In the Early 1900s, What Did It Mean for Cities to Be â€å“dryã¢â‚¬â?

Keywords

Phosphate looming crises, nutrients, N, P, Atlantic, Northward Sea, Rhine, seaweed community, extreme mega cities.

Introduction

Phosphorus (P) is ane of the common elements on earth and is essential for all living organisms. It forms part of DNA, nervus cells and the brain, bones, teeth and plays role in biochemical cycles like the Calvin cycle, Krebs Cycle, Glycolysis and Oxidative Phosphorylation, essential in the energy supply of plants and animals (Figure 1).

Figure 1: A very large number of dissimilar modules is active many key functions and biochemical pathways among else the energy carrier ATP (Salway 2006). All based on phosphate, which is a chemical compound of phosphorus, hydrogen and oxygen (Hengeveld 2012).

Each of usa excretes around 1.5 grams of phosphorus per 24-hour interval into sewage (Salway 2006), implying, with a population of 6 billion an annual use of three.iii billion-kilogram phosphate, which will increase to 5.5 billion-kilogram by 2050. Phosphate rock is the only economic source of P for product of phosphate fertilizers and phosphate chemicals. The current commercial reserves of phosphate rock are estimated at twoscore billion tons and are establish in the Us, People's republic of china, Republic of kazakhstan, Morocco, Republic of finland, South Africa, and some Pacific Islands, of which the first four are electric current production leaders with 72% of the total globe supply. These reserves are estimated to suffice for a 60-130 years supply at current usage and market prices (Zapata & Roy 2004). The relatively inexpensive phosphorus we use today will likely exist wearied within fifty years (Someus 2008), although estimates greatly vary (Van Vuuren et al 2010). The typical P2O5 content of phosphate rock is 30-xl% (=thirteen-17.5% P); simply with increasing demand, phosphate rock will increasingly be contaminated with impurities similar iron, volatile metals, chloride and copper (Schipper et al. 2004). These contaminants in fertilizer produced from rock, may be a more important driver for phosphorus recovery, so that the actual phosphate crisis may well be reached within fifty years (Someus 2008). Over 80% of the mined phosphate is used as fertilizer in agriculture (Zapata & Roy 2004; Hengeveld 2012). The phosphate, not incorporated in the crop, flushes abroad from the soil via the rivers to the oceans. Northward and P, whether the source is natural or (as present mostly) anthropogenic, cause eutrophication of the aquatic environs. Anthropogenic sources include direct run-off from state and dredge spoil/sewage sludge from the rivers to the seas like North Sea and Baltic Sea. Annually about 120 Gmol yr-1are lost from the watershed via rivers of which about 53 Gmol P are from large rivers (more often than not the Amazon) and the residuum from smaller rivers that flow into estuaries and shallow seas like Northward Body of water and Baltic Sea (Galloway et al. 1996). The Due north Body of water, with an expanse of 700,000 km2 is the virtually disturbed sea (Druon et al. 2004) and its major river contributors from the overpopulated European continent include the Elbe, Wieser, Ems, Rhine (Zobrist & Stumm 1981; De Klein 2007), Scheldt, Seine and Humber (Brion et al. 2004). Full annual inputs in the North Bounding main are 8870 ⌈ 4860 kt N and 494 ⌈ 279 kt P and information technology is concluded that for P this bounding main is a source for the Atlantic Body of water (-4 to 52 kt P year-one) (Brion et al. 2004). The Baltic Sea receives annually one meg tons of nitrogen and more than than xxx.000 tons of phosphorus (Helsinki Commission 2004). At this moment, the North Atlantic Body of water appears to accumulate P at a rate of nigh 0.1% per twelvemonth (Galloway et al. 1996) (Figure 2).

Figure 2: The marine phosphorus cycle. We suggest a new arroyo to extract P from the oceans for reuse on our terrestrial areas by accumulation them in "seaweed plantations" in the shallow seas and continental shelf and harvesting these macro algae before they disappear as inorganic phosphate for hundred thousands of years "out of the loop" in the infinite oceanic abyssal plain at 6 km depth (Modified: Paytan & McLaughlin 2007).

Therefore, phosphate recycling is essential for the sustainable futurity of our lodge, every bit it is inconceivable to continue to simply flush away a non-renewable resource that is essential for life, to the oceans. The best way to recycle phosphorus is agricultural re-use of sewage solids, merely logistic problems (lack of farmland effectually big cities), contamination with pollutants and consumer resistance apace reduce this option in many countries. In situations where agricultural re-use is non possible, industrial recycling of phosphates offers a sustainable solution (Schipper et al. 2004).

