Movements of brown bullheads in Presque Isle Bay,Lake Erie,Pennsylvania

Presque Isle Bay, Lake Erie, was listed as an Area of Concern (AOC) by the International Joint Commission in part because of the high incidence of external tumor in brown bullheads. Verifying the source of the possible contaminant exposure is critical to addressing the AOC designation. We used telemetry tracking (n = 49 fish) to test the hypothesis that adult bullheads captured within the bay during spawning season do not exit the bay during the post-spawning summer and fall months. We analyzed genetic variation at 15 microsatellite loci for 112 adult fish from 5 locations, 4 inside the bay and 1 outside, in order to test for possible differences. Data from fixed-station receivers suggested fish did not leave Presque Isle Bay during the study period. Predicted locations outside Presque Isle Bay were only 0.1% of all predicted locations and were below the 0.2% error rate based on known manual relocations. However, there was evidence for movement within Presque Isle Bay. Most movement was between Misery Bay or Lagoons and the open bay area. Whereas telemetry results showed tendency for adult site fidelity, genetic results showed no differences among locations, indicating that there is a single panmictic population. Our telemetry data suggest that brown bullheads are likely a useful indicator species for environmental conditions in Presque Isle Bay, since adults likely are retained in the system.     

Sediment Loading During the 20th Century in Presque Isle Bay,Lake Erie,Pennsylvania

Mud-dominated sediments in Presque Isle Bay are contaminated with metals and hydrocarbons derived from developed watershed and atmospheric sources. Prior to this study, the quantities, rates, and spatial distribution of long-term sedimentation and erosion in the bay were largely unknown. As a result, the fate of contaminated bay-floor sediments and possible rates of natural recovery for this Area of Concern (AOC) could not be determined. To provide baseline data useful to state and federal agencies monitoring recovery of the bay, this paper identifies: (1) the quantities, rates and patterns of 20^th Century sedimentation and erosion, (2) the major sediment inputs and outputs for the bay, and (3) the implications of the sedimentary regime on possible future rates of bay recovery. Bathymetric and sedimentological data show that 20th Century net accumulation totaled approximately 3.94 × 10⁶ m³ which is equivalent to a dry sediment loading of 5.92 × 10⁹ kg (5.92 × 10⁶ t), or 6.29 kg/m²/yr (1.28 lb/ft²/yr) when averaged over the accretional 70% of the bay. This external loading represents approximately 50% of total accretion because externally derived sediments are augmented with resuspended sediments from shallow-water parts of the bay. The principal sediment inputs were littoral drift from ephemeral and permanent inlets (∼42%), artificial infilling along the shoreline (∼28%), streams (∼16%), bank/bluff erosion (∼12%), and biological production (∼2%). Dredging was the principal output. Based on long-term average sedimentation rates and patterns, recovery of the AOC through natural sediment capping will take at least several decades if source contaminants are removed.     

Timescales of transport through Lower Green Bay

Contaminated sediments, poor water quality, and lost or altered habitat in Lower Green Bay and Fox River in the 1980s led to its listing as an Area of Concern by the International Joint Commission. Previous studies on the geophysics and health of the bay demonstrated the need for estimates of transport timescales. Such estimates can contribute to improved understanding of the transport and fate of nutrients, contaminants, and biogeochemical processes in the bay. This study reviews definitions of residence time and flushing time, estimates the temporal distribution of flushing time, the spatial and temporal distributions of residence time, and horizontal diffusivities. The study used a previously developed hydrodynamic model, a drifter experiment, a lake particle transport model, and methods appropriate for the estimation of transport timescales. The estimated residence time for lower Green Bay, 56 ± 16 days, is smaller than a previous estimate of 190 days for the whole bay, and had values similar to the estimated flushing times. The closeness between those timescales demonstrates the important role of water exchange across the Chambers Island transect. Flushing time and residence time do not follow the same trends in monthly variability because the former depends directly on water exchange across Chambers Island, while the later depends, in addition, on tributary inflows and the circulation patterns in the bay. The study includes a discussion of the relations between the timescales of transport and the previous studies of biogeochemical processes, such as trophic conditions, spatial distribution of cyanobacteria, cold-water intrusions, and hypoxia.     

