Figure. Seasonally migrating copepods appeared at Station K2. We can identify two groups of the copepods by the life cycle. Red: surface spawning species, Yellow: deep spawning species. N. cristatus N. plumchrus N. flemingeri E. bungii M. pacifica C. pacificus C. jashinovi

Figure. Schematic diagrams of life cycles for the ontogenetically migrating copepods. Dotted line shows that adult specimens die after egg spawning. They carried out extensive diel and seasonal migrations down to mesoplegatic layers, these behaviors are one of pathways of carbon flux. Different from other copepods, Neocalanus species to die after egg production at depth occurred in the North Pacific and Southern Ocean and was accounted for more than half of zooplankton biomass at K2. Therefore, active carbon flux by the ontogenetic migrants is considered to be more important in the NW Pacific compared with the other oceans. WinterSpringSummerAutumn Metridia Neocalanus Eucalanus Surface Mesopelagic Phytoplankton bloom DVM We were here!

Depth distribution of surface-spawning copepods Figure 4. Depth distribution of the surface-spawning species in the layers above 1000 m collected by IONESS. Abundance is mean of four day-night deployments during the study period (n=4). Bars show standard error. Calanus pacificus concentrated their biomass above 50 m, and dominated by adult males and females. They would emerge dormancy and start reproductions. Eucalanus bungii showed two abundance peaks at surface and in mid-layers. Over the study period, they decreased younger specimens and they started a downward migration. Metridia pacifica was a strong diel migrator, residing at mid-layers in daytime and at the surface in nighttime. Thus, they are active. Depth (m)

Depth distribution of deep-spawning copepods Figure 5. Depth distribution of the surface-spawning species in the layers above 1000 m collected by IONESS. Abundance is mean of four day-night deployments during the study period (n=4). Bars show standard error. Younger specimens of Neocalanus cristatus appeared abundantly in the layers above 100 m and they were developing into overwintering stage toward the end of our study period. Overwintering stages were dominated Neocalanus flemingeri and they resided at the mesopelagic layers throughout the study period, showing dormancy. Neocalanus plumchrus was most predominant species among zooplankton community and concentrated overwintering stage at the surface. Depth (m)

Table 1. Active carbon flux by the dominant diel migrants, Metridia pacifica and its comparison to POC flux. * Data from Ken. Parameter1 Aug.5 Aug.12 Aug. 16 Aug. Migrant population Abundance (10 2 animals m -2 ) Weighted mean depth in daytime (m) Ambient temperature in daytime (˚C) Active carbon flux (mgC m -2 day -1 ) Respiration Egestion -- Biomass (mgC m -2 ) Mortality Total POC flux (mgC m -2 day -1 ) * Ratio of active carbon flux to POC flux (%) Active carbon flux by Metridia pacifica is estimated to be 2-8 mgC m -2 day -1. Respiratory and egestion fluxes showed a similarly importance, and mortality flux was minor component. These active carbon flux by the single species was accounted for more than 20% of sinking POC flux.

Comparing with the results of the world’s oceans, respiratory flux of K2 zooplankton community showed the largest numbers and was nearly equal to sedimentary flux in the NW Pacific as shown by Debbie. Although Metridia pacifica was dominant diel migrants, they were accounted for 10% of the zooplankton respiratory flux. Therefore other zooplankton taxa would more important for respiratory flux. Table 2. Respiratory flux (mgC m -2 day -1 ) by the diel vertical migrants in the world’s oceans modified from Al- Murairi & Landry (2001). ME: Mesozooplankton, MA: Macrozooplankton, MP: M. pacifica. PC: Particulate carbon flux. LocationSource (mgC m -2 )Component(%) Atlantic NFLUX29ME+MA23150Longhurst et al. (1990) BATS192ME Dam et al. (1995) BATS49ME+MA15Steinberg et al. (2000) E. Equator96ME315150Zang & Dam (1997) Pacific E. Equator155ME620150Zang & Dam (1997) E. Equator53ME+MA64150Le Borgne & Rodier (1997) W. Equator47ME+MA36Le Borgne & Rodier (1997) ALOHA158ME+MA415Al-Murairi & Landry (2001) Migrant biomassFluxCompared to PC Depth (m) 150 ALOHA-ME+MA Steinberg et al. (in prep.)150 K2-ME+MA Steinberg et al. (in prep.)150 K MP1-42-3Kobari et al. (in prep.)150

