Metabolism of mesozooplankton across the Benguela upwelling system in terms of ETS and GDH activities

No he n Benguela upwelling: D i ing o ces and ecosys em esponses I. Fe nández-U uzola, A. He e a, L. Pos el, N. Osma, M. Gómez and T. T. Packa d e abolism o mesozooplank on ac oss he Benguela upwelling sys em in e ms o ETS and GDH ac i i ies M Ins i u e o Oceanog aphy and Global Change, Ecophysiology o Plank on G oup, Uni e si y o Las Palmas de G an Cana ia, Cana y Islands, Spain. E-mail add ess: i e nandez@beca ios.ulpgc.es INTRODUCTION Respi a ion in he ocean ecosys ems Respi a ion is a ubiqui ous p ocess which cons i u es a key componen in he es ima ion o he ca bon lux. Howe e , i s magni ude in ocean ecosys ems emains unce ain (Del Gio gio and Dua e, 2002) due o he di icul y on quan i ying in si u espi a ion a es. They p o ide low da a acquisi ion a es and a e complica ed by o ganisms manipula ion, o e c owding and s a a ion (Bidiga e, 1983). WATER-BOTTLE INCUBATIONS Po en ial measu emen s such as ETS a oid hese me hodological a i ac s!! (I) NH4+ is an in e medi a e p oduc in decomposi ion o o ganic ma e , which cons i u es he mos educed o m o N. (II) NH4+ sus ains a global a e age o 80 % o he au ho oph’s eque imen s (Ha ison, 1992), wi h he mesozooplank on esponsible o 12 – 23 % (He nández-León, 2008). Zeh and Kudela (2011) INTRODUCTION Impo ance o NH4+ in ma ine sys ems RECYCLYING EFFICIENCY Nu i ional His o y (Mille and Roman, 2008; Saba e al., 2009) Tempe a u e (Ikeda, 1985) T ophic In e ac ions (Glibe , 1998) INTRODUCTION Elec on T anspo Sys em as index o O2 espi a ion Vmax INTRODUCTION Glu ama e dehyd ogenase as index o NH4+ espi a ion GDH (EC 1.4.1.3) is ound in high le els in plank onic c us aceans (Regnaul , 1987). I s ole in amino acids ca abolism agues o i s con ol o e a g ea p opo ion o NH4+ exc e ion. Modi ied om Yuen and Chiew (2010) INTRODUCTION Benguela Upwelling Sys em Namibian coas is cha ac e ized by in ense coas al upwelling associa ed wi h Benguela cu en . These upwelling a eas p o ide high o ganic p oduc ion linked o phy oplank on bloom. Map o sea su ace empe a u e om he MODIS senso on boa d NASA Aqua sa elli e (3 Feb.2008). We es ima ed biomass, as well as he po en ial espi a ion (ETS) and NH4+ exc e ion (GDH) in mesozooplank on communi y in h ee dep hs along a ansec wi h di e en oceanog aphic condi ions o unde s and how a ec phy oplank on bloom in he zooplank on me abolism. MATERIAL AND METHODS S udy a ea 4 sec ions ac oss he no he n Benguela upwelling sys em: LT1,LT2 and LT3 wi h 12 s a ions, and LT4 wi h 21 s a ions. '-:::~- --:-- -- . -- _. 1-·· 1 . --_ . . -- _. - -...,_ . "."';'" . -_ .. _. ..... ... _. _ . MATERIAL AND METHODS Expe imen al design SIZE FRACTIONATION Da a analysis Labo a o y wo k a ins i u e TAXONOMY, BIOMASS and METABOLISM Mo e han 700 samples we e analyzed o me abolic a es S o age in c io ials a -80 oC GDH Ac i i y (Bidiga e and King, 1981) ETS Ac i i y (Packa d e al., 1971) P o ein mass (Low y, 1951) 0 50 100 150 200 250 18:00 18:14 18:28 18:43 18:57 19:12 19:26 Tie e [m] 457N070301, 13-9-2000, 200-75 und 75-25m ZOOPLANKTON SAMPLING 100-200 μm 200-500 μm 500-1000 μm > 1000 μm RESULTS Global a e ages om he di e en sec ions The highe biomass alues a e coupled o he upwelled wa e s. ETS ac i i y i s wi h he biomass pa e n, while GDH ac i i y p esen mo e dispe sion since i oplanc on does no ha e e ec in his a e. Howe e , he GDH maximum a e is s ill nex o he upwelling. Biomass [mg p o ein . (m3)-1] NAM027 NAM025 NAM023 NAM021 NAM019 NAM017 NAM014 NAM009 NAM004 NAM001 -- __ _ • • • • • 4 • 3 50 • • • • • • • E' '-'- 5 ~ 2 Q 100 1 • • • 150 O 500 400 300 200 100 O Sec ion Dis ance [km] RESULTS Biomass and enzyme ac i i ies o each “sho ” sec ion SECTION 1 The e is a bloom on NAM007, which causes high enzima ic a es in his a ea. This ac i e me abolism seems o mo e o sho e along he subsupe icial wa e s, specially o GDH. SECTIONS 3 and 4 These wo sec ions show a simila pa e n han ha ound in sec ion one. The bloom is now placed a ound NAM005 and i sligh ly ex ends o sho e. SECTION 2 Biomass and ETS ac i i y a e mos ly dis ibu ed in all he wa e column o NAM009. The la e , howe e , p esen s i s maximum be ween 200-75 m. This no seems o a ec GDH, whose highe ac i i y is in he su ace wa e s o NAM017 p obably due o a peak o zooplank on in his egion RESULTS Size ac ion con ibu ion o he mean alues in e ms o Biomass 100-200 μm 200-500 μm 500-1000 μm > 1000 μm All he ac ions p esen high alues onsho e. Howe e , he lowe he size ac ion is, he mo e coupled is wi h he upwelling. Consequen ly, he mesozooplank on o e 500 μm seems o domina e o sho e, wi h maximum alues on NAM023 o he highes ac ion. RESULTS Size ac ion con ibu ion o he mean alues in e ms o ETS FRACCIONES INTEGRADAS ETS 100-200 μm 200-500 μm 500-1000 μm > 1000 μm All he ac ions p esen high alues onsho e. Howe e , he lowe he size ac ion is, he mo e coupled is wi h he upwelling. Consequen ly, he mesozooplank on o e 500 μm seems o domina e o sho e, wi h maximum alues on NAM023 o he highes ac ion. RESULTS Size ac ion con ibu ion o he mean alues in e ms o GDH FRACCIONES INTEGRADAS GDH 100-200 μm 200-500 μm 500-1000 μm > 1000 μm All he ac ions p esen high alues onsho e. Howe e , he lowe he size ac ion is, he mo e coupled is wi h he upwelling. Consequen ly, he mesozooplank on o e 500 μm seems o domina e o sho e, wi h maximum alues on NAM023 o he highes ac ion. RESULTS Wha does he s a isc ics say? 1. A e he e signi ican di e ences in ETS, GDH and Biomass be ween DEPTHS? YES!! (K uskal-Wallis es , p<0.001) RESULTS Wha does he s a isc ics say? 2. A e he e signi ican di e ences in ETS, GDH and Biomass be ween SIZE FRACTIONS? YES!! (K uskal-Wallis es , p<0.001) RESULTS Wha does he s a isc ics say? YES!! (Mann-Whi ney es , p<0.001) 3. A e he e signi ican di e ences in ETS, GDH and Biomass be ween UPWELLED and OFFSHORE WATERS? RESULTS Wha does he s a isc ics say? 4. A e he e signi ican di e ences in ETS, GDH and Biomass be ween DAY/NIGHT SAMPLING? NO!! (Mann-Whi ney es , p>0.001) ✗ RESULTS Me abolism and biomass ela ionship: Kleibe ’s law Fo many yea s i has been accep ed he pa adigm o he Kleibe ´s law, which s ablish a exponen ial ela ionship be ween biomass and me abolic a es wi h a coe icien “b” close o 0.75. Se e al zooplank on s udies show di e en a ios close o o g ea e han 0.75 in op imal eeding condi ions, and below 0.75 when he o ganisms a e ound in oligo ophic a eas o poo eeding (Gómez e al., 2008; He e a e al., 2011; Ma ínez, 2007; Packa d and Gómez, 2008). In his s udy, he coe icien s “b” a e g ea e han 0.75 o ETS and GDH ac i i ies in bo h upwelling and o sho e a eas. Me abolic a e = aWb (W=biomass) RESULTS Me abolism and biomass ela ionship: Kleibe ’s law OFFSHORE log ETS = 1.05 log W + 0.68 UPWELLING log ETS = 1.08 log W + 0.67 ETS s Biomass