Green Bay,Lake Michigan: A proving ground for Great Lakes restoration

Green Bay has sometimes been referred to as the largest freshwater “estuary” in the world. Its watershed, much of it in intensive agriculture, comprises one-third of the Lake Michigan basin and delivers one-third of the lake's total phosphorus load. At one time, the major tributary, the Fox River, was considered the most heavily industrialized river in North America, primarily from paper manufacturing. Deterioration in water quality and the loss of beneficial and ecological uses have been extensive and began well back into the last century. More recently, the bay has also become a test case for our resolve to remediate and restore ecosystems throughout the Great Lakes and elsewhere. Green Bay has stimulated a significant amount of widely relevant research on the fate and behavior of toxics, biogeochemistry, habitat, biodiversity, and ecological processes. The bay represents a true “proving ground” for adaptive restoration. Key findings of the recent summit on the Ecological and Socio-Economic Tradeoffs of Restoration in the Green Bay Ecosystem are summarized here. Foremost among recommendations of the workshop was the creation of a “Green Bay Ecosystem Simulation and Data Consortium” serving as a data clearing house, building upon the significant progress to date, and developing a modeling framework and visualization tools, furthering public outreach efforts, and ensuring a sustained growth in scientific expertise. Funding was estimated to be on the order of ~$15–20M over the next ~5?years – a modest investment relative to the value of the ecosystem and the long-term cost of inaction.     

Contemporary genetic structure of walleye (Sander vitreus) reflects a historical inter-basin river diversion

River diversions can have unexpected biological consequences. In the mid-20th century, the upper Ogoki River in northern Ontario was diverted from its original Hudson Bay drainage to flow into the Great Lakes. Although walleye were present in both systems prior to the diversion, the Hudson Bay and Great Lakes watersheds had previously been separated since the early Holocene (7500–8500 years ago). We assessed the effects that this inter-basin diversion has had on the genetic structure of two formerly allopatric populations. We assessed the genetic structure and diversity of walleye in the Ogoki and Little Jackfish river systems and Lake Nipigon (number, distribution, and divergence of identified genetic groups) and quantified the contribution of fish from the historical population (Hudson Bay drainage Ogoki River) and Lake Nipigon to walleye in the Ogoki and Little Jackfish Rivers. Walleye from Ogoki Lake, the Ogoki River diversion through the Little Jackfish River, Lake Nipigon and Nipigon Bay were genotyped at 10 microsatellite loci. Significant genetic differences were detected among sampling locations: walleye from Ogoki Lake, presumably representing fish originally from the historical Ogoki River gene pool, were genetically similar to but statistically distinct from walleye within the diversion. Walleye from sample sites within the diversion and Ombabika Bay appear to form a single genetic group that is largely derived from the Ogoki watershed and differs significantly from walleye in Lake Nipigon and Nipigon Bay. Our findings confirm that the historical river diversion has had long-term effects on the genetic composition of contemporary walleye populations.     

Thirty-five years of restoring Great Lakes Areas of Concern: Gradual progress,hopeful future

