Limnological description of the Tarelo lagoon (SW Spain)

1 Limnological desc ip ion o he Ta elo lagoon (SW Spain). L. Se ano1, M. Reina1, A. A echede a1, M. A. Casco2& J. Toja1 1Depa amen o de Biología Vege al y Ecología. Uni e sidad de Se illa. Ap. 1095. 41080. Se illa. Spain. 2P.C. Ficología. Museo de La Pla a. Ap. 1900. La Pla a. A gen ina. ABSTRACT The lagoon o Ta elo (SW, Spain) is a pe manen aqua ic sys em loca ed nea he es ua y o he Guadalqui i Ri e . The wa e quali y o his lagoon was poo du ing he s udy pe iod (Janua y 2001-Augus 2002): he high wa e u bidi y hinde ed he g ow h o subme sed aqua ic mac ophy es and he bo om wa e was deple ed o dissol ed oxygen in sp ing-summe despi e he mixing c ea ed by he wind. The concen a ion o plank onic chlo ophyll a anged om 74.2 o 330.7 µg l-1 in he su ace wa e and om 34.8 o 256.2 µg l-1 in he bo om wa e . The blooms o cyanobac e ia (>106 cells ml-1) we e equen and con- ibu ed o he gene a ion o episodic anoxia in he wa e column. Consequen ly, he numbe o bo h plank onic and ben honic axa we e e y low. Two axa o cyanobac e ia, Aphanocapsa holsa ica and Mic ocys is sp., occu ed wi h an a e age ela i e abundance >30%. The mos commonly ound axa we e Oscilla o ia sp., Oocys is sp., Oscilla o ia limne ica, Ch oococcus sp. and Mono aphidium ci cinalle. Popula ion explosions (>2000 ind l-1) we e common in o i e s such as B achionus plica ilis and Ke a ella opica. The densi y o Chi onomus plumosus in he sedimen su ace declined ab up ly when oxygen was sca - ce. The empo al a iabili y o nu ien concen a ions anged om e en -scale pulses o seasonal ime scales. Ni ogen ollo- wed a seasonal pa e n o loading in win e and deple ion in summe , whe eas he a ailabili y o o-P in he wa e oscilla ed in pulses. The concen a ion o o-P in he in e s i ial wa e o he sedimen peaked in e mi en ly du ing he s udy pe iod and i was posi i ely co ela ed wi h he concen a ion o o-P in he bo om-wa e ( =0.698, P<0.05). On a e age, he concen a ions o o ganic ma e and To -P in he sedimen we e ela i ely low (7 % and 456 µg gDW-1, espec i ely), and bo h a iables we e highly co ela ed ( =0.853, P<0.01). The majo i y o he sedimen P was o ganic, indica ing he g ea con ibu ion o he au och honous p oduc ion o he sedimen load. I can be expec ed ha he in e nal P loading will inc ease wi h ime and lead he sys em o a highe ophic deg ee. Keywo ds: eu ophica ion, wa e quali y, P- ac iona ion, cyanobac e ia, whi e-headed duck, Oxyu a leucocephala. RESUMEN La laguna de Ta elo (SO España) es un sis ema acuá ico pe manen e si uado ce ca del es ua io del Río Guadalqui i . La cali- dad del agua de es a laguna ue pob e du an e el pe íodo es udiado (ene o 2001-agos o 2002): la ele ada u biedad del agua limi ó el c ecimien o de plan as acuá icas sume gidas y no se de ec ó oxígeno disuel o en el ondo de la columna de agua du an e la p ima e a- e ano a pesa de la mezcla gene ada po el ien o. La concen ación de clo o ila planc ónica osci- ló en e 74.2 y 330.7 µg l-1 en la supe icie y, en e 34.8 y 256.2 µg l-1 en el ondo de la laguna. Las p oli e aciones masi as de cianobac e ias ue on ecuen es (>106 cells ml-1) y con ibuye on a la apa ición de episodios de anoxia en la columna de agua. En consecuencia, el núme o de axa an o en el planc on como en el ben os ue muy bajo. Dos cianobac e ias, Aphanocapsa holsa ica y Mic ocys is sp., alcanza on una abundancia ela i a p omedio >30%. Los axa más comunes en el i oplanc on ue on: Oscilla o ia sp., Oocys is sp., Oscilla o ia limne ica, Ch oococcus sp. y Mono aphidium ci cinalle. Las poblaciones de o í e os como B achionus plica ilis y Ke a ella opica expe imen a on explosiones de más de 2000 ind l-1. La densidad de Chi onomus plumosus en la supe icie del sedimen o disminuyó d ás icamen e a bajas concen aciones de oxíge- no. La concen ación de nu ien es mos ó una amplia a iabilidad empo al: desde pa ones es acionales has a pulsos