Response of phytoplankton communities to environmental changes in the Bohai Sea in late summer (2011−2020)

Understanding the dynamics of phytoplankton communities in coastal zones is crucial for the management and conservation of coastal ecosystems.Previous research indicated that the phytoplankton community structure and dominant taxa in the Bohai Sea(BHS)have exhibited significant shifts from the 1990s to the early 2010s in response to environmental changes,especially the change in nutrient structure.This study comprehensively investigated the variations in net-collected phytoplankton(>76μm)community structure,diversity,and environmental factors in the BHS during the late summers of 2011-2020,aiming to understand the recent trend in phytoplankton community structure and to explore the interactions between the communities and the environment.During the study period,the nutrient status in the BHS was characterized by a decrease in dissolved inorganic nitrogen(DIN)concentration,an increase in dissolved inorganic phosphorus(DIP)concentration,and a return of the nitrogen-to-phosphorus(N/P)molar ratio(hereinafter referred to as N/P ratio)to the Redfield ratio since 2016.The eutrophication index(EI)in the BHS remained stable and was generally at a low level(<1).The Dia/Dino index fluctuated but did not show an obvious trend.Overall,the eutrophication,the imbalance in nutrient ratio,and the shift in phytoplankton community structure did not continue during the study period.The increased abundance of phytoplankton was strongly associated with elevated concentrations of DIN,as well as higher N/P and nitrogen-to-silicon(N/Si)ratios,whereas the greater diversity was strongly linked to higher concentrations of DIP.Diatoms and dinoflagellates showed significant differences in their interactions with the environment,and their relative dominance was related to water column depth and stratification intensity;their impacts on the phytoplankton community diversity were also significantly different.The variations of certain dominant species,i.e.,Skeletonema costatum,Paralia sulcata,and Tripos longipes,exhibited strong links to the changes in nutrient structure in the BHS.The findings of this study contribute to understanding the regional environmental changes and provide insights into the adaptive strategies of coastal ecosystems in response to environmental shifts and fluctuations.

Paleoenvironmental changes recorded by grain size of loess/paleosol sequence from the Chifeng City,Northeastern China since the Last Glacial

The accumulation processes of loess in northeastern(NE)China record the varying characteristics of the East Asian Monsoons(EAM)and the evolution of the local environment.In this study,grain size end-member analysis of the Dajiugang(DJG)section deposited since the Last Glacial in Chifeng City,NE China was used to reveal the dynamic depositional characteristics of loess and environmental evolution of NE China.Results showed that the Chifeng loess comprises three grain size end-members(EM),EM1(7.38μm),EM2(49.4μm)and EM3(90.00μm),indicating the three transport dynamics of dust delivered to the region.The EM1 represents atmospheric dust as the background.The EM2,mainly derived from relatively distant-sources deposition,and EM3,material transported over a short distance,correspond to the intensity of southwesterly winds and the East Asian Winter Monsoon(EAWM),respectively.Results of climate reconstruction,combined with other records,showed that the climate was generally cold and dry with a strong EAWM and a weak East Asian summer monsoon(EASM)during the stadial-period[Marine Isotope Stage(MIS)4 and MIS 2 stage].The climate was predominantly warm and humid,with weak EAWM and surface winds and strong EASM in interstadial-period(MIS 3 and MIS 1 stage).Comparisons between indicators,e.g.,EM3,the LR04 benthicδ18O stack and summer insolation at 65°N suggest that the strong EAWM is induced by increasing the Northern Hemisphere ice volume and reduced summer solar radiation.

