Topography-based modulation of environmental factors as a mechanism for intertidal microhabitat formation: A basis for marine ecological design.

Topographic complexity is often considered to be closely associated with habitat complexity and niche diversity; however, complex topography per se does not imply habitat suitability. Rather, ecologically suitable habitats may emerge if topographic features interact with environmental factors and thereby alter their surrounding microenvironment to the benefit of local organisms (e.g., resource provisioning, stress mitigation). Topography may thus act as a key modulator of abiotic stressors and biotic pressures, particularly in environmentally challenging intertidal systems. Here, we review how topography can alter microhabitat conditions with respect to four resources required by intertidal organisms: a source of energy (light, suspended food particles, prey, detritus), water (hydration, buffering of light, temperature and hydrodynamics), shelter (temperature, wave exposure, predation), and habitat space (substratum area, propagule settlement, movement). We synthesize mechanisms and quantitative findings of how environmental factors can be altered through topography and suggest an organism-centered 'form-follows-ecological-function' approach to designing multifunctional marine infrastructure.

Photoreceptor genes in a trechine beetle, Trechiama kuznetsovi, living in the upper hypogean zone.

To address how organisms adapt to a new environment, subterranean organisms whose ancestors colonized subterranean habitats from surface habitats have been studied. Photoreception abilities have been shown to have degenerated in organisms living in caves and calcrete aquifers. Meanwhile, the organisms living in a shallow subterranean environment, which are inferred to reflect an intermediate stage in an evolutionary pathway to colonization of a deeper subterranean environment, have not been studied well. In the present study, we examined the photoreception ability in a trechine beetle, Trechiama kuznetsovi, which inhabits the upper hypogean zone and has a vestigial compound eye. By de novo assembly of genome and transcript sequences, we were able to identify photoreceptor genes and phototransduction genes. Specifically, we focused on opsin genes, where one long wavelength opsin gene and one ultraviolet opsin gene were identified. The encoded amino acid sequences had neither a premature stop codon nor a frameshift mutation, and appeared to be subject to purifying selection. Subsequently, we examined the internal structure of the compound eye and nerve tissue in the adult head, and found potential photoreceptor cells in the compound eye and nerve bundle connected to the brain. The present findings suggest that T. kuznetsovi has retained the ability of photoreception. This species represents a transitional stage of vision, in which the compound eye regresses, but it may retain the ability of photoreception using the vestigial eye.

Hydroxycamptothecin and Substratum Stiffness Synergistically Regulate Fibrosis of Human Corneal Fibroblasts.

Corneal fibrosis is a common outcome of inappropriate repair associated with trauma or ocular infection. Altered biomechanical properties with increased corneal stiffness is a feature of fibrosis that cause corneal opacities, resulting in severe visual impairment and even blindness. The present study aims to determine the effect of hydroxycamptothecin (HCPT) and matrix stiffness on transforming growth factor-ß1 (TGF-ß1)-induced fibrotic processes in human corneal fibroblasts (HTK cells). HTK cells were cultured on substrates with different stiffnesses ("soft", ∼261 kPa; "stiff", ∼2.5 × 103 kPa) and on tissue culture plastic (TCP, ∼106 kPa) and simultaneously treated with or without 1 µg/mL HCPT and 10 ng/mL TGF-ß1. We found that HCPT induced decreased cell viability and antiproliferative effects on HTK cells. TGF-ß1-induced expression of fibrosis-related genes (FN1, ACTA2) was reduced if the cells were simultaneously treated with HCPT. Substrate stiffness did not affect the expression of fibrosis-related genes. The TGF-ß1 induced expression of FN1 on both soft and stiff substrates was reduced if cells were simultaneously treated with HCPT. However, this trend was not seen for ACTA2, i.e., the TGF-ß1 induced expression of ACTA2 was not reduced by simultaneous treatment of HCPT in either soft or stiff substrate. Instead, HCPT treatment in the presence of TGF-ß1 resulted in increased gene expression of keratocyte phenotype makers (LUM, KERA, AQP1, CHTS6) on both substrate stiffnesses. In addition, the protein expression of keratocyte phenotype makers LUM and ALDH3 was increased in HTK cells simultaneously treated with TGF-ß1 and HCPT on stiff substrate as compared to control, i.e., without HCPT. In conclusion, we found that HCPT can reduce TGF-ß1-induced fibrosis and promote the keratocyte phenotype in a substrate stiffness dependent manner. Thus, HCPT stimulation might be an approach to stimulate keratocytes in the appropriate healing stage to avoid or reverse fibrosis and achieve more optimal corneal wound healing.

