Diversity Of Benthic Invertebrates Research Articles

Oil and gas platforms degrade benthic invertebrate diversity and food web structure

Oil and gas exploitation introduces toxic contaminants such as hydrocarbons and heavy metals to the surrounding sediment, resulting in deleterious impacts on marine benthic communities. This study combines benthic monitoring data over a 30-year period in the North Sea with dietary information on >1400 taxa to quantify the effects of active oil and gas platforms on benthic food webs using a multiple before-after control-impact experiment. Contamination from oil and gas platforms caused declines in benthic food web complexity, community abundance, and biodiversity. Fewer trophic interactions and increased connectance indicated that the community became dominated by generalists adapting to alternative resources, leading to simpler but more connected food webs in contaminated environments. Decreased mean body mass, shorter food chains, and the dominance of small detritivores such as Capitella capitata near to structures suggested a disproportionate loss of larger organisms from higher trophic levels. These patterns were associated with concentrations of hydrocarbons and heavy metals that exceed OSPAR's guideline thresholds of sediment toxicity. This study provides new evidence to better quantify and manage the environmental consequences of oil and gas exploitation at sea.

Fish diversity declines with loss of sessile benthic invertebrate density on nearshore hardbottom communities in the Florida Keys, United States

Nearshore hardbottom communities are characterized by their invertebrate benthos, which provide food, habitat, and refuge for fish. Structural complexity supports greater species richness and abundance; thus, habitat degradation can reduce fish diversity and lead to a shift in community composition. Nearshore hardbottom communities in the Florida Keys, USA, have lost sessile benthic invertebrate diversity since the 1970s and the communities examined here have shifted from coral- and sponge-dominated to sponge- and algae-dominated. Two nearshore hardbottom communities (one oceanside site and one bayside) were surveyed from 1991 through 1996, and then were resurveyed in 2021 and 2022. Both communities experienced declines in fish richness, biodiversity, and trophic structure. Present-day fish species richness is approximately 30%–40% of what it was when surveying began in 1991. Sessile benthic invertebrate richness and density were correlated with fish richness and composition; the degradation of benthic communities appears to have negatively influenced fish assemblages. Diverse and abundant fish assemblages are key to healthy and productive coastal ecosystems; this loss of biodiversity will reduce the ecological functionality of nearshore hardbottom communities.

Determination of the ecological status of an Aegean river (Türkiye) using benthic macroinvertebrates as an indicator of water quality.

Bakırçay is one of the important rivers of Western Anatolia, Türkiye. The objectives of this study are (a) to determine the diversity of benthic invertebrates distributed in Bakırçay, (b) to evaluate the obtained data using various biological indices, (c) to determine the interactions of species with environmental variables, and (d) to estimate the water quality level of the river using BMWP and ASPT analyses. Samplings were carried out at 15 stations between October 2017 and July 2018, seasonally. A total of 11,897 specimens belonging to 136 benthic macroinvertebrate taxa were determined. Diptera and Oligochaeta were the dominant groups with 32 (24%) and 25 taxa (18%), respectively. Station 4 has the highest species richness with 49 taxa (36%). The highest individual number (3421) was at the 14th station. Tubifex tubifex and Physella acuta have the highest dominancy (25.76%) and frequency (51.67) values, respectively. Diversity (H') values of the stations fluctuated between 1.367 (st. 13) and 3.154 (st. 12). Similarity analysis showed that the 3rd and 11th stations have the highest similarity (> 90%), while the 14th station was an outgroup and has 28% similarity ratio. BMWP and ASPT scores gave similar results, and there was no 1st class water quality in the river. On the other hand, the results of the TR-BMWP score suggested that the 1st, 4th, and 6th stations had 1st class water quality. Although some stations are classified as "good conditions," the adverse effects of pollution were mainly observed in the main channel and downstream of the river.

