The world's largest macroalgal bloom in the Yellow Sea, China: Formation and implications
TL;DR: The world's largest trans-regional macroalgal blooms during 2008-2012 occurred in the Yellow Sea, China as discussed by the authors, and the causes, development and future challenges in this unique case were addressed.
Abstract: The world's largest trans-regional macroalgal blooms during 2008-2012 occurred in the Yellow Sea, China. This review addresses the causes, development and future challenges in this unique case. Satellite imagery and field observations showed that the macroalgal blooms in the Yellow Sea originated from the coast of Jiangsu province and that favorable geographic and oceanographic conditions brought the green macroalgae from the coast offshore. Optimal temperature, light, nutrients and wind contributed to the formation and transport of the massive bloom north into the Yellow Sea and its deposition onshore along the coast of Shandong province. Morphological and genetic evidence demonstrated that the species involved was Ulva prolifera, a fouling green commonly found growing on structures provided by facilities of Porphyra aquaculture. Large scale Porphyra aquaculture (covering >20,000 ha) along the Jiangsu coast thus hypothetically provided a nursery bed for the original biomass of U. prolifera. Porphyra growers remove U. prolifera from the mariculture rafts, and the cleaning releases about 5000 wet weight tonnes of green algae into the water column along the coast of Jiangsu province; the biomass then is dispersed by hydrographic forcing, and takes advantage of rather high nutrient supply and suitable temperatures to grow to impressive levels. Certain biological traits of U. prolifera -efficient photosynthesis, rapid growth rates, high capacity for nutrient uptake, and diverse reproductive systems- allowed growth of the original 5000 tonnes of U. prolifera biomass into more than one million tonnes of biomass in just two months. The proliferation of U. prolifera in the Yellow Sea resulted from a complex contingency of circumstances, including human activity (eutrophication by release of nutrients from wastewater, agriculture, and aquaculture), natural geographic and hydrodynamic conditions (current, wind) and the key organism's biological attributes. Better understanding of the complex biological-chemical-physical interactions in coastal ecosystems and the development of an effective integrated coastal zone management with consideration of scientific, social and political implications are critical to solving the conflicts between human activity and nature. (c) 2013 Elsevier Ltd. All rights reserved.
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TL;DR: Harvesting the macroalgae, a valuable raw material, before they beach could well be developed into an effective solution to solve the problem of sudden beaching of huge seaweed masses.
Abstract: Sudden beaching of huge seaweed masses smother the coastline and form rotting piles on the shore. The number of reports of these events in previously unaffected areas has increased worldwide in recent years. These 'seaweed tides' can harm tourism-based economies, smother aquaculture operations or disrupt traditional artisanal fisheries. Coastal eutrophication is the obvious, ultimate explanation for the increase in seaweed biomass, but the proximate processes that are responsible for individual beaching events are complex and require dedicated study to develop effective mitigation strategies. Harvesting the macroalgae, a valuable raw material, before they beach could well be developed into an effective solution.
579 citations
21 Jun 2016
TL;DR: While cost-effective methods for sea cucumber aquaculture close to their point of consumption is good news for wild stocks of sea cucumbers in different parts of the world, there is a potential downside in the environmental impact of such extensive production methods.
Abstract: Sea cucumber aquaculture has flourished as a result of increasing demand coupled with declining wild fisheries and has been facilitated by technical progress in the production and grow-out phase of larvae and small juvenile sea cucumbers. China has developed a large and successful sea cucumber aquaculture industry based on the temperate species Apostichopus japonicus (Selenka, 1867). China consumes most of its domestic sea cucumber production (193, 705 tons: 2013), exporting only a few dozen tons. Much of the success of sea cucumber aquaculture in China came from advances in culture methods, especially for the early stages of broodstock conditioning, larval production and settlement, and the critical early juvenile development stage. These artificial approaches to production are a precondition for all aquaculture models, and the scientific procedures and management protocols must be strictly adhered to for success. Similarly, the grow-out phase of sea cucumber production in China has evolved from ...
163 citations
Cites background from "The world's largest macroalgal bloo..."
...Macroalgal blooms, caused by Ulva prolifera, have become an annually recurrent feature in the Yellow Sea, and these have caused significant economic damage to sea cucumber aquaculture (Liu et al., 2013)....
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TL;DR: With physical and biological changes occurring at unexpected pace, marine phycologists should integrate and join their research efforts to be able to contribute efficiently for the conservation and management of coastal systems.
162 citations
TL;DR: Wang et al. as discussed by the authors found that macroalgal wastes from the connecting ropes of Porphyra aquaculture rafts contributed significantly to the original biomass of free-floating green algae.
