Oligotrophication in the Seto Inland Sea

Yanagi, Tetsuo

doi:10.1007/978-94-017-9915-7_3

Cited by 13 publications

(11 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The depth of stations H5 and A6 were ca. 32 m and 54 m, and the mean depth in the northwestern part of Osaka Bay is deeper than that of Harima-Nada (Yanagi 2008). Uye (2000) has pointed out the importance of sufficient depth for C. sinicus to prosper to avoid embedding in bottom muds before egg hatching in addition to performing a full-scale diel vertical migration to avoid visual predators.…”

Section: Discussionmentioning

confidence: 99%

Temporal variations in the copepod community structure during the sand lance fishery season near the Akashi Strait, eastern Seto Inland Sea

Nishikawa,

Watanabe,

Furusawa

et al. 2024

Plankton Benthos Res

View full text Add to dashboard Cite

Around the Akashi Strait, about half of the catch of the sand lance in Harima-Nada and Osaka Bay is caught in winter to early spring. The annual catch has continued to decrease after the 1990s, and it is suggested that the decline in catch was caused by copepod shortage as food. In the present study, frequent samplings of copepods were conducted from December to early April around the Akashi Strait for three years to evaluate copepod abundance and biomass. Around the Akashi Strait, the dominant species by abundance were Paracalanus spp., Oithona spp. and Microsetella norvegica, but by biomass, the most dominant was Calanus sinicus. Cluster analysis showed that copepod adult communities, based on biomass, were classified into five groups, and the representative species were Oithona similis, Subeucalanus crassus, M. norvegica, Euchaeta plana and C. sinicus, respectively. Especially from February to early April, most of the copepod communities were classified into cluster group 5, characterized by a high biomass of C. sinicus. This period coincides with the active feeding on copepods by sand lance. These results suggest that C. sinicus is the most important prey item for sand lance around the Akashi Strait. In addition, the temporal recruitment of pelagic species such as S. crassus and E. plana contributed to an increase in copepod biomass. There is concern that environmental shifts will lead to declines in C. sinicus, resulting in a decline in the total copepod biomass in this area.

show abstract

Section: Discussionmentioning

confidence: 99%

Temporal variations in the copepod community structure during the sand lance fishery season near the Akashi Strait, eastern Seto Inland Sea

Nishikawa,

Watanabe,

Furusawa

et al. 2024

Plankton Benthos Res

View full text Add to dashboard Cite

show abstract

“…This study provides strong validation for measurements of primary productivity by FRRf in lakes with large spatiotemporal variabilities of phytoplankton assemblages and environmental conditions from oligo- to mesotrophic lakes (or lacustrine) environments. In the future, bio-optical measurements will allow researchers to disentangle the causality between anthropogenic nutrient control and fish catch [13,59,106], and between climate change and the production of higher trophic levels [7,107].…”

Section: Discussionmentioning

confidence: 99%

Development of photosynthetic carbon fixation model using multi-excitation wavelength fast repetition rate fluorometry in Lake Biwa

Kazama

Hayakawa

Kuwahara

et al. 2020

Preprint

View full text Add to dashboard Cite

Direct measurements of gross primary productivity (GPP) in the water column are essential, but can be spatially and temporally restrictive. Fast repetition rate fluorometry (FRRf) is a bio-optical technique based on chlorophyll a (Chl- a ) fluorescence that can estimate the electron transport rate (ETR PSII ) at photosystem II (PSII) of phytoplankton in real time. However, derivation of phytoplankton GPP in carbon units from ETR PSII remains challenging because the electron requirement for carbon fixation (Ф e,C ) can vary depending on multiple factors. Also, the FRRf is still relatively novel, especially in freshwater ecosystems where phosphorus limitation and cyanobacterial blooms are common. The goal of the present study is to construct a robust Ф e,C model for freshwater ecosystems using simultaneous measurements of ETR PSII by FRRf with multi-excitation wavelengths coupled with traditional carbon fixation rate by the 13 C method. The study was conducted in oligotrophic and mesotrophic areas in Lake Biwa from July 2018 to May 2019. The combination of excitation light at 444, 512 and 633 nm correctly estimated ETR PSII of cyanobacteria. The range of Ф e,C in the phytoplankton community varied from 1.1 to 31.0 mol e − mol C −1 during the study period. Generalized liner model showed the best model including 12 physicochemical and biological factors explained 67% of the variance in Ф e,C . Among all factors, water temperature was the most significant, while PAR intensity was not. The GPP values estimated by FRRf ( GPP f ) with the best Ф e,C model relative to 13 C ( GPP 13C ) varied 0.5–1.5. Further, GPP f estimated with more parsimonious Ф e,C models were also comparable to GPP 13C . This study quantifies the applicability of the in situ FRRf methodology, and supports continuous monitoring of GPP by FRRf in lakes with large spatio-temporal variability of environmental conditions and phytoplankton assemblages.

