El Niño is now a focal point for global climate change research, but its influence on the Western Pacific is still uncertain. Taiwan Strait is an important pathway, which connects the South China Sea and the East China Sea, and is strongly influenced by the monsoon. Generally, in winter, the strong winter monsoon brings the cold and nutrient-rich Changjiang Diluted Water¡]CDW¡^southward. While during the El Niño event, because of the weakened south wind in northern Taiwan, more cold CDW moves southward, and hence the decreased seawater temperature in spring and fall. The trend is opposite in summer. There is a high salinity signal in the seas outside of Hsin-Chu, suggesting sea water coming from the Kuroshio, which has circumvented the northeast tip of Taiwan. Meanwhile, there is a front which separates this Kuroshio water and CDW. During the El Niño, the front moves eastward, especially in summer. The salinity east of the front decreases gradually from spring to winter water, the center of upwelling located at the eastern side of the front in spring, and at or near the front from summer to winter. Furthermore, The N/P ratio of the northern Taiwan Strait water became higher after the Three Gorges Dam (TGD) became operational. The nitrous oxide (N2O) is a long-lived greenhouse gas. Unfortunately, in Taiwan, there are few data about N2O emission from rivers, lakes and coastal areas. This research also studies the N2O distribution in natural waters around Taiwan. The average surface water concentration and sea to air flux in the Taiwan Strait¡]7.81¡Ó1.28nM¡F0.28¡Ó0.38£gmol/m2/hr¡^is higher than in the South China Sea¡]SCS¡F7.55¡Ó2.45 nM¡F0.21¡Ó0.27£gmol/m2/hr¡^and the West Philippine Sea¡]WPS¡F5.3¡Ó0.62nM¡F-0.20¡Ó0.25£gmol/m2/hr¡^, which displays a rare sink signal in the world oceans. There is an N2O maximum observed around 1000m in the WPS, and another shollower one around 700m in the SCS, presumably because of the intenive upwelling and vertical mixing in the SCS basin. There are some rather high N2O concentrations (N2O>30nM) in the SCS, observed near the continental slope. We assume that these are released from sediments on the continental slope. Although the sea-to-air flux of N2O is much lower than the flux of CO2, N2O emission in the SCS contributes more than two times the greenhouse effect than CO2 does. Besides, The N2O concentration during El Niño is lower than usual, probably due to a smaller amount of the CDW. Finally, the average N2O concentrations of river and submarine groundwater discharge in Taiwan are about 32.3¡Ó43.3nM and 9.72¡Ó13.2 nM, respectively.

Phytoplankton dynamics and chemical characteristics of the euphotic zone were measured from 1998-2000 (an El Niño/La Niña cycle) at the 5 major stations along Line P. Near-shelf and offshore stations exhibited low seasonality in chlorophyll and moderate seasonality in particulate organic carbon (POC) production. During the 1998 El Niño, June was characterized by low chlorophyll and POC productivity due to nitrate depletion. In contrast, during the 1999 La Niña, and in 2000, higher POC productivity and nitrate occurred in June. During 1999, chlorophyll and POC productivity were similar to 1998 in late summer. Near-shelf biomass was highest in June and lowest in Feb. for the near-shelf stations. High nitrate, low chlorophyll (HNLC) stations had the highest chlorophyll in Feb. followed by June. The coccolithophore assemblage was usually numerically dominated by Emiliania huxleyi, particularly in June. Along the transect, coccolithophore abundance was much higher in June during the 1998 El Niño than in the 1999 La Niña, with Aug./Sept. abundance of both years being very low. Higher abundances were measured along the transect in June and the late summer of 2000 with sporadic ‘blooms’ of >1000 cells ml⁻¹ at some stations. Particulate inorganic carbon (PIC) production was high along the transect during June 1998, and low during both winters, June 1999 and during late summers of 1998 and 1999. There was an increase in diatom biomass and >20 µm POC production during the 1998 El Niño, specifically in the farthest offshore HNLC stations, yet diatoms were rarely found to dominate total phytoplankton biomass or production. However, there were some sporadic examples of anomalously high diatom biomass (carbon and abundance) as well as >20 µm POC production, specifically at P12 in Aug./Sept 2000. The same major diatom species were found throughout Line P (near-shelf, P16, and HNLC). Integrated silica production measured by ³²Si ranged from 0.2 to 4.7 mmol Si m⁻² d⁻¹ between 1999-2000. Silicic acid and nitrate were never limiting at all stations in Feb. and generally increased in concentration along Line P during all seasons.

