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The physical, chemical, and biological dynamics under changing atmospheric conditions of Laguna Lake, Philippines were analyzed from intensive observations. Diel measurements were conducted for 48 continuous hours for both dry and wet tropical seasons in addition to fine resolution long-term monitoring. Results revealed significant vertical and diel variations of lake variables in spite of a shallow water depth (2.5 m) caused by the intense surface heating from solar irradiance (~800 W m−2) and accentuated by the lake's high turbidity (16–32 ftu). Late afternoon land-lake breeze (~5–7 m s−1) regularly breaks daytime thermal stratification, and convective cooling at night maintains isothermal condition until dawn of the next day. The stratified condition demonstrated a wind-driven, density-induced 2-layer current pattern with a windward moving epilimnion (~4 folds faster) and a compensating hypolimnetic flow in the general lake circulation direction. Laguna Lake was observed to have a dominating diel cycle but also undergoes significant seasonal limnological variations brought primarily by climate, hydrology, and its interaction with the adjacent sea. Significantly correlated variations of pH, chlorophyll-a and DO in the dry season were indicative of the higher biological activity associated with the intrusion of polluted waters from Metro Manila. The non-occurrence of thermal over-turn was observed to be regularly followed by bottom hypoxic conditions (2–4 mg L−1), indicative of the eutrophic condition of the lake and the importance of diel wind-induced mixing in the bottom supply of DO. Laguna Lake was found to be predominantly net heterotrophic (GPP:R < 1, NEP < 0).
Eugene C. Herrera; Kazuo Nadaoka. Temporal dynamics and drivers of lake ecosystem metabolism using high resolution observations in a shallow, tropical, eutrophic lake (Laguna Lake, Philippines). Journal of Great Lakes Research 2021, 47, 997 -1020.
AMA StyleEugene C. Herrera, Kazuo Nadaoka. Temporal dynamics and drivers of lake ecosystem metabolism using high resolution observations in a shallow, tropical, eutrophic lake (Laguna Lake, Philippines). Journal of Great Lakes Research. 2021; 47 (4):997-1020.
Chicago/Turabian StyleEugene C. Herrera; Kazuo Nadaoka. 2021. "Temporal dynamics and drivers of lake ecosystem metabolism using high resolution observations in a shallow, tropical, eutrophic lake (Laguna Lake, Philippines)." Journal of Great Lakes Research 47, no. 4: 997-1020.
This study assessed the estuarine-scale dynamics of mixed seagrass beds in Bolinao and Anda coastal areas in the Philippines, where seagrass beds have declined primarily due to eutrophication-induced degradation of light environment caused by unregulated mariculture activities in the adjacent areas. A seagrass model, driven by a coupled hydrodynamic-biogeochemical model, was developed and applied to the two-dominant species in the area – Thalassia hemprichii and Enhalus acoroides, and validated using observed spatial seagrass shoot density. The results showed the degradation of light environment in the seagrass beds, especially near mariculture areas, due to advective fluxes of water with high phytoplankton biomass and high nutrients from fish farms. The seagrass model driven by the reproduced water quality showed high reproducibility of seagrass above-ground biomass distribution of the two co-existing species, with R2 values of 0.78 and 0.60 for T. hemprichii and E. acoroides, respectively. Scenario analysis was conducted to examine the effectiveness of individual- and inter-municipality mariculture management (e.g., regulating fish feed input) in improving the light environment and facilitating the recovery of seagrasses. Results showed that the light environment could be significantly enhanced by an inter-municipality scheme compared to individual efforts of Bolinao and Anda municipalities, since their waters are interconnected through hydrodynamics. In conjunction with the improvement of light conditions, the recovery in seagrass abundance is most significant under the cooperative management scheme, thus highlighting its effectiveness.
Masaya Yoshikai; Takashi Nakamura; Yoshiyuki Tanaka; Masahiro Nakaoka; Atsushi Watanabe; Eugene C. Herrera; Takumi Tsuchiya; Toshihiro Miyajima; Maria Lourdes San Diego-McGlone; Miguel D. Fortes; Ariel C. Blanco; Ayin M. Tamondong; Kazuo Nadaoka. Modeling seagrass bed dynamics under environmental impacts of intensive mariculture activities in Bolinao and Anda, the Philippines. Estuarine, Coastal and Shelf Science 2020, 250, 107152 .
AMA StyleMasaya Yoshikai, Takashi Nakamura, Yoshiyuki Tanaka, Masahiro Nakaoka, Atsushi Watanabe, Eugene C. Herrera, Takumi Tsuchiya, Toshihiro Miyajima, Maria Lourdes San Diego-McGlone, Miguel D. Fortes, Ariel C. Blanco, Ayin M. Tamondong, Kazuo Nadaoka. Modeling seagrass bed dynamics under environmental impacts of intensive mariculture activities in Bolinao and Anda, the Philippines. Estuarine, Coastal and Shelf Science. 2020; 250 ():107152.
Chicago/Turabian StyleMasaya Yoshikai; Takashi Nakamura; Yoshiyuki Tanaka; Masahiro Nakaoka; Atsushi Watanabe; Eugene C. Herrera; Takumi Tsuchiya; Toshihiro Miyajima; Maria Lourdes San Diego-McGlone; Miguel D. Fortes; Ariel C. Blanco; Ayin M. Tamondong; Kazuo Nadaoka. 2020. "Modeling seagrass bed dynamics under environmental impacts of intensive mariculture activities in Bolinao and Anda, the Philippines." Estuarine, Coastal and Shelf Science 250, no. : 107152.
