The evolution and degeneration of ecosystem in estuary and coastal zone are becoming a general trend worldwide. Bohai Sea, as an important semi-enclosed in land sea in China, was undergoing degenerating resulting from deteriorated environment by climate changes and anthropogenic disturbances.
Macrobenthic assemblages plays a key role on the cycle of energy and materials in marine ecosystem. Due to their unique living pattern, macrobenthos community and its succession are always the first choice of bio-indicator to reflect the ecosystem health and the long terms changes of marine ecosystem.
The first survey on macrobenthic assemblages of Bohai Sea began with 1950s', and several surveys were carried out after that. By these investigations, the species composition, community structure, function group, secondary production and biodiversity of Southern Bohai Sea were progressively uncovered. However, most of them focused on short term period (less than 2 years), and few on long term succession of macrobenthos in Southern Bohai Sea.
Recently, an article titled "Long-term trends of macrobenthos in southern Bohai sea, China in relation to environmental changes" was published in Scientia Sinica Vitae (2016) 46(9), 1121-1134.doi: 10.1360/N052016-00063. Researchers analyzed the community structure based on historical and current data of 2011 and 2013. Over the past 60 years, the macrobenthic assemblages of Southern Bohai Sea have underwent some extent succession, including the temporal and spatial changes of species composition, the key species, the biomass and abundance, the biodiversity and the distribution pattern. K strategy species with long life, large size and high competitive advantage was progressively replaced by the R strategy species with short life, wide adaptability and high reproductive capacity.
According to the yearly fluctuation of species number, biomass and abundance, the succession process can be roughly divided into three periods (Figure 1), e.g. first period: before 1960s, the characters of macrobenthic fauna was presented by relatively low total species number, high value of biomass and abundance; commercial molluscs and crustacean as the two dominant groups; Second period: from 1980s to 2006, the macrobenthic fauna was representative of increasing species number, decreasing biomass values; small body sized mollusks and echinoderms becoming the dominant groups; Third period: after 2006, the increased value of biomass and dominated groups of molluscs and crustacean in macrobenthic community reflected a certain degree of recovery in bioresource.
China's coastal economy and the intensification of human sea-related activities shows a rapid development over past 60 years. The structure and function of the marine ecosystem in Bohai have also underwent dramatic changes and degradation. Environmental parameters such as seawater salinity, temperature, DIN, and N:P ratio exhibited positive trends, while DO, P, Si, and Si:N ratio exhibited negative trends in Bohai sea (Xuren Ning et al. in 2010). "Environmental changes change the spawning, feeding, wintering grounds and migration routes of biological resources, and then affect the recruitment in populations. Anthropogenic activities such as over-fishing reduce the trophic level of the marine ecosystem, shorten the food chain, cause the food web tending to be simple, and ultimately lead to the miniaturization of species in body size " they explained.
This study fully confirms the long term investigation and analysis of macrobenthors is an effective way for the quantitive study on long-term changes of environmental changes and biological responses to the human activities. This work clarified the succession of macrobenthic community in southern Bohai sea which is very important to deeply understand the service and function of Bohai ecosystem and to rationally develop and utilize the biological resources in Bohai sea.
This research was funded by Strategic Priority Research Program of the Chinese Academy of Sciences (XDA11020403 & XDA11020702), Key Research Program of the Chinese Academy of Sciences (KZZD-EW-14) and Science and Technology Service Network Initiative of the Chinese Academy of Sciences (KFJ-EW-STS-127).
See the article: Linlin Chen, Quanchao Wang, Xiaojing Li, Zhengquan Zhou, Baoquan Li. "Long-term trends of macrobenthos in southern Bohai sea, China in relation to environmental changes," Scientia Sinica Vitae (2016) 46(9), 1121-1134.doi: 10.1360/N052016-00063
This article was published online, in the Scientia Sinica Vitae, by Science China Press.