Photosynthetic characteristics of marine phytoplankton from contrasting physical environments

Two suites of phytoplankton samples have been collected in consecutive years at various times over a day from selected depths within vertically mixed and stratified water columns in the western Irish Sea, in order to provide a range of possible light histories within the populations collected. Values for the maximum rate of ¹⁴C retention (P _max) and the initial slope of the ¹⁴C retention: light intensity curve () were obtained. Supra-thermocline samples from the stratified water exhibited higher P _max values than corresponding subthermocline samples. Higher values of were also generally associated with samples from the supra-thermocline zone of the stratified region. Differences in the depth distribution of P _max and in the mixed water were small, except in the presence of a shallow thermocline. In one suite of samples from the stratified water, a diurnal increase in the P _max values of the supra-thermocline samples was observed. P _max values obtained from the samples from the mixed water were interpreted in relation to the distribution obtained from the samples from the stratified zone. Data from both the contrasting sites visited for one sample suite demonstrated a two-phase relationship between the chlorophyll a concentration and both P _max and . The rates of ¹⁴C retention of the first suite of samples were estimated by two techniques. The average differences in the retention were greater in samples from the sub-as opposed to suprathermocline zone. No trends were apparent in the smaples from the mixed waters.     

The persistence of chronically accumulated hydrocarbons in the hard shell clam Mercenaria mercenaria

Hard shell clams, Mercenaria mercenaria, from the chronically polluted environment of the Providence River, USA, were transferred to a clean laboratory system located in lower Narragansett Bay, Rhode Island. The hydrocarbon contents of these transplanted clams were monitored for 120 days after transfer. After this period only slight depuration had occurred. A 41.9 g g wet weight^-1 average initial hydrocarbon burden decreased to 29.3 g g^-1, a decrease that became statistically significant (P<0.1) only after 120 days. At most, only 30% of the clams' hydrocarbons were lost. These findings indicate that the duration of the exposure period and the chemical nature of the source hydrocarbons are both instrumental in determining the persistence of these compounds in filter-feeding bivalves. Chronically accumulated petroleum hydrocarbons are strongly retained by the organisms and are only very slowly depurated.     

Kinetics of light-intensity adaptation in a marine planktonic diatom

The marine planktonic diatom Thalassiosira weisflogii was grown in turbidostat culture under both continuous and 12 hL: 12 hD illumination regimes in order to study the kinetics of adaptation to growth-irradiance levels. In both illumination regimes adaptation to a higher growth-irradiance level was accompanied by an increase in cell division rates and a decrease in chlorophyll a cell^-1. The rates of adaptation for both processes, derived from first order kinetic analysis, equaled each other in each experiment. The results suggest that during the transition from low-to-high growth-irradiance levels chlorophyll a is diluted by cell division and is not actively degraded. Introduction of a light/dark cycle lowered the rate of adaptation. In transitions from high-to-low growth-irradiance levels there was a sharp drop in growth rates and a slow increase in chlorophyll a cell^-1 under both continuous and intermittent illumination. In the 12 hL:12hD cycle there was a circadian rhythm in chlorophyll a cell^-1, where cellular chlorophyll contents increased during the light cycle and decreased during the dark cycle. This circadian rhythm was distinctly different from light intensity adaptation. For kinetic analysis of light intensity adaptation in a 12 hL: 12 hD cycle, the circadian periodicity was separated from the light intensity response by subjecting the data to a Kaiser window optimization digital filter. Kinetic parameters for light-intensity adaptation were resolved from the filtered data. The kinetics of lightintensity adaptation of marine phytoplankton are discussed in relation to their spatial variations and time scales of mixing.This research was performed at Brookhaven National Laboratory under the auspices of the United States Department of Energy under Contract No. DE-AC02-76 CH00016     

Apparent predation on ichthyoplankton by zooplankton and fishes in nearshore waters of southern California

Plankton collected at discrete depths in Santa Monica Bay, California, USA, during January 1982 were examined for fish eggs and larvae that had been attacked or consumed by zooplankton. The bongo net remained open for only 3 min and samples were preserved within 5 min of capture. Juvenile and adult fishes that had been captured by otter trawl and preserved within 20 min of capture were examined for ingested fish eggs and larvae. Three copepods (Corycaeus anglicus, Labidocera trispinosa, and Tortanus discaudatus), one euphausid larva (Nyctiphanes simplex), one amphipod (Monoculoides sp.), and an unidentified decapod larva were found attached to fish larvae in the preserved plankton samples (attachment to 23% of the fish larvae was observed in one sample). Overall, about 5% of the white croaker (Genyonemus lineatus) larvae and 2% of the northern anchovy (Engraulis mordax) larvae had attached zooplankton predators. Most fish larvae with attached zooplankton predators were small. We found no indication of zooplankton predation on fish eggs. Few fish eggs and larvae were found in the digestive tracts of juvenile or adult fishes, and the ingested fish larvae were relatively large. The discussion considers apparent preyspecificity of the zooplankton predators as well as potential biases that may be associated with preserved samples collected by nets.     