Colonization dynamics in body-size spectrum of protozoan periphytons for marine bioassessment using two modified sampling systems.

The body-size spectrum of microperiphytons has been proved to be a powerful tool for bioassessment. To explore colonization dynamics in body-size spectrum of periphytic protozoa in two modified sampling systems of both glass slide (mGS) and polyurethane foam unit (mPFU), a 28-day colonization survey was conducted in coastal waters of the Yellow Sea, China. A total of 7 body-size ranks were identified from 62 species, with 7 ranks (60 species) in the mGS and 6 ranks (37 species) in the mPFU system. The stable pattern with similar body-size spectra was found earlier in the mGS system than mPFU system during the colonization period. Both the trajectory and bootstrapped average analyses revealed that the colonization dynamics were significantly different in the body-size spectrum between the two methods. Based on our data, it suggests that the mGS system might be a better choice than the mPFU system for bioassessment in marine ecosystems.

Collembola from Two Samplings in the MSS of the Sierra de Guadarrama National Park in Two Different Seasons, with Description of a New Species.

An intensive sampling in a colluvial mesovoid shallow substratum (MSS) of the Sierra de Guadarrama National Park, using 33 subterranean sampling devices (SSDs) is the origin of the Collembola studied in this paper. The data were obtained from the second extraction of the traps, in operation between October of 2015 and May of 2016. This paper presents the faunistic and diversity data along with the entire park (mostly at sampling points above 200 m a.s.l.) for this period, compares the data between the first extraction of the traps and the second one, and describes one species of the genus Pseudosinella that appears as new in the second campaign.

Seascapes and foraging success: Movement and resource discovery by a benthic marine herbivore.

Spatially concentrated resources result in patch-based foraging, wherein the detection and choice of patches as well as the process of locating and exploiting resource patches involve moving through an explicit landscape composed of both resources and barriers to movement. An understanding of behavioral responses to resources and barriers is key to interpreting observed ecological patterns. We examined the process of resource discovery in the context of a heterogeneous seascape using sea urchins and drift kelp in urchin barrens as a model system. Under field conditions, we manipulated both the presence of a highly valuable resource (drift kelp) and a barrier to movement (sandy substratum) to test the interacting influence of these two factors on the process of resource discovery in barren grounds by urchins. We removed all foraging urchins (Strongylocentrotus droebachiensis) from replicate areas and monitored urchin recolonization and kelp consumption. We tested two hypotheses: (1) unstable substratum is a barrier to urchin movement and (2) the movement behavior of sea urchins is modified by the presence of drift kelp. Very few urchins were found on sand, sand was a permeable barrier to urchin movement, and the permeability of this barrier varied between sites. In general, partial recolonization occurred strikingly rapidly, but sand slowed the consumption of drift kelp by limiting the number of urchins. Differences in the permeability of sand barriers between sites could be driven by differences in the size structure of urchin populations, indicating size-specific environmental effects on foraging behavior. We demonstrate the influence of patchy seascapes in modulating grazing intensity in barren grounds through modifications of foraging behavior. Behavioral processes modified by environmental barriers play an important role in determining grazing pressure, the existence of refuges for new algal recruits, and ultimately the dynamics of urchin-algal interactions in barren grounds.

Adhesion of Dictyostelium Amoebae to Surfaces: A Brief History of Attachments.

