Resilience of a zooplankton community subjected to marine intrusion in a tropical coastal lagoon

One of the main disturbances on Imboassica Lagoon is the occasional artificial opening of its sand bar. Following two such events, two environmental gradients were observed. One was directly related to entry of marine water (salinity gradient); and the other to a decrease in dilution of the nutrient load, because of water level reduction (trophic status gradient). Two stations were sampled. At Station 1, located near the sand bar, salinity increase caused a decrease in the total zooplankton density and a shift in community composition due to a loss of relatively small individuals (i.e. rotifers) and the subsequent entrance of larger ones (i.e. copepods). High diversity was related to salinity increases. At Station 2, located near the mouth of a sewage canal, the total zooplankton abundance and dominance were related to the salinity increase, while the highest richness and the lowest dominance were obtained at a high trophic state. The zooplankton community showed high persistence and resilience, which together with other ecological features in the system, returned to the pre-disturbance state 2 months after the sand bar was closed. Canonical correspondence analysis was a useful tool to assess system resilience.     

The zooplankton and other limnological features of a humic coastal lagoon (Lagoa Comprida,Macé, R.J.) in Brazil

Comprida lagoon is a shallow lagoon separated from the sea by a sand barrier. It has a brown-coloured freshwater with a high concentration of humic compounds. Its zooplankton community and limnological features were studied from March 1992 to December 1995. The lagoon was characterized by low transparency, acid water and relative constant physical–chemical features, except during sporadic marine entrances. The zooplankton, composed of holoplanktonic and meroplanktonic forms, consisted of 60 taxa. Eleven were permanent elements of the community: e.g. Bosminopsis deitersi, nauplii and copepodites of `Diaptomus' azureus. B. deitersi correlated positively with the lowest pH values and with the highest total dissolved nitrogen. Only four taxa correlated with chlorophyll-a concentration. Pigmentation in `D.' azureus is suggested to be as an energy reserve in a system where phytoplankton is probably light-limited.     

Temporal and spatial fluctuations of phytoplankton in a tropical coastal lagoon, southeast Brazil.

Spatial and temporal variability of the phytoplankton community in the tropical coastal Imboassica lagoon, an environment naturally isolated from the ocean by a narrow sandbar, was analysed every two weeks for 19 months by sampling three sites. During this study, the lagoon received direct input of marine water three times, resulting in remarkable salinity, nutrient concentrations and phytoplankton biomass variations in both temporal and spatial aspects. The phytoplankton biomass presented relatively low values ranging, on average, from 0.54 mg x L(-1) in the station closest to the sea (station 1) to 1.34 mg x L(-1) in the station close to a macrophyte bank (station 3). Diatoms and cryptomonads dominated in stations 1 and 2 (located relatively close to station 1, yet receiving the runoff of domestic sewage), and euglenoids, cryptomonads and dinoflagellates at station 3. Stations 1 and 2 usually presented the same dominant species but station 2 presented a higher phytoplankton biomass. On the other hand, station 3 showed more similar results concerning phytoplankton biomass with station 2, however the dominant species were usually different. The high fluctuations of salinity and the reduced nutrient availability are pointed out as the main factors structuring the dynamics of the phytoplankton community at the Imboassica lagoon.     

Hypersaline lagoons as conservation habitats: macro-invertebrates at Muni Lagoon, Ghana

A survey on the aquatic ecology of Muni Lagoon was carried out during the period December 1993 to July 1994. Samples of zooplankton, aufwuchs and benthos were taken from a number of stations, representative of the different habitat types that occurred in the lagoon. The aquatic invertebrate fauna of the lagoon is listed and the temporal and spatial distribution of the fauna is described. The fauna is depauperate and biodiversity was related closely to the hydrology and salinity of the lagoon waters. During the early part of the study period, with dry weather conditions, there was very little macro-invertebrate life within the waters of the lagoon. The invertebrate fauna was confined to crabs, which occupied the fringing vegetation in the southernmost portions of the lagoon. With the onset of rains and the flooding of the lagoon, the sand bar separating the lagoon from the sea was opened turning the lagoon into a tidal system. This event brought a radical change to the fauna of the lagoon with very diverse marine zooplankton in some stations. Within weeks, worms and juvenile crabs were found several kilometres inland from the sea opening, an indication of the rapid re-colonisation of a previously hypersaline environment. The anthropogenic threats to the aquatic portion of this Ramsar site have been assessed and prioritised.     

