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Algal blooms dominated by the raphidophyte Chattonella spp. and diatom Skeletonema spp. are a regular summer‐time phenomenon in the Ariake Sea (Japan). Given its high‐temporal frequency, the Geostationary Ocean Color Imager (GOCI) affords us the extraordinary ability to investigate short‐temporal scale dynamic of these blooms. Here we present a bloom detection method and classification criteria named Normalized Difference Red Peak Index (NDRI), which relies on a combination of data from the red wavebands of GOCI, with the spectral shape of remote sensing reflectance (Rrs(λ)) around 490 nm [SS(490)] to distinguish bloom pixels from nonbloom pixels. Diurnal changes in the bloom distribution and intensity were successfully captured by the new method with GOCI data. In the next step, an optical discrimination method was developed to differentiate Chattonella spp. from Skeletonema spp. blooms. Specifically, the backscattering at 555 nm of bloom waters was retrieved from a bio‐optical algorithm, bbp_index(555), based on the satellite Rrs(λ) of green and red bands. Combined with the NDRI, bloom species were successfully differentiated in the featured distribution of bbp_index(555). Further validations using GOCI images series and local observations indicate that the newly developed algorithm yields robust classification results. Moreover, transitions in Skeletonema spp. and Chattonella spp. blooms were captured in a 20 days time series of daily composite GOCI for July 2018. The successful application of the classification approach to GOCI opens up the possibility of understanding the factors influencing daily changes of harmful blooms in Ariake Sea, which at present is limited by the paucity of field observations. Plain Language Summary: Harmful blooms reflect anomalous growth of phytoplankton that are either toxic or can have negative impacts on the environment, seafood production, and other ecosystem services that are important for coastal economies. The Ariake Sea which is known for its high biological productivity in Japan, suffers on account of frequent outbreaks of harmful blooms during summer, a phenomenon that has exacerbated in recent years. Chattonella spp. and Skeletonema spp. are the most common bloom forming phytoplankton species. In this study, bloom waters were distinguished from nonbloom waters by the unusual spectral shape of remote sensing reflectance at blue and red wavebands. Chattonella spp. blooms were discriminated from Skeletonema spp. blooms using a backscattering‐based index developed from bio‐optical models. More than 80% of Chattonella spp. blooms were correctly classified using this index. Transitions of blooms from Skeletonema spp. to Chattonella spp. were captured by applying this method to daily composite GOCI images. Key Points: Harmful algal blooms were discriminated using GOCI imagesThe bbp_index(555) algorithm performs well in discriminating phytoplankton bloom typesTransitions of the Skeletonema spp. and Chattonella spp. blooms were captured by the daily composite GOCI images [ABSTRACT FROM AUTHOR]

The effect of photosynthetically active radiation (PAR) and temperature on photosynthesis of the cultivated red alga, Pyropia yezoensis f. narawaensis (Saga-#5 Strain, Bangiales), was determined for microscopic sporophytes and macroscopic gametophytes with pulse-amplitude fluorometry and dissolved oxygen sensors. A clear difference in the temperature response of the maximum quantum yield ( Fv/ Fm) and oxygenic gross photosynthesis (GP) was revealed between the two life-history stages. The sporophyte Fv/ Fm was not sensitive to temperature, although the model revealed an Fv/ Fm maximum (0.60) at 16.7°C. In contrast, the gametophyte Fv/ Fm was clearly sensitive to temperature and attained a maximum mean value of 0.55 at 14.7°C. The relationship between GP and temperature was also different. The maximum rates of GP of the sporophyte occurred at 30.7°C and was 17.1 μg O2 mgchl-a−1 min−1 (15.4-19.4, 95% Bayesian credible interval); however, maximum rates of GP for the gametophyte were much higher (110 μmol O2 mgchl-a−1 min−1) and occurred at a lower temperature (14.4°C). The response of oxygenic net photosynthesis to PAR also varied, and the initial slope (α), the saturation PAR ( Ek) and the maximum photosynthetic rate ( Pmax) of the gametophyte were much higher than the sporophyte. Therefore, we hypothesised that in species with a heteromorphic life history, such as those in the genus Pyropia, physiological responses to environmental gradients would be dissimilar. [ABSTRACT FROM AUTHOR]

Presents a study which investigated the steroidogenic pathway for estradiol-17 β biosynthesis in vitellogenic ovarian follicles of the bambooleaf wrasse. Review of related literature; Materials and methods used; Results and discussion.