Dictyostelium amoebae adhere to extracellular material using similar mechanisms to metazoan cells. Notably, the cellular anchorage loci in Amoebozoa and Metazoa are both arranged in the form of discrete spots and incorporate a similar repertoire of intracellular proteins assembled into multicomponent complexes located on the inner side of the plasma membrane. Surprisingly, however, Dictyostelium lacks integrins, the canonical transmembrane heterodimeric receptors that dominantly mediate adhesion of cells to the extracellular matrix in multicellular animals. In this review article, we summarize the current knowledge about the cell-substratum adhesion in Dictyostelium, present an inventory of the involved proteins, and draw parallels with the situation in animal cells. The emerging picture indicates that, while retaining the basic molecular architecture common to their animal relatives, the adhesion complexes in free-living amoeboid cells have evolved to enable less specific interactions with diverse materials encountered in their natural habitat in the deciduous forest soil. Dissection of molecular mechanisms that underlay short lifetime of the cell-substratum attachments and high turnover rate of the adhesion complexes in Dictyostelium should provide insight into a similarly modified adhesion phenotype that accompanies the mesenchymal-amoeboid transition in tumor metastasis.

Spatiotemporal Distribution of Asian Horseshoe Crab Eggs Are Highly Intermingled with Anthropogenic Structures in Northern Beibu Gulf, China.

Identification, protection and restoration of spawning habitats are vital for protecting the depleted species. Asian horseshoe crabs are ecologically important macroinvertebrates in coastal and estuarine ecosystems. However, their spawning habitat studies were limited to several reports in tropical regions, possibly due to the lack of modified survey methods, particularly in habitats with a lower density of spawning adults, and/or intermingled with anthropogenic structures. In this study, the year-round egg distribution and spawning habitat baselines of Carcinoscorpius rotundicauda and Tachypleus tridentatus were determined in the northern Beibu Gulf, China. Our findings demonstrated that the peak spawning occurred in June-July and ceased in November-January when the average water temperature dropped below 20 °C. Egg aggregations were found < 10 cm beneath the sediment surface with regular tidal inundation, regardless of seasonal changes, in the vicinity of natural and artificial structures with elevated, mildly sloping substratum within the high tide zones. The nests were characterized by medium-sized sediment grains (0.5-0.9 mm), high temperatures (31-34°C), low water contents (0.8%-0.9%), and total organic carbon contents (0.5%-0.7%), which might maximize the hatching success. The identified nesting beaches were close to nursery habitats for juveniles, and tidal creeks were present as the possible corridor connecting these two important habitats through the dominant mangrove forests. The findings provide valuable insights in the scope of spawning behavior and nest-site selection of Asian horseshoe crabs under a mixture of natural and artificial structures, which could benefit future management efforts for the exploited spawning populations.

Physiology of microalgal biofilm: a review on prediction of adhesion on substrates.

In view of high energy cost and water consumption in microalgae cultivation, microalgal-biofilm-based cultivation system has been advocated as a solution toward a more sustainable and resource friendlier system for microalgal biomass production. Algal-derived extracellular polymeric substances (EPS) form cohesive network to interconnect the cells and substrates; however, their interactions within the biofilm are poorly understood. This scenario impedes the biofilm process development toward resource recovery. Herein, this review elucidates on various biofilm cultivation modes and contribution of EPS toward biofilm adhesion. Immobilized microalgae can be envisioned by the colloid interactions in terms of a balance of both dispersive and polar interactions among three interfaces (cells, mediums and substrates). Last portion of this review is dedicated to the future perspectives and challenges on the EPS; with regard to the biopolymers extraction, biopolymers' functional description and cross-referencing between model biofilms and full-scale biofilm systems are evaluated. This review will serve as an informative reference for readers having interest in microalgal biofilm phenomenon by incorporating the three main players in attached cultivation systems: microalgae, EPS and supporting materials. The ability to mass produce these miniature cellular biochemical factories via immobilized biofilm technology will lay the groundwork for a more sustainable and feasible production.