in e - mi en es. El N siguió un pa ón es acional de en iquecimien o en in ie no y desapa ición en e ano, mien as que la disponibi- lidad de o-P osciló en pulsos. La concen ación de o-P en el agua in e s icial del sedimen o, que siguió una e olución de picos y alles a lo la go del pe íodo de es udio, se co elacionó con la concen ación de o-P en el agua del ondo ( =0.698, P<0.05). Las concen aciones p omedio de ma e ia o gánica y To -P en el sedimen o ue on ela i amen e bajas (7 % y 456 µg gDW-1, espec i amen e) y, ambas a iables se co elaciona on ue emen e ( =0.853, P<0.01). La mayo pa e del P sedimen a io e a de composición o gánica, lo que indica la impo ancia de la p oducción au óc ona en la ca ga de nu ien es del sedimen o. Es espe able que la ca ga in e na de P aumen e en el iempo ele ando el ni el o ico de es e sis ema. Palab as cla e: eu o ización, calidad del agua, accionamien o de P, cianobac e ias, mal asía, Oxyu a leucocephala. Limne ica 23(1-2): 1-10 (2004) © Asociación Española de Limnología, Mad id. Spain. ISSN: 0213-8409 Limne ica 23(1-2) 11/10/04 10:04 Página 1 INTRODUCTION The lagoon o Ta elo (SW, Spain) is a pe ma- nen aqua ic sys em loca ed a 3 km om he es ua y o he Guadalqui i Ri e in he limi o he illage o Sanlúca de Ba ameda wi h he Doñana Na u al Pa k. The bed o he lagoon was o igina ed by exca a ion o he ex ac ion o sand and o he d y ma e ials. The pi was e en- ually looded h ough seepage om he es ua y du ing win e 1989. Since hen, i has become an impo an b eeding si e o he Whi e-headed duck (Oxyu a leucocephala). Fo his eason his si e is unde p o ec ion o he Doñana Na u al Pa k. Howe e , his lagoon is loca ed in an ag icul u al a ea o in ensi e ac i i y and i is ed by he i e bed aqui e o he Guadalqui i Ri e , which has long been su e ing a se e e ni a e pollu ion (Na a o Al a gonzález e al., 1993). Consequen ly, a e y high p oduc i i y can be expec ed in his lagoon ha has changed om a sys em wi h a dense subme sed mac o- phy e de elopmen o ano he domina ed by phy oplank on in ecen yea s. The coas al lagoons a e e y dynamic sys- ems, he e o e assessing he scale o a ia ion and he ange o ansi ional s ages hey pass h ough a e basic ools o hei managemen (Comín e al., 1999). This s udy desc ibes he limnology o he lagoon o Ta elo om Janua y 2001 o Augus 2002 ocusing on i s wa e qua- li y. The nu ien dynamics has been add essed in ime and space by s udying he changes in he e ical s uc u e o he wa e column and i s in e ac ion wi h he sedimen . MATERIAL AND METHODS The lagoon was sampled mon hly be ween Janua y 2001 and Augus 2002 a an open si e (3-4 m deep) and a li o al si e (1.5-2.5 m deep). A day-cycle sampling was pe o med in May and June 2001. Ve ical p o iles o empe a u e, dissol ed oxygen and pH we e measu ed in si u wi h a p obe. The ligh compensa ion poin was es ima ed as 2.7 imes he dep h o he Secchi Disk (Ma gale , 1983). Conduc i i y (ATC) was measu ed in he labo a o y. Wa e samples we e aken in duplica es om he su ace and he bo - om o he wa e column a bo h si es using an elec ical bilge pump. Wa e was il e ed h ough Wha man GF/C il e s in he labo a o y. Chlo ophyll awas ex ac ed wi h me hanol in 3 eplica es pe sample (Ma ke e al., 1980) and i s concen a ion was calcula ed using Talling & D i e `s o mula (Vollenweide , 1969). The ol- lowing chemical concen a ions we e measu ed in he wa e samples in 2-3 eplica es: o al sus- pended solids (g a ime y), o ganic suspended solids (g a ime y a e igni ion a 450 ºC, 5 h), Cl-(APHA, 1985), SO42- (Rodie , 1981), o al alkalini y (Gol e man e al., 1978), NO2- (S ickland & Pa sons, 1972), NO3-(Gol e man, 1991), o-P (Mu phy & Riley, 1962), NH4+by nessle iza ion (Rodie , 1981), and o al phos- pho us (To -P) a e acid diges ion (De G oo & Gol e man, 1990). Sedimen s we e collec ed wi h an Ekman-Bi ge bo om sample . In he labo a o y, sedimen s we e no ea ed (nei he d ied no ozen) and s o ed a 