THE FRESHWATER MUSSEL Margaritifera Margaritifera (L.) in GALICIA (NW of SPAIN). PRELIMINARY STUDY in the RIVERS EO and MASMA
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THE FRESHWATER MUSSEL Margaritifera margaritifera (L.) IN GALICIA (NW OF SPAIN). PRELIMINARY STUDY IN THE RIVERS EO AND MASMA Fernández, C.1; Outeiro, A.2, Ondina, P.2, Amaro, R.1 & San Miguel, E.1 (1) Dpto. Xenética. Fac. de Veterinaria. USC. 27002 Lugo. Spain. (2): Dpto. Bioloxía Animal. Fac. de Veterinaria. USC. 27002 Lugo. Spain. [email protected] INTRODUCTION Throughout the last century, the populations of the freshwater bivalve Margaritifera Masma river Eo river Cantabric Sea margaritifera have suffered drastic decreases in all their geographical extension (Young et al., 2001). Many populations have disappeared and others are unable to reproduce successfully. The eutrophication of the rivers is considered the main cause, which is Foz r M1 determinant for the establishment and survival of young mussels (Bauer, 1986). This e eutrophication is caused mainly by intensive agriculture and anthropogenic activities from v Ribadeo i the growing urban areas. r a M3 Seasonally punctual measures of water quality were used to evaluate the degree of m s eutrophication. Besides, maps and satellite images were used to evaluate the degree of a alteration of the environment (Fig.1), specially of the riparian forests (Fig. 2). Both M M4 technologies were used to measure possible impacts on the populations of M. margaritifera. M2 In this context we study several populations of M. margaritifera located in two close rivers (Masma and Eo). Both rivers present different hydrological and environment Lourenzá characteristics. Fig. 4.- Frequency distribution of shell lengths in Masma and Eo M5 We analyze here the density and structure of the populations of M. margaritifera looking for possible relationships with water quality and the surrounding environment of M1 Eo1 r both rivers. Mondoñedo e iv r o E A B A Pontenova Agricultural land with natural vegetation Agricultural land and pastures Eo1 M2 Eo2 Fig 2. - The forest on the riverbank serves as a filter against the erosion Sections of undisturbed riparian and eutrophication caused by the agricultural activities, but it must be forest sufficiently developed. A: Section with a well developed forest on the bank. Eo2 B: Section in which the forest is reduced to a single row of trees. Removal Urban settlements of vegetation also creates riverbank instability, leading to bank collapse and subsequent siltation. 10 Km Eo3 CHARACTERISTICS OF THE STUDIED RIVERS The rivers Masma and Eo are located in the NW Spain (Fig. 1). The distance between their mouths is around 18 km. They have stable populations of Salmo salar, S. trutta trutta and S. trutta fario, potential hosts of the glochidia of M. margaritifera. M3 Eo3 Eo4 The river Masma has a length of 46.2 km. It presents a basin of 291.3 km2 and a discharge rate of 6.4 m3/seg. The middle and high parts of the Masma river basin (upstream from the sampling areas) have 3249 ha of surface occupied by farming and pastures. Moreover two urban areas (Mondoñedo and Lourenzá) are crossed by tributaries of Masma and one of which flows through an outcrop of lime rock. The Eo river has a length of 79 km, a basin of 700 km2 and a discharge rate of 24.4 m3/seg. Upstream from the sampling area there are only 475 ha used for farming and pastures (SIAM on line). The water analyses are showed in Table 1. Masma river Eo river Summer Winter Summer Winter M4 Geographic location of the Masma and Eo rivers Mean SD Min Max Mean SD Min Max Mean SD Min Max Mean SD Min Max Eo4 pH 7.5 0.38 6.8 8 7.2 0.24 6.6 7.2 7.0 0.15 6.8 7.2 6.8 0.06 6.8 6.8 T (ºC) 16.5 0.70 15.8 17.7 10.0 0.30 9.6 10.2 17.5 1.95 16.2 20.4 7.0 0.35 6.8 7.3 Conductivity 162.3 18.60 99.9 192.1 93.0 9.90 77.8 104.3 107.0 10.04 99.9 114.1 76.2 0.56 75.8 76.6 Fig. 1. - The map shows the sampling stations and the areas of the river basin altered by Alkalinity 72.8 10.0 56.0 81.6 27.3 4.6 19.6 31.7 30.9 2.6 29.1 32.8 23.3 0.6 22.9 23.7 agricultural activities. NH4+ (mgL-1) 0.157 0.028 0.129 0.193 0.188 0.012 0.180 0.206 0.077 0.018 0.064 0.090 0.039 0.018 0.026 0.052 Eo river and their tributary streams has a length of 372 Km: 26% of them flow through agricultural Cl- (mgL-1) 8.84 0.78 8.50 10.00 12.28 0.43 11.60 12.70 8.90 0.14 8.80 9.00 11.25 2.33 9.60 12.90 lands and pastures. 