Environmental drivers alter PUFA content in littoral macroinvertebrate assemblages via changes in richness and abundance

Shallow littoral areas in lakes are productive and highly diverse ecotonal zones, providing habitats for both invertebrate and vertebrate species. We developed a Bayesian modeling framework to elucidate the relationships between environmental drivers (lake typology, habitat, water chemistry, and latitude) and taxon richness, abundance, as well as the content of polyunsaturated fatty acids (PUFAs) in littoral macroinvertebrate communities in 95 boreal lakes. PUFAs, particularly arachidonic acid (ARA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), are critical micronutrients to maintain normal physiological functions in consumers. Lake typology was a significant predictor for PUFA content in the invertebrate assemblages, which was connected to taxon richness and/or abundance. Benthic communities in large humus-poor or nutrient-rich lakes displayed higher abundance, taxon richness, and more PUFA-rich taxa, whereas those in medium- and large-sized humic (color 30–90 mg Pt/L) and humus-rich lakes (color >90 mg Pt/L) were characterized by decreased abundance and subsequently low PUFA content. The abundance, taxon richness, and nutritional quality of the communities were also strongly related to latitude. Lakes with lower pH were characterized by lower benthic invertebrate diversity and low frequency of taxa with high somatic EPA and DHA content. The complexity of littoral habitats dominated by various macrophyte assemblages creates an environment that favors higher benthic abundance and increased presence of taxonomic groups with high PUFA content. Nutritional quality of benthic invertebrates for upper trophic levels can be modulated by a complex interplay between external stressors and abiotic factors that typically shape the structure of littoral benthic communities.

MACROINVERTEBRATES THE FOOTHILL LAKES OF THE NORTHERN AND NORTHEASTERN ALTAI

The taxonomic composition and abundance of benthic invertebrates in four lakes (Aya, Kireevo, Koksha and Svetloye) of the northern and northeastern Altai were studied in May, July and September 2022. 126 species from 9 classes of invertebrates were identifi ed in the macrozoobenthos of the studied lakes. Lakes Aya and Kireevo are characterized by low species diversity, abundance and biomass of benthic invertebrates. According to the composition and structure of communities of benthic invertebrates, lakes Aya and Kireevo were close to fl atland and low-mountain lakes. High taxonomic diversity and abundance of macroinvertebrates in lakes Koksha and Svetloye were noted. The bottom population of these lakes had features of both fl atland and mountain lakes.

Isolation controls reestablishment mechanisms and post-drying community structure in an intermittent stream.

Biota in disturbance-prone landscapes have evolved a variety of strategies to persist long term, either locally (resistance) or by regional recolonization (resilience). Habitat fragmentation and isolation can limit the availability of recolonization pathways, and thus the dynamics of post-disturbance community reestablishment. However, empirical studies on how isolation may control the mechanisms that enable community recovery remain scarce. Here, we studied a pristine intermittent stream (Chalone Creek, Pinnacles National Park, California) to understand how isolation (distance from a perennial pool) alters invertebrate community recolonization after drying. We monitored benthic invertebrate reestablishment during the rewetting phase along a ~2-km gradient of isolation, using mesh traps that selected for specific recolonization pathways (i.e., drift, flying, swimming/crawling, and vertical migration from the hyporheic). We collected daily emigration samples, surveyed the reestablished benthic community after 6 weeks, and compared assemblages across trap types and sites. We found that isolation mediated migration dynamics by delaying peak vertical migration from the hyporheic by ca. 1 day on average per 250 m of dry streambed. The relative importance of reestablishment mechanisms varied longitudinally-with more resistance strategists (up to 99.3% of encountered individuals) in the upstream reaches, and increased drift and aerial dispersers in the more fragmented habitats (up to 17.2% and 18%, respectively). Resistance strategists persisting in the hyporheic dominated overall (88.2% of individuals, ranging 52.9%-99.3% across sites), but notably most of these organisms subsequently outmigrated downstream (85.6% on average, ranging 52.1%-96% across sites). Thus, contrary to conventional wisdom, resistance strategists largely contributed to downstream resilience as well as to local community recovery. Finally, increased isolation was associated with a general decrease in benthic invertebrate diversity, and up to a 3-fold increase in the relative abundance of drought-resistant stoneflies. Our results advance the notion that understanding spatial context is key to predicting post-disturbance community dynamics. Considering the interaction between disturbance and fragmentation may help inform conservation in ecosystems that are subject to novel environmental regimes.