Importance of substratum quality for potential competitive niche overlap between native and invasive unionid mussels in Europe.

Infaunal freshwater mussels are highly threatened and declining worldwide. One of the potential threats to mussels consists of biological invasions. We intended to investigate the habitat overlap and behavioural differences between native (Unio pictorum, Unio tumidus, Anodonta anatina, Anodonta cygnea) and invasive (Asian Sinanodonta woodiana) unionid bivalves to determine potential sources of competition. Furthermore, we investigated differences between S. woodiana from the established population in artificially heated waters and from the recent population in a natural thermal regime. We used pairwise choice tests on mud, medium, coarse and very coarse sand, mixture of medium and coarse sand, fine, medium and coarse gravel, and observed mussel locomotion and burrowing in preferred and non-preferred substrata. All species generally preferred fine-grained materials. The widest preference range was exhibited by S. woodiana (both populations), whereas A. cygnea was the most selective. The preferences of the cold-water population of S. woodiana were shifted towards coarser materials compared to conspecifics from the heated waters, and highly overlapped with the preferences of the native species. Anodonta cygnea most often moved horizontally and spent the shortest time deeply burrowed. Both Unio species were deeply burrowed for the largest amount of time and the horizontal locomotion of U. tumidus was the lowest among the test species. Sinanodonta woodiana, especially from the heated water population, exhibited relatively weak locomotion (compared to A. cygnea) and burrowing (compared to Unio spp. and A. anatina). Deep burrowing was more common on fine-grained materials. Our results suggest that the native mussels can be threatened by S. woodiana due to their overlapping habitat preferences, potentially hindering habitat separation. However, mobile native mussels may be capable of migrating and avoiding competition. Accumulating knowledge of the biology and ecology of freshwater mussels could contribute to the creation and improvement of conservation plans to protect these threatened animals.

Temporal and spatial dynamics of arthropod groups in terrestrial subsurface habitats in central Portugal.

The mesovoid shallow substratum (MSS) can act as a climatic refuge for invertebrates, as a biogeographic corridor to deeper substrates or as a permanent habitat for some species. This study characterizes the seasonal invertebrate diversity and abundance of MSS ecosystems in central Portugal focusing on Diplopoda, Diplura, Orthoptera and Coleoptera during one year. Sampling was performed with standard MSS pitfalls in scree slopes (colluvial MSS) of karst areas and environmental parameters (temperature, pH, conductivity, water content, organic carbon, nitrate, phosphate and ammonium) were quantified. Our results show that winter was the season with the highest arthropod abundance and that the MSS acts as a permanent habitat for chordeumatidan millipedes and as a climatic refuge for orthopterans and most beetles. All Diplura collected belong to a single species known previously from surface habitats in the Iberian Peninsula, which does not seem to use the Portuguese MSS as a refuge. MSS habitats in central Portugal, classified as western Mediterranean and thermophile deposits protected by the Natura 2000 network based on plant communities and geology, revealed an abundant and diverse invertebrate community that urges characterization and protection.

Build Your Own Mushroom Soil: Microbiota Succession and Nutritional Accumulation in Semi-Synthetic Substratum Drive the Fructification of a Soil-Saprotrophic Morel.

Black morel, a widely prized culinary delicacy, was once an uncultivable soil-saprotrophic ascomycete mushroom that can now be cultivated routinely in farmland soils. It acquires carbon nutrients from an aboveground nutritional supplementation, while it remains unknown how the morel mycelium together with associated microbiota in the substratum metabolizes and accumulates specific nutrients to support the fructification. In this study, a semi-synthetic substratum of quartz particles mixed with compost was used as a replacement and mimic of the soil. Two types of composts (C1 and C2) were used, respectively, plus a bare-quartz substratum (NC) as a blank reference. Microbiota succession, substrate transformation as well as the activity level of key enzymes were compared between the three types of substrata that produced quite divergent yields of morel fruiting bodies. The C1 substratum, with the highest yield, possessed higher abundances of Actinobacteria and Chloroflexi. In comparison with C2 and NC, the microbiota in C1 could limit over-expansion of microorganisms harboring N-fixing genes, such as Cyanobacteria, during the fructification period. Driven by the microbiota, the C1 substratum had advantages in accumulating lipids to supply morel fructification and maintaining appropriate forms of nitrogenous substances. Our findings contribute to an increasingly detailed portrait of microbial ecological mechanisms triggering morel fructification.

