Showing papers on "Productivity (ecology) published in 1973"

Primary Production: Terrestrial Ecosystems

Abstract: The history of growth in understanding of primary productivity and in making estimates of biosphere production is reviewed. Two approaches to estimation of land production are discussed. Production may first be estimated by mean values for ecosystem types and the areas of these. A total production of 100×10 9 tons/year is thus estimated for the continents, making up 29% of the earth's surface. The energy content of net primary production is 426×1018 cal for the continents and 261×1018 cal for the seas, implying a biosphere energy efficiency of 0.13% relative to incident sunlight of the full spectrum at the earth's surface. As a second approach, the relation of productivity to mean annual temperature and precipitation is analyzed. On the basis of these relationships, a “Miami model” map of primary productivity of the continents is presented.

An analysis of factors governing productivity in lakes and reservoirs1

Abstract: Data collected as part of the International Biological Program from 43 lakes and 12 reservoirs, distributed from the tropics to the arctic, were subjected to statistical analysis to establish which factors are important in controlling production and how they are related. In the whole body of data, variables related to solar energy input have a greater influence on production than variables related to nutrient concentration; in lakes within a narrow range of latitude, nutrient-related variables assume greater importance. Morphological factors have little influence on productivity per unit area in either case. Chlorophyll a concentration is a good indicator of nutrient conditions and when combined with an energyrelated variable constitutes a good estimator of primary production.

Primary production: The biosphere and man

Abstract: The net primary production of the biosphere is about 160×10 9 tons/year, with 34% of this in marine, 0.8% in freshwater, and 66% in terrestrial ecosystems. World biomass (in the year 1950) is estimated as 1840×109 tons of dry matter, strongly concentrated on the continents (99.8%) and mostly in forests (90%). The total chlorophyll of the biosphere is about 240×106 tons; with about 90% of this on land. Land communities typically have 3–8 m2 of leaf surface and 1–4 g of chlorophyll per m2 of ground surface; chlorophyll in the oceans ranges mostly downward from 0.5 g/m2. Terrestrial and marine communities are in contrast in their mean ratios of biomass to net annual productivity (17.3 and 0.07) and of net annual productivity to chlorophyll (473 and 3100g/g). Man harvests about 1.3×109 tons/year of food from the land surface, about 17×106 tons/year from water bodies, with 88% of this from the seas. Despite the immensity of the biosphere, man has reduced its biomass and is beginning, with pollution, to affect its productivity. The relation of an exponentially increasing human population and industry to the biosphere is thus unstable. Some characteristics of this instability and the different consequences of overgrowth for poor or developing and rich or developed countries are considered.

Enhancement of net primary productivity by herbivore grazing in aquatic laboratory microcosms1