4 °C. The con- cen a ion o o ganic ma e in he sedimen was es ima ed in 3-4 eplica es by loss on igni ion (450 °C, 5 h). The To -P concen a ion in he sedimen samples was measu ed a e acid diges ion (De G oo & Gol e man, 1990) o he igni ed sedimen . The concen a ion o o al N in he sedimen was es ima ed as he concen a- ion o NH4+measu ed a e nessle iza ion o he diges ed sedimen . The in e s i ial wa e was ob ained by cen i uga ion (12 000 .p.m., 15 min) and he concen a ion o o-P was measu ed as be o e. The P- ac iona ion o he sedimen was pe o med in duplica es o a sample collec - ed in May 2001 om he open si e. A po ion o he sedimen sample was sie ed h ough a ny al mesh o 0.1 mm po e size ( ine sedimen ). Bo h he ine sedimen and he unsie ed sedimen ( o al sedimen ) we e ac iona ed by sequen ial ex ac ion wi h chela ing compounds ollowing he EDTA’s me hod (Gol e man, 1996). Lugol p ese ed samples o phy oplank on we e obse ed acco ding o he U e möhl`s (1958) echnique o enume a ion. Zooplank on 2Se ano e al. Limne ica 23(1-2) 11/10/04 10:04 Página 2 samples we e collec ed by il e ing 5-10 l o wa e h ough a ny al mesh o 63 mm po e size and p ese ed in 4% o maldehyde. The ben hic in e eb a es we e collec ed wi h an Ekman- Bi ge bo om sample o 144 cm2o su ace and p ese ed in 70% e hanol o u he examina- ion wi h a binocula mic oscope. Rain all da a was ob ained om he me eo olog- ical s a ion o “Palacio de Doñana” (RBD-CSIC). RESULTS The wa e dep h anged om 3 o 4 m a he open si e du ing he s udy pe iod. The elec ical conduc i i y (ATC) anged om 9.4 o 13.5 mS cm-1. Wa e was ich in Cl-and SO42- and anged om 125 o 137 meq l-1and om 42 o 47 meq l-1, espec i ely, whe eas o al alkalini y was much lowe (2-3 meq l-1). The e ical p o ile o empe a u e changed wi hin a e y na ow ange om he op o he bo om o he wa e column (0.5-1.5 °C in win- e and 3-5.5 °C in summe ). A weak he mal s a i ica ion de eloped du ing he day in sum- me , sugges ing ha his lagoon was polymic ic. The concen a ion o dissol ed oxygen changed widely ac oss he wa e column du ing he s udy pe iod (Table 1 and Figu e 1). The concen a ion o dissol ed oxygen in he su ace wa e was always highe han in he bo om wa e , excep o an episodic anoxia in June 2001 when bo h con- cen a ions we e ze o, o when he whole wa e column was oxygena ed due o s ong winds (Sep embe -Decembe 2001). Consequen ly, he Limnology o Ta elo Lagoon 3 Table 1. Minimum and maximum alues o se e al a iables in he su ace and bo om o he wa e column a he open si e du ing he s udy pe iod (Janua y-Decembe 2001 and Janua y-Augus 2002). Valo es mínimos y máximos de di e sas a iables en la supe icie y el ondo de la columna de agua du an e el pe íodo de es udio. 2001 2002 Su ace Bo om Su ace Bo om Tempe a u e (°C) 14.4-28.5 14.4-27.3 13.2-26.2 11.9-25.0 D.O. (mg l-1) 0.0-20.0 0.0-19.4 2.2-19.2 0-5.9 pH 6.3-9.6 6.3-9.1 5.6-9.5 5.5-8.8 Chl a(µg l-1) 74.2-226.6 34.8-174.5 115.2-330.7 105.6-256.2 T.S.S. (mg l-1) 25.6-60.5 24.9-56.5 49.0-238.3 111.7-200.0 NO3-(mM) 0.0-20.3 0.0-11.4 0.0-8.0 0.0-1.6 NO2-(µM) 6.4-946.6 13.4-961.3 7.4-312.0 3.5-98.8 NH4+(mM) 0.1-2.2 0.1-2.7 0.4-3.0 0.7-5.3 o-P (µg l-1) 1.8-97.4 3.7-150.1 7.1-48.5 6.5-234.9 To -P (µg l-1) 101.6-600.0 135.3-666.6 155.9-317.6 216.3-528.5 DIN/To -P 46.7-1281.6 42.8-936.2 73.8-784.0 59.5-215.7 Figu e 1. Concen a ion o dissol ed oxygen in he su ace (solid line) and bo om wa e (dashed line) a he open si e du ing he s udy pe iod. Mean ± SD. Concen ación de oxíge- no disuel o en la supe icie (línea con inua) y el ondo (línea discon inua) del cen o du an e el pe íodo de es udio. Limne ica 23(1-2) 11/10/04 10:04 Página 3 pH o he su ace wa e was always equal o o highe han he pH o he bo om wa e (Table 1). The laye o anoxic wa e in he open si e was loca ed a 2-2.5 m deep in sp ing-summe . In con- as , he bo om wa e a he li o al si e was a ely anoxic (excep in Ma ch 2002). The ligh compensa ion dep h in he