Aitor Laza - Academia.edu (original) (raw)
Papers by Aitor Laza
Journal of Sea Research, 2009
This contribution focuses upon the use of phytoplankton as an indicator of ecological quality in ... more This contribution focuses upon the use of phytoplankton as an indicator of ecological quality in the coastal waters of the Basque Country (Bay of Biscay, northern Spain). The Water Framework Directive (WFD) establishes a common water policy in the European Union. The phytoplankton, owing to its relationship with the eutrophication processes, is one of the biological elements considered within the WFD. Phytoplankton biomass, composition and abundance, together with frequency and intensity of blooms, are the metrics to be assessed according to the WFD. In this work, data on phytoplankton biomass and frequency and intensity of blooms along the Basque coast were analysed. Phytoplankton biomass was evaluated using the 90th percentile of the chlorophyll-a concentrations (Chl-a) over a 6-year period (2001–2006). For the evaluation of the frequency of blooms, data on composition and abundance of the phytoplankton communities were obtained, then analysed using three different approaches. The first approach involved the utilisation of only some of the taxonomic groups (diatoms and dinoflagellates). The second approach divided the phytoplankton community into two size categories (> 20 µm and 2–20 µm, cell diameter). The third approach used all of the phytoplankton taxa recorded in the sample. Evidence for the oligotrophy of the coastal waters of the Basque Country was provided by the low values obtained for the 90th percentile of the Chl-a (< 3 µg L− 1). Low intensity of upwelling activity, relatively small river loads and a narrow shelf characterise this coast, which can explain the low level of phytoplankton biomass. However, phytoplankton counts were relatively high compared with other neighbouring coastal waters a priori of higher trophic richness. These differences are discussed in relation to the methodologies for the analysis of cell counts which different monitoring programmes utilise in the European Union.
Estuarine Coastal and Shelf Science, 2006
In the context of a monitoring program developed in the Nervion River estuary, the structure of t... more In the context of a monitoring program developed in the Nervion River estuary, the structure of the phytoplankton community was assessed by means of microscopy and high-performance liquid chromatography (HPLC) analysis of pigments. Four size fractions were considered: <3 μm (picoplankton), 3–8 μm (small nanoplankton), 8–20 μm (large nanoplankton) and >20 μm (microplankton). Samples were taken in spring and summer at three sites located in the marine extreme of the estuary. Fucoxanthin, chlorophyll b and alloxanthin were the most abundant signature pigments. Fucoxanthin alone explained more than 95% of the total chlorophyll a variance. Most of the chlorophyll a and the major signature pigments were included in the nano- and microplankton size fractions, denoting the high trophic status of the water. The picoplankton, dominated by chlorophyll b containing algae or eustigmatophytes, accounted always for less than 5% of the total chlorophyll a. The fucoxanthin/chl a ratio of natural communities was highest in the microplankton and large nanoplankton whereas that of alloxanthin/chl a was generally highest in the small nanoplankton and that of chl b/chl a reached the highest values in the picoplankton.
Hydrobiologia, 2005
In the Nervion River estuary surface samples were taken from March to September 2003 at six sites... more In the Nervion River estuary surface samples were taken from March to September 2003 at six sites covering most of the salinity range with the aim to know the biomass and taxonomic composition of phytoplankton assemblages in the different segments. Nine groups of algae including cyanobacteria, diatoms, dinoflagellates, chlorophytes, prasinophytes, euglenophytes, chrysophytes, haptophytes, raphidophytes and cryptophytes were identified by means of a combination of pigment analysis by high-performance liquid chromatography (HPLC) and microscopic observations of live and preserved cells. Diatoms, chlorophytes and cryptophytes were the most abundant algae in terms of cells number, whereas fucoxanthin, peridinin, chlorophyll b (Chl b) and alloxanthin were the most abundant auxiliary pigments. Based on multiple regression analysis, in the outer estuary (stations 0, 1, 2 and 3) about 93% of the chlorophyll a (Chl a) could be explained by algae containing fucoxanthin and by algae containing Chl b, whereas in the rest of the estuary most of the Chl a (about 98%) was accounted for by fucoxanthin, Chl b and alloxanthin containing algae. The study period coincided with that of most active phytoplankton growth in the estuary and fucoxanthin was by far the dominant among those signature pigments. Several diatoms, chrysophytes, haptophytes and raphydophytes were responsible for fucoxanthin among identified species. Besides, dinoflagellates with a pigment pattern corresponding to chrysophytes and type 4 haptophytes were identified among fucoxanthin-bearing algae. Cryptophytes were the most abundant species among those containing alloxanthin. The maximum of Chl b registered at the seaward end in April coincided with a bloom of the prasinophytes Cymbomonas tetramitiformis, whereas the Chl b maxima in late spring and summer were accounted for by prasinophytes in the middle and outer estuary and by several species of chlorophytes in the middle and inner estuary. Other Chl b containing algae were euglenophytes and the dinoflagellate Peridinium chlorophorum. Dinoflagellates constituted generally a minor component of the phytoplankton.
