Release Of Inorganic Nutrients Research Articles

Inactivation of harmful cyanobacteria Microcystis aeruginosa by Cu2+ doped corn stalk biochar treated with different pyrolysis temperatures

In this study, biochars (BCs) derived from corn stalk treated at various pyrolysis temperatures (350–950 °C) were prepared and then loaded with Cu2+ to form highly efficient algaecide, i.e. Cu2+-doped BC composites (Cu-BCs). The results showed BCs pyrolyzed at higher temperatures suppressed the growth of Microcystis aeruginosa in the order of BC550 ≫ BC750 > BC950, while BC350 accelerated cell growth due to the release of inorganic nutrients. The difference could be attributed to the physicochemical characteristics, including specific surface area, adsorption capacity of nutrients and the presence of particularly persistent free radicals. Furthermore, Cu-BCs exhibited the improved inactivation performance, but the 72 h growth inhibition rates and reaction activities of Cu-BCs were still influenced by the Cu2+ loading ratio and pyrolysis temperature. These results, reported for the first time, demonstrated the algae inactivation efficiency of pristine BCs, and Cu-BCs were principally manipulated by the biochar pyrolysis temperature.

Climate Warming Does Not Override Eutrophication, but Facilitates Nutrient Release from Sediment and Motivates Eutrophic Process.

The climate is changing. The average temperature in Wuhan, China, is forecast to increase by at least 4.5 °C over the next century. Shallow lakes are important components of the biosphere, but they are sensitive to climate change and nutrient pollution. We hypothesized that nutrient concentration is the key determinant of nutrient fluxes at the water-sediment interface, and that increased temperature increases nutrient movement to the water column because warming stimulates shifts in microbial composition and function. Here, twenty-four mesocosms, mimicking shallow lake ecosystems, were used to study the effects of warming by 4.5 °C above ambient temperature at two levels of nutrients relevant to current degrees of lake eutrophication levels. This study lasted for 7 months (April-October) under conditions of near-natural light. Intact sediments from two different trophic lakes (hypertrophic and mesotrophic) were used, separately. Environmental factors and bacterial community compositions of overlying water and sediment were measured at monthly intervals (including nutrient fluxes, chlorophyll a [chl a], water conductivity, pH, sediment characteristics, and sediment-water et al.). In low nutrient treatment, warming significantly increased chl a in the overlying waters and bottom water conductivity, it also drives a shift in microbial functional composition towards more conducive sediment carbon and nitrogen emissions. In addition, summer warming significantly accelerates the release of inorganic nutrients from the sediment, to which microorganisms make an important contribution. In high nutrient treatment, by contrast, the chl a was significantly decreased by warming, and the nutrient fluxes of sediment were significantly enhanced, warming had considerably smaller effects on benthic nutrient fluxes. Our results suggest that the process of eutrophication could be significantly accelerated in current projections of global warming, especially in shallow unstratified clear-water lakes dominated by macrophytes.

Strategy to improve crude oil biodegradation in oligotrophic aquatic environments: W/O/W fertilized emulsions and hydrocarbonoclastic bacteria.

We studied petroleum biodegradation by biostimulation by using water in oil in water (W/O/W) double emulsions. These emulsions were developed using seawater, canola oil, surfactants, and mineral salts as sources of NPK. The emulsions were used in the simulation of hydrocarbon bioremediation in oligotrophic sea water. Hydrocarbon biodegradation was evaluated by CO2 emissions from microcosms. We also evaluated the release of inorganic nutrients and the stability of the emulsion's droplets. The double emulsions improved CO2 emission from the microcosms, suggesting the increase in the hydrocarbon biodegradation. Mineral nutrients were gradually released from the emulsions supporting the hydrocarbon biodegradation. This was attributed to the formation of different diameters of droplets and therefore, varying stabilities of the droplets. Addition of the selected hydrocarbonoclastic isolates simulating bioaugmentation improved the hydrocarbon biodegradation. We conclude that the nutrient-rich W/O/W emulsion developed in this study is an effective biostimulation agent for bioremediation in oligotrophic aquatic environments.

