Karl Banse

RATES OF GROWTH, RESPIRATION AND PHOTOSYNTHESIS OF UNICELLULAR ALGAE AS RELATED TO CELL SIZE—A REVIEW1,2

The decline of growth rate with increasing species size of unicellular algae grown under uniform conditions is quantified by applying to published data the equation, growth, (cell · time)−1= a (cell carbon)b where a and b are coefficients. The degree of size‐dependence might be highest under optimal conditions of growth where b is 0.75. Respiration rate is shown to decline with size in the same manner. It is postulated that gross photosynthesis and processes underlying growth are similarly size‐dependent. Growth, efficiency (net over gross photosynthesis) cannot be shown to be size‐dependent. Cell size, expressed as carbon, is proposed as a scaling factor in comparative algal physiology.

On the vertical distribution of Zooplankton in the sea

Abstract The effects of some factors on the vertical distribution of marine zooplankton are examined: temperature, water masses and transport, stratification, dissolved oxygen, pressure, seasonal and ontogenetic movements, and diurnal migrations. Distributions of species and biomass of holopelagic animals in deep water are reviewed. There are indications of a relation between species or community distribution and water masses in deep water. A homology between distributions of radioactive fallout and zooplankton in the surface layers is suggested; convection and advection, rather than animal movements, may best explain observed distributions. Zooplankton sampling should not be made at standard depths, but at hydrographically meaningful depths. The biomass of net plankton at great depths depends on surface production. There are indications that in the deep-sea the amount of nanoplankton is smaller than the amount of net plankton. Biological evidence of vertical divisions in the pelagic domain is not yet comparable to that for the provinces of zoogeography. Lack of knowledge of plankton near the sea floor is emphasized. Oceanographically, diurnal migration of holopelagic species may not be as important as implied by autoeoclogical studies. Diurnal migration seems to be weak or absent among pelagic larvae of bottom animals.

Seasonality of phytoplankton chlorophyll in the central and northern Arabian sea

Abstract Marked seasonality of ship-observed chlorophyll concentrations in the upper layers of the central and northern parts of the Arabian Sea is established for three hydrographically defined offshore areas. A peak related to the southwest (summer) monsoon occurs, either with or without a northeast (winter) monsoon-related peak. Both appear to depend on the establishment of a deep mixed layer and the concomitant nutrient supply, but at any station the relation between pigment content and mixed-layer depth or nitrate concentration is usually obscure.

Grazing, Temporal Changes of Phytoplankton Concentrations, and the Microbial Loop in the Open Sea

With the advent of maps of chlorophyll distribution in the world ocean (Feldman et al., 1989; Lewis, this volume), parochial questions can be asked on a global basis: (1) where, (2) when, and (3) why does phytoplankton occur in the open sea, and (4) how much is found? The first and fourth questions will be addressed briefly at the outset. The paper will treat the second and third questions at length, emphasizing the annual and seasonal time scales. Grazing will be shown to be a key variable that largely has been underrated. In addition to affecting phytoplankton, grazing will be recognized as central to the supply of substrate for the microbial loop.

Low seasonality of low concentrations of surface chlorophyll in the Subantarctic water ring: underwater irradiance, iron, or grazing?

Abstract In-situ surface chlorophyll concentrations (usually with phaeopigment) in the Pacific and Indian ocean sectors of the Subantarctic water ring (between the Subtropical Convergence and the Polar Front) are collated and reviewed. Offshore and away from hydrographic fronts, most means are only between 0.1 and 0.3 mg m−3, in spite of persistently high nutrients (N, P), and show little seasonality, in contrast to many Antarctic waters and the temperate-subpolar North Atlantic at the same range of latitude. Cell division rates can be expected to be high relative to the temperature-set maximum, and community net production is positive, at least during the summer, with some export of carbon. During the summer half of the year, the pigment concentrations are independent of mixed-layer depth (at least to 275 m), and, hence, of algal division rates. Also the relatively high winter pigment means, most between 0.10 and 0.15 mg m−3 even in the southern parts, show that underwater irradiance does not affect pigment concentration on the seasonal and regional average. Based on inferences from Antarctic bioassays and the enhanced dust supply in the Subantarctic, lack of iron is unlikely to cause directly the low chlorophyll levels, but probably is the reason for the dominance by small-celled phytoplankton. In homology to the offshore Subarctic and equatorial Pacific, grazing is postulated proximately to maintain the low pigment concentrations. These persistently low concentrations, coupled with relatively high cell division rates, entail low phytoplankton production rates that cannot outrun the physical supply of nutrients, thus allowing persistently high nutrient concentrations (N, P) to be maintained. The enhanced rate of primary production during the summer seems only to appear as enhanced concentrations of large zooplankton. In fronts, on island shelves, and downstream from New Zealand, however, phytoplankton blooms of large cells suggest that increased iron supply leads to a different community composition and dynamics and, presumably, at the islands to a temperate seasonal cycle. Much of the Atlantic Subantarctic is apt to be similar to the Indian and Pacific sectors, as is the permanently ice-free outer belt of the entire Antarctic. Thus, the offshore small-celled phytoplankton in these regions, more than a tenth of the global ocean area, appears to consist year-round of “grazer-controlled populations in an iron-limited ecosystem” (phrase used by NM Price and colleagues).

