Eutrophic Environments Research Articles

Amphipods’ grazing and excretion loop facilitates Chara contraria persistence in a eutrophic lagoon

Charophyte stands represent valuable ecosystems threatened by eutrophication-related phytoplankton and epiphyte blooms. The mechanisms allowing the persistence of charophytes in eutrophic environments are important but poorly studied. We analyzed the benthic primary production and respiration, and inorganic nitrogen (N) fluxes in a Chara contraria stand within a eutrophic estuarine system (Curonian Lagoon) via light and dark intact core incubations. Rates were contrasted with those measured in adjacent unvegetated sediments. Additionally, O2 production was measured in fragments of C. contraria and in the associated community of epiphytes, whereas O2 respiration and ammonium (NH4+) excretion rates were measured in incubation of amphipods (Pontogammarus robustoides) alone. The results from core incubations suggest high primary production and respiration within charophyte stands, resulting in pronounced daily O2 variations in the overlaying water. The incubations of charophyte fragments and associated epiphytes indicate that the latter supports a major fraction of the benthic primary production. The large production of dinitrogen in the dark indicates the occurrence of denitrification, which is suppressed in the light due to primary producers-bacteria competition. On a daily basis, the charophyte stand was a sink for inorganic N via assimilative NH4+ uptake and a dark nitrate sink via denitrification. Interestingly, active NH4+ excretion by the abundant amphipods supported nearly 40 % of the N uptake by the primary producers. We speculate that amphipods continuously feed on epiphytes growing on charophytes, favouring C. contraria persistence and recycling large amounts of N via herbivory and excretion that are immediately re-used by benthic primary producers. This grazing, excretion and assimilation loop may represent an example of macrofauna-macrophyte mutual facilitation and a mechanism easing C. contraria competition under eutrophic conditions.

Toxic Microcystis aeruginosa alters the resource allocation in Daphnia mitsukuri responding to fish predation cues.

Many prey organisms adaptively respond to predation risk by inducible defenses with underlying tradeoffs in resource allocation. Cyanobacterial blooms expose zooplankton to poor food conditions, affecting the herbivores' fitness. Given the interferences on resources allocation and life history traits, poor-quality cyanobacteria are predicted to affect the adaptive predator-induced responses in zooplankton. Here, we exposed two clones (i.e., clones SH and ZJ) of the cladoceran Daphnia mitsukuri to different combinations of fish predation cues and diets containing toxic Microcystis aeruginosa (0%-30%). D.mitsukuri matured at a small size and had elongated relative tail spine as adaptive responses to fish cues. Despite the comparable tail spine defense, fish cue-induced changes in growth and reproduction in the clone SH were more pronounced than those in the clone ZJ under no M.aeruginosa. Animals accumulated microcystin in the whole body with increasing abundance of M.aeruginosa. However, the inducible enhanced tail spine allometry was not affected, resulting in unchanged tail spine defense by Daphnia under all M.aeruginosa treatments. By contrast, M.aeruginosa remarkably decreased the adaptive maturation size and the offspring number in all animals. However, the inducible reproductive effort tended to increase or remain unchanged depending on clones associated with the constant or decreased responses of the somatic growth effort under increasing M.aeruginosa. Our results suggested that toxic M.aeruginosa did not alter the resource allocation to antipredator morphological defense but affected the somatic growth and reproduction in D.mitsukuri under fish cues. The present study highlights the different effects of toxic cyanobacteria on adaptive predator-induced responses in zooplankton, promoting the understanding for the morphological defense-mediated predator-prey interactions in eutrophic environments.