Phytoplankton dynamics and chemical characteristics of the euphotic zone were measured from 1998-2000 (an El Niño/La Niña cycle) at the 5 major stations along Line P. Near-shelf and offshore stations exhibited low seasonality in chlorophyll and moderate seasonality in particulate organic carbon (POC) production. During the 1998 El Niño, June was characterized by low chlorophyll and POC productivity due to nitrate depletion. In contrast, during the 1999 La Niña, and in 2000, higher POC productivity and nitrate occurred in June. During 1999, chlorophyll and POC productivity were similar to 1998 in late summer. Near-shelf biomass was highest in June and lowest in Feb. for the near-shelf stations. High nitrate, low chlorophyll (HNLC) stations had the highest chlorophyll in Feb. followed by June. The coccolithophore assemblage was usually numerically dominated by Emiliania huxleyi, particularly in June. Along the transect, coccolithophore abundance was much higher in June during the 1998 El Niño than in the 1999 La Niña, with Aug./Sept. abundance of both years being very low. Higher abundances were measured along the transect in June and the late summer of 2000 with sporadic ‘blooms’ of >1000 cells ml⁻¹ at some stations. Particulate inorganic carbon (PIC) production was high along the transect during June 1998, and low during both winters, June 1999 and during late summers of 1998 and 1999. There was an increase in diatom biomass and >20 µm POC production during the 1998 El Niño, specifically in the farthest offshore HNLC stations, yet diatoms were rarely found to dominate total phytoplankton biomass or production. However, there were some sporadic examples of anomalously high diatom biomass (carbon and abundance) as well as >20 µm POC production, specifically at P12 in Aug./Sept 2000. The same major diatom species were found throughout Line P (near-shelf, P16, and HNLC). Integrated silica production measured by ³²Si ranged from 0.2 to 4.7 mmol Si m⁻² d⁻¹ between 1999-2000. Silicic acid and nitrate were never limiting at all stations in Feb. and generally increased in concentration along Line P during all seasons.

abstract: Many studies over the past two decades examined the link between climate patterns and discharge, but few have attempted to study the effects of the El Niño Southern Oscillation (ENSO) on localized and watershed specific processes such as nutrient loading in the Southwestern United States. The Multivariate ENSO Index (MEI) is used to describe the state of the ENSO, with positive (negative) values referring to an El Niño condition (La Niña condition). This study examined the connection between the MEI and precipitation, discharge, and total nitrogen (TN) and total phosphorus (TP) concentrations in the Upper Salt River Watershed in Arizona. Unrestricted regression models (UMs) and restricted regression models (RMs) were used to investigate the relationship between the discharges in Tonto Creek and the Salt River as functions of the magnitude of the MEI, precipitation, and season (winter/summer). The results suggest that in addition to precipitation, the MEI/season relationship is an important factor for predicting discharge. Additionally, high discharge events were associated with high magnitude ENSO events, both El Niño and La Niña. An UM including discharge and season, and a RM (restricting the seasonal factor to zero), were applied to TN and TP concentrations in the Salt River. Discharge and seasonality were significant factors describing the variability in TN in the Salt River while discharge alone was the significant factor describing TP. TN and TP in Roosevelt Lake were evaluated as functions of both discharge and MEI. Some significant correlations were found but internal nutrient cycling as well as seasonal stratification of the water column of the lake likely masks the true relationships. Based on these results, the MEI is a useful predictor of discharge, as well as nutrient loading in the Salt River Watershed through the Salt River and Tonto Creek. A predictive model investigating the effect of ENSO on nutrient loading through discharge can illustrate the effects of large scale climate patterns on smaller systems. / Dissertation/Thesis / M.S. Biology 2012