In 1985, remedial action plan development was initiated to restore impaired beneficial uses in 42 Great Lakes Areas of Concern (AOCs). A 43rd AOC was designated in 1991. AOC restoration has not been easy as it requires networks focused on gathering stakeholders, coordinating efforts, and ensuring use restoration. As of 2019, seven AOCs were delisted, two were designated as Areas of Concern in Recovery, and 79 of 137 known use impairments in Canadian AOCs and 90 of 255 known use impairments in U.S. AOCs were eliminated. Between 1985 and 2019, a total of $22.78 billion U.S. was spent on restoring all AOCs. Pollution prevention investments should be viewed as spending to avoid future cleanups, and AOC restoration investments should be viewed as spending to help revitalize communities that has over a 3 to 1 return on investment. The pace of U.S. AOC restoration has accelerated under the Great Lakes Legacy Act (GLLA) and Great Lakes Restoration Initiative (GLRI). Sustained funding through U.S. programs like GLRI and GLLA and Canadian programs such as Canada-Ontario Agreement Respecting Great Lakes Water Quality and Ecosystem Health and the Great Lakes Protection Initiative is needed to restore all AOCs. Other major AOC program achievements include use of locally-designed ecosystem approaches, contaminated sediment remediation, habitat rehabilitation, controlling eutrophication, and advancing science. Key lessons learned include: ensure meaningful public participation; engage local leaders; establish a compelling vision; establish measurable targets; practice adaptive management; build partnerships; pursue collaborative financing; build a record of success; quantify benefits; and focus on life after delisting.     

What is the extent of water brownification in Lake Onego,Russia?

In the past 26 years the transport of allochthonous matter into Lake Onego has increased. Water brownification in Petrozavodsk Bay, a northwestern bay in Lake Onego, and in the Shuya River, a tributary of the bay, was shown earlier to begin in spring. The goal of this paper was to find out whether brownification spreads from Petrozavodsk Bay to the central part of the lake in summer. Spearman’s correlation coefficient and linear correlation coefficient confirm a significant (p < 0.05) increase in water color in Petrozavodsk Bay in the summers of 1992–2018. A tendency for increasing water color was found in the Central Onego’s epilimnion. Total iron and CO₂ concentrations in the epilimnion have increased and pH values have decreased both in Petrozavodsk Bay and in the Central Onego. In the Central Onego’s hypolimnion, only total iron and CO₂ concentrations have considerably increased. However, the present lake ecosystem is resistant to the increased effect of allochthonous matter due to long water renewal time and self-purification. In spite of a significant increase in CO₂ concentration in the lake water, the bicarbonate buffer system maintains the acid-base equilibrium and the changes revealed are not considered critical for the ecosystem.     

Zooplankton-phytoplankton interactions in Green Bay,Lake Michigan: Lower food web responses to biological invasions

As the largest freshwater estuary in the Laurentian Great Lakes, Green Bay, Lake Michigan (USA) is an important ecosystem presenting both challenges and opportunities for investigating changes in the face of multiple anthropogenic stressors. We collected new data from 2000 to 2007 to assess changes in lower food web interactions after establishment of invasive species (Bythotrephes longimanus and Morone americana in 1988 and Dreissena polymorpha in 1993) and nutrient reductions (1990s). Phytoplankton and zooplankton biomass and composition, as well as primary productivity and zooplankton community grazing rates, were determined along the previously well-studied trophic gradient from the shallow Lower bay to the stratified, open-water Middle bay. A clear trophic gradient still occurred during 2000–2007, with higher nutrients, phytoplankton and zooplankton in Lower bay compared to Middle bay. Phytoplankton abundance and cyanobacteria dominance increased significantly compared to earlier studies. However, integrated primary productivity did not change significantly at either Lower or Middle bay. Zooplankton standing stock decreased in Lower bay, driven primarily by reductions of bosminids, chydorids, and cyclopoid copepods, but did not change in Middle bay. Zooplankton community grazing rates did not change significantly, but shifts in magnitude and seasonality of net phytoplankton growth rates are consistent with increased phytoplankton standing stocks. Changes in zooplankton composition indicate increased predation by invertebrates and decreased fish predation. Shifts in both bottom-up and top-down factors have occurred, with Lower and Middle bay regions more eutrophic and similar to each other as a result of changes in this highly productive Great Lakes embayment.     