Hydrography of the Arabian Sea Shelf of India and Pakistan and effects on demersal fishes

Abstract Time-series observations of temperature, salinity, and oxygen off Cochin between August 1958 and January 1960 are presented. Upwelling, which begins with the southwest monsoon, causes an uplift of the 20°C isotherm by 90–100 m. The Kerala Coastal Deep Water of earlier authors, a subsurface water peculiar to the upwelling season, is redefined by the shape of the T-S relation. A comprehensive treatment is attempted of the hydrography in the area between Bombay and Karachi where time-series are not available from the open shelf. Mean sea level data suggest that during the southwest monsoon season cool subsurface water is always present on the entire shelf between Cochin and Karachi. Regular upwelling to the surface, however, is unknown north of 15°N. Probably June is the month this water usually appears on the middle of the shelf. All subsurface observations indicate that cool water is present from July onward below 50 m, sometimes even at shallower depths. Off Karachi, this situation may persist through November; off Bombay, through mid-December. Regional differences are pronounced, as are differences among years, in the period following the southwest monsoon. The cool water has a low oxygen content. During December 1963, sinking in a very limited area near Karachi was observed. There is no upwelling from December through March between Bombay and Karachi. Atmospheric cooling seems to cause the seasonally low surface temperatures near land. Away from the beaches the seasonal cycle of primary production is apt to be quite similar all along the west coasts of India and Pakistan. High photosynthetic rates can be expected during the southwest monsoon and later until the cool, deoxygenated subsurface water withdraws from the shelf. During the remainder of the year the density stratification in the surface layer will keep the photosynthetic rates low, near oceanic levels. Catch per unit effort of commercially exploited fishes between Bombay and Karachi in November 1963 appeared to be related to the oxygen content of near-bottom water. During the southwest monsoon and postmonsoon seasons, the entire shelf off the west coasts of India and Pakistan, below about 50 m, may possibly be devoid of exploitable concentrations of the demersal fish species utilized so far. The distribution of prawns may also be affected. The catch of demersal fishes below the principal discontinuity layer cannot be predicted from temperature of the near-bottom water during this period.

New views on the degradation and disposition of organic particles as collected by sediment traps in the open sea

Abstract Sharp gradients with depth ( z ) of fluxes ( F ) and concentrations ( C ) of organic particles are present in the upper few 100 m of the open sea. Because of under-determination of the system in the field, the balance of processes that maintain these gradients cannot yet be specified. A new scenario, with both quickly settling ( ∼ 100 m d -1 ), slowly decaying material and slowly sinking ( ∼ 20–33 m d -1 ), labile material that is degraded from within, mimics the observed gradients of F and C . A critique of recent ideas, which minimize decomposition of particles from within, notes that unambiguous interpretation in differences of cumulative particle collection between poisoned and live traps is difficult if daily decomposition rates of ∼ 20 to ∼ 30% prevail; these are claimed here for the labile fraction but have occasionally been observed even in bulk material from traps. The gradients with depth of F or C cannot be modeled as due to a first-order reaction. In addition, the description C = a z b may require b to change below the euphotic zone; quantitative and especially qualitative changes of mesozooplankton (0.2–0.3 mm) with depth are inferred as the cause. Finally, as in the euphotic zone, mesozooplankton might generate substantial amounts of dissolved organic matter at depth, which is presumably degraded by free-living bacteria. Attention to animals is urged for flux studies.

Uptake of inorganic carbon and nitrate by marine plankton and the Redfield Ratio

Published experiments are reevaluated regarding the uptake ratio of dissolved inorganic carbon (DIC) and nitrate in two plankton communities and the resulting elemental ratio of particulate organic matter (POM). The ratios are lower than Redfield values of 6.6 or 7.6 (by atoms); the uptake ratios of dissolved moieties are not measures for the composition of the newly formed POM; and uptake of DIC and nitrate may be entirely uncoupled. The use of closed systems of several 100 L to 1 m−3 content is suggested for studies of the underlying mechanisms.

On the coupling of hydrography, phytoplankton, zooplankton, and settling organic particles offshore in the Arabian Sea

Processes and issues related to the connections between hydrography, plankton, and the flux of organic carbon to great depth are reviewed for the offshore Arabian Sea and compared with observations in similar regimes of other seas. The south-north and west-east gradients and seasonality in the Arabian Sea are emphasized, but generalizations about the area as a whole are shunned. New data include regional differences in seasonality of satellite-observed chlorophyll for two years. The rule for the depth dependence of organic flux is unclear, therefore, this should be the first priority for future investigations. While the data for supply of organic carbon by settling and demand for the depth interval 200–1,000 m in the eastern Arabian Sea are in fair agreement, this is not true for the interval between 300 and 400 m. For advancing the understanding of the generation of flux in the upper layers and the consumption at depth, very much needs to be learned about the biology of the principal species of Zooplankton and nekton. To keep the task manageable, further studies of flux should focus on only one or two subdivisions of the Arabian Sea.

A GRAVIMETRIC METHOD FOR DETERMINING SUSPENDED MATTER IN SEA WATER USING MILLIPORE FILTERS

Abstract A modification of earlier methods for the determination of the weight of suspended matter in 0·5 to 51. of sea water is presented. Filter pore size can be selected to meet the requirements of the experiment. The precision is ± 0·15 mg at the 95 per cent level. The material can be subjected to subsequent analysis if the presence of the filter does not interfere.