Made available in DSpace on 2014-06-11T19:30:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-02-24Bitstream added on 2014-06-13T18:59:56Z : No. of bitstreams: 1 bochini_gl_me_botib.pdf: 1046951 bytes, checksum: c853155f5ecbb629ac360d4f519b2981 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O presente estudo foi dividido em dois capítulos e tiveram como objetivos: cap.1- verificar a distribuição espaço-temporal de L. schmitti em três baías do litoral norte do estado de São Paulo, Ubatumirim (UBM), Ubatuba (UBA) e Mar Virado (MV); testar a relação dos fatores ambientais com a distribuição dos camarões durante um período de 2 anos (1998 e 1999) e cap. 2- averiguar a variação anual e sazonal da biomassa e do número de indivíduos do camarão, durante 4 anos de estudo (1998, 1999, 2002, 2006), com enfoque no período reprodutivo e de recrutamento juvenil informando qual a melhor época para a pesca. Os camarões foram capturados com um barco camaroneiro equipado com redes do tipo “double-rig” em profundidades até os 20 metros. Em 1998 e 1999, um total de 5658 indivíduos foi coletado, sendo 4437 no primeiro ano e 1221 no segundo ano. Em MV obteve-se a maior abundância (n= 2747), seguido de UBM (n= 1649) e UBA (n=1262). A salinidade da água variou de 28 a 37 com média de 34,6 ± 1,44, porém não houve correlação significativa desse fator com a abundância (p=0,90). A média da temperatura de fundo foi de 24,8 ± 2,84 °C com valor máximo de 31,4 °C e mínimo de 19 °C. Apesar dessa grande variação nos valores obtidos, não houve correlação significativa desse fator com a abundância (p= 0,11). A maior captura de camarões foi registrada em áreas onde silte + argila correspondem mais de 70 % do sedimento e em locais com maior porcentagem de matéria orgânica. Houve relação inversa da abundância com a pluviosidade, com as maiores abundâncias nos meses posteriores a temporada de chuvas. Porém, no ano em que houve maior pluviosidade, também houve uma maior captura de indivíduos. A quantidade de camarões seguiu uma tendência sazonal, sendo maior durante o outono e inverno... / The present study was divided in two chapters, which aimed: chapter 1 – to verify the spatiotemporal distribution of L. schmitti in three bays of north littoral of São Paulo State, Ubatumirim (UBM), Ubatuba (UBA) e Mar Virado (MV); to test the relation between environmental factors and shrimp distribution, during a 2-year period (1998 and 1999) and chapter 2 – to investigate the annual and seasonal variation of biomass and of the number of shrimp individuals, focusing reproductive period and juvenile recruitment; which is the best period for the open season; the rainfall influence on abundance during 4 years of study (1998, 1999, 2002 and 2006). Shrimps were captured with a shrimp fishing boat equipped with two double-rig nets at depths up to 20m. In 1998 and 1999, a total of 5658 individuals was collected, being 4437 on first year and 1221 on second year. The highest abundance was obtained at MV (n=2747), followed by UBM (n=1649) and then by UBA (n=1262). Water salinity has varied from 28 to 37, with average of 34.6 ± 1.44, although abundance has not had a significant correlation with this factor (p=0,90). The average bottom temperature was of 24,8 ± 2,84 °C, with a maximum of 31.4 °C and a minimum of 19°C. Besides the great variation on these values, abundance has not had a significant correlation with this factor (p=0.11). The higher shrimp capture was registered in areas where sediment was composed by more than 70% of silt + clay and at areas with highest percentage of organic-matter. There was an inverse correlation between abundance and rainfall, with the highest abundances on months after the rainy season. However, the highest individual catch occurred in the year with highest rainfall rates. Shrimp amount had a seasonal tendency, being higher during autumn and winter in both years. A total of 566 (13,171 g) individuals... (Complete abstract click electronic access below)

