Influence of light on algal symbionts of the deep water coral Leptoseris fragilis

Photoadaptations of zooxanthellae living within the deep water coral Leptoseris fragilis taken from the Gulf of Aqaba (Red Sea) were studied. Specimens-collected in summer 1988 between 110 and 120 m depth —were transplanted to 70 and 160 m. At each depth individuals were exposed in their natural growth position (oral side facing the surface) or in a reverse growth position (oral side facing the bottom). After 1 yr of exposure the corals were collected and the zooxanthellae were isolated. As a function of the availability of light with depth and growth position several algal parameters showed changes which are related to photoadaptations. The relatively low density of zooxanthellae of 0.15x10⁶ cellsxcm^-2 at a natural growth depth of 116 m decreased to 0.0034x10⁶ cellsxcm^-2 (2%) at 160 m in specimens growing with a natural orientation. In corals with a downward-facing oral surface at the same depth (160 m) only degenerated algae could be observed. With respect to depth dependence the volume of the algae decreased from 728 m³ at 116 m to 406 m³ at a depth of 160 m and the content of pigments increased. The augmentation of peridinin per cell was low (two times at 160 m compared to 116 m). Chlorophyll a and in particular chlorophyll c ₂ concentrations per cell were enhanced. Compared to natural amounts at 116 m, chl a was five times and chl c ₂ eight times higher at 160 m. At all depths the chl c ₂ content per cell was higher than for chl a. The formation of chl a/chl c ₂ complexes as light harvestor is discussed. Light harvesting, with chl c ₂ prevailing may be explained as a special type of chromatic adaptation of L. fragilis in a double sense: (1) in the habitat light short wavelengths predominate. This light can be directly absorbed with pigments such as chl a and chl c ₂. (2) Host pigments absorb visible violet light and transform these wavelengths, less suitable for photosynthesis, into longer ones by means of autofluorescence. The emitted longer wavelengths fit the absorption maxima of the algal pigments. Thus the host supports photosynthesis of his symbionts. Corals exposed at 160 m depth with a downward facing oral surface were alive after 1 yr and the host wavelength transforming pigment system was still present, but zooxanthellae were absent or degenerated. The light field at 160 m seems therefore to be critical: the combined photoadaptations of host and symbionts, allowing photosynthesis under barren light conditions, seem to be exhausted. In L. fragilis the photoadaptive strategies of host and symbionts cooperate harmoniously. In addition, the adaptations are interlocked with the particular light situation of the habitat with respect to light quantity and quality. The cooperation of physical and organismic parameters examplifies how evolution and, in particular, coevolution has led to optimal fitness.     

Flow rate and particle concentration within the house of the pelagic tunicate Oikopleura vanhoeffeni

The food-concentrating filter within the house of Oikopleura vanhoeffeni Lohmann consists of three layers, upper and lower fine-mesh layers and an intermediate coarse-mesh layer. The filter is a natural analogue of man-made tangential, or cross-flow, filters that are used to concentrate fine particulate and colloidal material by the exclusion of water. Flow analysis using video microscopy of O. vanhoeffeni, collected in 1989 and 1990 at Logy Bay, insular Newfoundland, indicates concentration of particles of 74 to 1089 times that of ambient seawater ( ,n=23), for individuals 1.8 to 5.4 mm long. The smallest individuals had the highest concentration factors. Flow through the house is predominately affected by viscous forces and values of Reynolds numbers are 1. Flow rates through the house of O. vanhoeffeni indicate a maximum filtration capacity of ca. 1.4 to 26 liters d^-1 and clearance rates (assuming ca. 50% of the time is spent not actively pumping) of 0.7 to 13 liters d^-1, depending on body size. The estimated thickness of the boundary layer around individual fibers of the food-concentrating filter is 0.08 m, which is less than the pore width. The estimated concentration factors suggest that colloidal and fine particulate material may aggregate into larger particles within the food-concentrating filter and food tube during feeding.     

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.     

In situ observations of foraging,feeding, and escape behavior in three orders of oceanic ctenophores: Lobata,Cestida, and Beroida

The foraging, feeding, and escape behaviors of members of four genera of oceanic ctenophores were studied by direct observation in the field during the summer of 1987 (7 July to 7 September) on R. V. Oceanus Cruise 191 to the Northern Sargasso and Slope water, in an area bounded by 34° to 39°N and 67° and 74°W. Patterns of water movement around these ctenophores were studied using fluorescein dye. Bolinopsis infundibulum forages vertically, capturing prey with mucus-covered oral lobes. Species of Ocyropsis forage horizontally and produce a reduced wake, due to the extreme compression of the body and the aboral location of the ctene rows. Prey are trapped by the muscular oral lobes and ingested by the prehensile mouth. In both genera, the auricles are held rigidly, and apparently are used both to reduce the pressure wave as they forage and to startle prey onto the surfaces of the oral lobes. Cestum veneris also forages horizontally, but continually reverses direction. Prey startled by the turbulent wake produced in the previous pass are captured by tentilla that stream over the sides of the body. All three species of Beroe studied swim in a spiral while foraging and produce similar wakes. Prey are ingested by the negative pressure produced by the rapid expansion of the mouth, and with the macrocilia that line the oral portion of the stomodaeum. The escape behavior of species of Bolinopsis, Ocyropsis, and Cestum appears to function primarily to elude nonvisual predators such as Beroe spp. Species of Beroe bend and swim rapidly during the escape response, and will turn themselves inside-out when repeatedly stimulated. The types of prey captured depend in part on an interplay of foraging and feeding mechanisms.     