A new approach to excerpt P from the oceans for reuse on terrestrial areas might be accumulation in seaweeds and harvesting these macro-algae. In this enquiry we investigated the possibilities by measuring the N- and P-content of seaweed from contaminated waters (Netherlands, French republic, Ireland, Portugal) and one tropical seaweeds species from the Atlantic (Azores). We also measured the total Due north-content of seaweeds and ocean water. In addition we discuss the limitations of the N:P ratio of seaweeds as a useful biomarker for eutrophic seawaters.

Materials and Methods

Seaweeds

Fronds (5 replicates) of unlike species of bethic marine macrophyte (seaweeds) with dissimilar growth strategies and morphologies were collected from the upper and mid-littoral zone at 4 countries, in improver to one seawater sample. The post-obit seaweeds were collected with the location given:

-Eastern Scheldt, the netherlands (Ulva lactuca) (Chlorophyta), Approximate coordinates 51°32´30 N and iii°52´ Due east.

-Concarneaux, France, Ulva lactuca (Chlorophyta), Laminaria hyperbolia (Phaeophyceae), L. digitata (Phaeophyceae), Chondrus crispus (Rhodophyta), Fucus serratus (Phaeophycea), proximate coordinates 47°52´ Due north and iii°52´ E.

-Kilcar, Due west Donegal, Ireland (Laminaria digitata (Phaeophyceae), Undaria pinnatifidia (Phaeophyceae), Approximate coordinates 54°37´ Northward and viii°37´ Westward.

-Porto, Portugal (Chondrus crispus (Rhodophyta), Mastocarpus stellatus (Rhodophyta), Sargassum muticum (Phaeophyceae), Laminaria hyperbolia (Phaeophyceae), Gauge coordinates 41°32´thirty N and 9.5°42´ E.

-Norway, from the Island Solund, at the signal 61º.03' N, 4º52' E (Ascophyllym nodusum).

In addition we collected:

The tropical seaweed Sargassum natans (Phaeophyceae), by a whaler at the Atlantic Ocean at the point 37º 08.403 Due north/32º 22.591W.

Sampling seawater

A sample of the surrounding seawater of the seaweeds was taken while collecting the seaweeds and frozen on dry ice (-180ºC).

Dry weight seaweeds

Afterward collection, the seaweeds were brought every bit before long every bit possible to the laboratory. Nigh epiphytic material was removed; the seaweeds were rinsed apace with freshwater, air-dried, and oven-dried (i night at 60ºC and one nighttime at 105ºC) and weighed and the dry out affair content calculated.

N and P contents of seaweeds and seawater

After grinding the seaweeds to a fine pulverisation, Nt (N-total) and Pt (P-total) were measured on a SFA-NT/PT apparatus according to SW E1406 guidelines, Nts and P-PO4 analyses of seawater were performed on an SFA-CaCl2 apparatus according to SWV E1417 guidelines, P analysis was performed on an ICP-AES Thermo appliance co-ordinate to SWV E1304 guidelines, at the Chemical-Biological Laboratory for Soil Research, Wageningen Academy, Netherlands (modified: USEPA 2004).

Historical datasets Rhine River

In composing our historical dataset of the Rhine N Sea system depicted in Effigy 3 ---results paragraph-, we used the following datasets:

Figure iii: Historical datasets of nutrients (N & P) in the river Rhine. These nutrients nitrates (nitrogen compounds) for which a dataset is presented since ≈1842-2000 and phosphates with a dataset since ≈1880-2000 (for used datasets run into Material & Methods).

• Data before 1900 (after Clarke, 1924),

• Data betwixt 1928 and 1945 represent almanac averages measured at Rhenen, the Netherlands, calculated afterwards Biemond's reports 'The water supply of Amsterdam', 1940 I, p-210 and 1948, p. 110.

• Data afterward 1955 annual averages measured at Lobith (Intern. Comm. for Protection of the Rhine against Pollution 1972, 1976).

• Concentrations of of import nutrients in the Rhine and their long-term concentration changes (afterward Van Bennekom and Salomons, 1981).

• The total annual nutrient load of the North Body of water between 1995-2005 was on average 472 ± 37 meg kg N and 27.4 ± 37 million kg P (De Klein 2007).

