Blooms of Akashiwo sanguinea
(Dinophyceae) in a tropical estuary
in northeastern Brazil
We report an inter-annual bloom of
the unarmored dinoflagellate Akashiwo
sanguinea in a pristine estuary (Figure
1F) in Brazil. The estuarine section of
the Serinhaém River, Camamu Bay is
a species-rich ecosystem located in
the state of Bahia (Northeastern Brazil, Figure 1G), comprising preserved
mangrove vegetation and remaining
fragments of Atlantic Forest. It is an
important regional center of economic
activities based on coastal tourism and
fishing. We sampled ten areas along a
30 km transect starting downstream in
March 2013 and April 2014 during the
rainy period (260 mm), and October
2013 and November 2014, during the
dry period (235 mm). Water and surface
sediment samples were collected along
a salinity gradient, stored in plastic bottles and preserved in Lugols solution
and formaldehyde. Cell counts were
made following the Utermöhl method
with 5 ml of material observed using
an inverted microscope Olympus CKX
41. Linear dimensions, such as length,
width, and height were measured under
400x magnification prior to calculating
biovolume by geometric shape.
Based on discontinuities in spatial
variability, the estuary was divided into
three sections (Figure 1E) according to
Ward agglomerative clustering of log
transformed biovolume: (I) the four
downstream sites (SE1SE4) with high
values of salinity, mainly in the dry seasons, high pH, and where A. sanguinea
did not occur; (II) the three intermediate sites (SE5SE7) where salinity varied from ~17 to ~28 and A. sanguinea
biovolume varied from intermediate
values in 2013 to high values in the
rainy season of 2014, along with local
extinction during the dry season in this
same year; and (III) the three upstream
sites (SE8SE10), which formed a group
due to remarkable enhanced abundances of A. sanguinea, reaching up to 2 million cells L-1, as well as enhanced environmental heterogeneity (variability in
nutrient and hydrological conditions).
The highest biovolumes observed in the
recent study were during the first dry
season, specifically at the warm, stratified upstream conditions occurred during October/November (Figure 1C).
Bloom events occur in response to
specific environmental conditions, such
as high nutrient concentrations and low
turbulence [1]. These constraints partly
explain the high accumulation of A. sanguinea during the first dry season, when
stratification from reduced turbulence
created vertical gradients of nutrients
and light [2]. Under these conditions, A.
sanguinea is able to vertically migrate
in spiral movements and overcome the
vertical displacement of nutrients, optimizing its resource exploitation and
generating advantages over non-motile
taxa. The local source of nutrients or
disturbance also explains high accumulations upstream, since SE10 is the site
nearest to the town of Ituberá (68 meters), where the river receives an average effluent discharge of 18.08 m3 s-1. It
has been demonstrated that potentially
harmful algae blooms (among them A.
sanguinea) can be spatially correlated
with effluent discharge gradients [3].
On another level, a disturbance source
Figure 1. Map showing (G) the geographic location of the study area in Brazil, (A-D) the sampled sites along the Serinhaém River, (E ) biovolume (log transformed) of A. sanguinea along the Serinhaém River (point density) and clusters based on spatial discontinuities of biovolume
values along sites, (F) light micrograph of sample from site SE10 during the dry season of 2013 (highest accumulation) showing several cells at
different side views (200x magnification) and (H) temporal and spatial variability of the main nutrient and environmental descriptors of the
Serinhaém River. The colors represent each season (blue and purple lines for rainy seasons, red and green lines for dry seasons), the figure is
plotted downward in order to match the map visualization.
16
HARMFUL ALGAE NEWS NO. 67 / 2021
Harmful Algae News An IOC Newsletter on Toxic Algae and Algal Blooms No. 67 - April 2021 www.ioc-unesco.org/hab SHIOHIGARI and PSP toxins in Japan: Initiatives to save traditional recreatio nal clam picking Shiohigari has been enjoyed by people in Japan for centuries, as depicted in the Japanese a
Fig. 2 Clamming parks in Osaka Prefecture (Modified from a digital map of The Geospatial Information Authority of Japan) ingly, they had developed the exchange system to secure viability of their operations before 2002 when PST exceeding the regulatory limit were first detected in clams from seas a
Fig. 4 System of exchanging clams which secure food safety at Tannowa clamming park (Modified from [3} of visitors to clamming parks has now recovered. This is a success story of how to mitigate socio-economic impact on recreational clamming in Osaka prefecture due to PST. Thanks to the initiatives
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Acknowledgements We are grateful to Kyle Turner for helpful discussions regarding the fall 2018 EcoMon cruise and to Dr. Irene Andreu for SEM assistance. Dr. Paul E. Hargraves provided some insights on diatom taxonomy. We acknowledge the dedication of the crew of the R/V Sharp during a particularly
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Blooms of Akashiwo sanguinea (Dinophyceae) in a tropical estuary in northeastern Brazil We report an inter-annual bloom of the unarmored dinoflagellate Akashiwo sanguinea in a pristine estuary (Figure 1F) in Brazil. The estuarine section of the Serinhaém River, Camamu Bay is a species-rich ecosystem
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Authors Raquel AF Neves, Júlia Torres, Nathália Rodrigues & Clarissa Naveira, Graduate Program in Neotropical Biodiversity (PPGBIO), Research Group in Experimental and Applied Aquatic Ecology, Federal University of the State of Rio de Janeiro (UNIRIO), Avenida Pasteur 458-307 Rio de Janeiro- RJ, CEP
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Aotearoa/New Zealand Japan collaboration strengthened through HAB research at Cawthron Institute the 16th Young Researchers Award from the Japanese Society of Phycology for his research on harmful algae in Japan. Acknowledgements The collaboration between New Zealand and Japan has been continued
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