Showing papers on "Productivity (ecology) published in 1984"

Primary productivity and particle fluxes on a transect of the equator at 153°W in the Pacific Ocean

Abstract: Primary productivity (14C) and mass flux measurements using a free-drifting sediment trap deployed at 900 m were made at four stations in the Pacific Ocean between 12°N and 6°S at 153°W. The latitudinal variations in productivity were consistent with historical patterns showing the equator as a zone of high production and the oligotrophic waters north of the equatorial region as an area of low productivity. The correlation coefficient between the two sets of independent measurements was 0.999, indicating that in this oceanic area the activity of the primary producers was closely related to the total mass flux. A re-examination of historical data suggests that the downward flux of particulate organic carbon varies in direct proportion to the quotient of surface primary production raised to the 1.4 power and depth raised to the 0.63 power.

Significance of biomass and light availability to phytoplankton productivity in San Francisco Bay

Abstract: Primary productivity was measured monthly at 6 sites within San Francisco Bay, USA, throughout 1980. The 6 sites were chosen to represent a range of estuarine environments with respect to salinity, phytoplankton community composition, turbidity, and water depth. Annual net production over the photic zone ranged from 95 to 150 g C m-2, and was highest in regions of lowest turbidity. Daily photic zone net productivity PN,, ranged from 0.05 to 2 .2 g C m-2 d-', and was significantly correlated with the composite parameter B I,/& (where B = phytoplankton biomass; I, = daily surface insolation; E = attenuation coefficient). Lnear regression of PN,, against B Io/€ indicated that most (82 %) of the spatio-temporal variability in primary productivity within this estuary is explained by variations in light availability and phytoplankton biomass. We also calculated annual water-column net productivity PN, as a fraction of annual gross productivity PGx The ratio PN,, : PG, was inversely related to the ratio of water depth H to annual mean photic depth Z,. This linear relation indicates that the watercolumn of San Francisco Bay is a net photosynthetic source of organic carbon only when the ratio H : Z, < 6. In deep turbid habitats, where H : Tp > 6 , respiratory loss exceeds productivity. Thus, 2 empirical formulations allow us to estimate productivity over the photic zone and water column from simple properties that are easily measured.

Nutrient depletion indicates high primary productivity in the Weddell Sea

Abstract: The Southern Ocean, and in particular the Weddell Sea, have long been considered areas of high biological productivity1, but recent isotopic measurements of primary productivity have not confirmed this view2,3. Because the large Zooplankton and marine mammal populations of the Southern Ocean depend ultimately on phytoplankton as the base of the food web, accurate knowledge of primary productivity is essential to our understanding of the Antarctic ecosystem. Oceanographie data collected aboard the Soviet icebreaker Mikhail Somov have allowed us to derive a new productivity estimate, based on the seasonal depletion of nitrate, phosphate and silicic acid in the surface layer. From these depletions and data on the elemental composition of Southern Ocean phytoplankton, we estimate average primary productivity in the Weddell Sea in the springtime to be 220–420 mg C m−2 day−1. Our most conservative estimate is 1.5–4 times higher than recently reported measurements of productivity in the open ocean areas of the Southern Ocean2–5. Our estimates are inherently averages over time and space, including the effects of brief, intense spring blooms of phytoplankton which may occur near the receding ice edge6–8. Studies of primary productivity based on isotope uptake experiments, particularly in the austral summer, may fail to account for the significance of such blooms.

Large yearly production of phytoplankton in the Western bering strait.

Abstract: Production in the western Bering Strait is estimated at 324 grams of carbon per square meter per year over 2.12x 104 square kilometers. An ice-reduced growing season makes this large amount of primary production unexpected, but it is consistent with the area9s large upper trophic level stocks. The productivity is fueled by a cross-shelf flow of nutrient-rich water from the Bering Sea continental slope. This phytoplankton production system from June through September is analogous to a laboratory continuous culture.

