Particulate Organic Nutrients Research Articles

Bioavailability of Organic Phosphorus Compounds to the Harmful Dinoflagellate Karenia mikimotoi.

Karenia mikimotoi is one of the most well-known harmful bloom species in temperate coastal waters. The present study investigated the characteristics of alkaline phosphatase (APase) and phosphodiesterase (PDEase) activities in hydrolysis of two phosphomonoesters (adenosine triphosphate (ATP) and ribulose 5-phosphate (R5P)) and a phosphodiester (cyclic adenosine monophosphate (cAMP)) in K. mikimotoi and compared its growth and physiological responses to the different forms of phosphorus substrates. K. mikimotoi produced comparable quantities of APase and PDEase to hydrolyze the organic phosphorus substrates, although hydrolysis of the phosphomonoesters was much faster than that of the phosphodiester. The growth of K. mikimotoi on organic phosphorus substrates was comparable to or better than that on inorganic phosphate. The difference in particulate organic nutrients (carbon, nitrogen, and phosphorus) and hemolytic activity supported different rates of hydrolysis-assimilation of the various organic phosphorus substrates by K. mikimotoi. The hemolytic activities of K. mikimotoi in the presence of organic phosphorus substrates were several times those in the presence of inorganic phosphate during the exponential phase. This suggested the potential important role of organic phosphorus in K. mikimotoi blooms.

Ecological study of the aquatic carnivorous plant Utricularia australis R.Br. (Lentibulariaceae)

Utricularia australis is an aquatic rootless carnivorous plant that takes up nutrients through shoots or from trapped prey digested in its bladders. As the information on the ecology of this species is scarce, the main environmental factors which favour or limit its growth were analysed. Habitat characterization was carried out on 23 aquatic sites in Central Italy where U. australis occurred. Diverse water chemical and physical factors and aquatic plant dominants were sampled and compared to Utricularia coverage. Species response curves with respect to each analysed ecological factor were elaborated. Despite the large environmental variation among sites, U. australis did show some ecological preferences. Optimal growth of Utricularia was associated with sunny sites (~ 1500 µmol photon m−2 s−1) and shallow waters (< 20 cm) that were warm (~ 26 °C), alkaline (pH 8.3 median value), with moderate-high conductivity (700 µS cm−1) and with low aquatic inorganic phosphorus (< 10 µg L−1) but higher nitrogen (800–1600 µg L−1). Dissolved and particulate organic nutrients (mainly phosphorus) were highly important in determining U. australis ecology and its distribution. The knowing of the ecological preferences of U. australis, a plant that is becoming increasingly rare in Central Italy, could be very useful to identify and protect its habitats or to identify new potential sites and to avoid further population losses.

The impact of reservoir construction on riverine sediment and carbon fluxes to the Mediterranean Sea

Riverine suspended particulate matter (SPM) is an important vector for the transfer of nutrients and contaminants to the Sea. Mediterranean rivers are naturally rich in SPM, but their fluxes have been largely altered in the past decades because of damming. Based on empirical modeling, combining literature estimates on SPM fluxes with the environmental characteristics of the corresponding drainage basins, we present for the first time a spatially explicit quantification of the natural fluxes at the level of the Mediterranean Sea and its different sub-basins. These fluxes are further combined with the evolution of major reservoir constructions during the last century in order to quantify the sediment retention by dams. Our results confirm that natural riverine sediment fluxes generally result from a combination of hydroclimatic, geomorphologic and land use parameters in the corresponding drainage basin. Among these factors, the combination of lithology and land elevation appears to be a key factor in the control of mechanical erosion rates. According to our model, the natural flux of SPM by all Mediterranean rivers cumulates to about 997Mtyr−1, which corresponds to a specific SPM flux of 211tkm−2yr−1. Besides the Nile River, which holds a particular place among the Mediterranean rivers, coastal rivers (<5000km2) are particularly important for the overall SPM transport. Although they only occupy 38% of the Mediterranean drainage basin area, they export about 58% of the natural SPM flux. We further quantified the potential impact of damming on these fluxes. Using the dams which are geolocalized in the global GRandD data base, and combining them with a high resolution (5′) river routing scheme developed in this study, we find that after 2003, about 35% of the river sediments are retained by dams (26% without the Nile). These values are clearly minimum values, since GRandD is far from being complete in the Mediterranean drainage basin. According to our simulations, about 22% of the storage capacity is currently lost in these dams, and about 30% of them have a life expectancy that does not exceed 200years. We finally also combined our modeling with a global model for the fluxes of particulate organic carbon (POC), representative for particulate organic nutrients in general. Although POC is non-linearly coupled to the fluxes of SPM, our results show that the retention of POC in dams is almost identical to the retention of sediments.

Genetic diversity affects ecological performance and stress response of marine diatom populations.

