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2012 Best Presentation Award Page
Effects of natural and anthropogenic stressors in the North Pacific ecosystems: Scientific challenges and possible solutions
Abstracts
Oral (S1-8663), Science Board Session
The Ocean Health Index: Global assessment and future priorities
Benjamin S. Halpern1,2
1
National Center for Ecological Analysis and Synthesis, 735 State St. Santa Barbara, CA, 93101, USA
E-mail: halpern@nceas.ucsb.edu
2
Center for Marine Assessment and Planning, UC Santa Barbara, Santa Barbara, CA, 93106, USA
Recent development of the Ocean Health Index offers a flexible, quantitative and comprehensive tool for assessing
the condition of the natural and human dimensions of marine ecosystems. The Index assesses the sustainable
delivery of 10 widely-held public goals for healthy oceans, using measures of the current status, relative to a
reference point, and likely future state to quantify these goals. I will present results and lessons learned from the
initial global assessment and discuss future priorities and opportunities to refine and expand the Index.
Poster (S1-8), Science Board
Session
Decrease of surface water nutrient concentration and nutrient flux from the sediment in
Harima-Nada, Eastern Seto Inland Sea, Japan
Fisheries Technology Institute, Hyogo Prefectural Technology Center for Agriculture, Forestry and Fisheries, 22-2 Minami-Futami, Akashi, Hyogo, 674-0097, Japan
3
Kagawa Prefectural Fisheries Experimental Station, Yashima-Higashi, Takamatsu, Kagawa, 761-0111, Japan
4
Seto Inland Sea Regional Research Center, Kagawa University, Takamatsu, Kagawa, 760-8521, Japan
From the 1960s onwards, when Japan achieved high economic growth, the Seto Inland Sea was heavily eutrophicated due to serious water pollution by industrial effluent and urban wastewater. The result was a high
occurrences of red tides. Since the Law for Conservation of Environment of the Seto Inland Sea was enacted
in 1973, water quality has gradually improved. Since 1990, however, nutrient concentrations in seawater have
decreased considerably, which has raised a new problem. With the recent Dissolved Inorganic Nitrogen (DIN)
decrease, Nori (Porphyra) yield has declined. The fisheries yield of species such as sardine and short-neck clam
has also been affected negatively. We investigated the causes of the nutrient decrease by examining the nutrient
concentration of surface water in the eastern part of the Seto Inland Sea. We also surveyed the content of organic
matter in the surface sediments and nutrient upward fluxes from the sediments across the overlying water-sediment
interface. Our results showed that the organic content and the horizontal distributions in surface sediments were
similar to those of 30 years ago. On the other hand, the nutrient fluxes were quite low compared with fluxes
examined about 10 and 30 years ago in the same area. In this study, we suggest that the decrease of nutrient
upward flux is an important factor for the recent nutrient decrease in the surface seawater in the Seto Inland Sea.
Oral (BIO-P-8652), BIO Paper Session
Spatial, temporal and dietary overlap between harbour seals and fisheries in Erimo,
Japan: Conflict at sea?
Graduate School of Environmental Science, Hokkaido University, 3-1-1 Minato-cho, Hakodate, Hokkaido, 041-8611, Japan.
E-mail: tcyhui@ees.hokudai.ac.jp
2
Faculty of Fisheries Sciences, Hokkaido University, 3-1-1 Minato-cho, Hakodate, Hokkaido, Japan 041-8611
3
Field Science Center for Northern Biosphere, Hokkaido University, 3-1-1 Minato-cho, Hakodate, Hokkaido, Japan 041-8611
4
Obihiro University of Agriculture and Veterinary Medicine, Kuril Harbor Seal Research Group, Obihiro, Hokkaido, Japan 080-0835
5
Pinniped Research Group, Obihiro, Hokkaido, Japan 080-0835
The harbour seal is an endangered species in Japan. Since protection began in the mid-1980s, the total number of
harbour seals in Japan has been rebounding. With the increase in seal numbers, increased conflict with fisheries
(especially salmon fixed-net fisheries) has occurred through depredation and the belief that seals compete with
fisheries for prey. However, competition is unlikely if seals and fisheries take mostly different prey species, obtain
prey from different areas or at different times. We studied the foraging ecology of harbour seals in Erimo, site of
the largest population of harbour seals in Japan, from 2011-2012. We deployed satellite tags in July 2011 (n=1)
and June 2012 (n=4). The foraging ranges (average size of 90% ranges was 30 km2) of all tagged seals overlapped
at least one salmon fixed-net (5 total in Erimo). We collected seal scats in summer, fall and spring, identified prey
items from hard parts retrieved and compared the results with local fisheries data. Of the 39 scats with identifiable
prey remains analysed, none contained salmon remains. The seals’ diet differed greatly from fisheries catches.