Neelipleona and Symphypleona (Collembola) from a Sampling in the Mesovoid Shallow Substratum of the Sierra de Guadarrama National Park (Madrid and Segovia, Spain): Taxonomy and Biogeography.

Megalothorax minimus (Neelidae) and Sphaeridia pumilis (Sminthurididae) had already been identified in surface sampling from Sierra de Guadarrama. In Europe, Sminthurinus gisini (Katiannidae) seems to be associated with environments at specific altitudes, and has little representation in this sampling. Pygmarrhopalites custodum Baquero and Jordana sp. nov. (Arrhopalitidae) coexists with two previously identified surface occurring species of the same family (P. elegans and Arrhopalites caecus). However, P. custodum is more abundant, indicating that it occupies an ecological niche tending to troglophile in the mesovoid shallow substratum (MSS). Moreover, it is also more abundant in the MSS of higher altitude corresponding to the bioclimatic zones cryo-oro-Mediterranean and oro-Mediterranean supra forest. Allacma cryptica Baquero and Jordana sp. nov. (Sminthuridae), is another species that had not been previously detected on the surface in the study area. A. cryptica is an addition to a genus which has eight described species. Gisinurus malatestai (Sminthuridae) appears well represented in the MSS, being a species present very occasionally in the Mediterranean area. Two species of the genera Sminthurides (Sminthurididae) and Fasciosminthurus (Bourletiellidae) have been found, but they could not have been identified to the species level. Finally, a few specimens of Dicyrtomina minuta (Dicyrtomidae), an abundant species on the surface, have been captured.

All Shades of Shrimp: Preferences of Colour Morphs of a Freshwater Shrimp Neocaridina davidi (Decapoda, Atyidae) for Substrata of Different Colouration.

An ornamental freshwater shrimp, Neocaridina davidi, is popular as an aquarium hobby and, therefore, a potentially invasive species. There is a growing need for proper management of this species to determine not only their optimum breeding conditions, but also their ability to colonise novel environments. We tested habitat preferences of colour morphs (brown, red, white) of N. davidi for substratum colour (black, white, grey shades, red) and fine or coarse chess-board patterns to recognise their suitable captivity conditions and predict their distribution after potential release into nature. We conducted laboratory choice experiments (n = 8) with three individuals of the same morph exposed for two hours to a range of backgrounds. Shrimp preferred dark backgrounds over light ones irrespective of their own colouration and its match with the background colour. Moreover, the brown and red morphs, in contrast to the white morph, preferred the coarse background pattern over the finer pattern. This suggests that the presence of dark, uniform substrata (e.g., rocks, macrophytes) will favour N. davidi. Nevertheless, the polymorphism of the species has little effect on its total niche breadth, and thus its invasive potential.

Distribution of testate amoebae in bryophyte communities in São Miguel Island (Azores Archipelago).

