Pedro Augusto Mendes de Castro Melo

Demersal zooplankton communities from tropical habitats in the southwestern Atlantic

Abstract Demersal zooplankton were captured with traps from a set of tropical coastal habitats (seagrass bed, coral reef, gravel, and sand bottoms) to allow comparisons among communities. Sampling was carried out during dry and rainy seasons in 2000 and 2001. Traps with and without light were placed at 18:00 and removed at 06:00 the next day for three consecutive days. Eighty-eight zooplankton taxa were identified. Copepoda was the most abundant group, outranking in relative abundance in seagrass and in sandy bottoms. Copepoda was mainly represented by Oithona oculata, Pseudodiaptomus acutus, and Acartia lilljeborgi. No significant differences were found among substrates (P=0.1464); however, differences were significant between light and dark traps communities (P=0.0410). The average density was 7113 (±3966) ind m−2 in the light and 4759 (±4825) ind m−2 in the dark. In the light traps, Amphipoda and O. oculata were more representative. Without light, the main group was Foraminifera (>40%). Cluster analysis presented two main groups, Itamaracá Island and Tamandaré Bay; light and dark traps formed separate groups within these location groups. The results allow us to assess the efficiency of the used traps in a set of habitats of the tropical coastal area and gives information on the preference of specific organism groups in one of the tested substrates.

Diurnal and spatial variation of the mesozooplankton community in the Saint Peter and Saint Paul Archipelago, Equatorial Atlantic

The aim of this study is to assess small-scale variations in and spatial comparisons among the composition, distribution and abundance of the main zooplankton groups in the Saint Peter and Saint Paul Archipelago (SPSPA). Plankton samples were collected in May 2008 by net with a 300 µm mesh size. Sampling was carried out at two stations, Inner and Outer, during five consecutive days in the early morning and late afternoon. A total of 153 zooplankton taxa were identified. Copepoda was the most abundant and frequent group (with 49 species identified). Exocoetidae (Teleostei) eggs were also present in large numbers. No significant differences were found between stations or between day and night samples. The observed biomass was low; however, it was superior to that observed in the open ocean. The density of zooplankton was also low, but it increased slightly during the night. Indicator species for upwelling, such as Phaenna spinifera and Flaccisagitta hexaptera , were observed. We conclude that physical factors are important for structuring the SPSPA zooplankton community.

Copepod distribution and production in a Mid-Atlantic Ridge archipelago

The Saint Peter and Saint Paul Archipelago (SPSPA) are located close to the Equator in the Atlantic Ocean. The aim of this study was to assess the spatial variations in the copepod community abundance, and the biomass and production patterns of the three most abundant calanoid species in the SPSPA. Plankton samples were collected with a 300 µm mesh size net along four transects (north, east, south and west of the SPSPA), with four stations plotted in each transect. All transects exhibited a tendency toward a decrease in copepod density with increasing distance from the SPSPA, statistically proved in the North. Density varied from 3.33 to 182.18 ind.m-3, and differences were also found between the first perimeter (first circular distance band) and the others. The total biomass varied from 15.25 to 524.50 10-3 mg C m-3 and production from 1.19 to 22.04 10-3 mg C m-3d-1. The biomass and production of Undinula vulgaris (Dana, 1849), Acrocalanus longicornis Giesbrecht, 1888 and Calocalanus pavo (Dana, 1849) showed differences between some transects. A trend of declining biodiversity and production with increasing distance from archipelago was observed, suggesting that even small features like the SPSPA can affect the copepod community in tropical oligotrophic oceanic areas.

A Synoptic Assessment of the Amazon River-Ocean Continuum during Boreal Autumn: From Physics to Plankton Communities and Carbon Flux

The Amazon generates the worlds largest offshore river plume, which covers extensive areas of the tropical Atlantic. The data and samples in this study were obtained during the oceanographic cruise Camadas Finas III in October 2012 along the Amazon River-Ocean Continuum (AROC). The cruise occurred during boreal autumn, when the river plume reaches its maximum eastward extent. In this study, we examine the links between physics, biogeochemistry and plankton community structure along the AROC. Hydrographic results showed very different conditions, ranging from shallow well-mixed coastal waters to offshore areas, where low salinity Amazonian waters mix with open ocean waters. Nutrients, mainly NO3− and SiO2−, were highly depleted in coastal regions, and the magnitude of primary production was greater than that of respiration (negative apparent oxygen utilization). In terms of phytoplankton groups, diatoms dominated the region from the river mouth to the edge of the area affected by the North Brazil Current (NBC) retroflection (with chlorophyll a concentrations ranging from 0.02 to 0.94 mg m−3). The North Equatorial Counter Current (NECC) region, east of retroflection, is fully oligotrophic and the most representative groups are Cyanobacteria and dinoflagellates. Additionally, in this region, blooms of cyanophyte species were associated with diatoms and Mesozooplankton (copepods). A total of 178 zooplankton taxa were observed in this area, with Copepoda being the most diverse and abundant group. Two different zooplankton communities were identified: a low-diversity, high-abundance coastal community and a high-diversity, low-abundance oceanic community offshore. The CO2 fugacity (fCO2sw), calculated from total alkalinity (1,450 < TA < 2,394 μmol kg−1) and dissolved inorganic carbon (1,303 < DIC < 2,062 μmol kg−1) measurements, confirms that the Amazon River plume is a sink of atmospheric CO2 in areas with salinities <35 psu, whereas, in regions with salinities >35 and higher-intensity winds, the CO2 flux is reversed. Lower fCO2sw values were observed in the NECC area. The ΔfCO2 in this region was less than 5 μatm (−0.3 mmol m−2 d−1), while the ΔfCO2 in the coastal region was approximately 50 μatm (+3.7 mmol m−2 d−1). During the cruise, heterotrophic and autotrophic processes were observed and are indicative of the influences of terrestrial material and biological activity, respectively.