A 0.24 degrees C jump of record warm global mean surface temperature (GMST) over the past three consecutive record-breaking years (2014-2016) was highly unusual and largely a consequence of an El Nino that released unusually large amounts of ocean heat from the subsurface layer of the northwestern tropical Pacific. This heat had built up since the 1990s mainly due to greenhouse-gas (GHG) forcing and possible remote oceanic effects. Model simulations and projections suggest that the fundamental cause, and robust predictor of large record-breaking events of GMST in the 21st century, is GHG forcing rather than internal climate variability alone. Such events will increase in frequency, magnitude, and duration, as well as impact, in the future unless GHG forcing is reduced.

Typically, multi-model ensemble studies show mixed responses of El Nino Southern Oscillation (ENSO) under global warming, so it is currently unknown how, or even if, global warming will impact ENSO and its teleconnections. ENSO is governed by various ocean-atmosphere interactions in the equatorial Pacific, which provide either positive amplifying or negative damping feedbacks and are not always accurate in models. This results in uncertainty in projected ENSO responses. In a flux adjusted HadCM3 perturbed physics ensemble, the Bjerknes' stability index (BJ index), a measure of ENSO stability, has been used to analyse the strength of ENSO feedbacks and their response under the SRES A1B warming scenario with respect to mean climate conditions. Despite mean sea surface temperature biases being minimised by flux adjustment, the important dominant feedbacks, namely the latent heat flux feedback, shortwave flux feedback, the thermocline feedback and the zonal advective feedback are found to be too weak in the ensemble. Common model biases cause weak ocean-atmosphere interactions such as a weak response of ocean currents to wind stress anomalies, a weak thermocline slope response to wind stress anomalies and weak thermodynamic dampings. These biases are linked to overly strong zonal surface ocean currents and convective response biases. Under global warming, a large increase in thermodynamic damping, caused by increasing shortwave damping, is found. This increase is linked to a strong convective response and overrides other feedback responses, resulting in a weakening BJ index in contrast to increasing ENSO amplitude. Positive feedback responses are also found but counteract each other, so have relatively little impact on total ENSO stability. Results here show that common model biases, such as the cold tongue bias, are linked to persistent ENSO feedback biases pointing to areas of improvement in future models. Results also suggest that caution must be exercised when using the BJ index to assess ENSO, as the BJ index is not always representative of ENSO amplitude. This may be caused by non-linearities in ENSO feedbacks which are not accounted for by the linear approximations used in the BJ index, or by ENSO feedbacks not being directly comparable in magnitude, as assumed by the BJ index calculation.

Phytoplankton dynamics and chemical characteristics of the euphotic zone were measured from 1998-2000 (an El Niño/La Niña cycle) at the 5 major stations along Line P. Near-shelf and offshore stations exhibited low seasonality in chlorophyll and moderate seasonality in particulate organic carbon (POC) production. During the 1998 El Niño, June was characterized by low chlorophyll and POC productivity due to nitrate depletion. In contrast, during the 1999 La Niña, and in 2000, higher POC productivity and nitrate occurred in June. During 1999, chlorophyll and POC productivity were similar to 1998 in late summer. Near-shelf biomass was highest in June and lowest in Feb. for the near-shelf stations. High nitrate, low chlorophyll (HNLC) stations had the highest chlorophyll in Feb. followed by June. The coccolithophore assemblage was usually numerically dominated by Emiliania huxleyi, particularly in June. Along the transect, coccolithophore abundance was much higher in June during the 1998 El Niño than in the 1999 La Niña, with Aug./Sept. abundance of both years being very low. Higher abundances were measured along the transect in June and the late summer of 2000 with sporadic ‘blooms’ of >1000 cells ml⁻¹ at some stations. Particulate inorganic carbon (PIC) production was high along the transect during June 1998, and low during both winters, June 1999 and during late summers of 1998 and 1999. There was an increase in diatom biomass and >20 µm POC production during the 1998 El Niño, specifically in the farthest offshore HNLC stations, yet diatoms were rarely found to dominate total phytoplankton biomass or production. However, there were some sporadic examples of anomalously high diatom biomass (carbon and abundance) as well as >20 µm POC production, specifically at P12 in Aug./Sept 2000. The same major diatom species were found throughout Line P (near-shelf, P16, and HNLC). Integrated silica production measured by ³²Si ranged from 0.2 to 4.7 mmol Si m⁻² d⁻¹ between 1999-2000. Silicic acid and nitrate were never limiting at all stations in Feb. and generally increased in concentration along Line P during all seasons. / Science, Faculty of / Botany, Department of / Graduate