Minimal predation upon meiofauna by endobenthic macrofauna in the Exe Estuary,south west England

Field manipulation experiments were performed in the Exe Estuary, south west England, in October 1988, to investigate the importance of the meiofaunamacroinfauna trophic link in benthic trophodynamics. Four hypothetically meiofauna-predacious endobenthic macrofauna species were selected for manipulation using the criteria of high abundance and different modes of feeding: Cerastoderma edule (filter-feeder), Nereis diversicolor (omnivorous scavenger), Ophelia bicornis (sand-ingester), Scrobicularia plana (deposit-feeder). Enclosures constructed from plastic tubing, 63 m nylon monofilament mesh and galvanized steel were deployed, containing adult members of these taxa at densities raised to approximately four times that of the surrounding sediment. The experiments ran for 12 tidal cycles. Differences in phyletic meiofaunal abundance between treatment and control enclosures at the termination of the experiment were assessed using both uni- and multivariate dataanalysis techniques. Only two univariate significant differences (p<0.05) existed for the N. diversicolor treatment and two for the S. plana treatment. Annelida, Turbellaria and copepod nauplii were the only meiofauna taxa affected. No univariate significant differences were recorded for either the C. edule or O. bicornis treatments. Multidimensional scaling ordination of the data revealed no consistent changes in community composition between treatments and controls. It is concluded that the experiments provide evidence of minimal predation by macroinfauna upon meiofauna.     

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.     

Scavenging of atmospheric formaldehyde by wet precipitation

Despite the great importance that formaldehyde has in atmospheric photochemistry, few studies have been reported on rain water. In this paper, concentrations of HCHO in rain fractions within rain events are presented. Two sampling sites were chosen: one at Mexico City, a great polluted urban area, and the second at Rancho Viejo, a forested area under the meteorological influence of the city. The results show a general decrease during the early portion of the rain event. This seems to indicate that below-cloud scavenging is the most important mechanism while, from the small variations observed in the latter portion of the rainfall, it is possible to assume within-cloud scavenging as the predominant mechanism. Using the HCHO concentrations in rain water, the mixing ratios were estimated for the two sampling sites. The values were 0.68 ppb and 0.44 ppb at Mexico City and Rancho Viejo, respectively. Measurements at ground level in Mexico City gave a mean HCHO concentration in air of 24 ppb, much higher than the estimated mixing ratio. The high levels of HCHO found in ambient air and in rain water reflect anthropogenic emissions as the potential atmospheric sources.     

Susceptibility of different yeast species to environmental toxic metals

The purpose of the study reported here was to investigate the relative resistance of yeast species to various metallic and metalloid ions, with a view to gaining more knowledge on this subject, as resistant species may become dominant in habitats contaminated with the relevant metals. Saccharomyces cerevisiae, Candida albicans and Candida tropicalis were grown in media containing different concentrations of mercury (as HgCl(2)), cadmium (as CdCl(2)), lead (as Pb(CH(3)COO)(2)), arsenic (as Na(2)HAsO(4)) and selenium (as Na(2)SeO(3)) for various intervals. Invariably, the two Candida species turned out to be more resistant to all the metals studied than S. cerevisiae. The metal showing the highest toxicity for these species was mercury, with cadmium being the second, lead, the third and arsenic and selenium being the least toxic elements. Strains showing resistance to mercury were isolated, even in the case of S. cerevisiae.     

Bacterial leaching of metals from sewage sludge by indigenous iron-oxidizing bacteria

Bioleaching of metals can be achieved in sewage sludge using Thiobacillus ferrooxidans, which obtains its energy requirements from the oxidation of added ferrous iron. The purpose of this study was to verify the presence of indigenous T. ferroxidans and to evaluate their adaptive capacity and leaching potential. Nineteen sludges (primary, secondary, aerobically and anaerobically digested, oxidation pond) were tested and all of them contained indigenous iron-oxidizing bacteria. The acclimation of these organisms by successive transfers allowed a rise of sludge redox potential over 450 mV and a decrease of sludge pH between 3.8 and 2.2 over a 10-day incubation period. The metal solubilization efficiencies were Cd: 55-98%, Cr: 0-32%, Cu: 39-94%, Mn: 71-98%, Ni: 37-98%, Pb: 0-31% and Zn: 66-98%, were reached with these indigenous strains. The results obtained show that the metal bioleaching may be easily realized by direct acclimation of sludge microflora.     

Persistent organochlorine residues in soils from tropical and sub-tropical Asian countries

Soil samples from paddy fields, uplands, and urban areas (gardens and roadsides) collected from Vietnam, Thailand, and Taiwan were analysed to determine the residual levels of persistent organochlorine compounds such as DDTs, HCHs, and PCBs. DDT concentration in soil samples from Vietnam were found to be highest, with a mean value of 110 ng g(-1), and were followed by those in Taiwanese soils with a mean value of 20 ng g(-1). HCH concentrations were highest in soil samples from Vietnam (a mean value of 4.8 ng g(-1)) and were followed by those from Taiwan (a mean value of 1.4 ng g(-1)). Concentrations of PCBs were found to be highest in Taiwanese soil samples, with a mean of 95 ng g(-1). Interestingly, relatively high concentrations of PCBs in rural cultivated-soil samples from Vietnam were recorded with a mean value of 25 ng g(-1), probably suggesting PCB release from different kinds of weapons used during the Second Indochina war. The lowest concentrations of DDTs, HCHs, and PCBs were obtained in soil samples from Thailand, with mean values of 8.3 ng g(-1), 0.4 ng g(-1), and 2.7 ng g(-1), respectively.