A comparative method for evaluating ecosystem services from the viewpoint of public works

Nature-based solutions (NbS), such as the implementation of environmental conservation and restoration as public works projects, require accurate and cost-effective assessments of the values related to the projects. The values should represent collective ecosystem services, individual services such as food provision and water purification, and other intangible services. To comprehensively assess such services, we proposed a novel method, which we call the comparative evaluation method. Our method is able to assess the value of each service category of an NbS project from a single questionnaire survey. Survey participants are asked to compare values of multiple services having anchoring prices. Our method determines the permissible economic value of environmental public works (PEP) in response to the quantity of service. The questionnaire results used for analysis are limited to those from respondents who made their PEP evaluation on the basis of their consideration of the appropriate expenditure of taxes. In addition, the method controls for the effect of the satisfaction that a person experiences from doing good deeds to reduce an overestimation of the values of services. Moreover, PEPs are not influenced by the respondent's annual income, age, sex, or educational background, and are based on personal values. Applying this new method, we surveyed residents of the watersheds of Tokyo Bay and Osaka Bay and evaluated nine ecosystem services. Overall, our new method is shown to be an effective method for evaluating the ecosystem services of NbS projects from the viewpoint of public works

Green port structures and their ecosystem services in highly urbanized Japanese bays

Green port structures (i.e. green infrastructure in ports and harbors) featuring habitats for marine organisms have been promoted in Japan as part of a comprehensive policy to reduce the environmental impact of ports and carry out habitat conservation, restoration, and creation. In this study, we evaluated the ecosystem services provided by green port structures in two highly urbanized bays (Tokyo Bay and Osaka Bay) in Japan. Our results show that the provision of some ecosystem services can be limited by circumstances particular to ports and other areas with restricted access. In the case of green port structures that have strong usage restrictions, for example, cultural services can only be provided if relevant authorities are prepared to conduct public events while ensuring participant safety. On the other hand, green port structures with weak usage restrictions are often equipped with incidental facilities such as parking lots and restrooms; these facilities can enhance the provision of cultural services (e.g. recreation and environmental education). Green port structures in highly urbanized bays often have usage restrictions, but their proximity to large populations means that they can potentially provide numerous ecosystem services. However, our study shows that appropriate management goals, such as protecting species and ensuring healthy habitats, are needed to maintain the value of these services in highly urbanized and eutrophic bays

TEMPORAL VARIATION OF CARBON DIOXIDE FLUX ON OMAEHAMA IN INNER PART OF OSAKA BAY

本研究では兵庫県西宮市に位置する大阪湾湾奥の御前浜において渦相関法を用いたCO2フラックスの時間変動およびCO2フラックスと水質の関連性を明らかにすることを目的に調査を行った．観測期間中のCO2フラックスは-0.90~0.67mgCO2/m2/sで変動しており，すべての小潮で吸収，大潮の3回の内，2回は放出を示した．また，小潮における昼間のCO2フラックスは夜間の約2.8倍の吸収を示した．CO2フラックスと表層の水質の関係性について，相関係数が0.5以上のCO2フラックスと関係性の強い変数はなかった．大阪湾湾奥におけるCO2フラックスは小潮で吸収傾向，大潮で放出傾向であり，貧酸素・無酸素状態，成層の緩和や硫化水素の発生といったイベントとの関連性は認められず，CO2フラックスは時間変動していることが考えられた．To reveal the relationship between temporal variation of CO2 flux and water quality using eddy correlation method at Omaehama beach in the inner part of Osaka Bay was conducted in this study. During the observation period, the CO2 flux fluctuated between -0.90 and 0.67 mgCO2/m2/s. CO2 was absorbed in all the neap tides, and was emited in spring tides. In addition, CO2 flux at daytime was absorbed about 2.8 times than that at night in the neap tide. There was no strong correlation CO2 flux and the surface water quality. It was thought that CO2 flux in the inner part of Osaka Bay fluctuated with neap and spring tide. Therefore, CO2 flux was effected by tide, but not events such as hypoxia, stratification and occurrence of hydrogen sulfide

CHANGES IN THE DISTRIBUTION OF INTERTIDAL ATTACHED ORGANISMS OF UPRIGHT STRUCTURES WITH DECREASING NUTRIENTS IN OSAKA BAY