A 200 year chronology of burrowing mayflies (Hexagenia spp.) in Saginaw Bay

After an absence of 50 years, burrowing mayflies (Hexagenia spp.) colonized western Lake Erie which led to interest in whether this fauna can be used to measure recovery in nearshore waters throughout the Great Lakes. However, in many areas we do not know if mayflies were native/endemic and thus, whether recovery is a logical measure to assess progress of recovery. In the present study, we construct a chronologic record of relative abundance of burrowing mayflies in Saginaw Bay by the use of mayfly tusks and radionuclides in sediments (i.e., a paleoecologic record) and historic records of mayfly nymphs in the bay. These records reveal that mayflies: (1) were few before 1799, which indicates that nymphs were probably native/endemic in the bay, (2) increased between 1799 and 1807 and remained at relatively high levels between 1807 and 1965, probably in response to increased nutrient run-off from the watershed, (3) declined dramatically between 1965 and 1973, probably as a result of excessive eutrophication in the mid-1950s; and, (4) were few and highly variable between 1973 and 2001, probably as a result of low and unstable abundances of mayfly nymphs. Historic records verify that nymphs disappeared in the bay in the late-1950s to early-1960s which is in agreement with the paleoecologic record. Reoccurrence of low abundances of nymphs in the bay between 1991 and 2008 and comparison of chronologic records of nymphs in Saginaw Bay and western Lake Erie suggest that mayflies may return to Saginaw Bay in the early-21st century. Undoubtedly, watershed conservation and three decades of pollution abatement have set the stage for a recovery of burrowing mayflies in Saginaw Bay, and possibly in other areas of the Great Lakes.     

The Remedial Action Plan That Led to the Cleanup and Delisting of Collingwood Harbour as an Area of Concern

This paper traces the rehabilitation and restoration of Collingwood Harbour's ecosystem and establishes that the targets set to delist Collingwood Harbour as one of 43 North American Areas of Concern were met as of 1994. Numerous actions to ameliorate environmental problems and rehabilitate the harbor ecosystem have been implemented. In so doing, environmental conditions to support the uses and goals identified by the Public Advisory Committee and the community of Collingwood have been realized. The process of cleaning up and protecting Collingwood Harbour's ecosystem has been an extensive one, involving 8 years of legislative, organizational, and information-gathering efforts and a far-reaching program of public consultation and participation. Extensive consultation with agency scientists, government officials, the International Joint Commission, the community of Collingwood, and the public at large has resulted in unified consent that the environmental targets established for the community-driven cleanup have been met, and in fact, surpassed.     

The Role of Sediments in the Nitrogen Budget of Lower Green Bay,Lake Michigan

The extreme southern portion of Green Bay is a shallow (1 to 5 m depth), eutrophic water body which receives considerable nutrients from the Fox River and metropolitan Green Bay, Wisconsin. Research to evaluate the effect of sediments on nitrogen (N) in the bay entailed periodic sampling of waters and sediments at six sites over 20 months and laboratory investigations of the rates of nitrification, denitrification, mineralization, immobilization, and N₂ fixation. The monitoring data indicated that the N concentrations, approximately 0.6 and 0.8 mg/L of inorganic and organic N, respectively, in the bay waters are considerably higher than the threshold limits that may cause algal bloom and aquatic weed problems. Consideration of the available sediment N pool with respect to recognizable N inputs indicated that only 1.2 percent of the yearly N loading from the Fox River is present in the active sediment layer. Nitrification and subsequent denitrification at the sediment-water interface as a result of intermittent wind stirring could be a major sink for N, but presently it has a minor impact due to the high loading rate of N in this ecosystem. The study indicates that even if approximately 50 percent of the present point source loading of N were eliminated by pollution abatement, the N input from nonpoint sources (combined with existing concentrations of phosphorus in the bay waters) would be sufficient to maintain eutrophic conditions.     