Benthic habitats are structurally complex and ecologically diverse ecosystems that are severely vulnerable to human stressors. Consequently, marine habitats must be mapped and monitored to provide the information necessary to understand ecological processes and lead management actions. In this study, we propose a semiautomated framework for the detection and mapping of benthic habitats and seagrass species using convolutional neural networks (CNNs). Benthic habitat field data from a geo-located towed camera and high-resolution satellite images were integrated to evaluate the proposed framework. Features extracted from pre-trained CNNs and a “bagging of features” (BOF) algorithm was used for benthic habitat and seagrass species detection. Furthermore, the resultant correctly detected images were used as ground truth samples for training and validating CNNs with simple architectures. These CNNs were evaluated for their accuracy in benthic habitat and seagrass species mapping using high-resolution satellite images. Two study areas, Shiraho and Fukido (located on Ishigaki Island, Japan), were used to evaluate the proposed model because seven benthic habitats were classified in the Shiraho area and four seagrass species were mapped in Fukido cove. Analysis showed that the overall accuracy of benthic habitat detection in Shiraho and seagrass species detection in Fukido was 91.5% (7 classes) and 90.4% (4 species), respectively, while the overall accuracy of benthic habitat and seagrass mapping in Shiraho and Fukido was 89.9% and 91.2%, respectively.
Hassan Mohamed; Kazuo Nadaoka; Takashi Nakamura. Semiautomated Mapping of Benthic Habitats and Seagrass Species Using a Convolutional Neural Network Framework in Shallow Water Environments. Remote Sensing 2020, 12, 4002 .
AMA StyleHassan Mohamed, Kazuo Nadaoka, Takashi Nakamura. Semiautomated Mapping of Benthic Habitats and Seagrass Species Using a Convolutional Neural Network Framework in Shallow Water Environments. Remote Sensing. 2020; 12 (23):4002.
Chicago/Turabian StyleHassan Mohamed; Kazuo Nadaoka; Takashi Nakamura. 2020. "Semiautomated Mapping of Benthic Habitats and Seagrass Species Using a Convolutional Neural Network Framework in Shallow Water Environments." Remote Sensing 12, no. 23: 4002.
The accurate classification and 3D mapping of benthic habitats in coastal ecosystems are vital for developing management strategies for these valuable shallow water environments. However, both automatic and semiautomatic approaches for deriving ecologically significant information from a towed video camera system are quite limited. In the current study, we demonstrate a semiautomated framework for high-resolution benthic habitat classification and 3D mapping using Structure from Motion and Multi View Stereo (SfM-MVS) algorithms and automated machine learning classifiers. The semiautomatic classification of benthic habitats was performed using several attributes extracted automatically from labeled examples by a human annotator using raw towed video camera image data. The Bagging of Features (BOF), Hue Saturation Value (HSV), and Gray Level Co-occurrence Matrix (GLCM) methods were used to extract these attributes from 3000 images. Three machine learning classifiers (k-nearest neighbor (k-NN), support vector machine (SVM), and bagging (BAG)) were trained by using these attributes, and their outputs were assembled by the fuzzy majority voting (FMV) algorithm. The correctly classified benthic habitat images were then geo-referenced using a differential global positioning system (DGPS). Finally, SfM-MVS techniques used the resulting classified geo-referenced images to produce high spatial resolution digital terrain models and orthophoto mosaics for each category. The framework was tested for the identification and 3D mapping of seven habitats in a portion of the Shiraho area in Japan. These seven habitats were corals (Acropora and Porites), blue corals (H. coerulea), brown algae, blue algae, soft sand, hard sediments (pebble, cobble, and boulders), and seagrass. Using the FMV algorithm, we achieved an overall accuracy of 93.5% in the semiautomatic classification of the seven habitats.
Hassan Mohamed; Kazuo Nadaoka; Takashi Nakamura. Towards Benthic Habitat 3D Mapping Using Machine Learning Algorithms and Structures from Motion Photogrammetry. Remote Sensing 2020, 12, 127 .
AMA StyleHassan Mohamed, Kazuo Nadaoka, Takashi Nakamura. Towards Benthic Habitat 3D Mapping Using Machine Learning Algorithms and Structures from Motion Photogrammetry. Remote Sensing. 2020; 12 (1):127.
Chicago/Turabian StyleHassan Mohamed; Kazuo Nadaoka; Takashi Nakamura. 2020. "Towards Benthic Habitat 3D Mapping Using Machine Learning Algorithms and Structures from Motion Photogrammetry." Remote Sensing 12, no. 1: 127.