Journal of Sea Research, 2009
This contribution focuses upon the use of phytoplankton as an indicator of ecological quality in ... more This contribution focuses upon the use of phytoplankton as an indicator of ecological quality in the coastal waters of the Basque Country (Bay of Biscay, northern Spain). The Water Framework Directive (WFD) establishes a common water policy in the European Union. The phytoplankton, owing to its relationship with the eutrophication processes, is one of the biological elements considered within the WFD. Phytoplankton biomass, composition and abundance, together with frequency and intensity of blooms, are the metrics to be assessed according to the WFD. In this work, data on phytoplankton biomass and frequency and intensity of blooms along the Basque coast were analysed. Phytoplankton biomass was evaluated using the 90th percentile of the chlorophyll-a concentrations (Chl-a) over a 6-year period (2001–2006). For the evaluation of the frequency of blooms, data on composition and abundance of the phytoplankton communities were obtained, then analysed using three different approaches. The first approach involved the utilisation of only some of the taxonomic groups (diatoms and dinoflagellates). The second approach divided the phytoplankton community into two size categories (> 20 µm and 2–20 µm, cell diameter). The third approach used all of the phytoplankton taxa recorded in the sample. Evidence for the oligotrophy of the coastal waters of the Basque Country was provided by the low values obtained for the 90th percentile of the Chl-a (< 3 µg L− 1). Low intensity of upwelling activity, relatively small river loads and a narrow shelf characterise this coast, which can explain the low level of phytoplankton biomass. However, phytoplankton counts were relatively high compared with other neighbouring coastal waters a priori of higher trophic richness. These differences are discussed in relation to the methodologies for the analysis of cell counts which different monitoring programmes utilise in the European Union.
Estuarine Coastal and Shelf Science, 2006
In the context of a monitoring program developed in the Nervion River estuary, the structure of t... more In the context of a monitoring program developed in the Nervion River estuary, the structure of the phytoplankton community was assessed by means of microscopy and high-performance liquid chromatography (HPLC) analysis of pigments. Four size fractions were considered: <3 μm (picoplankton), 3–8 μm (small nanoplankton), 8–20 μm (large nanoplankton) and >20 μm (microplankton). Samples were taken in spring and summer at three sites located in the marine extreme of the estuary. Fucoxanthin, chlorophyll b and alloxanthin were the most abundant signature pigments. Fucoxanthin alone explained more than 95% of the total chlorophyll a variance. Most of the chlorophyll a and the major signature pigments were included in the nano- and microplankton size fractions, denoting the high trophic status of the water. The picoplankton, dominated by chlorophyll b containing algae or eustigmatophytes, accounted always for less than 5% of the total chlorophyll a. The fucoxanthin/chl a ratio of natural communities was highest in the microplankton and large nanoplankton whereas that of alloxanthin/chl a was generally highest in the small nanoplankton and that of chl b/chl a reached the highest values in the picoplankton.
Hydrobiologia, 2005
In the Nervion River estuary surface samples were taken from March to September 2003 at six sites... more In the Nervion River estuary surface samples were taken from March to September 2003 at six sites covering most of the salinity range with the aim to know the biomass and taxonomic composition of phytoplankton assemblages in the different segments. Nine groups of algae including cyanobacteria, diatoms, dinoflagellates, chlorophytes, prasinophytes, euglenophytes, chrysophytes, haptophytes, raphidophytes and cryptophytes were identified by means of a combination of pigment analysis by high-performance liquid chromatography (HPLC) and microscopic observations of live and preserved cells. Diatoms, chlorophytes and cryptophytes were the most abundant algae in terms of cells number, whereas fucoxanthin, peridinin, chlorophyll b (Chl b) and alloxanthin were the most abundant auxiliary pigments. Based on multiple regression analysis, in the outer estuary (stations 0, 1, 2 and 3) about 93% of the chlorophyll a (Chl a) could be explained by algae containing fucoxanthin and by algae containing Chl b, whereas in the rest of the estuary most of the Chl a (about 98%) was accounted for by fucoxanthin, Chl b and alloxanthin containing algae. The study period coincided with that of most active phytoplankton growth in the estuary and fucoxanthin was by far the dominant among those signature pigments. Several diatoms, chrysophytes, haptophytes and raphydophytes were responsible for fucoxanthin among identified species. Besides, dinoflagellates with a pigment pattern corresponding to chrysophytes and type 4 haptophytes were identified among fucoxanthin-bearing algae. Cryptophytes were the most abundant species among those containing alloxanthin. The maximum of Chl b registered at the seaward end in April coincided with a bloom of the prasinophytes Cymbomonas tetramitiformis, whereas the Chl b maxima in late spring and summer were accounted for by prasinophytes in the middle and outer estuary and by several species of chlorophytes in the middle and inner estuary. Other Chl b containing algae were euglenophytes and the dinoflagellate Peridinium chlorophorum. Dinoflagellates constituted generally a minor component of the phytoplankton.