Macroinvertebrate Fauna Research Articles

Bivalve shell beds in the Triassic of the Sierra De Gádor (Alpujárride complex, Betic Cordillera, SE Spain)

Abstract The Peñón the Bernal section in the Sierra de Gádor comprises a succession of limestones, marly limestones and marls in the upper part of the Gádor unit, which belongs to the Alpujárride Complex in the Internal Zones of the Betic Cordillera. Several shell beds in this section and the locality of La Zarba in the same unit include relatively well-preserved macroinvertebrate assemblages. These beds reflect shell concentrations caused by storms and later colonised by epifaunal communities of cemented, epibyssate and endobyssate bivalves. Sedimentary features, fossil traces, and composition of bivalve assemblages indicate that the succession accumulated in a peritidal environment in a restricted carbonate platform with cyclic changes in water depth. The identified bivalve and ammonoid taxa suggest a Ladinian (Middle Triassic) age for the limestones, marly limestones and marls culminating the Gádor unit, so far considered as Upper Triassic in age. Like in other domains in the Betic Cordillera, the macroinvertebrate fauna has strong affinities with the Sephardic bioprovince.

Investigation of benthic macroinvertable fauna and some environmental variables in Sızır Waterfall (Gemerek-Sivas)

In this study, the benthic macroinvertebrate fauna of Sızır Waterfall, which is located in Sivas Province (Türkiye) and has an important place in recreational activities, and some environmental variables (velocity speed, water temperature, pH, conductivity, dissolved oxygen, total hardness of water, Ca, Mg, Cl, salinity, total amount of dissolved matter, PO4, SO4, NO2-N, NO3-N contents) that may be effective in their distribution were investigated. Also, some elements (Li, B, Na, Al, K, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, Cd, Sb, Ba, Tl, Pb) and a total of 181 types of pesticides were investigated in the studied area. During the wet and dry seasons of 2022, samplings were made from a total of 3 stations: at the beginning of the waterfall (upstream), inside the waterfall (waterfall) and at the exit of the waterfall (downstream). While individuals belonging to Oligochaeta (Potamothrix sp.), Gastropoda (Physa sp.), Amphipoda (Gammarus pseudosyriacus), Ephemeroptera (Baetis sp.), Plecoptera, Trichoptera, Coleoptera, Diptera and Odonata were determined. Also the physicochemical analysis results were evaluated in terms of water quality. The physicochemical and biological data of the sampling stations were examined statistically, and based on the similarity obtained, the effects of environmental variables on the distribution of macroinvertebrates were evaluated. The relationship between physicochemical data was analyzed using Pearson Correlation Analysis.

Environmental factors affecting the distribution of Spongillidae (Porifera) in an artificial channel (in north-western Italy)

The hydrographic network of the upper Po Valley (NW Italy) is characterized by the presence of numerous hydroelectric plants, often powered by artificial channels. These man-made water courses, which range from a few hundred meters to several kilometers in length, are used to convey water from the rivers to the electricity production plant. Power canals are usually characterized by concrete banks and bottoms, a geometric profile, and the absence of riparian vegetation so that they host peculiar invertebrate communities, often extremely well adapted to life in a completely artificial habitat. Sponges are an often little considered component of the freshwater macroinvertebrate fauna, whose functions and role within communities can be of considerable interest. These sessile, filter-feeding organisms can colonize artificial channels, but little is known about the local environmental characteristics that influence their distribution. In this study, we investigated the distribution of a freshwater sponge family Spongillidae, in a 4.5 km long artificial channel in Rocca Grimalda (Alessandria, NW Italy). A total of 863 specimens were localized and measured, and selected environmental characteristics were recorded. Results suggested that the distribution of sponges depends mainly on the lighting rather than the type of substrate or other local factors, so that this taxon is well-suited to colonizing artificial environments with good water quality conditions.

