Spatial and temporal distributions of Secchi depths and chlorophyll a concentrations in the Suo Nada of the Seto Inland Sea, Japan, exposed to anthropogenic nutrient loading

Nishijima, Wataru; Umehara, Akira; Sekito, Satoshi; Okuda, Tetsuji; Nakai, Satoshi

doi:10.1016/j.scitotenv.2016.07.020

Cited by 21 publications

(9 citation statements)

References 13 publications

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“…Likewise, the lagoon receives several urban and industrial discharges from the around cities, other than the sediments from the rivers 24 . Unlike the BL, Secchi depth obtained in the BB occurs in the water depths greater than 20 m as indicated by 25 . The salinity value in the BL is similar to that recorded by 26,27 .…”

Section: Discussionmentioning

confidence: 91%

Effect of Lagoon and Sea Water Depth on Gracilaria gracilis Growth and Biochemical Composition in the Northeast of Tunisia

Mensi

Nasraoui

Bouguerra³

et al. 2020

Sci Rep

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This study evaluated the growth and biochemical composition of farming Gracilaria gracilis (Stackhouse) M. Steentoft, L. M. Irvine & W. F. Farnham in the Bizerte Lagoon (BL) and Bizerte Bay (BB) in the North Coast of Tunisia, using lantern nets. Effects of site and depth on alga daily growth rate (DGR) and biochemical composition were investigated. The DGR was affected by culture site (1.42 ± 0.65% day −1 and 1.19 ± 0.34% day −1 for the BL and the BB respectively). Agar yield, was higher (p < 0.05) in the BB than the BL (23.31 ± 2.64% vs. 19.19 ± 2.32%) with a higher (p < 0.05) 3,6-anhydrogalactose (3,6-AG) contents (41.37 ± 3.68% vs 23.30 ± 5.40%) and a lower (p < 0.05) sulphate degree (6 ± 2.00% vs 8.80 ± 0.86%). The proteins contents were independent of the site and depth of culture (20.74 ± 7.22% and 22.02 ± 6.34% for the BL and the BB respectively). R-phycoerythrin (R-PE) contents were significantly higher (p < 0.05) in the BB (0.86 ± 0.31 mg g −1) than those obtained in the BL (0.33 ± 0.12 mg g −1). The salinity, transparency, nitrate and ammonium were monitored in both sites, and their influences were discussed. Our results suggest that G. gracilis cultured in Bizerte Bay can be used in a cascading biorefinery approach. Global seaweed production, largely derived from aquaculture (96.5 percent by volume of the wild-collected and cultivated aquatic plants combined), has changed considerably since 2005 1. This production increased from 13 million in 2005 to reach 30 million tons (live weight) in 2016. Moreover, 99% of the world's production comes from Asian countries, notably China (47.9%), Indonesia (38.7%), Philippines (4.7%), Republic of Korea (4.5%), Democratic People's Republic of Korea (1.6%), Japan (1.3%) and Malaysia (0.7%). Furthermore, trade in aquatic plants increased from USD 60 million in 1976 to more than USD 1 billion in 2016, with Indonesia, Chile and the Republic of Korea the major exporters, and China, Japan and the United States of America the leading importers. Accordingly, red seaweed production accounts for 53% of the world production 1. The most exploited red algae, expressed in a million tons year −1 , are Euchema seaweeds nei and Eucheuma spp. (10.5), Gracilaria spp. (4.1) and Porphyra spp. (1.3). In contrast, the red alga Gracilaria spp. was barely farmed at all in 1990. However, the increase in Gracilaria spp. production, by aquaculture, is mainly due to the growing demand for agar. Consequently, Gracilaria spp. aquaculture has been initiated by many countries, in different regions of the world, such as Thailand, Chile, Vietnam, Portugal, Australia, Brazil and India 2. The red alga Gracilaria gracilis, which grow in Asian coasts, was introduced into the Mediterranean Sea 3 , and established in the lagoons 4-7. Consequently, the alga was found all year round, but is the most component of the BL flora between April and June 4. In Tunisia, the quantity of seaweeds harvested, was restricted along the Bizerte Lagoon and the Tunis Lake, which is inadequate to supply the raw material requi...

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Section: Discussionmentioning

confidence: 91%

Effect of Lagoon and Sea Water Depth on Gracilaria gracilis Growth and Biochemical Composition in the Northeast of Tunisia

Mensi

Nasraoui

Bouguerra³

et al. 2020

Sci Rep

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“…Red tides in the Seto Inland Sea became less extensive and severe and phytoplankton biomass declined on broader scales. In the Suo Nada, the westernmost portion of the Seto Inland Sea between Honshu and Kyushu, chlorophyll a levels declined substantially, particularly in shallow waters, between 1984 and 2004, closely following reductions in loads of phosphorus and nitrogen (Nishijima et al, 2016). The introduction of advanced treatment for some wastewater discharges has also yielded reductions in nutrient concentrations and chlorophyll a in Tokyo Bay (Kubo et al, 2019).…”

Section: Asiamentioning

confidence: 99%

Barriers and Bridges in Abating Coastal Eutrophication

Boesch

2019

Front. Mar. Sci.

127

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Over the past 30 years concerted campaigns have been undertaken to reverse nutrient-driven eutrophication in coastal waters in Europe, North America, Asia, and Australia. Typically, eutrophication abatement has proven a more recalcitrant challenge than anticipated, with ecosystem improvements only recently beginning to emerge or falling short of goals. Reduction in nutrient loads has come mainly from advanced treatment of wastewaters and has lagged targets set for diffuse agricultural sources. Synthesis of the major campaigns-varying in terms of physical settings, ecosystem characteristics, nutrient sources, socio-economic drivers, and governance-identified barriers inhibiting eutrophication abatement and potential bridges to overcome them. Actionable science can be advanced by: application of the well-established and emerging knowledge and experience around the globe, client-responsive strategic research, and timely and conclusive adjudication of scientific controversies. More accountable governance requires: enduring engagement of high-level officials of the responsible governments; effective communication of the causes, risks and benefits to the public and stakeholders; quantitative and accountable allocation of responsibility for nutrient load reductions; and binding requirements, as opposed to simply voluntary actions. Effective reduction in nutrient loads requires: reduction strategies for both nitrogen and phosphorus; inclusion of actions that reduce atmospheric emissions of nitrogen in addition to direct inputs to waterways; efficacious regulations; public subsidies based on performance; limitations on biofuel production that increases nutrient loads; and enhancing the sinks and losses for legacy nutrients retained in soils and groundwater. Outcomes must be measured and strategies appropriately adjusted through: sustained monitoring of essential indicators and processes, the use of multiple models, truly adaptive management, and cautious interventions within the coastal ecosystem. The changing climate must be taken into account by reassessing achievable future conditions and seeking alternatives for mitigating and adapting to climate change that also reduce nutrient loads.

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“…The variation in phytoplankton community structure may occur in response to the environmental variables [14]. Nishijima et al [15] explored the Chl-a changes at different Secchi depths in the different time and space scales and found that the lack of nutrients, especially phosphorus, limited the increase in phytoplankton biomass. Hao et al [16] suggested that the thermal water discharged from the two power stations was a driver of the ecosystem's change in Daya Bay.…”

Section: Introductionmentioning

confidence: 99%

Temporal-Spatial Distribution of Chlorophyll-a and Impacts of Environmental Factors in the Bohai Sea and Yellow Sea

Zhao

Zhang

et al. 2019

IEEE Access

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Better understanding of the temporal-spatial distribution of chlorophyll-a concentration (Chl-a) is crucial in controlling harmful water blooms. In this study, the dynamical change of Chl-a over the Bohai Sea and Yellow Sea from 2003-2017 were analyzed by using the MODIS/Aqua satellite data, and the effects of sea surface temperature (SST), wind and wave were investigated. The typical distribution modes of long-term surface Chl-a were extracted by using the Self-organizing Mapping (SOM), neural network model. The results showed distinct seasonal variations of the Chl-a along with a gradual increase in the study period. The total Chl-a of the whole area reached the lowest value of 2.41mg/m 3 in July, and the highest value 3.43mg/m 3 in April; though in Laizhou Bay, the Chl-a concentration was significantly higher than other regions and the value reached at the peak in September. The spatial distribution showed that Chl-a decreased from inshore to offshore. Meanwhile, from clear mode to low, medium, and high concentration modes, the Chl-a gradually increased in coverage and concentration, and modes extracted by the SOM neural network have effectively elucidated the trend of Chl-a in spatial, seasonal, and interannual variability. The Generalized Additive Model (GAM) was used to evaluate the effect of SST, wind, and wave on the changing patterns of Chl-a. It was found that there is a significant nonlinear correlation between Chl-a and SST, wind speed, mean wave direction and significant height of the wave. These influencing factors accounted for 47.9% of the change of Chl-a, which had significant effects on Chl-a change. Compared with wind speed, mean wave direction and significant height of wave, SST can better explain the change of Chl-a. Besides, wind direction and increased human activity (e.g., river discharge) played a significant role in changing the Chl-a distribution in the Bohai Sea and Yellow Sea. INDEX TERMS Chl-a, self-organizing mapping neural network, generalized additive model, environmental factors, the Bohai sea and Yellow sea.

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Spatial and temporal distributions of Secchi depths and chlorophyll a concentrations in the Suo Nada of the Seto Inland Sea, Japan, exposed to anthropogenic nutrient loading

Cited by 21 publications

References 13 publications

Effect of Lagoon and Sea Water Depth on Gracilaria gracilis Growth and Biochemical Composition in the Northeast of Tunisia

Effect of Lagoon and Sea Water Depth on Gracilaria gracilis Growth and Biochemical Composition in the Northeast of Tunisia

Barriers and Bridges in Abating Coastal Eutrophication

Temporal-Spatial Distribution of Chlorophyll-a and Impacts of Environmental Factors in the Bohai Sea and Yellow Sea

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