Zooplankton From a Reef System Under the Influence of the Amazon River Plume

At the mouth of the Amazon River, a widespread carbonate ecosystem exists below the river plume, generating a hard-bottom reef (∼9500 km2) that includes mainly large sponges but also rhodolith beds. The mesozooplankton associated with the pelagic realm over the reef formation was characterized, considering the estuarine plume and oceanic influence. Vertical hauls were carried out using a standard plankton net with 200 μm mesh size during September 2014. An indicator index was applied to express species importance as ecological indicators in community. Information on functional traits was gathered for the most abundant copepod species. Overall, 179 zooplankton taxa were recorded. Copepods were the richest (92 species), most diverse and most abundant group, whereas meroplankton were rare and less abundant. Species diversity (>3.0 bits.ind-1) and evenness (>0.6) were high, indicating a complex community. Small holoplanktonic species dominated the zooplankton, and the total density varied from 107.98 ind. m-3 over the reef area to 2,609.24 ind. m-3 in the estuarine plume, with a significant difference between coastal and oceanic areas. The most abundant copepods were the coastal species ithona plumifera and Clausocalanus furcatus and early stages copepodites of Paracalanidae. The holoplanktonic Oikopleura, an important producer of mucous houses, was very abundant on the reefs. The indicator species index revealed three groups: (1) indicative of coastal waters under the influence of the estuarine plume [Euterpina acutifrons, Parvocalanus crassirostris, Oikopleura (Vexillaria) dioica and Hydromedusae]; (2) characterized coastal and oceanic conditions (Clausocalanus); (3) characterized the reef system (O. plumifera). Two major copepods functional groups were identified and sorted according to their trophic strategy and coastal-oceanic distribution. The species that dominated the coastal area and the area over the rhodolith beds are indicators of the estuarine plume and are mixed with species of the North Brazil Current. These species practically disappear offshore, where occur oceanic species commonly found in other oligotrophic tropical areas. This ecosystem shows a mixture of estuarine, coastal and oceanic communities coexisting in the waters over the Amazon reefs, with no significant differences among these areas. However, the MDS clearly separated the communities along the salinity gradient in the plume.

COMMUNITY STRUCTURE OF THE TINTINNIDS (CILIOPHORA: SPIROTRICHEA) IN THE REGION OF ABROLHOS (BAHIA, BRAZIL)

The tintinnid community in the region of Abrolhos (Bahia, Brazil) was studied during February 2012. We hypothesized that the tintinnid community structure varies significantly over a short temporal scale (photoperiod), as well as spatially over a short scale (on and away from the reefs), and a broad scale (distance of the reef area from the coast). Three areas in Abrolhos were studied. Two sampling points were delimited in each area, where the tintinnids were collected by horizontal subsurface plankton net (20 μm mesh-size) hauls. Sampling was undertaken every 6 hours, during 24 hours in each area. 24 species were found, all of which are of neritic, cosmopolitan, and of warm-water distribution. The only hypothesis that is not rejected is that related to variability on an extensive spatial scale. There are significant differences between the samples collected in the three areas studied (ANOVA p = 0.017). The clustering of the species highlights a continent-ocean gradient. There is one community typical of the internal arc, composed mainly of neritic agglutinated tintinnids, and another community typical of the external arc, composed mainly of hyaline warm-water and cosmopolitan tintinnids. The factor which exercises the greatest influence on the tintinnid community in the Abrolhos region is the distance from the coast.

The first occurrence of the Order Mormonilloida (Copepoda) in the Tropical Southwest Atlantic Ocean

This communication is the first report of the occurrence of the order Mormonilloida (Mormonilla phasma) in the tropical Southwestern Atlantic Ocean. Female individuals were found in surface waters from the shelf break state of Rio Grande do Norte (Northeastern Brazil) and between depths of 60 and 100 m in the epipelagic layer around the St. Peter and St. Paul Archipelago (equatorial Atlantic). This finding extends the vertical limits for this species.

Zooplankton from shrimp culture ponds in Northeastern Brazil

Zooplankton was examined in 14 commercial shrimp Litopenaeus vannamei ponds in tropical Brazil to assess their composition, determine their density, and indicate environmental quality. In each farm, two ponds and the water intake point were monitored in 2003. Sampling was made with a standard plankton net 50 micrometers mesh size. The zooplankton presented 40 taxa and was essentially composed of typical marine euryhaline species and suspensionfeeding forms. In all farms the dominant group was Copepoda with a total of 45%, followed by Protozoa (18%). The most abundant meroplankton were Polychaeta larvae, Gastropoda larvae, nauplii of Cirripedia and zoeae of Brachyura with large distribution in the region, sometimes dominating the community. Zooplankton abundance varied from 972+209 ind m -3 to 4,235 + 2,877 ind m -3 . In the studied marine shrimp culture ponds, copepods dominance were replaced by protozoan and rotifers as nutrient concentrations increased with the culture period, indicating that zooplankton trophic structure can be strongly affected by the occurrence of eutrophic conditions in shrimp ponds. The tendency of low species diversity is indicative of an unbalanced hypereuthrophic system decreasing the water quality and the cultured species. These results can be an important appointment to understand the effects of eutrophication in coastal plankton structure and its effects to marine aquatic food web.