Environmental Changes Analysis of Hongjiannao Lake During Recent Fifty Years——Based on the Data of Lake Sediments

Particle size, the contents of carbonate and TOC were analyzed on lake sediments from a short core in Hongjiannao Lake to discuss the environmental changes during the past decades. On the basis of the records in lake sediments and comparison with the meteorological data of Yulin region, the environmental changes in Hongjiannao Lake were approximately divided into two stages. In stage A （1957 -1996）, the lake evolution and the environmental change were mainly influenced by natural factors. It contains three sub-stages： A1 （1957-1969）, a period of lake expansion, A2 （1969-1990）, a stable period with high lake levels, and A3 （1990 -1996）, a period of gradual extraction of the lake. In stage B （1996 -2005）, the lake area still keeps diminishing. During this period, organic matter increased rapidly due to the input of nutrient elements in the catchment. The carbonate content, however, decreased. As the precipitation was decreasing and the temperature was increasing, the decrease of carbonate content could not be explained by either temperature or precipitation change.

Soil Organic Carbon and Labile Carbon Along a Precipitation Gradient and Their Responses to Some Environmental Changes

Based on data from a field survey in 2001 along the Northeast China transect (NECT), a precipitation gradient,and a short-term simulation experiment under ambient CO2 of 350 μmol mol-1 and doubled CO2 of 700 μmol mol-1with different soil moisture contents of 30%-45%, 45%-60%, and 60%-80% soil water holding capacity, the distributionof soil organic carbon and labile carbon along the NECT, their relationships with precipitation and their responses toCO2 enrichment and soil moisture changes were analyzed. The results indicated that the soil labile carbon along thegradient was significantly related to soil organic carbon (r = 0.993, P < 0.001). The soil labile carbon decreased morerapidly with depth than organic carbon. The soil organic and labile carbon along the gradient decreased with decrease inlongitude in both the topsoils and subsoils, and the coefficient of variation for the labile carbon was greater than that forthe organic carbon. Both the soil organic carbon and labile carbon had significant linear relationships with precipitation,with the correlation coefficient of soil organic carbon being lower (0.677 at P < 0.001) than that of soil labile carbon(0.712 at P < 0.001). In the simulation experiment with doubled and ambient CO2 and different moisture contents, thecoefficient of variation for soil organic carbon was only 1.3%, while for soil labile carbon it was 29.7%. With doubled CO2concentration (700 μmol mol-1), soil labile carbon decreased significantly at 45% to 60% of soil moisture content. Theseindicated that soil labile carbon was relatively more sensitive to environmental changes than soil organic carbon.

Paleoenvironmental changes during the late Quaternary as inferred from foraminifera assemblages in the Laizhou Bay

Controlled by climate changes, there were three large-scale transgressions and regressions around the Bohai Sea during the late Quaternary, which were accepted by most geologists. However, a big controversy still exists about the time when the transgressions occurred separately. In order to find out the process of the paleoenvironmental changes around the Bohai Sea in the late Quaternary, the foraminifera assemblages from a new borehole Lz908 in the southern coast of the Laizhou Bay were studied, and then the transgressive strata were indentified. Combined with accelerator mass spectrometry radiocarbon 14C（AMS14C） and optically stimulated luminescence（OSL） ages, the occurrence time of these transgressions were re-determined. The result showed that three major large-scale transgressions occurred separately at the beginning of marine isotopic stage 7（MIS7）, the last interglacial period（MIS5） and the Holocene. In addition, a small-scale transgression occurred in the mid-MIS6, and the corresponding transgressive stratum was deposited. The transgressive deposition of MIS3 was also discovered in this study. However, the characteristics of the foraminifera indicated the environment during this period was colder than that in the MIS5. By comparison with the global sea-level changes, the paleoenvironmental changes around the Bohai Sea in the late Quaternary can be consistent with the global climate changes.

The sources and composition of organic matter in sediments of the Jiaozhou Bay：implications for environmental changes on a centennial time scale