Gadoids (FO=55%), snailfish (FO=35%) and sculpins (FO=30%) were the main prey items found in seal scats. In
contrast, salmonids were the main species caught by fisheries, accounting for >50% of catches by mass, followed
by gadoids (15%). Resource overlap between seals and fisheries was <0.01 (Pianka index) in summer, fall and
spring. As such, we conclude that competition is highly unlikely between harbour seals and fisheries in Erimo.
Poster (BIO-P-4),
BIO Topic Session
Seasonal occurrence of mesopelagic fish larvae in the onshore side of the Kuroshio off
southern Japan
Chiyuki Sassa1 and Yuichi Hirota2
1
Graduate School of Environmental Science, Hokkaido University, 3-1-1 Minato-cho, Hakodate, Hokkaido, 041-8611, Japan.
E-mail: tcyhui@ees.hokudai.ac.jp
2
National Research Institute of Fisheries Science, Fisheries Research Agency, 2-12-4 Fukuura, Kanazawa-ku, Yokohama, Kanagawa, 236-8648, Japan
Information on the annual reproductive cycle of mesopelagic fishes has been limited in the western North Pacific, despite their ecological importance.. The Kuroshio region is an important spawning ground for various
species of mesopelagic fishes. To describe the reproductive seasonality, we examined the seasonal occurrence
patterns of the mesopelagic fish larvae on the continental slope in Tosa Bay which is strongly influenced by the
Kuroshio, based on monthly samples collected from January 2001 to December 2004. In total, 2,558 mesopelagic
fish larvae occurred, with peak abundance during May to June. Larvae of the dominant families Myctophidae,
Sternoptychidae, Gonostomatidae, Bathylagidae, and Phosichthyidae were represented by 26 species (or types)
belonging to 18 genera. The twelve most abundant species accounted for 96.9% of the total catch. The seasonal
occurrence patterns of these larvae were categorized into five groups in accordance with physical properties of the
water column: Winter (Notoscopelus japonicus and Lipolagus ochotensis); Spring (Symbolophorus evermanni and
Maurolicus japonicus); Early summer (Myctophum asperum and Diaphus stubby type); Autumn (Lampanyctus sp. A, Cyclothone spp., and Sigmops gracile); and Year-round (Vinciguerria nimbaria, Diaphus slender type, and
Diogenichthys atlanticus) groups. No significant difference was observed in the months of peak abundances of
these larvae during the four years, suggesting that each species has a fixed seasonal pattern of reproduction. The
various patterns of seasonal occurrence would result in seasonal habitat segregation of the larvae among species,
possibly reducing intraspecific competition for food resources in the oligotrophic waters of the Kuroshio.
Oral (FIS-P-8501), FIS Paper Session
Spatial modeling of the potential fishing zone of Japanese common squid in coastal waters
of southwestern Hokkaido, Japan
Xun Zhang, Sei-Ichi Saitoh and Toru Hirawake
Laboratory of Marine Environment and Resource Sensing, Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1 Minato, Hakodate, Hokkaido, 041-8611, Japan. E-mail: xun@salmon.fish.hokudai.ac.jp
Japanese common squid (Todarodes pacificus) is one of the most commercially important fished species in the southwestern Hokkaido coastal region, Japan. Jigging fishing in this region usually occurs at nighttime from June
to December and the lights used for fishing can be detected by DMSP (Defense Meteorological Satellite Program)
OLS (Operational Linescan System). We used three years of data (2000, 2001 and 2002) on daily fishing vessel
distribution derived from the nighttime DMSP/OLS images to identify the presence and absence of Japanese
common squid assemblages along the southwestern Hokkaido coastal region. Corresponding environmental factors
were considered to explain squid distribution, including bathymetry, SST (sea surface temperature), chlorophyll a concentration and Kd490 (diffuse attenuation coefficients of downwelling irradiance at 490-nm). We tested three
different models to predict squid distribution: GAM (Generalized additive model), GLM (Generalized linear
model) and BRT (Boosted regression trees). Model performance was validated and compared based on DMSP/OLS data of 2003. The comparisons indicated that the BRT was better than GAM and GLM. Results from the BRT
showed that potential fishing zones were closely correlated with the depth of the water. SST and chlorophyll a highly
contributed to squid occurrence as well, while Kd490 which is related to the transparency of the water was less
associated with the distribution. In addition, we applied BRT to detect monthly potential fishing zones between
2004 and 2009 and mechanisms potentially responsible for the spatial and temporal variation.
