Se presenta la variación diaria de la abundancia de zooplancton en Bahía Magdalena, México a partir de muestreos en una estación fija durante 10 días en febrero de 2002. De 112 taxa identificados, los nauplios de balanos y los cladóceros Penilia avirostris y Pseudevadne tergestina fueron los más comunes y abundantes y con niveles de variación diaria de más del 100%. Los copépodos constituyeron una quinta parte de la abundancia del zooplancton y 7 de las 80 especies encontradas se registran por vez primera en la zona de estudio. La abundancia del zooplancton fue parcialmente coherente con la hidrografía de la bahía, así como con un modelo de retención de partículas. Las 3 especies de copépodos más abundantes fueron más numerosas a inicio de la serie pero tendieron a reducir su densidad hacia el fin del lapso de estudio. La hidrodinámica invernal en la zona se identificó como un factor de concentración de zooplancton, quizá de importancia mayor que la temperatura o la concentración de clorofila a, aún no estimada en la estructura de la comunidad ni en la intensidad de las relaciones interespecíficas.
Abstract.-A proliferation of the epizoic diatoms Falcula hyalina and Cylindrotheca closterium occurred, respectively, on the exoskeleton of marine copepods Acartia tonsa and Paracalanus sp. Samples were collected in February and in October 2013 in Bahía de La Paz. Both represent the first proliferations of this epizoic microalgae reported in the Gulf of California. Seawater temperature was 19°C in February and 28°C in October. A short morphological description, cell measurements and distribution of both species are provided.
Phytoplankton growth and microzooplankton grazing rates in situ, were studied in a fixed sampling station from October 2007 to August 2008, at the Ensenada de La Paz, Mexico, using the dilution method. The apparent growth rate of phytoplankton was higher in December (1.33 d-1) and lower in October (0.35 d-1). The grazing rate was highest in April (0.86 d-1) and minimum in February and August (0.38 d-1). Grazing pressure, measured as the percentage of potential production removed (% PPR) varied between 28 and 76%. The relationship between phytoplankton growth and grazing rate indicates that chlorophyll-a production is consumed by approximately 50%, involving other processes that cause mortality of phytoplankton, as sedimentation rate and mesozooplankton grazing. The finding of moderate grazing in autumn and a clear growth and consumption in the winter are features that require monitoring in larger temporal and spatial scales.
Zooplankton were studied from 16 oceanographic surveys carried out in Magdalena Bay, Baja California Sur, Mexico, between August 1997 and March 2001. Twenty-six taxonomic groups were identified, the most abundant and frequent of which were copepods and chaetognaths. In 2000-2001, the number of zooplankton groups tended to decrease by 10 to 20. Both zooplankton biomass and copepod abundance declined, unlike chaetognaths, which increased slightly. Fluctuations in zooplankton abundance were independent of the chlorophyll-a concentration, whereas the maximum zooplankton abundances were associated with changes in the sea surface temperature. The seasonal zooplankton abundance cycle in Magdalena Bay indicated that, in winter, the averaged was than 65,000 ind 100 m-3, a value that increased to more than 99,000 ind 100 m-3 in spring, remained around 100,000 ind 100 m-3 in summer, and decreased rapidly to nearly 40,000 ind 100 m-3 in autumn.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.