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Nutrient Inputs (nutrient + input)

Distribution by Scientific Domains

Life Sciences	71%
Earth and Environmental Science	28%

Selected Abstracts

Nitrogen, phosphorus and potassium utilization and their cycling in a beef-forage production system

ANIMAL SCIENCE JOURNAL, Issue 4 2009
Yusuke TABATA
ABSTRACT The objective of this study was to quantify nitrogen (N), phosphorus (P) and potassium (K) utilization and their cycling in a beef-forage production system. A survey was conducted at the Kyoto University experimental farm in Kyoto Prefecture, Japan, and included 9.5 ha of meadow and about 160 head of beef cattle. Forages cultivated on the meadow were ensiled and offered to breeding cows. The whole farm was regarded as a beef-forage production system. The system consisted of three components: animals, manure and soil/crop. Nutrient inputs, flows through the soil-plant-animal pathway and outputs were quantified for 2 periods for the whole farm. Nutrient utilization was evaluated by nutrient balances, utilization efficiencies (ratio of nutrient export to nutrient input) and cycling index. The average nutrient balances of N, P and K for the whole farm (kg/year/ha) were 435.7, 136.3, and 262.8, and the average nutrient utilization efficiencies were 0.08, 0.06, and 0.01, respectively. The characteristics of nutrient balances and utilization efficiencies for each component differed among the nutrients. The average cycling indices for N, P and K were 0.19, 0.17 and 0.49, respectively. This study illustrates the importance of internal nutrient cycling for improving nutrient utilization in beef production systems. [source]

Nutrient cycling efficiency explains the long-term effect of ecosystem engineers on primary production

FUNCTIONAL ECOLOGY, Issue 1 2007
SÉBASTIEN BAROT
Summary 1Soil organisms, such as earthworms, accelerate mineralization of soil organic matter and are thought to be beneficial for plant growth. This has been shown in short-term microcosm experiments. It is thus legitimate to ask whether these increases in plant growth are due to brief pulses of mineralization or whether these increases are long-lasting. 2This question was addressed using a system of differential equations modelling the effects of decomposers on nutrient cycling via trophic (nutrient assimilation) and nontrophic effects (through their ecosystem engineering activities). 3The analytical study of this model showed that these processes increase primary production in the long term when they recycle nutrients efficiently, allowing a small fraction of the recycled nutrients to be leached out of the ecosystem. 4Mineralization by the ecosystem engineering activities of decomposers seems to deprive them of a resource. However, it was shown that a decomposer may increase its own biomass, through its ecosystem engineering activities, provided the created recycling loop is efficient enough. 5Mechanisms through which earthworms may modify the efficiency of nutrient cycling are discussed. The necessity of measuring the effect of earthworms on the nutrient input,output balance of ecosystems under field conditions is emphasized. [source]

The Trophic Index of Macrophytes (TIM) , a New Tool for Indicating the Trophic State of Running Waters

INTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 1 2003
Susanne Schneider
Abstract In running waters, apart from structural degradation, nutrient input becomes increasingly important. To investigate the indicator values of as many species of submerged macrophytes as possible numerous samples of the sediment within macrophyte stands and the overlying water were taken in running waters throughout Bavaria, Germany. To develop the Trophic Index of Macrophytes (TIM), the concentrations of soluble reactive phosphorus of both the water body and the sediment pore water were used. Based on a weighted sum of the SRP-concentrations of the water body and the sediment pore water, indicator values were determined for a total of 49 species of submerged macrophytes. A detailed method is described on how and depending on which preconditions the trophic state of running waters can be determined by the TIM. An example of the TIM in the stream Rotbach is given. It shows that the TIM is a useful means to detect differences in the phosphorus loading of running waters. [source]

Nutrients, Chlorophyll a and Phytoplankton in the ,skenderun Bay (Northeastern Mediterranean)

MARINE ECOLOGY, Issue 2 2002
Sevim Polat
Abstract. The monthly changes in chlorophyll a, phytoplankton abundance and nutrient concentrations at two stations, one at the inshore and the other at the deep waters of the northern part of ,skenderun Bay, were investigated between 1994,,,1995. The vertical distribution of nutrients and phytoplankton biomass were also studied at the deep station. The concentrations of NO3+NO2 -N, PO4 -P and SiO4 -Si of surface water at both stations were 0.31,,,1.63 µg-at · l -1, 0.08,,,0.60 µg-at · l -1 and 0.50,,,2.7 µg-at · l -1, respectively. The highest concentrations were measured at the inshore station and clear differences were found between the inshore and deep-water stations. Chlorophyll a concentrations ranged from 0.17 to 2.78 µg · l -1 and the highest value was measured in March. At the inshore station, which was affected by land run-off, phytoplankton abundance reached the highest value (21,308 cells · l -1) in October 1995, with a marked dominance of Pseudonitzschia pungens (20,200 cells · l -1). The nutrient and chlorophyll a concentrations at the inshore station were higher than those at the deep station. One reason for this is the land-based nutrient input into the coastal area here. In spite of these effects, the bay is not eutrophicated because of circulation events in the northeastern Mediterranean. [source]

