Macroinvertebrate Assemblages Research Articles

Variation in macroinvertebrate assemblages and water quality as a test for different levels of ecological impairment across an Ethiopian highland river system

The Ethiopian highlands is an area under high anthropogenic pressure. Despite being a hotspot for freshwater biodiversity, there is no regular monitoring of the ecological status of local rivers. Physicochemical and nutrient water-quality parameters and macroinvertebrate assemblages were sampled monthly from the Megech River and its tributaries from January to March 2021. Sampling locations were designated as being either upstream or downstream of the Gondar City urban area. We tested for temporal (monthly) and spatial (location, river) variation in water quality and spatial (location, river) variation in macroinvertebrate assemblage structure, and examined which water quality parameters were most associated with patterns in macroinvertebrate assemblages. Water quality varied significantly between locations and months, but not between rivers. Water quality differences were particularly driven by higher nutrient, salinity, dissolved solids and conductivity levels downstream, and higher pH and dissolved oxygen levels upstream. Despite macroinvertebrate assemblages being more abundant and diverse downstream, biotic index scores generally indicated slightly increased ecological impairment downstream. There was a clear spatial pattern in macroinvertebrate assemblages between locations. We detected a significant difference between rivers, with pairwise differences between sampling locations, particularly due to high dissimilarity between the upstream and downstream locations of the Angereb, Shinta and Qeha rivers. BIO-ENV Pearson correlations indicated that variation in macroinvertebrate assemblages were mostly explained by dissolved oxygen, salinity and nutrient parameters including nitrate, ammonium, and sulphate. Our findings confirm the need for more rigorous monitoring of Ethiopian highland rivers and improved management of nutrient inputs.

Improving the performance of macroinvertebrate based multi-metric indices by incorporating functional traits and an index performance-driven approach

Human-driven multiple pressures impact freshwater ecosystems worldwide, reducing biodiversity, and impacting ecosystem functioning and services provided to human societies. Multi-metric indices (MMIs) are suitable tools for tracking the effects of anthropogenic pressures on freshwater ecosystems because they incorporate various biological metrics responding to multiple pressures at different levels of biological organization. However, the performance and applicability of MMIs depend on their metrics' selection and their calibration against natural environmental gradients. In this study, we aimed to unravel i) how incorporating functional trait-based metrics affects the performance of MMIs, ii) how disentangling the natural environmental gradients from anthropogenic pressures effects affects the performance of MMIs, and iii) how the performance of MMIs developed using a metric performance-driven approach compares with MMIs developed using an index performance-driven approach. We carried out a field survey measuring abiotic and biotic variables at 53 sites in the Karun River basin (Iran) in 2018. For functional trait-based metrics, we used 15 macroinvertebrate traits and calculated community-weighted mean trait values and functional diversity indices. We used random forest modeling to account for the effect of natural environmental gradients on each metric. Based on our results, incorporating functional traits increased the MMI performance significantly and facilitated ecological interpretation of MMIs. Both taxonomic and functional components of macroinvertebrate assemblages co-varied strongly with natural environmental gradients, and accounting for these covariations improved the performance of MMIs. Finally, we found that index performance-driven MMIs performed better in terms of precision, bias, sensitivity, and responsiveness than metric performance-driven MMIs.

Effects of natural flood management woody dams on benthic macroinvertebrates and benthic metabolism in upland streams: Importance of wood‐induced geomorphic changes

AbstractNatural Flood Management (NFM) aims to reduce flood hazard by working with nature and is gaining prominence worldwide. One particular NFM technique involves the use of channel‐spanning woody dams that maintain a clearance height above baseflow. These dams function by increasing channel roughness during high flows and by forcing excessive water onto the floodplain. Whether these dams provide additional benefits to nature remains unclear. While there are many existing studies on natural in‐stream wood structures, very few have documented the impact of NFM woody dams in particular. This study adopted a multidisciplinary approach and a Before–After Control–Impact (BACI) research design to assess whether NFM woody dams installed in a small upland catchment had driven changes in benthic macroinvertebrate assemblages and benthic metabolic activities through the geomorphic changes that they had created. Statistical results indicate that macroinvertebrate density, richness, and diversity did not show any difference between stream reaches with and without NFM woody dams. The metrics were generally not related to grain‐size parameters and volumes of sediments eroded or deposited. However, individual genera such as Baetis and Rhithrogena became more dominant in the control reach towards the end of the study period, likely due to the higher flow velocities and coarser sediments there resulting from the lack of flow resistance in the absence of NFM woody dams. Rates of benthic respiration (but not rates of photosynthesis) were consistently significantly higher in woody dam reaches than in control reaches, likely due to the presence of patches of finer sediments in the former.