本研究は大阪湾沿岸の付着生物の調査を実施し，栄養塩低下と付着生物の分布の関連性を明らかにするために検討を行った．具体的には13年前に実施した調査地点を中心に調査を行った結果，生物相に大きな変化はなかったが，春季の海藻の種数は湾奥において増加しており，ワカメやクロフジツボ等の付着生物は環境勾配の変化に従って，湾奥に分布域を拡大していた．長期間のモニタリングデータを用いて大阪湾沿岸の水質変化を検討した結果，2000年からの栄養塩は減少していた．また，水質を用いて特徴的な生息分布を示した生物種に関し，Maxentを用いて分布に寄与する要因を解析した結果，栄養塩を主として透明度や塩分，護岸構造物の種類が寄与していると考えられた．大阪湾沿岸における栄養塩の低下は付着生物の分布に影響を及ぼしていることが示唆された．To clarify the relationship between attached organisms and decreasing nutrients, we investigated attached organisms in the coastal area of Osaka Bay. There was no significant change in the biota, but the number of species of seaweeds in the spring increased in the inner part of the bay, and the number of attached animals in the summer increased south of inner part in Osaka Bay. In addition, the number of attached animal species increased south of inner part at Osaka Bay in summer. Some of the attached organisms have expanded their spatial distribution to the inner part of the Osaka bay. Water quality changes in the coastal areas of Osaka Bay were examined using long-term monitoring data. The results showed that nutrients in the coastal areas of Osaka Bay have decreased since 2000. Distribution of some species that showed characteristic habitat distributions, were analyzed the factors contributing to the distributions, and the results indicated that nutrients contributed to the spring distribution. The results suggest that low nutrient levels in coastal areas of Osaka Bay affect the distribution of attached organisms

THE MAIN CAUSE OF “SINKING EVENT” AT A COMPENSATIVE ARTIFICIAL TIDAL FLAT IN OKINOSU, TOKUSHIMA CITY

徳島市沖洲地区にある人工海浜は，埋め立てられる既存海浜の代償措置として造成されたが，既存海浜の底生生物相を再現できていなかった．決定的な違いはホソウミニナの有無であり，その原因は沖洲人工海浜で確認されている「沈み込み現象」によるものと推察された．筆者らは「沈み込み現象」の発生原因として，ニホンスナモグリに着目した．その結果「沈み込み現象」は，ニホンスナモグリの生息域のみで発生していること，加えてニホンスナモグリを排除すると「沈み込み現象」は発生しないことを示した．また，ニホンスナモグリはホソウミニナの生残に負の影響を与えることも分かった．しかしニホンスナモグリを排除することで，底生生物相が貧弱になる結果も示されており，ニホンスナモグリが干潟生態系へ与える影響は極めて複雑であることが示された．An artificial tidal flat was created in 2007, to compensate for the loss of a natural tidal flat, at Okinosu, Tokushima City. However, five years after its creation, it was found that the ecological conditions in the artificial habitat of benthic animals differed vastly from those in the natural habitat. In particular, the mud snail Batillaria cumingi, which dominates natural tidal flats, was rarely found in the artificial habitat.  We tested the hypothesis that the “sinking event” was caused due to bioturbation by the ghost shrimp, Nihonotrypaea japonica. The “sinking event” occurred only at the places where N. japonica was abundant. Therefore, it seemed that bioturbation by N. japonica was the cause of the “sinking event”. Although exclusive treatment with N. japonica led to a low-biodiversity assemblage, N. japonica has both positive and negative effects on the tidal flat ecosystem

FISH DIVERSITY DETECTION AT THE INNER PART OF OSAKA BAY USING ENVIRONMENTAL DNA ANALYSIS

大阪湾奥に位置する尼崎運河において，環境DNA調査と捕獲調査を比較して運河内スケールにおける環境DNAの有効性と問題点を検討し，各調査地点の魚類相の比較および環境条件との関連を明らかにした．東堀では1月の表層のORPやDOが回復し，同時期の環境DNAにより検出された種数が最も多かった．このことから，この場所が水質の回復によって魚類の利用場所となるポテンシャルを持っている可能性が示唆された．環境DNA調査はより環境の異なる港湾との比較や季節変化については差の検出が可能であった．環境DNA調査は検出は不安定で，検出できない種もあるが，採捕調査よりも多くの魚種を検出する傾向にあり，直接採捕の調査と合わせると互いの調査方法の結果を補い，魚類相全体の把握に有効な手法であると考えられる．Fish diversity at at Amagasaki canal in the Inner Part of Osaka Bay were investigated by environmental DNA analysis (eDNA) to clarify whether this method is valuable in eutrophic conditions. A ORP and DO was restored in January in Higashi-bori sampling point and the detected fish species was larger number than the other time. The result suggests that Higashi-bori has a potential for fish habitat with a water quality recovery. The number of detected species and fish fauna suggests that eDNA is efficient in comparison among sampling points which has sharp contrast of environmental factors and monitoring seasonal difference. The eDNA is unable to detected a certain species, but allow to detect larger number of species than the conventional sampling methods. eDNA is most effective when used in conjunction with conventional sampling method for investigation of fish diversity

