Mesozooplankton distribution, production and respiration in the global ocean.

Mesozooplankton biomass, abundance and mass-specific physiological rates as well as community production and respiration in the upper 2000 m were assessed from samples collected during the Malaspina circumnavigation expedition (~35ºN-40ºS) using an image-based analysis system (IBS). Equations relating metabolic rates, temperature, and body weight, were developed according to temperature ranges found at the different ocean regions and depth layers. High abundance and biomass were observed in the epipelagic zone and decreasing with depth as expected. However, high biomass was also found beyond 1000 m related to the colder and productive waters of the eastern regions of the Indian and Pacific Oceans. Specific growth and respiration rates followed a similar pattern and were highly correlated with temperature (r2=0.835 and 0.806 , respectively). Therefore, higher values were observed in the tropical and subtropical zones as the effect of higher temperature. Community production and respiration were considerably higher in the epipelagic layer, matching the distribution of biomass, with high values below 1000 m in the eastern Pacific/Indian Oceans. Global metabolism assessed through the IBS was similar to previous results based on data review.MALASPINA (CSD2008-00077

Vertical biogeographical overview of the Zooplankton community across the Atlantic, Pacific and Indian ocean (35ºN-40ºS)

From December 2010 to June 2011 the mesozooplankton has been sampled at the deep Atlantic, Indian and Pacific Ocean (*). From surface to 3000 m depth a HYDROBIOSS multinet was used distinguishing the epipelagic (77%), mesopelagic (11%) and bathypelagic zones (11%), where five layers were usually sampled (0-200, 200-500, 500-1000, 1000-2000 and 2000-3000 m depth). Among the three oceans, no large differences on abundance were found when taxonomic groups were considered, being always depth the most important factor affecting the vertical zooplankton distribution. The zooplankton abundance strongly decreased with depth and very low abundance was found at deeper waters. Very irregular spatial distribution was observed all across the three oceans, finding the lowest abundance in the south and western Pacific region. Copepods were always the most abundant contributors of the zooplankton community (84%) and more than 260 species identified. They were followed by chaetognaths (5%), siphonophores (3%), ostracods (2%) and euphausiids (1%). In a biogeographical overview, the vertical distribution of the most abundant copepods is analyzed, finding the largest copepods at deeper stratum, where small cosmopolitan copepods were also found

Vertical variability of trophic positions of zooplankton in the deep Ocean

Zooplankton plays a key role in oceanic ecosystems. However, the trophic ecology of organisms in deep layers of the ocean is poorly known. In this study we analyze the variability of trophic positions of zooplankton collected across three ocean basins in the epi-, meso and bathypelagic domains. Stable carbon and nitrogen isotopes were used as indicators of the sources of nutrients and positions within the food web. The enrichment in heavy nitrogen isotopes with depth and the correlation between surface and deep samples revealed that deep zooplankton was supported by local epipelagic production, subsequently processed through the water column. In addition the nitrogen isotope enrichment of carnivores vs. omnivores was consistent across ocean biomes and water layers, suggesting a similar trophic structure of the pelagic food web in the deep ocean despite variations in the nitrogen sources. Siphonofora, Chaetognata and Myctophida were the top predators while Calanoid Copepoda and Mysidacea displayed the lowest trophic positions. In contrast, carbon isotopes did not show significant variations with depth or trophic groups implying low influence of coastal production in deep ocean food webs

Vertical biogeographical overview of zooplankton: preliminary results of the Malaspina expedition 2010-2011

octobre 19631963/10 (N468)

Abundance and diversity of zooplankton along the subtropical and tropical global oceans.

The abundance and composition of zooplankton down to 3000 m depth was studied in the subtropical and tropical latitudes across the Atlantic, Pacific and Indian Oceans (35 °N–40 °S). Samples were collected from December 2010 to June 2011 during the Malaspina Circumnavigation Expedition. Usually, low abundances were observed with the highest values found in the North Pacific Ocean, Benguela, and off Mauritania, and the lowest in the South Pacific Ocean. No significant differences in abundance and zooplankton composition were found among oceans, with depth being consistently the most important factor affecting their distribution. Each depth strata were inhabited by distinct copepod assemblages, which significantly differed among the strata. The contribution of copepods to the zooplankton community increased with the depth although, as expected, their abundance strongly decreased. Among the copepods, 265 species were identified but 85% were rare and contributed less than 1% in abundance. Clausocalanus furcatus and Nannocalanus minor dominated the epipelagic strata. Pleuromamma abdominalis and Lucicutia clausi were of importance in the mesopelagic layer, and Pareucalanus, Triconia, Conaea and Metridia brevicauda in the bathypelagic layer. Our results provide a global-scale assessment of copepod biodiversity and distribution, providing a contemporary benchmark to follow future ocean changes at low latitudes

Bathypelagic fauna as a main driver of carbon sequestration in the ocean

Sequestration, in contrast to export, is a mechanism of the biological pump occurring when carbon cannot return to the atmosphere in at least 100 years, normally the carbon transported below 1000 m depth. Pelagic fauna release carbon at depth through respiration, egestion, excretion, moulting, lipid consumption and mortality supporting deep-sea food webs. Knowledge about this transport in the mesopelagic layer is growing. However, the role of the pelagic fauna to fuel the bathypelagic zone, the layer where effective carbon sequestration occurs, is largely unknown. Here we report net zooplankton biomass in the meso- and bathypelagic zones showing significant relationships with primary production (PP) at a global scale during the Malaspina Circumnavigation Expedition. We also reviewed available data on zooplankton biomass at the different biogeographical provinces also showing significant correlations with large-scale estimates of PP, implying the transference of a significant fraction of PP from the epipelagic to the deep ocean. Carbon sequestration assessed only from conservative estimates of zooplankton mortality in the bathypelagic was 0.43 PgC y-1, in the order of recent estimates of gravitational carbon sequestration. These values and those recently reviewed due to lipid consumption almost triples ocean carbon sequestration estimates in Westerlies and Polar biomes. These results point at a pivotal role of the pelagic fauna in ocean carbon sequestration as, besides zooplankton, downward transport by macroplankton and micronekton should also be accounted for. Our results raises the question of whether we are severely underestimating carbon sequestration in the ocea

Large-scale ocean connectivity and planktonic body size

Global patterns of planktonic diversity are mainly determined by the dispersal of propagules with ocean currents. However, the role that abundance and body size play in determining spatial patterns of diversity remains unclear. Here we analyse spatial community structure - β-diversity - for several planktonic and nektonic organisms from prokaryotes to small mesopelagic fishes collected during the Malaspina 2010 Expedition. β-diversity was compared to surface ocean transit times derived from a global circulation model, revealing a significant negative relationship that is stronger than environmental differences. Estimated dispersal scales for different groups show a negative correlation with body size, where less abundant large-bodied communities have significantly shorter dispersal scales and larger species spatial turnover rates than more abundant small-bodied plankton. Our results confirm that the dispersal scale of planktonic and micro-nektonic organisms is determined by local abundance, which scales with body size, ultimately setting global spatial patterns of diversit