Secondary Production Rates Research Articles

Enhancement of PM2.5 source appointment in a large industrial city of Korea by applying the elemental carbon tracer method for positive matrix factorization (PMF) model

The concentration of particulate matter with an aerodynamic diameter less than 2.5 μm (PM2.5) measured in an industrial area is strongly influenced by the industrial characteristics of the region. Ulsan, an industrial city in Korea, has a large regional impact on PM2.5 concentration because various industries, such as the petrochemical, automobile manufacturing, and shipbuilding, are located in this city. As such, the PM2.5 pollution sources must be identified to enable its management. In this study, PM2.5 source apportionment was conducted in Ulsan. In this process, the contribution to secondary organic formation was estimated considering the secondary organic carbon (SOC) calculated using the elemental carbon (EC) tracer method. Sources were classified into ten categories (i.e., coal-related, industry, sea salt, secondary sulfate, soil, oil combustion, secondary nitrate, traffic-related, SOC formation, and primary emission). Of these, secondary formation contributed approximately 71%. The high rate of secondary production seems to be influenced by the industry in the area. Contributions of secondary sulfate and secondary nitrate were related to the seasons, contributing to the most, in summer and winter, respectively. SOC formation was highest in spring, not summer, which seems to be due to the decrease in organic carbon (OC) concentration due to the washing effect of summer. The contribution of secondary formation in Ulsan was likely overestimated due to the influence of local sources. The positive matrix factorization (PMF) with SOC performed in this study can help to easily separate the PM2.5 sources of secondary formation and primary emissions.

Heavy snowfall event over the Swiss Alps: did wind shear impact secondary ice production?

Abstract. The change in wind direction and speed with height, referred to as vertical wind shear, causes enhanced turbulence in the atmosphere. As a result, there are enhanced interactions between ice particles that break up during collisions in clouds which could cause heavy snowfall. For example, intense dual-polarization Doppler signatures in conjunction with strong vertical wind shear were observed by an X-band weather radar during a wintertime high-intensity precipitation event over the Swiss Alps. An enhancement of differential phase shift (Kdp>1∘ km−1) around −15 ∘C suggested that a large population of oblate ice particles was present in the atmosphere. Here, we show that ice–graupel collisions are a likely origin of this population, probably enhanced by turbulence. We perform sensitivity simulations that include ice–graupel collisions of a cold frontal passage to investigate whether these simulations can capture the event better and whether the vertical wind shear had an impact on the secondary ice production (SIP) rate. The simulations are conducted with the Consortium for Small-scale Modeling (COSMO), at a 1 km horizontal grid spacing in the Davos region in Switzerland. The rime-splintering simulations could not reproduce the high ice crystal number concentrations, produced too large ice particles and therefore overestimated the radar reflectivity. The collisional-breakup simulations reproduced both the measured horizontal reflectivity and the ground-based observations of hydrometeor number concentration more accurately (∼20 L−1). During 14:30–15:45 UTC the vertical wind shear strengthened by 60 % within the region favorable for SIP. Calculation of the mutual information between the SIP rate and vertical wind shear and updraft velocity suggests that the SIP rate is best predicted by the vertical wind shear rather than the updraft velocity. The ice–graupel simulations were insensitive to the parameters in the model that control the size threshold for the conversion from ice to graupel and snow to graupel.

Toxicity and Starvation Induce Major Trophic Isotope Variation in Daphnia Individuals: A Diet Switch Experiment Using Eight Phytoplankton Species of Differing Nutritional Quality.

Stable isotope values can express resource usage by organisms, but their precise interpretation is predicated using a controlled experiment-based validation process. Here, we develop a stable isotope tracking approach towards exploring resource shifts in a key primary consumer species Daphnia magna. We used a diet switch experiment and model fitting to quantify the stable carbon (δ13C) and nitrogen (δ15N) isotope turnover rates and discrimination factors for eight dietary sources of the plankton species that differ in their cellular organization (unicellular or filamentous), pigment and nutrient compositions (sterols and polyunsaturated fatty acids), and secondary metabolite production rates. We also conduct a starvation experiment. We evaluate nine tissue turnover models using Akaike's information criterion and estimate the repetitive trophic discrimination factors. Using the parameter estimates, we calculate the hourly stable isotope turnover rates. We report an exceedingly faster turnover value following dietary switching (72 to 96 h) and a measurable variation in trophic discrimination factors. The results show that toxic stress and the dietary quantity and quality induce trophic isotope variation in Daphnia individuals. This study provides insight into the physiological processes that underpin stable isotope patterns. We explicitly test multiple alternative dietary sources and fasting and discuss the parameters that are fundamental for field- and laboratory-based stable isotope studies.

Life history and secondary production of Anomalocosmoecusilliesi Marlier, 1962 (Trichoptera, Limnephilidae) in a small stream in the northern Ecuadorian Paramo.

Life history of benthic faunas of tropical high-altitude cold environments are poorly studied. Here, monthly larval and adult data are presented for Anomalocosmoecusilliesi at Saltana Stream in Ecuador. In cold conditions throughout the year (6 °C), this species showed an asynchronous and continuous production. Larval density showed two peaks in August and April. All five larval instars were present in most months. Using the size-frequency method an annual rate of secondary production per biomass of 4.8 was calculated. The measured biomass was 785 mg/m2.

Nitrogen Source Matters: High NH4/NO3 Ratio Reduces Cannabinoids, Terpenoids, and Yield in Medical Cannabis.

The N form supplied to the plant, ammonium (NH4+) or nitrate (NO3–), is a major factor determining the impact of N nutrition on plant function and metabolic responses. We have hypothesized that the ratio of NH4/NO3 supplied to cannabis plants affects the physiological function and the biosynthesis of cannabinoids and terpenoids, which are major factors in the cannabis industry. To evaluate the hypothesis we examined the impact of five supply ratios of NH4/NO3 (0, 10, 30, 50, and 100% N-NH4+, under a uniform level of 200 mg L–1 N) on plant response. The plants were grown in pots, under controlled environment conditions. The results revealed high sensitivity of cannabinoid and terpenoid concentrations and plant function to NH4/NO3 ratio, thus supporting the hypothesis. The increase in NH4 supply generally caused an adverse response: Secondary metabolite production, inflorescence yield, plant height, inflorescence length, transpiration and photosynthesis rates, stomatal conductance, and chlorophyll content, were highest under NO3 nutrition when no NH4 was supplied. Ratios of 10–30% NH4 did not substantially impair secondary metabolism and plant function, but produced smaller inflorescences and lower inflorescence yield compared with only NO3 nutrition. Under a level of 50% NH4, the plants demonstrated toxicity symptoms, which appeared only at late stages of plant maturation, and 100% NH4 induced substantial plant damage, resulting in plant death. This study demonstrates a dramatic impact of N form on cannabis plant function and production, with a 46% decrease in inflorescence yield with the increase in NH4 supply from 0 to 50%. Yet, moderate levels of 10–30% NH4 are suitable for medical cannabis cultivation, as they do not damage plant function and show only little adverse influence on yield and cannabinoid production. Higher NH4/NO3 ratios, containing above 30% NH4, are not recommended since they increase the potential for a severe and fatal NH4 toxicity damage.

Assessment of the Factors Influencing Sulfur Dioxide Emissions in Shandong, China

Sulfur dioxide (SO2) is a serious air pollutant emitted from different sources in many developing regions worldwide, where the contribution of different potential influencing factors remains unclear. Using Shandong, a typical industrial province in China as an example, we studied the spatial distribution of SO2 and used geographical detectors to explore its influencing factors. Based on the daily average concentration in Shandong Province from 2014 to 2019, we explored the influence of the diurnal temperature range, secondary production, precipitation, wind speed, soot emission, sunshine duration, and urbanization rate on the SO2 concentration. The results showed that the diurnal temperature range had the largest impact on SO2, with q values of 0.69, followed by secondary production (0.51), precipitation (0.46), and wind speed (0.42). There was no significant difference in the SO2 distribution between pairs of sunshine durations, soot emissions, and urbanization rates. The meteorological factors of precipitation, wind speed, and diurnal temperature range were sensitive to seasonal changes. There were nonlinear enhancement relationships among those meteorological factors to the SO2 pollution. There were obvious geographical differences in the human activity factors of soot emissions, secondary production, and urbanization rates. The amount of SO2 emissions should be adjusted in different seasons considering the varied effect of meteorological factors.

Warming alters the metabolic rates and life-history parameters of Ceriodaphnia silvestrii (Cladocera).

Temperature rise has effects on the metabolic process of organisms, population structure, and ecosystem functioning. Here, we tested the effects of warming on the metabolic rates and life-history parameters of the widespread cladoceran Ceriodaphnia silvestrii. Two scenarios of global warming were established, an increase of 2 °C and an increase of 4 °C; the control temperature was 22°C. Our results showed that warming altered C. silvestrii metabolic rates, by increasing the rates of assimilation and secondary production, and decreasing the rates of filtration and ingestion. Warming also increased C. silvestrii fecundity and the body size of neonates and juveniles, and decreased the embryonic and post-embryonic time of development. C. silvestrii might be an important food resource at intermediary temperature as it had higher assimilation rates, even filtering fewer algae. At the highest temperature, we observed a substantial decrease in assimilation and secondary production, which could be a sign of stress starting. The increase in temperature by global warming will affect the cladocerans' metabolic processes and the population survival, even a small increase (2°C) might induce drastic fluctuations in such processes and affect the carbon and energy availability inside aquatic food-webs.

Quantifying epifaunal secondary production within tropical macroalgal meadows: Seasonality and sensitivity to canopy structure

AbstractSecondary production connects primary producers with higher‐order consumers. The response of secondary production to seasonal variation in primary producers can influence trophic flows that underpin key ecosystem functions and services. Within the canopy‐forming macroalgal meadows of Ningaloo Reef, Western Australia, we quantified the secondary production generated by Sargassum‐associated epifauna across seasons and seascapes. We found a strong positive correlation between overall epifaunal production and Sargassum canopy size. Variation in epifaunal production was predominantly driven by seasonal changes in Sargassum canopy size. However, these seasonal effects were not uniform across the seascape. Key predictors of spatial and temporal variation in epifaunal production were the presence of invertivorous fish families, as well as daily and monthly fluctuations in sea temperature. Areal estimates of epifaunal productivity were much higher in summer than in winter, due to higher Sargassum canopy size and percent cover in summer. Epifaunal production was estimated to be more sensitive to Sargassum percentage cover than to canopy height. Modeling a 45% reduction in canopy height and percent cover of Sargassum associated with a marine heatwave event revealed a potential 81% drop in the areal rate of secondary production by Sargassum epifauna in this tropical fringing reef ecosystem. Disturbances to Sargassum canopy structure driven by global change can therefore significantly alter the productivity of these tropical macroalgal meadows and their ability to support higher level consumers within the food web, including important fisheries species. Our results highlight the importance of including epifaunal production estimates in predictive modeling when managing macroalgal‐dominated marine ecosystems.

Plankton community composition and productivity near the Subantarctic Prince Edward Islands archipelago in autumn

The Subantarctic Ocean is a sink for atmospheric CO2, largely due to its biological pump, which is enhanced by the influence of the Subantarctic islands on the plankton ecosystem (the so‐called “island mass effect”). The influence of the Prince Edward Islands archipelago in the Indian Subantarctic on the surrounding hydrography and benthos has been well studied; however, over the last two decades, little attention has been paid to the functioning and productivity of its plankton ecosystem. Here, we present the first measurements of primary production at the archipelago in over 20 years and the first‐ever rates of secondary production, interpreted in the context of hydrographic, biogeochemical, and plankton community composition data. In autumn 2017, after the late‐summer bloom, nanophytoplankton dominated the near‐island waters and regenerated nutrients fuelled 76% of phytoplankton growth. Primary production and carbon export potential (inferred from nitrate uptake) reached a local maximum in the inter‐island region, which we attribute to water‐mass retention and stratification over the inter‐island plateau (a manifestation of the island mass effect). We observed a diverse mesozooplankton community, likely a remnant of the late‐summer bloom rather than representing the consumers feeding on the in situ (nano)phytoplankton. We estimate that even after the decay of the late‐summer bloom, roughly a quarter of the planktonic carbon was potentially exportable. This finding implies that the archipelago's upper‐ocean ecosystem sequesters atmospheric CO2 at least through autumn despite high rates of recycling and inefficient trophic transfer, thereby contributing to the island mass effect‐associated strengthening of the Subantarctic Ocean's biological pump.