open si e anged om 0.7 o 2.3 m. Then, he a ailabili y o PAR in he bo om wa e was always lowe han 1% du ing he s udy pe iod. The ligh com- pensa ion dep h was in e sely co ela ed wi h he mean alue o chlo ophyll aconcen a ion in he wa e column ( = -0.581, P<0.05) and also, wi h bo h he mean alues o o al suspended ma e and o ganic suspended ma e ( = -0.718, = -0746, P<0.01, espec i ely). The concen a- ion o plank onic chlo ophyll a anged om 74.2 o 330.7 µg l-1 in he su ace wa e and om 34.8 o 256.2 µg l-1 in he bo om wa e du ing he s udy pe iod (Table 1). The concen- a ion o plank onic chlo ophyll awas signi i- can ly highe in he su ace han in he bo om wa e (Fig. 2) du ing June-Sep embe 2001 and July-Augus 2002 ( -s uden , P<0.01). The concen a ion o dissol ed ino ganic N ol- lowed a seasonal pa e n, especially NO3-and NO2-concen a ions ha dec eased in summe and inc eased du ing ainy pe iods (Fig. 3). In ac , he concen a ion o NO3-in he bo om wa e was signi ican ly co ela ed o he amoun o ain all collec ed be ween samplings ( =0.717, P<0.01). Also, bo h he NO2-concen- a ion in he bo om and su ace wa e we e sig- ni ican ly co ela ed o ain all ( =0.592 and =0.604 P<0.05, espec i ely). In con as , he concen a ion o o-P in he wa e , especially in he bo om wa e , oscilla ed in pulses h oughou he s udy pe iod (Fig. 4). The concen a ion o o- P in he in e s i ial wa e o he sedimen also peaked in e mi en ly and i was posi i ely co e- la ed wi h he concen a ion o o-P in he bo - om-wa e ( =0.698, P<0.05). The low a ailabili- y o P and he high concen a ion o dissol ed ino ganic ni ogen (DIN) de e mined ha he a io o DIN/To -P was ela i ely la ge in bo h he su ace and he bo om wa e (Table 1). In con as , he a io N/P in he sedimen anged om 0.05 o 4.34 du ing he s udy pe iod. 4Se ano e al. Figu e 2. Concen a ion o plank onic chlo ophyll ain he su ace (solid line) and bo om wa e (dashed line) a he open si e du ing he s udy pe iod. Mean ± SD. Concen ación de clo o ila aplanc ónica en la supe icie (línea con inua) y el ondo (línea discon inua) del cen o du an e el pe íodo de es udio. Figu e 3. Concen a ion o NO3-in he su ace (solid line) and bo om wa e (dashed line) a he open si e du ing he s udy pe iod. Mean ± SD. Concen ación de NO3-en la supe icie (línea con inua) y el ondo (línea discon inua) del cen o du an e el pe íodo de es udio. Limne ica 23(1-2) 11/10/04 10:04 Página 4 The concen a ion o To -P in he sedimen anged om 120.3 o 964.3 µg gDW-1, and he concen a ion o o ganic ma e anged om 0.9 o 13.5%. Bo h a iables we e highly co ela ed ( =0.853, P<0.01) sugges ing ha he sedimen was ich in o ganic P-compounds. The P- ac- iona ion o he sedimen showed ha he o gan- ic P- ac ions comp ised 75% o he ine sedi- men and 64 % o he o al sedimen (Table 2). The la ges P- ac ion was always he one ex ac ed wi h alkali (o g-Palkali), ollowed by he acid soluble o ganic P- ac ion (o g-Pacid) in he ine sedimen o he i on-bound ac ion (Fe (OOH)~P) in he o al sedimen . The o g- Pacid and he esidual o ganic ac ion (o g- P esidual) we e highe in he ine sedimen ha in he o al sedimen ( -s uden , P<0.01), whe eas he Fe (OOH)~P and CaCO3~P we e highe in he o al sedimen ( -s uden , P<0.01). These di e ences can be explained by a lowe con en o la ge de i al pa icles in he ine sedimen . Fi y- i e axa o phy oplank on we e iden i- ied du ing he s udy pe iod: 25 axa o cyanobac e ia, 14 chlo ophy es, 4 dino lagela es, 10 dia oms, 3 c yp ophy es and 3 ch ysophy es (Table 3). The phy oplank on densi y anged om 2·104 o 7·106 cells ml-1. Two axa o cyanobac e ia, Aphanocapsa holsa ica and Mic ocys is sp., appea ed wi h an a e age ela i e abundance o 35 % and 30 %, espec i ely. O he axa such as C yp omonas sp., Amphidinium sp., Gymnodinium sp., Chae osce os sp., Oocys is sp. and Pseudocho ella sp., eached an a e age ela- i e abundance o only 2.5 – 4%. The mos com- mon axa in all samplings (occu ence>60%) we e