Trace elements in relation to trophic ecology of long-distance migratory shorebirds and seabirds in West Africa

Shorebirds and seabirds are abundant predators in coastal habitats worldwide, relying upon a high diversity of benthic invertebrates and fish, respectively. While occupying different trophic guilds, they are differently exposed to element contamination entering the coastal food web. Therefore, these birds have been used as bioindicators of environmental contamination in marine ecosystems. We analysed the concentration of trace elements in blood samples of 16 shorebird and seabird migratory species in a major non-breeding site, the Bijagós Archipelago, in regard to their trophic ecology. Overall, our study shows low exposure of this bird community to toxic elements, except for Hg. Most species presented Hg burdens within the moderate toxicity threshold, but one species (Dunlin) presented values at a potential high Hg toxicity risk. We found a positive relationship between Se and Ni concentrations and δ15N values (a proxy for trophic level). In addition, a positive relationship was found between δ13C (a proxy for habitat characteristics) and Hg, Fe, Cu and Mn, while the opposite pattern was recorded for As. Differences were also shown for several trace elements between the two studied trophic guilds: concentrations of As, Pb and Se were higher in pelagic fish consumers (seabirds), whereas Cr, Fe and Sr burdens were higher in benthic invertebrate consumers (shorebirds). Although previous studies in the same site revealed very high concentrations of Cd and Pb in some of the prey species of shorebirds and seabirds (bivalves and fishes), values found in birds for these two elements suggest no toxicological risk. Thus, exposure to toxic elements is not currently a threat to coastal bird populations, namely those facing apparent local declines in Guinea-Bissau, one of the most important non-breeding quarters for of West Africa. Still, Hg burdens were high in some species, deserving further monitoring.

Diversity and distribution of benthic invertebrates dwelling rivers of the Kruger National Park, South Africa

Meiobenthos (or meiofauna) are microscopic invertebrates that inhabit biofilms and interstitial spaces in rivers. They are diverse and extremely abundant, and they perform essential ecological functions by linking microbial production to higher trophic levels (e.g. macrobenthic invertebrates and fishes). However, meiobenthic communities remain poorly studied in Africa. Here, we sampled meio- and macrobenthic invertebrate communities associated with biofilms and sediments across an upstream–downstream gradient along the Olifants, Sabie and Crocodile rivers flowing through the Kruger National Park (KNP). We expected to link differences in community structure to environmental gradients as those rivers show different degrees of anthropogenic stress as they enter the park. Both meio- and macrobenthic communities differed across rivers and also structured along an upstream–downstream gradient. The upstream sites, which were the closest to the park borders, consistently showed a lower diversity in all three rivers. There, the invasive snail Tarebia granifera strongly dominated (making up 73% – 87% of the macrobenthos), crowding hard substrates, while concomitantly the abundances of biofilm-dwelling meiobenthos like nematodes and rotifers were substantially reduced. Nevertheless, the diversity and evenness of communities then tended to increase as water flowed downstream through the park, suggesting a beneficial effect of protected river reaches on benthic invertebrate diversity. However, for the Crocodile River, which makes up the southern border of the park, this trend was less conspicuous, suggesting that this river may experience the greatest threats. More generally, benthic invertebrate communities were driven by the concentrations of phosphates, sulphates, ammonium and organic matter and by substrate characteristics.Conservation implications: Meiobenthic organisms are very abundant in KNP rivers and react to environmental gradients; thus, they should be more considered for bio-monitoring or conservation of comprehensive assemblages of animals. Interestingly, protected reaches tended to show a reduced dominance of the invasive T. granifera and a higher diversity of benthic invertebrates.

Are springs hotspots of benthic invertebrate diversity? Biodiversity and conservation priority of rheocrene springs in the karst landscape

Abstract Springs are perceived by human society as essential sources of drinking water, but on the other hand they represent peculiar and vulnerable ecosystems. They differ from other watercourses in the relatively high stability of their physicochemical conditions. As a result, springs represent ecosystems with an insular character, usually inhabited by specific aquatic communities. Although springs are generally considered species‐rich habitats across the world, they have been outside scientific and conservation interest in the karst mountains of the Western Carpathians. This study, therefore, examined the diversity of spring benthic macroinvertebrates and compared it with that of other watercourses of the Western Carpathian riverine landscape. The results of the study showed that, in contrast to rhithral streams, individual karst springs often had low species richness, and therefore they cannot be considered biodiversity hotspots. However, their metacommunity diversity is characterized by high taxonomic turnover, resulting in high gamma diversity. This means that the individual springs often harbour unique macroinvertebrate communities, so they are worthy of protection. However, the present level of spring habitat protection is insufficient as even springs located in protected areas are often captured as sources of drinking water and hydromorphologically or otherwise disturbed. A simple method to evaluate the spring conservation priority (CP) was developed to find a better trade‐off between their use and protection. It uses the number of Red List, endemic and crenal taxa, as well as the total species richness at each site. Based on this classification method, 16% of the springs studied reached very high CP, 39% high CP, 33% moderate CP and 12% low CP. The proposed management recommendations based on findings of conservation priority of the Western Carpathian karst springs can significantly contribute to their more effective protection and the creation of a legislative framework relating to spring habitat protection in general.