Warming intensify CO2 flux and nutrient release from algal wrack subsidies on sandy beaches.

Algal wrack subsidies underpin most of the food web structure of exposed sandy beaches and are responsible of important biogeochemical processes that link marine and terrestrial ecosystems. The response in decomposition of algal wrack deposits to global warming has not been studied in ocean-exposed sandy beaches to date. With this aim, passive open top chambers (OTCs) were used to increase soil temperature within the range predicted by the IPCC for western Europe (between 0.5 and 1.5°C), following the hypothesis that the biogeochemical processing of macroalgal wrack subsidies would accelerate in response to temperature increase. The effect of temperature manipulation on three target substrates: fresh and aged macroalgae, and bare sand, was tested. Results indicated that a small warming (<0.5°C) affected the wrack decomposition process through traceable increases in soil respiration through CO2 flux, inorganic nutrients within the interstitial environment (N and P), sediment organic contents measured through the amount of proteins and microbial pool through the total soil DNA. The different responses of soil variables in the studied substrates indicated that the decomposition stage of stranded macroalgae influences the biogeochemical processing of organic matter in sandy beaches. Thus, CO2 fluxes, releases of organic and inorganic nutrients and microbial activity intensify in aged wrack deposits. Our results predict that expected global warming will increase the release of inorganic nutrients to the coastal ocean by 30% for the N (21Gg/year) and 5.9% for P (14 Gg/year); that increase for the flow of C to the atmosphere as CO2 was estimated in 8.2% (523Gg/year). This study confirms the key role of sandy beaches in recycling ocean-derived organic matter, highlighting their sensitivity to a changing scenario of global warming that predicts significant increases in temperature over the next few decades.

Organic matter export to the seafloor in the Baltic Sea: Drivers of change and future projections.

The impact of environmental change and anthropogenic stressors on coastal marine systems will strongly depend on changes in the magnitude and composition of organic matter exported from the water column to the seafloor. Knowledge of vertical export in the Baltic Sea is synthesised to illustrate how organic matter deposition will respond to climate warming, climate-related changes in freshwater runoff, and ocean acidification. Pelagic heterotrophic processes are suggested to become more important in a future warmer climate, with negative feedbacks to organic matter deposition to the seafloor. This is an important step towards improved oxygen conditions in the near-bottom layer that will reduce the release of inorganic nutrients from the sediment and hence counteract further eutrophication. The evaluation of these processes in ecosystem models, validated by field observations, will significantly advance the understanding of the system's response to environmental change and will improve the use of such models in management of coastal areas.

The Effect of Increased Loads of Dissolved Organic Matter on Estuarine Microbial Community Composition and Function.

Increased river loads are projected as one of the major consequences of climate change in the northern hemisphere, leading to elevated inputs of riverine dissolved organic matter (DOM) and inorganic nutrients to coastal ecosystems. The objective of this study was to investigate the effects of elevated DOM on a coastal pelagic food web from the coastal northern Baltic Sea, in a 32-day mesocosm experiment. In particular, the study addresses the response of bacterioplankton to differences in character and composition of supplied DOM. The supplied DOM differed in stoichiometry and quality and had pronounced effects on the recipient bacterioplankton, driving compositional changes in response to DOM type. The shifts in bacterioplankton community composition were especially driven by the proliferation of Bacteroidetes, Gemmatimonadetes, Planctomycetes, and Alpha- and Betaproteobacteria populations. The DOM additions stimulated protease activity and a release of inorganic nutrients, suggesting that DOM was actively processed. However, no difference between DOM types was detected in these functions despite different community compositions. Extensive release of re-mineralized carbon, nitrogen and phosphorus was associated with the bacterial processing, corresponding to 25–85% of the supplied DOM. The DOM additions had a negative effect on phytoplankton with decreased Chl a and biomass, particularly during the first half of the experiment. However, the accumulating nutrients likely stimulated phytoplankton biomass which was observed to increase towards the end of the experiment. This suggests that the nutrient access partially outweighed the negative effect of increased light attenuation by accumulating DOM. Taken together, our experimental data suggest that parts of the future elevated riverine DOM supply to the Baltic Sea will be efficiently mineralized by microbes. This will have consequences for bacterioplankton and phytoplankton community composition and function, and significantly affect nutrient biogeochemistry.

