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Drier and hotter conditions linked with anthropogenic climate change can increase wildfire frequency and severity, influencing terrestrial and aquatic carbon cycles at broad spatial and temporal scales. The impacts of wildfire are complex and dependent on several factors that may increase terrestrial deposition and the influx of dissolved organic matter (DOM) from plants into nearby aquatic systems, resulting in the darkening of water color. We tested the effects of plant biomass quantity and its interaction with fire (burned vs. unburned plant biomass) on dissolved organic carbon (DOC) concentration and degradation (biological vs. photochemical) and DOM composition in 400 L freshwater ponds using a gradient experimental design. DOC concentration increased nonlinearly with plant biomass loading in both treatments, with overall higher concentrations (>56 mg/L) in the unburned treatment shortly after plant addition. We also observed nonlinear trends in fluorescence and UV-visible absorbance spectroscopic indices as a function of fire treatment and plant biomass, such as greater humification and specific UV absorbance at 254 nm (a proxy for aromatic DOM) over time. DOM humification occurred gradually over time with less humification in the burned treatment compared to the unburned treatment. Both burned and unburned biomass released noncolored, low molecular weight carbon compounds that were rapidly consumed by microbes. DOC decomposition exhibited a unimodal relationship with plant biomass, with microbes contributing more to DOC loss than photodegradation at intermediate biomass levels (100-300 g). Our findings demonstrate that the quantity of plant biomass leads to nonlinear responses in the dynamics and composition of DOM in experimental ponds that are altered by fire, indicating how disturbances interactively affect DOM processing and its role in aquatic environments.

Long-term monitoring of individual coral colonies is important for understanding variability between and within species over time in the context of thermal stress. Here, we analyze an 11-year time series of permanent benthic photoquadrats taken on Palmyra Atoll, central Pacific, from 2009 to 2019 to track the growth (i.e., increase in live planar area), pigmentation or lack thereof ("discoloration"), partial or whole-colony mortality, survival, and regrowth of 314 individual coral colonies of nine focal species from two reef habitat types. During this period, thermal anomalies occurred on Palmyra in conjunction with El Niño-Southern Oscillation events in both 2009 and 2015, of which the latter heatwave was longer-lasting and more thermally-severe. We found that coral responses varied by habitat, within and among species, and/or according to the degree of accumulated thermal stress. Nearly all species, particularly Stylophora pistillata and Pocillopora damicornis, responded more negatively to the 2015 heatwave in terms of colony-specific discoloration and reduction in live planar area. While discoloration was more prominent at the shallower reef terrace compared to the fore reef for this subset of colonies, the reef terrace exhibited greater stability of community-wide coral cover. Colony fate was associated with severity of discoloration at the time of warming: one year following the 2009 heatwave, more severely discolored colonies were more likely to grow, yet following the second heatwave in 2015, colonies were more likely to experience shrinkage or mortality. However, colonies that were more severely discolored in 2009 were not necessarily more discolored in 2015, suggesting that colony-specific factors may be more influential in governing responses to thermal stress. [ABSTRACT FROM AUTHOR]

Many tropical corals have declined in abundance in the last few decades, and evaluating the causal basis of these losses is critical to understanding how coral reefs will change in response to ongoing environmental challenges. Motivated by the likelihood that marine environments will become increasingly unfavorable for coral growth as they warm and become more acidic (i.e., ocean acidification), it is reasonable to evaluate whether specific phenotypic traits of the coral holobiont are associated with ecological success (or failure) under varying environmental conditions including those that are adverse to survival. Initially, we asked whether it was possible to identify corals that are resistant or sensitive to such conditions by compiling quantitative measures of their phenotypic traits determined through empirical studies, but we found only weak phenotypic discrimination between ecological winners and losers, or among taxa. To reconcile this outcome with ecological evidence demonstrating that coral taxa are functionally unequal, we looked beyond the notion that phenotypic homogeneity arose through limitations of empirical data. Instead, we examined the validity of contemporary means of categorizing corals based on ecological success. As an alternative means to distinguish among functional groups of corals, we present a demographic approach using integral projection models (IPMs) that link organismal performance to demographic outcomes, such as the rates of population growth and responses to environmental stress. We describe how IPMs can be applied to corals so that future research can evaluate within a quantitative framework the extent to which changes in physiological performance influence the demographic underpinnings of ecological performance.