Plankton community structure and limnetic primary production

Abstract: A mechanistic, size-structured model was used to analyze effects of grazers on lacustrine primary productivity. Dependence of grazing and nutrient excretion rates on herbivore size, and dependence of algal metabolic rates on cell size, interacted to produce strong responses in primary productivity. Productivity was maximum at intermediate concentrations of chlorophyll and zooplankton biomass. This unimodal response is consistent with data from aquatic systems, terrestrial systems (where the underlying mechanisms are different), and theoretical expectations. Substantial variability in lake productivity (2 to 3 orders of magnitude) exists that cannot be explained by nutrient supply. Food web interactions can regulate herbivorous zooplankton size and abundance, independent of nutrient supply. The resultant variability in herbivory influences nutrient recycling and the size distribution of the phytoplankton, and can alter lake primary productivity by as much as two orders of magnitude.

Cycling of Organic Matter by Bacterioplankton in Pelagic Marine Ecosystems: Microenvironmental Considerations

Abstract: Recently developed methods for measuring production rates of heterotrophic bacteria have shown that the bacterioplankton is a major route for the flux of material and energy in marine ecosystems (Hagstrom et al., 1979; Fuhrman and Azam, 1980, 1982; Williams, 1981). Even conservative estimates (Fuhrman and Azam, 1980, 1982) show that the measured bacterial productivity corresponds to 10–50% of the primary productivity.

Suspended Marine Bacteria as a Food Source

Abstract: During the last decade, evidence has accumulated which undermine the classical picture of planktonic food chains. The general belief was that phytoplankton is consumed by herbivorous zooplankters with an efficiency approaching 100% (Steele, 1976). It has more recently been found that the largest fraction of heterotrophic metabolic activity can be attributed to bacteria rather than to the herbivorous Zooplankton. Studies based on a variety of methods suggest that bacterial biomass has turnover times ranging from <0.5 to a few days and that this represents a production which amounts to 10–30% of the primary production. The reduced carbon sustaining this productivity derives mainly from exudates of phytoplankton cells, but leachates from dead cells and from herbivores as well as detrital material contribute, so that as much as 20–40% of the primary production turns up as dissolved organic matter to be utilized by bacteria (Azam and Hodson, 1977; Hagstrom et al., 1979; Larsson and Hagstrom 1979; Fuhrman et al., 1980; Rheinheimer, 1981; Williams, 1981; Stuart et al., 1982; Wolter, 1982). To this heterotrophic production of bacteria, a photosynthetic production of unicellular cyanobacteria, now known to be an ubiquitous component of plankton, must be added (Sieburth, 1979).

Productivity and utilization of the seagrass Halodule wrightii and its attached epiphytes1

Abstract: Epiphytic algae growing attached to shoalgrass (Halodule wrightii) blades accounted for nearly half of the aboveground live biomass and primary productivity of two seagrass meadows in southern Texas from June-December 1980. They also accounted for the major fraction of recognizable diet material of common seagrass meadow macroinvertebrates, such as grass shrimp (Palaemonetes), crabs (Callinectes), snails (Anachis and Bittium), and amphipods (Cymadusa). Significant shading of seagrass by epiphytes did not appear evident at the light intensities normally encountered by these populations. The passage of Hurricane Allen near the area in early August 1980 did not seem to have a major impact on the seagrass meadow, despite wind gusts of 150 kph and storm tides of+3m.

13C/12C ratios and the trophic importance of algae in Florida Syringodium filiforme seagrass meadows

Abstract: Over 380 stable carbon isotope (δ13C) analyses made during 1981–82 showed that Syringodium filiforme Kutz seagrass meadows in the Indian River lagoon of eastern Florida have food webs based on algal rather than seagrass carbon. Seagrasses averaging approximately-8‰ were isotopically distinct from algae epiphytic on seagrass blades (X=-19.3‰) and particulate organic matter in the water column X=-21.6‰. δ13C values of most fauna ranged between-16 and-22‰, as would be expected if food web carbon were derived solely from algal sources. These results counter the idea that seagrass detritus is the dominant carbon source in seagrass ecosystems. Two factors that may contribute to the low apparent importance of seagrass in the study area are high algal productivities that equal or exceed S. filiforme productivity and the high rates of seagrass leaf export from meadows.