Effects of Spartina alterniflora invasion on the benthic invertebrate community in intertidal wetlands

AbstractExotic species invasions have profound effects on native ecosystems, with the ecological effects of non‐native plants being especially pervasive. We investigated the impacts of a plant invasion on benthic invertebrate assemblages in intertidal wetlands of the Yellow River Delta, comparing benthic communities associated with exotic Spartina alterniflora against those associated with native plants (Tamarix chinensis, Suaeda salsa, and mudflat). Our study surprisingly found that the density, diversity, and richness of benthic invertebrates associated with S. alterniflora were higher than with native habitats. Multivariate analysis also revealed that the structure of benthic invertebrates in S. alterniflora habitats was different than in T. chinensis and mudflat habitats. The structure of invertebrates associated with the invasive S. alterniflora and native S. salsa was more similar, although the dominant species differed. Indicator species analyses indicated that each habitat was characterized by unique taxa. S. alterniflora invasion increased the beta diversity of the community, with the species turnover component being of most importance. Mollusks were most likely to be influenced by Spartina invasions. Given the extent of the S. alterniflora invasion in the Yellow River Delta, altered benthic invertebrate communities will likely have important implications for the ecology of the intertidal wetland ecosystems and deserve increased attention.

ЗООИНДИКАЦИЯ ВОДОЕМОВ НА ТЕРРИТОРИИ НЕФТЯНЫХ МЕСТОРОЖДЕНИЙ БОЛЬШЕЗЕМЕЛЬСКОЙ ТУНДРЫ

Intensive development of the oil and gas industry and accidents on oil pipelines become the reason of the environmental tension in the Pechora River basin (Nenets Autonomous District). Data on changes in water quality in five lakes and a small watercourse in the territory of oil fields of the Bolshezemelskaya tundra are presented. The bioindication indices (Berger-Parker (D), Shannon biodiversity (H '), Woodiwiss (W), Pantle-Buck (S), Balushkina (Kch)) were applied. The assessment of the state of water bodies in the Kolva River Basin (large lakes - Kolvaty and Nercheity), in the Laya River Basin (shallow lakes - Krugloye, Bezymyannoe 1, Bezymyannoe 2, stream) was done. The 28 samples of zoobenthos was processed by the standard method in July 2012 and 2019. A low diversity of benthic invertebrates was revealed for 5–20 taxa of the rank of families and orders. During the considered period, the changes have occurred in the structure and composition of the zoobenthos of water bodies. In 2019, the species diversity decreased in Kolvaty Lake (H'<2). There are no species of the crustacean complex (Monoporeia affinis, Mesocyclops leuckarti, Heterocope borealis) and larvae of Trichoptera. Only Sphaeriidae and Chironomidae with a predominance of Psectrocladius psilopterus (D = 55%) were recorded. The species diversity in Nercheity Lake increased (H'> 2) with a change in the dominant taxa: the larvae of the chironomids Ablabesmyia monilis (D = 44%) were found in 2012, the lower crustaceans (D = 47–51%) - in 2019. However, according to the totality of hydrobiological indicators, the quality of water in the lakes of the Kolva River Basin in 2019 compared to 2012 did not change significantly. The quality of water in the Krugloye and Bezymyannoe 1, Bezymyannoe 2 lakes (the Laya River Basin) has improved that is confirmed by a significant increase of species diversity. The most characteristic groups of benthic communities in these lakes are lower crustaceans (Cladocera, Copepoda, Ostracoda) and Chironomidae. The indicators of clean waters are o-β-mesosaprobic species Cladocera, Copepoda Heterocope appendiculata, Heterocope borealis (in the oligotrophic lakes), caddisfly Limnephilus stigma (in the Krugloe Lake), rotifer Polyarthra euryptera (in the Bezymyannoe 2 Lake), mayfly larvae Centroptilum luteolum. More resistant to organic pollution Copepoda began to prevail in abundance and diversity in Bezymyannoe 1 and Bezymyannoe 2 lakes, with a decrease in the taxonomic composition of Cladocera, which indicates the eutrophication of these water bodies. In most lakes, the water corresponds to the III quality class ("moderate pollution"), but in the Kolvaty lake and in the Bezymyanny stream (the Laya River basin) was recorded the biogenic pollution. Totally, insignificant taxonomic changes in zoobenthos structure took place in the lakes and the state of water bodies of the surveyed tundra remains relatively stable.

