Download PICES XV S9-2846 Poster The role of temperature, salinity, light

PICES XV
S9-2846
Poster
The role of temperature, salinity, light intensity and photoperiod for dinoflagellates,
Ceratium furca and Ceratium fusus, in the temperature coastal water of Sagami Bay,
Japan
Seung Ho Baek, Shinji Shimode and Tomohiko Kikuchi
Graduate School of Environmental and Information Sciences, Yokohama National University, Tokiwadai, 79-2, Hodogaya-ku, Yokohama,
240-8501, Japan. E-mail: [email protected]
Seasonal changes of field populations and growth rates of two dinoflagellates, Ceratium furca and Ceratium
fusus, were examined in the temperate coastal waters of Sagami Bay, Japan. Weekly field sampling was
conducted from August 2002 to August 2003, and laboratory experiments carried out to investigate the effects
of temperature, irradiance and photoperiod on the growth rates of the two species. In the field, both species
increased significantly in abundance from April to August, and gradually decreased from November 2002 to
January 2003. In February 2003, C. fusus increased its population even at lower temperatures (ca. 13ºC). In the
laboratory, the two species did not grow at temperatures < 10ºC or > 32ºC. The highest specific growth rate of
C. furca was 0.72 d-1 at 24ºC and 600 µmol m-2s-1. Optimum growth rates (> 0.4 d-1) of C. furca were observed
at temperatures from 18 to 28 ˚C and at irradiances from 216 to 796 µmol m-2s-1. On the other hand, the highest
growth rate of C. fusus was 0.56 d-1 at 26ºC and 216 µmol m-2s-1. Optimum growth rates of C. fusus were
observed at the same irradiance rage of C. furca, whereas its temperature range was narrower (26 to 28ºC).
Growth curves of both species indicated saturation of growth rates above irradiance of 216 µmol m -2s-1, but no
photoinhibition was also observed up to 796 µmol m-2s-1. Moreover, the specific growth rates of both Ceratium
species were clearly decreased at L: D = 10:14, compared to those at L: D = 14:10 and L: D = 12:12. The
present study clearly indicates that the two Ceratium species adapt to a wide-range of temperature and
irradiance, implying that their adaptations make them one of the dominant species and allow their sustainance
beyond normal growth seasons in the temperate waters in the world ocean.
PICES XV
S9-2798
Poster
Basic factors determinative phytoplankton bloom in the western subarctic Pacific and
the adjacent deep area of the Bering Sea in spring of 2005
Boris M. Borisov
Far Eastern Regional Hydrometeorological Research Institute, Vladivostok, 690091, Russia. E-mail: [email protected]
In spring of 2005, a plankton survey was carried out in the western subarctic Pacific Ocean and in the adjacent
deep area of the Bering Sea. During the survey, an intense algal bloom occurred in the study area; the highest
biomass of net-collected phytoplankton at the upper 50m layer was 2900mg m-3. Mesozooplankton samples
were represented mainly by fragments of large body-size species - salps and heteropods, typical inhabitants of
the south boundary of the Western Subarctic Gyre. The composition of the remainder of zooplankton samples
included typical warm water species: Pleuromamma gracilis, P. abdominalis, Tessarobrachion oculatum, and
spawning stage of Euphausia pacifica. The species composition of mesozooplankton at the study area during
the spring of 2005 suggests that the water supporting the intense algal bloom was observed penetrated from
Western Subarctic Gyre. It is possible that during this time, the large amount of dead salps and heteropods
provided a strong input of nutrients to the euphotic zone, which resulted in the observed algal bloom in the study
area, although such a phenomena has not been detected previously in this area.