The response of plants to elevated CO2 : II. Competitive interactions among annual plants under varying light and nutrients.

Abstract: Communities, consisting of six co-occurring, disturbed site annuals, were subjected to CO2 unenriched (300 ppm) and to CO2 enriched (450 and 600 ppm) atmospheres at different levels of light and nutrient availability. In general, total community production increased with CO2 enrichment to 450 ppm, but a further increase in CO2 to 600 ppm had little or no effect. The response of community production to CO2 level was not affected by nutrient availability but was affected by light level.Of the six species, four display C3 metabolism. The proportion of total community production contributed by these species increased as a result of CO2 enrichment, and was dependent upon both light and nutrient availability. The relative success of some species, particularly in terms of reproduction (total seed biomass), was significantly altered by CO2 concentration depending on the level of nutrients. There were not only changes in reproductive success (seed biomass) and shoot biomass but also changes in the proportion of biomass allocated to seed.These experiments demonstrate that CO2 enrichment does affect annual plant communities both in terms of productivity and species composition and that the affect of CO2 on such system may depend upon other resources such as light and nutrients.

Utilization of amino acids by planktonic marine bacteria: Importance of clean technique and low substrate additions1,2

Abstract: Rapid turnover of dissolved free amino acids (DFAA) by bacterioplankton in the Gulf of Mexico was observed with techniques designed to eliminate contamination of samples with trace metals and organic compounds. The mean turnover rate of DFAA, based on incorporation of 0.5 nM additions of a mixture of amino acids, was 4.9-d-l for high productivity neritic environments and 1.3.d-’ for low productivity oceanic environments. These rates are faster than those in parallel samples measured by traditional techniques and are consistently faster than previously reported values. Data for multiple level (0.01-7 nM) additions of the mixed substrate were in accord with the Michaelis-Menten enzyme kinetics model. Kinetic parameters derived from this model (V,,,, K, + S,, and R), bacterial cell numbers, and V,,,/cell were highest at photic depths of the neritic zone, intermediate at photic depths of the oceanic zone, and lowest at aphotic depths of the oceanic zone. Estimates of secondary productivity by bacterioplankton (based on V,,,,,) on an equal water volume basis were 6.6 + 1.5% (+-SE, y1 = 5) of the light-saturated primary productivity at the maximum productivity depth. Estimated turnover time of the bacterioplankton community ranged from 2.4 d at 5 m at the highest productivity station to 130 days at 250 m at the lowest productivity

Feeding requirements of krill in relation to food sources

Abstract: During the Melville expedition to the Scotia Sea in January-March 1981, a multidisciplinary team of investigators studied the distribution and biomass of Euphausia superba, in addition to its food resources. The areas studied included five north-south transects of the Scotia Sea (33°–50°W) where krill were relatively sparse, and an area north of Elephant Island where a superswarm of krill was encountered. Krill biomass, determined on samples obtained by paired bongo nets (1 m2), has been used to calculate the minimal daily food requirements for all stages of krill from Calyptopis I to the adult stage. The mean krill biomass in the upper 200 m of the water column in the Scotia Sea (10.6 mg dry weight m–3) would require 0.105–-0.211 mg C m–3 d–1; the corresponding value for krill in the swarm area (270 mg dry weight m–3) was 2.4-5.4 mg C m–3 d-'. The phytoplankton productivity for the upper 200 m in the Scotia Sea and in the swarm area was estimated to be 4.8 and 4.2 mg C m–3 d-', respectively. Our calculations have been concerned mainly with the minimal daily carbon requirements for "maintenance" metabolism. Data of other investigators have been used to compare the total carbon requirement for growth of krill on a seasonal basis. In areas of dense krill aggregations (such as that north of Elephant Island) our calculations indicate that phytoplankton productivity can sustain "maintenance" metabolism by the krill population, but may not provide for full growth of the individuals. Other factors must be invoked here, such as dispersal of the swarm, horizontal movements of the krill along lines of increasing food concentrations, and advection of food resources into the swarm area. Floristic analyses of phytoplankton "in" and "out" of krill swarms suggest that the krill preferentially consume the larger phytoplankton, and leave most of the nannoplankton. Our data from the Scotia Sea indicate that this area is very high in primary production as compared to most other sections of the Antarctic Ocean, and this might be responsible for the high krill biomass reported for this area. The BIOMASS acoustic data set indicates, however, that the greatest krill concentrations exist in the East Indian Ocean (61 mg dry weight m–3), where data indicate that primary production is very low. This anomaly requires further investigation on the relationship of large-scale zones of high primary production in Antarctic waters and their relation to zooplankton biomass.