The structure and diversity of macroinvertebrate assemblages associated with the understudied pseudo-kelp Saccorhiza polyschides in the Western English Channel (UK)

We examined spatiotemporal variability in the structure of faunal assemblages associated with the warm-temperate pseudo-kelp Saccorhiza polyschides towards its range centre (Western English Channel, southwest UK), to better understand its role as a habitat-former in the northeast Atlantic. A total of 180 sporophytes and their associated fauna were sampled across three months, three sites, and two depths. Assemblage abundance and biomass varied markedly between three morpho-functional sporophyte components (i.e., holdfast, stipe, blade). We recorded rich and abundant macroinvertebrate assemblages, comprising nine phyla, 28 coarse taxonomic groups, and 57 species of molluscs, which consistently dominated assemblages. We observed pronounced seasonality in faunal assemblage structure, marked variability between sites and depths, and strong positive relationships between biogenic habitat availability and faunal abundance/biomass. S. polyschides sporophytes are short-lived and offer temporary, less-stable habitat compared with dominant perennial Laminaria species, so shifts in the relative abundances of habitat-formers will likely alter local biodiversity patterns.

Temporal and spatial drivers of the structure of macroinvertebrate assemblages associated with Laminaria hyperborea detritus in the northeast Atlantic

Kelp forests occur on more than a quarter of the world's coastlines, serving as foundation species supporting high levels of biodiversity. They are also a major source of organic matter in coastal ecosystems, with the majority of primary production released and exported as detritus. Kelp detritus also provides food and shelter for macroinvertebrates, which comprise important components of inshore food-webs. Hitherto, research on kelp detritus-associated macroinvertebrate assemblages remains relatively limited. We quantified spatiotemporal variability in the structure of detritus-associated macroinvertebrate assemblages within Laminaria hyperborea forests and evaluated the influence of putative drivers of the observed variability in assemblages across eight study sites within four regions of the United Kingdom in May and September 2015. We documented 5167 individuals from 106 taxa with Malacostraca, Gastropoda, Isopoda and Bivalvia the most abundant groups sampled. Assemblage structure varied across months, sites, and regions, with highest richness in September compared to May. Many taxa were unique to individual regions, with few documented in all regions. Finally, key drivers of assemblage structure included detritus tissue nitrogen content, depth, sea surface temperature, light intensity, as well as L. hyperborea canopy density and canopy biomass. Despite their dynamic composition and transient existence, accumulations of L. hyperborea detritus represent valuable repositories of biodiversity and represent an additional kelp forest component which influences secondary productivity, and potentially kelp forest food-web dynamics.

Benthic assemblages in relation to planktonic assemblages in a eutrophic, thermally stratified reservoir