Holocene regression of the critically endangered species Cladium mariscus (L.) Pohl on Žitný ostrov Island (site Mad, Danubian plain Lowland)

This study presents the palaeo-botanical record from the central part of Žitný Ostrov Island on the Danubian Lowland in Slovakia. The record spans almost the entire Holocene period and provides evidence that the wetland species Cladium mariscus (Cyperaceae) was present in this region as late as the Greenlandian period. In addition, the combination of C. mariscus and Carex elata beds were most likely an important part of the littoral zone vegetation during that period. Our investigations are based on plant macro-remain analysis, radiocarbon dating and physical sedimentary analysis of the former Danube side channel. The palaeo-channel infill active in the Late Pleistocene reflects complete hydroseral succession of a terrestrialised palaeo-lake. The earlier of two possible hiatuses in the fossil record was likely associated with a disturbance which caused Cladium mariscus to disappear from the local plant spectra. The most likely drivers of C. mariscus’ decline are a climate change of 8.6 cal ka BP associated with water fluctuations and the local habitat alteration to an eutrophic environment. These are discussed herein together with the isolated scattered populations surviving in the surrounding micro-region throughout the Meghalayan period. Finally, there are only two known remaining C. mariscus sites in the Žitný Ostrov Island area, and the key modern driving factor was the dramatic water regime changes in 19–20th Century caused by anthropogenic impact. These were caused by the construction of drainage canal systems and the transition from alluvial meadows to agricultural land.

Toxicity of the sawdust used for phosphorus recovery in a eutrophic reservoir: experiments with Lactuca sativa and Allium cepa.

Eutrophication is one of the environmental problems arising from the increase of essential nutrient concentrations, mainly phosphorus and nitrogen. In contrast to excess phosphorus, the depletion of phosphate rock deposits used for the production of fertilizers compromises the food supply. Therefore, the development of technologies that propose the recovery of the phosphorus contained in eutrophic environments for its later use for agricultural fertilization purposes is very important to ensure global food security. This work aimed to evaluate the toxic potential of the sawdust (biosorbent previously used for phosphorus adsorption) in order to enable its application in agriculture. For this, toxicity experiments with Lactuca sativa (lettuce) and Allium cepa (onion) seeds were performed. The phytotoxic potential was assessed by means of the seed germination index and physiological parameters such as radicle and hypocotyl growth. Cytotoxicity, genotoxicity, and mutagenicity tests were also performed on onion seeds. From statistical tests, it was possible to affirm that the sawdust did not promote inhibition of seed germination and radicle and hypocotyl growth. No genotoxicity, cytotoxicity and, mutagenicity were observed, which allowed to state that the sawdust is not toxic to the onion species, which reinforces the possibility of application of the biosorbent for soil fertilization purposes. Therefore, the use of sawdust for phosphorus biosorption with the subsequent agricultural application is promising and quite important from a global food security point of view.

Influence of the chlorophyll-a gradient on the community structure of plankton microcrustaceans (Cladocera and Copepoda) in a Neotropical reservoir.

Fish farming in net cages is considered as an alternative to food production in response to elevated population growth, and zooplankton is an important resource to the development of this economic activity. We (i) compared microcrustacean composition in eutrophic and oligotrophic habitats under net tank influence, (ii) investigated changes in species distributions in these habitats, and (iii) indicated which chlorophyll-a concentrations presented thresholds that alter community structure. We expected different responses of species to changes in chlorophyll-a concentration due to net cage management, as chlorophyll-a represents an estimate of food availability. Microcrustacean samplings and chlorophyll-a estimation were made upstream, downstream and close to the net cages, during 120 days, in the Rosana Reservoir (Brazil). Species composition differed significantly (p<0.05) among habitats where in the eutrophic environment was found the largest number of species. However, only in the eutrophic habitats did frequency of occurrence and relative abundance of some species change with chlorophyll-a variation. Thus, net cage management influenced species distribution only in the most productive habitat. These responses can affect ecosystem processes related to trophic dynamics as secondary productivity and nutrient cycling.