The sea-surface microlayer: phytoneuston productivity and effects of atmospheric particulate matter

Abstract: The sea-surface microlayer, the upper 50 μm of the ocean surface, provides a habitat for an important biota (the neuston), an interface for exchange of gases between the atmosphere and oceans and a site for deposition of anthropogenic metals and other materials from the atmosphere. Several recent studies have suggested that biochemical processes, including photosynthesis, in the microlayer are inhibited relative to the bulk seawater. We compared the biomass, species composition and productivity of phytoneuston to that of phytoplankton in Sequim Bay, Washington State, USA. Mean enrichment ratios (microlayer: bulk water concentrations) for bacteria, microalgae, chlorophyll pigments and photosynthesis (estimated gross) were 2 444, 380, 12 and 40, respectively. Compared to the bulk water, the microlayer had a unique assemblage of microalgae with a higher concentration of chlorophyll c. When exposed to high light intensities (summer) or metalrich urban atmospheric particulate matter, radiocarbonmeasured photosynthesis was lower in phytoneuston than in phytoplankton. Deposition of atmospheric particulate matter at rates similar to those occurring in urban coastal areas resulted in a significant (P<0.01) reduction in radiocarbon-measured photosynthesis in the sea-surface microlayer. These apparent decreases in photosynthesis are believed to result from the extracellular release of 14C as glycolate or other soluble compounds and may not reflect a true decrease in gross primary productivity in the microlayer. Further measurements of the degree of extracellular carbon release will be necessary to quantify gross photosynthetic rates in the microlayer.

Microplankton productivity in the oligotrophic ocean

Abstract: Uncertainty about the absolute levels of biological productivity over vast tracts of the world's oceans is a fundamental limitation to our understanding of the marine ecosystem1,2. Various workers have sought clarification through a comparison of the fluxes of oxygen and carbon in the photic layer3–5. A re-examination of data4 used to compare short-term (<1 day) in vitro carbon assimilation with long-term (≈100 day) in situ oxygen accumulation at a station in the north central Pacific has shown that the molar fluxes of oxygen and carbon are, in fact, consistent within the resolution of the comparison6. This test, however, is lacking in discrimination7. A recent comparison of short-term in vitro carbon and oxygen fluxes off Hawaii has been interpreted5 as indicating that short-term (≈12h) carbon uptake in open ocean regions provides an unbiased measure of gross primary production, Pg. We show here that comparisons of short-term oxygen- and carbon-flux measurements do not provide a powerful test of the accuracy of either of the measurements, both of which can be biased by trophic interactions in the microplankton. Consideration of trophic interactions, implicit in the reported data5, leads to the important new conclusion that the active biomass of microheterotrophic organisms was large compared with that of autotrophs, a situation which may be generally applicable to the pelagic zone of the open ocean.