Oscilla o ia sp., Oocys is sp., Oscilla o ia limne ica, Ch oococcus sp. and Mono aphidium ci cinale (Table 3). Consequen ly, he di e si y o phy oplank on was e y low: an assemblage o jus one, wo o h ee axa domina ed wi h a ela- i e abundance >80% in mos o he samplings. The seasonal phy oplank on succession was di - e en in bo h yea s o s udy. In 2001, he blooms o cyanobac e ia (Oscilla o ia sp., Mic ocys is sp.,) al e na ed wi h a high densi y o dino lagel- la es (Amphidinium sp., Gymnodinium sp.), chlo ophy es (Oocys is sp., Mono aphidium sp.) and dia oms (Chae oce os sp.). Howe e in 2002, cyanobac e ia la gely domina ed o he mos pa o he yea while he densi y o dino lagella es and dia oms was g ea ly educed (Fig. 5). The high wa e u bidi y hinde ed he g ow h o subme sed aqua ic mac ophy es as only Po amoge on pec ina us g ew in he shallowe a eas, while he li o al ege a ion was mainly Limnology o Ta elo Lagoon 5 Figu e 4. Concen a ion o o-P in he su ace (solid line) and bo om wa e (dashed line) a he open si e du ing he s udy pe iod. Mean ± SD. Concen ación de o-P en la supe icie (línea con inua) y el ondo (línea discon inua) del cen o du an e el pe íodo de es udio. Table 2. Concen a ion o o-P (mg gDW-1) in he di e en P- ac ions o he ine sedimen (<0.1 mm) and he o al sedimen in May 2001. Mean ± SD. Concen ación de o-P (mg gDW-1) en las dis in as acciones de P en el sedimen o ino y el sedimen o o al de mayo 2001. Fe(OOH)~P CaCO3~P o g-Pacid o g-Palkali o g-P esidual Fine sedimen 99±2.6 110±22.3 209±23.7 364±34.8 52±8.4 To al sedimen 123±11.8 222±8.5 101±3.3 495±30.6 22±4.9 Limne ica 23(1-2) 11/10/04 10:04 Página 5 composed o Ph agmi es aus alis and Typha la i olia. A ew aqua ic in e eb a e species we e eco ded du ing he s udy pe iod (Table 4). Only 5 o i e species and 2 c us acean species we e iden i ied in he zooplank on. The o al densi y o he zooplank on gene ally anged be ween 100 and 2000 ind l-1, bu popula ion explosions we e common in o i e species such as B achionus plica ilis (max. 2025 ind l-1) and Ke a ella opica (max. 2118 ind l-1). The mini- mum alue o zooplank on densi y (6 ind l-1) was eco ded in June 2001 when he whole wa e column became anoxic. 6Se ano e al. Table 3. A e age ela i e abundance (F .) and occu ence (Occ.) o main phy oplank on species du ing he s udy pe iod. P omedio de la abun- dancia ela i a (F ) y ecuencia de apa ición (Occ.) de las p incipales especies del i oplanc on. Species F . (%) Occ. (%) Species F . (%) Occ. (%) CYANOBACTERIA DIATOMS Anabaena a . aspe a 0.1 13.6 Ampho a sp. 0.1 13.6 Anabaena a . spi oides 1.6 31.8 Cyclo ella meneghiniana 0.5 54.5 Anabaena aphanizomenoides 0.4 27.3 Cymbella sp. 0.1 4.5 Anabaena sp.1 0.1 13.6 Chae osce os sp. 3.9 45.4 Anabaena sp.2 0.1 9.1 F agilla ia a . cons uens <0.1 4.5 Anabaenopsis ci cula is 0.1 9.1 Melosi a sp. 0.1 9.1 Anabaenopsis sp. 0.1 4.5 Ni zschia palea 0.1 4.5 Aphanocapsa holsa ica 35.4 22.7 Ni zschia sp. 0.1 9.1 Aphanocapsa ince a 1.0 9.1 Uniden i ied penna e dia om 0.2 9.1 Caelosphae ium sp. 1.3 22.7 CHRYSOPHYTES Calo h ix sp. 0.1 4.5 Mallomonas sp <0.1 4.5 Chl ogloea sp. 0.1 4.5 Och omonas sp. 0.1 18.2 Ch oococcus a . dispe sus 3.0 27.3 Uniden i ied ch ysophy a 0.1 4.5 Ch oococcus sp. 0.8 63.6 CHLOROPHYTES Gomphosphae ia sp. 0.3 4.5 Ankis odesmus sp. 0.1 4.5 Lynbya sp. 0.1 18.2 Coelas um sp. 0.1 9.1 Me ismopedia sp. 0.1 9.1 Chlamydomonas sp. 0.1 4.5 Mic ocys is sp. 30.0 54.5 Chlo ella sp. 0.9 13.6 Oscilla o ia limne ica 1.4 63.6 Mono aphidium ci cinale 1.0 63.6 Oscilla o ia sp. 0.4 77.3 Mono aphidium con o um 0.3 36.4 Spi ulina sp. 0.1 18.2 Oocys is sp. 3.4 72.7 Synechococcus sp.0.1 13.6 Pando ina sp. 0.1 4.5 Synechocys is sp. 0.5 9.1 Pi amidomonas sp. <0.1 4.5 CRYTOPHYTES Pseudochlo ella sp. 3.1 4.5 C yp omonas sp.1 3.5 59.1 Scenedesmus sp. <0.1 4.5 C yp omonas sp.2 0.1 27.3 Sch oede ia sp. 0.1 40.9 Ch oomonas a . acu a 0.1 9.1 Uniden i ied Chlo ococcal 0.8 54.5 