Abstract: To discover the original source and clarify development of the world's largest transregional green tides in the Yellow Sea, an integrated investigation covering the Subei Shoal coastal waters and the adjacent regions was carried out during March to June of 2012. The results showed that macroalgal wastes from the connecting ropes of Porphyra aquaculture rafts contributed significantly to the original biomass of free-floating green algae. Approximately 6500t of Ulva prolifera were released into the coastal waters from mid-April to late-May when farmers were cleaning aquaculture facilities. Among the total biomass disposed, about 62.3% floated up to the sea surface, which turned into the original floating patches. The floating U. prolifera, with a high growth rate of 26.3% per day, dominated in the floating algal patches rapidly, moved northward under the hydrodynamic action, and formed a massive free-floating green tide near the south of Shandong peninsula in early June. The optimal sea temperature and sufficient nutrients in the Yellow Sea facilitated the formation of the green tide. No other source contributing substantially to the initial floating biomass was detected in the survey except those from the connecting ropes of rafts. Based on our field data, we concluded that the green tide in Yellow Sea is a transregional disaster stimulated directly by the unhygienic husbandry and maintenance practices of coastal aquaculture.
159 citations
TL;DR: China is facing intense coastal eutrophication, and large-scale seaweed aquaculture in China is popular, now accounting for over 2/3’s of global production, and it is projected this industry will remove 100% of the current phosphorus inputs to Chinese coastal waters by 2026.
Abstract: China is facing intense coastal eutrophication. Large-scale seaweed aquaculture in China is popular, now accounting for over 2/3’s of global production. Here, we estimate the nutrient removal capability of large-scale Chinese seaweed farms to determine its significance in mitigating eutrophication. We combined estimates of yield and nutrient concentration of Chinese seaweed aquaculture to quantify that one hectare of seaweed aquaculture removes the equivalent nutrient inputs entering 17.8 ha for nitrogen and 126.7 ha for phosphorus of Chinese coastal waters, respectively. Chinese seaweed aquaculture annually removes approximately 75,000 t nitrogen and 9,500 t phosphorus. Whereas removal of the total N inputs to Chinese coastal waters requires a seaweed farming area 17 times larger than the extant area, one and a half times more of the seaweed area would be able to remove close to 100% of the P inputs. With the current growth rate of seaweed aquaculture, we project this industry will remove 100% of the current phosphorus inputs to Chinese coastal waters by 2026. Hence, seaweed aquaculture already plays a hitherto unrealized role in mitigating coastal eutrophication, a role that may be greatly expanded with future growth of seaweed aquaculture.
148 citations
References
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TL;DR: In this paper, the authors review features of macroalgal blooms pointed out in recent literature and summarize work done in the Waquoit Bay Land Margin Ecosystems Research project which suggests that nutrient loads, water residence times, presence of fringing salt marshes, and grazing affect macroalgae blooms.
Abstract: Macroalgal blooms are produced by nutrient enrichment of estuaries in which the sea floor lies within the photic zone. We review features of macroalgal blooms pointed out in recent literature and summarize work done in the Waquoit Bay Land Margin Ecosystems Research project which suggests that nutrient loads, water residence times, presence of fringing salt marshes, and grazing affect macroalgal blooms. Increases in nitrogen supply raise macroalgal N uptake rates, N contents of tissues, photosynthesis-irradiance curves and P max , and accelerate growth of fronds. The resulting increase in macroalgal biomass is the macroalgal bloom, which can displace other estuarine producers. Fringing marshes and brief water residence impair the intensity of macroalgal blooms. Grazing pressure may control blooms of palatable macroalgae, but only at lower N loading rates. Macroalgal blooms end when growth of the phytoplankton attenuates irradiation reaching the bottom. In estuaries with brief water residence times, phytoplankton may not have enough time to grow and shade macrophytes. High phytoplankton division rates achieved at high nutrient concentrations may compensate for the brief time to divide before cells are transported out of the estuary. Increased N loads and associated macroalgal blooms pervasively and fundamentally alter estuarine ecosystems. Macroalgae intercept nutrients regenerated from sediments and thus uncouple biogeochemical sedimentary cycles from those in the water column. Macroalgae take up so much N that water quality seems. high even where N loads are high. Macroalgal C moves more readily through microbial and consumer food webs than C derived from seagrasses that were replaced by macroalgae. Macroalgae dominate O 2 profiles of the water columns of shallow estuaries and thus alter the biogeochemistry of the sediments. More frequent hypoxia and habitat changes associated with macroalgal blooms also changes the abundance of benthic fauna in affected estuaries. Approaches to remediation of the many pervasive effects of macroalgal blooms need to include interception of nutrients at their watershed sources and perhaps removal by harvest of macroalgae or by increased flushing. Although we have much knowledge of macroalgal dynamics, all such management initiatives will require additional information.