Dynamics of grazing lawn formation: an experimental test of the role of scale-dependent processes

OIKOS, Issue 10 2008
Joris P. G. M. Cromsigt
Grazing lawns are characteristic for African savanna grasslands, standing out as intensely grazed patches of stoloniferous grazing-tolerant grass species. Grazing lawn development has been associated with grazing and increased nutrient input by large migratory herds. However, we argue that in systems without mass migrations disturbances, other than direct grazing, drive lawn development. Such disturbances, e.g. termite activity or megaherbivore middens, also increase nutrient input and keep the bunch vegetation down for a prolonged time period. However, field observations show that not all such disturbances lead to grazing lawns. We hypothesize that the initial disturbance has to be of a minimal threshold spatial scale, for grazing intensity to be high enough to induce lawn formation. We experimentally tested this idea in natural tall savanna grassland. We mowed different-sized plots to simulate initial disturbances of different scales (six times during one year) and applied fertilizer to half of the plots during two years to simulate increased nutrient input by herbivores or termite activity. Allowing grazing by naturally occurring herbivores, we followed the vegetation development over more than three years. Grazing kept bunch grass short in coarser, fertilized plots, while grasses grew out toward their initial height in fine-scale and unfertilized plots. Moreover, lawn grasses strongly increased in cover in plots with an increased nutrient input but only after coarser scale disturbance. These results support our hypothesis that an increased nutrient input in combination with grazing indeed induces grazing lawn formation, but only above a threshold scale of the initial disturbance. Our results provide an alternative mechanism for the development of grazing lawns in systems that lack mass migrating herds. Moreover, it gives a new spatial dimension to the processes behind grazing lawn development, and hence help to understand how herbivores might create and maintain spatial heterogeneity in grassland systems. [source]

Nitrogen, phosphorus and potassium utilization and their cycling in a beef-forage production system

Effects of common carp Cyprinus carpio (L.) and feed addition in rohu Labeo rohita (Hamilton) ponds on nutrient partitioning among fish, plankton and benthos

AQUACULTURE RESEARCH, Issue 1 2008
Mohammad Mustafizur Rahman
Abstract The effects of introducing common carp (CC) and of adding artificial feed to fertilized rohu ponds on water quality and nutrient accumulation efficiency were studied. All ponds were stocked with 15 000 rohu ha,1. Treatments included ponds with rohu alone, rohu plus 5000 common carp ha,1 and rohu plus 10 000 CC ha,1. A comparison was also made between supplementally fed and non-fed ponds. The overall highest nitrogen (N) and phosphorus (P) concentrations were observed in ponds with 5000 CC ha,1, followed by ponds with 10 000 and 0 CC ha,1. The largest fractions of N and P inputs accumulating in fish, phytoplankton and zooplankton were observed in ponds with 5000 CC ha,1, followed by ponds with 10 000 CC ha,1 and subsequently ponds without CC. Relatively more nutrients accumulated in benthic organisms in ponds without than in ponds with CC. A smaller fraction of the nutrient input was retained in fish, plankton and benthic organisms in ponds without CC compared with ponds with CC. Compared with 5000 CC ha,1, stocking 10 000 CC ha,1 can be considered as overstocking, because this leads to lower fish production and relatively less nutrients retained in plankton and benthic organisms. [source]

The role of vegetation patterns in structuring runoff and sediment fluxes in drylands