DINOFLAGELLATES Uniden i ied Vol ocal 0.1 9.1 Amphidinium sp. 3.2 40.9 Glenodinium sp.0.1 9.1 Gymnodinium sp. 2.6 50.0 Gymnodinium sp.2 0.1 9.1 Figu e 5. Changes in he ela i e abundance o phy oplank on composi ion in he su ace a he open si e du ing he s udy pe iod. Cambios en la abundancia ela i a de la composición i oplanc ónica en la supe icie a lo la go del pe íodo de es u- Limne ica 23(1-2) 11/10/04 10:04 Página 6 The ela i e abundance o Chi onomus plumo- sus inc eased in au umn-win e (347-15000 ind m-2 in he open-si e and 521-31900 ind m-2 in he li o al si e) and dec eased in sp ing-summe (0-140 ind m-2 in he open-si e and 0-1945 ind m-2 in he li o al si e), eaching ze o du ing June-July 2001 (open si e) and June-Augus 2002 (bo h li o al and open si es). DISCUSSION Due o i s a i icial o igin as an ex ac i e pi , he su ace basin o he lagoon is limi ed o i s sho eline so i is basically ed by g ound wa e and di ec ain all. The impo ance o g ound wa e eeding is suppo ed by he inc ease in conduc i i y du ing ainy pe iods. The salini y o he i e bed aqui e o he Guadalqui i Ri e is e y high in his a ea due o a ossil aqui e below he es ua y (IGME, 1975) and o he pa ial in usion o seawa e (Na a o Al a gonzález e al., 1993). Addi ionally, he high a io o Cl-: SO42-, and he ela ion o Cl->SO42->CO3H-in hype haline wa e s is ypi- cal o coas al lagoons (Alonso, 1998). Al hough he su ace o he Ta elo lagoon is no connec ed o he es ua y, seawa e can in luence he ionic composi ion o he lagoon h ough bo h g ound wa e seepage and sp ay. The high concen a ions o bo h NO3-and NO2-in he wa e and hei posi i e co ela ion o ain all is also an indica ion o he impo ance o g ound wa e eeding in his lagoon. The g ound wa e o he Guadalqui i i e bed is pollu ed wi h N as high NO3-concen a ions (ca. 8 mM) we e al eady de ec ed in his a ea in 1987 (Na a o Al a gonzález e al., 1993). The amoun o NO3- eco ded in his lagoon (up o 20.3 mM) was e en la ge han ha ound in he eu ophic lagoons o Ad a which ecei ed he di ec inle o ag icul u al uno (Ca illo e al., 1996). In con as , NO2- ended o be e y low and NH4+was he dominan ino ganic o m o N in o he aqua ic en i onmen s o he Doñana a ea such as he empo a y ponds on aeolian sand (Se ano & Toja, 1995). The load o NO3- and NO2-du ing ainy pe iods declined ab up ly du ing bo h summe s when NO3-concen a ion eached ze o in he bo om wa e o his lagoon. The o al concen a ion o DIN also dec eased du ing bo h summe s and was minimal in June 2001. The e o e, DIN showed a seasonal pa e n o en ichmen in au umn-win e due o g ound wa e seepage, and o decline in summe due o bo h deni i ica ion and NO3-assimila ion. In spi e o he mixing c ea ed by he equen coas al winds, signi ican di e ences be ween he su ace and he bo om o he wa e column we e de ec ed, pa icula ly in summe , in ela- ion o se e al limnological a iables, such as he concen a ion o phy oplank on, dissol ed oxygen, pH, and suspended solids. Thus, bo h he spa ial and empo al a iabili y o hose a iables ela ed o he p ima y p oduc ion we e coupled in a seasonal pa e n o e ical seg e- ga ion. The ab up ex inc ion o he ligh pene- a ion and he di e en a ailabili y o nu ien s in he wa e column can accoun o his pa e n. In con as o he seasonal pa e n o N, he dynamics o P luc ua ed in pulses. The concen- a ion o o-P in bo h he bo om wa e and he in e s i ial wa e peaked du ing pe iods o anoxia in he deep wa e . The e a e h ee hypo hesis o explain he elease o o-P om anoxic sedi- Limnology o Ta elo Lagoon 7 Table 4. Lis o aqua ic mic oin e eb a e species. Lis a de mic oin- e eb ados acuá icos. ROTIFERA B achionus plica ilis B. calyci lo us B. no ae-zelandiae Ke a ella opica Tes udinella pa ina CLADOCERA Daphnia longispina COPEPODA Acan hocyclops c . kie e i ISOPODA Sphae oma se a um GASTROPODA Physella acu a Po amopy gus an ipoda um DIPTERA Chi onomus plumosus Limne ica 23(1-2) 11/10/04 10:04 Página 7 men s: h ough he educ ion o Fe(OOH)~P, he acidi ica ion o sedimen s, and he mine aliza- ion o o ganic P-compounds such as phy a e (Gol e man e al., 1998). The decomposi ion o o ganic ma e in he sedimen is a simple mechanism o o-P elease ha canno be uled ou (P ai ie e al.,2002), especially in his case, when To -P and o ganic ma e in he sedimen a e highly co ela ed. The concen a ion o To -P in he sedimen o his lagoon ell wi hin he ange o o he eu ophic shallow sys ems such as he coas al lagoons o Ad a (De Vicen e e al., 2003) and he Doñana empo a y ponds (Díaz- Espejo e al., 1999). The majo i y o he To -P in he sedimen o his lagoon was composed o o ganic P- ac ions as in he case o he Doñana ponds (Díaz-Espejo e al., 1999; Se ano e al., 2000) whe e To -P and sedimen o ganic ma e we e also co ela ed (Jaú egui & Toja, 1993). The e o e, he eu ophic s a e o his lagoon ensu ed a high in e nal P-loading as he concen- a ion o plank onic chlo ophyll ain he wa e column a e aged 137.5 µg l-1 du ing he s udy pe iod. An e en highe concen a ion o chlo o- phyll ahas been eco ded in he hype eu ophic coas al lagoon Albu e a o Valencia (200-600 µg l-1) ha was also domina ed by cyanobac e ia (Vicen e & Mi acle, 1992). The a iabili y o he local wind speed can also gene a e pulse-scale e en s ha may p o- duce a signi ican e ec on he unc ioning o he sys em unde he p esen condi ions o high phy oplank on p oduc ion. This is he case o an episode o anoxia, on 12 h June 2001, ha deple ed he en i e wa e column o dissol ed oxygen a e a pe iod o in e mi en mixing gene a ed by an al e na ion o s ong winds and calms. Du ing in e mi en mixing, cyanobac e- ia, such as Mic ocys is colonies, mig a e upwa d b inging abou he de elopmen o blooms (Eas hope & Howa d, 1999). In ac , Mic ocys is bloomed in his lagoon in May 2001 esul ing in he minimum alue o ligh pene a ion in 2001 and he highes alue o o - P in he pa icula e suspended ma e ial o bo h he su ace and he bo om wa e . One mon h la e , he episodic anoxia ook place and he wa e column became dis inc ly seg ega ed in wo laye s: a su ace laye wi h mo e chlo o- phyll aand less o-P han he bo om laye . The a ailabili y o nu ien s in a dim ligh en i on- men could ha e a ou ed he la e g ow h o Oscilla o ia. I is well known he abili y o cyanobac e ia o al e na e be ween au o ophic and he e o ophic me abolisms and, in pa icu- la o Oscilla o ia limne ica, o al e na e be ween oxygenic and a non-oxygenic pho o- syn hesis when he sulphide concen a ion is high and he a ailable PAR is low (A las & Ba ha, 1998). Some algal species a e also able o u n o a he e o ophic me abolism when ligh a ailabili y is e y low and he e is a high pool o dissol ed o ganic compounds de i ed om he dying cells (Tuchman, 1996; So okin, 1999). Tha is he case o he dino lagella e Gymnodinium and he dia om Chae oce os ha bloomed in July and Augus 2001, espec i ely. In he long un, cyanobac e ia a e known o domina e he phy oplank on communi y in eu ophic sys ems due o he many ad an ages hey can exhibi unde luc ua ing condi ions, such as hei me abolic e sa ili y, hei gas esicles, hei nu ien up ake a e y low o-P concen a ion and hei capaci y o h i e in educing condi ions (So okin, 1999). In his lagoon, he in e mi en mixing, he di e en ime-scales o nu ien a ailabili y, he a iabili- y o he unde wa e ligh en i onmen and o he educing condi ions, c ea ed a luc ua ing en i onmen mos sui able o cyanobac e ia. As i can be expec ed in eu ophic sys ems unde s ess, he numbe o axa was ela i ely low and he communi ies we e domina ed by only a ew species. Simila ly, mo e han 80% o he o al phy oplank on biomass was comp ised by no mo e han h ee species du - ing mos pa o he yea in he hype eu ophic lagoon Albu e a o Valencia (Romo & Mi acle, 1995). E en an oppo unis ic species, such as Chi onomus plumosus, common in eu ophic en i onmen s (P a , 1991) disappea ed om he sedimen su ace du ing summe . Simila