The Jiaozhou Bay is characterized by heavy eutrophication that is associated with intensive anthropogenic activities. Four core sediments from the Jiaozhou Bay are analyzed using bulk technologies, including sedimentary total organic carbon（TOC）, total nitrogen（TN）, the stable carbon（δ13C） and nitrogen（δ15 N） isotopic composition to obtain the comprehensive understanding of the source and composition of sedimentary organic matter and further shed light on the environmental changes of the Jiaozhou Bay on a centennial time scale.Results suggest that the TOC and TN concentrations increase in the upper core, having indicated a probable eutrophication process since the 1920 s in the inner bay and the 2000 s in the bay mouth. The TOC and TN concentrations outside the bay have also changed since 1916 owing to the variation of terrigenous input.Considering TOC/TN ratio, δ13 C and δ15 N, it can be concluded there is a mixture of terrigenous and marine organic matter sources in the study area. A simple two end-member（terrigenous and marine） mixing model usingδ13 C indicats that 45%–79% of TOC in the Jiaozhou Bay is from the marine source. The environmental changes of the Jiaozhou Bay are recorded by geochemical proxies, which are influenced by the intensive anthropogenic activities（e.g., extensive use of fertilizers, and discharge of sewage） and climate changes（e.g., rainfall）.

Sediment records of environmental changes in the south end of the Zhejiang-Fujian coastal mud area during the past 100 years

Previous studies carried out in the East China Sea （ECS） mud area focused on long-term environmental changes in sedimentary records during the Holoeene, especially during the mid-Holocene high-stand water levels period. These results indicate that sensitive grain size groups can be used as a sedimentary proxy to reconstruct the evolution of the East Asian Winter Monsoon （EAWM）. The studies have been carried out mainly in the northern and middle portions of the Zhejiang-Fujian coastal mud, however, similar research in the southern portion and the comparison between sedimentary proxy and modern measured data of EAWM are lacking. In this paper, we focused on a sedimentary record of the past 100 years with an enhanced resolution of 1.8 years. Investigations of the southern end of the Zhejiang-Fujian coastal mud area were conducted on the basis of 21~Pb chronology, grain-size analysis and chemical element analysis. The correspondence between the mean grain size （Mz） of sediment sensitive grain size and the measured EAWM was confirmed for the first time. We found that during the recent 100 years, the variation of the mean grain size of the sensitive population in the southern portion of the Zhejiang-Fujian mud was mainly controlled by the EAWM intensity changes; and not directly related to changes in the sediment discharge from Datong station of the Changjiang River （DTSD）. Finally, recent changes in the content of heavy metals in study area reflect the impact of human activities on the environment.

Environmental changes during modern period from the record of Gaoyou Lake sediments, Jiangsu

Based on analysis of parameters of cores taken from Gaoyou Lake, including magnetic susceptibility, grain-size characteristics and sedimentary rate, environmental changes during the modern period were examined with the assistance of historical records and Gaoyou Lake water level materials. It is concluded that during the modern period a higher value of magnetic susceptibility and a lower sediment grain size coincided with a wet climate, while a lower value of magnetic susceptibility and a higher grain size were related with a dry climate. The results indicate that the climate in the 123 years period from 1880 to 2003AD can be divided into four stages： two low water level stages （1880-1915AD, 1948-1981AD） and two high water level stages （1915-1948AD, 1981-2003AD）. It appears that the regional climate generally underwent a dry-wet-dry-wet pattern in 30-year cycles. At present, it is at the end of a wet period, so the regional climate is expected to become dry in the near future. This conclusion corresponds with the climate records in the historical literature of the Gaoyou area, and it also matches with the climatic changes in North Jiangsu area.

Population growth，economic growth，technology changes in relation to environmental changes──A theoretical modelling analysis of environmental changes

This paper mainly deals with the impact of three major factors , namely population growth,economic growth and technology changes, on the changes of environmental quality. It presents a curve ofenvironmental changes in relation to demographic transition and process of industrialization. It concludesthat a major way of improving environmental quality is to intensify pollution decreasing technical factorsand that control of population growth will also reduce the pressure on the environment.