Macroinvertebrates associated with Chara in a tropical coastal lagoon (Imboassica lagoon,Rio de Janeiro,Brazil)

Imboassica lagoon is an urban coastal lagoon located in the municipality of Macaé (RJ), which has been exposed to a process of artificial eutrophication through the inflow of untreated sewage, as well as artificial openings of the sandbar that separates it from the ocean, provoking drastic modifications in this ecosystem. The sampling for the analysis of the community of macroinvertebrates associated with Charopyceae (Chara angolensis e C. fibrosa) were performed between October 1995 and October 1997, with a total of 9 samplings at two sampling stations: one located in the innermost area of the lagoon and another at the mouth of the main sewage channel, close to the sandbar. Throughout this period, four artificial sandbar-opening events were recorded, resulting in changes in the biomass of the macroalgae and in the densities of the macroinvertebrate populations. Through the analysis of the density of organisms per square meter, and density of organisms per 100 g dry weight of Chara, it was established that the biomass of the macroalgae has a direct influence on the density of the associated macrofauna. The greater development of the periphytic community in the area close to the inflow of sewage allows for the development of a community of macroinvertebrates with high densities, composed mainly of scraping organisms, such as the mollusc Heleobia australis (Hidrobiidae).     

Effects of the Sand Bar Breaching on Typha domingensis (PERS.) in a Tropical Coastal Lagoon

Coastal lagoons are usually subjected to several kinds of human impacts, especially eutrophication. The breaching of the sand bar, which separates the lagoon from the ocean, by human action, is a common process used to decrease the negative effects of eutrophication. The aims of this research were to evaluate the effects of the artificial sand bar breaching on the populations of the aquatic macrophyte Typha domingensis and the subsequent effects on nutrients concentration in a tropical coastal lagoon. Samplings were carried out monthly from February/01 to January/02 in a monospecific stand of T. domingensis at Imboassica lagoon (Rio de Janeiro/Brazil). Two sampling sites, in the middle and in the border of the stand, were marked in three different transects. Water depth was measured and the aerial biomass sampled with a 0.25 m² quadrat. The macrophyte samples were separated into live and dead material and the shoot length, shoot density and number of leaves were analyzed. All plant material was oven dried till constant weight and net primary production, dead stand crop production and the nutrients release through decomposition were estimated at each site. The decrease in water level due to sand bar opening affected negatively T. domingensis populations, but the most intense effects were observed in the middle of the stand. The shoot mortality was highly enhanced after the sand bar breaching and the nutrients were released through decomposition to the water column. It reflected on an input of 11.5 kg C m⁻², 0.22 kg N m⁻² and 0.13 kg P m⁻² into the lagoon, which represent from 22.5 to 44.8 ton P and 35.9 to 71.8 ton N to the lagoon. The decrease of nutrients concentration after the sand bar breaching was not successfully accomplished. The decay of T. domingensis stands due to the sand bar breaching neutralized the exportation of nutrients to the ocean, and contributed to the phosphorous increase in the water column. Thus, to a better management of aquatic ecosystems subjected to human eutrophication, the role of aquatic macrophytes decomposition on internal fertilization of aquatic ecosystems should be accounted.     

Analysis of a 24-hour cycle of zooplankton sampling in a lagoon of the Po River Delta

Short-term zooplankton samples were collected in a lagoon ofthe Po River Delta (Sacca del Canarin) over a 24-h cycle inAugust 1981. The biocoenosis was mainly represented by taxa(especially copepods) coming into the lagoon from the sea and,to a lesser extent, by autochthonous zooplankton (gastropod,cirripede and decapod larvae). Density fluctuations of sometaxa were found to be greatly influenced by hydro dynamic factors,in particular by the tidal currents. A daily balance of inputand output through one of the two mouths connecting the lagoonto the sea was calculated for different taxa; quantitative estimatesof zooplankton exchanges between lagoon and sea due to tidaltransportation were obtained.     

Abundance dynamics and functional role of predaceous <Emphasis Type="Italic">Leptodora kindtii</Emphasis> in the Curonian Lagoon

The abundance and distribution of predatory cladoceran Leptodora kindtii was investigated in the estuarine lagoon (Curonian Lagoon, SE Baltic Sea). Three hydrodynamically different parts of the lagoon were selected, representing transitory oligohaline, intermediate freshwater and stagnant freshwater sites. L. kindtii was least abundant at the oligohaline site, never occurring at salinities greater than 4 psu. At the two freshwater sites, the abundance of L. kindtii varied from a low of <0.1 up to 2.2 indv. L⁻¹ during peak abundance. Two peaks of L. kindtii abundance were observed with timing differences between stations: at the stagnant site the population of L. kindtii peaked two weeks earlier relative to the more hydrodynamically active sites, likely due to a 2°C higher May temperature. The small body size of L. kindtii in the lagoon (seasonal mean 2.68±0.6 mm) shows high fish predation pressure and predicts small cladocerans, juvenile copepods and rotifers being in the preferred prey size range. The calculated L. kindtii daily consumption during the population peak was as high as 100% of the daily zooplankton production, which implies high potential of this predator to shape the grazing zooplankton community in the lagoon.     

Macrophytes in the anthropic constructions of the Venice littorals and their ecological assessment by an integration of the “CARLIT” index

A check-list of the macroalgae which colonize the artificial structures “dykes” formed by limestone blocks, placed between the northern Adriatic Sea and the Venice Lagoon to protect the wide sea inlets of Lido and Malamocco, the stone breakwaters and the submerged reefs parallel and perpendicular to the sea coastline of the Lido island “Murazzi” is presented. Macroalgae have been sampled monthly during one-year period (February 2007–January 2008) both in the lagoon inlets and along the marine coast. Flora was represented by 213 taxa: 61 Chlorophyta, 114 Rhodophyta, 38 Ochrophyta (37 Phaeophyceae, 1 Xanthophyceae), with the richest and luxuriant vegetation in the lagoon inlet areas. The application of the Rhodophyta/Chlorophyta (R/C) index and the Expert-Macrophyte Quality Index (E-MaQI) highlighted the “High” ecological status (EQR > 0.9) of the lagoon inlet areas.As E-MaQI is not applicable in marine areas, an adaptation of CARLIT to the anthropic structures of the north-western coasts of the northern Adriatic Sea and its integration with the dominant taxa is proposed.The application of the revised index to the Lido dykes and breakwaters placed along the marine littorals shows “Moderate” conditions.     

Neutral processes and species sorting in benthic microalgal community assembly: effects of tidal resuspension

Benthic microalgae (BMA) provide vital food resources for heterotrophs and stabilize sediments with their extracellular secretions. A central goal in ecology is to understand how processes such as species interactions and dispersal, contribute to observed patterns of species abundance and distribution. Our objectives were to assess the effects of sediment resuspension on microalgal community structure. We tested whether taxa‐abundance distributions could be predicted using neutral community models (NCMs) and also specific hypotheses about passive migration: (i) As migration decreases in sediment patches, BMA α‐diversity will decrease, and (ii) As migration decreases, BMA community dissimilarity (β‐diversity) will increase. Co‐occurrence indices (checkerboard score and variance ratio) were also computed to test for deterministic factors, such as competition and niche differentiation, in shaping communities. Two intertidal sites (mudflat and sand bar) differing in resuspension regime were sampled throughout the tidal cycle. Fluorometry and denaturing gradient gel electrophoresis were utilized to investigate diatom community structure. Observed taxa‐abundances fit those predicted from NCMs reasonably well (R² of 0.68–0.93), although comparisons of observed local communities to artificial randomly assembled communities rejected the null hypothesis that diatom communities were assembled solely by stochastic processes. No co‐occurrence tests indicated a significant role for competitive exclusion or niche partitioning in microalgal community assembly. In general, predictions about relationships between migration and species diversity were supported for local community dynamics. BMA at low tide (lowest migration) exhibited reduced α‐diversity as compared to periods of immersion at both mudflat and sand bar sites. β‐diversity was higher during low tide emersion on the mudflat, but did not differ temporally at the sand bar site. In between‐site metacommunity comparisons, low‐ and high‐resuspension sites exhibited distinct community compositions while the low‐energy mudflats contained higher microalgal biomass and greater α‐diversity. To our knowledge this is the first study to test the relevance of neutral processes in structuring marine microalgal communities. Our results demonstrate a prominent role for stochastic factors in structuring local BMA community assembly, although unidentified nonrandom processes also appear to play some role. High passive migration, in particular, appears to help maintain species diversity and structure communities in both sand and muddy habitats.     

Tropical zooplankton in the highly-enclosed lagoon of Taiaro Atoll (Tuamotu Archipelago, French Polynesia)

 Nocturnal zooplankton assemblages around Taiaro Atoll were sampled over six nights during February 1994. Replicate zooplankton samples were collected at windward and leeward locations in the enclosed lagoon and adjacent ocean with a metered net (85 cm diameter, 500 μm mesh) towed for 15 min at 5 m depth. The zooplankton community in the lagoon was very different from that in the ocean. Oceanic samples contained 50 mostly holoplanktonic taxa (diversity index, H′=2.62; evenness index, J′=0.67). Lagoonal samples contained 19 mostly meroplanktonic taxa (H′=1.54, J′=0.52) with three taxa (decapod larvae; an ostracod, Cypridina sp.; a copepod, Acartia fossae) contributing >90% of the individuals. Unlike the ocean, zooplankton distributions in the lagoon were not homogenous; instead spatial patterns were apparently formed by the interaction between hydrodynamic processes and species-specific behaviour. Accepted: 28 August 1997     

A marine zooplankton community vertically structured by light across diel to interannual timescales

The predation risk of many aquatic taxa is dominated by visually searching predators, commonly a function of ambient light. Several studies propose that changes in visual predation will become a major climate-change impact on polar marine ecosystems. The High Arctic experiences extreme seasonality in the light environment, from 24 h light to 24 h darkness, and therefore provides a natural laboratory for studying light and predation risk over diel to seasonal timescales. Here, we show that zooplankton (observed using acoustics) in an Arctic fjord position themselves vertically in relation to light. A single isolume (depth-varying line of constant light intensity, the value of which is set at the lower limit of photobehaviour reponses of Calanus spp. and krill) forms a ceiling on zooplankton distribution. The vertical distribution is structured by light across timescales, from the deepening of zooplankton populations at midday as the sun rises in spring, to the depth to which zooplankton ascend to feed during diel vertical migration. These results suggest that zooplankton might already follow a foraging strategy that will keep visual predation risk roughly constant under changing light conditions, such as those caused by the reduction of sea ice, but likely with energetic costs such as lost feeding opportunities as a result of altered habitat use.     

Climate shifts the interaction web of a marine plankton community

Climatic effects in the ocean at the community level are poorly described, yet accurate predictions about ecosystem responses to changing environmental conditions rely on understanding biotic responses in a food‐web context to support knowledge about direct biotic responses to the physical environment. Here we conduct time‐series analyses with multivariate autoregressive (MAR) models of marine zooplankton abundance in the Northern California Current from 1996 to 2009 to determine the influence of climate variables on zooplankton community interactions. Autoregressive models showed different community interactions during warm vs. cool ocean climate conditions. Negative ecological interactions among zooplankton groups characterized the major warm phase during the time series, whereas during the major cool phase, ocean transport largely structured zooplankton communities. Local environmental conditions (sea temperature) and large‐scale climate indices (El Niño/Southern Oscillation) were associated with changes in zooplankton abundance across the full time series. Secondary environmental correlates of zooplankton abundance varied with ocean climate phase, with most support during the warm phase for upwelling as a covariate, and most support during the cool phase for salinity. Through simultaneous quantitation of community interactions and environmental covariates, we show that marine zooplankton community structure varies with climate, suggesting that predictions about ecosystem responses to future climate scenarios in the Northern California Current should include potential changes to the base of the pelagic food.     

Eleocharis mutata (L.) Roem. et Schult. subject to drawdowns in a tropical coastal lagoon,State of Rio de Janeiro,Brazil

This investigation of the aquatic macrophyte Eleocharis mutata (L.) Roem. Et Schult. was carried out in Imboassica lagoon, a coastal lagoon in Macaé (22°50S; 44°42W), in the northern part of Rio de Janeiro, Brazil. The sandbar separating this lagoon from the ocean has been opened several times for flood control and to allow the entrance of marine species of commercial interest. The barrier bar has been breached without appropriate planning, and the consequences of breaching for the lagoon ecosystem are poorly understood. These openings drastically affect the structure and functioning of the lagoon, but there are no data on possible effects on macrophyte communities. In this project, we obtained data on the increase of the distribution, biomass accumulation and production rates of E. mutata in the establishment of a new stand, in an effort to relate effects of sandbar breach events to the expansion of this species. During 22 months of sampling, 4 breachings of the sandbar occurred, and E. mutata increased its area of coverage by about 810⁴ m², or 2.5% of the total area of the lagoon. The total aerial biomass reached a maximum of 1515 g DW m^–2, and the underground biomass reached 583 g DW m^–2. During the establishment and development of the stand, both dead and live aerial biomass and underground biomass tended to accumulate. Aerial net primary production (ANPP) was quite variable, reaching a maximum of 18.9 g DW m^–2 d^–1. We conclude that the sudden variations in water level caused by breaches in the sandbar were beneficial to the expansion of this species in Imboassica lagoon.     

Seasonal hydrochemical variation in a tropical coastal lagoon (A?u Lagoon, Brazil).

Hydrochemical conditions in the A?u Lagoon are described using spatial and temporal variations of various limnological variables (water temperature, dissolved oxygen, electric conductivity, total alkalinity, carbon dioxide, dissolved and total nutrients (N, P and Si), and chlorophyll a). Collected data was used in order to understand the structure and functioning of an enclosed coastal lagoon strongly influenced by climatic conditions. Water samples were collected monthly (November 1999-December 2000) in five sampling stations established along the lagoon. A decreasing spatial gradient of electrical conductivity was observed beginning from a sand bar region between the lagoon and the sea in the direction of the sweet-water input area. The positive correlation observed between the pH and dissolved oxygen (DO) values, and the negative one observed between pH values and those of carbon dioxide (CO2), evidenced coupled biological processes, e.g., primary production and decomposition. Both spatial and temporal variation of dissolved nutrients showed fast increase and decrease in the beginning of summer, suggesting that nutrient input resulting from rainfall stimulates phytoplankton production, as reflected by chlorophyll a concentration increase.     

Distribution patterns of micro- and meso-zooplankton communities in sea ice regions of Lützow-Holm Bay, East Antarctica

In the Southern Ocean, zooplankton research has focused on krill and macro-zooplankton despite the high densities of micro- and meso-zooplankton. We investigated their community structure in relation to different sea ice conditions around Japan’s Syowa Station in Lützow-Holm Bay, in the summers of 2011 and 2012. Zooplankton samples were collected using vertical hauls (0–150 m), with a closing net of 100-μm mesh size. The results of cluster analysis showed that the communities in this region were separated into fast ice, pack ice, and open ocean fauna. The fast ice fauna had lower zooplankton abundance (393.8–958.9 inds. m^?3) and was dominated by cyclopoid copepods of Oncaea spp. (54.9–74.8 %) and Oithona similis (6.6–19.9 %). Deep-water calanoid copepods were also found at the fast ice stations. Pack ice and open ocean fauna had higher zooplankton abundance (943.6–2,639.8 inds. m^?3) and were characterized by a high density of foraminiferans in both years (6.6–61.9 %). Their test size distribution indicated that these organisms were possibly released from melting sea ice. The pteropod Limacina spp. was a major contributor to total abundance of zooplankton in the open ocean zone in 2012 (26.4 %). The physical and/or biological changes between 2 years may affect the abundance and distribution of the dominant zooplankton taxa such as cyclopoid copepods, foraminiferans, and pteropods. Information on the relationships between the different species associated with sea ice will help to infer the possible future impacts of climate change on the sea ice regions.     

Plankton community and the relationship with the environment in saline lakes of Onon-Torey plain,Northeastern Mongolia

The plankton community of sixteen saline lakes located on Onon-Torey plain (Northeastern Mongolia) during the filling phase and the raising of the water level was investigated in July 2011. Thirty-five taxa of phytoplankton and thirty-one species of zooplankton were found. For phytoplankton, blue-green algae (Merismopedia elegans, Anabaenopsis elenkinii, Arthrospora fusiformis, Spirulina major, Lyngbya sp., Oscillatoria sp.) and green algae (Monoraphidium minutum, Tetrastrum komarekii, Ankyra ocellata, Oocystis sp.) were dominant. For zooplankton, Filinia longiseta, Brachionus plicatilis, B. variabilis, Hexarthra mira (Rotifera), Daphnia magna, Moina brachiata, M. mongolica (Cladocera), Arctodiaptomus bacillifer, Mixodiaptomus incrassatus, Metadiaptomus asiaticus (Copepoda) dominated. Mineralization, active hydrogen ratio, dissolved oxygen and water temperature were the main factors influencing the diversity, structure and distribution of plankton organisms in the steppe lakes during low water level. The RDA analysis for phytoplankton and zooplankton from different lakes was carried out for selected two groups which included lakes and a subset related species. The first group is of oligohaline and mesohaline lakes in which mostly green algae, rotifers and copepods inhabit. The second group is of mesohaline and polyhaline lakes with mainly blue-green algae, some crustaceans and rotifers inhabiting. High abundance and biomass of Spirulina major, Oscillatoria sp. and Brachionus variabilis were observed in lakes with high mineralization, pH and temperature.     

