Marine environmental proxies
1
Geochemical and microfaunal proxies to assess environmental quality conditions in Bilbao estuary (1997-2012) Nereo Cuesta 1 , Alejandro Cearreta 1 1 Dpto de Estratigrafía y Paleontología UPV/EHU; This project concludes an monitoring study about the environmental improvement in the estuary of Bilbao, which began in 1997. Such study have used tools based on geological microfaunal analysis (using benthic foraminifera) and geochemical (by heavy metals) in surface sediments of the estuary, in order to assess their quality and environmental changes over the last 15 years. For this have been identified the main species of foraminifera present in the estuary, their abundance and spatial distribution, together with the presence of heavy metals in surface sediments of the estuary. 1. Background The natural characteristics of Bilbao’s estuary were modified by a large urban settlement, industrial and port. . The iron ore mining industry took to the development the city of Bilbao in the mid-nineteenth century. In 1885, the original estuary was reduced to an artificial waterway canal that connected the city to the open sea. During the past 150 years, the estuary has received all kinds of waste from mine and industrial works. 2. Materials and Methods Geochemical Results: In general it is observed that the results of heavy metal concentrations continue the decreasing trend that had been observed since 2003. In contrast, in this study (2012) a persistent pollution in Galindo (8) and Udondo stations (12) can be highlighted. In that points two peaks of concentration of lead and zinc can be seen. Sudden increases observed in some seasons between 2000 and 2012 are due to punctual dredging and dumping. The estuary of Bilbao is located on the north coast of the Iberian Peninsula. Tides are semidiurnal, ranging between 4.6 m and 1.2 m. The tidal channel flows into a large bay called el Abra(3.5 km of average width and 30 m of maximum depth). Main freshwater entrances are from Ibaizabal and Nervión rivers (68%), while the rest comes from smaller tributaries such as: Kadagua (27%), Galindo (4%), Asua (0.7%) and Gobelas (0.3%). 3. Study area 4. Results and discussion Leorri et al., 2008: Bilbao estuary map with the location of the sampling areas.1-Atxuri; 2-La Ribera; 3-Zorroza; 4-Elorrieta; 5-Burtzeña; 6-Asua; 7- Rontegi; 8-Galindo; 9-Erandio;10-Simondrogas; 11-Axpe; 12-Lamiako; 13- La Benedicta, y 14-Arriluze. WWTP- waste water treatment plant. Sample fixa*on in ethanol (80cm 3 ) 1mm sieve (large organic fragments) 63 μm sieve (fine washing) Rose Bengal staining Living organisms (dyed) Dead organisms (not dyed) H 2 O The sample is cleaned to eliminate the dye excess H 2 O Sample drying at 60 o C Trichlorethylene flota*on method Reflected light binocular stereoscopic microscope observa*on H 2 O Foraminifera extrac*on Species Shell type Hyaline Porcelaneous Agglu*nated Autochthonous Allochthonous Sorted by: Shell origin Total area: 150 ha Length: 15 km Width: 100 m Depth: 10 m Watershed: 1.700 km 2 Freshwater contribution: 25 m 3 s -1 Seawater contribution: 230 m 3 s -1 To carry out this study 13 different points in Bilbao estuary were sampled, 12 of which are within the estuary and one in the bay (Fig. 1). Microfaunal Analysis: To extract the foraminiferal sediment intended for the quantitative analysis, we used a plastic ring of 40 cm 2 in area and 1 cm deep. Two pseudo-replica were taken to prevent foraminifera stain characteristic distribution. The ring measures were selected to ensure a representative number of living foraminifera (300 individuals) Materials and methods diagram used in the classification process of foraminifera Geochemical Analysis: The analysis of samples for geochemical characterization was performed in the laboratory Actlabs (Canada). The samples were dried, crushed and analyzed by fluorescence spectrometry X-rays. Because of it the natural ecosystems have been degraded to the point of causing conditions close to anoxia in its waters , with low concentrations of dissolved oxygen and high concentrations of organic matter and heavy metals. However, between the 1980s and 1990 has been observed a decrease in the flow of organic matter and heavy metals, caused by an economic recession and improvement of the environmental policies and in the waste treatment systems of the city. In the dead association have been extracted more than 5,400 shells of dead foraminifera, belonging to 21 different species, and showing a representative value of more than 300 individuals in all stations except Burtzeña (5), where more than 120 shells were found. Regarding the last study in 2009 there is an increase of individuals and an species decreased from 29 to 21. Micropaleontological results: In the living association (histogram) have been taken a total of 4042 living foraminifera, belonging to 11 different species, and showing a representative value of more than 300 individuals in five different stations, three stations more then in 2009. The number of living individual per unit volume (80 cm 3 ) at the surface of the sediment has increased compared with the previous sampling. The environmental conditions are becoming more favorable for growth and reproduction of foraminifera in the estuary. Acknowledgements This work has been funded thanks to the projects 80IT365-10 (Basque Government, Harea- Grupo de Investigación en Geología Litoral), UFI11/09 (Universidad del País Vasco UPV/EHU, Unidad de Formación e Investigación en Cuaternario), and thanks to "La Caixa” Foundation. (Aerial photo, 1957)
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Analysis of the water pollution in Bilbao estuary (Northern Spain) by microfaunal and geochemical proxies (1997-2012). Paleontology and Stratigraphy Department.