Biomass variation and autotrophic production of an epiphyte-macrophyte community in a coastal Danish area: II. Epiphyte species composition, biomass and production

Abstract: A study done at Hvidore in the Oresund, Denmark, in 1979 showed that algae and bacteria occurred on eelgrass leaves throughout the year. Algal species composition, biomass and productivity varied markedly with season, depending on both environmental conditions and growth pattern of the host macrophyte. Bacteria and the diatom Cocconeis scutellum Ehrenberg were pioneer colonizers on young eelgrass leaves. With increasing leaf age several algal species appeared and, in total, 24 algal species were recorded. Species diversity reached a maximum in spring when green and brown macroalgae dominated, while during summer and autumn, microalgae and bacteria dominated. Epiphyte biomass and productivity followed a bimodal pattern with maximum values in April-May and small, secondary maxima in August. The life time of eelgrass leaves ranged between 50 days (summer) and 200 days (winter) and, thus, exposure of the leaf substratum to epiphyte colonization and biomass accumulation varied substantially with seaso...

Variability and productivity of meiobenthos in the Southern Bight of the North Sea

Abstract: The composition and density of meiofauna in the Belgian coastal waters of the North Sea are essentially similar to those over large spatial scales. However, the impact of pollution from the Western Scheidt river is clearly reflected in a decrease in diversity on all taxonomic levels. Nematodes are the only animal group that survives in normal or even greater abundance, albeit it with lower diversity. Total meiofauna production is estimated at 1 . 5 - 2 . 0 g C m-2 yr-1 and equals or even greatly exceeds macrofauna production in the area.

Annual population dynamics and production ecology of Testacea (Protozoa, Rhizopoda) in an aspen woodland soil

Abstract: The population studies of Testacea in an aspen woodland soil revealed 28 taxa of living Testacea, 14 of which were considered constant. The 14 species, while comprising 98 and 96% of the mean annual density and total annual production numbers respectively, accounted for only 80% of the mean annual biomass and 86% of the total annual production biomass. All 14 species had a peak in abundance in autumn, immediately or soon after leaf litter fall. While most species maintained small, active and reproducing populations over the winter period, some maintained higher than normal densities, had seasonal peaks in abundance and biomass, or higher than normal rates of production and turnover. All species had an increase in reproduction and usually in abundance also during the late winter-early spring period before spring thaw. The annual mean weekly density and biomass and the annual production totals tor numbers and biomass were highest in the H layer and lowest in the L. The F layer produced the highest numbers of generations per year and the highest annual mean weekly biomass turnover rate for most of the species. The majority of the periods of high intrinsic rate of natural increase, biomass production and turnover occurred during or after an increase, a decrease or a stabilization in soil moisture content. Mean annual biomass and total annual production were estimated as 0.72 and 206 g wet weight m −2 respectively. The aspen woodland soil Testacea (in a mor humus) had a much higher production and number of generations per year than Testacea from mull and moder humus forms. Total annual ingestion, respiration losses and egestion losses for testate amoebae in an aspen woodland soil were calculated as 1377, 344 and 826 g wet weight of biomass m −2 , respectively. The annual secondary production of Testacea was about 250–300 times the standing crop of Testacea in all the soil layers. The dry weight of carbon respired per year by the Testacea was estimated as 16.2 g m −2 , which amounted to about 6% of the total carbon input.

Effects of two types of nutrient enrichment on the structure and function of contrasting old-field communities.