PICES XV
S9-2777
Poster
Application of biotechnology for monitoring harmful algae in marine food resources
Lalit P. Chaudhari, A.G. Bhole, S.P. Yavalkar and N.K. Choudhary
Institute for Sustainable Development and Research, B-1-8, Narayan Pujari Nagar, Worli, Mumbai, 400018, India
E-mail: [email protected]
Phytoplankton blooms, micro-algal blooms, toxic algae, red tides, and harmful algae, are all terms for naturally
occurring phenomena. About 300 hundred species of micro-algae are reported at times to form mass
occurrences, these so called blooms. Nearly one fourth of these species are known to produce toxins. Harmful
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algae and their toxins pose a growing global problem for human health, aquaculture, fisheries, seafood trade,
tourism and recreation, and the aquatic environment at a time when human reliance on coastal zones for food,
recreation and commerce is also expanding. In developing countries, seafood often constitutes an important or
even the sole source of food and protein, especially in coastal areas. With the increasing problems of over
fishing, aquaculture may become an increasingly important alternative for the supply of seafood. However, to
minimize the risk of sea-food poisonings and the risk of major economic losses due to fish kills, it is important
to establish adequate surveillance programmes, and to control the quality of the seafood products; this will
often require expert assistance from countries which have longstanding experience in biotechnological
applications in the marine sector. This study focuses on development of the plan for monitoring and
management of harmful algal blooms in coastal waters for aquaculture using biotechnology from experiences in
India. The study also evaluates taxonomy and biogeography of harmful algae for increasing aquaculture
productivity. This study signifies that the application of biotechnologies is essential for aquatic food production
with special focus on eco-physiology, biochemical and pharmacological aspects of algal toxins.
PICES XV
S9-3198
Poster
Growth and toxicity of Pseudo-nitzschia cuspidata from the U.S. Pacific Northwest
Maureen E. Auro1, William P. Cochlan1 and Vera L. Trainer2
1
2
Romberg Tiburon Center for Environmental Studies, San Francisco State University, 3152 Paradise Drive, Tiburon, CA, 94920-1205,
U.S.A. E-mail: [email protected]
Northwest Fisheries Science Center, NOAA Fisheries, 2725 Montlake Blvd. E., Seattle, WA, 98112, U.S.A.
The toxigenic diatom, Pseudo-nitzschia cuspidata, is commonly found in the Juan de Fuca Eddy region of the
U.S. Pacific Northwest. Isolates collected during Fall surveys of the ECOHAB-PNW project during 2004 and
2005 were examined in non-axenic, semi-continuous, batch cultures enriched with either 40 M nitrate, 40 M
ammonium or 20 M urea as the sole nitrogen source. Experiments conducted at high (120 µE·m-2·s-1) and low
(40 µE·m-2·s-1) photosynthetic photon flux densities (PPFDs), demonstrate that P. cuspidata grew significantly
faster at high PPFD, but showed no preference for one nitrogen source over the other. However at low PPFD,
cells maintained on urea grew faster than those on either nitrate or ammonium. Exponential growth rates
(determined using cell abundance over time) and particulate domoic acid (using ELISA) did not significantly
differ as a function of the nitrogen growth substrate. In contrast to other Pseudo-nitzschia species where DA is
generally enhanced during stationary phase, the particulate DA per cell for P. cuspidata averaged 51% greater
during exponential growth on nitrate compared to stationary growth, regardless of PPFD. Growth on urea at
low light showed a similar reduction in particulate DA during stationary phase. These results demonstrate the
capability of this diatom to grow and produce DA on both oxidized and reduced N substrates. Our field
observations have generally found greatest P. cuspidata abundances in the nitrate-rich, upwelled waters of the
Juan de Fuca Eddy, whereas elevated urea concentrations have not been observed in this and adjacent coastal
regions.
PICES XV
S9-2895
Oral
Noctiluca scintillans with endosymbiont, successful red tide species in SE Asian waters
Ken Furuya1, Takuo Omura2 and Thaithaworn Lirdwitayaprasit3
1
2
3
Department of Aquatic Bioscience, The University of Tokyo, Yayoi, Bunkyo, Tokyo, 113-8657, Japan
E-mail: [email protected]
Asian Natural Environmental Science Center, The University of Tokyo, Yayoi, Bunkyo, Tokyo, 113-8657, Japan
Department of Marine Science, Chulalongkorn University, Phyathai Rd., Bangkok, 10330, Thailand
Noctiluca scintillans containing the photosynthetic endosymbiont, Pedinomonas noctilucae, is the most frequent
causative organism of red tides in Southeast Asian waters. Clonal cultures of N. scintillans isolated from
Thailand and Philippine waters were of two types: one requiring an external food supply and the other not
requiring an external food supply. The latter grew photoautotrophically for generations, but they also fed on
foods. The P-E relationship was characterized by low light intensity of saturation and either absence or weak
photoinhibition, showing efficient utilization of light. Thus, P. noctilucae assures a supply of organic matter to
the host, and facilitates survival of N. scintillans under food limitation. The organism forms perennial red tides
in Manila Bay, Philippines, and since 2003 occasionally covering almost the whole area. A field survey was
conducted in March 2004, when N. scintillans formed red tides in the whole bay with surface chlorophyll-a
reaching up to 522 µg L-1. This predominance was not explained by growth activity or physical accumulation.