Few studies have explored the relationship between benthic and planktonic assemblages in reservoirs, despite their role in food chains and maintaining ecological functions. Macroinvertebrates play a crucial role in food webs and contribute about 42% of whole-lake secondary productivity. Therefore, their status is vital for maintaining good ecological functions. In this study, we selected Nanwan Reservoir, a eutrophic thermally stratified reservoir in China, to evaluate the community of macroinvertebrates in different seasons and explore the relationships between macroinvertebrate assemblages and different planktonic groups, including phytoplankton, protozoans, rotifers, and planktonic crustaceans. Cyanophyta and Bacillariophyta dominated the phytoplankton assemblages, and their proportions varied with seasons. The bad community of macroinvertebrates in summer, autumn, and winter could be attributed to the excessive growth of Cyanophyta or other phytoplankton. Based on the results of partial least squares regression, an algorithm used for prediction, we determined that the excessive growth of algae, crustaceans, protozoans, and Cyanophyta was detrimental to the development of macroinvertebrates, and was indicative of high nutrient loads in the reservoir. However, the growth of Bacillariophyta, Chrysophyta, and Euglenophyta was advantageous to macroinvertebrate assemblages and indicated a better ecological condition of the reservoir. The results of partial least squares structural equation modeling demonstrated close associations between phytoplankton and both zooplankton and macroinvertebrates, indicating their interdependence in this reservoir system. Our study results imply that the status of macroinvertebrates can be predicted by the abundance of some planktonic assemblages, and cost savings from selecting one of the planktonic groups to monitor ecological conditions could be accomplished in future studies.

Drivers of macroinvertebrate assemblages in littoral and pelagic habitats of a large shallow lake: implications for bioassessment

Drivers of macroinvertebrate assemblages in littoral and pelagic habitats of a large shallow lake: implications for bioassessment

Drivers of Macroinvertebrate Communities in Mediterranean Rivers: A Mesohabitat Approach

We investigated the relationship between benthic macroinvertebrate community attributes (richness, abundance, biodiversity, and climate-specific and resistance forms) and the physical characteristics of distinct mesohabitats (hydromorphological unit types) discretized into fast (e.g., riffles or rapids) and slow (e.g., pools or glides) flow types in four Mediterranean rivers of Spain. Key attributes of hydromorphological units, including length, width, depth, shade, substrate composition, embeddedness, abundance of aquatic vegetation, and density of woody debris, were considered. Through a comprehensive suite of multivariate analyses, we unraveled taxonomic and habitat distinctions among rivers and hydromorphological unit types, with a notable influence of spatial proximity (greater similarity within the same river basin). In slow hydromorphological units, aquatic vegetation, depth, and abundance of coarse substrate emerged as pivotal factors shaping macroinvertebrate assemblages, whereas in fast-flowing units, vegetation, substrate embeddedness, and density of woody debris were the most important. Contrary to the remaining community attributes, the studied resistance forms (absent, eggs, cocoons, and cells against desiccation and diapause) exhibited uniformity across rivers despite observed variations in macroinvertebrate communities, underscoring regional functional analogies in biological and ecological mechanisms within the investigated Mediterranean river basins. This study contributes valuable insights for anticipating the repercussions of ongoing climate change, particularly in regions where fast-flowing hydromorphological units are more susceptible to depletion during drought periods.

Structure and Diversity of Mobile Macro-invertebrate Assemblages Associated to Different Seaweeds

Structure and Diversity of Mobile Macro-invertebrate Assemblages Associated to Different Seaweeds

Climate warming shifts riverine macroinvertebrate communities to be more sensitive to chemical pollutants.

Freshwaters are highly threatened ecosystems that are vulnerable to chemical pollution and climate change. Freshwater taxa vary in their sensitivity to chemicals and changes in species composition can potentially affect the sensitivity of assemblages to chemical exposure. Here we explore the potential consequences of future climate change on the composition and sensitivity of freshwater macroinvertebrate assemblages to chemical stressors using the UK as a case study. Macroinvertebrate assemblages under end of century (2080-2100) and baseline (1980-2000) climate conditions were predicted for 608 UK sites for four climate scenarios corresponding to mean temperature changes of 1.28 to 3.78°C. Freshwater macroinvertebrate toxicity data were collated for 19 chemicals and the hierarchical species sensitivity distribution model was used to predict the sensitivity of untested taxa using relatedness within a Bayesian approach. All four future climate scenarios shifted assemblage compositions, increasing the prevalence of Mollusca, Crustacea and Oligochaeta species, and the insect taxa of Odonata, Chironomidae, and Baetidae species. Contrastingly, decreases were projected for Plecoptera, Ephemeroptera (except for Baetidae) and Coleoptera species. Shifts in taxonomic composition were associated with changes in the percentage of species at risk from chemical exposure. For the 3.78°C climate scenario, 76% of all assemblages became more sensitive to chemicals and for 18 of the 19 chemicals, the percentage of species at risk increased. Climate warming-induced increases in sensitivity were greatest for assemblages exposed to metals and were dependent on baseline assemblage composition, which varied spatially. Climate warming is predicted to result in changes in the use, environmental exposure and toxicity of chemicals. Here we show that, even in the absence of these climate-chemical interactions, shifts in species composition due to climate warming will increase chemical risk and that the impact of chemical pollution on freshwater macroinvertebrate biodiversity may double or quadruple by the end of the 21st century.