2- -1 6.4 1.14 5.0 8.0 3.2 0.45 3.0 4.0 2.0 0.0 2.0 2.0 4.0 0.0 4.0 4.0 Masma and its tributaries have a length of 126 Km, 46,8% of them flow through agricultural land SO4 (mgL ) and pastures. Ca2+ (mgL-1) 24.34 3.66 18.20 27.12 6.06 1.27 4.90 8.13 8.49 2.04 7.05 9.93 9.72 1.34 8.78 10.67 Mg2+ (mgL-1) 5.33 0.73 4.21 6.13 1.47 0.25 1.30 1.89 2.38 0.34 2.62 2.14 3.29 0.23 3.13 3.46 ) ) ) ) ) ) ) ) 2 2 2 2 2 2 2 2 Table 1: Water analyses show a greater degree of eutrophication in the river Masma with M5 1798 m + 2, 3.164 ej. (1340 m 479 ej. ( 3.269 ej. (1375 m 3.030 ej. (1894 m 810 ej. (1735 m 2777 ej. (1554 m 11.278 ej. (1721 m 1.080 ej. (1104 m respect to the Eo: conductivity, NH4 and SO4 , were higher in the river Masma. pH, alkalinity and Ca2+ were also higher in the river Masma but these results may be explained 8 by the presence of a limestone outcrop. 7 ) 2 6 5 METHODOLOGY 4 Young mussel from Eo3 Five linear transects of 100m lenght were selected in the Masma river (M1-M5) and four in the Eo river (Eo1-Eo4), in areas 3 where the species was previosuly observed. 2 To obtain the population density (Fig. 4) we removed visible and buried specimens (up to 15 cm underground ) taking between 30 to 35 random samples from a surface of 0,25 m2. Results were analyzed using adaptive sampling method (Thompson, Densities average (Ej/m 1 Fig 3 - Frequency distribution of shell lengths for each 1992 ) sampling station. The specimens smaller than 65 mm 0 The structure of the populations was assess using the frequency distribution of shell lengths for each sampling point (Fig 3). N= M5 M4 M3 M1 Eo4 Eo3 Eo2 Eo1 (around 10 years old) are considered juvenils (in red) 33 to 60 specimens for each section . The measured specimens were returned to the river. (San Miguel, et al., 2004). Results show that the population of M. margaritifera in Fig. 4. Population densities in each of the sampling areas the Masma river are aged and they are not able to (no M2) reproduce successfully. In the other hand the juvenils in the Eo river, represent RESULTS an 31.7% in Eo1 population, 8.5% in Eo2, 19.2 % in Eo3 and they are absent in Eo4. The mapping of the land cover and land use (Fig 1) and the satellite images (Fig 2) show that the Masma river undergoes a greater agricultural and urban pressure, and a REFERENCES greater degree of alteration of the native riverbank vegetation. This is supported by the Bauer, G., 1986.- The status of the freshwater pearl mussel Margaritifera water analyses (Table 1), showing the Masma river a greater degree of eutrophication. margaritifera L. in the south of its european range. Biological Conservation, 38, 1-9. The eutrophication seems to have consequences on the population structure of M. A B C Machordom A, Araujo R, Erpenbeck D, Ramos MA. 2003. Phylogeography and margaritifera on both rivers. Fig. 3 clearly shows that individuals under 65 mm are conservation genetics of endangered European Margaritiferidae (Bivalvia: practically absent in the Masma river but appear in a significant number in the Eo river; Unionoidea). Biological Journal of the Linnean Society, 78, 235–252. with the exception of Eo4 the unique one surrounded by agricultural lands (Fig.1). MAPA. Visor gráfico SigPac (On line). FEGA. Ministeria de agricultura pesca y alimentación. V. 3.0 (Consulted in 2006 July 4).:http://sigpac.mapa.es/fega/visor However, the different degree of eutrophication does not seem to have relation on the San Miguel, E., Monserrat, C., Fernández, C., Amaro, R., Hermida, M., Ondina, densities of population of the studied areas (Fig 4), so the adult of M. margaritifera could P. & Altaba, C.R., 2004.- Growth models and longevity of freshwater peral bear temporally a greater variety of surroundings (Fig 5). mussels (Margaritifera margaritifera) in Spain. Canadian Journal of Zoology: 82: M. margaritifera is listed as “threatened” by IUCN (2004), and recently it has been 1370-1379. considered one of the most critically endangered freshwater mussel in the world SIAM. Corine Landcover 2000 (On line). Consellería de Medio Ambiente. Xunta E F de Galicia.