East China Sea Ecosystem Research Articles

Climate change alters social-ecological trade-offs in achieving ocean futures' targets.

The effects of climate change on marine ecosystems are causing cascading impacts on livelihood, food security, and culture through fisheries. Such impacts interact and exacerbate the effects of overfishing on marine social-ecological systems, complicating the rebuilding of ecosystems to achieve desirable and sustainable ocean futures. Developing effective pathways for ecosystem rebuilding requires consideration of the co-benefits and trade-offs between ecological and social dimensions and between fishing sectors. However, the effects of intensifying climate change on such co-benefits or trade-offs are yet to be well understood, particularly in regions where ecosystem rebuilding is urgently needed. We applied a numerical optimization routine to define the scope for improvement toward the Pareto-frontier for ecological robustness and economic benefits of the northern South China Sea (NSCS) and the East China Sea (ECS) ecosystems. These two ecosystems were used to represent over-exploited low- and mid-latitude systems, respectively, and the optimization aimed to improve their status through fisheries management. We find that the ECS ecosystem has the possibility of increasing the economic benefits generated by the fisheries it supports under climate change by 2050 while increasing the uncertainty of achieving biodiversity objectives. Nevertheless, climate change is projected to reduce the scope to restore ecosystem structures and the potential economic benefits in the NSCS ecosystem. This study highlights the contrasting impacts of climate change on the co-benefits/trade-offs in ecosystem rebuilding and the benefits obtainable by different fishing sectors even in neighboring ecosystems. We conclude that consideration at the nexus of climate-biodiversity-fisheries is a key to developing effective ecosystem rebuilding plan.

Seasonal-Spatial Distribution Variations and Predictions of Loliolus beka and Loliolus uyii in the East China Sea Region: Implications from Climate Change Scenarios.

Global climate change profoundly impacts the East China Sea ecosystem and poses a major challenge to fishery management in this region. In addition, closely related species with low catches are often not distinguished in fishery production and relevant data are commonly merged in statistics and fishing logbooks, making it challenging to accurately predict their habitat distribution range. Here, merged fisheries-independent data of the closely related squid Loliolus beka (Sasaki, 1929) and Loliolus uyii (Wakiya and Ishikawa, 1921) were used to explore the construction and prediction performance of species distribution models. Data in 2018 to 2019 from the southern Yellow and East China Seas were used to identify the seasonal-spatial distribution characteristics of both species, revealing a boundary line at 29.00° N for L. uyii during the autumn, with the highest average individual weight occurring during the summer, with both larvae and juveniles occurring during the autumn. Thus, the life history of L. uyii can be divided into winter-spring nursery and summer-autumn spawning periods. L. beka showed a preference for inshore areas (15-60 m) during the summer and offshore areas (32.00-78.00 m) during the winter. High-value areas of both species included inshore areas of the southern Yellow and mid-East China Seas during the autumn, enlarging during the spring to include central areas of the survey region, before significantly decreasing during the summer. Therefore, this study provides both a novel perspective for modeling biological habitat distribution with limited data and a scientific basis for the adjustment of fishery resource management and conservation measures in the context of climate change.

Larval Spatiotemporal Distribution of Six Fish Species: Implications for Sustainable Fisheries Management in the East China Sea

The larval distributions of the small-sized fishes Omobranchus elegans, Erisphex pottii, Benthosema pterotum, Acropoma japonicum, Upeneus bensasi, and Apogonichthys lineatus in the East China Sea ecosystem are important due to their ecological and economic benefits. To date, however, there have been few studies describing their population distributions and dynamics. In the current study, ichthyoplankton surveys were carried out from April to July 2018 to analyze variations in the larval abundance, distribution, and development stages of these species. In addition, the spatiotemporal larval distribution was investigated in terms of measured environmental variables. It was found that larvae were mainly distributed at depths of 5.00–66.00 m, in areas with sea surface temperature of 4.40–29.60 °C, sea surface salinity of 16.54–34.60 psu, pH of 7.00–9.00, and dissolved oxygen concentration of 2.54–8.70 mg/L. Benthosema pterotum and A. lineatus migrated from 30.00–31.00° N 123.17–123.50° E in June to 30.00–32.50° N 122.22–123.50° E in July. The results of this study can help to preserve spawning and nursery grounds and contribute to sustainable coastal fisheries management.