BACKGROUND: Testate amoebae are a polyphyletic group of protists living preferentially in soils, freshwaters and wetlands. These Protozoa have a worldwide distribution, but their presence and diversity in the Azores (a remote oceanic archipelago) is poorly known, with only twelve taxa recorded so far. The published information reflects occasional collections from sporadic field visits from naturalists to São Miguel Island, mainly in the nineteenth century. To overcome this limitation, a standardised survey was carried out on the Island, sampling different types of habitats from several localities to provide the distribution and information on species ecology of testate amoebae. NEW INFORMATION: In this study, 43 species of testate amoebae were recorded (within a total of 499 occurrences), belonging to two orders of Protista (26 Arcellinida and 17 Euglyphida). The most frequently occurring testate amoebae were Euglypha strigosa, Trinema lineare, Euglypha rotunda, Assulina muscorum and Cyclopyxis eurystoma. The most diverse genus was Euglypha (six species). A total of 38 species are new records for the Azores Archipelago. These data help to improve knowledge of the geographical distribution of testate amoebae in the northern hemisphere and their diversity in the Azores Archipelago.

Substratum influences uptake of radium-226 by plants.

Radium-226, an alpha emitter with half-life 1600 years, is ubiquitous in natural environments. Present in rocks and soils, it is also absorbed by vegetation. The efficiency of 226Ra uptake by plants from the soil is important to assess for the study of heavy metals uptake by plants, monitoring of radioactive pollution, and the biogeochemical cycle of radium in the Critical Zone. Using a thoroughly validated measurement method of effective 226Ra concentration (ECRa) in the laboratory, we compare ECRa values of the plant to that of the closest soil, and we infer the 226Ra soil-to-plant transfer ratio, RSP, for a total of 108 plant samples collected in various locations in France. ECRa values of plants range over five orders of magnitude with mean (min-max) of 1.66 ± 0.03 (0.020-113) Bq kg-1. Inferred RSP values range over four orders of magnitude with mean (min-max) of 0.0188 ± 0.0004 (0.00069-0.37). The mean RSP value of plants in granitic and metamorphic context (0.073 ± 0.002; n = 50) is significantly higher (12 ± 1 times) than that of plants in calcareous and sedimentary context (0.0058 ± 0.0002; n = 58). This difference, which cannot be attributed to a systematic difference in emanation coefficient, is likely due to the competition between calcium and radium. In a given substratum context, the compartments of a given plant species show coherent and decreasing RSP values in the following order (acropetal gradient): roots > bark > branches and stems ≈ leaves. Oak trees (Quercus genus) concentrate 226Ra more than other trees and plants in this set. While this study clearly demonstrates the influence of substratum on the 226Ra uptake by plants in non-contaminated areas, our measurement method appears as a promising practical tool to use for (phyto)remediation and its monitoring in uranium- and radium-contaminated areas.

First data on the structure of tubes formed by phoronids.

Phoronids are marine benthic animals that live in tubes in soft sediment or hard substrata; the phoronids form the tubes by digging or boring. Epidermal glands produce much of the material of the tube, which is completely imbedded in the soft sediment or hard substrata. The structure of phoronid tubes has not been previously studied in detail. In the current research, the morphology and microstructure of the tubes were studied by light microscopy, histology, and scanning electron microscopy for the following species: Phoronis ijimai, Phoronis svetlanae, Phoronis hipporcrepia, Phoronis australis, and Phoronopsis harmeri. In most of these species, the tube consists of an inner organic cylinder and an external layer. The inner organic cylinder is formed by three layers (inner, middle, and outer) of thin films. Each film is formed by fibers, whose thickness differs in different species. These fibers form a net, whose density is higher in digging phoronids than in boring phoronids. The middle layer is formed by highly compressed thin films. The outer layer is the densest portion of the inner cylinder and is associated with the external layer. The external layer is absent in some species (P. australis) but is well developed in digging phoronids. The differences in the organization of tube are consistent with the biology of each species and depend on the type of substrata and on the life style of the animal. Tube organization substantially differs between phoronids and sedentary annelids: the inner organic cylinder is much thicker in phoronid than in annelid tubes, and the fibers that form films are randomly oriented in phoronids but regularly oriented in annelids. In annelids but not in phoronids, inorganic particles in the external layer are usually surrounded and glued together by organic material. These differences may be used to distinguish phoronid tubes from annelid tubes in present-day benthic samples and also in fossil samples.

