Frederico Pereira Brandini

Pico and nanoplankton abundance and carbon stocks along the Brazilian Bight

Pico and nanoplankton communities from the Southwest Atlantic Ocean along the Brazilian Bight are poorly described. The hydrography in this region is dominated by a complex system of layered water masses, which includes the warm and oligotrophic Tropical Water (TW), the cold and nutrient rich South Atlantic Central Water (SACW) and the Coastal Water (CW), which have highly variable properties. In order to assess how pico- and nanoplankton communities are distributed in these different water masses, we determined by flow cytometry the abundance of heterotrophic bacteria, Prochlorococcus, Synechococcus and autotrophic pico and nanoeukaryotes along three transects, extending from 23°S to 31°S and 39°W to 49°W. Heterotrophic bacteria (including archaea, maximum of 1.5 × 106 cells mL−1) were most abundant in Coastal and Tropical Water whereas Prochlorococcus was most abundant in open-ocean oligotrophic waters (maximum of 300 × 103 cells mL−1). Synechococcus(up to 81 × 103 cells mL−1), as well as autotrophic pico and nanoeukaryotes seemed to benefit from the influx of nutrient-rich waters near the continental slope. Autotrophic pico and nanoeukaryotes were also abundant in deep chlorophyll maximum (DCM) layers from offshore waters, and their highest abundances were 20 × 103 cells mL−1 and 5 × 103 cells mL−1, respectively. These data are consistent with previous observations in other marine areas where Synechococcus and autotrophic eukaryotes dominate mesotrophic waters, whereas Prochlorococcus dominate in more oligotrophic areas. Regardless of the microbial community structure near the surface, the carbon stock dominance by autotrophic picoeukaryotes near the DCM is possibly linked to vertical mixing of oligotrophic surface waters with the nutrient-rich SACW and their tolerance to lower light levels.

Epilithic community development on artificial reefs deployed along a cross-shelf environmental gradient off Paraná state, southern Brazil

Concrete modules were deployed on the bottom of the 11, 18 and 30 meters isobaths along a cross-shelf hydrographic gradient off Parana State, Southern Brazil, with the purpose of studying the colonization of sessile epilithic macroinvertebrates on artificial surfaces. After one year of submersion a total of 63 species of epilithic organisms were identified, dominated by Ostrea puelchana, Chthamalus bisinuatus, Balanus cf spongicola, Astrangia cf rathbuni, Didemnum spp, poryphers and bryozoans. Diversity index and percent cover at reef stations placed at 11, 18 and 30 meters isobaths were respectively 2.28 and 66.7%, 2.79 and 96.6% and 1.66 and 77.4%. Differences of general community structure among the three assemblages were not clearly related to the general environmental conditions at the bottom layers near the reef stations. Turbidity and larval abundance are discussed as important factors affecting colonization processes. Results indicate that depths between 15-20 meters are more suitable for the implementation of large scale artificial reef systems in the inner shelf off Parana and, possibly, throughout the inner shelves off southern Brazil with similar hydrographic conditions.

Diel Vertical Dynamics of Gelatinous Zooplankton (Cnidaria, Ctenophora and Thaliacea) in a Subtropical Stratified Ecosystem (South Brazilian Bight).

The diel vertical dynamics of gelatinous zooplankton in physically stratified conditions over the 100-m isobath (~110 km offshore) in the South Brazilian Bight (26°45’S; 47°33’W) and the relationship to hydrography and food availability were analyzed by sampling every six hours over two consecutive days. Zooplankton samples were taken in three depth strata, following the vertical structure of the water column, with cold waters between 17 and 13.1°C, influenced by the South Atlantic Central Water (SACW) in the lower layer (>70 m); warm (>20°C) Tropical Water in the upper 40 m; and an intermediate thermocline with a deep chlorophyll-a maximum layer (0.3–0.6 mg m-3). Two distinct general patterns were observed, emphasizing the role of (i) physical and (ii) biological processes: (i) a strong influence of the vertical stratification, with most zooplankton absent or little abundant in the lower layer. The influence of the cold SACW on the bottom layer apparently restricted the vertical occupation of most species, which typically inhabit epipelagic warm waters. Even among migratory species, only a few (Aglaura hemistoma, Abylopsis tetragona eudoxids, Beroe sp., Thalia democratica, Salpa fusiformis) crossed the thermocline and reached the bottom layer. (ii) A general tendency of partial migrations, with variable intensity depending on the different species and developmental stages; populations tended to be more widely distributed through the water column during daylight, and to become more aggregated in the upper layer during the night, which can be explained based on the idea of the “hunger-satiation hypothesis”, maximizing feeding and minimizing the chances of being predated.

