Comparison of mesozooplankton assemblages across quasi-synoptic oceanographic features on the north-western iberian shelf break

Luc í a Lopez - Lopez ,Ana Mi anda, Ge a do Casas, Izaskun P eciado, Elena Tel, Julio Gil Luc í a Lopez Lopez , Ana Mi anda, Ge a do Casas, Izaskun P eciado, Elena Tel, Julio Gil Spanish Ins i u e o Oceanog aphy- C.O. San ande The pelagic sys em o e he shel b eak a ea is a complex en i onmen ac ing as a ansi ion zone be ween he p oduc i e shel and he oligo ophic wa e s o he open ocean. The exchange be ween hese wo sys ems is pa icula ly ele an in coas al ma gins wi h na ow shel es and wind ‐ d i en upwelling [ 1 ] such us he No h ‐ Wes e n Ibe ian shel b eak du ing E Figu e 4. Resul s om he NMDS analysis on he log ans o med mesozooplank on abundance da a. Capi al le e s a e used o adul s and lowe case o la ae “‐ shel es and wind d i en upwelling [ 1 ] , such us he No h Wes e n Ibe ian shel b eak du ing he summe ‐au umn [2] The biological composi ion o mesoscale s uc u es is o iginally de e mined by he sou ce wa e mass, howe e hei e olu ion (isola ion o eddies and wa ming and mixing o upwelled wa e s) a ec s communi y composi ion by modi ying species abundance and biomass [3]. Wi h his s udy, we aimed a di e en ia ing he mesozooplank on g oup’s abundance be e cha ac e izing he e olu ion om ecen ly upwelled wa e s o s a i ica ion and an icyclonic RATIONAL E Fig and lowe case o la ae . ‐ N” and “‐C” s ands o nauplius and cyp is, espec i ely. Elipses enci cling he poin s ep esen ing di e en oceanog aphic condi ions a e d awn o easing he in e p e a ion. cha ac e izing he e olu ion om ecen ly upwelled wa e s o s a i ica ion and an icyclonic eddy condi ions. Sampling was pe o med du ing dayligh be ween 23 d Sep embe and 10 h Oc obe 2009 along he No h‐wes e n shel b eak o he Ibe ian Peninsula. D S Figu e 3. Communi y composi ion in he sampling s a ions a ending o he main zooplank on g oups. The adius o he pies a e p opo ional o he o al abundace (N/m3)in he sample, wi h minimum being 10 02 ind ∙ m ‐3 and Sampling loca ions we e de e mined in si u acco ding o he CTD p o iles, including upwelling a eas‐(Fig 1a) di ided a e wa ds in o ea ly, medium and la e upwelling‐s a i ica ion a eas (Fig 1b) and an icyclonic eddy s uc u es (Fig 1c). The obse ed anomalies we e co obo a ed wi h he 10m and 50 m empe a u e anomalies (Fig 2a and2b espec i ely). Zooplank on was sampled wi h a 40 cm diame e bongo ne wi h 200µm mesh size in double ‐ oblique hauls up o 100 m Samples we e s o ed in 4 % bu e ed o malin L &METHO D h oughou he s udy a ea, ollowed by doliolids, appendicula ians and siphonopho es (Fig 3). The non me ic mul idimensional scaling (NMDS) on he assemblages ’ abundance Mesozooplank on abundance (ind ∙m‐3)washighe in he No h‐wes e n edge o he s udy si e and copepods we e he mos abundan g oup being 10 . 02 ind ∙ m and maximum 311.04 ind ∙m‐3 double oblique hauls up o 100 m . Samples we e s o ed in 4 % bu e ed o malin immedia ely a e collec ion. In he labo a o y, samples we e iden i ied and classi ied in o he main axonomic g oups, di e en ia ing holoplank on om me oplank on. NMDS analysis on he log‐ ans o med abundance da a was calcula ed o s udy simila i y amongs sampling condi ions. ANOSIM and SIMPER analysis we e also pe o med on he abundance da a ma ix. MATERIA L The non me ic mul idimensional scaling (NMDS) on he assemblages abundance composi ion clea ly iden i ied he di e en domains (Fig 4). Indeed, he analysis o simila i ies (ANOSIM) on he communi ies’ s uc u e iden i ied hese domains as s a is ically di e en (p < 0.05, 999 pe mu a ions). The second axes o he NMDS seemed o d i e he mesozooplank on communi y succession om upwelling o an icyclonic eddy condi ions. Based on hese i e oceanog aphic domains simpe analysis showed ha eddy RESULTS The iden i ica ion o oceanog aphic domains h ough T‐S p o iles in si u is p o en N S Based on hese i e oceanog aphic domains , simpe analysis showed ha eddy s a ions showed low abundance o la al s ages. Ea ly upwelling s a ions di e ed om o he upwelling phases by hei lowe p opo ion o appendicula ians and ela i e high lamelib achia la ae abundance. 30' 43 o N 30' 44 o N 30' 14 16 18 3 4 5 6 7 89 o be a eliable me hod o iden i ying sho ‐li ed oceanog aphic s uc u es. Wa ming in su ace wa e s was ound o al e he mesozooplank on communi ies be ween ea ly upwelled and an yciclonic eddy condi ions. Chae ogna a, jelly ish and la al s ages associa ed wi h he o me while os acods appendicual ians and o amini e a wi h he la e . Howe e , copepods we e he dominan mesozooplank on g oup in he s udy a ea, h oughou all he oceanog aphic domains s udied. C ONCLUSIO N 10 o W 8 o W 6 o W 4 o W 2 o W 0 o 42 o N 14 43 o N 30' 44 o N 30' 13 14 15 16 3 4 5 6 7 89 12 Figu e 1: a) Typical Tempe a u e‐Salini y‐Oxigen (TSO) p o ile o s a i ica ion in he wa e column [S a ion 1]; b) Typical TSO p o ile o a ecen upwelling e en [S a ion 4]; c) Typical TSO p o ile o a ecen upwelling e en [S a ion 8] [1] Mo ales e al. (2010) P og.Oceanog . 84: 158‐173; [2] Gil (2008) J. Biol. Assoc. UK. 88:217‐225; [3] S zelecki e al. (2007) Deep‐Sea Res II. 54: 1103‐1112 Bib C 10 o W 8 o W 6 o W 4 o W 2 o W 0 o 42 o N 30' 12 Figu e 2: a) In si u empe a u e ield a 10 m. b) In si u empe a u e ield a 50 m. Simbols ep esen sampling s a ions cha ac e ised by s a i ica ion ( illed ci cle), eddy (open ci cle), ea ly upwelling ( iangle), medium upwelling (squa e) and la e upwelling (s a ). 12 View publica ion s a s