Contaminant occurrence, spatiotemporal variation, and ecological risk of organophosphorus flame retardants (OPFRs) in Hangzhou Bay and east China sea ecosystem.

Occurrence, spatiotemporal variation, sources, and ecological risks of 20 organophosphorus flame retardants (OPFRs) in water and sediments from Hangzhou Bay (HZB) and its adjacent East China Sea (ECS) were investigated in this study. The concentrations of OPFRs (∑OPFR) in water ranged from 0.51ng/L to 885ng/L, with chlorinated OPFRs having the highest value. For sediments, ∑OPFR ranged from 2.93ng/g, dry weight (dw) to 37.8ng/g, dw. The ∑OPFR in the water and sediments of HZB in summer was significantly (p<0.05) higher than that in autumn. Additionally, the pollution of OPFRs in HZB was higher than that in ECS, and the high-concentration areas appeared in the north and south banks of HZB and near the coast of ECS. Principal component analysis-multiple linear regression showed that the OPFRs in this region were mainly from industrial products (e.g., polyurethane foam/paint/coating/textiles/product processing). In terms of aquatic environments, ecological risks were in a low (∑RQs<0.1) to moderate (0.1<∑RQs<1) level, with regard to median exposure levels, a moderate risk (0.1<∑RQs<1) was found in the sediments during autumn. This study can provide new insights into the OPFR pollution characteristic and ecological risk in a specific eco-environment.

Estimating the Impact of a Seasonal Fishing Moratorium on the East China Sea Ecosystem From 1997 to 2018

Fisheries management policies (FMPs) have been implemented in coastal countries to ensure a sustainable supply of seafood and the recovery of species diversity. Because of the depletion of fishery stocks, China has introduced a series of FMPs since 1995, including a seasonal fishing moratorium (SFM), a zero-growth strategy, and a minimum mesh size for fishing nets. Here, we built two mass balance models for 1997–2000 (M1997) and 2018–2019 (M2018) using Ecopath with Ecosim 6.6 to illustrate the interannual changes over the past two decades in the East China Sea (ECS). We then simulated two dynamic scenarios from 1997 to 2018, SFM (M2018SFM) and no SFM (M2018no-SFM), to test the role of the SFM under fishing pressure in the ECS. Ecopath showed that the ECS ecosystem is becoming more mature, although it is still unstable, featuring lower total primary production/total respiration, longer cycles, faster organic material circulation speed, and a higher omnivorous degree. This suggests a slow recovery for the ECS ecosystem in the past two decades. The biomass of fish in the ECS—especially the planktivores, dominated by small-sized Benthosema pterotum—significantly increased in M2018 versus M1997, but there were fewer medium- and large-sized fish. The keystone species switched from the planktivores/piscivores dominated by Decapterus maruadsi in M1997 to planktivores in M2018. Ecosim illustrated that the SFM has positive effects on fishery resources recovery, especially for commercial fishes (i.e., large yellow croakers and hairtails), as reflected by the significantly higher predicted biomass of fish in M2018SFM compared to M2018no-SFM and M1997, although the bioaccumulation was consumed by the intense fishing pressure after the SFM. However, the M2018SFM prediction for nektons was still lower than the actual value, especially for planktivores, which display a sharp increase in biomass. This should be partly attributable to the policy of the minimum mesh size (&amp;lt;5 cm was banned), which benefits B. pterotum due to its 3.5 cm maximum body size. Therefore, a series of FMPs, rather than only the SFM, functioned together in the ECS ecosystem. However, the mixed trophic impact indicated a negative impact if the fisheries were further developed. Fishery management in the ECS needs to be strengthened by extending the SFM and reducing fishing pressure after the SFM.

East China Sea ecosystem under multiple stressors: Heterogeneous responses in the sea surface chlorophyll-a

The East China Sea and southern Yellow Sea ecosystems have undergone drastic changes over the past decades. The changes in the ecosystems are attributable to both natural and anthropogenic stressors. We analyzed the seasonal and interannual variability of the sea surface chlorophyll-a in the East China Sea and the southern Yellow Sea using a suite of remotely sensed data (1998–2012). When seen on a Large Marine Ecosystem level, there seems no trend in the region. However, when seen on a sub-regional scale, heterogeneous responses can be recognized among the subregions. There was an increasing trend of chlorophyll-a in the vicinity of the Changjiang (Yangtze) River mouth, while there was a decreasing trend in the southeastern slope area which can be attributed to anthropogenic nutrient enrichment and warming, respectively. Contrary to some previous studies, our analysis clearly showed that the summer-autumn averaged chlorophyll-a decreased by about 14% in a large area (circa 178,000 km2) in the northeastern East China Sea after 2003 coinciding with the initial impoundment of the Three Gorges Dam. Our analysis demonstrates that our ability to detect the trends in response to multiple stressors largely depends on choosing an appropriate spatiotemporal scale.

