of the samples were performed.     

Evidence for microfloral succession on allochthonous plant litter in Apalachicola Bay,Florida, USA

Changes in hydrolytic, respiratory,catabolic and lipid biosynthetic activities depend at least in part on successional changes in the microfloral populations of allochthonous plant litter incubated in a semi-tropical estuary. Initial colonization is by populations which have a high content of muramic acid relative to the adenosine triphosphate (ATP) and which are progressively displaced by a microflora with a lower ratio of muramic acid to ATP. Scanning electron micrography of the plant-litter microflora shows a succession of forms, with an initial bacterial colonization and its progressive displacement by more complex forms. Estimates of the microbial mass and the rates of phospholipid synthesis suggest that the detrital microflora has a relatively slow growth rate compared to its growth potential.     

An annual carbon budget for the kelp Laminaria longicruris

Oxygen evolution and uptake by whole thalli of the large marine alga Laminaria longicruris de la Pylaie were measured for 24 h, once every 2 weeks for a year, using large chambers to incubate the plants on the sea bed. Diel rates of photosynthesis and respiration were calculated from these measurements and continuous light measurements were used to extrapolate the data between observation dates. The resulting estimates were combined with measurements of growth and carbon content to give an annual carbon budget for a typical mature plant. Annual net assimilation was 6.8 mgC per cm² of frond surface (71 cal cm^-2). Approximately 45% of this appeared in the production of new frond tissue, and a further 12% was accounted for by storage of carbon in mature frond tissue. About 8% was needed for stipe growth, and the remaining 35% was assumed to be lost as dissolved organic carbon. Diel net photosynthetic rates reached a maximum in June and July and were negative only in November, indicating an ability to produce a photosynthetic surplus throughout winter. In early winter the plants drew on stored reserves to supplement photosynthesis in providing carbon for growth, but from January onwards photosynthesis provided more than enough carbon for growth.     

Toxicity evaluation of a complex metal mixture to the softshell clam Mya arenaria

Adults of the softshell clam Mya arenaria were continuously subjected to a flowing raw seawater solution containing a mixture of salts of manganese, zinc, lead, nickel, copper, and cadmium. Final calculated concentrations, in g l^-1, of the toxicant solution were 7200 Mn, 2500 Zn, 70 Pb, 50 Ni, 50 Cu and 1 Cd; these concentrations approximated highest measured levels within surficial interstitial sediment waters from mid-Narragansett Bay, Rhode Island. M. arenaria were also subjected to a 20% solution, i.e., 1440 Mn, 500 Zn, 14 Pb, 10 Ni, 10 Cu, and 0.2 g l^-1 Cd. One study was conducted for 112 days in winter at 0° to 10°C and another for 16 days in summer at 16° to 22°C. In the winter study, all clams exposed to a 100% solution died between the 4th and 10th week; soft parts of survivors at 6 weeks contained about 19 times more Pb, 15 x more Zn, 12 x more Cu, 10 x more Mn, 3 x more Ni and 0.1 x more Cd than controls; relatively minor changes in whole body elemental content of Ca, Cr, Fe, K, Mg, Na, Sr, and V were observed. Clams exposed to a 20% solution during winter survived the 112 day study; at that time these contained about 5 x more Cu, 4 x more Mn, 3 x more Zn and about 2 x more Pb than controls; comparatively minor changes were observed in other elements examined. In the summer study, all M. arenaria subjected to the 100% solution died between 6 and 14 days; survivors from this group at 7 days contained about 25 x more Pb, 13 x more Cu, 11 x more Zn, 7 x more Mn, and 3 x more Ni than controls; other changes in elemental content were not as pronounced. Mortality in the 20% group during summer was slightly higher than controls during the 16 day study; at 14 days survivors from this group contained about 12 x more Mn, 7 x more Pb, 7 x more Zn, 4 x more Cu, and 3 x more Ni than controls. Survival and bioaccumulation patterns were not altered through feeding a supplemental diet of algae. The significance of these findings are discussed in terms of potential environmental perturbations, especially local dredging practices.     

Aufnahme von chlorierten Kohlenwasserstoffen durch Pflanzenoberflächen

Spinach plants were contaminated with hexachlorobenzene (HCB) and 2,2′, 5,5′-tetrachlorobiphenyl (PCB) in the vapor phase and by bentonite aerosol. To characterize the deposition of these substances on contaminated plant leaves, different solvents were used (water,n-hexane, and acetone). The solubility of the substances was shown to depend on the mode of application. Release studies indicate that the concentration of the tested chemicals decreases to 5% for HCB and to 27%, respectively 49%, for PCB after a period of 4 days at 23°C for different modes of contamination.     

Leitfaden zur Beurteilung von Boden-Kontaminationen

This article investigates to which extent presently obtainable data can sufficiently evaluate soil contamination. Relevant data pertaining to this question are tabulated. Risk assessments are made for particular contaminations on the basis of the compiled data. The proposed procedure is a guideline for the practical evaluation of cases of soil contamination by organic pollutants. Analyses are made for soil compartments, including risk assessments for groundwater. Evaluations are directed at protection of resources and plant growth. The project aims at facilitating the recognition of research deficiencies and at suggesting appropriate measures.