Microzooplankton grazing rate in Ensenada of La Paz, B.C.S., Mexico

Abstract

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.

Seasonal and diel influences on bottlenose dolphin acoustic detection determined by whistles in a coastal lagoon in the southwestern Gulf of California

“…Lower detections of bottlenose dolphins in August, when the temperature exceeds 28.7 C, might be a consequence of decreased prey availability ( Meekan et al, 2003 ; Drinkwater et al, 2010 ). This is the moment when nutrients in the lagoon may start to get depleted ( Esqueda-Escárcega et al, 2013 ) and the abundance of fish and marine mammals is known to decrease, too ( González-Acosta et al, 2005 ; Cubero-Pardo, 2007 ). Temperature was the only variable related to seasonal productivity patterns, because Chl was excluded due to collinearity ( Zuur, Ieno & Elphick, 2010 ; Dormann et al, 2013 ).…”