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In-situ specific growth rate (0.16 d-1), as determined by cell cycle analysis at a fixed station, was likely too low
to account for its dominance in the bay, where potentially fast growing diatoms co-existed. Many cells of
N. scintillans conducted active grazing, and preferred large particles mainly secondary dominant species. Based
on these observations, we postulate a hypothesis that despite the low growth rate the endosymbiont provides
competitive advantages for N. scintillans, and that once it becomes dominant, its active grazing prevents
population growth of co-existing phytoplankton.
PICES XV
S9-2958
Oral
Physical oceanic conditions on summer time related with harmful algal blooms around
the Korean Peninsula
In-Seong Han, Hee-Dong Jeong and Ki-Tack Seong
National Fisheries Research and Development Institute, 408-1, Shirang-ri, Gijang-up, Gijang-gun, Busan, 619-902, Republic of Korea
E-mail: [email protected]
Outbreaks of harmful algal blooms (HABs) have frequently occurred in the Korean waters, and have caused
economic losses in the coastal breeding grounds. These annual outbreaks were usually accompanied by distinct
physical, biological and environmental conditions in Korean waters. From the results of spatial scale, maximum
density and duration, relatively large-scale outbreaks of HABs appeared in 1995, 1997, 1999, 2001, 2002 and
2003. To clarify the relationship between these HAB outbreaks and physical oceanic environmental factors, we
examined the horizontal and vertical distribution of temperature, coastal temperature variation, behavior of low
saline water, magnitude of Kuroshio volume transport at upstream areas and related factors. Relatively lower
coastal temperature in August around the South Sea correspond with the outbreak of HABs. To clarify the
relationship between HAB outbreaks and stratification around the South Sea, we also examined the temperature
profiles in this region. Weaken stratification usually corresponded with HAB outbreaks. We also considered
that relatively weaken stratification plays an important role in nutrient supply from lower layers. Moreover, we
found that the relationship between the behavior of low saline water originated from Changjian, larger Kuroshio
volume transported upstream and HAB outbreaks. There are surely some exceptions to this finding because
HAB outbreaks have complex causes including biological, environmental and physical factors. To gain a better
undertstanding of such HAB outbreaks, physical oceanographic factors must be included in HAB research.
PICES XV
S9-3035
Oral
Nutrient and phytoplankton dynamics in Hong Kong and their response to sewage
abatement
Paul J. Harrison, Alvin Ho, Kedong Yin and Xu Jie
AMCE Program, Hong Kong University of Science and Technology, Hong Kong, PR China. E-mail: [email protected]
The Hong Kong government has a 15-year time series of ambient nutrients and phytoplankton dynamics in
Victoria Harbor and its vicinity. Ammonium and phosphate are good indicators of sewage inputs where
screened, untreated sewage was discharged into the harbor until 2001. Total inorganic nitrogen, nitrate and
chlorophyll have been increasing and dissolved oxygen has decreased during this 15-year period. The
phytoplankton biomass was usually dominated by fast growing centric diatoms and chlorophyll ranged from 5 to
20 ug/L. During the last four years, 70% of the sewage is now receiving primary treatment at a sewage
treatment plant located several kilometers away. We have been following the recovery in Victoria Harbor with
a focus on nutrients, dissolved oxygen, chlorophyll and phytoplankton dynamics. Ammonium, phosphate and
total inorganic nitrogen concentrations have declined since sewage treatment has begun. However, increasing
Chl-a and decreasing dissolved oxygen in the bottom waters near the new sewage treatment plant indicates that
the potential eutrophication problem may have been moved from the harbor to the vicinity of the sewage
treatment plant.