Abstract: The role of herbivore grazing intensity as a factor affecting net primary productivity was investigated by introducing varying biomasses of a starved herbivore (Notropis spilopterzcs) into replicate autotrophic microcosms, After 20 clays, the enhancement of net primary productivity in the experimental microcosms was directly related to herbivore biomass up to a certain density and inversely related above this. The relationship approximates the first derivative of a sigmoid population growth model. Enhancement of primary production under these experimental conditions appears to be due to reductions of standing crop and increased turnover rates of producer populations. The results suggest that these responses were independent of increased nutrient regeneration rates brought about by grazing. The distinction between productivity (a rate function) and standing crop (a static mcasurcment) has often been made. Yet, the notion that reduction in producer standing crop corresponds to a reduction in food material for a consumer population is taken as axiomatic in many investigations of production-consumption relationships. Several observations of changes in productivity of producer populations immediately following rapid removal of consumers suggest that measurements of standing crop are not necessarily indicative of the amount of food material available for consumption by a consumer population. For example, Paine and Vadas ( 1969) found that removal of sea urchins ( StrongyZocentrotus spp, ) resulted in significant alterations in benthic algal species composition and increases in primary productivity. Also, the high mortality of limpets on the Cornish shorts subsequent to detergent spraying following the Terre!/ Canyon oil spill in 1967 resulted in enhanced primary productivity by attached green algae (Smith 1968). But thcrc has been little direct invcstigation of the dynamic effects of hcrbivorc 1 This research was supported by a research fellowship and grant-in-aid from the SUNY Research Foundation JAC/UAC 365-570. ’ Prcscnt address: Battelle Columbus Laborntories, 505 King Avenue, Columbus, Ohio 43201. consumption on rates of primary productivity. Hargrave ( 1970) varied numbers of the herbivorous amphipod Hyalda axteca in sediment cores. The productivity of the sediment microflora was stimulated with increased amphipod numbers within the range of natural density. Above this lcvcl, with increased numbers of amphipods, algal production declined. The results suggest that increased grazing, within the range of natural grazing intensities, scrvcs to increase the primary productivity of benthic microflora. One explanation for the cnhancemcnt of net primary productivity by low level grazing is that herbivores might increase nutrient cycling rates in nutrient-limited situations. Nutrient rcgcncration by aquatic consumers has been discussed by Johanncs ( 1968) and is undoubtedly important for producer populations in situations of nutricnt limitation. However, several reports suggest that the cnhanccmcnt of net primary productivity by grazing might bc due to other factors. Welch ( 1968) found that nutrient reserves in sand recdgrass bccamc deplctcd in rcsponsc to grazing and deduced that the plants wcrc utilizing thcsc rcscrves to satisfy a newfound growth potential in the aftermath of standing crop rcductions due to grazing. Examples such as this from tcrrcstrial habitats may or may LIMNOLOGY AND OCEANOGRAPIIY 31 JANUARY 1973, V. 18( 1)

Trophic Dynamics and Niches of Salt Marsh Foraminifera

Abstract: Energetic considerations of the growth of three species of littoral benthic foraminifera, Allogromia laticollaris, Rosalina leei , and Spiroloculina hyalina , have been made on laboratory-grown populations. Under optimum laboratory conditions A. laticollaris has the greatest intrinsic rate of increase (r = 2.533 org/day); S. hyalina (r = 1.472 org/day), and R. leei (r = 0.272 org/day) being less fecund. The respiration rates of the three species were similar (0.5–4.5 μ1/mg body wt/hr) within the temperature range (15–35 C) tested. The species studied are selective feeders. Only 4-5 of 28 species of algae tested were consumed in significant quantities (40-150 × 108 g/foram/day). Although great numbers of bacteria were eaten, their biomass was negligible when compared to the algae. The ecological growth efficiency (Ee) of the three species tested is highest in fresh cultures (5-20%) and declines rapidly. Evidence suggests that the species studied are well adapted for the rapid changes in the microbial community structure which take place throughout the summer, and that community stability and high rate of productivity are achieved through diversity.

The productivity of hawaiian fringing-reef crustose corallinaceae and an experimental evaluation of production methodology†