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 2 2005
Juan Puigdefábregas
Abstract The dynamics of vegetation-driven spatial heterogeneity (VDSH) and its function in structuring runoff and sediment fluxes have received increased attention from both geomorphological and ecological perspectives, particularly in arid regions with sparse vegetation cover. This paper reviews the recent findings in this area obtained from field evidence and numerical simulation experiments, and outlines their implications for soil erosion assessment. VDSH is often observed at two scales, individual plant clumps and stands of clumps. At the patch scale, the local outcomes of vegetated patches on soil erodibility and hydraulic soil properties are well established. They involve greater water storage capacity as well as increased organic carbon and nutrient inputs. These effects operate together with an enhanced capacity for the interception of water and windborne resources, and an increased biological activity that accelerates breakdown of plant litter and nutrient turnover rates. This suite of relationships, which often involve positive feedback mechanisms, creates vegetated patches that are increasingly different from nearby bare ground areas. By this way a mosaic builds up with bare ground and vegetated patches coupled together, respectively, as sources and sinks of water, sediments and nutrients. At the stand scale within-storm temporal variability of rainfall intensity controls reinfiltration of overland flow and its decay with slope length. At moderate rainfall intensity, this factor interacts with the spatial structure of VDSH and the mechanism of overland flow generation. Reinfiltration is greater in small-grained VDSH and topsoil saturation excess overland flow. Available information shows that VDSH structures of sources and sinks of water and sediments evolve dynamically with hillslope fluxes and tune their spatial configurations to them. Rainfall simulation experiments in large plots show that coarsening VDSH leads to significantly greater erosion rates even under heavy rainfall intensity because of the flow concentration and its velocity increase. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Nutrients, diversity, and community structure of two phytotelm systems in a lower montane forest, Puerto Rico

ECOLOGICAL ENTOMOLOGY, Issue 3 2000
Barbara A. Richardson
Summary 1. Bromeliad and heliconia phytotelmata in the same forest area were compared in terms of their animal assemblages, nutrient inputs, and plant architecture. 2. For all major elements, nutrient inputs from canopy-derived debris and rainfall in bromeliads were significantly lower than those derived from decaying flower parts and plant secretions in heliconia bracts. Bromeliads contained significantly fewer organisms per unit volume of water and unit dry weight of organic matter than did heliconia inflorescences. They also contained a significantly lower animal biomass (199 mg DW from 15 bromeliads, 527 mg DW from 15 heliconia inflorescences). 3. Species richness was independent of abundance, demonstrating that, at least for small container habitats, higher abundance does not necessarily lead to a greater species richness. Communities were remarkably similar in patterns of relative abundance and species richness (23 spp. in bromeliads, 21 spp. in heliconia), probably due to functional similarities in plant architecture, with the two most abundant species comprising 60,62% of the total community. Coefficients of similarity were low because of marked differences in species assemblages. 4. Some taxa were phytotelm generalists but most showed a preference for one particular habitat, indicating differential selection in the choice of oviposition sites and larval development within the forest ecosystem. In common with many island communities, species richness was lower than that reported for these phytotelm habitats in mainland central and south America. [source]

Factors influencing bacterial dynamics along a transect from supraglacial runoff to proglacial lakes of a high Arctic glacieri

FEMS MICROBIOLOGY ECOLOGY, Issue 2 2007
Birgit Mindl
Abstract Bacterial production in glacial runoff and aquatic habitats along a c. 500 m transect from the ablation area of a Svalbard glacier (Midre Lovénbreen, 79°N, 12°E) down to a series of proglacial lakes in its forefield were assessed. In addition, a series of in situ experiments were conducted to test how different nutrient sources (glacial flour and dissolved organic matter derived from goose faeces) and temperature affect bacterial abundance and production in these ecosystems. Bacterial abundance and production increased significantly along this transect and reached a maximum in the proglacial lakes. Bacterial diversity profiles as assessed by denaturing gradient gel electrophoresis indicated that communities in glacial runoff were different from those in proglacial lakes. Heterotrophic bacterial production was mainly controlled by temperature and phosphorus limitation. Addition of both glacial flour and dissolved organic matter derived from goose faeces stimulated bacterial production in those lakes. The results suggest that glacial runoff sustains an active bacterial community which is further stimulated in proglacial lakes by higher temperatures and nutrient inputs from bird faeces. Thus, as in maritime temperate and Antarctic settings, bacterial communities developing in the recently deglaciated terrain of Svalbard receive important inputs of nutrients via faunal transfers from adjacent ecosystems. [source]

Assessment of methane and nitrous oxide flux from mangroves along Eastern coast of India