Weathering, secondary mineral genesis, and soil formation caused by lichens and mosses growing on granitic gneiss in a boreal forest environment

Lichens and mosses growing on granitic gneiss in a boreal forest environment caused intense chemical weathering of the rock, producing exclusively biogenic secondary minerals and soils and accumulating solubilised rock-forming elements (Si and metals), but weathering in the absence of these organisms was relatively ineffective. Apart from primary biotite, the only phyllosilicates in the rock were sericite and chlorite formed by hydrothermal metamorphism or abiotic weathering, or both, but the biogenic soils contained expandable clay minerals and, in several cases, kaolinite and calcite, together with illite and chlorite. Lichens were especially effective in altering feldspars to clay, but mosses generally produced a greater abundance of expandable clay minerals, and kaolinite was produced only by certain species of moss — specifically the ones whose rock-derived element concentrations and Mg/Ca ratios were highest. Rock-derived element concentrations were usually highest in mosses, and element enrichment increased with the charge/radius ratio of the cation of the element, suggesting carrier-mediated transport across cell membranes. Furthermore, lichens and mosses produced different assemblages of expandable clay minerals, and most mosses (but none of the lichens) produced authigenic amphiboles and pyroxenes. Biological weathering is attributable to solubilisation of rock-forming elements by chelating agents and H2CO3, bioaccumulation of the elements, and nucleation of secondary silicates by chelate complexes functioning as templates for epitaxial growth of specific crystal structures. The different weathering and soil-forming processes of lichens and mosses suggest a mutualistic strategy for maximising the release of inorganic nutrients from rocks and retaining them in bioavailable forms in the soil.

Nitrogen and phosphorus removal by the Algal Turf Scrubber at an oyster aquaculture facility

Integrated multi-trophic aquaculture is an aquaculture method by which waste of one species is used to produce another product. The purpose of this study was to determine rates of algal productivity using the inorganic nutrient waste from an oyster aquaculture facility, along with assessing the bioremediation potential of integrating an algal production system with the oyster aquaculture facility. Experimental-scale (1m2) Algal Turf Scrubber™ (ATS) systems were deployed at a commercial oyster aquaculture facility in Chesapeake Bay during summer 2012 and 2013 to determine algal productivity rates and assess the potential for remediation of inorganic nutrient release by the facility. Productivity rates of the ATS were high relative to previous studies, with a two-season average of 88.8galgae/m2/d. Total nitrogen and phosphorus removal rates by the ATS averaged 12.2g-N/m2/d and 0.25g-P/m2/d. An ATS with area of 640m2 would be needed to remediate all the nitrogen excreted by the oyster farm. A system of this size would produce 56.9kg of algae (dry weight), and remove 7.8kg of nitrogen and 151.6g of phosphorus per day during the summer growing season. The harvested algae is a resource that could potentially be used as biomass for biofuel production, food for livestock, or fertilizer.