Abstract: Estimates of the mean net total contribution to the Waikiki reef by Porolithon oro rates determined by all three techniques showed the same serial order, by species, from highest to lowest producer. The pH and 0, electrode methods are more useful and reliable than the ‘“C data where high sensitivity is not critical. The Winkler oxygen method has been classically applied to light and dark incubated bottles for studying benthic productivity. Its sensitivity permits significant determinations where OZ evolution is as low as 0.15 mg literl. Where 02 evolution exceeds 0.5 mg liter-l, polarographic OZ analyzers are useful. Variations in COn have also been used to measure photosynthesis, and changes in pH (Beyers et al. 1963) have proven to be reasonably sensitive indices to COa uptake, The 14C technique is the most sensitive, widely accepted, and routinely applied of the methods. Such workers as McAllister et al. ( 1961) and Thomas ( 1964) have compared the 14C method, Winkler 02 (light-dark bottle), and pH measurements for determining the productivity of natural and cultured phytoplankton populations. Miiller and‘ Kniipp ( 1971) evaluated 14C, 02 electrode, and Winkler analyses in a study of primary productivity in flowing waters. In my study, all of the above techniques in addition to others (gas chromatography, Ca electrodes, 45Ca, and atomic absorption spectrophotometry) were used on the same thalli simultaneously, to measure the productivity of reef-building coralline algae. 1 This work was supported by U. S. Atomic Energy Commission Contract AT ( 04-3) 235. Previous workers (e.g. Setchell 1926, 1928; Crossland 1938) have debated the relative importance of calcareous organisms in the reef environment. Biologists have classically stressed the importance of standing stock (usually in subjective terms) and geologists have emphasized sediment mcasurements. Few approaches have considered the functional roles played by reef-building organisms or the correlation between standing stock and the skeletal components that remain after grazing, export, and resolution. As Gorcau ( 1963) pointed out, the missing quantity is a calcification-rate parameter. Among the three studies to date of the functional importance of crustose Corallinaceac, that of Sargent and Austin ( 1954) assumed from the density of crustose coralline algae on the seaward face of the reef at Rongelap Atoll that the area had high photosynthesis. They measured net oxygen production of various reef organisms in jars set in the flowing interisland waters: three measurements of a single Porolithon thallus yielded rates comparable to those of corals (based on sample wet weight). Goreau ( 1963) first measured carbon fixation and calcium carbonate deposition rates for various reef-building algae by radioisotope techniques ( 14C and 4%a simultaneously). He reported the uptake LIMNOLOGY AND OCEANOGRAPHY 946 NOVEMBER 1973, V. 18( 6) UENTHIC ALGAL PRODUCTIVITY 947 rates in terms of milligram moles of C or Ca fixed per milligram N per hour (an index of cell protein), which is difficult to relate either to the standing stock of calcareous organisms or to scdimentological studies, Marsh ( 1970) found the productivity of unidentified crustose Corallinaceac from Eniwetok Atoll and Kaneohe Bay, Hawaii, measured with a specially constructed dissolved-oxygen electrode, to bc within the same order of magnitude but lower than that of other photosynthetic reef organisms. However Smith (1973) compared the productivity at Eniwetok and obtained results that may be contradictory to those of Marsh, Both a transect dominated (visually) by a mixture of corals and corallinc algae and one dominated by a coralline algal turf (Porolithon and Jania) calcified at 4,000 g CaCOn m-2 yr-1, but the coralline algal community showed a higher net production (24-hr day) rate than did the coralalgal community (7.20 vs. 1.56 g C m-3 day-l). It may be that organisms not visually prominent arc rclativcly more important metabolically than the calcifying organisms, since total community metabolism was the parameter measured, I am grateful to M. S. Doty for his advice and encouragement during all phases of this rcscarch and to S. V. Smith for critically reading the manuscript, METHODS AND MATERIALS The productivity of crustose Corallinaceae as measured includes the rate of fixation of particulate and dissolved organic carbon (primary and secondary productivity) as well as the rate of fixation of particulate inorganic carbon (calcification). The experimental chambers used (Fig. 1) are modifications of that of Doty (1967). The metal screws were moved outside the internal cavity to avoid contact with the cuhure medium. Three double-O-ring apertures were constructed in the top to seal three clectrodcs (pH, 02, and Ca) airtight and a tapered stopper was fitted in one corner of the top to facilitate filling and expelling air from the chamber. The chambers hold 600 ml rather than 300 and contain a rack to support the crustose thalli on monofilament Iinc during incubation. The portion of each species incubated consisted of approximateIy equal fragments of the same thallus or similar thallus chipped from the same square meter patch of the Waikiki fringing reef at 0930 hours. Each species was sampled in the area of its peak of abundance (Littler 1973). Three to five small fragments of the freshly collected algae were placed horizontally on a support of monofilament line in each of two duplicate chambers containing MiIlipore-filtered seawater; a third chamber (without electrodes and covered with aluminum foil) was used as a blank to correct for dark uptake by the algae. The lids, with the clectrodcs inserted, were placed on the chambers and secured, and the chambers were completely filled so that no air bubbles remained. The two chambers were placed in a water bath over identical magnetic stirring motors, modified to run cooler, in a photoperiod incubator, at 24.0°C, above the light saturation intensities of the corahine algae (10,800-21, 500 lux). The rate of stirring was adjusted to a standard setting and the chambers were allowed to equilibrate for about 1 hr. During the equilibration period, initial samples were taken. A 300-ml sample of the water used had reagents added for later Winkler analysis. Two ampoules of 10 ml each were labeled and sealed for measurement (by procedures in Strickland and Parsons 1968) of initial dissolved organic carbon and calcium. All seawater was from one 40.0-liter Millipore-filtered (0.45pm pore size) batch that was collected from just inside the algal ridge area of the Waikiki reef, filtered immediately and stored in the dark in a sterilized polyethylene carboy. Data recording began at 1130 each day to minimize any effects of periodicity. Dissolved 02 and pH were monitored for a 1-hr dark period, at the end of which the chambers (including the dark control)

