The role of epiphytic and epibenthic algal productivity in a tropical seagrass, Syringodium isoetifolium (Aschers.) Dandy, community

1993 ◽  
Vol 44 (1) ◽  
pp. 141 ◽  
Author(s):  
PC Pollard ◽  
K Kogure
Keyword(s):  
Algal Community ◽  
Sediment Surface ◽  
Leaf Production ◽  
Net Productivity ◽  
Multidisciplinary Study ◽  
Bare Sediment ◽  
Carbon Transfer ◽  
Algal Productivity ◽  
Syringodium Isoetifolium

The overall aim of this study, which was part of a multidisciplinary investigation, was to evaluate the role of epiphytic and epibenthic algae in a tropical seagrass, Syringodium isoetifoliurn (Aschers.) Dandy, community. Algal biomass (chlorophyll a) and productivity were determined over 20 days. The rates of photosynthesis were measured with both gas (oxygen) release and H14CO3 incorporation techniques. The photosynthetic characteristics of the algal community are described by the relationship between the rates of photosynthesis and irradiance (PI curve). The saturating light intensity (Ik), determined in the laboratory, was 240 �E m-2 s-1 (1 �E= 1 �mol). However, the maximum rate of net epibenthic production (Pmax) in situ of 2 g C g chla-1.h-1 was reached only at light intensities above the leaf canopy of more than 480 �E m-2 s-1 because of shading. The photoperiod (the period when algae were at Pmax was determined from the daily light profiles and used to calculate the mean net productivity of the epibenthic (4.2 g C m-2 day-1) and epiphytic (11.5 g C m-2 day-1.) algae during the study. The net epiphytic and seagrass productivities were equal and positively correlated (slope = 1.0; r2 = 0.92). However, the net seagrass leaf production was only 25% of the total seagrass net production. Most of the seagrass production appeared to be directed elsewhere, possibly into the below-ground tissue. Epiphytic algae accounted for more than four times the above-ground primary production. Compared with the bare sediment surface, the dense seagrass stand afforded 27�4 (s.d.) times more surface area on which the epiphyton could colonize. Thus, seagrasses provided the surfaces essential for maintaining the substantial epiphytic primary productivity, a passive but nonetheless important role. We compare our findings with other results of the multidisciplinary study and construct a carbon budget from which we infer a model of carbon transfer through this ecosystem. The algae were quantitatively the most important of the primary producers, seeming to provide most of the organic carbon to the higher trophic groups, at least for the period of this study.

Bacterial decomposition of detritus in a tropical seagrass (Syringodium isoetifolium) ecosystem, measured with (Methyl- super-3H)thymidine

1993 ◽  
Vol 44 (1) ◽  
pp. 155 ◽  
Author(s):  
PC Pollard ◽  
K Kogure
Keyword(s):  
Organic Carbon ◽  
Bacterial Activity ◽  
Sediment Surface ◽  
Minor Role ◽  
Bacterial Productivity ◽  
Decomposition Of Organic Matter ◽  
Bacterial Decomposition ◽  
Algal Productivity ◽  
Syringodium Isoetifolium ◽  
A Minor

The bacterial decomposition of detritus was measured in a tropical seagrass meadow (Syringodium isoetifolium) off Dravuni Island, Fiji, and compared with the seagrass and algal productivity. Our estimates of bacterial decomposition of organic matter was based on the rate at which the bacteria divided, and this was measured by the rate at which [methyl-3H]thymidine was incorporated into the bacterial DNA. Bacterial activity was greatest in the top 1 cm of the seagrass sediments. The number of bacteria, their specific growth rate, and their productivity were 6.3 � 0.3 × 109 cells cm-3 , 0.04� 0.005 h-1, and 0.671 g C day-1 m-2 (depth-integrated over 30 cm), respectively. At the sediment surface, bacterial activity coincided with the daily light intensities during the day. Benthic microalgal production seemd to be coupled to the heterotrophic bacterial activity. However, the amount of organic carbon passing through the bacterial decomposition process was small compared with the total autotrophic production. The net bacterial productivity was only between 4 and 6% of that of microalgae and 6% of that of the seagrass. The bacteria appeared to play a minor role in the transfer of organic carbon between the primary producers and the higher trophic groups. Much of the microalgal production could have been directly consumed by the benthic infauna, whereas the seagrass production may have been translocated, via the seagrass roots and rhizomes, to other parts of the plant and/or converted into more refractory or storage compounds.