Comparison of zooplankton community structure between impacted and non-impacted areas of Paranaguá Bay Estuarine Complex, south Brazil

We analysed the seasonal distribution of the zooplankton community in an anthropogenically impacted area (Paranaguá Bay) and a non-impacted area (Laranjeiras Bay) of the Paranaguá Bay Estuarine Complex. Large phytoplankton (> 50 μm) and zooplankton were collected every two months, between August 2003 and June 2004. The phytoplankton community was numerically dominated by diatoms (78%) and dinoflagellates (19%). Zooplankton abundance varied between 670 and 100,716 individuals m–3, with a dominance of copepods, mainly the calanoids Acartia lilljeborgii, Acartia tonsa and Pseudodiaptomus acutus. A clear seasonal pattern was observed: copepods were significantly more abundant during the rainy than in the dry season. Significant differences in abundance between the two bays were detected only for cirripede larvae, which were more abundant in Paranaguá Bay. This lack of difference between the two areas was probably a consequence of the water circulation along the estuary, which may have diluted and dispersed the pollutants from Paranaguá Bay to other areas of the estuary.

First record of the hydromedusa Aequorea macrodactyla (Leptothecata: Aequoreidae) in Brazilian waters

Three Aequorea macrodactyla (Brandt 1835) medusae were found along the São Paulo and Rio de Janeiro coasts. The specimens clearly match the diagnosis of the species, as they have tentacular bulbs with a large abaxial keel and a prominent excretory pore and papilla. The number of tentacles is approximately three times smaller than the number of radial canals. In the southwestern Atlantic, this species was previously known from Patagonian waters and this is the first record from the non-temperate southwestern Atlantic. Additionally, a thorough review of meristic data is provided for this hydrozoan species.

The Partitioning of Carbon Biomass among the Pico- and Nano-plankton Community in the South Brazilian Bight during a Strong Summer Intrusion of South Atlantic Central Water

To investigate how pico- and nanoplankton respond to oceanographic conditions in the Southwestern Atlantic Ocean, we assessed the influence of a summer intrusion of the South Atlantic Central Water (SACW) on the spatial and vertical dynamics of planktonic abundance and carbon biomass across environmental gradients. Seawater samples were collected from six depths within the euphotic zone at nine oceanographic stations in a transect on the Brazilian continental shelf in January 2013. The abundance of pico- and nanoplankton populations was determined by flow cytometry, and carbon biomass was calculated based on conversion factors from the literature. The autotrophic Synechococcus spp., picoeukaryotes and nanoeukaryotes were more abundant in the surface layers of the innermost stations influenced by Coastal Water (maximum of 1.19x105, 1.5x104, and 8.61x103 cell·mL−1, respectively), whereas Prochlorococcus spp. dominated (max. of 6.57x104 cell·mL−1) at the outermost stations influenced by Tropical Water and in the uplifting layers of the SACW around a depth of 100 m. Numerically, heterotrophic bacterial populations were predominant, with maximum concentrations (2.11x106 cell·mL−1) recorded in the surface layers of the inner and mid shelves in Coastal Water and the upper limits of the SACW. Nutrient-rich (high silicate and phosphate) and relatively less saline waters enhanced the picoeukaryotic biomass, while Synechococcus and heterotrophic bacteria were linked to higher temperatures, lower salinities, and higher inputs of ammonia and dissolved organic carbon. The relative importance of each group to carbon biomass partitioning under upwelling conditions is led by heterotrophic bacteria, followed by picoeukaryotes, Synechococcus and Prochlorococcus, and when the SACW is not as influential, the relative contribution of each phytoplanktonic group is more evenly distributed. In addition to habitat preferences, the physical structure of oligotrophic waters has a large impact on the vertical and spatial distribution patterns of picoplankton, reflecting the strong effect of the SACW intrusion.

