Wetland Loss by Erosion in Odiel Marshes (SW Spain)

We land Loss by E osion in Odiel Ma shes (SW Spain) Au ho s: Cas illo, J.M., Rubio-Casal, A.E., Luque, C.J., Nie a, F.J., and Figue oa, M.E. Sou ce: Jou nal o Coas al Resea ch, 36(sp1) : 134-138 Published By: Coas al Educa ion and Resea ch Founda ion URL: h ps://doi.o g/10.2112/1551-5036-36.sp1.134 BioOne Comple e (comple e.BioOne.o g) is a ull- ex da abase o 200 subsc ibed and open-access i les in he biological, ecological, and en i onmen al sciences published by nonp o i socie ies, associa ions, museums, ins i u ions, and p esses. You use o his PDF, he BioOne Comple e websi e, and all pos ed and associa ed con en indica es you accep ance o BioOne’s Te ms o Use, a ailable a www.bioone.o g/ e ms-o -use. Usage o BioOne Comple e con en is s ic ly limi ed o pe sonal, educa ional, and non - comme cial use. Comme cial inqui ies o igh s and pe missions eques s should be di ec ed o he indi idual publishe as copy igh holde . BioOne sees sus ainable schola ly publishing as an inhe en ly collabo a i e en e p ise connec ing au ho s, nonp o i publishe s, academic ins i u ions, esea ch lib a ies, and esea ch unde s in he common goal o maximizing access o c i ical esea ch. Downloaded F om: h ps://bioone.o g/jou nals/Jou nal-o -Coas al-Resea ch on 11 May 2020 Te ms o Use: h ps://bioone.o g/ e ms-o -use Jou nal o Coas al Resea ch, Special Issue 36, 2002 INTRODUCTION We land losses ha e been de ec ed in many es ua ies a ound he wo ld (CHUNG, 1982; DELAUNE e al., 1983; BARROS, 1996; BRIVIO, 1996; PSUTNY a n d MOREIRA, 2000), a ibu ing hei main mechanism o e osion. Thus, e osi e p ocesses such as unde mining o he d ainage channel banks ha e been cha ac e ised (PHILLIPS, 1986; KEARNEY and STEVENSON, 1991; GABET, 1998), which esul in s eeped slopes be ween ege a ed ma shes and ba e in e idal sedimen s (NYMAN e al., 1994). In e idal sedimen dynamics a e a key p ocess in he e olu ion o e oded ma shes, since hey de e mine he heigh o e osi e banks and a ec hei coloniza ion by ege a ion. In addi ion, he iden i ica ion o he causes o e osion and i s quan i ica ion a e necessa y in de eloping managemen s a egies o e oded we lands. This s udy was ca ied ou in he Odiel idal ma shes (SW Spain), whe e high bank e osion a es ha e been quan i ied in a sho e m s udy (CASTILLO e al., 2000a). He e, we aim o quan i y bank e osion and wi h e ical e osion / acc e ion a es on in e idal a eas o e a ou yea pe iod. STUDYAREA This s udy was ca ied ou in he Odiel idal sal ma shes in he join es ua y o Odiel and Tin o i e s (37º15’ - 37º37’N, 6º57’ - 6º58’W; SW Spain) (Fig. 1). T h i s Holocene es ua y is loca ed in a coas al a ea wi h a meso idal semidiu nal cha ac e . Mean idal ange is 2.10 m and mean sp ing idal ange is 2.97 m. Wa e le els ange be ween 0.40 and 3.37 m abo e Spanish Hyd og aphic Ze o (SHZ) (CASTELLANOS e al., 1994). The es ua y occupies a 25 km long s e ch o an incised i e alley and is unde lain by Neogene sandy-sil y sedimen s. The oldes es ua ine sedimen s ha e been da ed a 6.715 ± 115 y BP. Sedimen acc e ion a es (app oxima ely 5 mm yea -1) indica e as in illing o he es ua y du ing he wo las millennia (LARIO, 1996). In as uc u es such as dykes, b eakwa e s, ha bou s and wa e ese oi s ha e modi ied he hyd odynamic and he sedimen supply in he es ua y o Odiel and Tin o i e s (OJEDA e al. 1995). On he o he hand, he main channel o he es ua y is d edged con inuously o allow essel a ic. The Odiel ma shes, wi h an a ea o 7158 hec a es, we e decla ed a Biosphe e