Poster (FIS-P-12), FIS Paper Session
High dispersal of moray eel larvae to the open ocean: Early life history estimated from
ocean-wide distribution patterns
Atsushi Tawa1, Taku Yoshimura2 and Noritaka Mochioka1
1
Laboratory of Fisheries Science, Graduate school of Bioresources and Bioenvironmental Science, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka, 812-8581, Japan. E-mail: a-tawa@hotmail.co.jp
2
Seikai National Fisheries Research Institute, Fisheries Research Agency, 1551–8 Taira, Nagasaki, 851–2213, Japan
Information on larval fish ecology and early life history is very important for resource management and the
conservation of marine biodiversity. In addition, larval recruitment of demersal fishes determines adult distribution
patterns. Moray eels are important elements in tropical to temperate coastal ecosystems due to their role as a
higher-level predator. Some species are reported to spawn in coastal areas, however, their larval ecology and
early life histories are mostly unknown. Therefore, we first examined the distribution patterns of the leptocephali
of different species or types in the Indo-Pacific to estimate the general early life history of moray eels. A total
of 914 specimens of muraenid leptocephali were collected across a wide range from the western North Pacific
to the western Indian Ocean. They were separated into at least 75 species based on morphology and genetic
analysis. All species were distributed in the open ocean. The leptocephali of two species, Gymnothorax minor and G. pseudothyrsoideus were also collected from coastal areas. The specimens collected at moderate distances
from coastal areas were small to large size. But the specimens collected at long distances from coastal areas were
all large size. Therefore, we estimated that small leptocephali born in the coastal areas were dispersing widely
across the open ocean, and then their leptocephali returned to the coastal area after growing. Further research is
necessary to clarify their dispersal mechanisms and the timing of when they leave the open ocean, and this will be
investigated using otolith microchemistry with LA-ICP-MS.
Oral (S10-8429), BIO/MEQ/FUTURE Topic Session
The combined effects of elevated carbon dioxide concentration and temperature on the
early development stage of olive flounder Paralichthys olivaceus
Kyung-Su Kim1, JeongHee Shim2 and Suam Kim1
1
Department of Marine Biology, Pukyong National University, Busan, Korea, 608-737
2
National Fisheries Research and Development Institute, 152-1 Haeanro, Gijang-Up, Gijang-Gun, Busan, 619-705, R Korea. E-mail: ks-kim@pknu.ac.kr
Due to a high warming rate and possible local acidification in Korean waters, fishermen and aquaculturists require
scientific knowledge on the biological reactions to environmental change for proper management of fisheries. To
examine the effects of ocean warming and acidification on the early growth of olive flounder (the most popular
fish species in the aquaculture industry), we conducted experiments with larvae reared under different conditions:
combination of 400 and 1500 ppm atmospheric CO2 and 18°C and 22°C of seawater temperature. Fertilized eggs
of flounder were hatched in the system and larvae were reared for 4 weeks. After 4 weeks, the body weight and
length were measured to differentiate the Specific Growth Rate at different rearing conditions. Bone structure and
some sensor systems such as the lateral-line and surface porse were examined to compare normal and acidityaffected
fish using a scanning electron microscope.
Poster (S10-2), BIO/MEQ/FUTURE Topic Session
Iron as a triggering factor for harmful dinoflagellate blooms
Department of Environment Sciences, Faculty of Life and Environmental Sciences, Prefectural University of Hiroshima, Shobara, Hiroshima, 727-0023, Japan. E-mail: naito@pu-hiroshima.ac.jp
2
National Research Institute of Fisheries and Environment of Inland Sea, Fisheries Research Agency, 2-17-5 Maruishi, Hatsukaichi, Hiroshima, 739-0452, Japan
3
Laboratory of Marine Biology (Plankton Laboratory), Division of Marine Bioresource and Environmental Science, Graduate School of Fisheries Sciences, Hokkaido University, Hakodate, Hokkaido, 041-8611, Japan
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 in uncontaminated conditions.