GEOFLUIDS (ELECTRONIC), Issue 4 2008
R. CHAUHAN
Abstract Mangroves are considered to be a minor source of greenhouse gases (CH4 and N2O) in pristine environmental condition. However, estimates of efflux suggest that anthropogenic activities have led to a pronounced increase in greenhouse gas emission. Along the east coast of India, mangroves vary substantially in area, physiography and freshwater input, which ultimately modify the biogeochemical processes operating within this ecosystem. An attempt has here been made to elucidate the existing variation and role of climatic variability on the emission of greenhouse gases from mangroves. The flux estimates of CH4 and N2O have been quantified from Bhitarkanika mangrove accounting for spatial and temporal (seasonal) variation. The annual rates were estimated to be 0.096 × 10 9 g CH4 year,1 and 5.8 × 103g N2O year,1 for the whole mangrove area of the east coast of India. Upscaling these estimates yield an annual emission of 1.95 × 10 12 g CH4 year,1 and 1.1 × 10 11 g N2O year,1 from worldwide mangrove areas. The influence of elevated nutrient inputs through anthropogenic influence enhances the emission of greenhouse gas. The present article shows the need to develop an inventory on greenhouse gas flux from mangrove ecosystem. [source]

Extensification of grassland use in the Welsh uplands: sheep performance in years 1,6

GRASS & FORAGE SCIENCE, Issue 2 2001
M. Fothergill
An experiment was established in 1991 on a 25-year-old perennial ryegrass/bent (Lolium perenne L./Agrostiscapillaris L.)-dominated pasture in Wales to study the effects of reducing nutrient inputs to previously fertilized upland pasture. The effects of the removal of applications of (1) N (denoted by CaPK) (2) N, P and K (Ca) and (3) N, P, K, and Ca (Nil) were compared with a treatment which received applications of all four nutrients (CaPKN) over a 6-year period (1991,96) in a randomized block design replicated three times. The experiment was managed under a continuous variable stocking regime (ewes and lambs until weaning and ewes thereafter) maintaining a sward surface height of 4·0 cm throughout the grazing season. Although individual liveweight gain of the lambs was unaffected by the treatments, there was a significant reduction (P < 0·05) in total lamb liveweight gain, ewe stocking rate and length of grazing season as a result of the withdrawal of nutrients. Over the 6 years total lamb liveweight gain was reduced by 17%, 32% and 45% and ewe stocking rate by 21%, 36% and 49% on treatments CaPK, Ca and Nil, respectively, compared with treatment CaPKN. The effect of withdrawing nutrient inputs on ewe stocking rate was progressive and by 1996 the Nil input treatment displayed a 63% reduction compared with the CaPKN treatment and this was also coupled with a 21-day reduction in length of the grazing season. During the post-weaning period, ewes from the Nil input treatment recorded a liveweight loss in 1995 and only a modest liveweight gain in 1996. This coupled with significantly lower body condition scores (P < 0·01) of these ewes in the autumn indicated that the Nil input treatment could lead to reductions in reproductive performance. [source]

Can management compensate for atmospheric nutrient deposition in heathland ecosystems?

JOURNAL OF APPLIED ECOLOGY, Issue 4 2006
WERNER HÄRDTLE
Summary 1Atmospheric nutrient deposition has contributed to widespread changes in heathlands throughout Europe. As a consequence, management is now being considered as a potential tool with which to compensate for increased nutrient loads. Currently, only limited information is available on the extent to which management measures could compensate for atmospheric nutrient deposition. We hypothesized that low-intensity management measures are not sufficient to counterbalance current nutrient inputs, particularly of nitrogen (N). 2In order to improve heathland management schemes, we evaluated the effectiveness of different management measures in reducing the impact of ongoing atmospheric nutrient loads. We compared the effects of mowing, prescribed burning (low-intensity management) and sod-cutting (high-intensity management) on heathland nutrient budgets [N, calcium (Ca), potassium (K), magnesium (Mg) and phosphorus (P)] in the Lueneburg Heath nature reserve (north-west Germany). Nutrient balances were calculated by analysing the present-day input, the output as a result of the removal of biomass/humus horizons, and changes in leaching rates. 3Nutrient losses by increased leaching following management measures were negligible compared with nutrient losses caused by the removal of above-ground biomass or humus horizons. The total quantities of nutrients removed by sod-cutting were equivalent to between 37 and 176 years of atmospheric input (for N, 89 years). 4In contrast, the quantities of N removed by mowing and prescribed burning were equivalent to only 5 years of atmospheric input. Thus, heathlands subjected to such treatments will accumulate N in the long term. In addition, output,input ratios for phosphorus (P) exceeded those for N in the mowing and sod-cutting experiments. It is therefore likely that heathlands currently (co-) limited by N will shift to being more P-limited in the long term. This will promote species that are well adapted to P-limited sites (e.g. Molinia caerulea). 5Synthesis and applications. This study shows that low-intensity management cannot compensate for atmospheric N loads in the long term. Consequently, high-intensity management measures are an indispensable tool in preserving a long-term balanced N budget in heathlands. In order to maintain a diverse structure, managers need to combine low- and high-intensity management measures. Prescribed burning proved to be the best means of avoiding an increasing P shortage, because this measure causes very low P outputs. [source]