Ecological Conditions of the Lower Dniester and Some Indicators for Assessment of the Hydropower Impact

The Dniester is one of the largest transboundary rivers of the Black Sea basin, and its lower reaches integrate the influence of climate change and hydropower plant (HPP) impact on the waterway. The decrease in precipitation and average annual air temperature increase and intensive hydroelectric construction have led to a decline in the total water content of the river, during the last 10 years, being below the long-term historical “norm”. The shifts in the river flow result in multidirectional seasonal dynamics of nutrient concentrations. During the modern period, a stabilization of nutrient concentrations takes place, being lower than at the peak of eutrophication in the 1970s–1980s, but higher than in the natural flow period. The construction of reservoirs leads to a long-term decline in silica concentrations, continuing in the modern period. The concentration of heavy metals and metalloids in water and bottom sediments of the river generally corresponds to the ecological status of “Moderate”. Biological communities show a high β-diversity of microalgae, but low diversity of plankton and benthic invertebrates. Biological communities respond to the impact of HPP in both the short- and long-term. Hydroelectric dams change the bioavailability of nutrients downstream which, in the long-term, causes shifts in phytoplankton composition, especially the reduction of Bacillariophyta due to the lack of silicates that are deposited in reservoirs. However, in the short-term, after the discharge from the HPP dam, the concentration of silicates and the proportion of diatoms increase. Long-term changes also include a decline in the proportion of Rotifera and an increase in Copepoda in the total abundance of zooplankton and the unification of the benthic community with an increase in the biomass of gastropods in the area, which can be considered as indicators of the impact of hydroelectric power plants. The saprobity index, calculated both for zooplankton and macrozoobenthos, characterised the water as moderately polluted; benthic biotic indexes (Biological monitoring working party (BMWP), Belgian Biotic Index (BBI), Danish Stream Fauna Index (DSFI)) calculated on macrozoobenthos described the condition as “low” quality.

Assessment of benthic invertebrate diversity and river ecological status along an urbanized gradient using environmental DNA metabarcoding and a traditional survey method

Benthic invertebrate diversity is one of the most commonly used bioindicators for assessing aquatic ecosystem health in river systems. Although an increasing number of studies have focused on assessing benthic invertebrate diversity using environmental DNA metabarcoding and traditional survey methods, benthic invertebrate diversity and ecological status assessments performed across different landscapes within river systems have not been well documented. Here, the diversity and ecological status of benthic invertebrates and the influence of water quality on the invertebrate assemblage distribution along an urbanization gradient in rivers from the Jingjinji (JJJ) region, China, were investigated using eDNA metabarcoding and the traditional method. With the combination of the two methods, 395 benthic invertebrates from 6 phyla, 27 orders, 94 families, and 222 genera were identified. The species richness of the benthic invertebrate community in the mountain area was significantly higher than that in the urban and agricultural areas. Compared to the traditional results, eDNA metabarcoding obtained a significantly greater number of species from every sampling site (P = 0.000) and detected a notably higher abundance in Annelida (P = 0.000). Furthermore, the nonmetric multidimensional scaling (NMDS) and permutational multivariate analysis of variance (PERMANOVA) based on the Bray-Curtis dissimilarity index indicated that the benthic invertebrate communities from the different habitats were discriminated more accurately and easily using eDNA metabarcoding (P = 0.038) than with the traditional method (P = 0.829). Additionally, the assemblages identified by eDNA metabarcoding were more closely linked to water quality and could be realistically used to assess the ecological status of rivers. Our findings highlight that eDNA metabarcoding could represent a rapid and reliable method for estimating benthic invertebrate diversity and ecological status in river systems.

