Respiratory physiology in summer diapause embryos of the neustonic copepodAnomalocera patersoni

The respiratory physiology of summer diapausing eggs of the neustonic copepodAnomalocera patersoni, maintained under constant temperature (13 °C) and light (12 h light:12 h dark) conditions, was characterized by a bell-shaped curve, with low O₂ uptake levels at the beginning of dormancy. This was followed by a steady rise in O₂ consumption with maximum levels of 0.002 l O₂ embryo^–1 h^–1 70 d after spawning. A slow diminution in O₂ uptake then occurred until Day 150 when minimum values of 0.0003 l O₂ embryo^–1 h^–1 were recorded, coinciding with the hatching of the first embryos. Embryos continued to hatch asynchronously up to 360 d from the moment of egg laying. When eggs were subjected to 20 °C, the respiratory activity was almost three times higher than at 13 °C, even though both respiratory curves were similar. The elevated metabolism in eggs kept at 20 °C led to death of the embryos possibly due to a total depletion of metabolic reserves. ATP content also differed at the two temperatures. Diapause eggs kept at 20 °C showed no rapid rise in ATP content as opposed to those kept at 13 °C. The results of temperature shock experiments, in which eggs were first kept at winter temperatures for several weeks, after which the temperature was raised to 20 °C for another number of weeks prior to a second period of chilling at 13 °C, showed that as long as embryos were kept at 20 °C no hatching occurred. By contrast, hatching was observed after 10 d following the resumption of winter temperatures, suggesting that low environmental temperatures are an essential prerequisite for hatching of these eggs. The type of diapause inA. patersoni differs considerably from the one described in insects and in another neustonic copepod,Pontella mediterrana. In this case, there is a U-shaped respiratory curve with greatest O₂ consumption prior to the onset or upon breaking of diapause. Differences in the two types of diapause seem to involve not only differences in O₂ consumption levels but also in the sequence of metabolic changes with time and the metabolic requirements during sommer and winter dormancy.     

The influence of particle surface characteristics on pollutant metal uptake by cells

The phosphatic mineral, hydroxyapatite, and two ion exchange resins have been used as artificial sediment particles. The surface properties of these materials have been studied using the Langmuir adsorption isotherm to calculate the binding capacity (B(max)) and the adsorption constant (K(L)) for zinc and cadmium ions. Mussels (Mytilus edulis) were fed on the particles and their digestive glands were subsequently removed and subjected to cell fractionation. The supernatant fraction was used to determine cytosol metal levels as a measure of the materials absorbed from the ingested particles. The level of cytosol zinc and cadmium was correlated with the K(L) values of the artificial sediments. It is suggested that phagocytosis of sediment particles plays an important part in transferring pollutants into benthic organisms and that the efficiency of this process is related to the adsorption coefficient of the particle surfaces.     

The fate of endosulfan in aquatic ecosystems

Endosulfan, one of the major pesticides used in cotton-growing, is of environmental concern because of its toxicity to fish and its apparent persistence in the environment. This study examines the distribution and degradation pathways for endosulfan in an aquatic system and the processes by which it is removed. In the alkaline waters of the cotton region, hydrolysis is the dominant degradation process. By this mechanism alone, the expected half-lives for the alpha- and beta-endosulfan isomers were found to be 3.6 days and 1.7 days, respectively. Partitioning studies showed, however, that the major proportion of endosulfan would associate with the sediments (log Koc(alpha) 3.6 and log Koc(beta) 4.3). Field studies confirmed the presence of high concentrations in sediments. Microcosm experiments showed that loss of endosulfan was slower than predicted from hydrolysis rates. Models are presented to explain how desorption from sediment limits the loss of endosulfan from a system.     