Biomass and Productivity Models of Forest Canopies

Abstract: Knowledge of the amount, distribution and functioning of foliage within canopies is important in understanding the productivity of plant communities because photosynthesis forms the basis for energy capture and dry matter growth. Most forest trees maintain their productive structure through systems of branches which, in themselves, contain a considerable fraction of dry matter produced.

Field Studies on Photosynthesis of Cladophora Glomerata (Chlorophyta) in Green Bay, Lake Michigan

Abstract: Net photosynthesis of Cladophora glomerata was measured at three sites in lower Green Bay, Lake Michigan, from late spring through summer, 1971. Lower levels of productivity occurred early in the season at two of the sites, when water temperatures were lowest. At the third site water temperature and productivity varied the least. Contrary to other reports, we found that Cladophora made relatively efficient use of low illumination. Under statistically similar temperature and irradiance levels, productivity was higher with increasing proximity to the mouth of the Fox River. Nitrogen, calcium, strontium, sodium, and zinc also were highest in concentration in plants receiving the greatest amount of effluents from the Fox River in comparison with the site receiving the least. Site differences in productivity appear to be related to nutrient levels, whereas seasonal differences in productivity are probably most closely related to seasonal temperature differences. See full-text article at JSTOR

Late Glacial and Postglacial Productivity Changes in a New England Pond

Abstract: During the late glacial and postglacial the productivity of Berry Pond in Berkshire County, Massachusetts, underwent a number of significant oscillations. This is suggested by data on sedimentary chlorophyll degradation products, diatoms, and Cladocera. The productivity changes were. apparently controlled by changes in weathering, terrestrial vegetation in the watershed, litter production, and runoff. There are associated changes in cladoceran community structure.

Spatial variability of the productivity: biomass ratio for phytoplankton in a small marine basin

Abstract: The productivity:biomass (P:R) ratio for phytoplankton was studied using a replicated sampling design at six stations in a small marine basin. On six out of ten sampling days, statistically significant differences were revealed in the P:B ratios between stations. This result is consistent with the concept of contemporaneous disequilibrium which emphasizes the spatial component of the heterogeneity of the phytoplankton habitat,

Primary Productivity and Microenvironment in an Ambrosia-dominated Old Field

Abstract: Aboveground primary production in a field dominated by Ambrosia artemisiifolia in southeastern Illinois was 630 + 168 g m-2 in 1968 and 595 + 142 g m-2 in 1969. During the 1st year productivity for the entire growing seasorn was 7.8 g m-2 dayand 14.4 g mr2 dayfor a short period during the growing season. Efficiency of aboveground net primary production was 1.3 % between plowing of the field and peak, standing, aboveground biomass of the plant community in mid-August. Efficiency was a high 2.6% during a short period of the growing season when productivity was maximal. Comparisons with other data on primary production of 1-year and 2-year fields in several areas of the eastern deciduous forest biome show that the southeastern Illinois fields are significantly more productive and more efficient. This suggests that generalizations concerning community organization in young successional ecosystems require further investigation.

