Estuaries are subject to increasing pressures due to local human activities. In addition, global change is affecting coastal habitats. Such disturbances impinge on goods and services provided by these ecosystems. The paper is devoted to efforts to restore environmental quality in some industrialised estuaries during the few past decades. It then compares strategies to recover damaged habitats and methods to restore lost ecological functionalities. Case studies are taken from the Seine in France, the Humber in England, the Scheldt in Belgium and the Netherlands and the Elbe in Germany. The article retraces briefly the morphological and ecological changes which have been inflicted on the estuaries over the last century. It puts into light actions which have been successful in improving their ecological functioning. Through comparing the various restoration schemes, policies are assessed. Details are given on efforts made lately in the Seine estuary which has lost more than 90% of its intertidal areas in about 150 years. Recently, losses due to an extension of harbour facilities in le Havre (“Port 2000”) have been compensated by the rehabilitation of a former mud flat and various constructions such as an artificial island for birds. The discussion confronts the present management of tidal estuaries to future challenges, including global changes. Such changes will not only include global warming and its consequences (sea level rise, biogeochemical cycles alteration...), but also socio-economic adjustments and a possible geo-political reorganization expected to take place in relation to increased harbour activities and the increasing need for more space dedicated to natural habitats and leisure activities (sports, tourism...). The conclusion puts together the various approaches from the considered European estuaries. Resting on a rigorous scientific approach, it proposes a synthetic approach to restoration: 1. Efficient procedures of socio-ecological evaluation, 2. A methodology to assess the ecological quality of systems considered, 3. Rigorous monitoring programs, resting on a relevant choice of indicators, and 4. Participation of local communities, in order to define strategies compatible with conservation and sustainable development at the local, regional and European levels.
This paper presents a systematic approach to coastal restoration projects with five components: planning, implementation, performance assessment, adaptive management, and dissemination of results. Typical features of the iterative planning process are synthesized, beginning with a vision, a description of the ecosystem and landscape, and goals. The conceptual model and planning objectives are developed, prioritization techniques are used for site selection, and numerical models contribute to preliminary designs as needed. Within the planning process, cost analysis involves budgeting, scheduling, and financing. Performance criteria and reference sites are selected during design of the monitoring program. Particular emphasis is given to the monitoring program, used as a tool to assess project performance and identify problems affecting progression toward project goals, within an adaptive management framework. Key approaches to aspects of the monitoring program are reviewed and detailed with project examples. Another important means of strengthening the restoration project or program is documentation, peer review, and the distribution of information outside the planning team prior to finalizing construction plans, during implementation, and throughout monitoring and adaptive management.
Mudflats are formed in the upper littoral zones in estuaries, especially in the innermost part of macro-tidal embayments (upper reaches of estuaries), providing a habitat for peculiar fauna and flora. The peculiar fauna and flora of estuarine mudflats appear to have been extirpated in many estuaries in Japan, along with the mudflats that have been damaged or destroyed by thoughtless and drastic coastal reclamation. At present, Ariake Bay, which constitutes the largest area of mudflats remaining in Japan, also has the greatest variety of species. The mudflat-specific species are almost or completely restricted to Ariake Bay, while populations of the same (or closely related) species are distributed along Asian continental coasts, which suggests they are continental relicts. Some of the mudflat-specific species now restricted to Ariake Bay (e.g.,the bivalve, Tegillarca granosa, the polychaete, Hediste japonica, the salt marsh plant, Suaeda japonica) previously enjoyed a wide distribution in Japan. Even within Ariake Bay, huge mudflats in Isahaya Bay were recently lost to a reclamation project there. The high productivity of benthic organisms in mudflats seems to benefit carnivores such as birds and fishes (e.g., Japanese eel). Conservation and restoration of mudflats are needed to conserve endangered species and to maintain traditional human fisheries and culture. From this aspect, restoration of the largest mudflats in Isahaya Bay in Ariake Bay is highly desirable.
This study investigates shell growth patterns and the reproductive cycle of the Mediterranean mussel Mytilus galloprovincialis in Tokyo Bay, central Japan. A follow-up study of marked mussels within the intertidal zone from July 2007 to September 2008 indicates a remarkably fast annual shell-growth rate and a short life span, reaching the maximum shell length (ca. 70 mm) at age 3 or 4 years. Histological examinations of mussel gonads collected fortnightly revealed that the Tokyo Bay population has a spawning season between late autumn and spring, and attains sexual maturation several months after recruitment. Shell growth patterns for individual mussels show seasonal variations, with high shell-growth rates during spring and summer, and minimal growth from late autumn to early spring. Slow shell growth during winter is possibly controlled by combined environmental (lower air and seawater temperatures, and scarce phytoplankton) and physiological (the reproductive effort expended in gametogenesis and spawning) factors.
To evaluate and conserve the biodiversity of tidal flats, quantitative research studies and precise identification of benthos species are required. However, there has been no convenient procedure for conducting a benthos survey by common people attempting the conservation of tidal flat ecosystems. In this paper, we describe our attempts to make a civil procedure with a method that is not only simple but also semi-quantitative and analytical. From field tests and field practices, we propose the following method as the civil procedure. At least 8 people are necessary for this work, which entails collecting epifauna during a 15-min search and infauna from 15 holes dug with a small scoop. After collection, the benthos species are identified in the fields through the help of experts and by referring to a handy-sized guidebook with pictures of benthos species. Then, the benthos species are recorded by checking on the tidal flat benthos check sheet. Next, numbers of the check marks for respective species recorded on every check sheet are transcribed to a new sheet (to ascertain how many people collect each species). The total number of species recorded on this combined sheet signifies species richness, with >70% check mark recorded being evaluated as dominant, 70–10% as common and <10% (or collected by only 1 person) as a rare species. Since the civil procedure is designed to be conducted by more than 8 people, deviations due to personal idiosyncrasies would be eliminated. Therefore, the civil procedure we proposed would be not only simple and easy for beginners but also semi-quantitative and analytical. It might be possible to make significant comparisons with other tidal flats and it might be prove useful for long-term monitoring by the public.