Spatial Distribution of Benthic Macroinvertebrate Assemblages in Wetlands of Jeju Island, Korea

Spatial Distribution of Benthic Macroinvertebrate Assemblages in Wetlands of Jeju Island, Korea

Kelp holdfasts in the Great African Seaforest provide habitat for diverse assemblages of macroinvertebrates

Kelp forests along the southwestern and west coasts of South Africa, dominated by the species Ecklonia maxima and Laminaria pallida, are locally termed ‘the Great African Seaforest’. They form 3-dimensional biogenic habitats that provide 4 distinct microhabitats—canopy, fronds, stipe and holdfast—with the latter typically supporting the highest abundance and diversity of associated macroinvertebrates. The macrofauna inhabiting kelp holdfasts in South Africa have rarely been studied, resulting in a near complete lack of baseline data. In this study, macrobenthic assemblages from 40 E. maxima holdfasts were examined over 2 marine ecoregions and 4 locations. Macroinvertebrates were identified and counted for univariate and multivariate analyses using family-level data. A total of 120 families from 9 phyla were identified and were generally dominated by Arthropoda (48 families), Annelida (24 families) and Mollusca (23 families). Marine ecoregion had no significant effect on composition of macroinvertebrate assemblages, whereas location had a significant effect. There was no significant relationship between holdfast volume and macroinvertebrate diversity or abundance, suggesting that other environmental and physicochemical factors are important in determining community structure. This study serves as a baseline for future research aimed at understudied holdfast macroinvertebrate communities in the Great African Seaforest.

Eutrophication modifies the relationships between multiple facets of macroinvertebrate beta diversity and geographic distance in freshwater lakes

AbstractAimUnderstanding the distance–decay relationship (DDR) has been considered important because it reflects a combination of several ecological processes such as dispersal limitation and environmental sorting. However, effects of human disturbances on DDR are poorly known, especially in freshwater lakes. This study is aimed to examine how anthropogenic eutrophication modified the relationships between three facets (taxonomic, functional and phylogenetic) of macroinvertebrate beta diversity and geographic and environmental distances across 30 freshwater lakes.LocationThe Yangtze River floodplain, China.MethodsWe used Mantel tests to examine the relationships between multiple facets of assemblage dissimilarities (overall beta diversity, replacement and richness difference components) and geographic and environmental distances. Distance‐based redundancy analysis (dbRDA) and associated variation partitioning procedures were applied to explore the relative contributions of environmental and spatial factors on the three facets of beta diversity.ResultsWe found that none of the three beta diversity facets was related to geographic distance, but all were significantly related to environmental distance, mainly mirroring eutrophication‐related variables. Based on the variation partitioning approach, the macroinvertebrate assemblages examined were almost exclusively structured by environmental factors associated with eutrophication, while spatial variables had a negligible effect. Nevertheless, the different facets of beta diversity did not decrease (i.e., no homogenization trend) in lake groups showing the highest eutrophication levels, implying complex influences of anthropogenic disturbances in driving homogenization or differentiation in assemblage compositional dissimilarity.Main ConclusionsOur findings suggested that the high degrees of eutrophication acted as an environmental filter to significantly modify the spatial distance–decay relationships, possibly via decreasing the importance of dispersal limitation in shaping macroinvertebrate assemblages in the studied lakes. Given the sensitivity of beta diversity patterns to eutrophication we found in this study, we recommend that the role of anthropogenic disturbances should be incorporated into research on general ecological patterns like the DDR.

