ALBERT

Notes: Summary Throughout 1981, the first routine collections of a variety of fish were made under the McMurdo Ice Shelf near White Island, Antarctica. Estimates of their local biomass were calculated using food consumption patterns of resident seals. Since no significant primary production occurs at White Island, the resident fauna must be maintained by a large nutrient influx from the Ross Sea.

Notes: Abstract Dissolved total carbohydrate (TCHO), polysaccharide (PCHO), monosaccharide (MCHO) and organic carbon (DOC) were determined at 3-h intervals over 5 diel cycles in the mixed layer of the northwestern Caribbean Sea while following a drogued buoy. These data have been compared to populations of phototrophic (PNAN) and heterotrophic (HNAN) nanoplankton (2–20 μm diameter) and heterotrophic bacteria (HBAC) (0.2–2.0 μm diameter) estimated by epifluorescence counts, as well as to ΣCO2, phosphate, chlorophyll a and phaeopigment data determined simultaneously. Two different types of apparent diel dissolved carbohydrate (CHO) patterns were found. On 3 d when no sustained net ΣCO2 uptake was evident, TCHO and PCHO generally declined during the afternoon and early evening while MCHO tended to increase. On two other days when apparent sustained ΣCO2 uptake occurred during the day, there were large evening TCHO and PCHO peaks with constant or declining MCHO levels. These accumulations probably resulted from the release of recently produced PCHO from phototrophs. As was found earlier in the Sargasso Sea, PNAN populations were inversely related to PCHO concentrations. The sample to sample fluctuations of PNAN also were inversely related to the apparent rates of change of TCHO and PCHO, possibly due to an inverse relation between the rates of PNAN cell division and CHO excretion. Fluctuations in HBAC populations were inversely correlated with PCHO dynamics and directly related to MCHO variations, possibly due to extracellular hydrolysis of PCHO to MCHO during periods of rapid bacterial growth as well as to net heterotrophic PCHO uptake. A direct relationship between HNAN and TCHO fluctuations suggests the importance of HNAN excretion in the release of dissolved organics. The combined PNAN and HBAC fluctuations accounted for a more significant fraction of the variance in the apparent rates of change of PCHO than did any single population parameter indicating that intimate interactions between the microbial plankton groups are important in the in-situ regulation of CHO dynamics. Total system net TCHO release and uptake rates for 5 d averaged 56 and 53 μg C l-1 d-1 respectively, assuming that the observed fluctuations resulted from temporal planktonic processes in homogeneous water masses. While the data contain indications that this was the case, this assumption is not definitive.

Notes: Abstract This study (1975–1977) examines the effect of man-made structures on natural sand bottom communities in shallow water in San Diego County, southern California, USA. While there were shallow scour effects to 15 m around some artificial reefs, the reefs had no measurable effect on sand ripple patterns, grain size, organic carbon or infauna beyond the scoured areas. Foraging by reef-associated fishes produced profound alterations in the epifauna populations of the sea pen Stylatula elongata. The sea pen densities were 4 to 10 m-2 before the reefs were established, but within 5 mo were eliminated from distances greater than 200 m around the reefs. On the other hand, densities of the tube-building polychaetes Diopatra spp. seemed to be enhanced in the immediate vicinity of the artificial reef. Oil platforms and bridge pilings seem to have much more profound effects on the nearby sand communities than do the relatively small artificial reefs. In addition to the elimination of sea pens, Diopatra spp. densities increased from 〈1.0 m-2 in control areas to as many as 73 m-2 in the vicinity of oil platforms. Grain size and infauna were strongly affected by the oil platform.

Notes: Abstract Microplankton cages with porous polycarbonate membrane sides were used to investigate the population growth of Favella sp., a large tintinnid which preys on dinoflagellates, Balanion sp., a non-loricate ciliate which also preys on dinoflagellates, and two other tintinnids, Eutintinnus pectinis and Tintinnopsis kofoidi, at close to in-situ conditions in a small estuary during a spring dinoflagellate bloom. The effects of temperature and food concentration on the growth of Favella sp. and Balanion sp. were also investigated in culture. Growth rates in the field were variable from day to day. The highest net growth constant (base e) observed for Favella sp. in the cages was 0.032 (generation time 21.7 h). This was lower than growth constants which can be achieved in culture. Food availability, parasitism by the dinoflagellate Duboscquella sp., and perhaps life cycle events all contributed to the lower net growth rate of Favella sp. in the field. The highest net growth constant observed in the cages for Balanion sp. was 0.068 (generation time=10.7 h), which is also lower than growth constants achieved in culture. The growth of Balanion sp. populations in the cages was limited by the availability of small-sized dinoflagellates and by predation. The highest net growth constants observed for E. pectinis and T. kofoidi were 0.030 and 0.068, respectively; we know little about the factors controlling the growth of these tintinnids.