The decomposition of estuarine macrophytes under different temperature regimes

The Great Brak Estuary is a temporarily open/closed system situated along the warm temperate coast of the Western Cape, South Africa. The estuary is subject to a variety of anthropogenic impacts (e.g. freshwater abstraction and sewage discharge) that increases its susceptibility to prolonged periods of mouth closure, eutrophication, and ultimately the formation of macroalgal blooms. The aim of this study was to determine the decomposition characteristics of the most dominant submerged macrophyte and macroalgal species in the Great Brak Estuary. Laboratory experiments were conducted to determine the effect of different temperature regimes on the rate of decomposition of 3 macrophyte species and the extent of inorganic nutrients released. The results demonstrated that anaerobic decomposition of Zostera capensis, Ruppia cirrhosa, and Cladophora glomerata resulted in high levels of inorganic nutrient release over the 28-day study period. Ammonium (NH4+) was the dominant form of dissolved inorganic nitrogen (DIN) released during the decomposition process for all three species. The low levels of total oxidised nitrogen (nitrate and nitrite) released during decomposition were attributed to the inhibition of nitrification by heterotrophic bacteria under anoxic conditions. The relative levels of dissolved inorganic phosphorus (DIP) released were lower than that observed for DIN, and peaked early on in the experimental period (ca. 7 days), thereafter stabilising or decreasing. The DIP levels were explained, in part, by the varying nutrient requirements and limitations of each species (e.g. nitrogen-limited). The release of inorganic nutrients was greatest at higher temperatures (i.e. 25°C and 30°C), due to the reduced bacterial activity experienced at lower temperatures (i.e. 15°C). Ultimately, estuarine health deteriorates during macroalgal blooms, and therefore it is important to implement mitigation measures, such as artificial mouth breaching and plant harvesting, in order to minimise or reverse the effects of eutrophication.Keywords: Great Brak Estuary, decomposition, temperature, inorganic nutrient release, Cladophora glomerata, Zostera capensis, Ruppia cirrhosa

Pesticide Influence on the Desmid Flora of a Reservoir in an Agricultural Region at Campo Verde, Mato Grosso, Brazil

The objective of the research was to investigate the influence of pesticides on the desmid flora. Five series of samples were taken between July 5, 2005, and April 6, 2006, for analysis of pesticide content and algal community structure in the Sao Lourenco River springs on the Pirassununga Ranch, Campo Verde, Mato Grosso. The greatest amounts of pesticides were detected in July, when the abundance of algae was also greatest. Positive correlations were determined between the concentrations of endosulfan (r = 0.94; p = 0.051), cyhalothrin (r = 0.96; p = 0.037) and endrin (r = 0.96; p = 0.037) and the biomass of desmids. Insecticides, such as endosulfan, inhibit the activity of ATPase, contributing considerably to the mortality of the biota, since ATP is of fundamental importance in the energy metabolism of all organisms. This suggests that the pesticides promote algal growth both by removing the small herbivores that feed on the algae and increasing the release of inorganic nutrients from decomposing animals in the water. Algae were least abundance in January, possibly due to the presence of the herbicide atrazine (r = -0.63; p > 0.05).

Jellyfish Modulate Bacterial Dynamic and Community Structure

Jellyfish blooms have increased in coastal areas around the world and the outbreaks have become longer and more frequent over the past few decades. The Mediterranean Sea is among the heavily affected regions and the common bloom - forming taxa are scyphozoans Aurelia aurita s.l., Pelagia noctiluca, and Rhizostoma pulmo. Jellyfish have few natural predators, therefore their carcasses at the termination of a bloom represent an organic-rich substrate that supports rapid bacterial growth, and may have a large impact on the surrounding environment. The focus of this study was to explore whether jellyfish substrate have an impact on bacterial community phylotype selection. We conducted in situ jellyfish - enrichment experiment with three different jellyfish species. Bacterial dynamic together with nutrients were monitored to assess decaying jellyfish-bacteria dynamics. Our results show that jellyfish biomass is characterized by protein rich organic matter, which is highly bioavailable to ‘jellyfish - associated’ and ‘free - living’ bacteria, and triggers rapid shifts in bacterial population dynamics and composition. Based on 16S rRNA clone libraries and denaturing gradient gel electrophoresis (DGGE) analysis, we observed a rapid shift in community composition from unculturable Alphaproteobacteria to culturable species of Gammaproteobacteria and Flavobacteria. The results of sequence analyses of bacterial isolates and of total bacterial community determined by culture independent genetic analysis showed the dominance of the Pseudoalteromonadaceae and the Vibrionaceae families. Elevated levels of dissolved proteins, dissolved organic and inorganic nutrient release, bacterial abundance and carbon production as well as ammonium concentrations characterized the degradation process. The biochemical composition of jellyfish species may influence changes in the amount of accumulated dissolved organic and inorganic nutrients. Our results can contribute insights into possible changes in bacterial population dynamics and nutrient pathways following jellyfish blooms which have important implications for ecology of coastal waters.