1,281 citations
"The world's largest macroalgal bloo..." refers background in this paper
...The cause of green tides has generally been attributed to poor water quality, e.g., eutrophication from agricultural runoff or urban-derived pollution, which can lead to overgrowth of macroalgae (Sfriso et al., 1987; Fletcher, 1996; Valiela et al., 1992, 1997)....
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...Waterways and valuable habitats can be choked or damaged by high macroalgal biomass; noxious odors (NH3, H2S) and anoxic conditions produced by algal decay can impact tourism and lead tomassive fish and shellfish kills (Valiela et al., 1992, 1997; Raffaelli et al., 1998; Nelson et al., 2008)....
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...…adaptive capacity of green algae to the variable environment in the intertidal zone (e.g., temperature, salinity and light) and decreased herbivore control of algal biomass can significantly contribute to the formation of green tides (Valiela et al., 1997; Lotze et al., 2000; Worm and Lotze, 2006)....
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...Fast growing marine algae associated with most algal blooms have higher nitrogen demand than slow growing species (Valiela et al., 1997; Pedersen and Borum, 1997), as seen in laboratory culture experiments with Ulva prolifera in the Yellow Sea (Table 3)....
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...In general, Ulva spp. associated with most green tide events display a close positive correlation to dissolved inorganic nitrogen (DIN), where growth increased with increasing DIN concentration (Sfriso et al., 1987; Valiela et al., 1997; Morand andMerceron, 2004; Teichberg et al., 2010)....
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TL;DR: In this paper, a series of subwatersheds of Waquoit Bay was studied to investigate the coupling of land to marine systems, and it was found that the increased macroalgal biomass dominates the bay ecosystem through second or third-order effects such as alterations of nutrient status of water columns and increasing frequency of anoxic events.
Abstract: Human activities on coastal watersheds provide the major sources of nutrients entering shallow coastal ecosystems. Nutrient loadings from watersheds are the most widespread factor that alters structure and function of receiving aquatic ecosystems. To investigate this coupling of land to marine systems, we are studying a series of subwatersheds of Waquoit Bay that differ in degree of urbanization and hence are exposed to widely different nutrient loading rates. The subwatersheds differ in the number of septic tanks and the relative acreage of forests. In the area of our study, groundwater is the major mechanism that transports nutrients to coastal waters. Although there is some attenuation of nutrient concentrations within the aquifer or at the sediment-water interface, in urbanized areas there are significant increases in the nutrient content of groundwater arriving at the shore’s edge. The groundwater seeps or flows through the sediment-water boundary, and sufficient groundwater-borne nutrients (nitrogen in particular) traverse the sediment-water boundary to cause significant changes in the aquatic ecosystem. These loading-dependent alterations include increased nutrients in water, greater primary production by phytoplankton, and increased macroaglal biomass and growth (mediated by a suite of physiological responses to abundance of nutrients). The increased macroalgal biomass dominates the bay ecosystem through second- or third-order effects such as alterations of nutrient status of water columns and increasing frequency of anoxic events. The increases in seaweeds have decreased the areas covered by eelgrass habitats. The change in habitat type, plus the increased frequency of anoxic events, change the composition of the benthic fauna. The data make evident the importance of bottom-up control in shallow coastal food webs. The coupling of land to sea by groundwater-borne nutrient transport is mediated by a complex series of steps; the cascade of processes make it unlikely to find a one-to-one relation between land use and conditions in the aquatic ecosystem. Study of the process and synthesis by appropriate models may provide a way to deal with the complexities of the coupling.
598 citations
"The world's largest macroalgal bloo..." refers background in this paper
...The cause of green tides has generally been attributed to poor water quality, e.g., eutrophication from agricultural runoff or urban-derived pollution, which can lead to overgrowth of macroalgae (Sfriso et al., 1987; Fletcher, 1996; Valiela et al., 1992, 1997)....
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...Waterways and valuable habitats can be choked or damaged by high macroalgal biomass; noxious odors (NH3, H2S) and anoxic conditions produced by algal decay can impact tourism and lead tomassive fish and shellfish kills (Valiela et al., 1992, 1997; Raffaelli et al., 1998; Nelson et al., 2008)....
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TL;DR: Preliminary results provide strong evidence that Ulva, Enteromorpha and Chloropelta are not distinct evolutionary entities and should not be recognized as separate genera.