Fire can lead to transitions between forest and grassland ecosystems and trigger positive feedbacks to climate warming by releasing CO2 into the atmosphere. Climate change is projected to increase the prevalence and severity of wildfires. However, fire effects on the fate and impact of terrestrial organic matter (i.e., terrestrial subsidies) in aquatic ecosystems are unclear. Here, we performed a gradient design experiment in freshwater pond mesocosms adding 15 different amounts of burned or unburned plant detritus and tracking the chronology of detritus effects at 10, 31, 59, and 89 days. We show terrestrial subsidies had time‐ and mass‐dependent, non‐linear impacts on ecosystem function that influenced dissolved organic carbon (DOC), ecosystem metabolism (net primary production and respiration), greenhouse gas concentrations (carbon dioxide [CO2], methane [CH4]), and trophic transfer. These impacts were shifted by fire treatment. Burning increased the elemental concentration of detritus (increasing %N, %P, %K), with cascading effects on ecosystem function. Mesocosms receiving burned detritus had lower [DOC] and [CO2] and higher dissolved oxygen (DO) through Day 59. Fire magnified the effects of plant detritus on aquatic ecosystem metabolism by stimulating photosynthesis and respiration at intermediate detritus‐loading through Day 89. The effect of loading on DO was similar for burned and unburned treatments (Day 10); however, burned‐detritus in the highest loading treatments led to sustained hypoxia (through Day 31), and long‐term destabilization of ecosystem metabolism through Day 89. In addition, fire affected trophic transfer by increasing autochthonous nitrogen source utilization and reducing the incorporation of 15N‐labeled detritus into plankton biomass, thereby reducing the flux of terrestrial subsidies to higher trophic levels. Our results indicate fire chemically transforms plant detritus and alters the role of aquatic ecosystems in processing and storing carbon. Wildfire may therefore induce shifts in ecosystem functions that cross the boundary between aquatic and terrestrial habitats. [ABSTRACT FROM AUTHOR]

Deforestation and subsequent land-use conversion has altered ecosystems and led to negative effects on biodiversity. To ameliorate these effects, nitrogen-fixing (N2-fixing) trees are frequently used in the reforestation of degraded landscapes, especially in the tropics; however, their influence on ecosystem properties such as nitrogen (N) availability and carbon (C) stocks are understudied. Here, we use a 30-y old reforestation site of outplanted native N2-fixing trees (Acacia koa) dominated by exotic grass understory, and a neighboring remnant forest dominated by A. koa canopy trees and native understory, to assess whether restoration is leading to similar N and C biogeochemical landscapes and soil and plant properties as a target remnant forest ecosystem. We measured nutrient contents and isotope values (δ15N, δ13C) in soils, A. koa, and non-N2-fixing understory plants (Rubus spp.) and generated δ15N and δ13C isoscapes of the two forests to test for (1) different levels of biological nitrogen fixation (BNF) and its contribution to non-N2-fixing understory plants, and (2) the influence of historic land conversion and more recent afforestation on plant and soil δ13C. In the plantation, A. koa densities were higher and foliar δ15N values for A. koa and Rubus spp. were lower than in the remnant forest. Foliar and soil isoscapes also showed a more homogeneous distribution of low δ15N values in the plantation and greater influence of A. koa on neighboring plants and soil, suggesting greater BNF. Foliar δ13C also indicated higher water use efficiency (WUEi) in the plantation, indicative of differences in plant-water relations or soil water status between the two forest types. Plantation soil δ13C was higher than the remnant forest, consistent with greater contributions of exotic C4-pasture grasses to soil C pools, possibly due to facilitation of non-native grasses by the dense A. koa canopy. These findings are consequential for forest restoration, as they contribute to the mounting evidence that outplanting N2-fixing trees produces different biogeochemical landscapes than those observed in reference ecosystems, thereby influencing plant-soil interactions which can influence restoration outcomes. [ABSTRACT FROM AUTHOR]

