Light and nutrient limitation on phytoplankton production in the strait of an enclosed coastal sea (Bisan Strait, eastern Seto Inland Sea, Japan)

Spatio-temporal representativeness of euphotic depth in situ sampling in transitional coastal waters

“…AlvarezCobelas et al (2002) have noted that proper characterisation of underwater light field requires both spatially and temporally comprehensive sampling as they reported multiscale variability in optical properties of a small mesotrophic lake in Spain. Yamaguchi et al (2015) revealed that temporal variability in underwater light availability can cause spatial differences in seasonal phytoplankton dynamics by altering the (17,20,23,26,31,34,37, and 40, on the x-axis of the diagrams) is treated separately. Values exceeding the 25% difference limit are indicated in black.…”

Environmental and seasonal dynamics altering the primary productivity in Bingo-Nada (Bingo Sound) of the Seto Inland Sea, Japan

“…In connection with the recent January blooming that was not found in the 1970s through the 1990s, this spring minimum has not been previously recognized. However, in Bisan-Seto (Bisan Strait), from April 2012 to March 2013, primary production during the spring season similarly exhibited a minimum value in April, which was attributed to DIN depletion in April that lowered the photosynthetic yield versus light (Yamaguchi et al 2015). In addition to phytoplankton consumption, low riverine inflow in winter accelerated nutrient depletion.…”

“…Previous studies reported peaks in October, but phytoplankton species were not mentioned, and therefore the possibility of species transition could not be discussed. Yamaguchi et al (2015) also reported that primary production in Bisan-Seto (Bisan Strait) did not show an autumn bloom and constantly decreased from August to December, regardless of the highest photosynthetic yield being in October, and they concluded that the lack of an autumn production peak was attributed not to nutrient (DIN) deficiency but to the high turbidity in Bisan-Seto, where vertical mixing always dominates (Hashimoto et al 1997). The mechanism of primary production: summary…”

“…The current drastic changes in climate should also affect the mechanisms of productivity. However, the most recent investigations of primary productivity in the entire Seto Inland Sea were conducted in 1993 and 1994 (Tada et al 1998), with occasional research in the Bisan Strait (e.g., Yamaguchi et al 2015), and there has been a long-term gap in such studies from 1994 until now, although this period has experienced drastic environmental and climate changes. Therefore, to determine the most recent trends in the primary productivity of Bingo-Nada, we conducted monthly surveys from May 2014 to March 2018.…”

“…Methodologies using the principle of carbon assimilation, originally the assimilation of 14 C (Steemann-Nielsen 1951), have been standard in primary productivity estimation and have been used in surveys in the Seto Inland Sea (e.g., Endo 1964, 1970, Uye et al 1987). Because of limitations in using 14 C for carbon assimilation research, alternative methodologies using the stable isotope 13 C have been standardized in the sea (e.g., Tada et al 1998, Yamaguchi et al 2015. However, we did not employ this costly and labor-intensive methodology, because the aim of our study was to conduct frequent-long-term samplings at a site with relatively large horizontal and vertical environmental fluctuations, and to determine the environmental reasons (i.e., light, turbidity, nutrient levels, etc.)…”