Stable carbon isotopic analysis of amino acids in a simplified food chain consisting of the green algaChlorellaspp., the calanoid copepodCalanus sinicus, and the Japanese anchovy (Engraulisjaponicus)

Japanese anchovy (Engraulis japonicus Temminck and Schlegel, 1846) is a keystone species in the food web of the Yellow Sea and East China Sea ecosystem. To study nutrient flow at intermediate and lower trophic levels, a controlled feeding experiment was carried out on a simplified food chain of the green alga Chlorella Beijerinck, 1890 – the calanoid copepod Calanus sinicus Brodsky, 1962 – E. japonicus. For the whole organism, bulk δ13C was found to be enriched with escalating trophic level, although the intertrophic gap in δ13C was slightly lower than the commonly reported 1.5‰ per increase in level. Furthermore, 15 amino acids (AAs) were detected in the studied organisms. Among them, the δ13C values of 12 AAs were determined and were found to exhibit diverse patterns of variation. The δ13C levels of essential AAs changed very little and were highly correlated across trophic levels, indicating that they underwent little trophic fractionation and were mainly ingested by the consumers from the proteins in their food. In contrast, the δ13C values of nonessential AAs differed greatly across trophic levels, indicating that the nonessential AAs in consumers were synthesized de novo from food proteins. The fractionation pattern of nonessential AAs may depend on the carbon pool and the AA composition of the organism at the lower trophic level.

The impacts of fishing and nutrient influx from Yangtze River on the ecosystem in East China Sea

As the main nutrient inputs of East China Sea (ECS), nutrient concentrations of the Yangtze River increase significantly due to high-speed economy development, which play a very important impact on the East China Sea ecosystem. In this study, by integrating MEC and EwE model, we analyzed the impact of Yangtze nutrient fluxes change and fishery on the ecosystem of ECS from 1960 to 2000. Our research shows that under high fishing pressure, the main fish production decrease significantly, average trophic level recession and small fish take the main position of ecosystem. But the increasing nutrition influxes from Yangtze River have a certain influence for the ecosystem to slow the decline tendency of fish because it can stimulate the plankton growth. This research provides a method to study the entire ecosystem from the prospective of both environmental and fishery factors, extending from physical conditions to higher ecosystem, to achieve a top–down and bottom–up management.

Compound-specific isotopes of fatty acids as indicators of trophic interactions in the East China Sea ecosystem

The composition and compound-specific isotopes of fatty acids were studied within food webs in the East China Sea. Lipid-normalized stable carbon isotopes of total organic carbon had a good correlation with trophic level. Variations in fatty acid compositions among diff erent species were observed but were unclear. Diff erent dietary structures could be traced from molecular isotopes of selected fatty acids in the Shiba shrimp (Matapenaeus joyneri), the coastal mud shrimp (Solenocera crassicornis) and the northern Maoxia shrimp (Acetes chinensis). Both M. joyneri and S. crassicornis are mainly benthos feeders, while A. chinensis is a pelagic species, although they have a similar fatty acid composition. There was a good correlation for isotopes of arachidonic acid (C20:4n6; ARA) and docosahexaenoic acid (C22:6n3; DHA) among pelagic species from higher trophic levels. The isotopic compositions of DHA in benthic species were more negative than those of pelagic species at the same trophic level. The fact that the diet of benthic species contains more degraded items, the carbon isotopes of which are derived from a large biochemical fraction, may be the reason for this variation. A comparative study of benthic and pelagic species demonstrated the diff erent carbon sources in potential food items and the presence of a more complex system at the water-sediment interface.