Benthic habitat monitoring is essential for many applications involving biodiversity, marine resource management, and the estimation of variations over temporal and spatial scales. Nevertheless, both automatic and semi-automatic analytical methods for deriving ecologically significant information from towed camera images are still limited. This study proposes a methodology that enables a high-resolution towed camera with a Global Navigation Satellite System (GNSS) to adaptively monitor and map benthic habitats. First, the towed camera finishes a pre-programmed initial survey to collect benthic habitat videos, which can then be converted to geo-located benthic habitat images. Second, an expert labels a number of benthic habitat images to class habitats manually. Third, attributes for categorizing these images are extracted automatically using the Bag of Features (BOF) algorithm. Fourth, benthic cover categories are detected automatically using Weighted Majority Voting (WMV) ensembles for Support Vector Machines (SVM), K-Nearest Neighbor (K-NN), and Bagging (BAG) classifiers. Fifth, WMV-trained ensembles can be used for categorizing more benthic cover images automatically. Finally, correctly categorized geo-located images can provide ground truth samples for benthic cover mapping using high-resolution satellite imagery. The proposed methodology was tested over Shiraho, Ishigaki Island, Japan, a heterogeneous coastal area. The WMV ensemble exhibited 89% overall accuracy for categorizing corals, sediments, seagrass, and algae species. Furthermore, the same WMV ensemble produced a benthic cover map using a Quickbird satellite image with 92.7% overall accuracy.
Hassan Mohamed; Kazuo Nadaoka; Takashi Nakamura. Assessment of Machine Learning Algorithms for Automatic Benthic Cover Monitoring and Mapping Using Towed Underwater Video Camera and High-Resolution Satellite Images. Remote Sensing 2018, 10, 773 .
AMA StyleHassan Mohamed, Kazuo Nadaoka, Takashi Nakamura. Assessment of Machine Learning Algorithms for Automatic Benthic Cover Monitoring and Mapping Using Towed Underwater Video Camera and High-Resolution Satellite Images. Remote Sensing. 2018; 10 (5):773.
Chicago/Turabian StyleHassan Mohamed; Kazuo Nadaoka; Takashi Nakamura. 2018. "Assessment of Machine Learning Algorithms for Automatic Benthic Cover Monitoring and Mapping Using Towed Underwater Video Camera and High-Resolution Satellite Images." Remote Sensing 10, no. 5: 773.
To predict coral responses to future environmental changes at the reef scale, the coral polyp model (Nakamura et al. in Coral Reefs 32:779–794, 2013), which reconstructs coral responses to ocean acidification, flow conditions and other factors, was incorporated into a reef-scale three-dimensional hydrodynamic-biogeochemical model. This coupled reef-scale model was compared to observations from the Shiraho fringing reef, Ishigaki Island, Japan, where the model accurately reconstructed spatiotemporal variation in reef hydrodynamic and geochemical parameters. The simulated coral calcification rate exhibited high spatial variation, with lower calcification rates in the nearshore and stagnant water areas due to isolation of the inner reef at low tide, and higher rates on the offshore side of the inner reef flat. When water is stagnant, bottom shear stress is low at night and thus oxygen diffusion rate from ambient water to the inside of the coral polyp limits respiration rate. Thus, calcification decreases because of the link between respiration and calcification. A scenario analysis was conducted using the reef-scale model with several pCO2 and sea-level conditions based on IPCC (Climate change 2013: the physical science basis. Contribution of working group I to the fifth assessment report of the intergovernmental panel on climate change, Cambridge University Press, Cambridge, 2013) scenarios. The simulation indicated that the coral calcification rate decreases with increasing pCO2. On the other hand, sea-level rise increases the calcification rate, particularly in the nearshore and the areas where water is stagnant at low tide under present conditions, as mass exchange, especially oxygen exchange at night, is enhanced between the corals and their ambient seawater due to the reduced stagnant period. When both pCO2 increase and sea-level rise occur concurrently, the calcification rate generally decreases due to the effects of ocean acidification. However, the calcification rate in some inner-reef areas will increase because the positive effects of sea-level rise offset the negative effects of ocean acidification, and total calcification rate will be positive only under the best-case scenario (RCP 2.6).
Takashi Nakamura; Kazuo Nadaoka; Atsushi Watanabe; Takahiro Yamamoto; Toshihiro Miyajima; Ariel C. Blanco. Reef-scale modeling of coral calcification responses to ocean acidification and sea-level rise. Coral Reefs 2017, 37, 37 -53.
AMA StyleTakashi Nakamura, Kazuo Nadaoka, Atsushi Watanabe, Takahiro Yamamoto, Toshihiro Miyajima, Ariel C. Blanco. Reef-scale modeling of coral calcification responses to ocean acidification and sea-level rise. Coral Reefs. 2017; 37 (1):37-53.
Chicago/Turabian StyleTakashi Nakamura; Kazuo Nadaoka; Atsushi Watanabe; Takahiro Yamamoto; Toshihiro Miyajima; Ariel C. Blanco. 2017. "Reef-scale modeling of coral calcification responses to ocean acidification and sea-level rise." Coral Reefs 37, no. 1: 37-53.