Physical and Chemical Evolution of Lunar Mare Regolith

AbstractThe lunar landscape evolves both physically and chemically over time due to impact cratering and energetic processes collectively known as space weathering. Despite returned soil samples and global remote sensing reflectance measurements, the rate of space weathering in the lunar regolith is not well understood. To address this, we developed a novel three‐dimensional landscape evolution model to simulate the physical processes that control the burial, excavation, and transport of regolith on airless bodies. Applying this model to the lunar mare, we find that over billions of years of surface evolution, material typically spends only a few million years on the surface where it is exposed to the effects of space weathering. The small surface residence times are a result of vigorous mixing by small‐scale impacts, predominantly driven by secondary crater formation. We deduce the rate of space weathering by comparing our modeled distribution of surface residence times on the lunar mare to measurements of space weathering maturity from Apollo soil samples and orbital surface reflectance datasets. These chemical constraints indicate that soil on the lunar mare reaches maturity in 7 Myr of cumulative surface exposure though due to uncertainties in the rate of small secondary crater production, this timescale could be 2–3 times higher. Weathering progresses more rapidly upon initial exposure to space but the surface residence time required to achieve maturity is realized over billions of years as regolith is repeatedly buried and exposed by small impacts.

Composition, biomass and secondary production of the macrobenthic invertebrate assemblage in a mangrove forest in Nayband Bay, Persian Gulf

Nayband Bay is a unique protected area located on the Iranian coast of the Persian Gulf. The bay supports a diverse macrobenthic assemblage; studying the biomass and secondary production of such a habitat can offer insights into the ecosystem’s patterns and processes. In total, 18 benthic sampling sites were taken from six sites along the bay between May 2016 and February 2017. Macrozoobenthos assemblages comprised 60 taxa; among them, gastropods accounted for much of the overall biomass and secondary production. The mean annual biomass of macrobenthos was found to be 1974.68 mg AFDW m−2, while the secondary production was 8.04 mg m−2 y−1. Secondary production values appeared to increase during winter (14.21 mg m−2 day−1) and decrease in spring (4.59 mg m−2 day−1); such seasonal differences were primarily dependent on the presence of different groups of macrobenthos. The annual mean production-to-biomass (P/B) ratio was 6.93, a value that increased from cold seasons to warm seasons. This means that in summer and spring, polychaetes (with smaller species) were the dominant group of macrobenthos. Conversely, in winter, gastropods and crustaceans (with large species) were the dominant group and increased macrobenthic production. High temperature and drought were the main reasons for the decreased density of macrobenthos during the warm seasons. However, a significant reduction in the abundance of macrobenthos was also observed in areas where road construction prevented direct contact between the mangrove trees and the marine tidal system. This could explain the deficient levels of biomass and secondary production among the macrobenthos groups in the area. The results of this study indicate that human activities, like construction, in mangrove forests can reduce both the density of macrobenthos and their rates of secondary production. Therefore, proper management is essential to sustainable anthropogenic development in mangrove forests.

Ocean acidification modifies the impact of warming on sediment nitrogen recycling and assimilation by enhancing the benthic microbial loop

Nitrogen that has been recycled in the benthos supports high rates of primary and secondary production in estuaries. However, little is known about the effect of future climate on benthic nitrogen recycling and assimilation. An ex situ core incubation was used to assess the impact of combinations of warming (8°C range) and ocean acidification (OA) (i.e. increased pCO2 and decreased pH) on ammonium (NH4+) and nitrate/nitrite (NOx) fluxes and 15N-nitrate assimilation in shallow unvegetated estuarine sediments. Dissolved inorganic nitrogen (DIN = NH4+ + NOx) fluxes were significantly affected by the interaction of warming and OA, highlighting the importance of considering combined stressor treatments when investigating ecosystem responses to future climates. Warming alone increased DIN efflux from the sediments. At current mean ambient temperatures (23°C) and below (Δ-3°C), OA significantly increased DIN effluxes, but there was little to no effect of OA on DIN fluxes at warmer temperatures (Δ+3°C and Δ+5°C). OA reduced the 15N assimilation/retention of the sediments across all temperatures, suggesting that nitrogen retention in bacterial biomass was reduced, despite OA also increasing primary productivity. As such, under the projected future climate of ~3°C warming and doubling of pCO2 (~1000 µatm), unvegetated estuarine sediments are likely to have a more rapid turnover of DIN driven by greater microphytobenthos production and recycling.