Large shallow lake response to anthropogenic stressors and climate change: Missing macroinvertebrate recovery after oligotrophication (Lake Balaton, East-Central Europe)

East-Central Europe's largest shallow lake, Balaton, experienced strong eutrophication in the 1970–80s, followed by water quality improvement and oligotrophication by 2010 CE. Recently however, repeated cyanobacterial blooms occurred and warned that internal P-recycling can act similarly to external P load, therefore we need a better understanding of past water level (WL) and trophic changes in the lake. In this study we discuss the last 500-yr trophic, WL and habitat changes of the lake using paleoecological (chironomids, pollen) and geochemical (sediment chlorophyll, TOC, TS, TN, C/H ratio, major and trace element) methods. We demonstrate that the most intensive and irreversible change in the macroinvertebrate fauna occurred during the period of economic boom between the First and Second World War (∼1925–1940 CE), when large-scale built-in and leisure use of the lake has intensified. At that time, the Procladius-Microchironomus-Stempellina dominated community transformed to Procladius-Chironomus plumosus-type-Microchironomus community that coincided with land use changes, intensified erosion and water-level regulation in the lake with the maintenance of year-round high WL. This was followed by the impoverishment and population size decrease of the chironomid fauna and Procladius dominance since 1940 CE, without any recovery after 1994 CE despite the ongoing oligotrophication. Accelerated rate of change and turnover of the fauna was connected to an increase in the benthivorous fish biomass and eutrophication. The basin lost almost completely its once characteristic Stempellina species between 1927 and 1940 CE due to trophic level increase and seasonal anoxia in the Szemes Basin. Reference conditions for ecosystem improvement were assigned to 1740–1900 CE. We conclude that in spite of the ongoing oligotrophication, the re-establishment of the Procladius-Microchironomus-Stempellina assemblage is hampered, and requires fish population regulation.

Evaluation of the Aquatic Oligochatea Fauna and Seasonal Changes in Water Quality of the Büyükçekmece Dam Lake, which Provides Water to İstanbul

This study was conducted at 4 stations in Büyükçekmece Dam lake in 2020. In this study, water and Oligochaeta samples were collected seasonally. Parameters such as secchi disk depth, water temperature, dissolved oxygen, pH, electrical conductivity, salinity, total hardness, nitrite nitrogen, phosphate and nitrate nitrogen were measured. Water quality parameters were qualified by SKKY (2004) ve TSWQR (2021). Also, the study, Limnodrilus hoffmeisteri (Claparède, 1862) and Limnodrilus udekemianus (Claparède, 1862) species belonging to Oligochaeta were found in the dam lake. The number of individuals per m2 and % dominance ratios of species were also calculated. It is recommended that similar and more comprehensive studies be carried out periodically in the dam lake to monitor the water quality of the dam lake regularly and to determine the benthic macroinvertebrate fauna.

Benthic invertebrate fauna of a forest spring on the Muravyov- Amursky Peninsula (Primorsky Krai, Southern Russian Far East)

The fi rst data on spring macroinvertebrate fauna of the Southern Russian Far East are presented. Macrobenthos of a small forest spring classifi ed as helocrene includes at least 21 species from 20 genera and 17 families in Arthropoda and Platyhelminthes. Main groups of benthic organisms are amphipods, planarians, larvae of dipterous insects, caddisfl ies, stonefl ies and mayfl ies, small water beetles. The following invertebrates are defi ned to the species level: planaria Phagocata sibirica, stonefl y Skwala compacta, caddisfl y Glossosoma angarensis, aquatic beetles Hydraena riparia (imago) and Heterlimnius gapyeongensis (larvae), amphipods Gammarus koreanus and hypogean Procrangonyx primoryensis. The macrobenthos of the spring is also ecologically diverse. Here, rheo- and stagnophiles, highly specialized stygo- and crenobionts, and species with wide ecological niches, sharply diff ering in their preferences, closely coexist.

Infrequent Long-Range Dispersal and Evolution of a Top Terrestrial Arthropod Predator in the Sub-Antarctic.