While widely known for their destructive power, typhoon events can also bring benefit to coral reef ecosystems through typhoon-induced cooling which can mitigate against thermally stressful conditions causing coral bleaching. Sensor deployments in Sekisei Lagoon, Japan’s largest coral reef area, during the summer months of 2013, 2014, and 2015 were able to capture local hydrodynamic features of numerous typhoon passages. In particular, typhoons 2015-13 and 2015-15 featured steep drops in near-bottom temperature of 5 °C or more in the north and south sides of Sekisei Lagoon, respectively, indicating local cooling patterns which appeared to depend on the track and intensity of the passing typhoon. This was further investigated using Regional Ocean Modeling System (ROMS) numerical simulations conducted for the summer of 2015. The modeling results showed a cooling trend to the north of the Yaeyama Islands during the passage of typhoon 2015-13, and a cooling trend that moved clockwise from north to south of the islands during the passage of typhoon 2015-15. These local cooling events may have been initiated by the Yaeyama Islands acting as an obstacle to a strong typhoon-generated flow which was modulated and led to prominent cooling of waters on the leeward sides. These lower temperature waters from offshore may then be transported to the shallower inner parts of the lagoon area, which may partly be due to density-driven currents generated by the offshore-inner area temperature difference.
Lawrence Patrick Cases Bernardo; Kazuo Nadaoka; Takashi Nakamura; Atsushi Watanabe. Island-enhanced cooling mechanism in typhoon events revealed by field observations and numerical simulations for a coral reef area, Sekisei Lagoon, Japan. Ocean Dynamics 2017, 67, 1369 -1384.
AMA StyleLawrence Patrick Cases Bernardo, Kazuo Nadaoka, Takashi Nakamura, Atsushi Watanabe. Island-enhanced cooling mechanism in typhoon events revealed by field observations and numerical simulations for a coral reef area, Sekisei Lagoon, Japan. Ocean Dynamics. 2017; 67 (11):1369-1384.
Chicago/Turabian StyleLawrence Patrick Cases Bernardo; Kazuo Nadaoka; Takashi Nakamura; Atsushi Watanabe. 2017. "Island-enhanced cooling mechanism in typhoon events revealed by field observations and numerical simulations for a coral reef area, Sekisei Lagoon, Japan." Ocean Dynamics 67, no. 11: 1369-1384.
The establishment of marine protected areas (MPAs) can often lead to environmental differences between MPAs and fishing zones. To determine the effects on marine dispersal of environmental dissimilarity between an MPA and fishing zone, we examined the abundance and recruitment patterns of two anemonefishes (Amphiprion frenatus and A. perideraion) that inhabit sea anemones in different management zones (i.e., an MPA and two fishing zones) by performing a field survey and a genetic parentage analysis. We found lower levels of abundance per anemone in the MPA compared to the fishing zones for both species (n = 1,525 anemones, p = .032). The parentage analysis also showed that lower numbers of fishes were recruited from the fishing zones and outside of the study area into each anemone in the MPA than into each anemone in the fishing zones (n = 1,525 anemones, p < .017). However, the number of self‐recruit production per female did not differ between the MPA and fishing zones (n = 384 females, p = .516). Because the ocean currents around the study site were unlikely to cause a lower settlement intensity of larvae in the MPA, the ocean circulation was not considered crucial to the observed abundance and recruitment patterns. Instead, stronger top‐down control and/or a lower density of host anemones in the MPA were potential factors for such patterns. Our results highlight the importance of dissimilarity in a marine environment as a factor that affects connectivity.
Masaaki Sato; Kentaro Honda; Wilfredo H. Uy; Darwin I. Baslot; Tom G. Genovia; Yohei Nakamura; Lawrence Patrick Cases Bernardo; Hiroyuki Kurokochi; Allyn Duvin S. Pantallano; Chunlan Lian; Kazuo Nadaoka; Masahiro Nakaoka. Marine protected area restricts demographic connectivity: Dissimilarity in a marine environment can function as a biological barrier. Ecology and Evolution 2017, 7, 7859 -7871.
AMA StyleMasaaki Sato, Kentaro Honda, Wilfredo H. Uy, Darwin I. Baslot, Tom G. Genovia, Yohei Nakamura, Lawrence Patrick Cases Bernardo, Hiroyuki Kurokochi, Allyn Duvin S. Pantallano, Chunlan Lian, Kazuo Nadaoka, Masahiro Nakaoka. Marine protected area restricts demographic connectivity: Dissimilarity in a marine environment can function as a biological barrier. Ecology and Evolution. 2017; 7 (19):7859-7871.
Chicago/Turabian StyleMasaaki Sato; Kentaro Honda; Wilfredo H. Uy; Darwin I. Baslot; Tom G. Genovia; Yohei Nakamura; Lawrence Patrick Cases Bernardo; Hiroyuki Kurokochi; Allyn Duvin S. Pantallano; Chunlan Lian; Kazuo Nadaoka; Masahiro Nakaoka. 2017. "Marine protected area restricts demographic connectivity: Dissimilarity in a marine environment can function as a biological barrier." Ecology and Evolution 7, no. 19: 7859-7871.
Tsunami overtopping a caisson breakwater is reproduced by a numerical model to evaluate the stability of armor units covering the harbor-side of the rubble mound. This model solves the overflow jet above the water surface and the harbor-side flow field separately to avoid entrainment of excessive bubbles. Using this model, the applicability of the Isbash formula for the stability of armor stones and concrete blocks against tsunami overflow is examined. The relationship between the Isbash number and the degree of movement of armor stones is clarified. In the case of concrete blocks, the Isbash number of the stability limitation varied with the thickness of the overflow jet. The Isbash formula by CERC tends to overestimate the effect of slope angle, when applied to concrete blocks. A stability prediction method for armor blocks based on fluid forces acting on each armor block is presented as well.