Responses of breeding waterbird communities to environmental changes in subsidence wetlands in the North China Plain

In the context of global degradation and loss of natural wetlands,waterbirds have been increasingly using artificial wetlands as alternative habitats.However,waterbirds are facing various threats in these artificial wetlands,due to dramatic environmental changes induced by anthropogenic activities.Exploring the effects of these changes on the temporal dynamics of the waterbird communities can help understand how waterbirds adapt to environmental changes and thus formulate effective management and conservation plans.In this study,we carried out field surveys on waterbirds and environmental factors across 20 subsidence wetlands created by underground coal mining in the Huainan coal mining area in the breeding seasons of 2016 and 2021.We predicted that the waterbird assemblages(i.e.,number of individuals,species richness,Shannon-Wiener diversity,Pielou evenness and species composition) differed between the two years,and that these differences were correlated with the temporal changes in environmental factors.Across the surveyed wetlands,we recorded 26 waterbird species in 2016 and 23 in 2021.For individual wetlands,the number of waterbird individuals and species richness increased by 71.6% and 20.1%,respectively,over the five years,with no changes in Shannon-Wiener diversity and Pielou evenness.The overall increase in the number of bird individuals was mainly caused by an increase in vegetation gleaners and gulls that adapt well to anthropogenic activities.The species composition was significantly different between the two years,which was mainly caused by changes in the number of individuals of dominant species under influence of changes in human activities.For most wetlands,the temporal pairwiseβ-diversities could be explained by species turnover rather than nestedness,probably due to high mobility of waterbird species and dramatic changes in local environments.Our study suggests that waterbird communities could respond to environmental changes in subsidence wetlands,providing important implications for waterbird conservation in human-dominated artificial wetlands.

Mountain evolution and environmental changes of Huangshan(Yellowmountain),China

Huangshan (Yellow Mountain) is located in southern part of the lower reaches of the Yangtze River. The highest Lotus Flower peak is 1864 m above sea level. Formative ages of the Huangshan and its granite,process of mountain geomorphic evolution from the Eocene to Quaternary,environmental changes of Quaternary, formative origin of beautiful peaks and fascinating rocks were studied and the questionable 'Pleistocene glaciation' was also discussed in this paper.

Attaching Importance to Post-9/11 Environmental Changes

Security environment is both an objective reality and a subjective consciousness. Here so-called "objective reality" mainly refers to the inherent law of the changes in international security situation. To a great extent, the subjective consciousness of the objective reality depends on the position and strategic choices of a nation in the international

Cave Environmental Changes： The Possibilities of Assessment

The aim of this research is to apply a new approach to assess cave environmental changes--CDI （cave disturbance index）, based on the five main categories： geomorphology, hydrology, atmosphere, biology and culture. The indicators of every category are considered in detail. The quantitative estimation of total CDI is proposed.

Reconstructing Environmental Changes of a Coastal Lagoon with Coral Reefs in Southeastern Hainan Island

Coastal lagoons with small catchment basins are highly sensitive to natural processes and anthropogenic activities. To figure out the environmental changes of a coastal lagoon and its contribution to carbon burial, two sediment cores were collected in Xincun Lagoon, southeastern Hainan Island and (210) ~Pb activities, grain size parameters, total organic carbon(TOC), total nitrogen(TN), total inorganic carbon(TIC) and stable carbon isotopes(δ^(13)C) were measured. The results show that in 1770–1815, the decreasing water exchange capacity with outer open water, probably caused by the shifting and narrowing of the tidal inlet, not only diminished the currents and fined the sediments in the lagoon, but also reduced the organic matter of marine sources. From 1815 to 1950, the sedimentary environment of Xincun Lagoon was frequently influenced by storm events. These extreme events resulted in the high fluctuation of sediment grain size and sorting, as well as the great variation in contributions of terrestrial(higher plants, soils) and marine sources(phytoplankton, algae, seagrass). The extremely high content of TIC, compared to TOC before 1950 could be attributed to the large-scale coverage of coral reefs. However, with the boost of seawater aquaculture activities after 1970, the health growth of coral species was severely threatened, and corresponding production and inorganic carbon burial flux reduced. The apparent enhanced inorganic carbon burial rate after 1990 might result from the concomitant carbonate debris produced by seawater aquaculture. This result is important for local government long-term coastal management and environmental planning.