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PICES XV
S9-3032
Oral
HAB occurrences and eutrophication in the Seto Inland Sea, Japan
Ichiro Imai1, Mineo Yamaguchi2 and Yutaka Hori3
1
2
3
Graduate School of Agriculture, Kyoto University, Kitashirakawa, Sakyo, Kyoto, 606-8502, Japan. E-mail: [email protected]
National Research Institute of Fisheries and Environment of Inland Sea, Fisheries Research Agency, Hatsukaichi, Hiroshima, 739-0452,
Japan
Fisheries Technology Institute, Minamifutami, Futami, Akashi, Hyogo, 674-0093, Japan
The Seto Inland Sea is the largest enclosed coastal sea in Japan and is also a major fishing ground including
aquacultural farms of fish, bivalves and seaweeds. Incidents of red tides had dramatically increased in
frequency and scale in the Seto Inland Sea along with serious eutrophication in 1960s and 1970s. The
maximum annual incidents of 299 was recorded in 1976, and these incidents showed a clear decreasing trend
reaching about 100 per year in late 1980s due to new regulations; this level has been subsequently kept with the
level of nutrients supporting red tide occurrences. The “Law Concerning Special Measures for Conservation of
the Environment of the Seto Inland Sea” was legislated in 1973 and industrial loading was decreased to half of
the level of 1972. The important red tide organisms causing huge fishery damages by fish-kill are Chattonella
antiqua, C. marina, C. ovata and Heterosigma akashiwo (Raphidophyceae) and Karenia mikimotoi and
Cochlodinium polykrikoides (Dinophyceae). The maximum fishery damage (death of 14.2 million yellowtails)
was 7.1 billion yen (about $60 million US) caused by C. antiqua in Harima-Nada in 1972. In 1988, a novel red
tide dinoflagellate species Heterocapsa circularisquama appeared for the first time, and has recurrently killed
both free-living and farmed bivalves, with the highest damage of 3.9 billion yen attributed to cultured oysters in
Hiroshima Bay in 1998. Among the important red tide organisms, C. antiqua, H. circularisquama and
C. polykrikoides are rated to be extremely harmful species that can easily reach the warning level of fishery
damages by consuming only small amounts of nutrients. In toxic blooms, the dinoflagellate Alexandrium
tamarense has become dominant in the Seto Inland Sea in the spring season, and has made short-necked clams
and cultured oysters toxic almost every year. The existence of abundant cysts of Alexandrium spp. in sediments
indicates the establishment of this toxic species in the Seto Inland Sea.
PICES XV
S9-3091
Invited
The role of viruses on harmful algal bloom dynamics
Janice E. Lawrence
Biology Department, University of New Brunswick, P.O. Bag Service 45111, Fredericton, NB, E3B 6E1, Canada
E-mail: [email protected]
Viral infection has only recently been appreciated for its role in influencing the population dynamics of
phytoplankton. It is now recognized that infections become especially important during bloom conditions since
the rate of infection is dependent on the density of host cells. Heterosigma akashiwo is a harmful algal bloomforming species against which numerous distinct viruses have been isolated. These lytic HaVs are unevenly
distributed throughout marine ecosystems and therefore impose dynamic controls on host abundance, and spatial
and temporal distribution. High abundances of HaVs are found in coastal sediments; evidence suggests they
accumulate in the benthos via sinking, infected cells. The presence of infectious viruses in coastal sediments
has several implications on past, present and future harmful algal blooms, all of which will be discussed. Each
type of HaV is distinct with respect to lytic cycle length, host range and burst size. These infection
characteristics interact with the physiology and ecology of the host alga to influence the rate of propagation of
infection throughout a bloom. The result is a complex, dynamic role of viruses in shaping the formation,
demise, and genetic compositions of harmful algal blooms. Isolating and characterizing more novel algal
viruses is important for further developing our understanding of algal-virus interactions, and therefore
phytoplankton population dynamics.
