INDICADORES ECOLÓGICOS DE LA ESTRUCTURA DE LA COMUNIDAD FITOPLANCTÓNICA EN BAHÍA CONCEPCIÓN, GOLFO DE CALIFORNIA, MÉXICO

G. Verdugo-Díaz, A. Martínez-López, I. Gárate-Lizárraga

Abstract


Se presentan los cambios en la distribución espacial de la comunidad fitoplanctónica en Bahía Concepción, B.C.S. de 1991 a 1993. Se estimó la abundancia total, la variación espacio-temporal por fracciones de tamaño (nano y microfitoplancton) y se describe su estructura. Se determinaron 235 taxa, en donde las diatomeas fueron el grupo con mayor riqueza de especies (131). Los géneros más importantes fueron Chaetoceros, Rhizosolenia y Nitzschia. El segundo grupo en importancia fue el de los dinoflagelados (92 especies), representados principalmente por Protoperidinium, Ceratium y Prorocentrum; el tercer grupo fueron los silicoflagelados (9 especies), principalmente del genero Dictyocha. Las diatomeas dominaron en la temporada fría cuando la columna de agua se mantiene homogénea, en tanto que los dinoflagelados prosperaron durante la temporada cálida cuando la columna de agua estuvo estratificada. De este último grupo, 10 especies son tóxicas o potencialmente tóxicas. La abundancia fitoplanctónica total no mostró un comportamiento estacional definido, sin embargo, las variaciones interanuales mostraron un decremento de aproximadamente 25% durante 1992 y 1993, asociado con anomalías positivas de temperatura. A pesar de que las abundancias totales disminuyeron, la contribución porcentual de la fracción nanofitoplanctónica se mantuvo.

Ecological indicators of the phytoplankton community structure in Bahía Concepción, Gulf of California, Mexico

Seasonal changes in the spatial distribution of the phytoplankton community were determined in Bahía Concepción, B.C.S., from 1991 to 1993. The total abundance and the seasonal variations of phytoplankton size fractions (nanno and microphytoplankton) as well as its structure were determined. A total of 235 taxa were identified. Diatoms were the best represented group due to their high species richness (131). The most important genera were Chaetoceros, Rhizosolenia and Nitzschia. The second important group were dinoflagellates (92 species), represented mainly by Protoperidinium, Ceratium and Prorocentrum. The third numerically important group were the silicoflagellates (9 species). The most representative genus of this group was Dictyocha. A major presence of the diatoms was observed during the cold months with a homogeneous water-column. Major presence of dinoflagellates was recorded during the warm season when the water-column appeared stratified. Ten species of dinoflagellates were considered as toxic or potentially toxic. Total phytoplankton abundance did not show a clear seasonal pattern; nevertheless, the interannual variations exhibited an important decline of about 25 % during 1992 and 1993. These changes were related to positive anomalies of temperature. Altough phytoplankton abundance diminished, the percentage contribution of nannophytoplankton was
stable.

Keywords


Community; ecological indicators; microphytoplankton; nannophytoplankton; diatoms; water-column stratification

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CICIMAR Oceánides,  Av. Instituto Politécnico Nacional s/n Col. Playa Palo de Santa Rita, CP. 23096 La Paz, Baja California Sur, México. Teléfono (52)57296000 ext. 81527.   ISSN: 2448-9123,  otorgado por el Instituto Nacional del Derecho de Autor.