AbstractThe sub-Antarctic terrestrial ecosystems survive on isolated oceanic islands in the path of circumpolar currents and winds that have raged for more than 30 million years and are shaped by climatic cycles that surpass the tolerance limits of many species. Surprisingly little is known about how these ecosystems assembled their native terrestrial fauna and how such processes have changed over time. Here, we demonstrate the patterns and timing of colonization and speciation in the largest and dominant arthropod predators in the eastern sub-Antarctic: spiders of the genus Myro. Our results indicate that this lineage originated from Australia before the Plio-Pleistocenic glacial cycles and underwent an adaptive radiation on the Crozet archipelago, from where one native species colonized multiple remote archipelagos via the Antarctic circumpolar current across thousands of kilometers. The results indicate limited natural connectivity between terrestrial macroinvertebrate faunas in the eastern sub-Antarctic and partial survival of repeated glaciations in the Plio-Pleistocene. Furthermore, our findings highlight that by integrating arthropod taxa from multiple continents, the climatically more stable volcanic Crozet archipelago played a critical role in the evolution and distribution of arthropod life in the sub-Antarctic.

Long-term changes and seasonal variability in the stream macrofauna of a Himalayan river system

ABSTRACT Interpreting long-term variability in mountain stream ecosystems is challenging where potential causes such as climate change and altered land use act simultaneously. The scarcity of historical data also limits research opportunity, especially at low latitudes. Here we assess the macroinvertebrate fauna of 12 Himalayan streams in Nepal covering an altitudinal gradient from 1500 to 3900 m a.s.l. using data from 1992, 2022, and 2023. We aimed to (1) compare long-term change in richness and community composition over 3 decades to short-term seasonal variation, and (2) analyse long-term changes in relation to catchment properties. Rarefied richness decreased equally with altitude in 1992 and 2022 but was greater at most sites in 2022, with several new families detected. By contrast, no clear seasonal pattern was found. The 2022:1992 ratio in rarefied richness was positively correlated with catchment area and weakly with maximum catchment altitude, whereas the 2 highest and glaciated sites gained relatively more taxa than other sites. Non-metric multidimensional scaling (NMDS) ordinations from rarefied Bray-Curtis dissimilarities showed considerable overlap in communities among the 3 datasets. Pairwise rarefied dissimilarities among all sites increased significantly with altitudinal distance between sites in 1992, but no such relationship was detected in 2022. Dissimilarities between 1992 and 2022 samples showed a near-significant correlation with increased catchment vegetation cover, as shown by the normalized difference vegetation index (NDVI). Our study is the first to document long-term variations in stream macroinvertebrate communities in Himalayan mountain streams, illustrating how some altitudinal patterns have remained stable through time while others seem to have weakened with links to global change.

Demre Çayı (Antalya) Makrozoobentik Faunası

In this study, it was aimed to determine the benthic macroinvertebrate fauna of Demre Stream in Antalya. Benthic macroinvertebrate samples were taken seasonally from 12 stations determined on Demre Stream between April 2015 and December 2015 and the obtained individuals belonging to Clitellata, Rhabditophora, Gastropoda, Insecta, and Arachnida groups Macroinvertebrate based clustering of stations was calculated by using UPGMA analysis. The lowest similarity was determined between the 3rd and 10th stations, and the highest similarity was between the 8th and 11th stations. Simpson and Shannon-Wiener diversity indices were applied to determine the diversity values of the stations. According to both diversity indices, the highest diversity value was reached at the 5th station, while the lowest diversity value was reached at the 3rd station. This study is the first study to determine the benthic fauna of the Demre Stream and therefore all the groups identified are the first records for the Demre Stream.

Marine macroinvertebrate fauna of the shallow coastal waters of the Shiretoko Peninsula, a World Natural Heritage at Hokkaido, Japan

Marine macroinvertebrate fauna of the shallow coastal waters of the Shiretoko Peninsula, a World Natural Heritage at Hokkaido, Japan

Investigation of Benthic Macroinvertebrate Fauna and Water Quality of Animal Drinking Water Troughs by Multivariate Statistical Methods: The Case of Şarkışla

Investigation of Benthic Macroinvertebrate Fauna and Water Quality of Animal Drinking Water Troughs by Multivariate Statistical Methods: The Case of Şarkışla

Interactions between microplastics and Culex sp. larvae in wastewater.