The raphidophyte Chattonella spp. and diatom Skeletonema spp. are the dominant harmful algal species of summer blooms in Ariake Sea, Japan. A new bio-optical algorithm based on backscattering features has been developed to differentiate harmful raphidophyte blooms from diatom blooms using MODIS imagery. Bloom waters were first discriminated from other water types based on the distinct spectral shape of the remote sensing reflectance R r s (λ) data derived from MODIS. Specifically, bloom waters were discriminated by the positive value of Spectral Shape, SS (645), which arises from the R r s (λ) shoulder at 645 nm in bloom waters. Next, the higher cellular-specific backscattering coefficient, estimated from MODIS data and quasi-analytical algorithm (QAA) of raphidophyte, Chattonella spp., was utilized to discriminate it from blooms of the diatom, Skeletonema spp. A new index b b p − i n d e x (555) was calculated based on a semi-analytical bio-optical model to discriminate the two algal groups. This index, combined with a supplemental Red Band Ratio (RBR) index, effectively differentiated the two bloom types. Validation of the method was undertaken using MODIS satellite data coincident with confirmed bloom observations from local field surveys, which showed that the newly developed method, based on backscattering features, could successfully discriminate the raphidophyte Chattonella spp. from the diatom Skeletonema spp. and thus provide reliable information on the spatial distribution of harmful blooms in Ariake Sea. [ABSTRACT FROM AUTHOR]

The accurate retrieval of chlorophyll-a concentration (Chl-a) from ocean color satellite data is extremely challenging in turbid, optically complex coastal waters. Ariake Bay in Japan is a turbid semi-enclosed bay of great socio-economic significance, but it suffers from serious water quality problems, particularly due to red tide events. Chl-a derived from the MODerate resolution Imaging Spectroradiometer (MODIS) sensor on satellite Aqua in Ariake Bay was investigated, and it was determined that the causes of the errors were from inaccurate atmospheric correction and inappropriate in-water algorithms. To improve the accuracy of MODIS remote sensing reflectance (Rrs) in the blue and green bands, a simple method was adopted using in situ Rrs data. This method assumes that the error in MODIS Rrs(547) is small, and MODIS Rrs(412) can be estimated from MODIS Rrs(547) using a linear relation between in situ Rrs(412) and Rrs(547). We also showed that the standard MODIS Chl-a algorithm, OC3M, underestimated Chl-a, which was mostly due to water column turbidity. A new empirical switching algorithm was generated based on the relationship between in situ Chl-a and the blue-to-green band ratio, max(Rrs(443), Rrs(448)/Rrs(547), which was the same as the OC3M algorithm. The criterion of Rrs(667) of 0.005 sr−1 was used to evaluate the extent of turbidity for the switching algorithm. The results showed that the switching algorithm performed better than OC3M, and the root mean square error (RMSE) of estimated Chl-a decreased from 0.414 to 0.326. The RMSE for MODIS Chl-a using the recalculated Rrs and the switching algorithm was 0.287, which was a significant improvement from the RMSE of 0.610, which was obtained using standard MODIS Chl-a. Finally, the accuracy of our method was tested with an independent dataset collected by the local Fisheries Research Institute, and the results revealed that the switching algorithm with the recalculated Rrs reduced the RMSE of MODIS Chl-a from 0.412 of the standard to 0.335. [ABSTRACT FROM AUTHOR]