Short-term response of nutrients, carbon and planktonic microbial communities to floodplain wetland inundation

Environmental flows were released to the Macquarie Marshes (~210,000 ha) in north-west NSW of Australia between October and December 2005, inundating an estimated 24,600 ha of floodplain area. According to the flood pulse concept, the marsh floodplains would have stored large amounts of nutrients and carbon during dry antecedent conditions, which would be released into the overlaying flood water. Field studies were conducted in mid-December 2005 at two sites, one on open floodplain woodland with a sparse canopy of River Red Gum and ground cover dominated by saltbushes and the other on open floodplain with black roly-poly. At each site, nutrients, dissolved organic carbon (DOC), planktonic bacteria and phytoplankton were monitored daily for a 6-day period from the overlaying water of a floodplain inundated by the environmental water release. Those in mesocosms deployed in situ, containing marsh floodplain sediments that had been inundated artificially, were also monitored. The mesocosm results from both the sites showed that release of nitrogen was rapid, attaining mean concentrations of total nitrogen of 3.7–14.8 mg l−1, followed by more gradual increases in total phosphorus (mean concentrations 0.6–0.8 mg l−1) and DOC (26.1–50.2 mg l−1) within the 6-day experiment; planktonic microbial communities developed concomitantly with the increasing concentrations of nutrients and DOC, attaining mean densities of (6.0–6.9) × 106 cells ml−1 of planktonic bacteria and (80.7–81.4) × 103 cells ml−1 of phytoplankton; and for each site the overall measured condition of the mesocosm tended to approach that of the Marshes, over the course of the 6-day experiment. The present study (both observational and experimental) demonstrates that the floodplain sediments in the Marshes, which have been exposed to dry antecedent conditions, release nutrients and carbon to the overlaying flood water following inundation. These resources are thought to have been stored during the dry antecedent phase in accord with the flood pulse concept. Based on the mesocosm experiment, the released nutrients and carbon are in turn most likely to be used by microbial components, such as bacteria and algae, which develop within days of inundation of the floodplain sediments. Thus, environmental flow release provides potential for floodplains to attain a series of ecological responses including initial release of inorganic nutrients and dissolved organic matter and increase in planktonic bacteria and phytoplankton.

Fishes and shrimps are significant sources of dissolved inorganic nutrients in intertidal salt marsh creeks

The release of inorganic nutrients by nekton (fish and shrimp) assemblages through excretion and bioturbation was quantified for intertidal creeks in a warm-temperate estuary, North Inlet, South Carolina, USA. Excretion rates for individual nekton taxa were determined for captive animals maintained in the field. Nutrient production by nekton assemblages was determined in laboratory tank experiments in which the effects of nutrient releases through excretion and bioturbation could be separated. These values and field-measured biomass data were used to calculate and compare nutrient generation rates by nekton to those of other biotic and abiotic sources in intertidal creeks. Mass specific ammonium excretion rates ranged from 5.7–11.9 μmol g dw −1 h −1 in early spring to 8.3–20.7 μmol g dw −1 h −1 in the summer. Orthophosphate excretion rates were distinctly lower and never exceeded 3 μmol g dw −1 h −1. The N/P ratio in the excretory products of the different taxa was generally higher during summer than in early spring. In the summer, experiments on nekton assemblages in tanks indicated that mass specific ammonium production rates based on excretion plus bioturbation were on average 40% higher than rates based on excretion alone. Orthophosphate production was unaffected by bioturbation during both seasons. Nekton, oyster reefs, and benthic remineralization were identified as the major sources for inorganic nutrients. These observations and the fact that consumer driven nutrient cycling through nekton has not been recognized as an important process in coastal ecosystems suggest that additional efforts to quantify the role of large motile animals are needed.

