Plankton trophic structure and particulate organic carbon production during a coastal downwelling-upwelling cycle

Abstract

) indicated the establishment of a herbivorous food web structure. Particulate organic carbon (POC) production was mainly due to phytoplankton (98%) and did not differ between periods. However, the observed variability in plankton trophic interactions should affect the magnitude of POC export from this dynamic system. KEY WORDS: Food webs · Carbon fluxes · Bacterioplankton · Phytoplankton · Zooplankton · Cabo Frio · South Brazil Bight Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 363: [109][110][111][112][113][114][115][116][117][118][119] 2008 small phytoplankton and bacteria to larger zooplankton and then higher pelagic trophic levels is mediated by heterotrophic nano-and micro-sized protists (Sherr et al. 1986). Therefore, in these microbial food webs, most of the biogenic carbon produced is recycled within the system through heterotrophic respiration (Legendre & Le Fevre 1995).In contrast, in more eutrophic systems with low vertical stability, larger phytoplankton cells are more representative and usually dominant, where turbulence simultaneously provides nutrient and prevents sinking below the euphotic zone (Kiørboe 1993). In those conditions an herbivorous food web prevails and most of the POC produced is exported via grazing, as the mesozooplankton are the dominant primary consumers (Legendre & Rassoulzadegan 1996). Moreover, carbon export is directly related to the input and uptake of 'new' nutrients, mainly nitrate (N-NO 3 ) to the euphotic zone (Dugdale & Goering 1967), and this nitrogen form is primarily utilized by larger cells, such as diatoms (Price et al. 1985).Coastal waters influenced by upwelling are among the most productive aquatic systems. The periodical wind-driven transport of surface waters offshore and the consequent upwelling of deeper water masses provide enrichment to previously oligotrophic waters. The high nutrient input to the surface waters, especially N-NO 3 , stimulates phytoplankton production, mainly for larger species, resulting in higher mesozooplankton and fisheries productivity. This pattern has been described for several upwelling zones around the world, such as those in the SE Pacific Ocean , Iriarte & Gonzalez 2004, Fernandez-Alamo & Farber-Lorda 2006, NE Pacific Ocean (Peterson et al. 1979, Collins et al. 2003, NE Atlantic Ocean (Bode et al. 2003), and Indian Ocean (Brown et al. 2002).Upwelling zones usually occur along eastern ocean boundaries, between 30°N and 30°S, due to the dominance of the trade winds. In the SW Atlantic, however, the change in the coastal direction at 23°S (Cabo Frio, SE Brazil) from N-S to E-W, along with the proximity of the 100 m isobath to the coast, allow the NE winds to move surface waters offshore and the consequent upwelling of the South Atlantic Central Water (SACW). This results in a high productivity core in the midst of the otherwise oligotrophic Brazilian Current waters (Valentin 1984a). The upwelling of deeper water masses is reversed when shifts in wind direction bring surface w...

Plankton and particle biomass size spectra on the Southwest Atlantic: Case studies in tropical and subtropical areas

“…The strong association between SACW and mesozooplankton biomass confirm the importance of these intrusions to enhance local productivity (Metzler et al 1997, Saldanha-Corrêa andGianesella 2004), especially of herbivorous mesozooplankton (Guenther et al 2008), since we found typically herbivorous groups associated to intrusions (e.g. calanoids, including Temora spp.…”

“…In a stratified water column with warmer surface temperature scenario, the surface water can be rapidly nutrient-depleted and the phytoplankton community is likely to be dominated by picoplankton and flagellates (Margalef 1997). On the other hand, under the SACW upwelling further north in Cabo Frio, when nutrients are injected in pulses, the phytoplankton community is largely dominated by diatoms (Guenther et al 2008). Therefore, although SACW bottom intrusions inject nutrients in the system, as in an upwelling event, this water mass rarely reaches the surface on the inner shelf off Ubatuba.…”

“…Previous studies have provided descriptions of the composition, abundance, and biomass distribution of both phyto-and zooplankton (Valentin andMonteiro-Ribas 1993, Brandini et al, 1997;Ekau, 1999;Knoppers et al, 1999;Susini-Ribeiro, 1999), as well as on phytoplankton production (Gaeta et al, 1999), but no information on plankton size structure is available. In fact, plankton communities are often neglected in coral reef studies worldwide, although they represent a significant food source for reef-building corals (Porter, 1976;Ferrier-Pagès et al, 2003) and associated biota, especially reef fish (Russell, 1983).…”

Infection by Amoebophrya spp. parasitoids of dinoflagellates in a tropical marine coastal area

“…During such periods, oligotrophic waters dominate in the Cabo Frio area and the plankton community experiences extensive nutrient limitation (Valentin 1984). The system is then characterized by a microbial food web structure, whereby carbon produced by bacteria and small phytoplankton cells is channeled via flagellates and ciliates up to the mesozooplankton and higher trophic levels (Guenther et al 2008). Occasional development of large dinoflagellate cells -like Ceratium falcatiforme -during these periods might restrict carbon flow up the food web.…”

Genetic Optimization of Artificial Neural Networks to Forecast Virioplankton Abundance from Cytometric Data

“…The inverse pattern comes with the S-SW winds when cold fronts bring the oligotrophic TW back to the coast [49]. According [50] these processes have a direct impact on the quantity and composition of the plankton communities, shifting the trophic structure.…”