Linear and nonlinear effects of nutrient enrichments on the diversity of macrobenthos in lowland watercourses

The study concerns the relationships between taxonomic, functional and phylogenetic diversity of benthic invertebrates inhabiting watercourses and abiotic parameters associated with excessive nutrients load (concentration of Kjejdahl nitrogen, nitrates, phosphorus, organic carbon and dissolved oxygen, values of BOD5 and electrolytic conductivity). The research used data on the species composition of leeches, molluscs and larval forms of odonates and chironomid dipterans. Their description using mathematical functions allowed to determine whether the diversity reaches maximal values at extreme or moderate values of nutrients enrichment. In most cases, statistically significant relationships were unimodal—the highest diversity was observed at intermediate values of nutrients content and associated parameters, however the different patterns of relationships, monotonic and inverse quadratic, were also observed. Indirect impacts of nutrients enrichment on diversity were found as the most significant relationships. Significant responses of functional diversity were clearer and stronger than responses of taxonomic and phylogenetic diversity. The identification of fauna to the species level allowed for obtaining precise results that could enable selection of appropriate parameters for effective assessment of environmental degradation.

The physical–chemical environment and benthic invertebrate assemblages of two thermal springs located on carbonate and ophiolite rocks in northern Oman

ABSTRACT The paper compares the physical and chemical environments and associated benthic invertebrate assemblages of two thermal streams with different geology in Oman. Nakhal Thawarah is a thermal spring originating in carbonate rocks. Mur-Fayha has its origin in igneous ophiolite rocks. The main physical and chemical parameters that contribute to the differences are water temperature, pH, electrical conductivity, total dissolved solids, chloride, sulphate, calcium and magnesium. Two zones in each spring-stream system, the source and stretch analysed, reveal intra- and interstream differences in the physical and chemical environments controlling the occurrence and abundance of benthic invertebrates. Despite higher water temperatures, the diversity of benthic invertebrates in Nakhal Thawarah is relatively high. Mur-Fayha with high alkalinity is a harsh environment that has low diversity dominated by tolerant Chironomidae. This study indicates the need to conserve thermal springs in Oman from adverse effects of tourism.

Intraspecific diversity loss in a predator species alters prey community structure and ecosystem functions.

Loss in intraspecific diversity can alter ecosystem functions, but the underlying mechanisms are still elusive, and intraspecific biodiversity–ecosystem function (iBEF) relationships have been restrained to primary producers. Here, we manipulated genetic and functional richness of a fish consumer (Phoxinus phoxinus) to test whether iBEF relationships exist in consumer species and whether they are more likely sustained by genetic or functional richness. We found that both genotypic and functional richness affected ecosystem functioning, either independently or interactively. Loss in genotypic richness reduced benthic invertebrate diversity consistently across functional richness treatments, whereas it reduced zooplankton diversity only when functional richness was high. Finally, losses in genotypic and functional richness altered functions (decomposition) through trophic cascades. We concluded that iBEF relationships lead to substantial top-down effects on entire food chains. The loss of genotypic richness impacted ecological properties as much as the loss of functional richness, probably because it sustains “cryptic” functional diversity.

Benthic invertebrate assemblage changes in an urban bay of Lake Ontario: 1990 to 2012

Invasions by dreissenid mussels and the round goby have altered the makeup of benthos in many areas of the Great Lakes complicating the use of benthic invertebrate composition as an indicator of environmental conditions. The Ontario Ministry of the Environment, Conservation and Parks (MECP) has been monitoring the composition of benthos at nearshore stations since the 1990s. The interactive influences of environmental change and invasive species have been evident in areas of the Toronto Waterfront such as Humber Bay (HB), an area of intensifying urbanization. Dreissenid mussels were first detected in HB in 1994, became abundant in 2000, and were followed by the round goby in 2005. Both invasions overlapped with increasing population density in the watershed and efforts to reduce pollutant and nutrient inputs. Benthic invertebrate diversity increased post-dreissenids, with densities of gastropods and amphipods increasing during peak mussel abundance (2000–2003). Dreissenid abundance declined after 2005, and snails (Valvatidae) disappeared, corresponding with increasing goby abundance. Abundance of sphaeriid clams declined over the monitoring period. Water clarity increased and the chlorophyll a level declined in the mid-1990s, before dreissenids were abundant at the site. Trophic conditions inferred from invertebrate composition shifted from oligotrophic in 1990 to mesotrophic and back to oligotrophic in 2012. There was little change in sediment quality other than a subtle increase in clay and fine silt at the primarily silty site. The trajectory of changes in the benthos was more strongly correlated with the dreissenid and goby invasions than changes in environmental quality.