Stand Equations for Estimating Aerial Biomass, Net Productivity, and Stem Survival of Young Aspen Suckers on Good Sites

Abstract: Equations were developed from single and repeated stem counts, diameter and height measurements to predict leafless aerial biomass, net productivity, and stem survival in young trembling aspen sucker stands on good to excellent sites. Although the most dense stands studied reached maximum periodic annual productivity at age 16, maximum mean annual productivity will not be reached until after 20 years of age.

Primary production: Marine ecosystems

Abstract: The seas occupy the greater part (70%) of the earth's surface, but their total net primary production is less than that of the land. Depletion of nutrients in the lighted surface waters is responsible for low productivities of most of the open ocean; higher productivities occur in coastal waters and areas of upwelling. A recent estimate of total production for the marine plankon is 50×10 9 metric tons of dry matter per year; the total with benthic production may be 55×109 tons/year. The value for the plankton may be too low; there are persistent problems in measuring productivity with the radiocarbon technique. Because harvestable fish populations are concentrated in a limited area of more productive waters, where they are subject to overharvest and pollution effects, major increase in food production from the seas is not likely.

A review of forest biomass accumulation

Abstract: Estimates of forest biomass and Its distribution are essential to the understanding of many aspects of forest ecology and ecosyst dynamics, as they can provide a basis for determination of productivity, energy flow, and chemical composition for mineral cycling studies. Most work dealing with productivity of forest systems has been concerned only with the merchantable volume of mass of timber, ignoring such components as leaves, branches, bark, and roots; therefore many of the early bi ss studies were carried out only in relation to management programs. This Involved estimating the biomass and its chemical composition, calculating what proportion would be removed in logging or cropping, and then estimating possible site deterioration (135, 229, 233).

Grazing and production by zooplankton in lakes of the Cedar River watershed

Abstract: Zooplankton grazing rates and life history stage densities for secondary production estimates were determined in three lakes in the Cedar River watershed, Washington Eight copepod species, seven cladoceran and nine rotifer species were identified in the three lakes No one species of cladoceran or copepod occurred in all the lakes, but the rotifers are common throughout Copepods in the lakes showed no clear diet migration, while two cladocerans did migrate Copepods were most important numerically in the lakes Some principal members were Diaptomus ashZandi which reached a seasonal maximum adult density of 11/2 (mean of water column) in Lake Sammamish and LimnocaZanus in Chester Morse which reached a maximum of 07/2 Two Diaptomus species are Important in Findley Lake Densities averaged about 10 times greater in Sammamish than in the two oligotrophic lakes Data on population dynamics from the egg ratio technique are given for the common cladocerans in the three lakes Grazing of phytoplankton by zooplankton stimulated photosynthetic carbon uptake in the light in excess of 200 percent over ungrazed populations Phytoplankton loss rates from grazing ranged from 0002 to 0268 pg chi a/ animal day Feeding was found to be maximum at low concentrations of algae These rates account for from 2-247 percent of the average growing season productivity in the lakes Net plankton (>500 were seldom grazed and since that size fraction and algal mass in general increased with mean productivity and nutrient content in the lakes such decreasing efficiency in food transfer is seen as a major effect of eutrophication

Comparative Primary Productivity of Two Flood Control Reservoirs in the Salt Valley Watershed of Eastern Nebraska

Abstract: Primary productivity, Secchi disc visibility, chlorophyll, and nutrient concentrations were studied in Wagon Train and Stagecoach reservoirs during the years 1969 and 1970. The reservoirs are separated by a distance of only 12 km and are similar in nutrient content and circulation pattern. Furthermore, in both reservoirs 92-100% of the productivity occurs in the upper two meiers. However, the reservoirs differ markedly in their underwater light conditions and, consequently in their primary productivity; Wagon Train Reservoir is turbid due to suspended silt and clay particles while Stagecoach Reservoir lacks this turbidity. During the summer months blue-green algal blooms occur frequently in Stagecoach Reservoir but only rarely in Wagon Train Reservoir. This appears to be due to the rapid attenuation of light by the suspended silt and clay particles. In Wagon Train Reservoir, increased primary productivity is usually associated with increased Secchi disc visibility, while in Stagecoach Reservoir, increased primary productivity is often associated with decreased Secchi depths. Inorganic turbidity is an important factor affecting the productivity of Wagon Train Reservoir while algal production itself determines turbidity in Stagecoach Reservoir. Annual productivity in both study reservoirs, when compared to published values for carbon uptake from other lakes and reservoirs, rates very high. Stagecoach Reservoir fixed 530 g Cjm 2jyear in 1969 and 834 g Cjm 2jyear in 1970. Wagon Train Reservoir increased from 148 g Cjm2jyear in 1969, a year of high inorganic turbidity, to 453 g Cjm 2jyear in 1970, a year of reduced inorganic turbidity.