Feasible suppression technique of methane emission from paddy soil by iron amendment

A revolving furnace slag (RFS), which is a by-product of the steel industry, and a spent disposable portable body warmer (PBW), which harnessed the heat of iron oxidation reaction, were used as iron materials. Portions of 4 kg of Coarse and Medium Textured Gley soil were placed into plastic pots (3 L). RFS was added to the pots at the rate of 0 (control), 10, 20, 40, 100 ton ha−1, while PBW was added at 10 ton ha−1 only. Methane flux from the potted soil with rice plants and Eh were measured during cropping seasons in 1999 and 2000. In the 1999 experiment, the RFS treatments showed lower Eh values compared with the control, especially at the early period of cultivation, although the RFS was applied to maintain the soil oxidative. The rapid decrease in Eh under high application of RFS may be due to the high pH of the RFS (pH (RFS:H2O = 1:2.5) was 12.2). However, total methane emission during the cultivation period significantly decreased, about 10%, when 10–40 ton ha−1 of RFS and 10 ton ha−1 of PBW were applied. The grain yield was significantly increased, about 30%, when 40 or 100 ton ha−1 of RFS was applied. This was also partly due to the release of inorganic nutrients from RFS and also from soil. The latter, due to effect of the alkaline RFS on soil. In the 2000 experiment, the pots with soils from 1999 were used without further application of iron materials. The influence of high application of RFS on soil Eh disappeared, compared with 1999. Total methane emission significantly decreased, about 35%, at 20 ton ha−1 of RFS. However, the increase of grain yield caused by RFS in 1999 was diminished, compared with 1999. Production activity of both methane and carbon dioxide at the RFS treatments were decreased, while methane oxidizing activity was increased. The decrease in total methane emission may be attributed to not only inhibition of methane production but also enhanced methane oxidation. In conclusion, methane emission from paddy soil could be suppressed, over two cropping seasons by single application of RFS without loosing grain yield.

Differential anaerobic decomposition of seagrass (Zostera noltii) and macroalgal (Monostroma obscurum) biomass from Arcachon Bay (France)

Arcachon Bay is characterized by extensive meadows of the seagrass Zostera noltii. Moreover, as a consequence of eutrophication, massive proliferations of the macroalga (Monostroma obscurum) have occurred since the beginning of 1990s. This paper describes the anaerobic decomposition of biomass of both species under experimental conditions by two methods. Firstly, the dynamics of decomposition were studied in situ using litter bags. The remaining biomass and the elemental composition of the decomposing macrophytes were monitored. Secondly, degradation was studied in experimental containers under anoxic conditions in which the release of inorganic nutrients and the development of fermentative and sulfate-reducing bacterial populations were followed. The decomposition rate of total biomass was faster for macroalgae than for the vascular plants, thus corroborating previous observations. However, both in situ and laboratory experiments showed that the anaerobic decomposition of the seagrass Z. noltii resulted in rapid release of inorganic N and P, and increasing C/N and C/P ratios of the residual biomass. As a result, the recycling of inorganic nitrogen and phosphorus compounds was slightly more efficient for Z. noltii than for M. obscurum. Recycling of inorganic nutrients appears to be of a great importance to the whole ecosystem, because of the extensive spreading of Z. noltii in the bay.