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 the above mentioned iron speciation, the concentrations of directly
bioavailable iron species are extremely low in natural waters. To clarify utilization of the iron for the harmful
algal species, we examined the growth experiments using a newly developed artificial synthetic medium in
the presence of different iron species. The present study demonstrated that particulate FePO4 and FeS were
bioavailable for the growth of the dinoflagellates Cochlodinium polykrichoides, Heterocapsa circularisquama and
Karenia mikimotoi. The differences in concentration of organic ligands in each medium caused the changes of the
growth (maximal growth yield and specific growth rate) of harmful algae examined. These results suggest that
the iron speciation has significant effects on controlling the harmful algal bloom formation in coastal areas. We
point out the possibility that iron is a triggering factor for harmful dinoflagellate blooms showing the expansion
in the North Pacific Ocean.
Invited (S3-8397), POC Topic Session
Interannual to decadal variability of the Gulf Stream and Kuroshio Extension jets
Yoshi N. Sasaki1, Shoshiro Minobe1 and Niklas Schneider2
1
Graduate School of Science, Hokkaido University, Sapporo, 060-0810, Japan E-mail: sasakiyo @mail.sci.hokudai.ac.jp
2
IPRC and Department of Oceanography, University of Hawaii at Manoa, Honolulu, 96822, USA
The Gulf Stream and Kuroshio Extension jets not only transport nutrients and biota downstream but also act a barrier for mixing subtropical and subarctic water masses. In this presentation, we review interannual to decadal
fluctuations of the latitudes of the Gulf Stream and Kuroshio Extension jets, and then we propose new theory, which
extends thin-jet theory for meanders on monthly and seasonal timescales, in order to understand the dynamics
of the jet variations on interannual to decadal timescales. In this theory, the low-frequent variability of the jets is
attributed to westward propagation of meridional shifts of the jets from east. These westward propagating signals
are induced by large-scale wind fluctuations, but are trapped around the jet axis. Using satellite altimeter data and
an eddy-resolving ocean general circulation model output, we show that the dynamics in the thin-jet framework
accounts for the bulk of interannual to decadal fluctuations of the Gulf Stream and Kuroshio Extension jets. Our
results suggest that the Gulf Stream (Kuroshio Extension) jet brings atmospheric signals from the eastern to the
western North Atlantic (North Pacific), and the resultant meridional shift of the jet induces the notable oceanic
changes, such as sea surface temperature and eddy activity, around the jets.
Poster (POC-P-5), POC Paper Session
Strong vertical mixing in the Urup Strait, Kuril Islands
Sachihiko Itoh1, Ichiro Yasuda1, Masahiro Yagi1, Satoshi Osafune2, Hitoshi Kaneko1, Jun Nishioka3, Takeshi
Nakatsuka4 and Yuri N. Volkov5
1
Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, 277-8564, Japan
E-mail: itohsach@aori.u-tokyo.ac.jp
2
Japan Agency for Marine-Earth Science and Technology, Yokosuka, 237-0061, Japan
3
Institute of Low Temperature Science, Hokkaido University, Sapporo, 060-0819, Japan
4
Graduate School of Environmental Studies, Nagoya University, Nagoya, 464-8601, Japan
5
Far Eastern Regional Hydrometeorological Research Institute, Vladivostok, Russia
Microstructure measurements were conducted in one of the Kuril Straits in the summer of 2007. Over the course
of 1 day of repeated observations across the Pacific side of the steep sill of the Urup Strait, extremely strong
mixing was observed during periods of Pacific-ward (down-sill) flows and during the transition from Pacificward
to Okhotsk-ward (up-sill) flows, with a turbulent energy dissipation rate ε of 10–6 to 10–5 W kg–1 and vertical
diffusivity of 10–1 to 5 ~ 10–1 m2 s–1. During the period of strong mixing, we observed homogeneous layers with
a thickness of 300–600 m and potential density of 26.6–26.7 σθ, occupying the entire water column in one case.