Microplastics (MPs) are a growing issue because they endanger both aquatic organisms and humans. Studies have indicated that wastewater treatment plants (WWTPs) are one of the major contributors to MPs in the environment. However, studies on the abundance of MP contamination in WWTPs and its transmission into aquatic organisms are still scarce, especially in Egypt. The goal of this study was to examine the temporal fluctuations in the distribution of MPs in surface water and the dominant macroinvertebrate fauna (Culex sp. larvae) in a fixed wastewater basin in Sohag Governorate, Egypt. The average of MPs in the surface water was 3.01 ±0.9 particles/L. The results indicated to seasonal variation of MP abundance in the wastewater basin that was significantly higher in winter than in the other seasons. The risk index for polymers (H), pollution load index (PLI), and potential ecological risk index (RI) were used to assess the degree of MP contamination. The basin has moderate H values (<1000) because of the presence of polymers with moderate hazard scores such as polyester (PES), polyethylene (PE), and polypropylene (PP). According to the PLI values, surface water is extremely contaminated with MPs (PLI: 88 to 120). The RI values of surface water showed higher ecological risk (level V). MPs in Culex sp. larvae were seasonally changed with an 85% detection rate, and an abundance average of 0.24 ±0.65 particles/ind, MP concentration in Culex sp. larvae was influenced by the MP characters (shape, color, and polymer). The larvae of Culex sp. showed a greater preference for black and red fibrous polyester (PES) with sizes (<1000 μm) of MPs. These findings suggest that Culex sp. larvae prefer ingesting MPs that resemble their food. It is possible to overestimate Culex sp.'s preference for lower sizes because of their catabolism of MPs. To better understand the preferences of Culex sp. larvae for MPs, further controlled trials should be conducted. PRACTITIONER POINTS: Wastewater is highly contaminated with microplastics (MPs) in the different seasons. First report of detection of the seasonal abundance of MP in Culex sp. larvae. Culex sp. larvae showed a stronger feeding preference for MPs with specific characteristics. Smaller size and blue polyester fibers were the dominant characteristics of MPs in wastewater.

Biodiversidade de invertebrados associados a macroalgas na área marinha protegida do Arquipélago de Alcatrazes, sudeste do Brasil

Abstract This study describes and illustrates the biodiversity of macroinvertebrates associated to Sargassum and Dictyota seaweed habitats in the Alcatrazes archipelago, the largest Marine Protected Area (MPA) in the state of São Paulo, southeast Brazil. Assemblages were sampled during the summers of 2018, 2019 and 2020 and winter of 2018 at two sites on the main island. Macroalgae containing the associated fauna were collected at approximately 10 meters deep, with six samples at each site and in each sampling campaign. Sargassum fronds prevailed during summer collections, whilst were absent in the winter campaigns, when Dictyota was the most frequent seaweed. Among invertebrates, 32 species were exclusively found on summer months, associated to Sargassum beds, while 12 species were only registered on winter collection, in association with Dictyota. In total, 91 species were identified, belonging to 60 families, 19 orders, 7 classes and 3 phyla, including Arthropoda (Malacostraca and Pycnogonida), Mollusca (Gastropoda, Bivalvia and Polyplacophora), and Echinodermata (Ophiuroidea and Echinoidea). Among the 91 species found, 73 species are new records for the Alcatrazes archipelago marine area, thus revealing the expressive invertebrate biodiversity living in association with macroalgae beds in that area, which has still been little explored. No significant difference in species diversity was found between the two sites of Alcatrazes. In addition, few specimens of two invasive species were found: Perna perna (Mollusca: Bivalvia) and Ophiothela mirabilis (Echinodermata: Ophiuroidea), which underscores the importance of monitoring different habitats within MPAs to check for possible changes in the fauna over the years. As far as our knowledge, this is the first illustrated inventory of the seaweed-associated macroinvertebrate fauna within the Alcatrazes Archipelago, one of the largest MPAs in the Brazilian coast; besides unravelling its notorious biodiversity, this can act as a reference for future monitoring of local coastal diversity.

