Here we review all published data on phytoplankton growth and microzooplankton grazing using the dilution technique to better understand the role of this group of grazers in different regions of the oceans, and to identify the knowledge gaps that require future efforts. A total of 1525 data points assimilated from 110 studies were included and grouped using the biogeographic subsets defined by Longhurst et al. [(1995) An estimate of global primary production in the ocean from satellite radiometer data. J. Plankton Res., 17, 1245-1271]. Total median phytoplankton growth rates in each of the subsets varied between 0.15 (Polar Southern) and 0.83 day 21 (Trades Atlantic), with the corresponding microzooplankton grazing rates ranging between 0.07 (Polar Southern) and 0.48 day 21 (Trades Indian). The median percentage of primary production (PP) grazed by microzooplankton was relatively constant among the regions and ranged from 49

The plankton outburst during the so-called late winter bloom in subtropical waters was studied in relation to lunar illumination in the Canary Island waters. Nutrient enrichment by mixing and dust deposition promoted a bloom of phyto-and zooplankton. Mesozooplankton biomass increased as the winter mixing progressed but peaked in every full moon and decreased thereafter because of the effect of predation by interzonal diel vertical migrants (DVMs). The pattern was similar to the one described in lakes due to predation by fishes and confirms that this phenomenon is important in the sea. The estimated consumption and subsequent transport of epipelagic zooplankton biomass by DVMs after every full moon is on the order of the mean gravitational export and is an unaccounted flux of carbon to the mesopelagic zone that may play a pivotal role in the efficiency of the biological pump.Most of the research about the downward flux of carbon in the ocean has centered on the so-called gravitational flux, the transport due to the sedimentation of the particulate organic carbon production from the euphotic layer to the mesopelagic zone. In tropical and subtropical regions this flux is a low number, normally less than 10% of primary production (Karl et al. 1996). Another component of the biological pump is the so-called active flux due to the transport of carbon by vertical migrants. These organisms feed on the shallower layers of the ocean at night and return to their daytime residence at depth where they metabolize carbon or simply are eaten by other organisms. The role of these rather large organisms (mesozooplankton and micronekton) in the ocean carbon sequestration has been almost neglected. Active flux is a rather complex mechanism that involves the gut flux (Angel 1989) (the transport due to the release of feces below the mixed layer), carbon dioxide respiration (Longhurst et al. 1990), dissolved organic carbon excretion (Steinberg et al. 2000), and mortality (Zhang and Dam 1997) at depth. The few values available at present mainly based on respiration at depth indicate that the active downward carbon flux is highly variable, ranging from 4% to 70% of the gravitational flux (Herná ndez-Leó n and Ikeda 2005a). However, diel vertical migrants (DVMs) account for the control of 5-10% of the daily epipelagic zooplankton production (Hopkins et al. 1996), and this ingested food is efficiently transported downward (Pearre 2003). The consumption of epipelagic zooplankton by these organisms and their role in the fate of a bloom are at present poorly known.A way to study the biological pump in subtropical waters is to understand the development of the bloom during winter, when nutrients are present in the euphotic zone. The late winter bloom in subtropical waters is produced by cooling of the shallower layers of the ocean, eroding the thermocline and allowing a small flux of nutrients to the euphotic zone. This process promotes the increase in primary production and the growth of micro-and mesozooplankton. Atmospheric Saharan...

We studied the plankton dynamics of two semi-enclosed marine coastal inlets of the north of Jurong Island separated by a causeway (SW Singapore; May 2012-April 2013). The west side of the causeway (west station) has residence times of ca. one year and is markedly eutrophic. The east side (east station) has residence times of one month and presents lower nutrient concentrations throughout the year. The higher nutrient concentrations at the west station did not translate into significantly higher concentrations of chlorophyll a, with the exception of some peaks at the end of the South West Monsoon. Microzooplankton were more abundant at the west station. The west station exhibited more variable abundances of copepods during the year than did the east station, which showed a more stable pattern and higher diversity. Despite the higher nutrient concentrations at the west station (never limiting phytoplankton growth), the instantaneous phytoplankton growth rates there were generally lower than at the east station. The phytoplankton communities at the west station were top-down controlled, largely by microzooplankton grazing, whereas those of the east station alternated between top-down and bottom-up control, with mesozooplankton being the major grazers. Overall, the trophic transfer efficiency from nutrients to mesozooplankton in the eutrophic west station was less efficient than in the east station, but this was mostly because a poor use of inorganic nutrients by phytoplankton rather than an inefficient trophic transfer of carbon. Some hypotheses explaining this result are discussed.

Resting strategies of planktonic organisms are important for the ecological processes of coastal waters and their impacts should be taken into consideration in management of water bodies used by multiple industries. We combined different approaches to evaluate the importance of resting stages in Singapore coastal waters. We used molecular approaches to improve the knowledge on Singapore biodiversity, we sampled and extracted cysts from sediments to evaluate the density of resting stages in Johor Strait, and we compared systematically information on Singapore planktonic biodiversity to existing published information on resting stages from these reported organisms. This is the first study evaluating the importance of resting stages in Singapore waters. Above 120 species reported in Singapore are known to produce resting stages though no previous work has ever been done to evaluate the importance of these strategies in these waters. The results from the resting stage survey confirmed 0.66 to 5.34 cyst g dry weight sediment were present in the Johor Strait suggesting that cysts may be flushed by tidal currents into and out of the strait regularly. This also suggest that the blooms occurring in Singapore are likely due to secondary growth of Harmful Algae Bloom species in the water rather than from direct germination of cysts from sediment. Finally, we discuss the importance of these resting eggs for three main national industries in Singapore (shipping, marine aquaculture and provision of drinking water through seawater desalination). We argue that this study will serve as a baseline for some of the future management of Singapore waters.

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