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PICES XV
S9-2950
Oral
Viral impact on the population dynamics of HABs
Keizo Nagasaki, Yuji Tomaru, Hiroyuki Mizumoto, Yoko Shirai and Yoshitake Takao
National Research Institute of Fisheries and Environment of Inland Sea, Fisheries Research Agency, Hatsukaichi, Hiroshima, 739-0452,
Japan. E-mail: [email protected]
Recently, viral infection is regarded as one of the most important factors controlling the population dynamics of
phytoplankton. To scrutinize the ecological relationship between the bloom-forming dinoflagellate Heterocapsa
circularisquama and its infectious viruses, we conducted field surveys in western Japan. About 88% of
H. circularisquama cells harbored small virus-like particles at the peak of the bloom in summer 2001; then, it
was followed by a sudden bloom termination. Further, occurrence of H. circularisquama blooms was
accompanied with specific increases in abundance of its infectious viral agents. By northern dot-blot analysis,
~96% of the clonal viral agents isolated through the surveys positively reacted with a molecular probe specific
to HcRNAV (H. circularisquama RNA virus); hence, viral impacts observed in these field surveys were
considered to be largely due to HcRNAV infection. HcRNAV comprises two ecotypes having complementary
intraspecies host ranges to each other (type UA and CY); they showed different dynamics presumably reflecting
the fluctuation patterns of their suitable host ecotypes in situ. Recent studies revealed the intraspecies host
specificity of HcRNAV is determined by the upstream events including specific binding of virus particle to host
cell surface receptor. Another point of interest is that the amount of HcRNAV accumulated in the sediment just
prior to the host’s blooming season may be a significant factor in determining the size or term length of H.
circularisquama blooms. Thus, HcRNAV infection is assumed to be one of the remarkable factors affecting the
population dynamics of H. circularisquama; both its biomass and clonal composition.
PICES XV
S9-3066
Oral
Iron and harmful algal blooms
Kanako Naito and Ichiro Imai
Graduate School of Agriculture, Kyoto University, Kyoto, 606-8502, Japan. E-mail: [email protected]
Iron is an essential element for the biochemical and physiological functioning of microalgae. However, the
mechanism of iron uptake by eukaryotic microalgae is not yet fully understood because of the intricate iron
chemistry of natural seawater and the difficulty in cultivation of axenic microalgae under uncontamination.
Dissolved iron fractions consist largely of colloidal hydrolysis species and most of those are bound by organic
ligands in natural waters. As a result of above-mentioned iron speciation, the concentrations of directly
bioavailable iron species are extremely low in natural waters. The growths of the principal species of red tide
microalgae including the harmful algal species were examined using a newly developed artificial synthetic
medium in the presence of different iron species. The present study demonstrated that particulate FePO 4 and
FeS were bioavailable for the growth of the dinoflagellates Heterocapsa circularisquama and Karenia
mikimotoi, and the cryptophyte Rhodomonas ovalis. And the differences in concentration of organic ligands in
each medium caused the changes of the growth (maximal growth yield and specific growth rate) of red tide
microalgae examined. Furthermore, it is confirmed by Chrome azurol S assay that 14 species of red tide
microalgae produced strong iron-binding ligands like siderophores ( > 0.1 µM), at the early stationary growth
phase under iron-limiting conditions. These results suggest that the iron speciation may be an important role in
controlling the harmful algal bloom formation in coastal water. We here suggest that red tide microalgae have
specific strategies to utilize iron under dissolved inorganic iron limitation.
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PICES XV
S9-2885
Oral
Long-term changes in the phytoplankton of the coastal waters off Vladivostok (the
north-western part of the Japan/East Sea)
Tatiana Yu. Orlova and Inna V. Stonik
Institute of Marine Biology, FEBRAS, 17 Palchevskogo Street, Vladivostok, 690041, Russia. E-mail: [email protected]
The qualitative and quantitative compositions of phytoplankton, as well as analysis of the blooms caused by
mass development of potentially toxic algae, have been carried out in the coastal waters off Vladivostok. This
area is exposed to continuous anthropogenic influence due to input urban and agricultural runoff. The following
trends in the composition and distribution of the phytoplankton were revealed: the total density and biomass
increased; the density of diatom Skeletonema costatum increased, leading to a decrease in microalgae species
diversity; the density of the non-diatom component of the phytoplankton increased. Twelve species causing red
tides were observed; these species belong to four taxonomic groups of phytoplankton: dinoflagellates, diatoms,
raphidophytes and euglenophytes. A total twenty-three red tide events were observed during the study period.