Comparative analysis of the Macroinvertebrate fauna of ecologically stable and traditional garden ponds

Freshwater habitats are considered to be highly vulnerable globally. For some species, mainly invertebrates, artificial ponds created in urban gardens give suitable habitat or function as stepping stones. However, traditional garden ponds use expensive pieces of equipment with high energy demand and might release harmful chemicals into their environment. In contrast, the ecologically stable garden ponds, which are distinguished from the traditional garden ponds by their design and the complex ecosystem that maintains them, offer a solution for the problems of eutrophication and succession and maintain optimal water quality in an environmentally and cost-effective way. This study aimed to compare the aquatic macroinvertebrate fauna diversity between traditional garden ponds and ecologically stable garden ponds designed and constructed by the first author. Five ponds of both types were examined, by collecting biological specimens from 90 sampling points. Altogether 42 species were identified, and one taxon at the genus level. Our statistical analysis indicates that the ecologically stable ponds host a much richer macroinvertebrate fauna in terms of species abundance compared to traditional garden ponds.

Benthic Macroinvertebrate Fauna of Some High Altitude Lakes on Bolkar Mountains

Bu çalışma, Bolkar Dağları üzerinde yer alan bazı yüksek irtifa göllerine ait (Yazıgöl, Yarıkgöl, Otlugöl, İsimsiz Göl, Eğrigöl ve Alagöl) bentik makroomurgasız faunasının belirlenmesi amacıyla Temmuz ve Ağustos 2019 tarihlerinde gerçekleştirilmiştir. Elde edilen makrobentik faunanın sistematik açıdan incelenmesi sonucunda sekiz takım (Diptera, Coleoptera, Trichoptera, Rhynchobdellida, Haplotaksida, Sphaeriida, Hygrophila ve Hemiptera) içerisinde sekiz familya ve 22 cinse mensup 23 tür tespit edilmiştir. Göllere ait tür çeşitliliği ve türler arasındaki yoğunluk ilişkilerinin belirlenebilmesi için Shannon-Wiener çeşitlilik (H) ve Shannon-Evenness yoğunluk (EH) indeksleri uygulanmış olup en yüksek çeşitlilik (H) 2,17 değeri ile Yarıkgöl’de gözlenirken bunu 1,94; 1,55; 1,08; 0,40 ve 0,38 değerleri ile sırasıyla Alagöl, Otlugöl, İsimsiz Göl, Yazıgöl ve Eğrigöl takip etmiştir. En dengeli dağılım (EH) ise Yarıkgöl ve İsimsiz Göl (0,73) olarak hesaplanırken bunu 0,59; 0,47; 0,25 ve 0,24 değerleri ile sırasıyla Otlugöl, Alagöl, Yazıgöl ve Eğrigöl izlemiştir. Belirlenen taksanın dağılımına göre en yüksek benzerlikler Otlugöl ve Yarıkgöl ile Eğrigöl ve İsimsiz Göl arasında tespit edilmiştir. En düşük benzerlikler ise İsimsiz Göl ve Yarıkgöl arasında hesaplanmıştır. Bu çalışma bölgedeki göller üzerinde yapılmış ilk çalışma niteliğinde olup göllerin makroomurgasız faunası oluşturulmuştur.

Assessing the Impact of Anthropic Pressures on Aquatic Macroinvertebrates: A Functional Trait Approach in the Irtysh River Watershed.