J. Mitsui; A. Matsumoto; M. Hanzawa; K. Nadaoka. Numerical Analysis on Tsunamis Overtopping Caisson Breakwaters and the Stability of Armor Units. Coastal Structures and Solutions to Coastal Disasters 2015 2017, 1 .
AMA StyleJ. Mitsui, A. Matsumoto, M. Hanzawa, K. Nadaoka. Numerical Analysis on Tsunamis Overtopping Caisson Breakwaters and the Stability of Armor Units. Coastal Structures and Solutions to Coastal Disasters 2015. 2017; ():1.
Chicago/Turabian StyleJ. Mitsui; A. Matsumoto; M. Hanzawa; K. Nadaoka. 2017. "Numerical Analysis on Tsunamis Overtopping Caisson Breakwaters and the Stability of Armor Units." Coastal Structures and Solutions to Coastal Disasters 2015 , no. : 1.
Mahmoud Sharaan; Abdelazim Negm; Moheb Iskander; Kazuo Nadaoka. Questionnaire-based assessment of Mediterranean fishing ports, Nile Delta, Egypt. Marine Policy 2017, 81, 98 -108.
AMA StyleMahmoud Sharaan, Abdelazim Negm, Moheb Iskander, Kazuo Nadaoka. Questionnaire-based assessment of Mediterranean fishing ports, Nile Delta, Egypt. Marine Policy. 2017; 81 ():98-108.
Chicago/Turabian StyleMahmoud Sharaan; Abdelazim Negm; Moheb Iskander; Kazuo Nadaoka. 2017. "Questionnaire-based assessment of Mediterranean fishing ports, Nile Delta, Egypt." Marine Policy 81, no. : 98-108.
The Philippines has lost nearly 70% of its natural mangrove cover since the early 1900s. As a result, large investments have been made to restore mangrove forests and the many ecosystem services that they provide. Most of these restoration efforts have been through outplanting of Rhizophora sp. seedlings, many of which have failed because the proper hydrological and ecological conditions were not properly assessed. Other afforestation projects involved planting seedlings in inappropriate places (e.g., seagrass beds, mudflats) that resulted in replacing one valuable ecosystem with another. The aim of this research was to investigate the growth of 3-, 9-, and 21-year-old afforested stands of Rhizophora spp. mangrove forest. We also investigated the impact of these plantations on local seagrass beds. The total aboveground biomass was 42.6, 74.4, and 111.7 Mg ha−1 for the 3-, 9-, and 21-year-old mangrove stands, respectively. Seagrass bed cover decreased under the closed canopy of the mangrove due to reduced photosynthetically active radiation and competition for growing space. This study shows that mangroves can grow to some extent on seagrass beds, though mangrove planting in these areas could eventually lead to seagrass loss. Thus, mangroves should not be planted in areas that are naturally occupied by other ecologically important ecosystems. The purpose of mangrove restoration should be clear and efforts should be focused on formerly deforested or degraded areas. Additional studies are needed from different locations to understand how mangrove planting in seagrass beds impacts growth performance and ecological functions of the latter ecosystem.
Sahadev Sharma; Kazuo Nadaoka; Masahiro Nakaoka; Wilfredo H. Uy; Richard A. MacKenzie; Daniel A. Friess; Miguel D. Fortes. Growth performance and structure of a mangrove afforestation project on a former seagrass bed, Mindanao Island, Philippines. Hydrobiologia 2017, 803, 359 -371.
AMA StyleSahadev Sharma, Kazuo Nadaoka, Masahiro Nakaoka, Wilfredo H. Uy, Richard A. MacKenzie, Daniel A. Friess, Miguel D. Fortes. Growth performance and structure of a mangrove afforestation project on a former seagrass bed, Mindanao Island, Philippines. Hydrobiologia. 2017; 803 (1):359-371.
Chicago/Turabian StyleSahadev Sharma; Kazuo Nadaoka; Masahiro Nakaoka; Wilfredo H. Uy; Richard A. MacKenzie; Daniel A. Friess; Miguel D. Fortes. 2017. "Growth performance and structure of a mangrove afforestation project on a former seagrass bed, Mindanao Island, Philippines." Hydrobiologia 803, no. 1: 359-371.
In this study, two hydrologic models, the Gridded Surface Subsurface Hydrologic Analysis (GSSHA) and the Soil and Water Assessment Tool (SWAT), were applied to predict stream flow and suspended sediment concentration (SSC) in a small agricultural watershed in Ishigaki Island, Japan, in which the typical time scale of flood event was several hours. The performances of these two models were compared in order to select the right model for the study watershed. Both models were calibrated and validated against hourly stream flow and SSC for half-month periods of 15 to 31 May 2011 and 17 March to 7 April 2013, respectively. The results showed that both models successfully estimated hourly stream flow and SSC in a satisfactory way. For the short-term simulations, the GSSHA model performed slightly better in simulating stream flow as compared to SWAT during both calibration and validation periods. GSSHA only gave better accuracy when predicting SSC during calibration, while SWAT performed slightly better during validation. For long-term simulations, both models yielded comparable results for long-term stream flow and SSC with acceptable agreement. However, SWAT predicted the overall variation of long-term SSC better than GSSHA.