Diversity and microhabitat use of benthic invertebrates in an urban forest stream (Southeastern Brazil)

ABSTRACT This work aimed to assess the diversity and microhabitat use of benthic invertebrates in an urban forest stream in southeastern Brazilian region. The invertebrates were sampled in a headwater stream, located at the Tijuca Forest, Rio de Janeiro. Three types of microhabitats were sampled (litter, sand and stone) using a Surber sampler. Specimens were identified to the family-level and rarefaction curves were constructed for the total sampling and for each type of microhabitat. Community structure indices (abundance, taxonomic richness, diversity, and dominance) were calculated for each microhabitat. Differences among indices were tested through a repeated measure ANOVA, and differences among microhabitatsʼ composition through a PerMANOVA. A total of 9,800 specimens were registered in which Chironomidae was the most abundant. The rarefaction curves did not reach the asymptote. Community structure indices exhibited differences (RM ANOVA; p < 0.001), as well as microhabitats’ composition (PerMANOVA; p < 0.001). Abundance and taxonomic richness were the highest in litter, diversity was higher both in litter and stone, and sand had the highest dominance. Results highlighted that the variety of microhabitats may enhance local diversity and that the differences in resources availability of each type of microhabitat determine the distribution of these invertebrates.

Does the buffer width matter: Testing the effectiveness of forest certificates in the protection of headwater stream ecosystems

Forest harvest has multiple impacts on adjoining freshwater ecosystems, particularly headwater streams which typically receive minimal protection against forestry. However, evidence on the effectiveness of differently sized riparian buffers remains limited. Using data from two discrete regions of Finland, we assessed the effectiveness of riparian buffers in providing protection for the riparian and stream environment, benthic invertebrate diversity and species composition, and ecosystem functioning of boreal headwater streams. Our study included streams with both wide (>15 m) and narrow (<15 m) riparian buffers, enabling comparison of the two dominant forest certificates (FSC and PEFC). Compared to unharvested reference streams, nutrient concentrations as well as stream and riparian light intensity and temperature were higher at forestry-impacted sites. The amount of woody debris, cover of aquatic mosses and particulate organic matter standing stock were strongly reduced in streams draining harvested forests, especially in narrowly buffered streams. Changes in light and nutrient conditions induced a transition towards more autotrophic conditions. Organic matter decomposition rates were elevated in forestry-impacted sites only in the southern region. Forest harvest decreased macroinvertebrate diversity and evenness, and altered community composition in the northern region, but much weaker changes were observed in the southern region. Our findings support the retention of riparian buffers, but also confirm that their effectiveness depends on the environmental context and thus remains poorly predictable. Our results also suggest that the widely applied PEFC certification does not provide sufficient protection for stream ecosystems and more stringent protocols are needed to ensure ecological sustainability of forestry.

Beyond ecological opportunity: Prey diversity rather than abundance shapes predator niche variation

AbstractEcological opportunity (i.e. the diversity of available resources) has a pivotal role in shaping niche variation and trophic specialisation of animals. However, ecological opportunity can be described with regard to both diversity and abundance of resources. The degree to which these two components contribute to niche variation remains unexplored.To address this, we used an extensive dataset on fish diet and benthic invertebrate diversity and density from 73 sampling events in three Norwegian rivers in order to explore realised trophic niches and the response of dietary niche variation along gradients of resource diversity (potential trophic niches), resource density (as a proxy of resource abundance) and fish density (as a proxy of inter‐ and intra‐specific competition) in a freshwater top predator (the brown trout,Salmo truttaL.).Linear models indicated that individual and population niche variation increased with increasing ecological opportunity in terms of prey diversity. However, no simple cause‐and‐effect associations between niche indices and prey abundance were found. Our multiple regression analyses indicated that the abundance of certain resources (e.g. Chironomidae) can interact with prey diversity to determine individual and population realised trophic niches. Niche variation (within‐individual component and inter‐individual diet variation) decreased with increasing inter‐ and intra‐specific competition.This study extends prevailing trophic ecology theory by identifying diversity, rather than density, of available prey resources as a primary driver of niche variation in fish of temperate riverine systems with no extensive resource limitation. The study also shows that ecological opportunity may mask the direction of the effect (compression or expansion) of competition on niche variation when food resources are diverse.Our study provides novel empirical insight to the driving forces behind niche variation and reveals that diversity, rather than density, of available prey resources may be a primary driver of niche variation in freshwater fish. Our study supports the view that a broader potential trophic niche promotes broader realised trophic niche variation by individuals, which leads to individual niche diversification by opening access to alternatives resources, resulting in a concomitant rise in the realised trophic niche width of the population.