Colonization dynamics of protozoan communities in marine bioassessment surveys using two modified sampling systems.

Colonization dynamics of protozoan communities were investigated at a depth of 1 m in the coastal waters of the Yellow Sea, northern China from May to June 2019, using modified glass slide (mGS) and modified polyurethane foam unit (mPFU) systems. The colonization process and growth curves of protozoa were well fitted to the MacArthur-Wilson and logistic models in both systems, respectively. However, they showed significant differences in both colonization dynamics and biodiversity/functional parameters between the mGS and mPFU systems. The H' (species diversity), the G (colonization rate), and Amax (maximum abundance) were higher, while the value of T90% (the time for reaching 90% equilibrium species number) was lower in the mGS system than those in the mPFU system. Multivariate analyses demonstrated that protozoa showed different models of colonization dynamics in both systems. The results suggest that the mGS system might be more effective than the mPFU system in marine bioassessment surveys.

Artificial substrata increase pond farming density of grass carp (Ctenopharyngodon idella) by increasing the bacteria that participate in nitrogen and phosphorus cycles in pond water.

Aquaculture has become a primary method to produce various aquatic products, and intensive aquaculture technologies have become commercially important. To improve the efficiency of intensive aquaculture per unit area without reducing the growth rate of cultured fish, the present study explored the potential of artificial substrata in ponds. Our results showed that the concentrations of total nitrogen (TN) and total phosphorous (TP) in the ponds with different stocking densities of grass carp were lower than those in the control group in most cases. Further, the feed conversion rate of grass carp was significantly reduced by introducing these artificial substrata, and the culture density could be significantly increased without reducing the growth rates of these fish. Artificial substrata also significantly enriched specific bacteria and changed the structure of the microbiota in pond water. The relative abundance of Proteobacteria was significantly increased, and bacteria closely related to N and P cycles, such as Hyphomicrobium, Chitinimonas, Legionella, Shewanella, Roseiflexus, and Planktothrix were significantly enhanced. These results showed that the artificial substratum could increase TN and TP removal in aquaculture pond water by enriching N and P cycle-related bacteria, thus significantly increasing the specific growth rate of grass carp and significantly reducing their feed conversion rate. Finally, the stocking density of grass carp and the yield per unit area of pond could be increased without reducing the growth rate.

Invertebrate community responses to urban wastewater effluent pollution under different hydro-morphological conditions.

Urban wastewater effluents bring large amounts of nutrients, organic matter and organic microcontaminants into freshwater ecosystems. The effects of this complex mixture of pollutants on freshwater invertebrates have been studied mainly in temperate rivers and streams with high dilution capacities. In contrast, Mediterranean streams and rivers have lower dilution capacities especially during the seasonal drought, and are therefore exposed to high concentrations of pollutants. Here, we assess the effects of urban wastewater pollution on invertebrate communities from Mediterranean streams under different hydrological conditions. Specifically, we assessed the invertebrates taxonomic composition and functional biological traits in 12 streams, differing in stream and substrate size (sand or cobbles), under low (2 surveys) and baseflow (1 survey) conditions. In each stream, we selected reaches both upstream and downstream of the wastewater discharge point. Our results indicate that urban wastewater pollution favours the most tolerant invertebrate taxa and homogenises functional trait composition over time. Changes in functional traits were more evident during the seasonal drought, when the low flow conditions at the upstream and downstream sites were more severe and, pollutant concentrations downstream were at their highest. However, the effects of urban wastewater pollution were not uniform in the downstream sites; as local invertebrate communities differed in according to the river substrate and stream size (i.e., width and discharge). Overall, urban pollution caused by wastewater enhanced both, taxonomic and functional differences between the invertebrate communities. Such an absence of homogenisation among wastewater pollution impacted sites was probably related to the relevant role of stream substrate-size as well flow conditions in the rivers receiving the impact. These are attributes that need to be considered when setting the pollutant discharge limits in rivers and streams receiving effluents.