Chondrichthyans—sharks, rays, skates, and chimaeras—influence top down control of food webs and connect disparate ecosystems, yet populations of many species around the world have experienced sharp declines in abundance. Marine protected areas (MPAs) have a long history of conserving marine biodiversity, but their effectiveness to protect representative and critical habitat for threatened species on a global scale is controversial and hindered by a lack of biological and ecological data for the majority of chondrichthyan species. In this thesis, I use non-invasive baited remote underwater video (BRUV) and citizen science diver data to explore diverse chondrichthyan communities in two countries, South Africa and Costa Rica, with data-poor chondrichthyan fisheries and limit conservation funding, and the relationships of these chondrichthyans to biotic and abiotic factors in their habitats in and around MPAs. First, through a literature review, I find substantial taxonomic and geographic biases in understanding of reef shark biology, ecology, and conservation, which impair ability to implement effective conservation measures for these species. After identifying these research gaps, I used BRUVs to explore the diversity of a chondrichthyan hotspot in South Africa, finding many poorly understood endemic chondrichthyans. I discovered strong associations of the chondricthyan community to different habitat types (sand versus reef and kelp habitat), which resulted in poor diversity within one of the region’s larger MPAs—a whale sanctuary whose focus on large charismatic whales left mostly poorer quality sand habitat protected. However, a high occurrence of chondrichthyans within a neighbouring MPA suggested even small MPAs can conserve a high abundance of smaller species, especially if residency can be demonstrated. I then used the BRUV data to examine the relationships amongst these chondrichthyans and the community of other marine animals within the region, finding strong co-occurrence patterns that suggest chondrichthyans, particularly the endemic catsharks, could serve as effective ‘umbrella’ species for conservation in this region where little other information is available for conservation planning and monitoring. Finally, at Cocos Island, an MPA off Costa Rica, I discovered similarly strong, species-specific associations to another aspect of habitat: temperature. I found significant and species-specific responses to the El Niño–Southern Oscillation (ENSO). For example, the scalloped hammerhead Sphryna lewini counts declined by 224.7% during strong El Niño conditions and by 14.7% with just a 1°C rise in SST, while the benthic whitetip reef shark Triaenodon obesus had a weaker response, dropping by only 7.9% and 4.4%, respectively. In general, strong El Niño events reduced sightings within the MPA, providing some of the first indications of how a rising frequency and intensity of these events will impact the spatial distribution of both chondrichthyans and their habitat in the Eastern Tropical Pacific. Overall, this thesis provides insight into the factors influencing chondrichthyan abundance and diversity, demonstrating the importance of considering both biotic and abiotic factors during MPA design and the need to study these factors across diverse taxonomic groups and ecosystems. / Graduate / 2021-05-08

付記する学位プログラム名: グローバル生存学大学院連携プログラム / 京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21058号 / 工博第4422号 / 新制||工||1687(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 寶 馨, 教授 堀 智晴, 准教授 佐山 敬洋 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM