Paulo Cesar Abreu

Importance of biofilm for water quality and nourishment in intensive shrimp culture

Abstract Experiments were conducted to test the usefulness of biofilms—a microbial consortium associated with extracellular polymeric substances attached to submersed surfaces—in reducing the levels of ammonium and phosphate of rearing system water, and as a food source for the shrimp Farfantepenaeus paulensis . A mature biofilm, which is able to keep ammonium and phosphate at low levels, occurred 10–15 days after tank cleanup, and was characterized by chlorophyll- a concentration around 5 μg/cm 2 . It was mainly composed of pennate diatoms ( Amphora , Campylopyxis , Navicula , Sinedra , Hantschia and Cylindrotheca ; ca. 9×10 4 cells/mg of biofilm) and filamentous cyanobacteria ( Oscillatoria and Spirulina ; ca. 2×10 5 cells/mg), though bacteria (max. 1.48×10 7 /mg), flagellates (max. 1.08×10 3 /mg) and ciliates (max. 3.51×10 2 /mg) were also present. Pennate diatoms and filamentous cyanobacteria were responsible for the largest uptake of ammonium from the water, but nitrifying bacteria also played an important role. The presence of a biofilm lead to reduced exportation of phosphorus (33% less phosphate) and to a higher output of nitrate+nitrite, instead of ammonium. Biofilm was also an important complementary food source for the shrimp, increasing their growth.

The use of microorganisms as food source for Penaeus paulensis larvae.

Abstract Three experiments were conducted to test the usefulness of microorganisms as food source for the Penaeus paulensis larvae. Larvae fed only bacteria survived longer (3 days) than those cultured in filtered (

Human activities and climate variability drive fast-paced change across the world's estuarine-coastal ecosystems

Time series of environmental measurements are essential for detecting, measuring and understanding changes in the Earth system and its biological communities. Observational series have accumulated over the past 2-5 decades from measurements across the worlds estuaries, bays, lagoons, inland seas and shelf waters influenced by runoff. We synthesize information contained in these time series to develop a global view of changes occurring in marine systems influenced by connectivity to land. Our review is organized around four themes: (i) human activities as drivers of change; (ii) variability of the climate system as a driver of change; (iii) successes, disappointments and challenges of managing change at the sea-land interface; and (iv) discoveries made from observations over time. Multidecadal time series reveal that many of the worlds estuarine-coastal ecosystems are in a continuing state of change, and the pace of change is faster than we could have imagined a decade ago. Some have been transformed into novel ecosystems with habitats, biogeochemistry and biological communities outside the natural range of variability. Change takes many forms including linear and nonlinear trends, abrupt state changes and oscillations. The challenge of managing change is daunting in the coastal zone where diverse human pressures are concentrated and intersect with different responses to climate variability over land and over ocean basins. The pace of change in estuarine-coastal ecosystems will likely accelerate as the human population and economies continue to grow and as global climate change accelerates. Wise stewardship of the resources upon which we depend is critically dependent upon a continuing flow of information from observations to measure, understand and anticipate future changes along the worlds coastlines.

Structuring of a postspring phytoplankton community by manipulation of trophic interactions

Structuring of a postspring phytoplankton community by manipulation of trophic interactions

The role of free and attached microorganisms in the decomposition of estuarine macrophyte detritus

Abundance and respiration of free and attached microorganisms were monitored during the decomposition of the seagrass Scirpus maritimus leaves in laboratory microcosms for 30 days. There was a clear succession between bacteria and heterotrophic flagellates during the course of the study. The beginning of the study (1-4 days) was characterized by higher rates of bacterial respiration, compared to the later periods. Free microorganisms were responsible for more than half of the respiration (65%) within the microcosms, suggesting that they were responsible for the mineralization of the bulk of the macrophyte detritus following its dissolution. On the other hand, estimates of activity on a per cell basis revealed that individual attached bacteria had much higher (3- to 4-fold) respiration rates than free bacteria, suggesting attached bacterial activity may play a key role in the breakdown and dissolution of particulate detritus in estuarine waters. The findings suggest different but coupled roles for attached and free bacteria in nature.

Drought Effects on Pelagic Properties in the Shallow and Turbid Patos Lagoon, Brazil

