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Persistent eutrophication and hypoxia in the coastal ocean
- Minhan Dai, Yangyang Zhao, Fei Chai, Mingru Chen, Nengwang Chen, Yimin Chen, Danyang Cheng, Jianping Gan, Dabo Guan, Yuanyuan Hong, Jialu Huang, Yanting Lee, Kenneth Mei Yee Leung, Phaik Eem Lim, Senjie Lin, Xin Lin, Xin Liu, Zhiqiang Liu, Ya-Wei Luo, Feifei Meng, Chalermrat Sangmanee, Yuan Shen, Khanittha Uthaipan, Wan Izatul Asma Wan Talaat, Xianhui Sean Wan, Cong Wang, Dazhi Wang, Guizhi Wang, Shanlin Wang, Yanmin Wang, Yuntao Wang, Zhe Wang, Zhixuan Wang, Yanping Xu, Jin-Yu Terence Yang, Yan Yang, Moriaki Yasuhara, Dan Yu, Jianmin Yu, Liuqian Yu, Zengkai Zhang, Zhouling Zhang
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- Journal:
- Cambridge Prisms: Coastal Futures / Volume 1 / 2023
- Published online by Cambridge University Press:
- 23 February 2023, e19
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- Article
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Coastal eutrophication and hypoxia remain a persistent environmental crisis despite the great efforts to reduce nutrient loading and mitigate associated environmental damages. Symptoms of this crisis have appeared to spread rapidly, reaching developing countries in Asia with emergences in Southern America and Africa. The pace of changes and the underlying drivers remain not so clear. To address the gap, we review the up-to-date status and mechanisms of eutrophication and hypoxia in global coastal oceans, upon which we examine the trajectories of changes over the 40 years or longer in six model coastal systems with varying socio-economic development statuses and different levels and histories of eutrophication. Although these coastal systems share common features of eutrophication, site-specific characteristics are also substantial, depending on the regional environmental setting and level of social-economic development along with policy implementation and management. Nevertheless, ecosystem recovery generally needs greater reduction in pressures compared to that initiated degradation and becomes less feasible to achieve past norms with a longer time anthropogenic pressures on the ecosystems. While the qualitative causality between drivers and consequences is well established, quantitative attribution of these drivers to eutrophication and hypoxia remains difficult especially when we consider the social economic drivers because the changes in coastal ecosystems are subject to multiple influences and the cause–effect relationship is often non-linear. Such relationships are further complicated by climate changes that have been accelerating over the past few decades. The knowledge gaps that limit our quantitative and mechanistic understanding of the human-coastal ocean nexus are identified, which is essential for science-based policy making. Recognizing lessons from past management practices, we advocate for a better, more efficient indexing system of coastal eutrophication and an advanced regional earth system modeling framework with optimal modules of human dimensions to facilitate the development and evaluation of effective policy and restoration actions.
Feeding ecology of three sympatric species of stingrays on a tropical mudflat
- Kean Chong Lim, Ving Ching Chong, Phaik-Eem Lim, Tatsuya Yurimoto, Kar Hoe Loh
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- Journal:
- Journal of the Marine Biological Association of the United Kingdom / Volume 99 / Issue 4 / June 2019
- Published online by Cambridge University Press:
- 02 October 2018, pp. 999-1007
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Periodic fish ingressions into intertidal areas during high tide are known to occur on tropical mudflats. This study aimed to elucidate the feeding ground function of coastal mudflats for three common stingray species in the Klang Strait, Malaysia. Stingrays (disc width range from 5.65–54.50 cm) sampled over 17 months using a large barrier net (~2 ha enclosure) at two sampling sites were examined for their diet composition, prey frequency and prey volume according to predator species and maturity. The index of relative importance and Schoener's index of diet overlap were calculated. The three stingray species fed on relatively similar prey items which varied in size and contribution. Brevitrygon heterura fed on the widest range of prey taxa (28) whereas Hemitrygon bennetti (22) and Telatrygon biasa (17) showed higher prey specialization. The Penaeidae (dominantly Metapenaeus brevicornis and M. affinis) were the most important food item in the stingray diet which also included Actinopterygii, Amphipoda, Brachyura and Calanoida. The stingray diet showed an ontogenetic shift, with young stingrays tending to be generalists whereas the more mature stingrays (except H. bennetti) become more specialized in their feeding habits. This shift in feeding strategy reflects the diversity of prey taxa abundantly available to young stingrays on the mudflats, while the larger stingrays adapt to feed on larger prey once they enter deeper waters.