Little is known about how changes in the biodiversity and functional traits of macroinvertebrates in rivers respond to the responses of anthropic pressures and their driving factors. Macroinvertebrates were sampled at 17 sites in the Irtysh River Basin and classified macroinvertebrates into 10 traits and 38 categories between May and August 2022. Then, we performed R-mode linked to Q-mode (RLQ) analysis and calculated functional richness, evenness, divergence, and Rao's quadratic entropy (RaoQ) for each site and community-weighted means for each trait category. Our results indicated that there were pronounced alterations in species variability in the urban region. Functional divergence indicated fierce competition among species and considerable niche overlap in the urban region. Functional evenness indicated that species abundance distribution and interspecific functional distance were not uniform in the urban region. Functional richness indicated that the urban region was the strongest region in terms of niche occupation, resource utilization, and buffering capacity for environmental fluctuations. Rao's quadratic entropy showed that the trait difference of macroinvertebrates was the largest in all regions, which was caused by the gradient environmental difference. Research has revealed that urbanization significantly influences the evolutionary trajectory of macroinvertebrate fauna, culminating in an upsurge in pollution-tolerant species and a convergence of functional traits. We recommend strengthening the control of urban and industrial pollution and wise planning and management of land and water resources to mitigate the impact of anthropogenic destruction on habitat fragmentation in the Irtysh River Basin.

Using benthic macroinvertebrates as bioindicators to evaluate the impact of anthropogenic stressors on water quality and sediment properties of a West African lagoon

This study aimed to investigate the impact of anthropogenic stressors (landfilling, navigation for transport of goods, cooling in fossil fuel, urbanization, industrial expansion, agriculture activities, and recreational activities) on environmental variables, microbiological quality, and sediment properties using benthic macroinvertebrates as a bioindicator within Lagos Lagoon, Nigeria. Four (4) sampling stations were established with respect to their importance/anthropogenic activities within the Lagos Lagoon. Surface water, bottom substrates, and benthic macroinvertebrate fauna samples were collected bimonthly from each sampling station for a year and analyzed using appropriate standard methods and procedures. The highest pH range of 7.96–8.01 (7.98 ± 2.35) was recorded at Site IV, while the lowest range of 6.41–7.01 (6.15 ± 1.14) was observed at Site II, and there was a significant difference (p < 0.05) among the pH mean values across the sites. High values of salinity, chloride, sodium, COD, BOD, manganese, nickel, cadmium, and nitrate were recorded among the surface water physicochemical parameters, which were above WHO (2011) permissible limits, while the high concentrations of toxic metals (Pb, Cr, Zn, and Cd) was recorded in sediment. A total of 26 species of benthic macroinvertebrates were recorded during this study, which belongs to eight (8) classes. Gastropoda recorded the highest percentage contribution of 39.12%, followed by polychaeta accounting for 30.34%, while malacostraca contributed 2.63%. The highest abundance of macroinvertebrates was recorded at Site I (256 Indiv/m2), followed by Site IV (252 Indiv/m2), and the least was observed at Site II (195 Indiv/m2). Based on the results of the physico-chemical, heavy metals, microbial quality, and macroinvertebrates assemblage obtained from this study revealed the adverse effect of anthropogenic activities on water quality degradation. It plays a significant role in the distribution and diversity of benthic macroinvertebrates in an aquatic environment.

The Benthic Macroinvertebrates of the Kızılırmak River (Nevşehir, Turkey) and Their Relation with Environmental Variables

Turkey has many ecological characteristics due to its geographical location, allowing it to have a rich biodiversity in freshwater ecosystems. This study was carried out on the Kızılırmak river, the longest river (1.355 km) in the country; it originates and empties into the sea within its borders. The Kızılırmak river serves various agricultural, industrial, drinking water-related, and recreational purposes and greatly contributes to the region’s economy. This study aimed to determine the distribution of the river’s macroinvertebrate fauna and evaluate the impact of environmental variables on species distribution. In addition, using species-based biodiversity indices such as the Biological Monitoring Working Party (BMWP), Average Score per Taxon (ASPT), the Shannon–Wiener index, and evenness analysis, spatial and temporal similarities and differences were determined. According to the results, the ten taxonomic groups in the Kızılırmak river belong to the following categories: Gastropoda (81.5%), Gammaridae (9.8%), Oligochaeta (6.2%) Chironomidae (2.1%), Hirudinea (0.3%), and various others (0.1%). The Shannon–Wiener and evenness indexes were 0.29–1.9 and 0.46–0.14, respectively. TR-BMWP scores are in the poor to very poor water quality classes, and the ASPT ranges from moderate to poor water quality. Correlation analysis between species and physicochemical parameters indicated that the benthic macroinvertebrate fauna diversity of the river is affected by natural and anthropogenic factors.