Chloride and total phosphorus budgets for Green Bay,Lake Michigan

Green Bay is an elongated freshwater embayment located in northwestern Lake Michigan. Due to its short residence time, the lower bay is heavily influenced by the Fox River's large nutrient load. The inner bay is classified as hypereutrophic and a well-defined trophic gradient is observed moving away from the Fox River towards Lake Michigan, where the bay is nearly oligotrophic. Recent chloride and total phosphorus loading estimates were used to update a chloride and total phosphorus mass-balance model for the bay for 1994–2008. The chloride model provided a means to estimate turbulent eddy diffusion within the bay and exhibited excellent agreement with observed data. The total phosphorus model agreement with observed data was generally good, with the exception of a large deviation in lower Green Bay during 1999–2004. The model was used to estimate the internal loadings necessary to account for the deviation in phosphorus concentrations. The source of the unexpected increase remains unclear, but we speculate significant internal loading due to wind-driven sediment resuspension and hypoxia-induced phosphorus diffusion was significant. These models allow needed reductions to be identified and sourced and also indicate the role internal loading may play in the Green Bay phosphorus budget.     

Modeling the Role of Zebra Mussels in the Proliferation of Blue-green Algae in Saginaw Bay,Lake Huron

Between 1991 and 1993, Saginaw Bay experienced an invasion by zebra mussels, Dreissena polymorpha, which caused a significant perturbation to the ecosystem. Blooms of Microcystis, a toxin-producing blue-green alga, became re-established in the bay after the zebra mussel invasion. Microcystis blooms had all but been eliminated in the early 1980s with controls on external phosphorus loadings, but have re-occurred in the bay most summers since 1992. An apparent paradox is that these recent Microcystis blooms have not been accompanied by increases in external phosphorus loadings. An ecosystem model was used to investigate whether the re-occurrence of Microcystis could be due to changes caused by zebra mussels that impacted phytoplankton community structure and/or internal phosphorus dynamics. The model was first used to establish baseline conditions in Saginaw Bay for 1991, before zebra mussels significantly impacted the system. The baseline model was then used to investigate: (1) the composite impacts of zebra mussels with average 1991–1995 densities; (2) sensitivity to changes in zebra mussel densities and external phosphorus loadings; and (3) three hypotheses on potential causative factors for proliferation of blue-green algae. Under the model assumptions, selective rejection of blue-green algae by zebra mussels appears to be a necessary factor in the enhancement of blue-green production in the presence of zebra mussels. Enhancement also appears to depend on the increased sediment-water phosphorus flux associated with the presence of zebra mussels, the magnitude of zebra mussel densities, and the distribution of zebra mussel densities among different age groups.     

Tweeting the Laurentian Great Lakes: A community opinion analysis about Great Lakes areas as assessed through mentions on Twitter

Accounting for community opinions of environmental restoration is critical both for planning and evaluating these initiatives. While considerable research assesses the value of restoration through economic metrics focusing on expenditures or preferences for ecosystem services, these metrics may not adequately account for the sociocultural services that ecosystems provide communities, such as mental and physical health or recreational opportunities. To address this challenge, we explored the use of social media data to assess online discourse communities’ opinions about ecosystem services through a case study of Twitter mentions of sites targeted for restoration through the Great Lakes Restoration Initiative (GLRI). While there is evidence of the economic and ecological benefits of GLRI, little is known about how these benefits at sites targeted for funding are perceived by the public. From April through October 2019, we collected 40,000 tweets that mentioned an Area of Concern or a Great Lakes National Park that received GLRI funding. We used a mixed-methodological approach combining tweet content and sentiment analysis to determine themes of discussion and characterize online discourse communities’ opinions around these topics. Half of all tweets were about one of three Areas of Concern, and recreation was the most discussed theme with an overall positive sentiment. A metric accounting for the number of tweets and the sentiment of tweets was derived to understand community opinions of restoration at these areas. Our findings demonstrate the potential of social media data mining as a tool for examining online conversations about and engagement with the Great Lakes.     