Abstract: Ulva, one of the first Linnaean genera, was later circumscribed to consist of green seaweeds with distromatic blades, and Enteromorpha Link was established for tubular forms. Although several lines of evidence suggest that these generic constructs are artificial, Ulva and Enteromorpha have been maintained as separate genera. Our aims were to determine phylogenetic relationships among taxa currently attributed to Ulva, Enteromorpha, Umbraulva Bae et I.K. Lee and the monotypic genus Chloropelta C.E. Tanner, and to make any nomenclatural changes justified by our findings. Analyses of nuclear ribosomal internal transcribed spacer DNA (ITS nrONA) (29 ingroup taxa including the type species of Ulva and Enteromorphat, the chloroplast-encoded rbcL gene (for a subset of taxa) and a combined data set were carried out. All trees had a strongly supported clade consisting of all Ulva, Enteromorpha and Chloropelta species, but Ulva and Enteromorpha were not monophyletic. The recent removal of Vmbraulva olivascens (PJ.L...
568 citations
"The world's largest macroalgal bloo..." refers background in this paper
...This species was earlier known as Enteromorpha prolifera (O.F. Müller) (Hayden et al., 2003; andwww. algaebase.org)....
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TL;DR: In this paper, stable isotope ratios of N in groundwater and producers from the Waquoit Bay watershedestuary system, Cape Cod, Massachusetts were compared to explore this link, and the ability to identify effects of increasing wastewater N loads on 615N of estuarine producers may provide a means to reliably identify incipient eutrophication in coastal waters.
Abstract: It is clear that anthropogenic nitrogen inputs from watersheds to estuaries stimulate eutrophication. It has been difficult, however, to explicitly link anthropogenic N entering estuaries to N found in estuarine producers. To explore this link, we compared stable isotope ratios of N in groundwater and producers from the Waquoit Bay watershedestuary system, Cape Cod, Massachusetts. The 615N values of groundwater nitrate within the Waquoit Bay watershed increase from -0.9%0 to + 14.9%0 as wastewater contributions increase from 4 to 86% of the total N pool. As a result, the average S’“N of dissolved inorganic nitrogen (DIN, nitrate + ammonium) received by different estuaries around Waquoit Bay increases from +0.5%0 to +9.5%0. This increase is strongly correlated to increases in S”N of eelgrass, macroalgae, cordgrass, and suspended particulate organic matter. The increase of all producers examined in Waquoit Bay with increasing S15N of DIN in groundwater demonstrates a tight coupling between N contributed to coastal watersheds and N used by primary producers in estuaries. The ability to identify effects of increasing wastewater N loads on 615N of estuarine producers may provide a means to reliably identify incipient eutrophication in coastal waters.
510 citations
"The world's largest macroalgal bloo..." refers background in this paper
...…anthropogenically enriched organic matter from farm runoff, animal, and human wastes can result in elevated levels of isotopically heavy nitrate in seawater (d15N ¼ 10e25&) and could leave a signature in the thalli of algae (McClelland and Valiela, 1998; Cole et al., 2005; Teichberg et al., 2010)....
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TL;DR: In this paper, marine macroalgae Enteromorpha prolifera was converted to bio-oil by hydrothermal liquefaction in a batch reactor at temperatures of 220−320 °C.
Abstract: Marine macroalgae Enteromorpha prolifera, one of the main algae genera for green tide, was converted to bio-oil by hydrothermal liquefaction in a batch reactor at temperatures of 220−320 °C. The liquefaction products were separated into a dichloromethane-soluble fraction (bio-oil), water-soluble fraction, solid residue, and gaseous fraction. Effects of the temperature, reaction time, and Na2CO3 catalyst on the yields of liquefaction products were investigated. A moderate temperature of 300 °C with 5 wt % Na2CO3 and reaction time of 30 min led to the highest bio-oil yield of 23.0 wt %. The raw algae and liquefaction products were analyzed using elemental analysis, Fourier transform infrared (FTIR) spectroscopy, gas chromatography−mass spectrometry (GC−MS), and 1H nuclear magnetic resonance (NMR). The higher heating values (HHVs) of bio-oils obtained at 300 °C were around 28−30 MJ/kg. The bio-oil was a complex mixture of ketones, aldehydes, phenols, alkenes, fatty acids, esters, aromatics, and nitrogen-cont...
503 citations
"The world's largest macroalgal bloo..." refers background or methods in this paper
...Lately, a few scientists explored the uses of U. prolifera for bio-oil production, considering the tremendous biomass in the green tides of the Yellow Sea (e.g., Li et al., 2010a,b; Zhou et al., 2010, 2012; Zhuang et al., 2012)....
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...U. prolifera is converted to bio-oil by hydrothermal liquefaction, and the bio-oil yield up to 23.0 wt% (calculated on the feed) was obtained at 300 C, with a reaction time of 30 min and the addition of 5 wt% Na2CO3 (Zhou et al., 2010, 2012)....
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