Transcript of Marine environmental proxies
Geochemical and microfaunal proxies to assess environmental quality conditions in Bilbao estuary (1997-2012)!
!
Nereo Cuesta1, Alejandro Cearreta1!1Dpto de Estratigrafía y Paleontología UPV/EHU; !
This project concludes an monitoring study about the environmental improvement in the estuary of Bilbao, which began in 1997. Such study have used tools based on geological microfaunal analysis (using benthic foraminifera) and geochemical (by heavy metals) in surface sediments of the estuary, in order to assess their quality and environmental changes over the last 15 years. For this have been identified the main species of foraminifera present in the estuary, their abundance and spatial distribution, together with the presence of heavy metals in surface sediments of the estuary.!
1. Background !
The natural characteristics of Bilbao’s estuary were modified by a large urban settlement, industrial and port. . The iron ore mining industry took to the development the city of Bilbao in the mid-nineteenth century. In 1885, the original estuary was reduced to an artificial waterway canal that connected the city to the open sea. During the past 150 years, the estuary has received all kinds of waste from mine and industrial works.!
2. Materials and Methods!
Geochemical Results: In general it is observed that the results of heavy metal concentrations continue the decreasing trend that had been observed since 2003. In contrast, in this study (2012) a persistent pollution in Galindo (8) and Udondo stations (12) can be highlighted. In that points two peaks of concentration of lead and zinc can be seen. Sudden increases observed in some seasons between 2000 and 2012 are due to punctual dredging and dumping.!
The estuary of Bilbao is located on the north coast of the Iberian Peninsula. Tides are semidiurnal, ranging between 4.6 m and 1.2 m. The tidal channel flows into a large bay called el Abra(3.5 km of average width and 30 m of maximum depth). Main freshwater entrances are from Ibaizabal and Nervión rivers (68%), while the rest comes from smaller tributaries such as: Kadagua (27%), Galindo (4%), Asua (0.7%) and Gobelas (0.3%).!
3. Study area!
4. Results and discussion!
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Leorri et al., 2008: Bilbao estuary map with the location of the sampling areas.1-Atxuri; 2-La Ribera; 3-Zorroza; 4-Elorrieta; 5-Burtzeña; 6-Asua; 7-Rontegi; 8-Galindo; 9-Erandio;10-Simondrogas; 11-Axpe; 12-Lamiako; 13-La Benedicta, y 14-Arriluze. WWTP- waste water treatment plant.
!
Sample fixa*on in ethanol (80cm3)
1mm sieve (large organic fragments)
63 μm sieve (fine washing)
Rose Bengal staining Living organisms (dyed)
Dead organisms (not dyed)
H2O
The sample is cleaned to eliminate
the dye excess H2O
Sample drying at 60o C
Trichlorethylene flota*on method
Reflected light binocular stereoscopic microscope
observa*on
H2O
Foraminifera extrac*on
Species Shell type
Hyaline Porcelaneous Agglu*nated
Autochthonous Allochthonous
Sorted by:
Shell origin
!
Total area: 150 ha
Length: 15 km
Width: 100 m
Depth: 10 m
Watershed: 1.700 km2
Freshwater contribution:
25 m3s-1
Seawater contribution:
230 m3s-1 !
To carry out this study 13 different points in Bilbao estuary were sampled, 12 of which are within the estuary and one in the bay (Fig. 1). Microfaunal Analysis: To extract the foraminiferal sediment intended for the quantitative analysis, we used a plastic ring of 40 cm2 in area and 1 cm deep. Two pseudo-replica were taken to prevent foraminifera stain characteristic distribution. The ring measures were s e l e c t e d t o e n s u r e a representative number of l iving foraminifera (300 individuals)
Materials and methods diagram used in the classification process of foraminifera
Geochemical Analysis: The analysis of samples for geochemical characterization was performed in the laboratory Actlabs (Canada). The samples were dried, crushed and analyzed by fluorescence spectrometry X-rays.
Because of it the natural ecosystems have been degraded to the point of causing conditions close to anoxia in its waters , with low concentrations of dissolved oxygen and high concentrations of organic matter and heavy metals. However, between the 1980s and 1990 has been observed a decrease in the flow of organic matter and heavy metals, caused by an economic recession and improvement of the environmental policies and in the waste treatment systems of the city.
In the dead association have been extracted more than 5,400 shells of dead foraminifera, belonging to 21 different species, and showing a representative value of more than 300 individuals in all stations except Burtzeña (5), where more than 120 shells were found. Regarding the last study in 2009 there is an increase of individuals and an species decreased from 29 to 21.
Micropaleontological results: In the living association (histogram) have been taken a total of 4042 living foraminifera, belonging to 11 different species, and showing a representative value of more than 300 individuals in five different stations, three stations more then in 2009. The number of living individual per unit volume (80 cm3) at the surface of the sediment has increased compared with the previous sampling. The environmental conditions are becoming more favorable for growth and reproduction of foraminifera in the estuary.
Acknowledgements This work has been funded thanks to the projects 80IT365-10 (Basque Government, Harea-Grupo de Investigación en Geología Litoral), UFI11/09 (Universidad del País Vasco UPV/EHU, Unidad de Formación e Investigación en Cuaternario), and thanks to "La Caixa” Foundation.
(Aerial photo, 1957)