Macroinvertebrates and litter nutrient release on a sub-Antarctic Island

For most plant communities on Marion Island (47°S, 38°E), mineralization of the large reserves of organic matter is the main process supplying nutrients for plant growth. However, due to the constantly low temperature, soil acidity and waterlogging, rates of nutrient release mediated by microorganisms alone are too low to account for the amounts taken up by the vegetation. Microcosm studies showed that the rate of inorganic nutrient release from plant litter is generally enhanced by moth larvae, earthworms, weevil larvae and adults, snails and slugs. Overall, moth larvae and slugs exerted the greatest influence across all nutrients tested (nitrogen, phosphorus, calcium, potassium, magnesium and sodium), although the effect was most consistently significant for nitrogen and phosphorus. The influence of the other invertebrate species was mostly limited to particular animal/nutrient combinations, which were fairly consistent across litter types, e.g. earthworms for nitrogen and phosphorus, snails for calcium and weevil adults for potassium. These findings suggest that, by ‘short-circuiting’ the slow microbially mediated mineralization of nutrients from organic matter, soil invertebrates are important agents of nutrient cycling on the island. Die meeste plantgemeenskappe op Marioneiland (47°S, 38°O) is vir hulle voedingstowwe van mineralisasie van die groot organiese reserwes afhanklik. Weens die voortdurend lae temperature, die suurheid en die waterdeurdrenktheid van die grond, kan die vrystelling van voedingstowwe a.g.v. mikroörganisme-aktiwiteite nie die hoeveelhede verklaar wat deur die plante opgeneem word nie. In isolasiehouers (mikrokosmosse) is aangetoon dat motlarwes, erdwurms, kalanderlarwes en -volwassenes, slakke en naakslakke, die vrystelling van anorganiese minerale uit plantreste versnel. Motlarwes en slakke het oor die algemeen die grootste bydrae tot die vrystelling van alle voedingstowwe (stikstof, forfor, kalsium, kalium, magnesium en natrium) gelewer, alhoewel die effek deurentyd vir stikstof en fosfor die beduidendste was. Die invloed van die ander invertebrate was hoofsaaklik tot spesifieke dier/voedingstofkombinasies beperk wat redelik konstant was vir al die plantreste — erdwurms het veral stikstof en fosfor vrygestel, terwyl slakke veral kalsium en volwasse kalanders veral kalium vrygestel het. Die bevindinge het aangedui dat invertebrate belangrike agente in voedingstofsiklusse op die eiland is deurdat hulle die stadige mikrobiologiese mineralisasie ‘kortsluit’.

The ecology and cultivation of mussels: new advances

Extensive cultivation of mussels is a world-wide activity of growing economic importance. To meet the increased demand and to spread the risk of damage from climatic events and environmental pollution, extension of mussel cultivation to new, unpolluted areas is to be expected. This is, however, limited because these areas are often in use for fisheries or nature conservation. Possible extension to new areas now depends on knowledge of the impacts of mussel populations on the ecosystem. For a number of mussel populations from natural bottom communities, culture plots and suspended culture, average annual budgets of uptake and release of carbon and nitrogen are reported in the literature. Recent in situ measurements on mussel beds show high rates of uptake of particulate material and release of inorganic nutrients, resulting in the regeneration of potentially limiting nutrients, and an increase of the production and turnover of phytoplankton. No such high nutrient release rates have been reported so far from accumulated biodeposits under mussel rafts or long-line culture systems. So, the impacts of suspended culture may differ from those of bottom culture. To understand the interaction of mussel populations with other components of the ecosystem, dynamic simulation models are used. Simulations with a model of the Oosterschelde ecosystem show effects of change in biomass of mussels on the scope for growth of mussels and other benthic suspension feeders, and consequently on the carrying capacity of the system for mussel cultivation. However, the benthic suspension feeders seem to have a stabilizing influence on the energy flow of the first and second trophic levels. It is concluded that further advances in mussel cultivation require knowledge of the role of mussels in the ecosystem, which can be provided by integrated ecological research and modelling.

Effect of mangrove detrital outwelling on nutrient regeneration and oxygen fluxes in coastal sediments of the central Great Barrier Reef lagoon

The effect of tidal outwelling of mangrove detritus on sediment nutrient chemistry, nutrient regeneration and oxygen fluxes in a coastal area of the central Great Barrier Reef lagoon was examined. Organic carbon and total nitrogen concentrations ranged from 0·2 to 3·9% and 0·01 to 0·18% by sediment dry weight (DW), respectively, and were highest at stations receiving the greatest quantities of mangrove litter. Total phosphorus concentrations ranged from 0·013 to 0·048% by DW, but did not relate to outwelling. C:N:P. ratios ranged from 29:6:1 at the site receiving the least amount of detritus to a high of 397:17:1 at the station receiving the most litter. The effect of outwelling on dissolved inorganic nutrients in porewaters was less clear, with concentrations closely related to sediment type and obscured by contributions from continental runoff. Ammonium (range: 10–310 μM) and silicate (range: 10–315 μM) were in greatest concentration at most sites followed by phosphate (range: 1–12 μM) and nitrite and nitrate (0·07–6·0 μM). Directly measured fluxes of dissolved inorganic nutrients across the sediment-water interface were either undetectable or small [ΣN = −560 to +3503; PO43 = undetectable to +157; Si(OH)4 = undetectable to +6449 μmol m−2 day−1] and not related to outwelling. Addition of mangrove litter to ☐core samples incubated for 10 days in the laboratory did not affect rates of dissolved inorganic nutrient release. Oxygen consumption rates ranged from 8·7 to 60·2 mmol O2 m−2 day−1 and were highest at most sites closest to mangrove forests, in agreement with previous measurements of bacterial productivity. Rates of net community primary production were either undetectable or low (as were chlorophyll α and phaeopigments) ranging from 12 to 77 mg C m−2 day−1. It appears that much of the deposited mangrove litter is highly refractory, but the amount of sedimented material appears to be great enough to significantly enrich bulk concentrations of particulate carbon and nitrogen, and rates of oxygen consumption. Benthic nutrient regeneration contributes only a small proportion to the daily nitrogen (6%) and phosphorus (9%) demand of coastal phytoplankton, implying supplementation from continental runoff and/or high rates of pelagic recycling.