Ratino Sith; Kazuo Nadaoka. Comparison of SWAT and GSSHA for High Time Resolution Prediction of Stream Flow and Sediment Concentration in a Small Agricultural Watershed. Hydrology 2017, 4, 27 .
AMA StyleRatino Sith, Kazuo Nadaoka. Comparison of SWAT and GSSHA for High Time Resolution Prediction of Stream Flow and Sediment Concentration in a Small Agricultural Watershed. Hydrology. 2017; 4 (2):27.
Chicago/Turabian StyleRatino Sith; Kazuo Nadaoka. 2017. "Comparison of SWAT and GSSHA for High Time Resolution Prediction of Stream Flow and Sediment Concentration in a Small Agricultural Watershed." Hydrology 4, no. 2: 27.
This paper analyzes the temporal variability in sediment yield in a small agricultural watershed located in the southwest portion of Japan. The relationships between the rainfall, runoff, and sediment variables were analyzed, and the suspended sediment concentration–discharge hysteresis was used to interpret the mechanisms of sediment transport. A total of 227 flood events were derived from long–term high resolution discharge and sediment data that had been collected over the period of 2000–2015. Long–term analyses showed that there are highly variable hydrological and sediment responses on inter–annual, annual, seasonal scales. Sediment was strongly transported in the period of August–October, when the watershed was hydrologically and sedimentologically most active, followed by the February–April, May–July, and November–January periods. The sediment concentration for most flood events was relatively high, frequently exceeding 200 mg.L−1 and reaching as much as 1967 mg.L−1. The rainfall, runoff, and sediment variables showed significant correlations with each other. However, antecedent rainfall strongly influenced the efficiency of runoff generation, which further affected the sediment transport. Four types of hysteresis were observed: clockwise (48%), counter–clockwise (16%), figure–eight (25%), and complex (11%). The results confirmed the complexity and heterogeneity of both the hydrological and sedimentological responses in the studied watershed. Even though the analyses revealed the efficiency of the soil erosion–reduction schemes that had been implemented in the studied watershed, the red soil outflow is still relatively high. Therefore, additional measures (e.g., slope gradient modification, grass strips, and cover crop planting prior to summer sugarcane planting) are necessary to reduce soil erosion and sediment discharge.
Ratino Sith; Takahiro Yamamoto; Atsushi Watanabe; Takashi Nakamura; Kazuo Nadaoka. Analysis of Red Soil Sediment Yield in a Small Agricultural Watershed in Ishigaki Island, Japan, Using Long–Term and High Resolution Monitoring Data. Environmental Processes 2017, 4, 333 -354.
AMA StyleRatino Sith, Takahiro Yamamoto, Atsushi Watanabe, Takashi Nakamura, Kazuo Nadaoka. Analysis of Red Soil Sediment Yield in a Small Agricultural Watershed in Ishigaki Island, Japan, Using Long–Term and High Resolution Monitoring Data. Environmental Processes. 2017; 4 (2):333-354.
Chicago/Turabian StyleRatino Sith; Takahiro Yamamoto; Atsushi Watanabe; Takashi Nakamura; Kazuo Nadaoka. 2017. "Analysis of Red Soil Sediment Yield in a Small Agricultural Watershed in Ishigaki Island, Japan, Using Long–Term and High Resolution Monitoring Data." Environmental Processes 4, no. 2: 333-354.
Seagrasses are marine angiosperms and play an essential ecological role in coastal ecosystems; however, seagrass meadows are threatened locally by anthropogenic disturbances. Understanding the dispersal patterns of seagrasses is essential for appropriate ecosystem management and establishment of marine protected areas (MPAs) in coastal ecosystems. In the Guimaras Strait in the Philippines, Banate (BAN) has been established as an MPA. However, there is a lack of information on the genetic diversity of seagrasses in BAN and the surrounding areas. In the present study, population genetics analysis of Enhalus acoroides was performed by using polymorphic microsatellite markers, for the estimation of genetic diversity, differentiation, and migration patterns of seagrasses within the regional geographical scale (~200 km) around the Guimaras Strait. The results showed that the genetic diversity of BAN is extremely low, although the Guimaras Strait is located in the tropical central habitat. Guimaras Island geographically divides the populations of E. acoroides into south and north. However, the genetic structure did not show any relationship between the geographical location and distance. The floating, buoyant fruits of E. acoroides may play a role in their long-distance dispersal; however, such dispersal is not frequent. Almost all of the seeds and fruits are derived from self-recruitment in the natal meadow. This study suggests that E. acoroides populations possess a weak genetic connectivity, and that the persistence of the meadow is threatened due to the low genetic diversity and high degree of population isolation in BAN. To maintain and enhance the genetic diversity of seagrasses within the MPA, the seagrass meadows in the surrounding areas should also be conserved.
Yuichi Nakajima; Yu Matsuki; Dan M. Arriesgado; Wilfredo L. Campos; Kazuo Nadaoka; Chunlan Lian. Population genetics information for the regional conservation of a tropical seagrass, Enhalus acoroides, around the Guimaras Strait, Philippines. Conservation Genetics 2017, 18, 789 -798.
AMA StyleYuichi Nakajima, Yu Matsuki, Dan M. Arriesgado, Wilfredo L. Campos, Kazuo Nadaoka, Chunlan Lian. Population genetics information for the regional conservation of a tropical seagrass, Enhalus acoroides, around the Guimaras Strait, Philippines. Conservation Genetics. 2017; 18 (4):789-798.