Petroleum and hazardous chemical spills in Newark Bay, New Jersey, USA from 1982 to 1991

Newark Bay, New Jersey, is particularly vulnerable to ecological damage from petroleum and chemical spills, as a result of the enclosed nature and shallow depth of the bay, the high frequency of shipping traffic, and the numerous chemical and petroleum transfer terminals located alongs its shores. To evaluate the potential impacts to the natural resources of this coastal estuarine ecosystem, chemical and petroleum accidents reported to the US Coast Guard (USCG) between 1982 and 1991 were compiled to determine the frequency and volume of these incidents in Newark Bay and in each of its major tributaries. Records obtained from the USCG National Response Center's computerized database indicated that more than 1453 accidental incidents, resulting in the release of more than 18 million US gallons of hazardous materials and petroleum products, occurred throughout Newark Bay during this period of time. The bulk of the materials released to the aquatic environment consisted of petroleum products, specifically No. 6 Fuel Oil (103 spills, 12 829 272 US gal) and gasoline (207 spills, 48 816 US gal). The majority of the reported incidents occurred in the Arthur Kill and its tributaries, as well as in the Kill Van Kull and the Passaic River. The results of this study indicated that the accidental discharge of petroleum and hazardous chemicals represents a significant source of chemical pollution in Newark Bay. Based on the frequency of spills and the volume of materials released to the aquatic environment, it is likely that these events are having a deleterious effect on the Newark Bay ecosystem.     

Plankton inhabiting the surface layer of the southern and southwestern lagoon of New Caledonia

In the southern and southwestern coral reef lagoon of New Caledonia and the adjacent oceanic waters, 42 neuston samples were collected from the upper surface layer (0 to 10 cm) along nine transects from the coast to the coral barrier reef and the open ocean immediately beyond the reef, in March and April 1979. There was a progressive numerical decrease in zooplankton densities from the coast to the reef and from the reef to the open sea. Generally, 80 to 95% of the surface plankton consisted of holoplankton and 5 to 20% of meroplankton. Zooplankton was very abundant in littoral bays with a marked eutrophication. In a few samples collected in very shallow waters close to coral patches, cladocerans were numerous and constituted up to 75% of the total plankton, whilst in other samples collected above greater depths, copepods made up 60 to 85% of the total plankton. In the coral reef lagoon of south and southwest New Caledonia, typically hyponeustonic copepods (pontellids) often comprised 5% of the total copepod populations.     

Sediment-rejection efficiency of 22 species of Australian scleractinian corals

Sediment-rejection rates of 22 Australian midshelf coral species were studied in situ between March and July 1988 at Lizard Island, Great Barrier Reef. Rejection rates of non-branching species were positively correlated with calice size and were faster for fine (63 to 250 m) than for coarse (500 to 1000 m) sediment at influxes of 200 mg/cm². Increasing water turbulence was a more important influence on rejection rates for some species than for others. Most replicates of most species cleared all sediment in 2 d. Of those that did not, some Favia stelligera and Leptoria phrygia showed partial tissue death within 48 h, and Gardineroseris planulata showed partial tissue death within 6 d. Montipora aequituberculata, Porites lobata and P. lutea tolerated sediment for at least 6 d, and exhibited extensive tissue bleaching, but these tissues recovered after sediment removal. Sediment-rejection efficiency and sediment tolerance are not directly related, and wide interspecific differences may occur in both. These findings are correlated with differences in sediment-rejection mechanisms and with ecological distributions on the reef.     

Age determination and growth of the bonnethead shark Sphyrna tiburo: a comparison of two populations

From July 1982 to December 1986, a study of the age and growth of the bonnethead shark Sphyrna tiburo was conducted in Tampa and Florida Bays, Florida, USA. Tetracycline-injected sharks held in captivity and, to a lesser extent, tagged, released and recaptured, were utilized for validating the annual nature of the rings (herein defined as the narrow, translucent regions) appearing on vertebral centra. The technique was validated for all age groups (0 to 6+yr) included in the study. Marginal increment analysis likewise suggested annual ring formation. The rings formed during the winter, when water temperatures were lowest. Using the vertebral ring aging-technique, von Bertalanffy growth curves for males and females from both tampa and Florida Bays were constructed. Growth of sharks born and held in captivity demonstrated that the male and female growth curves diverge after 1 yr and that mean sizes at age are statistically distinct after 2 yr. In both populations, females grew to larger sizes tha males and apparently are longer-lived. Reproductively mature females from Tampa Bay were significantly larger than those from Florida Bay.     