Phosphorus sorption potential of natural adsorbent materials from a Brazil semiarid region to control eutrophication

Abstract: Aim The aim of the present study was to evaluate the potential soluble reactive phosphorus (SRP) sorption of three natural P adsorbents (Luvisol, Planosol, and Scheelite tailing) from Brazil’s semiarid region. Methods The adsorption tests were done under pH 8 conditions with the natural adsorbents and Lanthanum-Modified Bentonite (LMB). The effect of humic substances on SRP sorption was also tested. For this, Luvisol and Planosol were incinerated to reduce their humic components, and new adsorption tests were done. The effect of adsorbents on water pH was also evaluated. Results The SRP sorption potential of the natural adsorbents was high at pH 8. Of the natural adsorbents, Luvisol achieved the highest maximum SRP adsorption capacity (Q) of 17.5 mg g-1, followed by Scheelite tailing (8.3 mg g-1) and Planosol (7.7 mg g-1). Scheelite tailing, Planosol and LMB increased the pH of the water. After treatment to reduce humic substances, Planosol showed a Q of 22.3 mg g-1 while Luvisol produced 11.1mg g-1. Reducing the amount of humic substances potentiated the sorption process in the Planosol. However, the isotherms of untreated Luvisol and treated Planosol have not reached equilibrium and therefore may be overestimated. Conclusions The precipitation process was probably the main sorption mechanism, being more expressive than adsorption. Scheelite tailing was the most promising material for eutrophic environments because it is alkaline, calcium-rich, and this capacity will probably remain high under anoxic conditions. It also has a small amount of organic matter and, consequently, contains less humic substances. The quality of the clay present in natural adsorbents was more important than quantity in the sorption process.

Spatio-temporal Variations in Bacterial Abundance with an Emphasis on Fecal Indicator Bacteria and Vibrio spp. in and around Visakhapatnam Port, East Coast of India

The ecological health of port environments, which are dynamic and hotspots of anthropogenic activities, can be analyzed using specific pathogenic bacteria as they provide definite evidence and source of pollution. The influence of seasons and environmental settings on total bacterial count (TBC), distribution of fecal indicators, and Vibrio spp. was explored in Visakhapatnam port, located along the east coast of India. South-west monsoon had a significant influence on TBC, fecal indicators, and Vibrio spp., and the abundance was influenced by the eutrophic environment in the inner harbour. Fecal indicators were one order higher in sub-surface water when compared with sediment, indicating their inoculation due to turbulent conditions in south-west monsoon. The abundance of V. cholerae was influenced by salinity, temperature, and SPM, and was positively correlated to plankton; relating their distribution with disease dynamics and ecosystem functioning is a step ahead. Such an assessment is important from the perspective of human health and marine bioinvasion.

Responses of Free-Living Vibrio Community to Seasonal Environmental Variation in a Subtropical Inland Bay.

Vibrio are widely distributed in aquatic environments and strongly associated with eutrophic environments and human health through the consumption of contaminated seafood. However, the response of the Vibrio community to seasonal variation in eutrophic environments is poorly understood. In this study, we used a Vibrio-specific 16S rRNA sequencing approach to reveal the seasonal distribution pattern and diversity of the Vibrio community in the Maowei Sea, Beibu Gulf of China. The Shannon diversity of the Vibrio community was highest in the summer, while β-diversity analysis showed that Vibrio community structures were significantly different between seasons. Distance-based redundancy analysis (dbRDA) and Mantel test analysis suggested that total dissolved nitrogen (TDN), total dissolved phosphorus (TDP), dissolved inorganic nitrogen (DIN), salinity, and temperature were the key environmental factors shaping the Vibrio community structure, indicating a strong filtering effect of trophic condition on Vibrio communities. Furthermore, through random forest analysis, V. fluvialis, V. alginolyticus, V. proteolyticus, V. splendidus, and the other eight Vibrio species were more sensitive to eutrophic changes. This study revealed seasonal changes in Vibrio communities and the influence of environmental variation on Vibrio community composition, contributing to a better understanding of their potential ecological roles in a subtropical inland bay.