Chicago/Turabian StyleYuichi Nakajima; Yu Matsuki; Dan M. Arriesgado; Wilfredo L. Campos; Kazuo Nadaoka; Chunlan Lian. 2017. "Population genetics information for the regional conservation of a tropical seagrass, Enhalus acoroides, around the Guimaras Strait, Philippines." Conservation Genetics 18, no. 4: 789-798.
The land based sources of pollution are major threat to the reef ecosystems; therefore, it is important to ascertain the temporal and spatial change pattern of coral cover at local scale to understand the causal links between reef degradation and ground discharge impact with changing land use practices. The land use change dynamics and its impacts on surrounding reefs were investigated using aerial photographs of 1977, 1994 and 2005 of Kuroshima Island, Japan by integrating remote sensing and GIS (Geographic Information System) approach. And the impact of groundwater associated nutrient discharge was estimated using 222Rn(radon) as an SGD (submarine groundwater discharge) tracer. Findings indicate that the land used for grazing has increased (597%) during the study period and most of this increase has been at the expense of forest and shrub land. The landscape development intensity (LDI) index, was used to evaluate the impact of land driven activities on coral assemblages. LDI results infer that north-eastern watershed (2.84), south-eastern watershed (3.02) and north-western watersheds (2.75 to 2.88) are most critical watersheds with higher LDI in comparison to other watersheds due to the enormous increase in pasture land. The benthic cover change analysis indicates the overgrowth of seagrass (99.5%) and microalgal productivity (99.6%) especially in the northern, western and southeastern part of the Island during 1977 to 2005. The groundwater discharge with high concentration of land-derived nutrients was observed as the main source for the reduction in coral cover around Kuroshima island.
Ankita P. Dadhich; Kazuo Nadaoka; Y. Motomura; A. Watanabe. Potential impacts of land use change dynamics and submarine groundwater discharge on fringing reefs of Kuroshima Island, Japan. Journal of Coastal Conservation 2017, 21, 245 -254.
AMA StyleAnkita P. Dadhich, Kazuo Nadaoka, Y. Motomura, A. Watanabe. Potential impacts of land use change dynamics and submarine groundwater discharge on fringing reefs of Kuroshima Island, Japan. Journal of Coastal Conservation. 2017; 21 (1):245-254.
Chicago/Turabian StyleAnkita P. Dadhich; Kazuo Nadaoka; Y. Motomura; A. Watanabe. 2017. "Potential impacts of land use change dynamics and submarine groundwater discharge on fringing reefs of Kuroshima Island, Japan." Journal of Coastal Conservation 21, no. 1: 245-254.
Hassan Mohamed; Abdelazim Negm; Mahmoud Salah; Kazuo Nadaoka; Mohamed Zahran. Assessment of proposed approaches for bathymetry calculations using multispectral satellite images in shallow coastal/lake areas: a comparison of five models. Arabian Journal of Geosciences 2017, 10, 1 .
AMA StyleHassan Mohamed, Abdelazim Negm, Mahmoud Salah, Kazuo Nadaoka, Mohamed Zahran. Assessment of proposed approaches for bathymetry calculations using multispectral satellite images in shallow coastal/lake areas: a comparison of five models. Arabian Journal of Geosciences. 2017; 10 (2):1.
Chicago/Turabian StyleHassan Mohamed; Abdelazim Negm; Mahmoud Salah; Kazuo Nadaoka; Mohamed Zahran. 2017. "Assessment of proposed approaches for bathymetry calculations using multispectral satellite images in shallow coastal/lake areas: a comparison of five models." Arabian Journal of Geosciences 10, no. 2: 1.
Danet Hak; Kazuo Nadaoka; Vo Le Phu. Socioeconomic Conditions and Perceptions of Environmental Risks in the Mekong Delta, Vietnam. Coastal Management 2016, 44, 585 -605.
AMA StyleDanet Hak, Kazuo Nadaoka, Vo Le Phu. Socioeconomic Conditions and Perceptions of Environmental Risks in the Mekong Delta, Vietnam. Coastal Management. 2016; 44 (6):585-605.
Chicago/Turabian StyleDanet Hak; Kazuo Nadaoka; Vo Le Phu. 2016. "Socioeconomic Conditions and Perceptions of Environmental Risks in the Mekong Delta, Vietnam." Coastal Management 44, no. 6: 585-605.
This study examined if, and how, comanagement is effective in controlling aquaculture industry in the municipalities of Anda and Bolinao in the province of Pangasinan, in the Philippines, the locations of two major production areas of milkfish (Chanos chanos) in the country. Institutional and community analyses conducted in these study sites revealed a unique hierarchy of resource users, as well as unique social and economic problems in aquaculture, distinct from those of capture fishery. It was also indicated that comanagement is seen as a solution for essential practices to be enforced practically and sustainably for the management of this industry. To improve aquaculture governance, it is desired that the comanagement scheme shall include not only the governments and fishers but also business operators who often have large capital and a high degree of power.