Multiple interactions in riverine biofilms - surfactant adsorption, bacterial attachment and biodegradation

1995 ◽  
Vol 31 (1) ◽  
pp. 61-70 ◽  
Author(s):  
Graham F. White
Keyword(s):  
Organic Pollutants ◽  
Bacterial Attachment ◽  
Solid Surfaces ◽  
Sediment Surface ◽  
Liquid Interfaces ◽  
Polluted Soils ◽  
Biofilm Bacteria ◽  
The Impact ◽  
Multiple Interactions

Many organic pollutants, especially synthetic surfactants, adsorb onto solid surfaces in natural and engineered aquatic environments. Biofilm bacteria on such surfaces make major contributions to microbial heterotrophic activity and biodegradation of organic pollutants. This paper reviews evidence for multiple interactions between surfactants, biodegradative bacteria, and sediment-liquid interfaces. Biodegradable surfactants e.g. SDS, added to a river-water microcosm were rapidly adsorb to sediment surface and stimulated the indigenous bacteria to attach to the sediment particles. Recalcitrant surfactants and non-surfactant organic nutrients did not stimulate attachment Attachment of bacteria was maximal when biodegradation was fastest, and was reversed when biodegradation was complete. Dodecanol, the primary product of SDS-biodegradation, markedly stimulated attachment. When SDS was added to suspensions containing sediment and either known degraders or known non-degraders, only the degraders became attached, and attachment accelerated surfactant biodegradation to dodecanol. These cyclical cooperative interactions have implications for the design of biodegradability-tests, the impact of surfactant adjuvants on biodegradability of herbicides/pesticides formulated with surfactants, and the role of surfactants used to accelerate bioremediation of hydrocarbon-polluted soils.

Protozoa abundance, growth, and bacterivory in the water column, on sedimenting particles, and in the sediment of Halifax Harbor

1990 ◽  
Vol 36 (12) ◽  
pp. 859-863 ◽  
Author(s):  
James A. Novitsky
Keyword(s):  
Bacterial Community ◽  
Water Column ◽  
Sediment Surface ◽  
Metabolic Inhibitor ◽  
Optimum Conditions ◽  
Bacterial Populations ◽  
Protozoan Grazing ◽  
Large Numbers ◽  
Doubling Times

The role of protozoan grazing in controlling bacterial populations was examined in four microbial habitats in Halifax Harbor, Canada: the water column, setting particles, the sediment–water interface, and the sediment. Large numbers of protozoans were found in all habitats although most (>56%) were small (<5 μm) flagellates. Protozoans larger than 10 μm were rarely observed; protozoans >20 μm were never observed. Protozoans were also observed to a depth of 9 cm below the sediment surface although efforts to culture viable protozoa failed except for the top 1 cm. The use of the metabolic inhibitor cycloheximide with and without colchicine to selectively inhibit eucaryotic metabolism was shown to severely affect procaryotic metabolism in sediment (and presumably particle and water) samples. Using fluorescently labelled bacteria as food, and under optimum conditions, up to 42% of the Protozoa population exhibited active grazing within 7 h. Using protozoan and bacterial community sizes and doubling times, it was calculated that each protozoan in Halifax Harbor would have to consume 13–118 bacteria per hour for the enumerated nanoplanktonic (<20 μm) Protozoa to be the sole control of the size of the bacterial community. Key words: marine, Protozoa, bacterivory, particles, bacteria.

scholarly journals Functional Ecology of Iceplant Taxa and Their Role in Eco-restoration of New Zealand Sand Dunes

2021 ◽  
Author(s):  
◽  
Guyo Duba Gufu
Keyword(s):  
New Zealand ◽  
Plant Species ◽  
Plant Communities ◽  
Growth Rates ◽  
Sand Dunes ◽  
Intergeneric Hybrid ◽  
Leaf Production ◽  
Natural Plant ◽  
Carpobrotus Edulis