Population Dynamics and Secondary Production of the Invasive Bivalve Mytilopsis leucophaeata (Bivalvia, Dreissenidae) in Lagoa Rodrigo De Freitas, Rio De Janeiro, Brazil

The dark false mussel Mytilopsis leucophaeata is an invasive bivalve known from two locations in Rio de Janeiro (Brazil): Lagoa Rodrigo de Freitas and Lagoa de Marapendi. For a population biology study of this species, monthly collections were carried out at Lagoa Rodrigo de Freitas over a period of 2 y (March 2016–March 2018). High densities were registered in both studied years: 84,560 (±22,066) ind. m–2 in the first year and 65,848 (±7,830) in the second year. Growth was lower for the first year (K = 0.4 for year 1 and K = 0.8 for year 2), whereas seasonal oscillation (C = 0.6) was of the same intensity in both years. The period of lower growth differed for the years, occurring in June (WP = 0.5) in the first year and in August (WP = 0.7) in the second year. The maximum and asymptotic lengths, longevity, secondary production, biomass, and turnover rate were higher for the first year; on the other hand, mortality was higher at the second year. Density of the invasive mussel was significantly and positively related with salinity (r2 = 0.5547; P < 0.0001). In a general way, the second year of study seems to be a more adverse period for the population of the invasive mussel with reduced density, body sizes, life expectancy, secondary production, biomass, and higher mortality. Among environmental factors, salinity seems to exert the strongest influence on the regulation of population attributes.

Changing Distributions of Zooplankton Communities in a Coastal Lagoon in Response to Rainfall Seasonality

Choi, J.-Y.; Kim, J.-C., and Kim, S.-K, 2020. Changing distributions of zooplankton communities in a coastal lagoon in response to rainfall seasonality. In: Jung, H.-S.; Lee, S.; Ryu, J.-H., and Cui, T. (eds.), Advances in Geospatial Research of Coastal Environments. Journal of Coastal Research, Special Issue No. 102, pp. 69-74. Coconut Creek (Florida), ISSN 0749-0208.Coastal lagoons are unique and complex ecosystems which exhibit very high primary and secondary production rate, and their productivity is underpinned by plankton communities. Empirical studies suggest that summer rainfall determines the spatial and temporal pattern of not only physicochemical variables but also zooplankton communities in coastal regions. It was hypothesized that drier or wetter than average summer rainfall years would change the environmental variables (e.g., salinity, dissolve oxygen, and nutrients) in coastal lagoons, thereby disrupting the spring growth trend of zooplankton communities. Long-term (2014–2017) monitoring data (rainfall, environmental variables, and zooplankton) were divided into two groups: Rainy and Dry years, corresponding to years with an annual rainfall that was higher or lower than the total annual average, respectively. The results showed that summer and autumn densities of zooplankton fell sharply in Rainy years but increased steadily in Dry years. The highest density of rotifers was mainly observed in sites adjacent to the inflow of tributary streams, while copepods were abundant near the outlet to the ocean. The differing spatial distribution of rotifers and copepods is attributed to the salinity gradient in the study site, and changed with freshwater inflows. Based on these findings, it is suggested that summer rainfall variations play an important role in driving the spatial and temporal distribution of zooplankton.

SECONDARY PRODUCTION OF Scolelepis goodbodyi (POLYCHAETA: SPIONIDAE) IN A TROPICAL SANDY BEACH IN THE SOUTHWESTERN ATLANTIC, BRAZIL

The secondary production is the result of the functional response of populations subject to various environmental factors. Marine habitats vary in terms of quantity and quality of food supply, and the use of secondary production values, as well as renewal rates (P/B), may be used as estimates for understanding the incorporation of organic matter and energy per unit, population or community in each area. This estimative was performed for the population of Scolelepis goodbodyi in a tropical beach in the Southwestern Atlantic, located in an upwelling area. A comparison of Spionidae and non-spionid populations from different latitudes was also done. The Mass Specific Growth Rate method (MSGR) and the Production/Biomass ratio (P/B) were used to estimate the somatic annual production and average annual biomass. The mean density and biomass were 16.38 ind. m-2 and 2.78 g AFDW m-2,respectively. The secondary production and P/B were 8.3 g AFDW m-2 y-1 and 2.98 y1, respectively. The growth rate in weight was greater for the small size than the large size classes. The largest individuals (W3C = 1.0 mm) showed the lowest biomass and secondary production values. The observed high rates of secondary production and P/B suggest that this S. goodbodyi population can transfer large amounts of biomass to higher trophic levels of the local food web. Studies of the secondary production of spionidae populations in different latitudes, including the population of S. goodbodyi in the beach of Manguinhos, showed variability in their rates probably due to the differences of several factors such as life history and environmental variability