Microphytobenthic productivity and biomass in sublittoral sediments of a stratified bay, southeastern Kattegat

The sublittoral sediment-associated microflora (microphytobenthos) of Laholm Bay, southeastern Kattegat, was investigated for a period of 3 yr by taking monthly sediment samples at depths of 2–20 m. The aims were to quantify the importance of the microphytobenthos in the primary production of a coastal area subjected to eutrophication and to assess the most important limiting factors. There was a considerable potential microphytobenthic production in Laholm Bay, but the actual in situ production was limited by light at a depth of > 5 m. Productivity and biomass did not, however, decrease linearly with depth and some of the highest values were measured at ≈ 15 m, where only a few percent of the surface light penetrated. This pattern of distribution along the depth gradient is interpreted as a result of the interaction of light and nutrient conditions, sediment type, and the degree of exposure to water movements. The range of photon-flux densities needed to saturate photosynthesis I ( I k ) was large (30–320 μE · m −2 · s −1) and varied with season and depth. The microbenthic primary production occurred mainly during the period May–September and varied between < 1 and 20 g C · m −2 · yr −1 depending on depth and sediment type. Viable sedimented phytoplankton cells occasionally contributed to benthic primary production. The annual microphytobenthic production for the whole bay has been estimated as 5–10 g C · m −2, which corresponds to 5–10% of the annual phytoplankton production. Based on this study and previous laboratory experiments, it is suggested that in an early stage of eutrophication, before an extensive increase in turbidity caused by phytoplankton, the microphytobenthos will benefit from increased nutrient levels. Microphytobenthic production will then have a positive effect on the ecosystem by improving oxygen conditions at the sediment-water interface and by decreasing the release of inorganic nutrients, in particular ammonium and phosphate, from the sediment.

Oxygen Consumption and Dissolved Inorganic Nutrient Production in Marine Coastal and Shelf Sediments of the Middle Atlantic Bight

AbstractThe benthic oxygen demand and inorganic nutrient release have been investigated in the coastal zone of the Mid‐Atlantic Bight of the United States using in situ and ship‐board incubations to estimate fluxes across the sediment‐water interface. Oxygen demand ranged from ca. 70 ml m−2 hr−1 nearshore in warm (25°C) muddy sediments to ca. 4 ml m−2 hr−1 in cold (6°C), coarse‐grained sediments offshore. Ammonium ion flux was out of the sediments in all but 4 of 29 incubations, while nitrate was often found to be utilized within or on the sediments, decreasing in 10 of 29 incubations. Those locations with fluxes of nitrate out of the sediment had concentrations in the pore water that were generally high, sometimes up to several mM l−1. Nitrate fluxes were always well below those of ammonia, even where high almost equivalent concentrations of both NH4 and NO3 were found at the same locale.On George's Bank only 13 % of total N demand by the phytoplankton was estimated to be supplied by the benthos, whereas in New York Bight the supply amounted to 42 % of the demand. This difference can be attributed to higher pelagic biological and advective (mixing and upwelling) inputs to George's Bank compared to the relatively well stratified New York Bight in late summer and autumn.