Table 4. Active carbon flux (mgC m -2 year -1 ) by the ontogenetic vertical migrants in the world’s oceans. CF: C. finmarchicus, NT: N. tonsus, NC: N. cristatus, NF: N. flemingeri, NP: N. plumchrus, Note: carbon flux at station K2 is shown as daily basis (mgC m -2 day -1 ). LocationSource (mgC m -2 )Spp.(%) Atlantic Ocean OWS I346CF275<1200Longhurst & Williams (1992) ST-NT Bradford-Grieve et al. (2001) STF - NT Bradford-Grieve et al. (2001) Pacific Ocean SAT OWS P-NC+NF+NP Bradford-Grieve et al. (2001) Oyashio7300NC+NF+NP430091Kobari et al. (2003) Migrant biomassFluxCompared to PC Depth (m) 1000 Active carbon flux by ontogenetic migration of N. flemingeri was estimated to be 3 mgC m -2 day -1 and was accounted for 20% of sinking POC at 500 m. Unfortunately, the active carbon flux by other two Neocalanus could not be estimated because they still resided at surface and were active. If it depends on migrant biomass, other two Neocalanus species will produce much larger carbon flux than those by N. flemingeri. This flux could not be negligible and significant carbon pathway to the mesoplagic K2322NF3*3* 9-20Kobari et al. (in prep.)500 Southern Ocean -NT9300-Bradford-Grieve et al. (2001)- K21757NC+NP?Kobari et al. (in prep.)--

Picophytoplankton unedible for the copepods dominated primary production. We measured pigment concentrations in copepod guts and estimated feeding rate and its composition. Phytoplankton composed <3% of the ingested carbon and their carbon demands should be relied on POC other than phytoplankton. Thus, their faecal pellets are also considered to come from non-phytoplankton materials. These results suggest that some fraction of the exported carbon could be channeled through microbial food web and the copepod community. Table 1. Community feeding rates and faecal pellets production by the ontogenetically migrating copepods in the layer above 150 m. * Data from Phil, ** Data from Ken. ParameterSource1 Aug. Units are mgC m -2 d -1, excepted for copepod biomass (mgC m -2 ) and ratio (%). 5 Aug.12 Aug. 16 Aug. Primary production (PP) * Biomass Respiratory requirement Feeding rate Ratio grazed Faecal pellet production Phytoplankton Other POC Ratio of PPPico Nano Micro

Contribution of the copepod faecal pellets to sinking POC Figure 6. Sinking POC flux and faecal pellet production (FPP) by the ontogenetic migrating copepods. POC flux at each layer was estimated from the formula of Pace et al. (1987) and primary production (Data from Phil). Comparing with sinking POC flux estimated from the equation of Pace and others, the copepod community feces composed less than 10% of sinking POC above 150 m, and their contribution to sinking POC is considered to be small. Since they were actively feeding on non-phytoplankton materials and transform them into faecal pellets, this process is considered to be an important carbon pathway during seasons dominated by small phytoplankton.

What we knew from the ontogenetic migrants? 1. Most of the copepod community resided at surface during our study period and was developing with actively feeding on non-phytoplankton. 2. Carbon budget of the copepod feeding and egestion shows that a large fraction of their ingested carbon is channeled through microbial food web but their faecal pellets are minor component of sinking POC. 3. Active carbon flux by dominant diel migrant composed more than 20% of the sedimentary POC flux at 150 m and can be supplement source for the mesopelagic carbon demand. 4. Active carbon flux by ontogenetic migration of single species was account for 20% of the sedimentary POC flux at 500 m, and could be an important source for the mesopelagic carbon demand considering with the copepods residing at surface.

The ontogenetically migrating copepods showed three types of life stages. Figure 2. Depth distribution of the ontogenetically migrating copepods in the layers above 1000 m. Abundance is mean of four day and nighttime IONESS deployments during the study period (n=4). Bars show standard error. Active -DVM- Dormant Active -no DVM- Active -no DVM- Active but -partially OVM- Active -no DVM-

Ontogenetically migrating copepods dominate zooplankton community at K2 Figure 3. Species composition of abundance and biomass for the ontogenetically migrating copepods above 1000-m depth at station K2 in the Western Subarctic Gyre during late summer. Ontogenetic migrating copepods composed >76% of zooplankton biomass, showing dominant zooplankton components. Neocalanus copepods were accounted for >80% of the copepod community.

Mortality and respiratory flux during dormancy （ Neocalanus flemingeri ） Supplement Figure 2. Carbon-based biomass (mgC m -2 ) and flow (mgC m -2 year -1 ) of Neocalanus flemingeri through overwintering at station K2 in the Western Subarctic Gyre. Overwintering biomass （ ） Carbon flux C4 0.7 C5 3.1 C6 Female C4 <0.1 Offspring C6 Male Surface Interior

Feeding rate and faecal pellet production Supplement Figure 3. Biomass (mgC m -2 ), feeding rate and faecal pellet production (mgC m -2 day -1 ) of the ontogenetically migrating copepods at station K2 in the Western Subarctic Gyre.