The Green Bay saga: Environmental change,scientific investigation,and watershed management

The Green Bay watershed, draining a total area of approximately 40,468?km², comprises about a third of the Lake Michigan drainage. In the early years, fur trade was the dominant economic activity within the watershed. Later, when timber harvesting, papermaking, and agriculture came on the scene in the 19th and early 20th centuries, major environmental changes occurred in a relatively short period of time. Nutrient and sediment loadings, accompanied by organic wastes from sawmills and paper mills, resulted in a pollutant overload in the Fox River and in the eutrophication of the waters of lower Green Bay. Citizen complaints about these severely degraded conditions initiated a period of scientific investigation. Starting slowly with a few studies and surveys in the first half of the 20th century, serious investigatory work began at mid-century with support from the University of Wisconsin Sea Grant Institute. Examples of topics that have been investigated since then with support from numerous sources are: biological oxygen demand (BOD), phosphorus and total suspended solids loads, trophic status and food chain efficiencies, coastal wetland characterization, dynamics of the benthic layer, algae and abiotic solids, phosphorus cycling and mass balance, PCBs, seasonal hypoxia, and climate change impacts. These studies have provided the scientific foundation for government-led programs such as the Green Bay Remedial Action Program, the PCB clean-up program, and the TMDL program. Progress has been made—reduction in BOD is an example—but a fuller rehabilitation of this large-scale ecosystem remains an elusive goal. The saga goes on.     

THREE-DIMENSIONAL NUMERICAL SIMULATION OF TIDES AND CURRENTS IN FUSHAN BAY, QINGDAO

The three-dimensional Princeton Ocean Model (POM) was employed to simulate the tide and current simultanuously for the first time in the Fushan Bay, Qingdao, China By adopting the elevation condition that was combined with the tides M2, $2, K1 and O1 at the open boundary and by choosing the proper value of bottom roughness, the horizontal and vertical distributions of the tidal current and water level variations in the bay were computed. The results agree well with the field observation data, indicating that this model can be used to predict accurately the variation of tides and currents in the Fushan Bay and other costal regions in the future.Our study also provides useful information and a data base for the Olympic Projects that will be conducted in the Fushan Bay in 2008.     

Phytoplankton Productivity in Saginaw Bay,Lake Huron: Effects of Zebra Mussel (Dreissena polymorpha) Colonization

Phytoplankton photosynthesis-irradiance parameters, chlorophyll concentrations, underwater extinction coefficients (kPAR), and surface irradiance were determined at 8–10 sites on 27 occasions in Saginaw Bay from spring 1990 through fall 1993 corresponding to a period before and after the establishment of large zebra mussel populations (began in summer 1991). Similar measurements, with the exception of the photosynthetic parameter, α, had also been made in 1974/75 at eight sites on nine occasions. In inner Saginaw Bay where zebra mussels were primarily found, chlorophyll and kPAR values decreased, while the photosynthetic parameters, P_max and α, increased after zebra mussel colonization. At sites in the outer bay where no zebra mussels were found, chlorophyll and kPAR values did not change after zebra mussel colonization, whereas photosynthetic parameters increased. Decreases in chlorophyll and kPAR in the inner bay were related to the zebra mussel, but increases in photosynthetic parameters in both the inner and outer bay were not. Areal-integrated and volumetric phytoplankton productivity decreased by 38% and 37%, respectively, in inner Saginaw Bay after the establishment of zebra mussels; phytoplankton productivity at outer bay control sites was similar during the same period. Decreased phytoplankton productivity in the inner bay was attributable to the large decrease in chlorophyll as increases in underwater irradiance (increased kPAR) and photo synthetic parameters could not compensate for the chlorophyll effect. Increase in underwater irradiance produced a significant increase in light to the benthic region and contributed to increased benthic primary productivity; ratio of photic zone to station depth increased in inner Saginaw Bay, from 0.6–0.8 before the zebra mussel colonization (1974–1990) to 1.1–1.3 after colonization (1992–1993). Overall, primary productivity in the inner bay did not exhibit a notable change after zebra mussel colonization as decreases in phytoplankton productivity were accompanied by increases in benthic primary productivity. Thus, zebra mussels altered inner Saginaw Bay from a pelagic-dominated system to a benthic/pelagic system which will have long-term effects on food web structure and productivity at higher trophic levels.     

