Phytoplankton assemblages and characterization of a Dinophysis acuminata population during an upwelling–downwelling cycle

Abstract

The distributions of Dinophysis acuminata, its potential prey Myrionecta rubra, and the microplankton populations associated with them, were studied in Ría de Pontevedra (NW Spain) during a 2 wk cruise that covered an upwelling-downwelling cycle, and during intensive sampling over 21 h at the end of the cruise. Special attention was focused on the characterization and physiological condition of D. acuminata. There was vertical segregation between a phytoplankton assemblage that was dominated by upwelling-promoted diatoms and another assemblage that was dominated by small dinoflagellates located in the warmer surface layer (0 to 5 m) where D. acuminata was observed. High spatio-temporal variability was observed in the frequency of cells containing starch granules (indicating photosynthetic activity) and digestive vacuoles (indicating heterotrophic feeding); this pattern corresponded with the apparent availability of M. rubra cells. Populations of D. acuminata and M. rubra have their own niches and distinct responses to physical forcing, but both are located in common water masses and occasionally meet. Changes in vacuolation of D. acuminata were followed by a substantial increase (~35%) in cellular volume. D. acuminata did not exhibit daily migratory behaviour, and expressed a high division rate (0.51 d -1 ) under downwelling conditions. This work sheds new light on the relation between D. acuminata populations and its potential prey, and on its ecophysiology; it also questions previous assumptions about the environment that is suitable for its development. KEY WORDS: Harmful algal blooms · Plankton communities · Dinophysis acuminata · Myrionecta rubra · Predator-prey interactionsResale or republication not permitted without written consent of the publisher

Role of dissolved nitrate and phosphate in isolates of Mesodinium rubrum and toxin-producing Dinophysis acuminata

“…Together, these results suggest that prey availability influenced the total amount of OA, DTX1, and PTX2. This finding is in agreement with previous reports on other species of Dinophysis in the field and in culture (Kim et al , 2008; Riisgaard and Hansen, 2009; Campbell et al , 2010; Gonzalez-Gil et al , 2010; Minnhagen et al , 2011; Sjoqvist and Lindholm, 2011; Hattenrath-Lehmann et al , 2013), that reported maximum abundances of Dinophysis spp. occurring shortly after the peak and subsequent depletion of prey.…”

“…The vertical distribution of Dinophysis extends to as deep as 110 m (Fux et al , 2010) ranging from the surface to below the euphotic zone (Gisselson et al , 2002), suggesting that the genera are tolerant of high and low light conditions. Dinophysis growth is often associated with a stable water column (Maestrini, 1998; Seeyave et al , 2009; Reguera et al , 2012) and cells have often been shown to accumulate in thin layers or patches due to horizontal and vertical migration, transport driven by wind or currents (Mackenzie, 1991, 1992; Xie et al , 2007), or biological behavior to locate prey or avoid predators (Maestrini, 1998; Campbell et al , 2010; Gonzalez-Gil et al , 2010; Sjoqvist and Lindholm, 2011, Hattenrath-Lehmann et al , 2013). Populations have also been documented within systems containing a range of ambient dissolved nutrient levels: total dissolved nitrogen, 2 – 21 µM; silicate, 0 – 10 µM, and phosphate, 0 – 0.24 µM (Delmas et al , 1992; Maestrini, 1998).…”

Climate Variability and Oceanographic Settings Associated with Interannual Variability in the Initiation of Dinophysis acuminata Blooms

“…Culture experiments have also shown the relationship between an ample supply of prey and high division rates in Dinophysis [24,26]. In field populations, Dinophysis may be subject to prey limitation most of the time and peak densities are preceded by or co-occur with high densities of Mesodinium [18,27]. Furthermore, D. acuminata and Mesodinium rubrum were observed exhibiting similar diurnal vertical migrations in a 24-h study under stratified conditions in Ría de Vigo [28], and thin layers of the dinoflagellate and the ciliate co-occurred in time, but not always in space, in a coastal inlet in the northern Baltic Sea [29].…”

Harmful Dinophysis species: A review

“…would be often preylimited due to the scarcity of prey and would receive a large fraction of its carbon requirements from photosynthesis. Field observations confirm a high variability in the frequency of vacuolated cell-the unambiguous sign of recent phagotrophic feeding-in Dinophysis populations Gonzá -lez-Gil et al, 2010). Nevertheless, correlation of Dinophysis and M. rubrum abundances has to be interpreted with care, because patches of the respective populations may meet offshore, far from the sampling areas, and once the Dinophysis cells are satiated, they can undertake several divisions in the absence of Mesodinium.…”