Wood-feeding beetles and soil nutrient cycling in burned forests: implications of post-fire salvage logging

AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 1 2010
Tyler P. Cobb
1Rising economic demands for boreal forest resources along with current and predicted increases in wildfire activity have increased salvage logging of burned forests. Currently, the ecological consequences of post-fire salvage logging are insufficiently understood to develop effective management guidelines or to adequately inform policy decision-makers. 2We used both field and laboratory studies to examine the effects of post-fire salvage logging on populations of the white-spotted sawyer Monochamus scutellatus scutellatus (Say) (Coleoptera: Cerambycidae) and its ecological function in boreal forest. 3Monochamus s. scutellatus adults were relatively abundant in both burned and clear-cut logged sites but were absent from salvage logged sites. 4An in situ mesocosm experiment showed that the abundance of M. s. scutellatus larvae in burned white spruce bolts was linked to changes in total organic nitrogen and carbon in mineral soil. 5Organic nutrient inputs in the form of M. s. scutellatus frass increased mineral soil microbial respiration rates by more than three-fold and altered the availability of nitrogen. Changes in nitrogen availability corresponded with decreased germination and growth of Epilobium angustifolium and Populus spp. but not Calamagrostis canadensis. 6Although the present study focused on local scale effects, the reported findings suggest that continued economic emphasis on post-fire salvage logging may have implications beyond the local scale for biodiversity conservation, nutrient cycling and plant community composition in forest ecosystems recovering from wildfire. [source]

160 Copepodology for the Phycologist with Apologies to G. E. Hutchenson

JOURNAL OF PHYCOLOGY, Issue 2003
P. A. Tester
Heterocapsa triquetra is one of the most common bloom forming dinoflagellates found in estuaries and near shore regions around the world. In order to bloom, H. triquetra optimizes a suite of factors including low grazing pressure, increased nutrient inputs, alternative nutrient sources, and favorable salinity and hydrodynamic conditions, as well as the negative factors of temperature-limited growth, short day lengths, and periods of transient light limitation. The prevailing environmental conditions associated its wintertime blooms are largely the result of atmospheric forcing. Low-pressure systems moved through coastal area at frequent intervals and are accompanied by low air temperatures and rainfall. Runoff following the rainfall events supplies nutrients critical for bloom initiation and development. Heterocapsa triquetra blooms can reach chl a levels >100 mg L,1 and cell densities between 1 to 6×106 L,1. As the blooms develop, nutrient inputs from the river became insufficient to meet growth demand and H. triquetra feeds mixotrophically, reducing competition from co-occurring phytoplankton. Cloud cover associated with the low-pressure systems light limit H. triquetra growth as do low temperatures. More importantly though, low temperatures limit micro and macrozooplankton populations to such an extent that grazing losses are minimal. [source]

DO PHYSICAL FACTORS REGULATE PHYTOPLANKTON DISTRIBUTION PATTERNS IN LARGE, SHALLOW LAKES?

JOURNAL OF PHYCOLOGY, Issue 2000
H.J. Carrick
Factors that regulate phytoplankton dynamics in shallow, productive lakes are poorly understood, due to their predisposition for frequent algal blooms and sediment resuspension events. In Lake Apopka, greatest phytoplankton biomass reflects wind-induced resuspension of algae (meroplankton) that exists on the aphotic lake bottom in a layer approximately 5 cm thick; this assemblage is dominated by diatoms (>60% of total biomass) that can occur in resting stages. Once exposed to moderate light, meroplankton are capable of growth and photosynthetic rates comparable with surface populations. In Lake Okeechobee, remote sensing was used to assess the basin-wide distribution of suspended particles. Satellite reflectance values agreed well with in situ particle densities at 20 in-lake stations (average r2; LANDSAT = 0.81, AVHRR = 0.53), and maps of algal blooms (r2 = 0.79, p , 0.01). The greatest chlorophyll concentrations occurred in the vicinity of tributary nutrient inputs at the lake's perimeter, while turbidity increased towards the center of the lake reflecting predominant water circulation patterns. These results underscore the importance of physical-biological interactions in lakes. [source]