Results

The river Rhine flows through a highly urbanized and intensively used agrarian region towards the North Ocean. Because extensive datasets regarding N and P dated to about the mid-19th century be information technology tin exist used as a scholarly example study of plush abatement measures to trap these nutrients and its effects in relation to the nowadays nutrient load on the North Body of water. Because the 'phosphate looming crises' will exist a miracle on a global scale, it is of import to spread this information of this well documented and historical datasets of this river Rhine N and P efflux towards the Northward body of water. This unique historical dataset comprises for nitrogen compounds a dataset roofing the menstruum ≈1842-2000 and for P-related phosphates a dataset covering the period ≈1880-2000. This Rhine River and North Ocean "case study" tin can already accept a scholarly impact on politicians, ecologists and biologists coping on our world with like problems of eutrophication of river systems and shallow seas and tremendous losses of the essential mineral Phosphorus. By combination of several datasets of the Rhine River (see Cloth & Methods), we were able to present a scholarly instance illustrating how the input of nutrients by rivers into the shallow seas like the North Sea has evolved through time in European regions because extensive data are available for the Rhine River since the midst 19th century. From the resulting both graphs depicted in Figure iii, it becomes clear that from the midst- 20th century the concentrations of these nutrients in the river Rhine has increased enormously reaching maximal levels in the eighties previous century of Nitrate concentrations effectually 350 μM while of [Phosphate] of effectually 13 μ (Figure iii). This is largely due to the intensive employ of chemical fertilizers in agriculture and inadequate wastewater treatment Also, major causes of the increase of both chemic compounds included a growing input from agriculture and industry as well as the belch of untreated urban sewage. Laundry detergent with phosphate additives to decalcify the launder h2o was a significant source of phosphates. In the eighties of the 20st century, counteractive political decisions/measures such as a ban on phosphate detergents and improved fertilizing techniques have been successful in significantly reducing the input since that time.. Appropriate measures were taken that have succeeded in consistently reducing the nutrient concentrations since the midst- 1980s followed by treatment of wastewater resulting in a further reduction. However response of the nutrients on a certain measure out is slow. Over a period of around 20-30 years nitrate concentrations declined and remained stable at around 350 μM while these of [Phosphate] remained stable around 13 μ giving ultimately the total annual food load of the N Body of water between 1995-2005 which was on average 472 ± 37 million kg N and 27.four ± 37 million kg P every bit basis for our calculations to trap this remaining part past a seaweed plantation on the North Sea as we volition work out in Table i and the next session of the Results paragraph and Discussion.

	Ds (%) (n=4-5)	Nt (1000/kg) (n=4-5)	Pt (chiliad/kg) (n=4-v)	North:P ratio (n=four-5)	Nt-water (mg/l) (north=1)	Pt-h2o (mg/l) (north=one)	P-PO4 water (mg/l) (n=1)
Netherlands Oosterschelde
Ulvalactuca	nineteen.8 ± 0.8	12.5 ± 2.4	1.v ± 0.ane	8.0 ± 0.ix	0.18	0.136	0.101
France Concarneaux
Ulvalactuca	xvi.three ± 1.six	12.5 ± ane.iii	0.ix ± 0.i	13.6 ± 0.vii	0.10	0.010	0.004
Laminariahyperbolia	12.0 ± 0.iv	9.0 ± 0.iii	0.viii ± 0.01	10.9 ± 0.2	0.10	0.010	0.004
Laminaria Digitata	17.1 ± 1.6	16.0 ± 1.2	1.4 ± 0.ii	11.half-dozen ± i.4	0.10	0.010	0.004
Chondruscrispus	xi.5 ± 0.8	16.1 ± 1.seven	1.1 ± 0.i	xiv.8 ± 1.0	0.10	0.010	0.004
Fucusserratus	21.eight ± one.7	14.half-dozen ± 0.six	0.vii ± 0.0	21.8 ± ane.0	0.10	0.010	0.004
Ireland Westward Donegal
Laminaria Digitata	25.8 ± 1.7	xi.8 ± 0.3	0.four ± 0.01	31.3 ± one.ii	0.14	0.01	0.002
Undaria Pinnatifidia	9.2 ± 5.2	21.ii ± 0.7	ane.1 ± 0.01	xix.1 ± 0.v	0.14	0.01	0.002
Palmaria palmate	21.7 ± 0.012	27.vii ± 0.four	23.three ± 0.03	eleven.half dozen ± 0.1	0.xiv	0.01	0.002
Norway Ascophyllymnodusum	29.eight ± 0.008	viii.i ± 0.9	0.5 ± 0.1	xv.1 ± 1.1	0.17	0.01	0.014
Portugal Porto
Chondruscrispus	33.2 ± 0.18	36.5 ± 0.8	2.8 ± 0.half dozen	13.7 ± 2.7	0.23	0.01	0.003
Mastocarpus stellatus	33.one ± 1.0	41.1 ± 0.four	ane.9 ± 0.03	22.2 ± 0.5	0.23	0.01	0.003
Sargassum muticum	17.ane ± 1.one	31.eight ± 0.6	two.8 ± 0.04	eleven.ii ± 0.two	0.73	0.05	0.007
Laminaria hyperbolia	fourteen.5 ± 1.4	xviii.0 ± 0.3	three.8 ± 0.09	4.vii ± 0.06	0.73	0.05	0.007
Gracilaria SP.	17.two ± 0.iv	58.ii ± 2.v	6.v ± 0.2	8.9 ± 0.3	0.21	0.00	0.005
Atlantic Sargassumnatans	xviii.5 ± two.iv	9.8 ± 0.7	one.1 ± 0.09	9.2 ± 0.2	1.00	0.03	0.027