Sulphur status in some Swedish podzols as influenced by acidic deposition and extractable organic carbon

To evaluate the changes in sulphur pools in response to acidic deposition, two studies were made-one in southwest Sweden where podzolic B horizons originally sampled in 1951 were resampled in 1989. At the Norrliden site, northern Sweden, sulphur pools in control plots were compared to plots that had been subjected to H(2)SO(4) application between 1971 and 1976. The results show that in southwest Sweden neither organic S nor extractable SO(4)(2-) increased significantly over the 38-year period, despite a decreasing pH and a high S deposition. At Norrliden, about 37% of the applied S was still remaining in the upper and central parts of the Bs horizon, most of which was inorganic sulphate. These contrasting results are explained by intrinsic differences in the soil organic carbon status between the sites-in southwest Sweden, organic carbon concentrations were high which inhibited SO(4)(2-) adsorption. Low organic carbon concentrations and high extractable Fe/Al concentrations promoted SO(4)(2-) adsorption and caused a low subsequent SO(4)(2-) desorption rate at the Norrliden site. The results suggest that sulphate adsorption may be an important mechanism which delays the response in soil chemistry to H(2)SO(4) deposition, provided that soil organic carbon concentrations are low. Organic S retention was not shown to be an important S retention mechanism in any of the sites studied.     

Proximate and elemental composition and energy content of mesopelagic crustaceans from the Eastern Gulf of Mexico

The proximate and elemental chemical compositions of 25 species of pelagic decapod and mysid crustaceans collected from the eastern Gulf of Mexico (27°N; 86°W, 1984 to 1989) was examined. Water level ranged from 63 to 95% and increased slightly with species' increased depth of occurrence. Protein levels were generally high (1.5 to 18.3% wet wt, WW; 27.6 to 62.4% ash-free dry wt, AFDW) and comprised the primary organic component in the majority of species. Protein, both as % WW and % AFDW, decreased with increased depth of occurrence. In contrast to protein, lipid levels were low (0.5 to 8.9% WW; 5.7 to 60.9% AFDW), and increased with increased depth of occurrence. Carbon and nitrogen best mirrored measured lipid and protein levels when considered as non-protein carbon and non-chitin nitrogen, respectively. C:N ratios increased with increased depth, consistent with changes in protein and lipid with depth. Because of their compositional attributes, resident Gulf of Mexico species have a low total wet weight energy content relative to species from more productive regions. Energy content showed no significant trend with depth. Vertical migration patterns were distinctly different between shallow-and deep-living gulf species and these differences were largely responsible for the relationships observed between composition and depth. In migrating species, the protein and nitrogen content were higher, the lipid and carbon contents and C:N ratio lower, than in non-migrating species. Three deep-living species of the genus Acanthephyra were found to be compositionally atypical, resembling shallow, migrating types rather than other deep-living, non-migratory species.     

Threshold and dose response estimation using the “filter model”

The “filter model” has been developed to explain the biologic effects of radiation and chemicals. We have examined nearly 300 sets of dose response data, of which 50 are presented here. Responses (induced by radiation and chemicals) which have been examined include in vitro survival studies on animal and plant tissues, induction of cellular aberrations and time to tumor or death. Similar data from in vivo studies has also been examined. All of the data appear to fit the model R = a lnD + b(lnD)² + c, where R is the response, a and b are parameters fitted by regression to a particular set of data, and c is the response at zero (or lowest) dose. By writing this model in exponential form, it can be seen that the response R results from multistage filtering (by net amounts a and b) of the initial dose, D. The threshold is obtained from this model as the point, $\text{D}\text{?}{}_{\mathrm{T}}$, at which the second derivative becomes zero. This is given by $\text{D}\text{?}{}_{\mathrm{T}}\text{=}\text{exp}\text{(1 ?}\text{a}\text{2b}\text{)}$ when a and b are oppositelt signed.