Introduction Ocean acidification (OA) caused by the dissolution of atmos[pH.sub.e]ric pC[O.sub.2] in seawater is a serious threat to marine life (Hoegh-Guldberg et al., 2007). Of the many taxa likely to [...], Early life stages of the coral Seriatopora caliendrum were used to test the hypothesis that the depression of dark respiration in coral recruits by high pC[O.sub.2] is caused by perturbed protein metabolism. First, the contribution of protein anabolism to respiratory costs under high pC[O.sub.2] was evaluated by measuring the aerobic respiration of S. caliendrum recruits with and without the protein synthesis inhibitor emetine following 1 to 4 days at 45 Pa versus 77 Pa pC[O.sub.2]. Second, protein catabolism under high pC[O.sub.2] was evaluated by measuring the flux of ammonium (N[H.sub.4.sup.+]) from juvenile colonies of S. caliendrum incubated in darkness at 47 Pa and 90 Pa pC[O.sub.2]. Two days after settlement, respiration of recruits was affected by an interaction between emetine and pC[O.sub.2], with emetine reducing respiration 63% at 45 Pa pC[O.sub.2] and 27% at 77 Pa pC[O.sub.2]. The interaction disappeared 5 days after settlement, when respiration was reduced 27% by emetine under both pC[O.sub.2] conditions. These findings suggest that protein anabolism accounted for a large proportion of metabolic costs in coral recruits and was affected by high pC[O.sub.2], with consequences detected in aerobic respiration. Juvenile S. caliendrum showed net uptake of N[H.sub.4.sup.+] at 45 Pa pC[O.sub.2] but net release of N[H.sub.4.sup.+] at 90 Pa pC[O.sub.2], indicating that protein catabolism, N[H.sub.4.sup.+] recycling, or both were affected by high pC[O.sub.2]. Together, these results are consistent with the hypothesis that high pC[O.sub.2] affects protein metabolism in corals.

To evaluate the effects of temperature and pC[O.sub.2] on coral larvae, brooded larvae of Pocillopora damicornis from Nanwan Bay, Taiwan (21[degrees]56.179'N, 120[degrees]44.85'E), were exposed to ambient (419-470 [micro]atm) and high (604-742 [micro]atm) pC[O.sub.2] at ~25 and ~29[degrees]C in two experiments conducted in March 2010 and March 2012. Larvae were sampled from four consecutive lunar days (LD) synchronized with spawning following the new moon, incubated in treatments for 24 h, and measured for respiration, maximum photochemical efficiency of PSII ([F.sub.v]/[F.sub.m]), and mortality. The most striking outcome was a strong effect of time (i.e., LD) on larvae performance: respiration was affected by an LD x temperature interaction in 2010 and 2012, as well as an LD x pC[O.sub.2] x temperature interaction in 2012; [F.sub.v]/[F.sub.m] was affected by LD in 2010 (but not 2012); and mortality was affected by an LD x pC[O.sub.2] interaction in 2010, and an LD x temperature interaction in 2012. There were no main effects of pC[O.sub.2] in 2010, but in 2012, high pC[O.sub.2] depressed metabolic rate and reduced mortality. Therefore, differences in larval performance depended on day of release and resulted in varying susceptibility to future predicted environmental conditions. These results underscore the importance of considering larval brood variation across days when designing experiments. Subtle differences in experimental outcomes between years suggest that transgenerational plasticity in combination with unique histories of exposure to physical conditions can modulate the response of brooded coral larvae to climate change and ocean acidification., Introduction Tropical coral reefs are threatened by global climate change (GCC) and ocean acidification (OA), with large numbers of corals killed by bleaching since the 1980s (Hoegh-Guldberg 1999), and the [...]

Introduction Coral reefs are threatened by natural and anthropogenic factors, including global climate change and ocean acidification (OA) (Hoegh-Guldberg et al., 2007; Wilkinson, 2008). OA poses a particularly severe threat, [...], . Juvenile colonies of massive Porites spp. were exposed to manipulated pH and bicarbonate ([HC[O.sub.3.sup.-]]) in situ to test the hypothesis that ocean acidification (OA) does not affect respiration and calcification. Incubations lasted 28 h and exposed corals to ambient temperature and light with ecologically relevant water motion. Three treatments were applied: (1) ambient conditions of pH 8.04 and 1751 µmol] [HC[O.sub.3.sup.-]] k[g.sup.-1] (Treatment 1), (2) pC[O.sub.2]-induced ocean acidification of pH 7.73 and 2011 µmol [HC[O.sub.3.sup.-]] k[g.sup.-1] (Treatment 2), and (3) pC[O.sub.2] and HC[O.sub.3.sup.-]-enriched seawater of pH 7.69 and 2730 µmol HC[O.sub.3.sup.-] k[g.sup.-1] (Treatment 3). The third treatment providing elevated [HC[O.sub.3.sup.-]] was used to test for stimulatory effects of dissolved inorganic carbon on calcification under low pH and low saturation of aragonite ([Ω.sub.arag]), but it does not reflect conditions expected to occur under C[O.sub.2]-driven OA. Calcification of juvenile massive Porites spp. was affected by treatments, with an 81% elevation in Treatment 3 versus Treatment 1, but no difference between Treatments 1 and 2; respiration and the metabolic expenditure concurrent with calcification remained unaffected. These findings indicate that juvenile massive Porites spp. are resistant to short exposures to OA in situ, and separately, that they can increase calcification at low pH and low [Ω.sub.arag] if [HC[O.sub.3.sup.-]] is elevated. Juvenile Porites spp. may therefore be limited by dissolved inorganic carbon under ambient pC[O.sub.2] conditions.

