Uptake Of Organic Material Research Articles

Coastal connectivity and spatial subsidy from a microbial perspective.

The transfer of organic material from one coastal environment to another can increase production in recipient habitats in a process known as spatial subsidy. Microorganisms drive the generation, transformation, and uptake of organic material in shallow coastal environments, but their significance in connecting coastal habitats through spatial subsidies has received limited attention. We address this by presenting a conceptual model of coastal connectivity that focuses on the flow of microbially mediated organic material in key coastal habitats. Our model suggests that it is not the difference in generation rates of organic material between coastal habitats but the amount of organic material assimilated into microbial biomass and respiration that determines the amount of material that can be exported from one coastal environment to another. Further, the flow of organic material across coastal habitats is sensitive to environmental change as this can alter microbial remineralization and respiration rates. Our model highlights microorganisms as an integral part of coastal connectivity and emphasizes the importance of including a microbial perspective in coastal connectivity studies.

Uptake of organic material by aquatic invertebrates. VI. Role of epiflora in apparent uptake of glycine by marine crustaceans

Soft-bodied marine invertebrates from most invertebrate phyla are capable of taking up amino acids from seawater. Marine crustaceans were originally reported not to accumulate amino acids. Artemia salina, Limnoria tripunctata, Tigriopus californicus, and Corophium acherusicum were examined for their ability to accumulate C14-labelled glycine from dilute solution in seawater. In initial experiments with Artemia and Limnoria the organisms were found to become very radioactive. When animals were preincubated in streptomycin or in a mixture of antibiotics, uptake of the C14-glycine was drastically reduced. Microorganisms associated with the arthropods and in the culture media were found capable of accumulating C14-labelled glycine. Efforts to demonstrate removal of amino acids from seawater by colorimeteric determination of material remaining in the medium were unsuccessful. The microorganisms responsible for the uptake are apparently associated with the exoskeleton of the organisms and not the gut. There is probably no substantial contribution to the nutrition of these crustaceans by the epiflora. Preincubation in the antibiotic mixture depressed the uptake of C14-glucose and C14-acetate by about an order of magnitude. It is concluded that there is no evidence for accumulation or assimilation of small organic compounds by the small crustaceans examined.

Uptake of organic material by aquatic invertebrates

Neanthes arenaceodentata (Moore) accumulates glycine −C14 from a dilute solution of seawater. After a 30 min exposure, 5 to 102 times as much radioactivity per unit volume is found in the animals (depending on the size and feeding stage of the worm) as is present in the medium. The relation between the log of cpm and log of weight is linear over 4 orders of magnitude variation in size. The rates of uptake were more variable in non-feeding stages of the life cycle. Non-feeding larvae showed rates of glycine accumulation which were significantly higher than those predicted from data on feeding stages.

Uptake of organic material by aquatic invertebrates. IV. The influence of salinity on the uptake of amino acids by the brittle star, Ophiactis arenosa.

1. The brittle star Ophiactis arenosa shows uptake of C14-labelled glycine, valine, alanine and arginine from dilute solution. The process is linear with time for at least 30 minutes.2. The bulk of the radioactivity accumulated during a 30-minute exposure to glycine-C14 remains in alcohol-soluble form. Autoradiography reveals the radioactivity to be associated with glycine.3. If the animals are allowed to remain in sea water following such an exposure, there is a gradual assimilation of the label into alcohol-insoluble compounds. Some radioactivity appears as C14O2, implying oxidation of the amino acid.4. A double-reciprocal plot of concentration against rate of uptake does not give a straight line. Even at ambient concentrations as high as 10-2 M, the accumulation system apparently is not saturated.5. Common metabolic inhibitors decrease the rate of both accumulation and assimilation.6. The free amino acid pool of Ophiactis in 100% sea water is of the order of 200 mM/kg. body water. In animals subjected ...

Uptake of organic material by aquatic invertebrates—II. Accumulation of amino acids by the bamboo worm, Clymenella torquata

1. 1. The maldanid worm, Clymenella torquata, is capable of removing glycine, lysine, phenylalanine and valine from dilute solution in the surrounding medium. 2. 2. The rate of uptake of these compounds from solutions of the order of 10 −6 moles/l depends on the compounds and is linear with time for at least 30 min. 3. 3. This uptake represents an accumulation of amino acid by the worm since the concentration per unit volume of body water is approximately four to ten times greater than the concentration in the medium after a 15 min exposure to an ambient solution. 4. 4. This process takes place across the body wall and does not require the participation of the digestive tract. Removal or ligation of the head or tail of the organism does not modify the rat of uptake. The rate of uptake under given conditions is an exponential function of the wet weight of the organism. 5. 5. The uptake process for these compounds exhibits kinetics which are similar to those for an enzyme-catalyzed process, indicating that uptake is probably limited by an adsorptive step at higher concentrations. 6. 6. The rate of accumulation of amino acids is independent of the oxygen tension of the medium for periods as long as 24 hr. 7. 7. Radioactivity appears in other compounds in the worms and labeled carbon dioxide can be recovered from the medium. Hence at least a portion of the amino acid taken up from solution enters functional metabolic pools. 8. 8. Samples of interstitial water, from the mud flat where the worms are abundant, were collected and free amino acids were estimated. Five estimates of ninhydrin-positive material in an extract of such samples range from 60 to 104 μmoles/l expressed as amino acid equivalents. An inventory of neutral and acidic amino acids in one sample totalled 74 μmoles/l. 9. 9. The oxygen consumption of Clymenella was measured and found to be 0·09 ml O 2/hr per g wet weight for 100 mg animals. 10. 10. Calculations, based on the amino acid levels found in the environment and the rate of uptake measured in the laboratory indicate that the amino acids obtained by the process under natural conditions may represent a significant supplement to food obtained by other methods.