SUMMARY The chronological change of photosynthetic efficiency in a frozen storage treatment of the Japanese Nori cultivation industry was examined in the cultivated red alga, Pyropia yezoensis f. narawaensis ( Saga-#5 Strain, Bangiales) by using pulse-amplitude fluorometry. During the desiccation process that was conducted after the nursery cultivation season in November, the maximum quantum yield ( Fv/ Fm) of the gametophytic sporelings growing on the Nori-net decreased monotonically with decreasing absolute water content ( AWC), and was around 0.1 at 20% AWC. During frozen storage of the Nori-net, the Fv/ Fm of the frozen gametophyte was low but stable, and ranged between 0.10 ± 0.02 SD and 0.14 ± 0.05 SD. The magnitude of Fv/ Fm for the gametophyte of the freezing treatment, after 10 min and 3 h of immersion in seawater, recovered quickly. After 10 min and 3 h of immersion, these values were 0.29 ± 0.12 SD and 0.47 ± 0.05 SD during the 14 days of freezing treatment, and 0.15 ± 0.02 SD and 0.29 ± 0.04 SD after 71 days of freezing treatment, and suggest that the ability to recover gradually decreased as the storage duration increased. The response of Fv/ Fm from general cultivation (i.e., directly cultivated from the nursery cultivation season) and those after 47 days of freezing were almost identical, suggesting that the current Nori -net frozen storage period (6 or 7 weeks) was not detrimental to the gametophyte. [ABSTRACT FROM AUTHOR]

In the innermost region of the Ariake Sea, Japan, the diatom Asteroplanus karianus (Grunow) C. Gardner & R.M. Crawford frequently forms massive blooms in winter, causing bleaching of cultured nori (Neopyropia) by exhausting seawater nutrients. To understand the bloom-forming mechanism of A. karianus , the effects of temperature and salinity on the rejuvenation of resting cells and the growth of rejuvenated vegetative cells were examined in the laboratory. Surface sediments from the Ariake Sea were cultured at 6.5, 10, 15, 20, 25, 27.5, and 30°C in media with a salinity of 30 to determine the suitable temperatures for rejuvenation and subsequent growth. A suitable temperature range for the rejuvenation and subsequent growth of A. karianus was found to be 10–20°C, and 15°C was revealed to be the optimum temperature. The sediments were then cultured in media with salinities of 3, 7.5, 12, 16.5, 21, 25.5, and 30 at 15°C to determine suitable salinity for rejuvenation and subsequent growth. The suitable salinity range for the rejuvenation was found to be 16.5–30, and growth of the rejuvenated vegetative cells at salinities of 25.5 and 30 was higher than at 16.5 and 21. These results suggest that suitable temperatures and salinities for the rejuvenation and subsequent growth of rejuvenated vegetative cells were 10–20°C and 25.5–30, respectively. This study suggested that A. karianus can bloom only in winter because the low water temperatures in late autumn and winter allowed for active rejuvenation and subsequent growth of A. karianus. • Suitable conditions for Asteroplanus karianus rejuvenation and growth were studied. • Temperatures of 10–20°C and salinities of 25.5–30 promoted rejuvenation and growth. • Optimum temperature for rejuvenation and subsequent growth was 15°C. • Active rejuvenation and subsequent growth at low temperatures lead to winter blooms. [ABSTRACT FROM AUTHOR]

It is widely accepted that the hypothalamic-pituitary-gonadal axis is involved in gonadal sex change in socially controlled sex-changing fish. However, the specific secretion profiles of pituitary gonadotropins (GtHs) in this type of fish are not known. To address this fundamental question, we demonstrated that the diurnal secretion patterns of GtHs differ distinctly between males and females in a socially controlled sex-changing fish. We analyzed the pituitary mRNA levels of glycoprotein hormone subunits (i.e., the common alpha-subunit and specific beta-subunits follicle-stimulating hormone beta, luteinizing hormone beta, and thyroid-stimulating hormone beta) in the wrasse Pseudolabrus sieboldi, which is a model fish that exhibits accurate diurnal rhythms of gametogenesis in both males and females. Northern blots clearly showed that each subunit gene exhibits a diurnal rhythm of expression in the pituitary and that the expression patterns differ distinctly between the sexes. Our results suggest that oogenesis and spermatogenesis in this hermaphroditic fish are regulated differentially through the distinct secretion patterns of pituitary glycoprotein hormones. This study also provides direct evidence of the sexual plasticity of pituitary GtH secretion in a socially controlled sex-changing fish., ((c) 2008 Wiley-Liss, Inc.)