Diversity of demersal fish in the East China Sea: Implication of eutrophication and fishery

The environment of the East China Sea has been greatly impacted by both fishing and land-based pollution over the past decades, with a concomitant decline of fishery resources. Imposition of a seasonal fishing moratorium and a trawling prohibition zone has failed to engender recovery of fish communities. To help understand the respective impacts of environmental factors and fishing activities in the East China Sea ecosystem, fish samples and environmental parameters were collected in prohibited and open fishing areas, during the seasonal fishing moratorium. The inshore area of the East China Sea, corresponding to the prohibited zone for trawling, had extremely high nutrient concentrations and relatively low dissolved oxygen. The diversity index of demersal fish showed significantly negative correlations with nutrient concentrations and positive correlations with bottom-water dissolved oxygen. The inshore area of the East China Sea was heavily dominated by small-sized fishes, such as Gobiids—Amblychaeturichthys hexanema and Apogonids—Apogon lineatus, reflecting low survival of most fish species. In contrast, the offshore areas, with lower nutrient concentrations and higher dissolved oxygen, had higher biodiversity. These findings suggest that eutrophication and subsequent hypoxia is responsible for the limited recovery of fishery resources in the trawling prohibition area of the East China Sea. Therefore, a multi-pronged fishery management that involves both fishing restriction and environmental improvement is urgently needed in the East China Sea.

“China GLOBEC II: A case study of the Yellow Sea and East China Sea ecosystem dynamics”

“China GLOBEC II: A case study of the Yellow Sea and East China Sea ecosystem dynamics”

How polluted is the Yangtze river? Water quality downstream from the Three Gorges Dam

The concentrations of major anions and cations, nitrogen and phosphorus, dissolved and particulate trace elements, and organic pollutants were determined for the middle and lower reaches of the Yangtze River (Changjiang) from below the Three Gorges Dam (TGD) to the mouth at Shanghai in November 2006. The concentration of dissolved inorganic phosphate (DIP) was constant at a low level of 6–8 µgP/L, but the concentration of nitrate (NO 3 −) approximately doubled downstream and was closely correlated with K +. This translated to a daily load of well over 1000 t of dissolved inorganic nitrogen (DIN) at Datong. The average concentrations of dissolved Pb (0.078 ± 0.023 µg/L), Cd (0.024 ± 0.009 µg/L), Cr (0.57 ± 0.09 µg/L), Cu (1.9 ± 0.7 µg/L), and Ni (0.50 ± 0.49 µg/L) were comparable with those in other major world rivers, while As (3.3 ± 1.3 µg/L) and Zn (1.5 ± 0.6 µg/L) were higher by factors of 5.5 and 2.5, respectively. The trace element contents of suspended particles of As (31 ± 28 µg/g), Pb (83 ± 34 µg/g), and Ni (52 ± 16 µg/g) were close to maximum concentrations recommended for rivers by the European Community (EC). The average concentrations of Cd (2.6 ± 1.6 µg/g), Cr (185 ± 102 µg/g), Cu (115 ± 106 µg/g), and Zn (500 ± 300 µg/g) exceeded the EC standards by a factor of two, and Hg (4.4 ± 4.7 µg/g) by a factor of 4 to 5. Locally occurring peak concentrations exceed these values up to fourfold, among them the notorious elements As, Hg, and Tl. All dissolved and particulate trace element concentrations were higher than estimates made twenty years ago [Zhang, J., Geochemistry of trace metals from Chinese river/estuary systems: an overview. Estuar Coast Shelf Sci 1995; 41: 631–658.]. The enormous loads of anthropogenic pollutants disposed to the river were diluted by the large water discharge of the Yangtze even during the lowest flow resulting in the relatively low concentration levels of trace elements and organic pollutants observed. We estimated loads of e.g. As, Pb and Ni to the East China Sea to be about 4600 kg As d − 1 , 3000 kg Pb d − 1 , and 2000 kg Ni d − 1 . About 6000 t d − 1 of dissolved organic carbon (DOC) was delivered into the sea at the time of our cruise. We tested for 236 organic pollutants, and only the most infamous were found to be barely above detection limits. We estimated that the load of chlorinated compounds, aromatic hydrocarbons, phenols, and PAHs were between 500 and 3500 kg d − 1 . We also detected eight herbicides entering the estuary with loads of 5–350 kg d − 1 . The pollutant load, even when at low concentrations, are considerable and pose an increasing threat to the health of the East China Sea ecosystem.