Analysis of Multi-scale Spatio-temporal Differentiation Characteristics of PM2.5 in China from 2011 to 2017

It is of great significance for joint prevention and control of air pollution to understand the spatial and temporal differentiation characteristics and regional driving factors of PM2.5 in China. In this study, from a multi-scale perspective, the spatial pattern analysis and geographical detectors are used to explore the spatial and temporal distribution pattern and causes of PM2.5 pollution in China mainland from 2011 to 2017. The results show that:① the annual average PM2.5 concentration is relatively stable from 2011 to 2017, and there is no obvious trend. The change characteristics of regional PM2.5 are similar to those of national PM2.5, showing a "W" shaped fluctuation. Overall, the order of pollution degree from high to low is:central, eastern, western, and northeastern. ② From the spatial pattern analysis results, we can see that the high-value cluster mainly appears in east China, middle China, and southwest of Xinjiang, while the low-value cluster appears in Qinghai-Tibet, Yunnan, Guizhou, Plateau, and Daxinganling regions. ③ The results of geographic detector analysis show that the population factor is the leading factor nationally; meanwhile, the industrial, energy consumption, and traffic factors all contribute to the distribution pattern of PM2.5 in varying degrees. Regionally, besides the population factor, the proportion of secondary production and urban green space rate have the greatest impact on the northeast, the industrial smoke and dust and road area in the east, and the total industrial electricity and buses in the central area. The impact of social and economic factors does not significantly affect the PM2.5 in the western region.

Zooplankton functional group responses to environmental drivers off the west coast of Vancouver Island, Canada

Zooplankton diversity and biomass are integral to marine ecosystem functioning. Functional trait-based approaches enable an examination of ecosystem dynamics in which species groups are defined by their functional roles (i.e. functional groups) within the ecosystem, rather their taxonomic identity. Changes in the relative and absolute biomass of zooplankton functional groups may affect the productivity of higher trophic levels via change in secondary production rates and the efficiency of energy transfer. Traits from 55 mesozooplankton species were assembled from the literature and applied to a 35-year time series (1980–2016) for the southern shelf area off the west coast of Vancouver Island, Canada. Eight functional groups were identified by clustering species on the basis of functional trait similarity. A time series of biomass anomalies was calculated for each functional group, after which links between functional group biomass anomalies and several environmental variables were examined. Generalized additive modeling (GAM) identified local sea surface temperature as the most important driver of biomass anomaly patterns for three groups: Doliolids, Omnivore-Herbivores, and the Active Ambush Omnivores. The Southern Oscillation Index (SOI) was also a main driver for three groups: Egg-Brooding Carnivores, Broadcast Carnivores, and Cruise Carnivores-A. The Ocean Niño Index (ONI) was significant for Active Ambush Omnivores and Egg-Brooding Carnivores, whereas the Pacific Decadal Oscillation (PDO) was a driver of Broadcast Carnivores and Cruise Carnivores-A. The Doliolids group also varied with surface salinity, and Cruise Carnivores-B with the North Pacific Gyre Oscillation (NPGO). The relative contribution of several zooplankton functional groups to the overall biomass showed no temporal trends but some groups had increased or decreased abundance contributions. This suggests functional redundancy within groups, as smaller or larger species may dominate based on environmental conditions. Our analysis demonstrates that functional group biomass anomalies vary with environmental variables, where conditions may favor certain functional groups, therefore dictating how the ecosystem is functioning.