Table one: Dry affair content (Ds), total-N, full-P and N: P ratio of several seaweeds collected around the North Sea (Netherlands, France, Ireland, Portugal) and the Atlantic Ocean (Sargassumnatans).

Discussion

In contempo years there has been an increased production of large seaweeds in shallow littoral waters. These macro-algae are by and large green seaweeds like Ulva spp. (Sawyer 1956; Ménesguen & Piriou 1995; Sorokin et al. 2002). This can be ascribed to their ability to survive in fluctuating environments and their ability to take upwards and store nutrients similar N and P. Seaweed-based ecosystems are amidst the most productive on Earth (Mann et al. 1980, Leigh et al. 1987). Therefore, these systems could probably serve as a sink to trap nutrients in shallow eutrophic seas like the Baltic, Adriatic and North Sea, to which N and P are delivered past rivers like the Rhine, in gild to avoid farther eutrophication of our oceans. Enhanced growth of seaweeds has been observed under certain conditions in coastal marine waters polluted by sewage (Causey et al. 1945, Sawyer 1956; Tewari et al. 1972). Also in disturbed food-rich systems like those in in Brittany (French republic) (Ménesguen and Pirriou 1995) and the Venice lagoon (Sorokin et al. 2002) Ulva spp. can blossom. On a global scale "green tides" are overwhelming the coastline of our planet Earth, mainly in Asia (Ye et al 2011). A recent report of Wichard et al (2015) -and references therein- reviews the literature for these Ulva blooms or "green tides" on a global scale: indications for eutrophic, hypoxic and disturbed ecosystems. Many aquatic ecosystems are threatened or affected by eutrophication. Here, eutrophication refers to the process by which water bodies learn loftier nutrient concentrations (in particular phosphates and nitrates) typically followed by excessive growth and decay of plants (algae) in the surface water. It may occur naturally (e.g. in deep waters) but is most often the result of pollution related to human being action, such every bit fertilizer runoff and sewage discharge and the atmospheric deposition of nitrogen compounds. This process has been linked to serious losses of fish stocks and other aquatic life (e.g. Smith 2003).Eutrophication may cause hypoxia, a country whereby aquatic ecosystems lack sufficient oxygen to support nigh forms of life, producing 'dead zones' (Rabalais et al. 2010). In marine ecosystems, about dead zones have developed forth coasts since the 1960s due to environmental pollution associated with human activities. 'Dead zones' are especially common along the coasts of Europe, North America and east Asia. Many are concentrated near the estuaries of major rivers, and result from the build-up of nutrients carried from inland agricultural areas. So our suggestions are to avert eutrophication of our marine h2o–peculiarly in case no major river effluent system exist like in Europe the river Rhine/North Bounding main organisation-which enables countries to build sewage treatment facilities. Hence, for these global regions without major river organization we advise to trap abundant nutrients by seaweed civilization e.g. of Ulva species (Wichard et al 2015). Seaweed growth is affected by season, temperature, (Duke et al. 1989a,b); light, (Lapointe & Tenore 1981; Couthino & Zingmark 1993), the availability of suitable substrates and shading and circannual rhytms and major factors like nutrient availability for counterbalanced growth are of import (Atkinson and Smith 1983; Cabioc'h et al 2006; Hurd et al 2014). Moreover, the surface to volume ratio may vary amongst seaweed species and may have an bear on on photosynthetic chapters and nutrient uptake (reviewed: Hurd et al 2014).