How do different modalities of land use practices impact the environmental features and macroinvertebrates? An assessment of mountain streams from Patagonia, Argentina

Agricultural intensification is a significant process, transforming the land and modifying stream water quality and biodiversity. Land-use practices are associated with substantial changes in vegetation structure, significant inputs of nutrients, erosion, and increased sedimentation, all of which profoundly impact aquatic biota and ecosystem functioning. The effect of different agricultural practices (horticulture, extensive and intensive livestock) on stream water quality was compared in terms of physicochemical features, bacteria, habitat condition, riparian ecosystem, and macroinvertebrate variables in a temperate rural landscape (Patagonia). The main objective was to identify which variables related to land use were determinants in the configuration of biotic communities. Significantly higher values in water temperature, conductivity, nutrients, and bacteria were found at intensively developed sites than at reference ones. The quality of the habitat and the riparian ecosystem had been profoundly modified. A multidimensional scaling analysis revealed that macroinvertebrate assemblages also differed among land use categories, with the variables: total phosphorous, total nitrogen, bacteria (E. coli, mesophilic and total coliforms), water temperature, and oxygen having the highest predictive power. Macroinvertebrate metrics (richness of EPT (Ephemeroptera+Plecoptera+Trichoptera), Plecoptera, shredders and scrapers, and the percentage of scrapers and collectors) proved appropriate bioindicators for discriminating intensive land use impacts and highlighted a trend of biodiversity loss. Plecoptera richness, a taxa group with a high level of endemism, responded significantly to habitat condition degradation. These results confirm that the intensification of land use leads to increased nutrient levels and suppressed aquatic-terrestrial interactions involved in the provision of allochthonous detrital input, shade, and habitat structure for larval stages and adults. The Habitat Condition Index appears to be a useful tool for rapid stream assessment and providing early warnings. Several ecological services are threatened in these Patagonian agroecosystems. Restoring riverbank heterogeneity and improving management practices that ameliorate nutrient and sediment inputs are crucial to enhance biodiversity.

The Impact Of Make Every Minute Count Classroom Management On The Activities Of Class IV Students

The present study reports the first comprehensive study on the freshwater macroinvertebrates and its habitat preferences in Bilah River, the largest riverin the Northern Sumatra. The riverside is characterized by the presence of anthropogenic and industrial activities which may alter the macroinvertebrate assemblage and biodiversity. Five moon 1, 2, 3 and 4 while group 2 consisted of station 5, 6, 7, 8, 9, and 10. Based on the diversity indices as ecological parameters, the habitat condition in Bilah River is categorized from low to moderately polluted. Spatial patterns in both environmental conditions affecting the macroinvertebrate assemblage was observed using canonical correspondence analysis (CCA) revealed the preferences from each macroinvertebrate species towards environmental conditions This study aims to find out: (1) Population variance of the two groups is the same or homogeneous, (2) Differences in average student learning outcomes, (3) The influence of class management Make Every Minute Count on student learning activity. This research is quantitative research using experimental methods and quasi-experimental design. The research population is the entire student at MI Taufiqurrahman 2 Kukusan which totaled 457 students. The sample technique used is purposive sampling. Research sample of 42 students consisting of class IV A 21 students (experimental) and IV B 21 students (kontrol). The data collection technique uses the lift as the primary instrument. From the test results the instrument obtained a Table R of 0.396 and Cronbach's Alpha of 0.836. The results analysis technique uses the t-test, which compares the two groups' rata-rata. The research findings indicate that: (1) Based on the information available, the significance level (Sig.) is less than 0.198 > 0.05, indicating a similar or homogenous population variation. (2) Based on results showing that the average learning time for the Afterwards Experiment (Make Every Minute Count) was 86,00 and the average deviation was 5,167, as well as the Average Learning Time for the Afterwards Control (Classroom Meeting) was 82,29 and the average deviation was 6,133. It may be observed that there are differences in student learning activity between the "Make Every Minute Count" and "Classroom Meeting" lesson plans. (3) Based on the Uji Wilcoxon results, Asymp.Sig. (2-Tailed) 0,000 < 0,05 or Ha is found. Thus, it is shown that there is a difference in the Make Every Minute Count staff's learning activity among fourth-grade students.

