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Pesticide use can impact not only cultivated land, but also protected ecosystems that receive pesticide inputs due to aquatic connectivity or atmospheric transport from agricultural regions. In Costa Rica's Caribbean lowlands, pesticides applied to banana and pineapple plantations are a potential source of pollution to ecological reserves. Macroinvertebrates and fish are both potentially useful bioindicators of agrochemical pollution in aquatic systems, and our goal was to determine whether three common stream consumer species (one fish and two aquatic insect species) could serve as bioindicators for the organophosphate pesticide ethoprophos. We identified thresholds at which ethoprophos impacts the survival (LC50) and observed behavior (LOEC – lowest observed effect concentration) for each species. The LC50 of the guppy Priapichthys annectens was 1530 µg/L, with observable behavioral changes occurring at 1000 µg/L. Insects were more sensitive: the mayfly Traverella holzenthali had an LC50 of 15 µg/L and an LOEC of 2.5 µg/L, and the caddisfly Leptonema sp. had an LC50 of approximately 30 µg/L and an LOEC of 5 µg/L. The LC50 values are notably higher than ambient concentrations recorded from polluted Costa Rican streams and suggest that these taxa are not ideal indicator species. However, the lower LOEC values (in the same order of magnitude as ambient concentrations) highlight the potential ecological importance of behavioral modification due to pesticides. Quantifying the thresholds at which common pesticides impact ecosystems is a key step in identifying bioindicator species and protecting tropical biodiversity. 

Abstract Disturbances can alter the structure and function of ecosystems. In stream ecosystems, changes in discharge and physicochemistry at short, intermediate, and long recurrence intervals can affect food webs and ecosystem processes. In this paper, we compare pH regimes in streams at La Selva Biological Station, Costa Rica, where episodic acidification frequency across the stream network varies widely due to buffering from inputs of bicarbonate‐rich interbasin groundwater. To examine the effects of acidification on ecosystem structure and function, we experimentally increased the buffering capacity of a headwater stream reach and compared it to an unbuffered upstream reach. We compared these reaches to a naturally buffered and unbuffered reaches of a second headwater stream. We quantified ecosystem structural (macroinvertebrate assemblages on leaf litter and coarse woody debris) and functional responses (leaf litter and coarse woody debris decomposition rates, and growth rates of a focal insect taxon [Diptera: Chironomidae]). Non‐metric multidimensional scaling and analysis of similarity revealed that macroinvertebrate assemblages were relatively homogenous across the four study reaches, although the naturally buffered reach was the most dissimilar. Ecosystem function, as measured by chironomid growth rates, was greater in the naturally buffered reach, while decomposition rates did not differ across the four reaches. Our results indicate that biological assemblages are adapted to pH regimes of frequently acidified stream reaches. Our experiment informs the effects on structure and function at short time scales in streams that experience moderate acidification, but larger magnitude acidification events in response to hydroclimatic change, as projected under climate change scenarios, may induce stronger responses in streams. 

ABSTRACT MotivationSNAPSHOT USA is an annual, multicontributor camera trap survey of mammals across the United States. The growing SNAPSHOT USA dataset is intended for tracking the spatial and temporal responses of mammal populations to changes in land use, land cover and climate. These data will be useful for exploring the drivers of spatial and temporal changes in relative abundance and distribution, as well as the impacts of species interactions on daily activity patterns. Main Types of Variables ContainedSNAPSHOT USA 2019–2023 contains 987,979 records of camera trap image sequence data and 9694 records of camera trap deployment metadata. Spatial Location and GrainData were collected across the United States of America in all 50 states, 12 ecoregions and many ecosystems. Time Period and GrainData were collected between 1st August and 29th December each year from 2019 to 2023. Major Taxa and Level of MeasurementThe dataset includes a wide range of taxa but is primarily focused on medium to large mammals. Software FormatSNAPSHOT USA 2019–2023 comprises two .csv files. The original data can be found within the SNAPSHOT USA Initiative in the Wildlife Insights platform.