Resilience of primary and export productivity in a eutrophic ecosystem following the Cretaceous-Paleogene mass extinction

The recovery time of marine productivity following the Cretaceous-Paleogene (KPg) mass extinction varies tremendously with location (hundreds to millions of years), with possible delays in the tropics as compared to higher latitudes. This heterogeneity is based on prevalent oligo- to mesotrophic marine environments. While highly productive eutrophic environments are less prevalent, they play a greater role in the carbon cycle. Here we present data from a eutrophic region within the tropical southern Tethys. Records of both organic matter and calcite production in this locality exhibit stability across the KPg boundary. In addition, our study points to a remarkably rapid recovery (<11 kyr), even possibly continuous high productivity across the KPg boundary, despite the tropical location. Moreover, the characteristic KPg δ13C negative excursion is observed in our locality, but is independent of high productivity, possibly indicating a reduction in the δ13C of the DIC of the ocean due to the input of light carbon from the atmosphere. Thus, this study provides new insight into the functioning of eutrophic ecosystems during environmental stress imposed by the ecological crisis.

T4-like myovirus community shaped by dispersal and deterministic processes in the South China Sea.

SummaryAs the most abundant and genetically diverse biological entities, viruses significantly influence ecological, biogeographical and evolutionary processes in the ocean. However, the biogeography of marine viruses and the drivers shaping viral community are unclear. Here, the biogeographic patterns of T4‐like viruses and the relative impacts of deterministic (environmental selection) and dispersal (spatial distance) processes were investigated in the northern South China Sea. The dominant viral operational taxonomic units were affiliated with previously defined Marine, Estuary, Lake and Paddy Groups. A clear viral biogeographic pattern was observed along the environmental gradient from the estuary to open sea. Marine Groups I and IV had a wide geographical distribution, whereas Marine Groups II, III and V were abundant in lower‐salinity continental or eutrophic environments. A significant distance‐decay pattern was noted for the T4‐like viral community, especially for those infecting cyanobacteria. Both deterministic and dispersal processes influenced viral community assembly, although environmental selection (e.g. temperature, salinity, bacterial abundance and community, etc.) had a greater impact than spatial distance. Network analysis confirmed the strong association between viral and bacterial community composition, and suggested a diverse ecological relationship (e.g. lysis, co‐infection or mutualistic) between and within viruses and their potential bacterial hosts.

Characteristics of Ammonia Oxidation in a Dielectric Barrier Discharge Reactor

At present, both the scale and intension for agricultural production are being largely developed, releasing a large amount of NH3 which causes people with malodor and health problems. In this article, the efficiency and products of ammonia removal in a dielectric barrier discharge reactor were studied experimentally, at different energy density, relative humidity, and ammonia concentration. The results show that the removal of ammonia increases with the increase of energy density, while the increase of NH3 concentration or humidity inhibits the ammonia removal. The conversion products of ammonia are mainly NO x and NH4NO3. More importantly, we found that under optimal conditions, nearly 80% of NH3 can be converted into NH4NO3. This discovery provides a new way for ammonia treatment and resource utilization in an eutrophic environment.

Bioerosion on Late Quaternary Planktonic Foraminifera Related to Paleoproductivity in the Western South Atlantic

AbstractPlanktonic Foraminifera are widely used in paleoceanographic reconstructions, although studies of their trophic interactions are still rare, especially those focusing on predation. Drilling holes are the most frequent traces of bioerosion in foraminifer tests, but environmental factors that control bioerosion are not yet understood. To determine if paleoceanographic variables are associated with bioerosion rates in late Quaternary planktonic foraminifers of the western South Atlantic, geochemical and assemblage analyses were made on a 46 kyr record from a piston core. An age model was constructed based on 10 AMS 14C dates. To reconstruct the paleoproductivity, δ13C, benthic/planktonic foraminifer and the relative abundances of Globigerina bulloides and Globigerinoides ruber (high and low productivity, respectively) were used. Bioeroded tests were counted and found in 21 of the 25 identified species, with frequencies ranging from 8.84% to 16.7%. Bioerosion was different in two groups identified by cluster analysis, with a higher intensity during glacial times, showing a strong correlation with paleoceanographic fluctuations. Paleoproductivity estimates and bioerosion rates show a significant correlation, suggesting that bioerosion is more frequent in eutrophic environments and more inhibited in oligotrophic conditions. However, even with a strong correlation between bioerosion and productivity, there is also a negative correlation with sea surface temperature in the study area. Since conditions that promote higher productivity are accompanied by a decrease in surface temperature, the precise distinction between the influence of both variables is hampered. Further research will allow us to explore the potential of planktonic foraminiferal bioerosion as a tool in paleoceanographic studies.