Dinoflagellates were the most common bloom-forming algae, and caused more than half of the total red-tide
events. Noctiluca scintillans has caused most of the visible red tides. Obtained data indicate that in the past two
decades there has been an apparent increase in the frequency, intensity and duration of microalgal blooms in the
coastal waters off Vladivostok. The algae that cause the most concern are the genera Pseudo-nitzschia,
Dinophysis, Prorocentrum and Heterosigma, known for their toxicity and ability to cause harmful algal blooms.
PICES XV
S9-3182
Poster
Population dynamics and overwintering of the shellfish killing dinoflagellate
Heterocapsa circularisquama in the western coastal Sea of Japan
Tomotaka Shiraishi1, Kiyohito Nagai2, Jyoji Go2, Takashi Yamamoto2, Michinori Yamakawa3, Misa Inoue4,
Isao Kuriyama4, Seiya Taino5, Tetsu Ishikawa5, Yoshihiro Hayashi5, Shingo Hiroishi6 and Ichiro Imai1
1
2
3
4
5
6
Laboratory of Marine Environmental Microbiology, Division of Applied Biosciences, Graduate School of Agriculture, Kyoto University,
Kitashirakawa-Oiwakecho, Sakyoku, Kyoto, 606-8502, Japan. E-mail: [email protected]
Mikimoto Pearl Research Laboratory, Mie, 517-0403, Japan
Nantocho Fisheries and Seeding Center, Mie, 516-1306, Japan
Fisheries Research Division, Mie Prefectural Science and Technology Promotion Center, Owase, Mie, 519-3602, Japan
Kochi Prefectural Fisheries Experimental Station, Kochi, 785-0167, Japan
Fukui Prefectural University, Fukui, 917-0003, Japan
In Japanese western coastal waters, Heterocapsa circularisquama is the most noxious dinoflagellate to shellfish
aquaculture due to its formation of red tides and the accompanying mass mortalities of both natural and cultured
bivalves such as oysters, short-necked clams, mussels and pearl oysters. In order to reduce the negative impacts
by H. circularisquama, it is important to comprehend its population dynamics. Sensitive monitoring is
presented here by employing the indirect fluorescent antibody technique using monoclonal antibody, and
overwintering was investigated in southwestern waters. Samplings were made several times per month in Ago
Bay, Mie, Japan from April 2001 to December 2005, once a month in two bays of Mie, from August 2003 to
December 2005, and several times a month in Uranouchi Inlet, Kochi, Japan, from February 2004 to July 2006.
Vegetative cells of H. circularisquama were generally detected from late spring to late autumn, and the cell
density increased (maximum 2.33 x 106 cells l-1) during summer in three bays of Mie. It is confirmed that
H. circularisquama causes red tides in summer in western coast of Japan. Vegetative cells were not detected
every year from winter to early spring. However in Uranouchi Inlet, Kochi, vegetative cells have been detected
throughout the year. These detected cells were regarded to be overwintering and/or overwintered cells.
Furthermore, the cultured strains isolated from Uranouchi Inlet in March 2004 were identified as
H. circularisquama. These results indicate that H. circularisquama can overwinter in the stage of vegetative
cell in warmer areas such as Uranouchi Inlet in Japan.
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PICES XV
S9-3180
Invited
Harmful algal blooms: Global spreading or global synchrony?
Theodore J. Smayda
Graduate School of Oceanography, University of Rhode Island, Kingston, RI, 02881, U.S.A.
E-mail: [email protected]
A harmful algal bloom (HAB) epidemic is in progress in global coastal waters and inland seas characterized by
remarkable and unusual parallel events relative to the historical record. Collectively, the patterns and impacts of
this phenomenon suggest that a major change in phytoplankton bloom dynamics, flagellate species in particular,
is occurring that may be symptomatic of an emergent and widespread disequilibrium in phytoplankton dynamics
in the sea. Four theories have been proposed to explain the HAB epidemic, three of which deal with
anthropogenic habitat modification - the ‘changing environment’ theories - while the fourth - the ‘emigration’
theory - attributes the HAB increase to the geographic dispersal of HAB species vectored in ballast water and
shellfish transplantation. The nutrient stimulus theory posits that the increased frequency in HABs is being
stimulated by anthropogenic nutrient enrichment of coastal waters, including changes in nutrient ratios which
influence species selection. Harmful blooms at aquacultural and fish-farming sites, often resulting in severe
financial loss, have been attributed to waste-nutrient excretions. Climate change by altering climatology and
driving physical habitat modifications that favor HABs has also been invoked. The merits of the ‘emigration’
and ‘changing environment’ stimulation theories will be evaluated applying a comparative ecosystem analysis in
combination with ecophysiological assessments of representative bloom-species. The question underlying the
analysis will be whether the HAB epidemic is primarily the coincidence of isolated, regional blooms developing
in response to different local causes, or whether there is a more profound global synchrony in this phenomenon.