ly, an indica o o bo h eu ophic and mine alised wa e s such as Po amoge on pec ina us 8Se ano e al. Limne ica 23(1-2) 11/10/04 10:04 Página 8 (Sche e , 1998) was e y sca ce and es ic ed o he shallowe a eas. Al hough he s udy pe iod was o sho o d aw any endency, he e we e some indica- ions o a quick p og ess owa ds an e en high- e ophic deg ee: he concen a ion o bo h o al and o ganic suspended ma e inc eased in 2002 wi h espec o 2001 and he a e age summe chlo ophyll was also highe in 2002 as well as he ela i e abundance o cyanobac e- ia. A endency owa ds a mo e ad anced s age o eu ophica ion is quie likely as eu ophic en i onmen s domina ed by cyanobac e ia can c ea e a sel - egula ed sys em o main ain s a- ble blooms in lakes (Sakamo o & Okino, 2000; Gibson e al., 2000). Howe e in he con ex o coas al lagoons, ansi ional s ages can also lead o uns able si ua ions (Comín e al., 1999). A e yea s wi hou appa en changes, ca as ophic shi s ha e d as ically changed he aqua ic communi ies o he coas al lagoon Albu e a o Valencia (Vicen e & Mi acle, 1992). The coas al lagoons o Comacchio (I aly) ha e eached a p eca ious equilib ium unde he absolu e dominance o cyanobac e ia wi h he al e na ion o au o ophic and he e- o ophic s ages when he aqua ic auna c ash- es o unde ec able numbe s du ing dys ophic c isis (So okin, 1999). The e o e, as p ima y p oduc ion inc eases in he lagoon o Ta elo, he ood a ailable o he Whi e-headed duck (Oxyu a leucocephala) will likely dec ease as his species eeds mainly on chi onomids, and seconda y on aqua ic subme sed mac ophy es (G een e al., 1999). ACKNOWLEDGEMENTS We hank Jose Ma ia A ana o his help and pa ience, and Luis Rod iguez “Fon” o his col- labo a ion. We a e also hank ul o he ange s o he Doñana Na u al Pa k, o S a. Lola and he amily, o he people o Ven a El Raspa and Casa Ru al La Algaida. The Conseje ía de Medio Ambien e, Jun a De Andalucía, suppo - ed his p ojec . REFERENCES ALONSO, M. 1998. Las lagunas de la España penin- sula . Limne ica, 15: 1-176. APHA. 1985. S anda d me hods o he examina ion o wa e and was ewa e . 16 h ed. Ame ican Public Heal h Associa ion. ATLAS, R. M. & R. BARTHA. 1998. Mic obial Ecology. Fundamen als and applica ions. Benjamin/Cummings Publishing Company, Inc. Menlo Pa k, 694 pp. CARRILLO, P., P. SÁNCHEZ-CASTILLO, L. CRUZ-PIZARRO & R. MORALES. 1996. Cambios cíclicos y endencias a la go plazo en la salinización de ecosis emas luc uan es (Albu e as de Ad a). E idencias de eu o ización y con ami- nación. Limne ica, 12: 59-65. COMÍN, F. A, F. MENÉNDEZ, J. A. ROMERO, O. HERNÁNDEZ, M. MARTÍNEZ & A. CHACÓN. 1999. Indicado es ecológicos y he amien as pa a la ges ión de ecosis emas acuá icos en la zona cos e a. Limne ica, 16: 61-68. DE GROOT, K. J. & H. L. GOLTERMAN. 1990. Sequen ial ac iona ion o sedimen phospha e. Hyd obiologia, 192: 143-149. DE VICENTE, I., L. SERRANO, V. AMORES, V. CLAVERO & L. CRUZ-PIZARRO. 2003. Sedimen phospha e ac iona ion and in e s i ial wa e phospha e concen a ion in wo coas al lagoons (Albu e as de Ad a, SE Spain). Hyd obiologia, 492: 95-101. DÍAZ-ESPEJO, A., L. SERRANO & J. TOJA. 1999. Changes in sedimen phospha e composi ion o seasonal ponds du ing illing. Hyd obiologia, 392: 21-28. GIBSON, C. E., R. H. FOY & S. D. LENNOX. 2002. The ise and ise o Plank o h ix aga dhii in Lough Neagh 1969-1997. Ve h. In e na . Ve ein. Limnol., 27: 2913-2916. GREEN, A. J., A. D. FOX, B. HUGHES & G. M. HILTON. 1999. Time-ac i i y budge s and si e selec ion o Whi e-headed Ducks Oxyu a leuco- cephala a Bu du Lake, Tu key in la e win e . Bi d S udy, 46: 62-73. GOLTERMAN, H. L. 1991. Di ec nessle iza ion o ammonia and ni a e in esh-wa e . Annls Limnol., 27: 99-101. GOLTERMAN, H. L. 1996. F ac iona ion o sedi- men phospha e wi h chela ing compounds: a sim- pli ica ion, and compa ison wi h o he me hods. Hyd obiologia, 335: 87-95. Limnology o Ta elo Lagoon 9 Limne ica 23(1-2) 11/10/04 10:04 Página 9