Experimental Consideration of the effects of Hydrogen Sulfide on Ruditapes philippinarum

Various laboratory experiments were performed to examine the effects of H2S (Hydrogen Sulfide) on R. philippinarum in this study. These results were as follows. 1) Most of clam closed its shell, in case was placed in the anoxic water. However, the number of clam that opened its shell increased with time. 20 hours later, the dying clam appeared after the clam extended the siphon and pelecypod. 2) H2S exposure had an insignificant effect on the clam, they closed shells. However, the clam was significantly affected by H2S exposure when they opened its shell and extended siphon and pelecypod. 3) When the water was hypoxic or anoxic before Blue tide occurrence (Aoshio), the clam would directly suffer severe effects of H2S because the extended soft tissue from the inside of shell was exposed

CARBON DIOXIDE FLUXS AT WATER AND SEDIMENT IN THE URBAN COASTAL TIDAL FLAT OF OSAKABAY

本研究では大阪湾沿岸部の13地点の干潟を対象に水質項目，底質環境，水面と堆積物のCO2フラックスを定量化し，その関係性を明らかにすることを目的に調査を行った．大阪湾の干潟は全体的に砂質で構成されており，化学的性状から好気的な環境であった．水面におけるCO2フラックスは13地点中8地点で放出を示し，湾奥の河川の影響が強い地点でCO2は放出傾向にあった．堆積物における1日当たりのCO2フラックスは矢倉海岸と男里川を除いてCO2は放出であり，1日当たりのCO2フラックスは水面より高いことから，堆積物では有機物の分解の場としてCO2は放出されていることが推察された．以上のことから，干潟では水面からCO2は放出傾向であり，堆積物は干出することで，有機物の分解が促進されてCO2は放出していることが考えられた．The objective of this study was to quantify the relationships between water surface and sediment CO2 fluxes on 13 tidal flats in the coastal area of Osaka Bay. The tidal flats are generally composed of sandy sediments, and their chemical properties indicate an aerobic environment. CO2 fluxes at the water surface of the tidal flats showed a release at 8 of the 13 sites, and CO2 tended to be released at the sites with strong river influence at inner part of Osaka bay. The daily CO2 flux in the sediments was higher than that in the water surface, suggesting that CO2 is released in the sediments as decomposition of organic matter. These results suggest that CO2 tends to be released from the water surface on tidal flats, and that CO2 at sediments is released by the decomposition of organic matter accelerated in low tide

CHARACTERISTICS OF CARBON FLOW ON PELAGIC ECOSYSTEMS AT HYPERNUTRIENT AREA IN AMAGASAKI CANAL

本研究では，大阪湾湾奥に位置する尼崎運河における植物プランクトン，動物プランクトンおよびコウロエンカワヒバリガイの現存量・生産速度を定量化することで，一次生産者から二次生産者へ至る年間の炭素フローを算出し，転送効率について評価した．植物プランクトンによる一次生産速度は他の水域に比べて高く，動物プランクトンの個体数，二次生産速度は低かった．年間を通して，植物プランクトンから動物プランクトン，コウロエンカワヒバリガイの転送効率はそれぞれ0.76%，7.8%であり，合わせて8.6%の有機炭素が二次生産者へ移行していた．運河ではコウロエンカワヒバリガイは効率よく成長して炭素を固定しているが，動物プランクトンは食物連鎖において魚類の現存量・生産速度に影響していることが示唆された．The purpose of this study was to reveal the carbon flow from primary producer (phytoplankton) to secondary producers (zooplankton and Xenostrobus securis), transfer efficiency at hyper-nutrient area in the Amagasaki Canal of inner part of Osaka Bay. The primary production rate was higher than that of other water area, while zooplankton biomass and secondary production rate were lower. The production rate of X. securis was about 1/12 of that of phytoplankton, but biomass was about 29 times higher. Transfer efficiency from phytoplankton to zooplankton and X. securis was 0.76% and 7.8%, respectively. These results suggested that X. securis grew efficiently and fixed organic carbon, zooplankton were not functioning properly as intermediaries in the food chain between phytoplankton and fishes