Variación temporal del fitoplancton entre 1993 y 1998 en una estación fija del seno Aysén, Chile (45º26′S 73º00′W)Temporal change of the phytoplankton between 1993 and 1998 in a fixed station inside Aysén fjord, Chile (45º26′S 73º00′W)
The evolution of phytoplankton was studied between December 1980 and August 1985. A total of 1269 net and water samples were obtained in 11 cruises as part of the Estudio Regional del Fenómeno El Niño‐Chile Program covering the area extending from Arica (18°30′S) to Chañaral (26°20′S) from the coast to 200 n. mi (370 km) westward. In the period which preceded the 1982–1983 El Niño event, the coastal phytoplankton consisted predominantly of blooming diatom species which support a large phytoplanktonic biomass. The cell density up to 20 n. mi (37 km) off the coast was over 100 cells mL−1, with a maximum density nucleus near the coast, where values over 1000 cells mL−1 were found. With the anomalous conditions produced by El Niño in December 1982, changes were detected in the phytoplankton biomass and composition. There was a marked decrease in the biomass, the diatom dominance was restricted to a narrow coast band of 2 to 3 n. mi (3.7–5.5 km), and warm water species of diatoms and dinoflagellates reached the coast. These conditions reached their maximum intensity in May 1983. Phytoplankton started to return to normal conditions in December 1983 with a predominance of large diatoms, which support a biomass somewhat larger than that during El Niño. Small diatoms returned as the dominant species in large blooms in 1985. The cell numbers reached values similar to those during pre‐Niño conditions, with a normal neritic and oceanic phytoplankton distribution. Red tides caused by the ciliate Mesodinium rubrum were common during normal conditions before and after El Niño.
RESUMENLa familia Hemiaulaceae comprende cuatro géneros, señalados previamente para las aguas chilenas con las siguientes especies: Cerataulina pelagica (Cleve) Hendey, Hemiaulus sinensis Greville, H. membranaceus Cleve, Climacodium biconcavum Cleve, Eucampia antarctica (Castracane) Mangin, E. cornuta (Cleve) Grunow y E. zodiacus Ehrenberg. Sin embargo, el análisis con microscopía fotónica y electrónica de muestras recolectadas en aguas marinas chilenas que contenían representantes de esta familia (incluyendo la mayoría de aquellas estudiadas anteriormente por otros investigadores nacionales) reveló que (1) el género Cerataulina está representado por C. pelagica, distribuida a lo largo de la costa chilena entre Arica por el norte y el Estrecho de Magallanes por el sur, (2) el género Eucampia está representado por cuatro taxa: E. zodiacus f. cylindrocornis Syvertsen (señalada en trabajos anteriores como E. zodiacus f. zodiacus), E. zodiacus f. recta Rivera, Avaria & Cruces f. nov. (descrita aquí), E. cornuta y E. antarctica. Los primeros tres taxa se distribuyen en la zona central y norte de Chile, mientras que E. antarctica es propia de las aguas antárticas desde el Estrecho de Magallanes al sur, (3) las citas anteriores de Hemiaulus sinensis, H. membranaceus y Climacodium biconcavum para las aguas chilenas corresponden a determinaciones erróneas de Eucampia zodiacus f. recta, f. nov. Se entregan descripciones de los taxa encontrados y fotografías obtenidas con los microscopios fotónico y electrónicos que ilustran sus principales características morfológicas.
This note reports the finding of Thalassionema pseudonitzschioides (Schuette & Schrader) Hasle in samples collected in Iquique Bay (20º12'S, 70º10'W), in northern Chile. This is the first record of the species for the region. The taxon has been associated mainly with subtropical to temperate waters.
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