PICES XV
S9-2864
Poster
Detecting red tides in the eastern Seto Inland Sea with satellite ocean color imagery
Wataru Takahashi1, Hiroshi Kawamura2, Takuo Omura3 and Ken Furuya4
1
2
3
4
Japan NUS Co., Ltd., Loop-X Bldg., 8F 9-15 Kaigan 3-Chome, Minato-Ku, Tokyo, 108-0022, Japan. E-mail: [email protected]
Center for Atmospheric and Oceanic Studies, Tohoku University, 6-3 Aramaki-aza, Aoba-Ku, Sendai, 980-8578, Japan
Asian Natural Environmental Science Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-Ku, Tokyo, 113-8657, Japan
Laboratory of Aquatic Biology and Environmental Science, Graduate School of Agricultural and Life Sciences, The University of Tokyo,
1-1-1 Yayoi, Bunkyo-Ku, Tokyo, 113-8657, Japan
A multi-spectral classification scheme is proposed to identify areas with red tides through the satellite ocean
color imagery by the Sea-viewing Wide Field-of-view Sensor (SeaWiFS). The eastern Seto Inland Sea, where
serious red tides frequently occur in Japan, was studied. Colors of the water around a red tide or those of water
before/after a red tide are referred to as “background ocean colors (BOCs)”, and BOCs are estimated as the
monthly mean of normalized water-leaving radiances (nLw) with 0.01 degree spatial resolution with SeaWiFS
imagery. Criteria for detection of red-tide pixels are established from analyses of the characteristics of nLw (at
443, 490, 510, and 555nm) anomalies from BOCs and the nLw spectra together with the red-tide records in
Osaka Bay. The criteria developed from the SeaWiFS data appear to be robust; the SeaWiFS data used for the
criteria indicated 81% of water with a red tide, and 95% of water without it. Probability of red-tide detection is
high in eastern Osaka Bay and in the coastal waters of the northern Harima Nada. In the innermost part of
Osaka Bay, monthly probability of red-tide detection (MPRD) does not go below 20% in any month. On the
other hand, in Harima Nada, MPRD is almost zero from November to April. These distribution patterns of
identified red tides in time and space are well supported by previous biogeographic investigations. The results
suggest that the scheme is appropriate to detect red tides for optically complex coastal water of the eastern Seto
Inland Sea.
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PICES XV
S9-2998
Oral
Does dam construction induce harmful algal blooms?
Tamiji Yamamoto and Gen Hatta
Graduate School of Applied Biological Science, Hiroshima University, Higashi-Hiroshima, 739-8528, Japan
E-mail: [email protected]
A numerical model was constructed to elucidate whether flattening of river discharge and trapping of silica by
dam construction could induce harmful algal blooms. Two harmful algal bloom species, the paralytic shellfish
poisoning dinoflagellate Gymnodinium catenatum and the fish-killing raphidophyte Chattonella antiqua were
used as representatives of harmful algae, and a diatom Skeletonema costatum was used as a norm. G. catenatum
showed the maximum cell yield in continuous nutrient supply mode and C. antiqua also showed less response to
pulsed discharge mode, while S. costatum showed the maximum cell yield in pulsed discharge mode with large
fluctuations. In simulations of mixed-species, a pulsed nutrient supply with an intermediate frequency interval
led to a longer period of coexistence than continuous nutrient supply, showing consistency with the Intermediate
Disturbance Hypothesis. Reduction of silicate supply depressed the S. costatum cell density and made the
coexistence period of these three species much longer. These model calculations imply that flattening of river
discharge and trapping silica by dam construction may induce harmful algal blooms. In other words, temporal
heterogeneity in estuaries could be a factor maintaining phytoplankton species diversity.
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