Impact of weirs in altering benthic macroinvertebrate assemblages and composition structure in the Luvuvhu River Catchment, South Africa

Stream flow weirs disrupt river flow regimes, physical conditions, and biological composition of rivers, posing significant threat to the river’s functionality, integrity, and sustainability. Home to diverse aquatic organisms, there is a lack of impact assessment of weirs on the stream of the Luvuvhu River Catchment (LRC). The aim of this study was to examine the impact of six weirs on aquatic macroinvertebrate assemblages and composition across five streams. A total of six sampling surveys on macroinvertebrates and physico-chemical parameters were conducted upstream and downstream of six weirs in 12 months between June 2021 and June 2022. The South African Scoring System score (SASS score) and Average Score per Taxon (ASPT) indices were used to compare organisms’ response between upstream and downstream of weirs. Generalized linear mixed models (GLMM) were used to determine the effect of physico-chemical variables on macroinvertebrate assemblage, while the CCA was employed to assess similarities between downstream and upstream sampling points across various sites. A total of 18,914 macroinvertebrate individuals were observed from 65 families during the survey. In upstream sections, the SASS score was driven by habitat integrity, electrical conductivity, and water depth, while ASPT responded significantly to habitat integrity, pH, dissolved oxygen and electrical conductivity. In the downstream sections, the SASS score increased with an increasing habitat integrity score and river width, while decreasing with elevation and pH levels. ASPT increased with increasing habitat integrity and elevation in the downstream sections, while decreasing with increasing river width and water temperature. This study’s findings suggest habitat integrity is largely driving aquatic abundance and assemblage in the LRC, and it is therefore important to maintain the ecological integrity of rivers.

Combined benthic and stream edge sampling better represent macroinvertebrate assemblages than benthic sampling alone along an aridity gradient

AbstractStudies of stream macroinvertebrates traditionally use sampling methods that target benthic habitats. These methods could underestimate biodiversity if important assemblage components exist outside of the benthic zone. To test the efficacy of different sampling methods, we collected paired reach‐wide benthic and edge samples from up to 10 study reaches in nine basins spanning an aridity gradient across the United States. Edge sampling targeted riparian‐adjacent microhabitats not typically sampled, including submerged vegetation, roots, and overhanging banks. We compared observed richness, asymptotic richness, and assemblage dissimilarity between benthic samples alone and different combinations of benthic and edge samples to determine the magnitude of increased diversity and assemblage dissimilarity values with the addition of edge sampling. We also examined how differences in richness and assemblage composition varied across an aridity gradient. The addition of edge sampling significantly increased observed richness (median increase = 29%) and asymptotic richness (median increase = 173%). Similarly, median Bray–Curtis dissimilarity values increased by as much as 0.178 when benthic and edge samples were combined. Differences in richness metrics were generally higher in arid basins, but assemblage dissimilarity either increased or decreased across the aridity gradient depending on how benthic and edge samples were combined. Our results suggest that studies that do not sample stream edges may significantly underestimate reach diversity and misrepresent assemblage compositions, with effects that can vary across climates. We urge researchers to carefully consider sampling methods in field studies spanning climatic zones and the comparability of existing data sets when conducting data synthesis studies.

Water‐level fluctuations and nutrient enrichment interact to alter ecosystem structure in distinct ways at different water depths

Abstract Aquatic ecosystems are often impacted by several human‐derived pressures simultaneously. A key challenge for ecologists is to develop mechanistic understanding of the cumulative effects of multiple stressors on freshwater biodiversity. We established an outdoor mesocosm experiment to examine the individual and combined effects of two key stressors on lake ecosystems globally—nutrient enrichment and amplified water‐level fluctuations—on benthic algal and macroinvertebrate assemblages along a gradient in littoral water depth. We found that nutrient enrichment and water‐level fluctuations not only altered the structure of littoral communities when acting individually, but also interacted to dynamically alter biomass and community structure in different ways at different depths. As expected, enrichment increased benthic algal biomass significantly in very shallow waters. Yet, when enrichment co‐occurred with water‐level fluctuations, this pattern was reversed, with algal biomass increasing significantly in deeper waters, but not in the shallows that were exposed to fluctuating water levels. This pattern occurred across all algal groups that we examined except for green algae. Green algae biomass increased with nutrient enrichment, was greatest in the shallows, and remained unaffected by fluctuating water levels. Water‐level fluctuations modified the functional feeding group structure of benthic macroinvertebrate communities, reducing relative densities of collector‐gatherers and increasing those of predators. However, these changes occurred only in the shallow‐most regions exposed directly to fluctuating water levels. Our results reveal how two globally important stressors of standing water systems can interact in different ways in different ecological contexts and show how stressors can combine to have unanticipated impacts that vary in space. Our findings underscore the potentially highly multifaceted and complex nature of stressor combinations that present a major and growing challenge to ecosystem management, particularly in light of accelerating global environmental change.

Influence of a protected riparian corridor on the benthic aquatic macroinvertebrate assemblages of a small northern Michigan (USA) agricultural stream

The biotic integrity of streams is frequently compromised by anthropogenic disturbance; thus, it is important to study the potential mitigating effects of undisturbed riparian zones on streams within disturbed watersheds. In this study, two first-order northern Michigan streams located 1 km apart in adjacent agricultural watersheds, but with differing riparian land use, were compared to observe the effects of intact forest within the immediate 100 m stream corridor. Both streams had high specific conductance values associated with agricultural streams. The stream with a primarily forested riparian corridor, however, had greater canopy cover, faster stream velocity, greater coarse substrate, lower percentage of organic sediment, lower water temperatures, higher dissolved oxygen, higher taxonomic richness, higher relative biomass of shredders, lower relative biomass of gathering collectors, and more pollution intolerant taxa than the stream with a primarily agricultural corridor. Moreover, the benthic macroinvertebrate assemblages were highly distinct from each other, with the riparian forested stream dominated by aquatic insects like mayflies and caddisflies, and the agricultural stream by non-emergent isopods and amphipods. These results demonstrate the effects of a buffer zone on stream substrate composition, water physicochemistry, and benthic assemblages, and indicate the importance of preserving riparian zones within agricultural watersheds.

Evaluating bottom-up forcing of a rocky intertidal resource harvest on a high trophic-level consumer group

The importance of ecosystem-based management (EBM) frameworks for resource harvest has increased over the past several decades as ecosystems face numerous anthropogenic stressors. In these frameworks, resource managers must consider the suite of interactions that comprise food webs and how resource harvest drives responses in non-target organisms. In rocky intertidal zones along North Atlantic coastlines, rockweed (Ascophyllum nodosum)—a canopy-forming brown seaweed—has been commercially harvested for centuries, yet most research on the effects of harvest have focused on the responses of the target resource and the macroinvertebrate assemblage. In this study, we used a Before-After Control-Impact experiment to assess the bottom-up effects of commercial rockweed harvest on a high trophic-level consumer group (birds) in Maine (USA). Overall, there was no evidence for strong bottom-up forcing of rockweed harvest on birds' site visitation. There was a small (fewer than two birds) positive effect size of harvest during the one-year post-harvest recovery interval. Several of the trends observed for the full bird assemblage appear to be driven more strongly by the low tide than the high tide bird assemblage. Independent of treatment, site visitation by birds was low in our study (60% of surveys recorded no birds) and highlights questions about the use of rocky intertidal habitats relative to other habitat types in coastal birds' home ranges. To our knowledge, there are no comparable assemblage-level bird studies in this system that can provide context to our results. Further research on coastal birds’ habitat use within home ranges and food-web connections with rockweed-associated macroinvertebrates is needed to more confidently incorporate this high trophic-level consumer group into an EBM framework for a rocky intertidal resource harvest.