Lagoon Resident Fish Species of Conservation Interest According to the Habitat Directive (92/43/CEE): A Review on Their Potential Use as Ecological Indicator Species

Transitional waters are fragile ecosystems with high ecological, social and economic values, that undergo numerous threats. According to the information provided by European Member States in the framework of the European Directive 92/43/EEC (Habitat Directive), the main threat to these ecosystems is represented by morphological and hydrological changes. The present work focuses on six lagoon fish species included in the Habitat Directive annex II (species requiring conservation measures: Aphanius fasciatus, A. iberus, Knipowitschia panizzae, Ninnigobius canestrinii, Valencia hispanica and V. letourneuxi) that spend their entire life cycle in the Mediterranean priority habitat 1150* “Coastal lagoons”. The overview of the current scientific literature allowed us to highlight how the presence and abundance of these species may provide important indications on the conservation status of coastal lagoon habitats. In fact, their occurrence, distribution and biology depend on the presence of peculiar structures, such as salt marshes, small channels, isolated pools and oligohaline areas. Coastal lagoon fragmentation and habitat loss have led to a significant reduction in genetic diversity or local population extinction. Although Aphanius and gobies have been shown to survive in eutrophic environments, it is clear that they cannot complete their life cycle without salt marshes (mainly Aphanius) and wetland areas (mainly gobies).

Eelgrass-associated mesograzers limit the distribution of bloom-forming Ulva via top-down control of its early life stages

Macroalgal blooms pose a threat to coastal ecosystems worldwide, especially in highly eutrophic environments. Excess nutrients often facilitate the proliferation of opportunistic algae, but in some systems grazing activity counterbalances its effects. I evaluated the regulating role of mesograzers associated with eelgrass (Zostera marina) in Elkhorn Slough, a eutrophic estuary where Ulva spp. blooms are frequent during the upwelling season. I monitored recruitment and transplant success of Ulva spp. along transects placed across the edge of the largest Z. marina bed. Changes in abundance of Ulva spp. on transplants differed spatially and seasonally, and were significantly correlated with density of both small and large invertebrate groups. Grazing affected not only adult Ulva spp. but also its early developmental stages, leading to decreased Ulva spp. abundance on transplants and minimal recruitment inside the Z. marina bed.

Water security and detection of Cryptosporidium spp. in samples from the Guarapiranga Reservoir, São Paulo

Water security depends, among other factors, on the hydrological cycle, quantity and quality of water. Several microorganisms that pose risks to human and animal health are waterborne, such as the protozoan Cryptosporidium spp. The parasitological diagnosis of Cryptosporidium spp. in biological material and environmental samples can be accomplished through several techniques that include optical microscopy with analysis of fresh material or through the use of concentration techniques, indirect immunofluorescence and molecular biology that allows differentiation between species. Oocysts of Cryptosporidium spp. are eliminated through feces from parasitized hosts and released into drinking water reservoirs through untreated sewage. Therefore, its proper identification is necessary when causing human gastrointestinal changes. The objective of this work is to analyze the presence of oocysts of Cryptosporidium spp. in recreational areas of the Guarapiranga Resevoir located in the state of São Paulo, Brazil. Water samples were collected and concentrated between July and November and analyzed through the technique of Ziehl Neelsen. Samples showed positive results for Cryptosporidium spp. and cyanobacteria, which are commonly found in the aquatic biota. The latter can be found in large quantities in eutrophic environments due to high amount of organic matter released in water bodies. Oocysts were observed in 60% of the analyzed samples and the distribution between positive and negative samples was not dependent on the month of sampling, but showed statistically significant differences according to the sampling site.