To assemble information well-nigh the effects of nutrients on seaweed growth rate and the possibility if seaweeds can be used to trap phosphorus and by harvesting return this chemical compound to terrestrial agroecosystems, nosotros made a study at the N : P ratio in seaweeds.

The mean C: N: P ratio of 92 benthic constitute samples from five phyla, sampled at nine locations worldwide is near 700:35:1; the median is well-nigh 550:thirty:1 (Atkinson and Smith 1983). In this report, the limiting value for the N: P ratio was 16, the median xxx and the mean 35. These values provide a basis for estimating their threshold values.

In general, for seaweeds an N: P ratio<10 indicates a relative N-limitation while an N : P ratio > 30 points to a relative P limitation (Atkinson and Smith 1983; Smith 1984).

According to the Bjönsäter & Wheeler's (1990) nomenclature of macroalgal food status, based on N : P ratios in their tissue, a Northward: P ratio<16 indicates a relative N-limitation; an ratio of 16- 24 indicates a balanced availability of both elements - i.e., no limitation and N: P>24 indicates a relative P-limitation

In only one extensive study, N: P ratios of fronds of unlike species of benthic marine macrophytes (22 macroalgae and i seagrass) were investigated (Hernandéz et al. 1999). The N: P ratio in 20 seaweeds was in the range of ten-20 which indicates N- and P-sufficiency. Only Cladophora rupestris and Ceramium nodolosum (from Tyne Sands, southeast Scotland) showed Due north: P ratios of respectively 44.vii ± iii.4 and 34.6 ± 1.5 which points to a relative P limitation (Hernandéz et al. 1999). In the study of Prince (1974) on Fucus vesiculosus (brown seaweed) and Enteromorpha linza (dark-green seaweed) Northward:P ratios were found of respectively 45 and 39, indicating a relative P limitation.

In a long-term written report in a tropical environment (Guanabara Bay, S-eastern Brazil) ten species of seaweeds (half-dozen green and iv cherry-red algae) were monitored from 1997 to 2004. Wide variations in total dissolved nitrogen concentrations and Due north: P ratios were recorded; however, no seasonal tendency was detected (Lourenço et al. 2006). Tissue N: P ratios were predominantly >20, while the highest value was found for Ulva lactuca (56.viii) which points to a relative P-limitation and the everyman value for Chondracanthus teedii (13.half-dozen), a threshold value for relative N-limitation (Lourenço et al. 2006).

However, Lourenço et al. (2006) caution against the N: P ratio studies performed in tropical environments (Fong et al. 2003), because their results are similar to those of studies with seaweeds growing under backlog nutrient availability (Lapointe et al. 2004). The loftier hateful overall North: P ratio observed in Guanabara Bay (Brazil) in summer 2004 (32.seven ± 10.7, north=43) is strongly afflicted by the high concentrations of nitrogen and is non necessary indicative of P limitation (Lourenço et al. 2006).

So, it is important to use the N: P ratio as a biomarker only in cases when the nitrogen content of the tissue is not fluctuating during the season. Iwasaki and Matsudaira (1954) found that the nitrogen concentration in the tissue of Porphyra tenera exhibited a marked seasonal fluctuation, causing the N : P ratio to vary between seven.two and 28.2. Likewise in the report of Wheeler and Björnsäter (1992), seasonal fluctuations were observed in N: P ratio for five seaweeds from Oregon (Northwest Pacific). The selection of the fourth dimension scale where seaweeds has to be exposed to stable food exposure to accept a valuable N: P ratio equally biomarker is rather complex due establish physiological characteristics. Seaweeds are adapted to stressful environments with variable supply of nutrients such as N (Duke et al. 1989a). It appears that many seaweeds can control the transient nitrate availability past means of active transport systems that atomic number 82 to luxury uptake, saturating the nitrate and nitrite reductase systems and leading to nitrate accumulation inside vacuoles (Hurd et al. 2014). In the report of Lourenço et al. (2005, 2006), N concentrations in the seaweeds advise that the species are permanently saturated with nitrogen. Ulva spp. tin control nitrate availability for approximately 40 days. North tin can be temporarily stored in photosynthetic pigments and Rubisco molecules (Knuckles et al. 1989), which allows these macroalgae to maintain active growth for at least 3 weeks after nitrate depletion in the medium (Viaroli et al. 1996). This procedure, however, is of importance merely in disturbed systems with strongly fluctuating nutrient contents such as Brittany (France) (Ménesguen and Pirriou 1995) and the Venice lagoon (Sorokin et al. 2002). This ability of seaweeds similar Ulva to shop nitrogen for several weeks (Duke at al. 1989a, Viaroli et al. 1996) is in contrast to the suggestion of Ryther and Dunstan (1971) that nitrogen is ofttimes the major limiting nutrient for algal growth in coastal marine waters were phosphate is plant generally in excess. Overall, in temperate eutrophic "stable" seas and large h2o bodies with stable nitrogen concentrations we can await that the N : P ratio is a useful biomarker for eutrophication if regularly sampled (in combination with water analysis). The ability of Ulva spp. (Viaroli et al. 1996) and other seaweeds to store P and N may have substantial effects on the growth of seaweeds, only also offers an opportunity for these species to act as a sink to eliminate P and N from eutrophic shallow seas.