Rese e by UNESCO in 1983, and hey a e loca ed in a Medi e anean clima e (NIEVA and LUQUE, 1995). We land Loss by E osion in Odiel Ma shes (SW Spain) J.M. Cas illo†, A.E. Rubio-Casal †, C.J. Luque‡, F.J. Nie a‡ and M.E. Figue oa† †Depa amen o de Biología Vege al y Ecología, Facul ad de Biología, Uni e sidad de Se illa. Apa ado 1095, 41080-Se illa, Spain, [email p o ec ed] ‡Depa amen o de Ciencias Ag o o es ales. Uni e sidad de Huel a. ABSTRACT We land loss in many es ua ies a ound he wo ld, has been a ibu ed mainly o unde mining and collapse o channel banks. This s udy aims o quan i y bank e osion and e ical e osion/acc e ion a es on in e idal sedimen s in he Odiel idal ma shes (SW Spain). Bi-mon hly e osion/acc e ion measu emen s we e aken on eigh channels o e a ou yea pe iod, using ma ke s (i on s akes) loca ed on in e idal a eas and on e oding banks. The in ensi y o e osion di ides he Odiel ma shes in o wo zones. The no he n zone has low e osion a es (ho izon al e osion c. -20 cm yea -1 and e ical e osion / acc e ion be ween 0 and –1 cm yea -1), and coincides wi h low le els o human ac i i ies. The sou he n zone has highe e osion a es (ho izon al e osion c. -25 cm yea -1 and e ical e osion / acc e ion be ween 0 and –5 cm yea -1) and exhibi s highe le els o an h opogenic p essu e. The highes ho izon al and e ical e osion a es (c. -80 cm yea -1) we e eco ded on na iga ion channels. Ho izon al and e ical e osion showed a posi i e linea ela ionship ( 2= 0.66; P< 0.01), indica ing ha sedimen s mobilized by bank e osion a e no deposi ed on adjacen in e idal a eas. E osion led o ma u e ma sh habi a loss o c. 17000 m2 yea -1 and a sedimen mobiliza ion o c. 16500 m3 yea -1. ADDITIONALINDEXWORDS: acc e ion, an h opogenic p essu e, bank e osion, in e idal plain, Spa ina ma i ima. Jou nal o Coas al Resea ch SI 36 134-138 (ICS 2002 P oceedings) No he n I eland ISSN 0749-0208 Downloaded F om: h ps://bioone.o g/jou nals/Jou nal-o -Coas al-Resea ch on 11 May 2020 Te ms o Use: h ps://bioone.o g/ e ms-o -use Ma sh E osion, Spain 135 Jou nal o Coas al Resea ch, Special Issue 36, 2002 METHODS Bank e osion by unde mining and e ical e osion / acc e ion a es on in e idal sedimen s we e measu ed on he eigh main channels o he Odiel Ma shes, bi-mon hly om May - Augus 1996 o July 2000 (Fig. 1). A ne wo k o 298 ma ke s was se up (Table 1). These consis ed o i on s akes app oxima ely 1.5 m all and 1 cm in diame e (Fig.2). Ma ke s we e inse ed o a dep h o 1 m, be ween +1.0 m and +2.5 m o e SHZ on in e idal plains and o e e osi e banks. The dis ance om he sedimen su ace o he op o he ma ke s was measu ed o quan i y e ical e osion / acc e ion dynamic; he dis ance om he edge o he bank o he ma ke base was measu ed o quan i y bank ho izon al e osion (Fig. 2). This me hod has been used by many au ho s (WOLMAN, 1959; RANWELL, 1964; HUBBARD and STEBBINGS, 1968; RANWELL, 1972; KING, 1975), since i allows epea ed measu emen s o e osion and acc e ion a he same loca ion. Nega i e alues indica e e osion and posi i e alues co espond o acc e ion. Mean bank heigh (n = 6) was measu ed a e e y channel o quan i y he olume o mobilized sedimen by ho izon al e osion. Analysis was ca ied ou using ‘S a is ica’ 5.1 (S a so Inc.). Pea son co ela ion coe icien s we e calcula ed be ween e osion / acc e ion a es. Ra es o e osion / acc e ion on di e en channels we e compa ed using one- way analysis o a iance. Leas signi ican di e ences (LSD) be ween means we e calcula ed only i he F- es was signi ican a he 0.05 le el o p obabili y. Da a we e es ed o homogenei y o a iance wi h he Le ene es (P> 0.05). Figu e 1. Loca ion o Odiel es ua y in The Ibe ian Peninsula and map o Odiel Ma shes. S udied channels a e numbe ed om 1 o 8. Table 1. Mean ± SEM bank ho izon al e osion and in e idal plain e ical e osion / acc e ion (cm yea -1) du ing ou yea s in he main channels o Odiel sal ma shes (SW Spain). 