Morphological and genetic traits of Meretrix lusoria and M. petechialis were compared among individuals from Japan and Korea. Multivariate analysis of shell morphology revealed that M. lusoria from all localities of Japan (Aomori to Kyushu) and from the southern and southwestern coasts of Korea (Sacheon Bay and Gangjin Bay) have some common characters, namely more linear shape in posterior-dorsal margin, smaller width of socket and larger shell breadth rather than M. petechialis from the western coasts of Korea (Baeksu and Saemangeum). Among M. lusoria, individuals from the Japan/East Sea coasts (Yuya Bay, Aso Sea and Mutsu Bay) have more linear shape in posterior-dorsal margin than those from other localities. The distribution border between M. lusoria and M. petechialis is located around the southwestern coasts of Korea (from Gangjin Bay to Baeksu). Analyses of mitochondrial COI and nucleus ITS also revealed that individuals from Japan and the southern coasts of Korea (Sacheon Bay) were classified as M. lusoria, and those from the western coasts of Korea (Baeksu and Saemangeum) as M. petechialis. However, all individuals from Gangjin Bay were classified as M. petechialis based on the analysis of mitochondrial COI, although most individuals were classified as M. lusoria by the analysis of nucleus ITS. These results suggest that hybridization between M. lusoria and M. petechialis occurs around Gangjin Bay. Further, we established a method to identify M. lusoria and M. petechialis from shell morphology. The modified discriminant score using the 5 selected characters, i.e. shell length (L), shell breadth (B), width of socket (SW), length of posterior-dorsal margin (LPM) and height of posterior-dorsal margin (HPM), is D = 110.26−61.61(log B/log L) + 10.90(log SW/log L) − 81.72(log LPM/log L) + 27.27(log HPM/log L). Using this discriminant score, we can identify M. petechialis and M. lusoria with 98.89% correct percentage.
The phylogeography of local populations of the direct-developing estuarine polychaete Hediste atoka was examined by comparing the partial nucleotide sequences of the mitochondrial gene for cytochrome oxidase subunit I (COI) from 67 individuals collected from 27 sites that cover the majority of the distribution area of this species along the Japanese coasts, and from two sites of the Korean coasts. The phylogenetic trees drawn by four different methods (maximum likelihood, neighbor-joining, minimum evolution and maximum parsimony) showed consistently that populations of H. atoka could be divided into two parapatric forms: form A constituted all Korean and most Japanese populations except for those in southern Japan (southwestern Kyushu and the Ryukyu Islands), occupied by form B. No morphological differentiation has been detected between the two forms; the number of paragnath on the proboscis of each group was not significantly different from each other. The geographical distributions of these two forms did not overlap each other. These results suggest that cryptic speciation may occur in H. atoka.
The phylogenetic relationship among the genus Cerithidea including an unidentified congeneric species referred here as species A collected in Suncheon Bay were inferred from nucleotide sequences of the mitochondrial gene for cytochrome c oxidase subunit I (COI). Their genetic structures were compared with other congeneric species and their local populations around Japan and Ryukyu Islands. A single C. cingulata haplotype was detected to be shared between the Suncheon Bay and Yatsushiro populations and it was the most dominant haplotype in both populatioms. The monophyly of species A was supported by a high bootstrap probability (100%) in the analysis using the neighbour-joining (NJ) method, which showed a closer relationship of this unidentified species with C. alata from Thailand and C. microptera from the Philippines than with other Cerithidea species. C. cingulata, C. largillierti, C. djadjariensis and species A populations in Suncheon Bay can be characterized by a low genetic diversity. These characteristics should be attributed to geographical factors, and further study of the connectivity of Suncheon Bay and the habitats in the outside of the bay could shed light on this interesting theme in conservation ecology.
As a social activity in “Korea and Japan Joint Symposium on Biology of Tidal Flats 2009” held in Sucheon, Jeollanam-do, the southern part of South Korea, most of the participants to the symposium joined the surveys with the purpose of making a list of macrobenthic fauna that occur on Suncheon Bay Tidal Flats with approximately 1,200 ha in total area between June 21 and 23, 2009. In this survey, sixteen species of bivalves, twenty species of gastropods, one species of chiton, fourteen species of polychaetes, eight species of crabs, and three species of other animals were collected, and identified by the participants. Among these sixty-one species, two species of macrobenthic invertebrate animals including gastropod, Ellobium chinense, and crab, Sesarmops intermedius, are listed in the latest Red List of the Ministry of Environment of the Republic of Korea, and eight species of them including five species of potamidid gastropods are listed in that of the Ministry of Environment, Japan. The results of this survey indicate that the ecosystem on the tidal flats in Suncheon Bay are still healthy, and preserved almost in their original conditions, due to the serious efforts of the people in Suncheon City and the municipal authorities.