High values of ε within this layer indicate the injection of diapycnal flows from the upper and lower layers,
possibly contributing to the southward intrusion of intermediate water into the subtropical gyre.
Oral (S11-8594), MONITOR/POC Topic Session
Tsunami disaster and nuclear power plant accident effects on fishery facilities and marine
products in Fukushima Prefecture: Present conditions and prospects
Toshihiro Wada1, Yoshiharu Nemoto2, Shinya Shimamura2 and Satoshi Igarashi2
The Tohoku earthquake tsunami disaster of 11 March 2011 severely damaged Fukushima’s coastal areas. Parts
of all 10 fishing ports were destroyed, and 873 fishing vessels (74% of all registered vessels) were damaged.
Regarding prefectural facilities, the Soma branch office of the Fukushima Prefectural Fisheries Experimental
Station (FPFES) was destroyed, and its research vessel, the Iwaki-maru (150 tons) sank in Onahama Port. The
Fukushima Prefecture Fish Farming Station, located 3 km south of Fukushima No. 1 Nuclear Power Plant, was
destroyed. Moreover, contamination of marine products by radioactive substances has prevented fishermen
from commencing commercial fishing. As of June 2012, the Fukushima prefectural government has inspected
the concentrations of radioactive substances (cesium-134/137 and iodine-131) from 4,450 specimens within 165
marine species. From April 2011 – March 2012, 24 species exceeded the tentative regulation limit of cesium
(500 Bq/kg). From January – June 2012, 36 species exceeded the new legal limit of cesium (100 Bq/kg) enforced
in April 2012. The specimens exceeding the legal limit were mostly found in shallower waters south of the
nuclear power plant. Concentrations decreased gradually in some pelagic fishes, seaweed, abalone, and surf clams.
However, most fish, especially demersal fish species, have not shown a clear declining tendency, suggesting
that radioactive cesium is continuing to pass through the food web. FPFES and other cooperative organizations
continue to monitor marine products, seeking to clarify the intake/discharge mechanisms for radioactive substances
between the environment and marine products, to restore fishery operations quickly, and to safeguard the safety
of fishery product consumers.
Poster (S11-6), MONITOR/POC Topic Session
Oceanic dispersion of radioactive cesium around Japan and western North Pacific after
the Fukushima Dai-ichi Nuclear Power Plant accident
Hideki Kaeriyama1, Daisuke Ambe1, Masachika Masujima1, Kou Nishiuchi2, Ken Fujimoto1, Tsuneo Ono1 and
Tomowo Watanabe1
1
National Research Institute of Fisheries Science, FRA, Kanazawa-Ku, Yokohama, Kanagawa, 236-8648, Japan
E-mail: kaeriyama@affrc.go.jp
2
Seikai National Fisheries Research Institute, FRA, 148, 1551-8, Taira-machi, Nagasaki-shi Nagasaki, 851-2213, Japan
The Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident after the Great East Japan Earthquake and
tsunami on 11 March 2011 resulted in the elevation of the level of anthropogenic radioactivity in the marine
environment in the western North Pacific from atmospheric fallout and direct discharges of highly radioactive
waters. Intensive monitoring of iodine-131, cesium-134 (Cs-134) and cesium-137 (Cs-137) in seawater near
offshore FDNPP, and in marine organisms in the broader area around Japan, was conducted during the time when
information of radioactive contamination in the seawater around western part of Japan and western North Pacific
was quite limited. In this study, we report the concentrations of Cs-134 and Cs-137 in seawater collected from the
western North Pacific, Japan Sea and East China Sea during 2011. Although high concentrations of Cs-134 and
Cs-137 were detected off the coast of eastern Japan, an almost background level of Cs-137 was detected from
the samples collected off the coast of western Japan, Japan Sea and East China Sea. In the western North Pacific,
both Cs-134 and Cs-137 were detected from the sample collected along 155˚E, but Cs-134 was not detected at
almost all stations along 175˚E in June and July 2011. The Kuroshio extension seemed to prevent the southward
dispersion of radioactive cesium. The vertical distributions of radioactive cesium off the coast of northern Japan
around FDNPP revealed complex patterns mainly due to the water mass interaction between Oyashio water and
Kuroshio water.