Contrasting responses of black fly species (Diptera: Simuliidae) to experimental whole‐stream warming

Abstract As global temperatures continue to rise, assessment of how species within ecological communities respond to shifts in temperature has become increasingly important. However, such assessments require detailed long‐term observations or ecosystem‐level manipulations that allow for interactions among species and the potential for species dispersal and exchange with the regional species pool. We examined the effects of experimental whole‐stream warming on a larval black fly assemblage in southwest Iceland. We used a paired‐catchment design, in which we studied the warmed stream and a nearby reference stream for 1 year prior to warming and 2 years during warming and estimated population abundance, biomass, secondary production, and growth rates for larvae of three black fly species. Experimental warming by 3.8°C had contrasting effects on the three black fly species in the assemblage. The abundance, biomass, growth, and production of Prosimulium ursinum decreased in the experimental stream during the warming manipulation. Despite increasing in the reference stream, the abundance, biomass, and production of another species, Simulium vernum, decreased in the experimental stream during warming. In contrast, warming had an overall positive effect on Simulium vittatum. While warming had little effect on the growth of overwintering cohorts of S. vittatum, warming led to an additional cohort during the summer months and increased its abundance, biomass, and production. Overall, family‐level production was enhanced by warming, despite variation in species‐level responses. Our study illustrates that the effects of climate warming are likely to differ even among closely related species. Moreover, our study highlights the need for further investigation into the uneven effects of warming on individual species and how those variable effects influence food web dynamics and ecosystem function.

Species dynamics and interactions via metabolically informed consumer-resource models

Quantifying the strength, sign, and origin of species interactions, along with their dependence on environmental context, is at the heart of prediction and understanding in ecological communities. Pairwise interaction models like Lotka-Volterra provide an important and flexible foundation, but notably absent is an explicit mechanism mediating interactions. Consumer-resource models incorporate mechanism, but describing competitive and mutualistic interactions is more ambiguous. Here, we bridge this gap by modeling a coarse-grained version of a species’ true cellular metabolism to describe resource consumption via uptake and conversion into biomass, energy, and byproducts. This approach does not require detailed chemical reaction information, but it provides a more explicit description of underlying mechanisms than pairwise interaction or consumer-resource models. Using a model system, we find that when metabolic reactions require two distinct resources we recover Liebig’s Law and multiplicative co-limitation in particular limits of the intracellular reaction rates. In between these limits, we derive a more general phenomenological form for consumer growth rate, and we find corresponding rates of secondary metabolite production, allowing us to model competitive and non-competitive interactions (e.g., facilitation). Using the more general form, we show how secondary metabolite production can support coexistence even when two species compete for a shared resource, and we show how differences in metabolic rates change species’ abundances in equilibrium. Building on these findings, we make the case for incorporating coarse-grained metabolism to update the phenomenology we use to model species interactions.

Bacterial production prevails over photo- and chemosynthesis in a eutrophic tropical lagoon

Dark carbon fixation is a combination of processes performed by microorganisms to fix inorganic carbon driven the energy generated by chemical reactions. Our study quantified microbial primary and secondary production rates to evaluate the relative importance of dark carbon fixation in relation to photosynthetic rates and heterotrophic bacterial production and their contribution to the carbon cycle in a tropical eutrophic and human-impacted lagoon (Rodrigo de Freitas Lagoon, Brazil). Samples were collected daily at a fixed point to assess short-term temporal variations and at six different stations to assess spatial variability. Water samples were incubated using 14C-bicarbonate at 100% of light and in the dark to quantify photosynthesis and dark carbon fixation, respectively; and 3H-leucine incubations were performed to measure bacterial production. Environmental parameters (temperature, salinity, dissolved oxygen, dissolved organic carbon and inorganic nutrients) were measured to characterize the hydrology of the studied area, and to evaluate their influence on the microbial production rates. There were no significant changes in production rates over time or within different depths. Bacterial production rates varied significantly over space, and were correlated with nitrogen compounds, temperature, salinity and pH. However, a short rainfall event, although not strong or extreme, promoted rapid changes in the shallow water column, such as a decrease in temperature and nitrogen compounds, inducing responses to microbial production rates, such as higher rates of dark carbon fixation and bacterial production at the bottom and lower rates of photosynthesis. Heterotrophic bacterial production was significantly higher than dark and light carbon fixation, being the most important carbon-cycling process in Rodrigo de Freitas Lagoon, possibly favored by the high allochthonous organic matter and nutrient inputs. This study showed that, on average, dark carbon fixation accounted for 30% at the surface and 43% near the bottom of the total primary production and up to 10% of heterotrophic production in the water column, which may be related to the availability of ammonia and methane. We concluded that, even for this short-term temporal and spatial assessment, dark carbon fixation is relevant, although usually disregarded, and this process should be taken into account when evaluating carbon budgets, metabolic balance and ecosystem functioning in tropical coastal lagoons.