Macrophyte- and Macrozoobenthic-Based Assessment in Rivers: Specificity of the Response to Combined Physico-Chemical Stressors

The importance of adequate biological assessments of rivers based on aquatic assemblages is essential to establish recovery measures. Macrophyte and macroinvertebrate communities react differently in time and in response strength to diverse stressors. Our hypothesis was that each group response is a result of specific and combined abiotic factors and each stressor’s impact. To address the above, both biological quality elements (BQEs) and values of the ecological quality ratio (EQR) were studied in relation to four abiotic parameters and five physico-chemical stressors. Discrepancies of more than one degree between the ecological status assessments of Bulgarian river sites determined using macrophytes and macrozoobenthos were discussed. The RDA analysis showed that altitude had a determining role in shaping the abundance of macrophyte and macrozoobenthos communities. Aquatic flora richness positively correlated with nitrogen enrichment and macroinvertebrate fauna—with altitude and biochemical oxygen demand (BOD). Nutrients and shading were most significant for the ecological status evaluation defined with both macrophytes and macrozoobenthos. Macrophyte-based EQR was related to oxygen concentration and shading, while macroinvertebrate-based EQR was better at sites with coarser substrates. Among tested stressors, mainly total nitrogen and BOD explained the lower macrophyte-based assessment at half of the studied sites. In conditions of increased nitrogen and BOD, but remaining in the range of good status, macrophytes as primary producers gave a faster and stronger response. Despite the differences in the assessment, both BQEs have higher values in conditions of lower BOD and total phosphorus.

HABITAT SELECTION OF Marmosops incanus (LUND, 1841) (DIDELPHIMORPHIA, DIDELPHIDAE) IN THE SERRA DOS ÓRGÃOS NATIONAL PARK, ATLANTIC FOREST, SOUTHEAST BRAZIL

Habitat selection is one of the mechanisms responsible for allowing species coexistence and, therefore, local richness of communities. This study investigates microhabitat selection by the opossum, Marmosops incanus, in a forested area in the Brazilian Atlantic Forest. We measured microhabitat variables related to vegetation structure and inferred M. incanus abundance as a measure of habitat use. Eight microhabitat variables were measured in each trap station: litter, herbaceous and woody stems, rock outcropping, canopy cover, foliar vertical obstruction at three heights (FOV), and number of fallen trunks. Based on a correlation matrix, we selected four microhabitat variables (litter, rock outcropping cover, FOV, and number of fallen trunks) and performed a Poisson regression using the selected variables and M. incanus abundance. Litter and rock outcropping cover were positively related to abundance, thus representing the habitat characteristics selected by the species. We infer that litter represents a source of food items, since it can support an abundant fauna of macroinvertebrates, especially arthropods. Rock outcroppings can be used as shelter and protection against predators. Other studies have recorded M. incanus using habitat in a unique way, either by changing the frequency of ground/understory use, or habitats with high/few herbaceous and litter cover, as the habitat varied from restinga to fragmented forests. Different habitat selection patterns were observed in areas where M. incanus and M. paulensis are sympatric, or Gracilinanus microtarsus, both of which have comparable size and ecology. We suppose the selection patterns recorded in this study are a result of the absence of a congener species in the study area. It may allow M. incanus to use more frequently areas where near-ground strata are clear and highly covered with litter. It remains to be evaluated if habitat simplification leads to behavior homogenization.