Pilot-scale study on the effects of cyanobacterial blooms on Vallisneria natans and biofilms at different phosphorus concentrations

Cyanobacterial blooms cause potential risk to submerged macrophytes and biofilms in eutrophic environments. This pilot-scale study investigated the growth, oxidative responses, and detoxification activity of aquatic plants in response to cyanobacterial blooms under different phosphorus concentrations. Variations of extracellular polymeric substances (EPSs) and microbial community composition were also assessed. Results showed that the biomass of Vallisneria natans increased with exposure to cyanobacterial blooms at higher phosphorous concentrations (P > 0.2 mg L−1). The amount of microcystin compounds (MC-LR) released into the water and the accumulation of MC-LR into both plant tissue and biofilms changed according to the phosphorus concentration. Furthermore, a certain degree of oxidative stress was induced in the plants, as evidenced by increased activity of superoxide dismutase, catalase, and peroxidase, as well as increased malondialdehyde concentrations; significant differences were also seen in acid phosphatase and glutathione S-transferase activities, as well as in glutathione concentrations. Together, these responses indicate potential mechanisms of MC-LR detoxification. Broader α-D-glucopyranose polysaccharides (PS) increased with increasing phosphorous and aggregated into clusters in biofilm EPS in response to the cyanobacterial blooms. In addition, alterations were seen in the abundance and structure of the microbial communities present in exposed biofilms. These results demonstrate that cyanobacterial blooms under different concentrations of phosphorus can induce differential responses, which can have a significant impact on aquatic ecosystems.

Bioremediation of Ammonium and Phosphates and their Effect on the Macroalgae Dictyota dichotoma (Hudson) Lamouroux Native to the Red Sea Coast, Egypt

IN LABORATORY experiments for eleven days, the effect of dissolved ammonium and phosphate on the absorption, growth, and nutritional content of Dictyota dichotoma was examined to determine their potential application as a nutrient biofilter. Five combinations of phosphates and ammonium concentration (0.8/8, 2/20, 4/40, 6/60, and 8/80μmol/L) were added to Sterile seawater. Molar phosphorus/ nitrogen ratio was 1:10. Over a 24hrs period, 69.2–99.9% of the available ammonium and 90.7–100% of the available phosphate were taken up by D. dichotoma. The highest specific growth rate was 9.3± 0.2% day-1 at 6/60μmol/L while the lowest was 5.11± 0.3% day-1 at 0μmol/L. On the other hand at 8/80μmol/L the biomass was decreased in the second day of treatment. Total soluble carbohydrate, total soluble protein, and total lipids of the tested D. dichotoma were significantly increased with the increase of PO4-3/NH4+ concentration and greater than their respective initial content. The highest averages of total soluble carbohydrate (TSC) (9.79± 0.45% dry wt.), total soluble protein (TSP) (16.3± 0.32% dry wt.) and total lipid (8± 0.30% dry wt.) were observed at the concentration of 6μmol/L for PO4-3 and 60μmol/L for NH4+. Based on these results, D. dichotoma has a strong absorption capacity for ammonium & phosphates, and as bioremediator in eutrophic environments can be a promising applicant.

Exploring the role of spatial and stoichiometric heterogeneity in the top-down control in eutrophic planktonic ecosystems