Effects of stocking density on the nutrient budget and growth of the western king prawn (Penaeus latisulcatus Kishinouye) in a recirculating aquaculture system

AQUACULTURE RESEARCH, Issue 10 2010
Le Van Khoi
Abstract Intensification in the commercial culture of prawns can have a significant impact on the water quality and hence on the survival, growth and the surrounding environment. The present study aims to evaluate the effects of stocking density on the water quality and performance of the western king prawns (Penaeus latisulcatus) and the nutrient budget of the culture environment. Four stocking densities of 4, 8, 16 and 32 prawns m,2 were tested in 12 recirculating systems. Prawn weight and specific growth rate increased with decreasing stocking density, while the survival rate showed the reverse trend. The mean total ammonia nitrogen, nitrate nitrogen, total phosphorus and soluble reactive phosphorus were significantly higher (P<0.05) at the higher stocking density. The nutrient budget revealed that the prawns could assimilate only 9.34,20.13% nitrogen and 4.97,11.25% phosphorus of the total nutrient inputs. The drained water at harvest was the major sink of phosphorus and nitrogen at stocking densities of 4, 8 and 16, which accounted for 45.59,64.82% and 44.28,65.62% of the total inputs, respectively, while a significant proportion of nitrogen sunk into the sediment at 32 prawns m,2. The study suggested that the stocking densities of western king prawns can be up to 16 prawns m,2 in the recirculating water environment. [source]

Alien and endemic flora at reference and non-reference sites in Mediterranean-type streams in Portugal

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 4 2007
Francisca C. Aguiar
Abstract 1.A comparison was made between a variety of alien and endemic plant species from 272 aquatic and riparian habitats in Portuguese Mediterranean-type streams in reference condition , i.e. near-natural river corridors , and non-reference condition. The objective was to detect differences in relative proportion and cover between these species groups. The differences in endemic and alien flora from siliceous and calcareous river types were also analysed. Environmental and human disturbance factors were related with the richness and cover of both species groups. 2.A total of 568 species were found, of which 44 were alien and 28 were endemic. Alien species were present at 91% of the surveyed locations, and were consistently more widespread at non-reference sites than at reference ones for both river types, with calcareous sites having a higher invasibility. Endemic species occurred at 45% of the sampling sites and displayed a significantly lower richness and cover than their alien counterparts. 3.Alien richness and cover were positively related to direct human disturbance within the river systems, and with floodplain uses such as urban occupation, intensive agriculture, and nutrient inputs. Endemic species also respond to anthropogenic variables, rather than to climatic and geographical ones, with richness and cover increasing as human impacts on fluvial systems and related floodplains decrease. 4.Comprehensive control of alien invasive species and the protection of endemic plant populations will require attempts at monitoring ecological river integrity, and the achievement of ,good ecological status' , one of the goals of the European Union's Water Framework Directive. Portuguese riparian areas must be managed in such a way as to protect the relatively few preserved riparian habitats by lowering the direct and indirect pressures in fluvial corridors and thus preventing future alien plant invasions. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Seasonality of hydrographic variables in a coastal lagoon: Mar Chiquita, Argentina

AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 4 2006
Jorge Marcovecchio
Abstract 1.The concentration and distribution of several hydrographical variables from Mar Chiquita coastal lagoon, Argentina, were measured monthly over a year in order to quantify their seasonal variations. Temperature, salinity, inorganic nutrient concentrations (nitrate, nitrite, phosphate, silicate) in the water column, and photosynthetic pigments (chlorophyll a and phaeopigments) in suspended particulate matter (SPM), were measured using internationally standardized analytical methods. 2.Agricultural use of land surrounding the coastal lagoon has been shown to be the main nutrient source, owing to the use of fertilizers for farming and the consequent leaching of the soils by freshwater runoff. 3.Two different hydrographical areas were identified within the coastal lagoon, one showing marine influence and the other dominated by inland influence (due to catchment and freshwater inputs), both with different characteristics and ecological behaviour. 4.The frequent occurrence of phytoplankton blooms has also been identified within the coastal lagoon. There was significant biological production (in terms of chlorophyll a) within the lagoon throughout the year. The lagoon appears to function as a transitional system, opportunistically benefiting from extra nutrient inputs which, together with other environmental conditions, results in a continuous food supply, useful to both marine and estuarine organisms. Consequently the system is important for numerous fish and shellfish species as a nursery area. Copyright © 2005 John Wiley & Sons, Ltd. [source]