Genetic diversity is considered an important factor, stabilizing ecological functions when organisms are faced with changing environmental conditions. Although well known from terrestrial systems, documentations of this relationship from marine organisms, and particularly planktonic microorganisms, are still limited. Here we experimentally tested the effects of genotypic diversity on ecologically relevant cellular parameters (growth, primary production, particulate organic carbon, particulate organic nitrogen, particulate organic phosphorus and biogenic silica) at optimal and suboptimal salinity conditions in a marine phytoplankton species. Multiple clonal genotyped and phenotypically characterized isolates of the diatom Skeletonema marinoi from the Baltic Sea were grown in monocultures and mixes of 5 and 20 clones at native (5 psu) and reduced (3 psu) salinities and respective parameters were compared. Re-genotyping of 30 individuals from each population at five microsatellite loci at the end of the experiment confirmed maintenance of genotypic richness. Although a diversity effect on growth was not detected, primary production and particulate organic nutrients were positively affected by increased diversity independent of salinity condition. Under salinity stress, highest values of primary production and particulate organic nitrogen content were measured at the high diversity level. The observed diversity effects emphasize the importance of genetic diversity of phytoplankton populations for ecological functions.

Bioinfiltration: Irrigation-Driven Transport of Clay Particles Through Bioturbated Sediments

Abstract The transport of clay-size particles into the pore networks of siliciclastic sediments by the bioirrigating activities of burrowing organisms is demonstrated here for the first time. In a laboratory microcosm, evidence for the advection of kaolinite particles into pore spaces was observed at the interface between two buried sand layers. The clay transport was caused by the burrow-irrigating behavior of the mud shrimp Upogebia pugettensis. The term “bioinfiltration” is introduced herein to describe the process of particulate transport into pore-water networks. Given the abundance of bioirrigating organisms in shallow-marine environments, bioinfiltration may be a widespread phenomenon affecting the properties of large sediment volumes. The introduction of clay mineral particles into otherwise clay-free sediments through bioirrigation would affect the sediment characteristics significantly. In particular, bioinfiltrated clays would occlude pore space, could act as precursors to the production of authigenic cements, and inhibit the growth of quartz cements—all of which would reduce the permeability and porosity of hydrocarbon reservoirs and groundwater aquifers. Bioinfiltration therefore needs to be considered when assessing the origins and diagenetic effects of clay particles in bioturbated sediments, and is likely also to be of significance to sediment biogeochemistry and infaunal ecology. This is because of the potential influence of sedimentary pore occlusion on pore-water exchange, and through the introduction of particulate organic nutrients into the sediment as flocs or colloids. Such changes are likely to affect microbial productivity, which is thought to be the food source of many burrowing micro- and macro-organisms.

Nutrient Uptake and Mineralization during Leaf Decay in Streams – a Model Simulation

AbstractWe developed a stoichiometrically explicit computer model to examine how heterotrophic uptake of nutrients and microbial mineralization occurring during the decay of leaves in streams may be important in modifying nutrient concentrations. The simulations showed that microbial uptake can substantially decrease stream nutrient concentrations during the initial phases of decomposition, while mineralization may produce increases in concentrations during later stages of decomposition. The simulations also showed that initial nutrient content of the leaves can affect the stream nutrient concentration dynamics and determine whether nitrogen or phosphorus is the limiting nutrient. Finally, the simulations suggest a net retention (uptake &gt; mineralization) of nutrients in headwater streams, which is balanced by export of particulate organic nutrients to downstream reaches. Published studies support the conclusion that uptake can substantially change stream nutrient concentrations. On the other hand, there is little published evidence that mineralization also affects nutrient concentrations. Also, there is little information on direct microbial utilization of nutrients contained in the decaying leaves themselves. Our results suggest several directions for research that will improve our understanding of the complex relationship between leaf decay and nutrient dynamics in streams. (© 2009 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Effects of the zebra mussel, an exotic freshwater species, on seston stoichiometry

We examined the effect of the zebra mussel, Dreissena polymorpha, an exotic species, on seston stoichiometry by conducting laboratory experiments in which we varied nutrient composition of seston and mussels over time. Zebra mussels altered the stoichiometry of seston through removal of particulate organic nutrients and changed the stoichiometry of the dissolved nutrient pool through nutrient excretion. Grazers had stronger effects on carbon : phosphorus (C : P) and nitrogen (N) : P ratios than on the C:N ratio of seston. Elemental residence time in tissue and high mass‐specific nutrient excretion by small mussels caused small mussels to be more efficient nutrient recyclers than larger mussels. Zebra mussels reduced P availability through enhancing C: P and N: P molar ratios of seston during the period extending from June to August, when P was limited in the lake, and increased the C:N molar ratio of seston in June, when N was at the minimum level in the lake. C: P and N: P molar ratios for zebra mussel tissue were higher in August and somewhat in September than in all other months. N was retained more efficiently than P in Dreissena tissue. Nutrient mass‐specific uptake rate was higher than excretion rate by zebra mussels.