show abstract

“…As a result, phytoplankton growth will be limited with long-term decline (Figure 2A) associated with decreasing primary production 37 . In coastal and enclosed seas, measures to reduce nutrient loading can lead to decreased phytoplankton concentration or reduce the eutrophication and associated ecological disasters such as the incidence of hypoxic events, though other issues like oligotrophication can emerge 38 . The Seto Inland Sea of Japan experienced severe eutrophication during the high economic growth period of the 1960s and 1970s 39 , but now is reported to be undergoing oligotrophication 38 .…”

Section: Assessment Of Coastal Eutrophication Potential: Global Oceanmentioning

confidence: 99%

“…In coastal and enclosed seas, measures to reduce nutrient loading can lead to decreased phytoplankton concentration or reduce the eutrophication and associated ecological disasters such as the incidence of hypoxic events, though other issues like oligotrophication can emerge 38 . The Seto Inland Sea of Japan experienced severe eutrophication during the high economic growth period of the 1960s and 1970s 39 , but now is reported to be undergoing oligotrophication 38 . Signi cant reductions in nutrient loading along with loss in biodiversity are reported to be the precursors of oligotrophication.…”

Section: Assessment Of Coastal Eutrophication Potential: Global Oceanmentioning

confidence: 99%

Globally Consistent Assessment of Coastal Eutrophication

Maúre

Terauchi

Ishizaka

et al. 2021

Preprint

View full text Add to dashboard Cite

Eutrophication associated with increasing anthropogenic nutrient loading is an emerging global concern. Often, eutrophication is concomitant with negative impacts on ecosystems and human well-being. Nevertheless, the impacts and the extent of eutrophication are limited to regions with dedicated monitoring programmes. Here we introduce the Global Eutrophication Watch, the first global and interactive assessment map of coastal eutrophication potential (CEP). It is constructed on Google Earth Engine and it evaluates temporal trends in satellite chlorophyll-a (CHL), a proxy for phytoplankton biomass, to devise a global map of CEP. Our analyses suggest that, globally, coastal waters (depth ≤ 200 m) covering ~ 1.15 million km2 are eutrophic potential. We found that waters associated with CHL increasing trends—those with potential for further deterioration of water quality—are twofold higher than those showing signs of recovery. The tool effectively identified areas of known eutrophication with severe symptoms, such as dead zones, as well as those with limited to no information of the eutrophication. Our tool introduces the prospect for a consistent global assessment of eutrophication trends with major implications for monitoring Sustainable Development Goals (SDGs). This work contributes to the application of Earth Observations in support of SDGs.

show abstract

Oligotrophication in the Seto Inland Sea

Cited by 13 publications

References 6 publications

Temporal variations in the copepod community structure during the sand lance fishery season near the Akashi Strait, eastern Seto Inland Sea

Temporal variations in the copepod community structure during the sand lance fishery season near the Akashi Strait, eastern Seto Inland Sea

Development of photosynthetic carbon fixation model using multi-excitation wavelength fast repetition rate fluorometry in Lake Biwa

Globally Consistent Assessment of Coastal Eutrophication

Contact Info

Product

Resources

About