<p>Biological invasion by non-native plant species has often been cited as a cause of native biodiversity loss. While the outcome of species invasions depends on interactions between exotic and resident native species, most studies of biological invasions have focused solely on the direct negative impacts of non-indigenous species on native biota. Although investigations of the role of competition in shaping natural plant communities were dominant in the previous generations and are still popular, more recent experimental research has uncovered the striking influence of facilitation on community dynamics. This thesis aims to investigate competitive and facilitative influence of the invasive South African iceplant (Carpobrotus edulis) on Spinifex sericeus, a native foredune grass species, with particular reference to implications of these interactions for dune restoration in New Zealand. It further explores the growth rates, substrate preferences and mating systems of the exotic and native iceplant taxa found in New Zealand. I begin by briefly outlining the influence of competition and facilitation on natural plant communities with reference to the role of facilitation in eco-restoration. I also give a few examples where exotic species have been found to facilitate native ones. Secondly, a neighbour removal experiment was conducted on coastal sand dunes with the main aim of studying the effects of Carpobrotus edulis on establishment of Spinifex sericeus at the foredune region. Finally, I compared the growth rates of the most widely distributed iceplant taxa in New Zealand in different substrates and the breeding systems of the exotic Carpobrotus.  Examples abound in literature of exotic plant species facilitating native ones especially in forestry. In the neighbour removal study, Carpobrotus edulis protected Spinifex seedlings against storm erosion, sandblasting and salt sprays while at the same time suppressing its leaf production. Suppression of Spinifex leaf production was more pronounced at top of the dune where stress elements is presumably more benign. There was no evidence of allelopathic suppression of Spinifex by C. edulis. Only Carpobrotus chilensis displayed some level of substrate preference by putting on relatively lower biomass in gravel. The exotic Carpobrotus spp. put on greater dry matter content than the native Disphyma australe and the Carpobrotus-x-Disphyma hybrid. The hybrid displayed a faster vegetative growth rate whereas D. australe allocated relatively more biomass to the roots than the shoot. Both Carpobrotus spp. are self compatible and highly capable of intrageneric and intergeneric hybridisation. Mass removal of the existing exotic iceplant stands from foredunes along high energy coasts is not advisable as they serve as useful stabilisers. The intergeneric hybrid is sexually sterile with sparsely spread stolons that could allow co-occurrence with other species and therefore is more suitable for foredune stabilisation. However, more research needs to be conducted on the ecology of the intergeneric hybrid.</p>

scholarly journals Oxycline oscillations induced by internal waves in deep Lake Iseo

2018 ◽  
Author(s):  
Giulia Valerio ◽  
Marco Pilotti ◽  
Maximilian Peter Lau ◽  
Michael Hupfer
Keyword(s):  
Internal Waves ◽  
Water Layer ◽  
Sediment Surface ◽  
Chemical Gradient ◽  
Deep Lakes ◽  
Deep Lake ◽  
Deep Waters ◽  
Basin Scale ◽  
First Time

Abstract. Lake Iseo is undergoing a dramatic de-oxygenation of the hypolimnion, representing an emblematic example among the deep lakes of the prealpine area that are, to a different extent, suffering from reduced deep water mixing. In the anoxic deep waters, the release and accumulation of reduced substances and phosphorus from the sediments is a major concern. Since the hydrodynamics of this lake was shown to be dominated by internal waves, in this study we investigate for the first time the role of these oscillatory motions on the vertical fluctuations of the oxycline, currently situated at a depth of around 95 m, where a permanent chemocline inhibits deep mixing by convection. Temperature and dissolved oxygen data measured at moored stations show large and periodic oscillations of the oxycline, with amplitude up to 20 m and periods ranging from 1 to 4 days. A deep dynamics characterized by larger amplitudes at lower frequencies is shown to be favoured by the excitation of second vertical modes in strongly thermally stratified periods and of first vertical modes in weakly thermally stratified periods, when the deep chemical gradient can support baroclinicity anyhow. These basin-scale internal waves cause in the water layer between 85 and 105 m depth a fluctuation of the oxygen concentration between 0 and 3 mg L−1 that, due to the bathymetry of the lake, changes the redox condition at the sediment surface. This forcing, involving about 3 % of the lake's sediment area, can have major implications for the biogeochemical processes at the sediment water interface and for the internal matter cycle.

Two Classics: Böhm-Bawerk's Positive Theory and Fisher's Rate of Interest Through Modern Prisms

1994 ◽  
Vol 16 (2) ◽  
pp. 202-228 ◽  
Author(s):  
Paul A. Samuelson
Keyword(s):  
Interest Rate ◽  
Time Preference ◽  
Positive Theory ◽  
Interest Theory ◽  
Net Productivity ◽  
The Interest Rate

Positive Theory of Capital (1889) is a classic which contains Eugen von Böhm-Bawerk's 1889 correct vision of how the interest rate might be determined by the interplay of systematic time preference (“impatience”) and time-phased technology's productivity. But he was not quite able to formulate his intuitive vision in terms that would satisfy today's persnickety jury of theorists. And indeed the classic Rate of Interest (1907) by his younger contemporary, Irving Fisher, seemed to be disagreeing with Böhm-Bawerk's treatment of time's net productivity; but, as Fisher was unable to make clear until 1930, he was objecting only to Böhm-Bawerk's formulation of the role of productivity in interest determination. In point of fact, Fisher, who was so long identified (wrongly, but understandably) as an “impatience theorist,” considered his own main contribution to interest theory to be his clarification of how the technological superiority of time-consuming processes cooperated in the determination of the equilibrium interest rate.

Réponses comportementales des polychètes Nereis diversicolor (O.F. Müller) et Nereis virens (Sars) aux stimuli d'ordre alimentaire : utilisation de la matière organique particulaire (algues et halophytes)

1995 ◽  
Vol 73 (12) ◽  
pp. 2307-2317 ◽  
Author(s):  
Marc Olivier ◽  
Gaston Desrosiers ◽  
Alain Caron ◽  
Christian Retière ◽  
Aline Caillou
Keyword(s):  
Potential Role ◽  
Time Budget ◽  
Sediment Surface ◽  
Lawrence Estuary ◽  
Nereis Diversicolor ◽  
Nereis Virens ◽  
Intertidal Ecosystem ◽  
Feeding Area ◽  
St Lawrence Estuary

Plant preference and feeding selectivity were studied in juveniles of Nereis diversicolor O.F. Müller) and Nereis virens (Sars) (Polychaeta: Nereidae) to evaluate the potential role of these species in the integration and transfer of vegetal debris to the littoral ecosystem. Results show that these annelids ingest the main plant species (algae and halophytes) that are abundant in the marshes of the bay of Mont-Saint-Michel (France) and (or) the À l'Orignal Inlet (St. Lawrence Estuary, Canada), independently of their origin or level of decomposition. Juveniles select detritus on the sediment surface (feeding area) and accumulate them in their burrow. Constant irrigation by young individuals (≈35% of time budget) maintains aerobic conditions favouring the decay process of plant debris by stimulating bacterial growth (gardening). Our results suggest that individuals of both N. diversicolor and N. virens play an important role in the transfer and integration processes and the residence time of vegetal detritus of the intertidal ecosystem.

scholarly journals Measuring the role of seagrasses in regulating sediment surface elevation

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Maria Potouroglou ◽  
James C. Bull ◽  
Ken W. Krauss ◽  
Hilary A. Kennedy ◽  
Marco Fusi ◽  
...  
Keyword(s):  
Surface Elevation ◽  
Sediment Surface

The effects of methylprednisolone and diabetes on the turnover of alanine and on the transfer of carbon atoms from alanine to pyruvate and glucose in dogs

1980 ◽  
Vol 58 (7) ◽  
pp. 787-796 ◽  
Author(s):  
G. Hetenyi Jr. ◽  
B. Pagurek ◽  
Elizabeth A. Dittmar ◽  
Catherine Ferrarotto
Keyword(s):  
Plasma Level ◽  
Plasma Glucose ◽  
Turnover Rate ◽  
Glucose Turnover ◽  
Direct Proportion ◽  
Carbon Transfer ◽  
Tracer Methods ◽  
Pancreatectomized Dogs

The turnover rate of glucose, the irreversible disposal rate of alanine, and the transfer of carbon atoms from alanine to glucose were studied with the help of tracer methods in normal, methylprednisolone (MP) treated and pancreatectomized dogs. The incorporation of carbon from alanine into pyruvate was also followed. In comparison with normal dogs, in MP-treated dogs the plasma level of alanine and pyruvate were elevated by a factor of about 3 whereas the level of plasma glucose was increased by 10%. Both the turnover rate of glucose and the irreversible disposal rate of alanine were significantly higher. In pancreatectomized dogs plasma alanine and pyruvate levels were not different from normal. There was no increase in the irreversible disposal rate of alanine. Glucose turnover was about twice as much as in normals. The transfer of C atoms from alanine to glucose was increased in both MP-treated and pancreatectomized dogs. The increase was in direct proportion to the increase in the irreversible disposal rate of alanine in MP-treated dogs whereas in pancreatectomized dogs it was due to an increased fraction of the irreversible disposal rate of alanine being converted to circulating glucose. Thus two different mechanisms are responsible for the increased carbon transfer and hence presumably gluconeogenesis in MP-treated and in pancreatectomized animals. The role of insulin as the determinant of the preferred route to increase gluconeogenesis is discussed.

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