Is inorganic nutrient enrichment a driving force for the formation of red tides?: A case study of the dinoflagellate Scrippsiella trochoidea in an embayment

Red tides (high biomass phytoplankton blooms) have frequently occurred in Hong Kong waters, but most red tides occurred in waters which are not very eutrophic. For example, Port Shelter, a semi-enclosed bay in the northeast of Hong Kong, is one of hot spots for red tides. Concentrations of ambient inorganic nutrients (e.g. N, P), are not high enough to form the high biomass of chlorophyll a (chl a) in a red tide when chl a is converted to its particulate organic nutrient (N) (which should equal the inorganic nutrient, N). When a red tide of the dinoflagellate Scrippsiella trochoidea occurred in the bay, we found that the red tide patch along the shore had a high cell density of 15,000 cells ml −1, and high chl a (56 μg l −1), and pH reached 8.6 at the surface (8.2 at the bottom), indicating active photosynthesis in situ. Ambient inorganic nutrients (NO 3, PO 4, SiO 4, and NH 4) were all low in the waters and deep waters surrounding the red tide patch, suggesting that the nutrients were not high enough to support the high chl a >50 μg l −1 in the red tide. Nutrient addition experiments showed that the addition of all of the inorganic nutrients to a non-red-tide water sample containing low concentrations of Scrippsiella trochoidea did not produce cell density of Scrippsiella trochoidea as high as in the red tide patch, suggesting that nutrients were not an initializing factor for this red tide. During the incubation of the red tide water sample without any nutrient addition, the phytoplankton biomass decreased gradually over 9 days. However, with a N addition, the phytoplankton biomass increased steadily until day 7, which suggested that nitrogen addition was able to sustain the high biomass of the red tide for a week with and without nutrients. In contrast, the red tide in the bay disappeared on the sampling day when the wind direction changed. These results indicated that initiation, maintenance and disappearance of the dinoflagellate Scrippsiella trochoidea red tide in the bay were not directly driven by changes in nutrients. Therefore, how nutrients are linked to the formation of red tides in coastal waters need to be further examined, particularly in relation to dissolved organic nutrients.

Scaling of nutrient inputs to submersed plant communities:temporal and spatial variations

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 152:89-102 (1997) - doi:10.3354/meps152089 Scaling of nutrient inputs to submersed plant communities: temporal and spatial variations Sturgis RB, Murray L Experiments were designed to test the hypothesis that the response of a submersed plant community will differ with varying form, mode and timing of nutrient delivery. Two separate experiments were conducted in summer-fall 1993 and spring-summer 1994; each ran for a period of 12 wk. Dissolved and particulate forms of nutrient additions were made to 10l microcosms containing a submersed vascular plant species (Potamogeton perfoliatus L.) formally abundant in brackish waters of the Chesapeake Bay, USA. Nutrients in the pulse treatments were added to each of 4 replicate chambers weekly in fall and bi-weekly in spring, while continuous inputs were administered via a peristaltic pump. Additions were made at a moderate loading rate of 38 µmol N l -1d-1 in both spring-summer and summer-fall experiments, and at a high loading rate of 5 times higher in spring-summer. Phosphorus was added to result in a 10:1 atomic N:P ratio. Results from the experiments involving moderate enrichment with dissolved nutrients indicate that water column concentrations remained low (1 to 2 µmol), while enrichment at the high levels exhibited an increase in concentrations over controls. Plant growth and biomass decreased with both moderate and high dissolved nutrient treatments, while morphological parameters also indicated plant stress. Algal concentrations, particularly epiphytes, increased with experimental treatment. Both plant and microalgal C:N ratios decreased with nutrient enrichment. In summer-fall, particulate organic nutrient (PON) enrichment at moderate levels resulted in a stimulation of plant growth in comparison to control. In spring-summer, PON enrichment resulted in initial stimulation of growth, followed by a decline. Total ecosystem production (Pa) and respiration (Rn) increased in experimental chambers. A nitrogen budget indicates a redirection of nutrients from plant biomass to algal biomass in the nutrient enriched systems. A seasonal comparison is made between the results from the summer-fall and spring-summer experiments. The relationship between water quality parameters in experimental chambers and established submersed plant habitat criteria is discussed. Submersed aquatic vegetation · Mesocosms · Nutrient enrichment Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 152. Publication date: June 26, 1997 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1997 Inter-Research.

A link between biologically imported particulate organic nutrients and the detritus food web in reef communities

Previous work with planktivorous fishes has shown that they import particulate organic and inorganic material to reefs in the form of fecal pellets, which, in part, are deposited in crevices on the reef where these fishes shelter during their inactive period. Since these feces do not accumulate in fish shelters, we predicted that some of the feces could be rapidly consumed by reef detritivores. We examined the attractiveness of fish feces to potential reef detritivores by placing traps baited with planktivorous fish feces, along with unbaited control traps, in crevices on rocky reefs at Santa Catalina Island, California, USA, between June 1982 and November 1983, and on coral reefs at St. Croix, U.S. Virgin Islands, during June 1983. Significantly more animals (the majority being crustaceans) were trapped in the baited traps compared to the unbaited controls on both reefs. There was also a significant association between the presence of trapped animals and fish feces at Santa Catalina Island (p = 0.009); this association was not quite as strong in St. Croix (p = 0.069). The consumption by shrimp of feces marked with carmine particles and, in turn, the predation on these shrimp by a reef fish demonstrates the links between this type of imported particulate organic and inorganic material and the food web of the reef community.