Understanding the impact of eutrophication on the dynamics of aquatic food webs, remains a long-term challenge in ecology. Mathematical models generally predict the destabilisation of such webs, under increasing eutrophication levels, with large oscillations of species densities that can result in their extinction. This is at odds with a number of ecological observations that show stable dynamics even for high nutrient loads. The apparent discrepancy between theory and observations is known as the Rosenzweig’s ‘paradox of enrichment’ and various solutions to the problem have been proposed over the years. In this study, we explore the stabilisation of dynamics of a tri-trophic plankton model in a eutrophic environment which occurs as a result of interplay of space heterogeneity, ecological stoichiometry, and food taxis of predators. We build a variety of models of increasing complexity, to explore various scenarios of phytoplankton growth, zooplankton food-dependent vertical movement, and different stoichiometric limitations of zooplankton. We show that the synergy among the vertical gradient in phytoplankton growth, phytoplankton structuring in terms of their stoichiometric ratio, and food-dependent vertical movement of zooplankton, would result in a postponing of destabilisation of eutrophic systems as compared to a well-mixed system. Our approach reveals a high complexity of the bifurcation structure of the system when key model parameters, such as the degree of eutrophication and light shading, are varied. We find coexistence of limit cycles and stable equilibria and that the possibility of multiple attractors in the system can result in hysteresis phenomena when the nutrient load is manipulated. These results are relevant and should be taken into account in lake restoration programs.

Autecology of Cylindrospermopsis raciborskii (Woloszynska) Seenayya et Subba Raju

Abstract: Aim Cylindrospermopsis raciborskii (Woloszynska) Seenayya and Subba Raju, also called Raphidiopsis raciborskii, is a diazotrophic and filamentous cyanobacterium with terminal heterocytes, belonging to the order Nostocales. It has been the focus of several studies due to its toxicity and wide geographic distribution. Methods To understand its autecology and to identify the key factors that control its dominance, the present review discusses, based on recent publications, whether the expansion of this species is a result of a high metabolic plasticity or the existence of distinct ecotypes. Results Among the factors influencing C. raciborskii growth are its ability to survive in wide temperature, light intensity and pH ranges; to dominate in both stratified and mixed environments; to tolerate oligohaline conditions; to produce and secrete allelopathic substances; suffer little herbivore pressure; and although associated with a eutrophic environment, to tolerate low concentration of phosphorus and nitrogen with a high affinity for ammonia. Conclusions Due to these differences in the environmental conditions of growth and development found in various studies, we suggest the existence of different ecotypes that will predominate under specific environmental conditions as the most appropriate hypothesis.

Campsurus truncatus Ulmer, 1920 (Polymitarcyidae): an Ephemeroptera in eutrophic waters

Abstract: Aim The order Ephemeroptera, together with Trichoptera and Plecoptera, has been considered as sensitive in environmental quality assessment. However, the species Campsurus truncatus Ulmer 1920 (Polymitarcyidae) has been sampled in anthropically altered sites. In this paper, data on the occurrence of that species in the water quality monitoring network of the Environmental Agency of São Paulo State (CETESB) were gathered to review its position in the environmental gradient and in the quality assessment of rivers and reservoirs. Methods For this, a compilation of the occurrences and densities of Campsurus obtained in rivers and reservoirs of São Paulo state between 2001 and 2018, with grab samplers, was carried. Environmental factors, the Trophic State Index (TSI) and the Benthic Community Index (BCI) were related to the species densities to define its environmental requirements. Results The sublittoral zone of reservoirs was the most common habitat to C. truncatus, occurring more frequently at mesotrophic sites with fair ecological quality. Higher mean densities were recorded at eutrophic sites with good ecological quality conditions. The statistical analysis did not show linear correlation between C. truncatus densities and any of the analyzed environmental variable such as grain size, organic matter content, DO and light penetration, although there was a tendency for higher species densities occur in muddy, dark sediments and with intermediate levels of organic matter. As described in literature the presence of aquatic plants can actually benefit that population once the highest densities were observed in sites with many macrophytes, as Salto Grande reservoir, but it may be confusing the relationship between population density and environmental factors. Conclusions The high occurrence and densities of C. truncatus obtained in eutrophic environments suggest that the species should not be considered as a sensitive taxon in qualitative indexes, such as the BCI for rivers and the sublittoral region of reservoirs. Moreover, its exclusion from the richness of sensitive groups had low impact on the diagnoses already performed at the CETESB monitoring network.