Primary Production and Limiting Nutrients in a Small, Subalpine Wyoming Lake

Abstract: Primary production and limiting nutrients were studied by 14C techniques in a small, shallow, subalpine lake. There was no relationship between productivity at any depth and light intensity at that depth. Samples taken near the lake bottom always had higher productivity than samples taken near the surface, probably due to more optimal nutrient conditions. Nutrient enrichment experiments support this hypothesis, since sediment extract and ethylenediamine-tetraacetic acid were always effective in enhancing productivity. The effects of other nutrients and nutrient combinations were less consistent, and tended to change through the summer. A large number of significant three, four and five factor interactions in midsummer indicated that the nutrient requirements of the algal community were most complex at this time. Although retention time increased through the summer from 10 to 71 hours, productivity tended to more closely parallel water temperature. Studies of currents showed that the western end o...

Benthic productivity in the Indian Ocean

Abstract: Benthic organisms form an important link in the food chain of organisms at different trophic levels. Between the primary production and the fish production, the role of benthic organisms first as a feeder of detritus and plant material and in turn forming food of some predators like crabs and fishes is now well recognised. This concept of bottom communities received little attention until last three decades. The investigations of Belegvad (1930), Jones (1950, 51 and 56), Sanders (1956) and Mulicki (1957) have thrown new light on the importance of benthic communities. Belegvad (1930) for the first time showed a direct connection between the variations in the quantity of benthic biomass and plaice fishery in the Atlantic region. In the Indian Ocean region the study of benthic productivity was more or less restricted to the inshore areas. In India, Annandale (1907), Panikkar and Aiyar (1937), Sheshappa (1953), Kurian (1955), Desai and Krishnakutty (1967 - a b) and Desai (1971) have discussed the benthic productivity of nearshore areas and Indian continental shelf region. During the Indian Ocean Expedition, the Soviet ship `Vityaz' carried out number of observations on benthic communities and excellent papers on deep sea benthos have been published by Beljaev and Vinogradova (1961) and Sokolova and pasternak (1962). An attempt has been made in this paper to review our present knowledge of benthic productivity in the Indian Ocean and suggest course of action to be undertaken to fill up lacunae and also measures to be taken to increase benthic productivity with an ultimate aim to increase fish yield

Productivity of specialized environments

Abstract: The term productivity here refers to "primary production" or the photosynthetic production of organic carbon in which carbon dioxide is the only source of carbon. This definition easily distinguishes primary production from chemosynthetic uptake of carbon dioxide by microbial flora, where no photosynthesis is involved. Specialized environments are in many ways unique ecosystems and rather specific to a particular region for example the backwaters of Kerala, consisting of a system of monsoonal lagoons and estuaries form such a specialized environment, the equivalent of which is not found anywhere in the world. The specialized environments are unlike the generalized marine ecosystems in which the changes could easily be predicted (Qasim, 1972a). The interest in the study of productivity of specialized environments began in 1965, at the Biological Oceanography Division, NIO, formed a small team of scientists and began studying the backwater around Cochin. Subsequently, in 1968, the study was extended to the atolls of the Laccadives. These studies were continued till 1970. In this communication, the productivity of the following three environments has been summarized: (1) Cochin Backwater (2) Atoll (3) Seagrass bed