Finally we give based on our nutrient measurements at the Northward Sea seaweeds an estimation how big the surface area of seaweed civilization has to be, to trap the almanac load of the Northward Ocean of P and Northward to oppose the eutrophication of this shallow ocean and consequently the Atlantic Sea. The total almanac food load of the Northward Sea between 1995-2005 was on average 472 ± 37 million kg North and 27.4 ± 37 million kg P (De Klein 2007). Seaweed communities are complex ecological systems in which different seaweed species interact and the results of these interactions may vary in fourth dimension and space (Hurd et al. 2014 Bhang and Kim 2000,). An example of such a seaweed community–based on observations along the declension of Bretagne (France) is depicted in Figure iv. Data about seaweed- ecosystems –communities and its interactions between the dissimilar seaweed species are scarce simply are an absolute prerequisite to use them in hereafter studies as a sequestering sink for nutrients like P (but likewise N) in the shallow seas like the North-sea before the eutrophicated water originating from populated areas like Western Europe reaches the Atlantic oceans (Figure ii).

Effigy 4: The vertical distribution of seaweeds in an ecosystem for the coast of Brest (France) (modified from: Cabioc'h et al 2006).

Conclusion

Excreted P reaches via sewage P rivers like the Rhine -which nowadays behave a total almanac load of 472 1000000 kg Northward and 27.4 one thousand thousand kg P (De Klein 2007)-to swallow coastal waters like the North Sea (57,000 km2) (Zobrist & Stumm 1981). Ultimately it will vanish in the Atlantic Ocean where it will deposit at an abyssal depth of ≈ 6,000 m unreachable to bring it back to country and 'shut the P-loop' (Paytan & McLaughlin 2007). We suggest to trap these nutrients already in urbanized area'south which is for 50% accomplished in the Rhine since 1972 and the remaining office by plantations of bogus seaweed communities planted until 10 meters depth. Based on Northward & P data of several seaweed species around the North Body of water we calculated that to trap the nowadays remaining outflow of N and P respectively, 2114 ha (three.71%) and 1758 ha (3.08%) of the Dutch North Bounding main surface should be planted. The basin is perchance the most heavily industrialized in the earth. The Rhine with a bowl area of 220,000 km² crosses Central Europe with i of the most intensive agricultural and industrial activity in the globe. Although the stream flow of the Rhine comprises only about 0.2 per cent of the period of all worldwide rivers information technology carries the waste material of 41.4 × 106 inhabitants and almost x to 20 per cent of the total Western chemical industry (OECD countries) is located in its bowl. Then extending knowledge in nutrient management in the river and our suggestions concerning "seaweed plantations" might be important for other river basins considering the "looming phosphorus crises" is a global problem. Particularly in Southeast Asia, rivers convey agronomical nutrients and untreated wastewater to the oceans. In many areas this causes a massive proliferation of algae. In some regions entire habitats are altered. Efforts to curtail the flood of nutrients accept been successful in some parts of Europe, but worldwide the state of affairs is growing worse.rivers are carrying more than and more than nutrients to the oceans, and experts expect this trend to continue (Ye et al. 2011). Especially in Asia in the 21st Century with its megacities see Effigy 5, where more than half of the world population will live our "river Rhine/North-Body of water model with seaweed plantations" might be an affordable, sustainable, environmental friendly method to cope with the "looming phosphorus crises".

Effigy five: Eutrophic areas are those with excessive nutrients (orange dots), putting them at risk of adverse effects. Hypoxic areas are those where oxygen levels in the water are already depleted and agin effects expected due to nutrient and or organic pollution (red dots). Blue dots are systems that were hypoxic at one fourth dimension only are recovering (Source: World Resources Institute 2011).

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