Aoi Sugimoto; Maria Lourdes San Diego-McGlone; Francisco Paciencia; Shielameh P. Milan; Elizabeth T. Tomas; Carolina C. Ramírez; Annabelle Echavez; Jessem Gabatin; Miguel D. Fortes; Kazuo Nadaoka. Comanagement for aquaculture: Suggestions from a comparative study between two major production areas of milkfish in the Philippines. Journal of Applied Aquaculture 2016, 28, 298 -313.
AMA StyleAoi Sugimoto, Maria Lourdes San Diego-McGlone, Francisco Paciencia, Shielameh P. Milan, Elizabeth T. Tomas, Carolina C. Ramírez, Annabelle Echavez, Jessem Gabatin, Miguel D. Fortes, Kazuo Nadaoka. Comanagement for aquaculture: Suggestions from a comparative study between two major production areas of milkfish in the Philippines. Journal of Applied Aquaculture. 2016; 28 (4):298-313.
Chicago/Turabian StyleAoi Sugimoto; Maria Lourdes San Diego-McGlone; Francisco Paciencia; Shielameh P. Milan; Elizabeth T. Tomas; Carolina C. Ramírez; Annabelle Echavez; Jessem Gabatin; Miguel D. Fortes; Kazuo Nadaoka. 2016. "Comanagement for aquaculture: Suggestions from a comparative study between two major production areas of milkfish in the Philippines." Journal of Applied Aquaculture 28, no. 4: 298-313.
Fisheries are considered one of the important sources of national income in Egypt. The fishery operates vast tracts of more than 13 million acres and varies according to the nature of these sources, such as Mediterranean Sea, Red Sea, lakes and the Nile River. There are 21 Egyptian fishing ports and marinas located on both the Mediterranean coasts and lakes. Only five of these ports have minimum requirements of infrastructure and facilities for accommodating catches, fishing boats, and equipment. This study aims to present the current environmental, planning, and facilities issues for four of the existing artificial and natural Egyptian fishing ports that are located on the Mediterranean Sea in terms of challenges and opportunities. The data are collected from different sources such as the annual reports of the Egyptian General Authority for Fish Resources Development, discussion, and personal interviews with the main stakeholders, and through field survey and visual observation. The results show that the investigated fishing ports are suffering from degradation of catch rates, increase of pollution levels, master planning issues, sedimentation issues, and deterioration of the basic infrastructure as well as a great variance of available facilities. The results spotlight the current conditions of fishing ports in Egypt. In addition, the need for further research to investigate the possibility of improving the offered facilities and the port efficiency towards transfer of Egyptian fishing ports into sustainable and greener ports is presented.
Mahmoud Sharaan; Abdelazim Negm; Moheb Iskander; Kazuo Nadaoka. Egyptian Fishing Ports Challenges and Opportunities Case Study: Mediterranean Sea Ports. Ports 2016 2016, 540 -549.
AMA StyleMahmoud Sharaan, Abdelazim Negm, Moheb Iskander, Kazuo Nadaoka. Egyptian Fishing Ports Challenges and Opportunities Case Study: Mediterranean Sea Ports. Ports 2016. 2016; ():540-549.
Chicago/Turabian StyleMahmoud Sharaan; Abdelazim Negm; Moheb Iskander; Kazuo Nadaoka. 2016. "Egyptian Fishing Ports Challenges and Opportunities Case Study: Mediterranean Sea Ports." Ports 2016 , no. : 540-549.
Multi-purpose reservoir development have been always a big challenge for the management of water resources. This paper describes an integrated approach for investigating catchment hydrology in the development of a hydropower and a canal irrigation system based on model analyses. The investigation aims to adequately determine an optimal domestic and irrigation water resources allocation scheme based on an assessment of the reservoir water balance and capacity for hydropower. The soil and water assessment tool (SWAT) which characterizes basin hydrology and the water management and planning model MODSIM which provides a decision support system for water allocation optimization, were used in this study. The integrated approach was applied to Prek Te River basin in Cambodia. The water demand aspect was examined based on domestic water use, irrigation water, environmental flow, and water losses. An operational rule curve was developed for hydropower operation with respect to a power potential of 13 MW. Hydrologic modeling revealed 90 % dependable water of about 2.7 m3/s during the dry season and 214.3 m3/s during the wet season, indicative of a wet-season dependent reservoir for storage. Results from the 26-years simulation period also showed that diversions for domestic water and irrigation water supply were 92.3 % dependable for a 13 MW capacity hydropower development. The integrated approach was shown to be a valuable decision support tool for water resources management with the determination of an optimum policy for multi-purpose reservoir operation based on available basin water supply.
Kong Chhuon; Eugene Herrera; Kazuo Nadaoka. Application of Integrated Hydrologic and River Basin Management Modeling for the Optimal Development of a Multi-Purpose Reservoir Project. Water Resources Management 2016, 30, 3143 -3157.
AMA StyleKong Chhuon, Eugene Herrera, Kazuo Nadaoka. Application of Integrated Hydrologic and River Basin Management Modeling for the Optimal Development of a Multi-Purpose Reservoir Project. Water Resources Management. 2016; 30 (9):3143-3157.
Chicago/Turabian StyleKong Chhuon; Eugene Herrera; Kazuo Nadaoka. 2016. "Application of Integrated Hydrologic and River Basin Management Modeling for the Optimal Development of a Multi-Purpose Reservoir Project." Water Resources Management 30, no. 9: 3143-3157.