Impacts of the 2011 Tsunami on Sediment Characteristics and Macrozoobenthic Assemblages in a Shallow Eutrophic Lagoon,Sendai Bay,Japan

A huge tsunami is one of the greatest disturbance events in coastal benthic communities, although the ecological consequences are not fully understood. Here we examined the tsunami-induced changes in the sediment environment and macrozoobenthic assemblage in a eutrophic brackish lagoon in eastern Japan. The 7.2-m-high tsunami completely replaced muddy sediment with drifting sea sand throughout the lagoon, leading to the drastic changes in quantity and quality of sedimental organic matters, sulfide contents, and sediment redox condition. Intensive physical stress devastated the benthic community, but the disappearance of sulfidic muddy bottoms significantly improved the habitat quality for macrozoobenthos. The re-established macrozoobenthic community after 5 months was characterized by (1) a 2-fold higher total density, but sharp declines in species richness, diversity, and evenness; (2) an increased density of opportunistic taxa (e.g., polychaete Pseudopolydora spp. and amphipod Monocorophium uenoi) in newly created sandy bottoms; and (3) disappearance of several dominant taxa including bivalves and chironomid larvae. These findings indicate that the sensitivity and recovery potential of macrozoobenthos were highly taxa-specific, which was closely related to the taxa’s ecological characteristics, including tolerance to physical disturbance, life-history traits, and life form. Our data revealed the rapid recolonization of opportunistic macrozoobenthos after a huge tsunami, which would contribute to the functional recovery of estuarine soft-bottom habitats shortly after a disturbance event.     

Temporal and spatial patterns of crustacean zooplankton dynamics in a transitional lagoon ecosystem

Patterns and mechanisms of plankton crustacean seasonal succession in the eutrophic freshwater Curonian lagoon (south-eastern Baltic Sea) were analysed on the basis of four-year (1995, 1996, 1998 and 1999) field sampling results. The seasonal crustacean zooplankton succession in the lagoon appears to be the consistent six-stage sequence of four distinct species complexes. Each stage is characterised by its individual species composition and quantitative characteristics. The uniform and periodic pattern of the limnetic zooplankton crustacean successional stages in the lagoon indicates that the seasonal succession of the limnetic zooplankton is not disturbed by unpredictable environmental fluctuations, such as brackish water inflows. Seasonal zooplankton succession is also comparatively uniform at a spatial scale. Not more than two adjacent successional stages were found across the northern part of the lagoon during each of 11 seasonal surveys. Comparison between monthly water residence time and dominant plankton crustacean species life cycle duration points to a more transitory plankton community in spring while in the summer it is not much influenced by lagoon hydrodynamics. Consequently, the Curonian lagoon crustacean community quite closely follows the Plankton Ecology Group (PEG)-described freshwater lake seasonal succession in summer and turns into a lentic-like system in spring and autumn.     

Sewage input effects on the macroinvertebrate community associated to Typha domingensis Pers in a coastal lagoon in southeastern Brazil.

This study was carried out at Imboassica Lagoon, located in an urban zone in the municipality of Macaé, Rio de Janeiro state, Brazil. This lagoon has been subject to anthropogenic impacts due to the increasing city population, such as the input of sewage. Areas of variable degree of anthropogenic influence in the lagoon were compared regarding the structure of the macroinvertebrate community associated to Typha domingensis leaves. For sampling, we used 35 x 20 cm net plastic bags, with 6.8 mm mesh containing T. domingensis leaves for colonization. Two different sampling stations were selected: station A, under direct input of sewage; and station B with lesser sewage influence. The bags were removed after 20, 40 and 75 days of colonization. For each sample the Shannon-Wiever Diversity, Pielou Evenness, Jaccard Similarity Indices, Correspondence Analysis and taxonomic richness were calculated. A total of 31,874 individuals were sampled, belonging to 34 taxa. The main taxonomical groups were: Oligochaeta (41%), Chironomidae (40%), Ancylidae (4.6%), Polymitarcyidae (4%) and Thiaridae (3%). At station A, the taxonomic richness, the Evenness and Diversity values were lower than in station B. On the other hand, the total density was three times higher in station A than in B. It was already possible to discriminate the community structure of each sampling station in the first sampling. Trichoptera and Ephemeroptera were the main exclusive groups of station B and are considered good water quality indicators due to their high sensibility to contamination. The major contribution to discriminate between the macroinvertebrate communities of the two sample stations came from Chironomidae, Oligochaeta and Ephemeroptera.