1 -8 ± 2 -0.5 ± 0.5 2 -15 ± 3 -1.1 ± 1.3 3 -47 ± 12 -1.6 ± 0.3 4 -37 ± 6 -1.3 ± 0.5 5 -34 ± 7 -1.6 ± 0.7 6 -76 ± 9 -4.7 ± 0.7 7 -40 ± 6 -0.3 ± 1.0 8 -64 ± 9 -2.4 ± 0.4 Bank ho izon al e osion Channels in e idal plain e ical e osion / acc e ion Figu e 2. Diag am showing he placemen o ma ke s o e a bank, o measu e ho izon al e osion, and on an in e idal plain, o measu e e osion / acc e ion dynamic. Downloaded F om: h ps://bioone.o g/jou nals/Jou nal-o -Coas al-Resea ch on 11 May 2020 Te ms o Use: h ps://bioone.o g/ e ms-o -use Cas illo, Rubio-Casal, Luque, Nie a and Figue oa 136 Jou nal o Coas al Resea ch, Special Issue 36, 2002 RESULTS The in ensi y o bank ho izon al e osion and in e idal plain e ical e osion / acc e ion a ied signi ican ly be ween channels (F = 14.66, P < 0.0001; F = 4.44, P < 0.0001, espec i ely) (Table 1). E osion / acc e ion a es di ided he Odiel ma shes in o wo zones. In he No he n zone (channels 1 and 2) mean ho izon al e osion was less han -20 cm yea -1 and he mean e ical e osion / acc e ion a e was be ween 0 and -1 cm yea -1. In he Sou he n zone (channels 3, 4, 5, 6, 7 and 8) mean ho izon al e osion was o e -25 cm yea -1, wi h a maximum close o -80 cm yea -1, and he e ical e osion / acc e ion a e was be ween 0 and –5 cm yea -1 (Fig. 1). The highes ho izon al and e ical e osion a es we e eco ded on na iga ion channels –(channels 6 and 8). Bo h channels we e loca ed close o he es ua y inle and channel 8 was he wides channel. Ho izon al and e ical e osion showed a posi i e and linea ela ionship ( 2= 0.66; P< 0.01) a all si es (Fig. 3). E osion in he Odiel idal ma shes has led o a loss o ma u e high ma sh o c. 17000 m2yea -1, p o oked by bank e osion, and a sedimen mobiliza ion by bank and in e idal e osion o c. 16500 m3yea -1 (Table 2). This e osion hinde s he de elopmen o ma shes by successional p ocesses and limi s he success o p ima y colonize s. Figu e 3 Co ela ion be ween ho izon al and e ical e osion in eigh channels in Odiel Ma shes (SW, Spain). ( 2 = 0.66; P< 0.01). Table 1. Table 2. Numbe o ma ke s, leng h (m), heigh o bank (cm), e oded a ea (m2yea -1) and mobilized sedimen s (m3yea -1) – conside ing a mean in e idal plain wid h o 10 m- in eigh channels o Odiel Sal Ma shes. 1 25 11167 37 893 892 2 19 16393 40 2459 2793 3 23 8374 51 3936 3359 4 25 5643 58 2088 1949 5 35 6351 64 2159 2403 6 53 1981 93 1506 2325 7 20 9140 59 3656 2407 8 98 600 52 384 382 ∑298 59649 - 17081 16510 Channel Nº o ma ke s Leng h (m) Heigh (cm) E oded a ea (m2 yea -1) Mobilized sedimen s (m3 yea -1) DISCUSSION E osion / acc e ion dynamic di ides he Odiel idal ma shes in o wo zones: a no he n zone wi h low e osion a es, coinciding wi h low le els o human ac i i ies; and a sou he n zone wi h highe e osion a es and highe le els o an h opogenic p essu es ( ec ea ional, po and indus ial ac i i ies, in as uc u e ins alla ion, e c.). The highes e osion a es we e eco ded on na igable channels, sugges ing ha essel a ic may con ibu e o inc eased e osion (PEZESHKI and DELAUNE, 1996). Howe e , human ac i i ies causing e osion a e di icul o iden i y and quan i y in his s udy, since mo e han one ac o could be ac ing a he same ime. Many in as