20 000 years environmental changes of the Gonong Co in Hoh Xil of Qinghai

The Gonong Co is situated at 60 km west of the No. 84 Highway Maintenance Squadof the Qinghai-Xizang Highway (34°38’N, 92°09’E) with an elevation of 4670m. In Juneof 1990, a drill 725 cm deep was made on the lake beach with a distanee of 100m to thewater line (20cm high above lake level) by the Hoh Xil Integtated Scientific

Holocene environmental changes around Xiaohe Cemetery and its effects on human occupation, Xinjiang, China

The Xiaohe Cemetery archaeological site （Cal. 4-3.5 ka BP） is one of the most important Bronze Age sites in Xinjiang, China. Although the surrounding environment is an extremely arid desert now, abundant archaeological remains indicate that human occupation was common during certain periods in the Holocene. Field investigations and laboratory analyses of a sediment profile near the Xiaohe Cemetery indicate that while the regional environment was arid desert throughout the Holocene there were three episodes of lake forma- tion near the site in the periods 4.8-3.5 ka BP, 2.6-2.1 ka BP and 1.2-0.9 ka BP. Geomorphic and hydrological investigations reveal that a lake or lakes formed in a low-lying area when water was derived initially from the Kongque River and then shunted into the Xiaohe River basin. Low amounts of active chemical elements in lacustrine sediment between 4.8-3.5 ka BP indicate abundant and continuous water volume in the lake; the content of active chemical elements increased between 2.6-2.1 ka BP but was still at a relatively low level, suggesting a declining amount of water and diminished inflow. Between 1.2-0.9 ka BP there was a very high content of active elements, suggesting decreased water volume and indicating that the lake was stagnate. In contrast, the general climate condition shows that there had a warm-humid stage at 8-6 ka BP, a cool-humid stage at 6-2.9 ka BP and a warm-dry stage at 2.9-0.9 ka BP in this region. The hydrological evolutions around Xiaohe Cemetery did not have one-to-one correspondence with climate changes. Regional comparison indicates that broad-scale climatic conditions played an important role through its influences on the water volume of the Tarim River and Kongque River. But, the formation of the lakes and their level were controlled by geomorphic conditions that influenced how much water volume could be shunted to Xiaohe River from Kongque River. Human occupation of the Xiaohe Cemetery and nearby regions during the Bronze Age and Han-Jin period （202 BC-420 AD） corresponded to the two earlier lake periods, while no human activities existed in the third lake period because of the decreased water volume.

Urbanization,economic development,and environmental changes in transitional economies in the global south:a case of Yangon

Background:Transitional economies in Southeast Asia—a distinct group of developing countries—have experienced rapid urbanization in the past several decades due to the economic transition that fundamentally changed the function of their economies,societies and the environment.Myanmar,one of the least developed transitional economies in Southeast Asia,increased urbanization substantially from 25%in 1990 to 31%in 2019.However,major knowledge gaps exist in understanding the changes in urban land use and land cover and environment and their drivers in its cities.Methods:We studied Yangon,the largest city in Myanmar,for the urbanization,environmental changes,and the underlying driving forces in a radically transitioned economy in the developing world.Based on satellite imagery and historic land use maps,we quantified the expansion of urban built-up land and constructed the land conversion matrix from 1990 through 2020.We also used three air pollutants to illustrate the changes in environmental conditions.We analyzed the coupled dynamics among urbanization,economic development,and environmental changes.Through conducting a workshop with 20 local experts,we further analyzed the influence of human systems and natural systems on Yangon’s urbanization and sustainability.Results:The city of Yangon expanded urban built-up land rapidly from 1990 to 2000,slowed down from 2000 to 2010,but gained momentum again from 2010 to 2020,with most newly added urban built-up land appearing to be converted from farmland and green land in both 1990–2000 and 2010–2020.Furthermore,the air pollutant concen-tration of CO decreased,but that of NO_(2)and PM_(2.5)increased in recent years.A positive correlation exists between population and economic development and the concentration of PM_(2.5)is highly associated with population,the economy,and the number of vehicles.Finally,the expert panel also identified other potential drivers for urbanization,including the extreme climate event of Cyclone Nargis,capital relocation,and globalization.Conclusions:Our research highlights the dramatic expansion of urban land and degradation of urban environment measured by air pollutants and interdependent changes between urbanization,economic development,and environmental changes.