한국 연근해 생태계의 잠재 재생산 지수

We developed an ecosystem indicator (EI) for the coastal and offshore areas of Korean waters. One of the major scientific challenges of this undertaking was to translate broad policy statements for ecosystem-based fisheries management (EBFM) into practical terms. Fish reproduction potential (FRP) was defined as an EI to describe the reproductive probability of adult fisheries resources in Korean waters. The FRP was estimated as the ratio of adult fish composition to total catch, catches (in metric tons) by species and by ecosystem, and fishery effort (in horse power per metric ton). The FRP indices of the East/japan Sea Ecosystem (EJSE), Yellow Sea Ecosystem (YSE), and East China Sea Ecosystem (ECSE) began to decrease after the mid-1980s, and the current indices have decreased further, at 0.63 (EJSE), 1.22 (YSE), and 0.68 (ECSE) index points compared to the indices of 1975, when similar catch amounts were recorded. Lower FRPs in the Korean marine ecosystems were the result of higher proportion of immature fisheries resources in the total catch. Because this kind of ecosystem-level indicator is thought to reflect scientific approaches to EBFM and to provide an important tool for assessing the current status of marine ecosystems with respect to both quantity and quality, more EIs should be developed for Korean waters.

Reduction of primary production and changing of nutrient ratio in the East China Sea: Effect of the Three Gorges Dam?

It has been documented that the global proliferation of dam construction on the major river has reduced nutrient and sediment loading to coastal environments. As a consequence, dams can impact marine ecological systems by changing nutrient concentrations and ratios in the coastal zone. From 1998–2004, we conducted a high resolution oceanographic investigation of the East China Sea (ECS) before and after the first filling phase (June 2003) of the Three‐Gorges Dam (TGD). We found that the Si:N ratio in the River affected region changed from 1.5 in 1998 to 0.4 in 2004 with sediment loading significantly reducing (about 55%) at the Datong station after June 2003. Most importantly, we found that the PP had declined by 86% between 1998 and 2003, both measured during the high flood season. The results suggest that the ECS ecosystem may respond sensitively to changes in the nutrient supply arising from the TGD project.

Establishment of trophic continuum in the food web of the Yellow Sea and East China Sea ecosystem: Insight from carbon and nitrogen stable isotopes

Stable carbon and nitrogen isotope ratios (delta (13)C and delta (15)N) are used to study the trophic structure of food web in the Yellow Sea and East China Sea ecosystem. The trophic continuum of pelagic food web from phytoplankton to top preyer was elementarily established, and a trophic structure diagram in the Yellow Sea and East China Sea was outlined in combination with carbon isotopic data of benthic organisms, which is basically consistent with and makes some improvements on the simplified Yellow Sea food web and the trophic structure diagram drawn based on the biomass of main resource population during 1985-1986. This result indicates that the stable isotope method is a potential useful means for further studying the complete marine food web trophic continuum from viruses to top predators and food web stability.

Geomorphology of the Davis Sea bottom : Beresnov A.F., 1962. Mezhd. Geofiz. Komitet, Prezidiume Akad. Nauk SSSR, Rezult. Issled. Programme Mezhd. Geofiz. Goda Okeanol. Issled., 5: 43–59

The environment of the East China Sea has been greatly impacted by both fishing and land-based pollution over the past decades, with a concomitant decline of fishery resources. Imposition of a seasonal fishing moratorium and a trawling prohibition zone has failed to engender recovery of fish communities. To help understand the respective impacts of environmental factors and fishing activities in the East China Sea ecosystem, fish samples and environmental parameters were collected in prohibited and open fishing areas, during the seasonal fishing moratorium. The inshore area of the East China Sea, corresponding to the prohibited zone for trawling, had extremely high nutrient concentrations and relatively low dissolved oxygen. The diversity index of demersal fish showed significantly negative correlations with nutrient concentrations and positive correlations with bottom-water dissolved oxygen. The inshore area of the East China Sea was heavily dominated by small-sized fishes, such as Gobiids—Amblychaeturichthys hexanema and Apogonids—Apogon lineatus, reflecting low survival of most fish species. In contrast, the offshore areas, with lower nutrient concentrations and higher dissolved oxygen, had higher biodiversity. These findings suggest that eutrophication and subsequent hypoxia is responsible for the limited recovery of fishery resources in the trawling prohibition area of the East China Sea. Therefore, a multi-pronged fishery management that involves both fishing restriction and environmental improvement is urgently needed in the East China Sea.