Phytoplankton productivity and growth rate kinetics in the cedar river lakes

Abstract: Lakes Findley, Chester Morse and Sammamish, Washington, are characterized by one major outburst of phytoplankton productivity and biomass (mainly diatoms) with usually no or low fall activity. Vernal outbursts were often delayed in the monomictic lakes by inadequate light because of unfavorable climate and/or a lack of thermal stratification. Strong inhibition by light (probably u.v.) was observed in Findley such that average maximum productivity occurred at 10% of surface intensity while maximum was customarily at 60% in the other lakes. Annual productivity was 369C/m2 in Findley, 479C/m2 in Chester Morse and 1989C/m2 in Sammamish. The range in mean chlorophyll a content was 0.8 to 10 ug/,for the same lakes respectively. Although more than three fourths of the productivity in the four lakes was contributed by nanoplankton (5-50u), a tendency for increased contribution from netplankton was observed with increasing trophic state. In vitro experiments during all parts of the growing season show that nitrogen (N) and phosphorus (P) were simultaneously limiting productivity increase in the three lakes. Growth rate kinetics experiments showed increasing half-saturation constants for P (0.17 to 2.8pgP/A) for the natural phytoplankton progressing from oligotrophy to eutrophy. Growth rate models using these parameters were evaluated in Findley Lake subsequent to iceout in 1973. The best agreement was obtained with a model using light (with a function that included inhibition) N and P in contrast to several other combinations of those variables. Light was the most important factor and adaptation problems to low experimental light necessitated increasing the maximum growth rate by a factor of 10 in order to obtain the best agreement with in situ growth rate.

Productivity of the Oceans

Abstract: The ratio of total world fish landings to annual primary production, about 1:3000, suggests a poor exploitation of the biological productivity of the world ocean. The ratio ranges from 1:100 in the most intensively exploited shelf areas and coastal upwelling regions to beyond 1:100,000 in the central oceanic gyres. Regional differences are a thousand-fold higher in fishing yields than in primary production.The yield differences among areas are caused by three groups of factors: 1, Primary production, which is subject to environmental factors; 2, Length, structure, and transfer efficiency of the food chain, which connects the primary producers with the exploited fish population and determines the ratio between fish production and primary production. Wherever primary production is high, the ratio tends to be favorable, particularly in shelf and upwelling areas. The short pelagic food chains of the cold-water regions lead to rich exploitable resources of pelagic fish, whales, and krill; 3, The rate of exploi...

Estimation of production properties of mollusk populations

Abstract: In 8 intermittently reproducing mollusk species, it was possible to estimate production properties on the basis of the population's size-weight structure. The increase in weight of individuals and the variations in the number of individuals per population allow to calculate the annual growth production of a population from quantitative samples obtained at different seasons. A mathematical model was employed to simulate natural production processes of a population. The computor programme yielded estimates of “pure production” in the sense of previous authors, and revealed that 4 samples taken in different seasons are sufficient for determining the average annual production with an error of less than 5%. When the average annual growth production is estimated from a single sampling, the best results are received from analysing a population in the middle of the period during which the young appear. Supporting production (quantity of substances formed and retained by a population within 1 year) secures the dynamic numerical balance in a population of a given age structure. Its Ps/B coefficient (Ps: supporting production; B: biomass) changes only insignificantly within 1 year, and is inversely proportional to the maximum age of individuals prevalent in the population. Related species and species with similar size-weight indices have a similar growth rate and approximately similar growth-curve characteristics. The rate of production is related with the species' thermal properties; different biogeographical groups of species attain their maximum productivity in different seasons. Even in certain parts of the same coastal basin (which differ in their temperature regime), production processes of one and the same species may vary. Seasonal fluctuations in productivity are highest in species with short life cycles and in populations subjected to marked environmental changes. Numerical stability is a constant property of populations as long as the hydrobiological environment does not change significantly over the years. Quantitative relationships between supporting production, biomass and growth production may serve as a measure for assessing the degree of the industrial exploitation of a population.