Oral (S14-8651), POC/TCODE Topic Session
Quantification of BDOC (bio-available dissolved organic carbon) of different water
masses in East China Sea
Shuchai Gan and Ying Wu
State Key Laboratory of Estuarine and Coastal Research, East China Normal University, 3663 North Zhongshan Rd., Shanghai, 200062, PR China.
E-mail: ganshuchai@163.com
Bioavailability of dissolved organic carbon (DOC) has garnered recent attention for its potential impacts on
carbon sink and source capacity. As a major ‘food’ and excrement of micro-organisms, BDOC is important for
the microbial food web. In order to verify the importance of BDOC in regional carbon cycle modeling of the East
China Sea, a 10-day cultivation experiment was carried out focusing on the major water masses in the East China
Sea—Yangtze river plume, bloom, Taiwan Warm Current and Kuroshio Current. Excitation emission matrix
fluorescence spectroscopy (EEMs), which we applied in our study, has recently been used to characterize the
sources, transformation and behavior of CDOM (the light absorbing fraction of DOM) in aquatic environments.
Combined with parallel factor analysis (PARAFAC), 5 individual fluorescent components have been identified:
3 humic-like and 2 protein-like components (P1, P2), which suggest different sources and bioavailability. We
have found that P1 and P2 are responsible for the BDOC. The percentage of bio-available DOC ranges from 0 to
31.1% with different P1 and P2 fluorescence, highest in the bloom event in coastal water, lowest in the Yangtze
Estuary with lowest P1 and P2. Estimated from the degradation process, the inorganic carbon output of different
water masses was calculated. It is important to elucidate that the biological processes (both DOC degradation
and production) are ‘visible’ by 3-D fluorescence (EEMs), which verifies that the microbial food web plays an
important role in the carbon cycle of aquatic ecosystems.
Poster (S14-5), POC/TCODE Topic Session
Active carbon flux by diel migrant zooplankton in the eutrophic and oligotrophic waters
of the Canary Current
Sébastien Putzeys1,3, Carlos Almeida2, Pierrick Bécognée1, Lidia Yebra3, Ángeles Marrero Diaz4 and Santiago
Hernández-León1
1
Institute of Oceanography and Global Change. Universidad de Las Palmas de Gran Canaria, Tafira Baja, 35017, Las Palmas, Spain.
E-mail: sebastien.putzeys@ma.ieo.es
2
Centro de Biotecnología Marina, Universidad de Las Palmas de Gran Canaria, Muelle de Taliarte s/n, Telde, 35214, Las Palmas, Spain
3
Instituto Español de Oceanografía, Centro Oceanográfico de Málaga, Puerto Pesquero s/n, 29640, Fuengirola, Málaga, Spain
4
Department of Physic. Universidad de Las Palmas de Gran Canaria, Tafira Baja, 35017, Las Palmas, Spain
The Canary Current is characterized by a strong disruption of its flow by the Canary archipelago, forming a
downstream region of high mesoscale activity. This Canaries-African coastal transition zone connects the NW
African upwelling system with the oligotrophic open ocean waters of the Eastern North Atlantic subtropical gyre.
Further south, the Cape Vert Frontal zone is a highly productive area influenced by a quasi-permanent upwelling
and a thermohaline front. To assess the role of zooplankton in the vertical export of carbon in those areas, we
studied zooplankton biomass distribution and metabolism from the coast to the open ocean in an oligotrophic zone
(26ºN) and in a meso- or eutrophic one (21ºN). Zooplankton biomass followed the same pattern in both transects,
presenting two dense layers of organisms. The upper layer was located above 200 m and the second one below 400
m depth coincident with the deep scattering layer. However, the average migrant biomass (0-200 m) was 2.6-fold
higher at 21ºN (71.4±51.4 mmolC·m-2) than at 26ºN (27.1±12.4 mmolC·m-2). This was reflected in the downward
export of respiratory carbon (0-900 m depth) which was 10-fold higher in the southern than in the northern
transect (0.54±0.42 and 0.05±0.05 mmolC·m-2·d-1, respectively). Moreover, the estimated pigmented gut flux was
20-fold higher in the south than in the north (0.85±0.98 and 0.04±0.26 mmolC·m-2·d-1). The total contribution of
zooplankton metabolism to the particulate organic carbon flux was 4% in the oligotrophic transect, contrasting
with the 92% observed in the eutrophic transect.
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