Abstract: Effects of 4 years of sewage sludge and commercial fertilizer applications on producer and primary consumer populations in a 3-year-old and a 7-year-old field were investigated in 1981. Three 0.1-ha enclosures in each old field received five monthly applications of sludge annually from 1978 through 1981. An equivalent nutrient subsidy in the form of urea-phosphate fertilizer was applied to three enclosures in each old field. Two enclosures in each old field were left untreated as controls. Nutrient enrichment did not significantly increase primary productivity or standing crop biomass in either old field. Species diversity was lower in sludgeand fertilizertreated enclosures in the 3-year-old field. The species composition of both types of nutrient-enriched enclosures became dominated by early successional plants in both old fields. Live trapping of meadow voles indicated that vole population densities were not affected by treatment. Tissue samples of plants and meadow voles were assayed for heavy metal content by atomic absorption spectroscopy. Sludge treatment significantly elevated cadmium, copper, and zinc concentrations in plants and cadmium concentrations in vole livers and kidneys. Voles accumulated cadmium in these organs at levels in excess of plant concentrations, i. e., biological magnification of cadmium occurred. INTRODUCTION Numerous studies have investigated the effects of nutrient enrichment on terrestrial ecosystems. Several researchers (Mellinger and McNaughton, 1975; Kirchner, 1977; Reed, 1977; Bakelaar and Odum, 1978; Magdoff et al., 1980; Willems, 1980) reported increases in net primary productivity in grassland communities following fertilizer application. Kirchner (1977) and Bakelaar and Odum (1978) found species diversity decreased as a result of fertilization. Thus, nutrient enrichment appears to favor high net productivity and low plant species diversity. According to Odum (1969), these structural and functional responses should be characteristic of early successional stages of community development. However, Mellinger and McNaughton (1975) and Bakelaar and Odum (1978) reported increased dominance by later successional species following short-term fertilizer application. Although these studies raise questions about the relationship of nutrient enrichment and succession, there is a paucity of information concerning how contrasting successional communities might differ with respect to the effects of nutrient enrichment on community structure (e.g., plant species diversity and standing crop biomass) and function (e.g., rates of net primary productivity and mammalian reproduction). Recently, there has been considerable interest in municipal sewage sludge as a source of nutrient enrichment (Baker et al., 1979). Sludge disposal has become an increasingly troublesome problem. The application of digested sludge to land as a fertilizer and soil conditioner is an attractive method of disposal. Studies have established that sludge treatment can enhance plant productivity and increase available nutrient levels (e.g., Pomares-Garcia and Pratt, 1978; Magdoff et al., 1980). Application of sludge is not without potential environmental hazards, however. The accumulation of trace elements (e.g., cadmium) in plant tissue and the resultant availability of these elements to the food chain is of ecological concern. Trace element composition of sewage sludge varies with site of origin (Furr et al., 1976). SludgeI Present address: Department of Biology, Virginia Polytechnic Institute and State University, Blacksburg 24061.

Ecology of Indian estuaries—V: Primary productivity of the Ashtamudi estuary, south-west coast of India

Abstract: Primary productivity at four representative stations in the Ashtamudi estuary has been presented. The average gross and net productivities in the surface water was maximum at Neendakara, the bar mouth zone and minimum at Kadapuzha, the riverine zone consistently exposed to pollution from paper mill effluents. Ashtamudi, the station directly on the gradient line and Kanjirakode, the station equidistant from Kadapuzha and Ashtamudi presented a transition phase with regard to the primary productivity. In the bottom water also productivity was minimum at the polluted zone. Generally productivity at sub-surface levels was higher than that at the surface. A seasonal pattern, independent of various environmental parameters, was discernible both in the gross and net productivity changes at surface and sub-surface levels. High concentrations of dissolved oxygen, silicate and nitrite helped to maintain higher productivities at Neendakara, Ashtamudi and Kanjirakode on several occasions during the year. The fact that productivity at the polluted Kadapuzha station was the lowest, indicates that the paper mill effluent has considerably disturbed the productivity mechanism of this otherwise healthy ecosystem.

Nutrient concentrations and primary productivity at the Peros Banhos and Salomon atolls in the Chagos Archipelago

Abstract: Coral atolls are areas of high biological productivity even though they are usually located in regions of the tropical ocean characterized by low primary production and extremely low levels of vital dissolved nutrient materials. Recent studies have indicated the possible importance of in situ dinitrogen fixation on shallow reef flats in supplementing low oceanic nitrate levels and thus contributing to the maintenance of high reef productivity. Variations in the structure of atolls may have a direct bearing on the accumulation of fixed nitrogen and other nutrient materials, and consequently on lagoonal and reefal primary productivity. This paper investigates the effect of differing atoll configurations by comparing neighbouring, but structurally dissimilar, mid-ocean atolls. The findings are discussed in terms of ecosystem function and possible influences on the structural evolution of atolls.