The ostracod assemblages and their environmental significance in the Chen Co area, southern Tibet in recent 1400 years

The CC1 core, with a length of 216 cm, was drilled in the west part of the Chen Co (Lake) in southern Tibet Plateau. The210Pb and137Cs measurement indicated that it was a consecutive sedimentary sequence since ca. 1400 years. The ostracoda and their assemblages under the level of 1 cm samples’ cutting interval were finished for this core to reveal the past environmental changes in the lake area. A total of 15 species of ostracods belonging to 7 genera in the core sediments had been identified. According to the ostracod distributions, abundances and preservations in the core, seven ostracod assemblages had been distinguished. The ostracod assemblages and their ecological features, together with the sediments dating decision were used to infer the past ca. 1400 years environmental changes of the Chen Co environmental evolutions in three stages, which had responded to the Medieval Ages Warm-period (MAW), the Little Ice Age (LIA) and modern warm period. The results show that the changes of the Chen Co environment had been mainly influenced by the climatic variations. The trend of the lake level fluctuations had been accorded with that of climatic variation during the past 1400 years.

A comparison of climate changes between Arctic and China in the last 600 years

A compilation of paleoclimate records from lake sediments, trees, ice cores, and historical documents provide a view of China and Arctic environmental changes in the last 600 years. Many of these changes have also been identified in sedimentary and geochemical signatures in deep-sea sediment cores from the North Atlantic Ocean, Arctic and Greenland and ice cores from the Qinghai-Tibet Plateau, confirming the linkage of environmental changes of different time scales between the Arctic and China. It is shown that the changes of precipitation, temperature and sea ice cover in Arctic were correlated with climate changes in China. This paper also developed a comparative research on the climate changes between Arctic and China both during the Little Ice Age (LIA) and the instrumental observation period. Cycles and trend of temperature variations during LIA and temperature and precipitation during the instrumental observation period are performed. We found some similarities and differences of environmental changes between Arctic and China.

Inter-Annual Variabilities of the Body Weights of Two Cephalopod Species in the Yellow Sea Under Different Environmental Conditions

As fish stocks have been overexploited and catches have decreased over the last few years,the cephalopod catch has increased globally to the point that they are now among the most important marine resources in the world.Climate change and hu-man activities greatly affect the growth and abundance of cephalopods.Understanding how the individual growth of key species varies and how they respond to environmental changes is essential for an effective fishery management.Loliolus beka and Amphioc-topus fangsiao are two dominant species in the cephalopod community of Yellow Sea(YS).Both of them are commercially impor-tant and have great ecological values.Herein,we compared the body weights(BW)of these two species from 2011 to 2018 based on an analysis of biological parameters(i.e.,mantle length and BW)from trawl surveys in the YS.Considerable temporal variations in the BW of the two species are apparent.Specifically,the BW of L.beka was the lowest in 2011 and the highest in 2017,and the well growth was noted in 2015-2018.The BW of A.fangsiao was the lowest in 2013 and the highest in 2016,while well growth was ob-served in 2015-2016.Mixed-effect models indicate that the BW of these species correlates significantly with the sea surface tem-perature(SST)and Southern Oscillation Index(SOI),suggesting the impact of the regional environment associated with strong ENSO events on BW.In a different response window,growth increases with increased SST and decreases with increased SOI.The consistent patterns of the BW of these cephalopods in response to environmental factors demonstrate they can be employed as indi-cator species for studying environmental change in the YS.Our results improve the understanding of the responses of cephalopods to environmental changes in the YS,as well as the mechanisms that drive their growth.Such information is critical for the effective management and sustainable development of cephalopod fisheries in this region.