Trends in the distribution and abundance of Hexagenia spp. in Saginaw Bay,Lake Huron, 1954–2012: Moving towards recovery?

Since at least the 1940s, multiple anthropogenic disturbances to the Laurentian Great Lakes have had detrimental effects on benthic habitats and biota including decimating the environmentally sensitive burrowing mayfly genus Hexagenia around the mid-1950s. While remediation efforts have facilitated recovery of some populations, benthic surveys in Saginaw Bay, Lake Huron in the last 50 years have only occasionally discovered Hexagenia nymphs. Recently, adult Hexagenia swarms have been reported near the bay; therefore, we corroborated the local presence of Hexagenia adults and evaluated the current status of Saginaw Bay Hexagenia nymphs. We quantified adults during mayfly emergence events in 2010 at three Tawas City, Michigan, USA area locations, and found > 17 Hexagenia/m²/site. We quantified nymphs from Ponar grab samples collected at 57 sites in Saginaw Bay between 2009 and 2012, and found 1.5 nymphs/m² overall with nymphs present at 15.8% of sites sampled, their greatest documented distribution in Saginaw Bay since 1956. Additionally, we mapped bay sediment composition and related sampling site abiotic conditions with both Hexagenia presence and abundance using Zero-Inflated Poisson regression. Model results indicate that the probability of observed Hexagenia absence being true absence is positively related to both sediment sandiness and surficial dissolved oxygen concentration while Hexagenia abundance is greatest where surficial temperatures are ~ 18.6 °C and is also related to sediment sand content. The documentation of nearby adults and in bay nymphs may indicate the beginning of a Hexagenia return to Saginaw Bay, and, therefore, a possible improvement of the ecosystem's benthic health.     

Evaluating Economic Value of Coastal Waterfront in Tokyo Bay, Japan with Willingness-to-Accept Measure

The total economic value of a coastal waterfront or coastal zone is important for policymakers and analysts concerned with coastal issues to evaluate policies that affect coastal management. A coastal waterfront as common goods is usually valuated with a measure of willingness to pay (WTP) for the improvement of coastal ecosystem functions from a demand side. However, there is a trend that the landscapes of a coastal waterfront like viewing the sea should be regarded as one of the property rights of coastal residents in Japan. Thus a coastal waterfront is necessarily evaluated with a measure of willingness to accept (WTA) the compensation for the loss of the accessibility to a coastal waterfront from a supply side because a number of empirical literatures show that WTP is usually substantially lower than WTA. This paper elicits the WTA for the loss of accessibility to coastal waterfronts using contingent valuation method provided that the accessibility should be regarded as one part of residents’ property rights. The result shows that the WTA in Tokyo bay is 65.3 million yen per household, more than ten times their annual household income. The total economic value of Tokyo bay is estimated as 539 trillion yen, which can be taken into consideration in the coastal risk assessment process to evaluate the efficiency of coastal risk reduction measures.     

粤港澳大湾区韧性内涝防治体系研究

粤港澳大湾区是我国开放程度最高、经济活力最强的区域之一,在国家发展大局中具有重要战略地位.近年来,粤港澳大湾区极端天气频发,且高度城镇化建设改变了下垫面情况.粤港澳大湾区的战略地位及其遭受内涝灾害所可能产生的巨大损失决定了该区域内涝防治的重要性.探讨了韧性体系的概念及演进过程,并结合粤港澳大湾区高度城镇化区域的内涝特征...