The effect of a 7-mo drought (La Niña 1988) was evaluated on pelagic properties in the large Patos Lagoon (30°12′–32°12′S, 50°40′–52°15′W). From December 1987 to December 1988, surface water was sampled along the longitudinal axis of the lagoon for temperature (10–29°C), salinity (0–31.4), dissolved inorganic phosphate (0.02–4.73 μM), nitrate (0.05–66.25 μM), nitrite (0.01–3.54 μM), ammonium (0.09–33.19 μM), silicate (1.11–359.20 μM), phytoplankton chlorophylla (chl; 0.4–41.2 mg m−3), primary production (gross PP 1.72–161.82 mg C m3 h−1; net PP 0.04–126.19 mg C m3 h−1), and species composition and abundance (42–4,961 ind ml−1). In the wet season the whole system acted as a river and light availability limited phytoplankton growth. During the drought from February to August monthly freshwater runoff was low and the inflow of marine water to the southern sector generated spatial variability of the analyzed properties and five functional areas were recognized. The northernmost Guaíba River (1) presented low light availability and phytoplankton chl concentration compared to the northern limnetic area (2) (chl mean 13.3 μg I−1; max 41.2 μg I−1; gross PP mean 52.6 mg C m3 h−1), which acted as a biological filter removing dissolved inorganic nutrients. Silicate concentration was strongly diminished in this area due to diatom uptake (Aulacoseira granulata, 9,330 cells ml−1). In the northern limnetic and central oligohaline (3) areas, phytoplankton biomass was controlled by light but nitrogen also played a limiting role. In the southern area (4) that is under marine influence, low chl concentration (mean 4.5 μg I−1) and gross PP (mean 28.1 mg C m3 h−1) coincided with co-limitation of nitrogen and light while the channel to the ocean (5) was strongly light limited. This study demonstrated that low light and high silicate input had a buffer effect at Patos Lagoon, hampering negative expression of cultural eutrophication. The main effect during the drought period occurred in the northern limnetic region, where low silicate values due to diatom uptake led to higher cyanobacteria abundance, and enhanced mineralization occurred in the central oligohaline lagoon. Increased rainfall resulted in light limitation and decreasing primary production in the entire freshwater lagoon, and the adjacent coastal region benefited from nutrient enrichment.

Influence of the Hydrological Cycle on the Bacterioplankton of an Impacted Clear Water Amazonian Lake

A bstractFree-living and attached bacterial population sizes were determined fortnightly from December 1991 to December 1992 in natural and disturbed areas of an Amazonian clear water lake (Batata Lake, Pará, Brazil) impacted by bauxite tailings. The bacterioplankton showed distinct patterns during different phases of the hydrological cycle. Total bacterial population size and rates of thymidine incorporation (measured during high and low water phases) were high during low water, with values ranging from 3.3 × 105 to 1.1 × 106 cells ml−1, and from 0.28 to 4.01 μg C l−1 h−1, respectively. The population size of free-living bacteria was larger at the natural station, while no differences were observed between attached bacterial populations at both stations. However, production and turnover rate of attached bacteria were high at the disturbed area. During low water, bacterial growth appeared to be driven mainly by the input of dissolved organic carbon (DOC) from phytoplankton origin. During high water, bacterial abundance was reduced, probably as the result of dilution and the input of less labile DOC from floodplains. The presence of bauxite tailings seems to influence bacterial dynamics in an indirect way, probably due to shading of phytoplankton cells and, hence, reducing the DOC supply for bacterial growth. This study, the first on the microbial ecology of an Amazonian clear water lake, demonstrated that water level variations exert a strong influence on the bacterioplankton dynamics.

Bacterial dynamics of the Patos Lagoon estuary, southern Brazil (32°S, 52°W): Relationship with phytoplankton production and suspended material

A field study of the microbial food web was conducted in a shallow region of the Patos Lagoon estuary (32°07′S; 52°06′W) between March 1989 and March 1990. On average, bacterial biomass (mainly attached bacteria) constituted 35·8% of the particulate organic carbon (POC) and exceeded phytoplankton biomass for several months. Bacterial growth, measured as the frequency of dividing cells (FDC), was significantly correlated with phytoplankton production (r = 0·70, p

Nutrient-rich saltwater and its influence on the phytoplankton of the patos lagoon estuary, Southern Brazil

Five cruises carried out in the main navigation channel of the Patos Lagoon estuary, southern Brazil, between June and December 1989, showed high concentrations of ammonium (up to 3.0 μM), nitrate (up to 13.0 μM), and phosphate (up to 3.0 μM) in the surface saltwater close to the lagoons mouth. High values of chlorophyll a were also measured in euhaline waters. The influence of nutrient-rich saltwater on phytoplankton production was found in a sequence of weekly measurements conducted at a shallow fixed station between September and November 1989. Peaks of carbon uptake coincided with high nitrate concentration measured during the intrusion of saltwater. Possible causes for the positive relationship between salinity and nutrients such as sewage input, sediment resuspension and return of previously exported estuarine water to the lagoon are discussed.

Efeito da densidade de estocagem sobre o biofilme e o desempenho de pós-larvas do camarão-rosa FarfantePenaeus paulensis cultivadas em gaiolas

O objetivo deste estudo foi analisar a influencia da densidade de estocagem na sobrevivencia e no crescimento de pos-larvas de F. paulensis cultivadas em gaiolas durante a fase de bercario. Alem disso, foram identificados e quantificados os principais microrganismos presentes no biofilme formado nos substratos artificiais colocados dentro das gaiolas. Foram usadas gaiolas com 4 m2 de fundo e com substratos artificiais, nas densidades de 100, 200, 300, 400 e 500PL25 m-2. O experimento durou 35 dias. Observou-se uma relacao negativa entre o aumento da densidade de estocagem de camaroes e a sobrevivencia e o crescimento destes. Foi observada uma preferencia pelo consumo de diatomaceas centricas. A viabilidade tecnica do cultivo de F. paulensis em gaiolas foi confirmada. O cultivo de F. paulensis em gaiolas na fase de bercario pode ser feito em densidades de ate 400PL m-2, sem maiores perdas em sua sobrevivencia e seu crescimento.