Notes: Abstract Six diel TCO2 cycles determined by infrared (IR) photometry from five drift stations occupied between 24 February and 16 March 1979 in the mixed layer of the northwestern Caribbean Sea are examined. Comparison of TCO2 variation with coincident salinity and O2 variation demonstrated that TCO2 often co-varied with these independently measured variables. During five diel cycles TCO2 variation was characterized by nocturnal production and diurnal consumption. The inverse, diurnal production of CO2, occurred downstream from Misteriosa Bank, whose corals apparently contributed to a water mass having a twofold increase of POC and a sixfold larger population of heterotrophic nanoplankters. For the five diel studies carried out in waters with balanced or nearly blanced heterotrophic and phototrophic components of the nanoplankton, CO2 consumption at constant salinity always occurred between 06.00 and 09.00 hrs. Net uptake often continued through 15.00 hrs, but not always in the absence of significant salinity changes. At constant salinity net O2 evolution never exceeded 0.5 μmol l-1 h-1 while net CO2 uptake consistently averaged 3 μmol l-1 h-1 for an apparent net production of 36 mg C m-3 h-1, which greatly exceeds the O2 changes and open ocean 14C estimates from the literature. Diurnal consumption was apparently balanced by nocturnal production of CO2 so that no significant net daily change in TCO2 was observed. Departures from theoretical PQ and RQ and the possibility of nocturnal variations in formaldehyde and carbonate alkalinity imply that chemotrophs, both methane producers and methane oxidizers, play a significant role in CO2 cycling. This could be through the metabolism of the nonconservative gases CH4, CO, and H2, and a link between chemotrophy and phototrophy through these gases is hypothesized. These open system measurements were subject to diffusion and documentable patchiness, but temporal TCO2 changes appear to indicate the net direction of microbiological activity and join a growing body of literature showing dynamic variation in CO2 and O2 that exceeds estimates by 14C bottle assays of carbon fixation.

Notes: Abstract A stimulation model of copepod population dynamics (development rate, fecundity, and mortality) was used to compute the predatory consumption necessary to control population growth in three dominant copepod species (Pseudocalanus sp., Paracalanus parvus, and Calanus finmarchicus) on Georges Bank, given observed seasonal cycles of copepod and predator populations. The model also calculated secondary production of each species. Copepod development rate and fecundity were functions of temperature while mortality was a function of predator abundance and consumption rate. Daily inputs of temperature and predator abundance (chaetognaths, ctenophores, and Centropages spp.) were derived from equations fit to field data. Model runs were made with various consumption rates until the model output matched observed copepod seasonal cycles. Computed consumption rates were low compared with published values from field and laboratory studies indicating that, even at conservative estimates of consumption, predators are able to control these copepod populations. Combined annual secondary production by the small copepod species, Pseudocalanus sp. and P. parvus, was nearly twice that of the larger C. finmarchicus with P. parvus having the highest total annual production.

Notes: Abstract Laboratory and field studies were used to show that development rate and survival of the copepods Pseudocalanus sp. and Paracalanus parvus are generally not food limited on Georges Bank. Copepods were reared in the laboratory at a series of phytoplankton concentrations (25 to 200 μg carbon l-1) spanning the range of particulate carbon and nitrogen measured on Georges Bank in October, 1978 and February, 1979. Pseudocalanus sp. and P. parvus were reared at 5° and 12°C, respectively. Development rate and survival in both species were not affected at Georges Bank food concentrations but were reduced at lower food levels. Development times from hatching to adulthood was 60 to 70 d for Pseudocalanus sp. and 25 to 30 d for P. parvus.

Notes: Abstract Four geographic populations of the painted greenling Oxylebius pictus, a small cryptic reef fish of the western coast of North America, were examined for biochemical evidence of genetic differentiation. Painted greenlings in Puget Sound and those in central and southern California are similar by Nei's genetic identity (I=0.966 to 0.995); Fowever, other observations argue for genetic differentiation among the 4 populations. First, there are geographic differences in allelic frequencies at two loci (Est-3 and Pgm), with a geographic cline exhibited at the latter locus. Second, and most significant, two assayable loci are uniquely present in pairs of populations below Point Conception (G3pdh-3) and above Point Conception (Idh-3), respectively. Larval dispersal patterns are inferred from breeding times for the painted greenling and on patterns of currents off the western coast of North America. We believe that gene flow in this species is less across Point Conception than between Puget Sound, Washington, and Monterey, California, on the basis of these genetic data and the patterns of dispersal.

Notes: Abstract Significant correlations between trophic components of the 〈20 μm microbial plankton and the concentrations of total dissolved carbohydrate (TCHO) and polysaccharide (PCHO) have been found at two drogued buoy stations which were sampled at 3 or 4-h intervals over diel cycles. An attempt was made to sample on two pre-selected isotherms (approximating isopycnals) at each station. Significant inverse correlations of TCHO and of PCHO with numbers of phototrophic nanoplankton (PNAN) were found along both isotherms at a station off the Carolina coast. Off central Florida, TCHO and/or PCHO were significant multiple linear functions of PNAN, heterotrophic bacterioplankton (BAC) and sometimes heterotrophic nanoplankton (HNAN) counts. Partial regression coefficients for PNAN were always negative and those for HNAN were positive. Inverse trends dominated the relations of BAC with PCHO and TCHO. The combined data from the two stations (300 nautical miles apart) produced very similar multiple linear relations. This suggests that the observed relationships are real, resulting from general physiological processes and interactions of the microbial plankton groups rather than from chance occurrences at a particular station, and that the combined activities of the 〈20 μm plankton actively regulate dissolved carbohydrate concentrations in the Sargasso Sea.