uc u es ha e been cons uc ed closed o Odiel ma shes ha may educe sedimen supply o he es ua y a ou ing ma sh e osion, such as b eakwa e s, ha bou s and wa e ese oi s. OJEDAe al. (1995) iden i ied an h opogenic al e a ions o he hyd odynamic condi ions o he Odiel ma shes, which may a ec e osion / acc e ion p ocesses h ough he modi ica ion o cu en s and sedimen supply (CHMURA e al., 2001). The lowe a es o e osion in he uppe es ua y migh also e lec lowe wa e ene gy, a sugges ion ha is also consis en wi h he obse a ion o highe e osion a es adjacen o he la ge na iga ion channels. On he o he hand, accele a ed sea le el ise could accele a e he loss o coas al we lands by e osion (ROGERS and MCCARTY, 2000). Downloaded F om: h ps://bioone.o g/jou nals/Jou nal-o -Coas al-Resea ch on 11 May 2020 Te ms o Use: h ps://bioone.o g/ e ms-o -use Ma sh E osion, Spain 137 Jou nal o Coas al Resea ch, Special Issue 36, 2002 I is in e es ing o no e, he posi i e and linea ela ionship be ween ho izon al and e ical e osion which indica es ha sedimen s mobilized by bank e osion a e no deposi ed on adjacen in e idal a ea. E osion on he Odiel ma shes has led o sedimen mobiliza ion o c. 16500 m3yea -1. Ou esul s sugges ha some o hese sedimen s, which a e dispe sed by cu en s and ides, could con ibu e o he sil ing o he channels o he es ua y. Conside able economic expense is incu ed in d edging na igable channels o enable he en ance o la ge ships in o de Po o Huel a. Fu he mo e, e osion is leading o he loss o c. 17000 m2o ma sh pe yea . Al hough low ma shes a e p esen ly o ming in he sou he n pa o he es ua y, mos o he los ma shes we e ma u e ones ha had aken a long ime o o m and we e ac ing as expo e s o o ganic ma e (HAZELDEN and BOORMAN, 1999). The loss o hese middle and high ma shes educes he habi a o ce ain communi ies, con ibu ing o a dec ease in species and habi a di e si y, since hey a e eplaced by ba e in e idal a eas. Ou esul s may con ibu e o he managemen o e oded ma shes, in o de o assis hei es o a ion by adminis a i e and cons uc i e geo-ecological me hods (CASTILLO e al., 2000a). These include he in oduc ion o ma sh plan species adap ed o high looding pe iods, such as Spa ina ma i ima (CASTILLO e al., 2000b), which enhance a es o low ma sh de elopmen by apping sedimen s (MOELLER e al., 1996). ACKNOWLEDGEMENTS This s udy was ca ied ou h ough an in es iga ion ag eemen wi h he Po Au ho i y o Huel a and he Gene al Di ec o a e o En i onmen al P o ec ion o he Jun a de Andalusia. We also hank he Di ec o a e o he Odiel Ma shes Na u al Pa k o collabo a ion, and he Jun a o Andalusia o he awa d o an FPI schola ship. Downloaded F om: h ps://bioone.o g/jou nals/Jou nal-o -Coas al-Resea ch on 11 May 2020 Te ms o Use: h ps://bioone.o g/ e ms-o -use Cas illo, Rubio-Casal, Luque, Nie a and Figue oa 138 Jou nal o Coas al Resea ch, Special Issue 36, 2002 LITERATURE CITED BARROS, A . P., 1996. An e alua ion o model pa ame e isa ions o sedimen pa hways: a case s udy o he Tejo es ua y. Con inen al Shel Resea ch, 16(13), 1725-1749. BRIVIO, P.A. and ZILIOLO, E., 1996. Assessing we land changes in he Venice lagoon by means o sa elli e emo e sensing da a. Jou nal o Coas al Conse a ion, 2(1), 23-32. CASTELLANOS, E.M., FIGUEROA, M.E. and DAVY, A.J., 1994. Nuclea ion and acili a ion in sal ma sh succession: in e ac ions be ween Spa ina ma i ima and A h ocnemum pe enne. Jou nal o Ecology, 82(2), 239- 248. CASTILLO, J.M.; LUQUE, C.J.; CASTELLANOS, E.M. and FIGUEROA, M.E., 2000a. 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