Community Structure and Spatiotemporal Dynamics of the Zooplankton in the South Brazilian Bight: A Review

The South Brazilian Bight (23–28.5°S; SBB) is a typical western boundary current system with a wide shelf and which has high ecologic and economic importance, supporting nationally important fishing grounds. Away from the coastal areas, the planktonic production is mostly controlled by regenerative processes prevailing in the oligotrophic Tropical Water (TW) of the Brazil Current, enriched by the advection of the nutrient-rich South Atlantic Central Water (SACW). About 790 zooplanktonic invertebrate species have been recorded, what is an underestimate considering that most meroplanktonic and some holoplanktonic taxa are largely unstudied. An inshore-offshore gradient is clear. Zooplankton abundance and biomass are typically higher in more coastal areas, diminishing offshore as the influence of the oligotrophic TW increases, while the diversity has the inverse tendency. The cold and nutrient-rich SACW intrusions certainly are the most relevant mesoscale physical feature over the shelf of the SBB, increasing considerably the primary production and subsequently zooplankton abundance and production. Indeed, available data suggest that the intrusions of the SACW and their strength are an important factor influencing both seasonal and interannual variability in zooplankton diversity, biomass, abundance, production, and size-spectra. While the distributional patterns of most of the dominant groups in relation to the main water masses are relatively well-known, little is known about the life strategy, trophic interactions, physiological responses, and the impact of the main physical processes on these populations. In this review, we also emphasize the need for process-oriented studies along SBB with spatiotemporal scales relevant to the main physical events in order to better understand the zooplankton dynamics and their role in the regional fishery production.

Influence of oceanic fronts on mesozooplankton abundance and grazing during spring in the south-western Atlantic

We investigated the influence of oceanic fronts on mesozooplankton distribution and grazing activity in the south-west Atlantic. Sampling was conducted during late spring 1993 along a north–south transect between subtropical waters off Brazil and Antarctic waters. Mesozooplankton abundance and biomass were ~10-fold higher in the Subtropical Confluence Zone (SCZ) and in the Antarctic Polar Front (APF) relative to subtropical and subantarctic waters beyond the influence of those frontal systems. Mesozooplankton was dominated by calanoid and cyclopoid copepods. Community ingestion rates ranged between 0.1 and 0.3mg chlorophyll-a m–2day–1 in interfrontal areas, increasing to 2.0 and 9.0mg chlorophyll-a m–2day–1 in the APF and SCZ respectively. Mesozooplankton grazing removed up to 40% of the total chlorophyll stock in the SCZ, and 22% in the APF, on a daily basis. These estimates suggest that mesozooplankton exert a significant grazing impact on phytoplankton over much of the frontal areas studied. Recent investigations have shown that the geographic position of oceanic fronts and plankton biomass maxima in the study area have remained basically the same from the time of our sampling effort to date, meaning that our results apply to present conditions.

Are free-floating planktonic hydroids (Cnidaria, Hydrozoa) common components of the pelagic fauna from the South Brazilian Bight?

We analysed 267 zooplankton samples collected in the South Brazilian Bight (SBB; 23–27°S) to determine whether hydroids, typically benthic, are common components of the pelagic SBB. Two species, Clytia arborescens , recorded for the first time in the Atlantic Ocean, and Clytia sp. were identified. While these planktonic hydroids were frequent or relatively so in shallow shelf waters (~23% of the samples 100 m), abundances were low (up to 61 hydranths m −3 ) suggesting a low trophic impact. Such colonies are probably fragments of benthic colonies detached by storms and/or tides. Given the good condition of the coenosarc, existence of gastric content, and presence of reproductive structures, development of these species appears to be normal in the pelagic environment. Existence in the plankton may increase their capacity for dispersion.

Draft genome sequence of a novel culturable marine chroococcalean cyanobacterium from the South atlantic ocean.

ABSTRACT The novel chroococcalean cyanobacterium strain CENA595 was isolated from the deep chlorophyll maximum layer of the continental shelf of the South Atlantic Ocean. Here, we report the draft genome sequence for this strain, consisting of 60 contigs containing a total of 5,265,703 bp and 3,276 putative protein-coding genes.