A rapid kinetic technique for quantifying polycarbonate species in coalspoils

A rapid, automated procedure has been used for differentiation and quantitative determination of siderite, calcite and dolomite, based on the different rates of dissolution of the three carbonate species when reacted with excess 5 mol/litre HCl. The method employs manometric measurements of acid-liberated CO₂ with a membrane differential-pressure transducer coupled to a stripchart recorder. Tested on the three carbonate species, singly and in pairs, the technique is discriminatory, sensitive and relatively rapid.Contributions from the Department of Agronomy, University of Kentucky Agricultural Experiment Station in Lexington, and Institute for Mining and Minerals Research of the University of Kentucky. The investigation reported in this paper (No. 83-3-206) is in connection with a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Director.     

Indications from photosynthetic components that iron is a limiting nutrient in primary producers on coral reefs

Because iron is not available generally in oxygenated sea water, it may be a limiting factor in marine primary production. This hypothesis was tested in the context of Davies Reef, Latitude 18°50′S (one of the coral reefs in the central region of the Great Barrier Reef system). Samples were collected for study in the period August, 1980 to March, 1981. Sea water around the reef contained ≦2x10^-6 M Fe, surface sediments from the reef contained 66±26 (1 SD) ppm total Fe, and interstitial water near the surface contained ≧5x10^-7 M Fe. Thus, Fe constituted a trace component of the reef environment, but limited Fe should be available to algae associated with the sediments. Specific biochemical analyses to test the Fe status of benthic photosynthetic organisms were carried out with a common blue-green alga, Phormidium sp., and a ubiquitous symbiotic dinoflagellate, Gymnodinium microadriaticum (zooxanthellae). The blue-green alga contained the electron transport protein, flavodoxin, which is found only in Fe-deficient organisms. Supporting evidence for Fe stress in this organism included chlorosis in the presence of plentiful biliprotein, and very low extractable photosynthetic cytochrome, c-553. The latter observations were shown to be the result of Fe deficiency in laboratory cultures of a blue-green alga, Synechococcus sp. These cultures showed that production of flavodoxin is not a universal response of algae to Fe stress, but that lowered cellular concentrations of Fe-containing proteins involved in photosynthesis probably is universal. The zooxanthellae from a soft coral, Sinularia sp., had three-fold lower total Fe and ferredoxin (an electron transport protein), than the same alga from a clam, Tridacna maxima. Thus, some algae in symbiotic associations may also suffer Fe-deficiency. It was concluded that the degree and extent of Fe-stress in primary producers on a coral reef may influence growth rates, biomass, and distribution of species.     

Spatial,temporal, and behavioral patterns in emergence of zooplankton in the lagoon of Heron Reef,Great Barrier Reef,Australia

A total of 34 zooplanktonic taxa were common in emergence trap, reentry trap, and net-tow samples taken in the lagoon of Heron Reef, Great Barrier Reef, between 27 February and 22 March and between 11 June and 4 July 1985. Twenty-nine of these taxa were classified as demersal (17 taxa), meroplanktonic and larval (10 taxa), or incidental (2 taxa). The remaining five multispecific groups yielded variable results. Differences were observed between two locations separated by 200 m, with emergence 2 to 62 times greater for 22 taxa at a deeper site with larger coral formations. Most zooplankters were more common (2 to 122 times) in samples from 1 m² areas around 0.25 to 0.5 m² patches of branching coral. However, two species of copepods, Pseudodiaptomus colefaxi and Metis holothuriae, were taken in greater numbers (3 to 12 times) from open sand. Seasonal increases (2 to 322 times) were observed for 13 adult taxa and 8 classes of larvae or juveniles in the summer and for 10 adult taxa and one larval group in the winter. Fourteen of the 17 demersal taxa and 4 groups of large larvae or juveniles emerged in numbers 2 to 323 times greater during lunar quarters or new moons. In contrast, 6 larval taxa and 4 groups of small or transparent adults displayed significant emergence during full moons. Five diurnal emergence patterns were shown by 27 taxa, with patterns varying primarily among lunar periods. The variety of taxon-specific patterns observed in this study highlight a need for caution when generalizing about demersal zooplankton.     

Influence of inter- and intra-daily light-field variability on photosynthesis by coastal phytoplankton

An investigation was carried out to determine the relationships between the principal photosynthetic parameters of natural marine phytoplankton and the properties of the irradiance of the preceding five days and the intra-daily ambient irradiance. Samples used in the study were collected from Strangford Lough, Northern Ireland during both winter and summer between 1979 and 1981. Photosynthetic parameters were determined for both constant and ambient incubation light fields. The fluctuation properties of the irradiance field exerted little influence on the photosynthetic parameters. In summer populations, the parameters obtained from morning samples were strongly influenced by the total irradiance recorded on the fourth day previous to experimentation, irrespective of the incubation irradiance. In contrast, the corresponding parameters from afternoon samples were most influenced by the total irradiance received during incubation. The influence of these two separate factors over a day may contribute to variability in the magnitude of diel changes in marine phytoplankton photosynthesis.