In an attempt to more clearly understand the strength characteristics of female rock climbers and whether those variables affect and predict climbing performance, 2 indoor climbing performance tests (route and bouldering) were compared to a series of muscular strength tests performed by moderate (n = 6), intermediate (n = 6), and expert (n = 6) female rock climbers. Significant differences (p < 0.05) were found between the expert group and the moderate and intermediate groups for climbing specific hand strength, as well as 1-arm lock-off strength when expressed as a strength-to-weight ratio. Multiple correlations showed that these variables (r > 0.426) as well as a questionnaire of past climbing performance (r > 0.86) significantly correlated to the tests of indoor climbing performance. In conclusion, climbing-specific tests of hand strength and of one arm lock-off strength reliably and sensitively measured 2 significant variables in the performance of indoor rock climbing, and a questionnaire of past best performance may be an accurate tool for the prediction of indoor climbing performance. KEY WORDS. rock climbing, strength, endurance, flexibility

Compound‐specific isotope analyses (CSIA) and multivariate "isotope fingerprinting" track biosynthetic sources and reveal trophic interactions in food webs. However, CSIA have not been widely applied in the study of marine symbioses. Here, we exposed a reef coral (Montipora capitata) in symbiosis with Symbiodiniaceae algae to experimental treatments (autotrophy, mixotrophy, heterotrophy) to test for trophic shifts and amino acid (AA) sources using paired bulk (δ13C, δ15N) and AA‐CSIA (δ13CAA, δ15NAA). Treatments did not influence carbon or nitrogen trophic proxies, thereby not supporting nutritional plasticity. Instead, hosts and symbionts consistently overlapped in essential‐ and nonessential‐δ13CAA (11 of 13 amino acids) and trophic‐ and source‐δ15NAA values (9 of 13 amino acids). Host and symbiont trophic‐δ15NAA values positively correlated with a plankton end‐member, indicative of trophic connections and dietary sources for trophic‐AA nitrogen. However, mass balance of AA‐trophic positions (TPGlx–Phe) revealed heterotrophic influences to be highly variable (1–41% heterotrophy). Linear discriminant analysis using M. capitata mean‐normalized essential‐δ13CAA with previously published values (Pocillopora meandrina) showed similar nutrition isotope fingerprints (Symbiodiniaceae vs. plankton) but revealed species‐specific trophic strategies. Montipora capitata and Symbiodiniaceae shared identical AA‐fingerprints, whereas P. meandrina was assigned to either symbiont or plankton nutrition. Thus, M. capitata was 100% reliant on symbionts for essential‐δ13CAA and demonstrated autotrophic fidelity and contrasts with trophic plasticity reported in P. meandrina. While M. capitata AA may originate from host and/or symbiont biosynthesis, AA carbon is Symbiodiniaceae‐derived. Together, AA‐CSIA/isotope fingerprinting advances the study of coral trophic plasticity and are powerful tools in the study of marine symbioses. [ABSTRACT FROM AUTHOR]

Early life stages of the coral Seriatopora caliendrum were used to test the hypothesis that the depression of dark respiration in coral recruits by high pCO2 is caused by perturbed protein metabolism. First, the contribution of protein anabolism to respiratory costs under high pCO2 was evaluated by measuring the aerobic respiration of S. caliendrum recruits with and without the protein synthesis inhibitor emetine following 1 to 4 days at 45 Pa versus 77 Pa pCO2. Second, protein catabolism under high pCO2 was evaluated by measuring the flux of ammonium (NH4+) from juvenile colonies of S. caliendrum incubated in darkness at 47 Pa and 90 Pa pCO2. Two days after settlement, respiration of recruits was affected by an interaction between emetine and pCO2, with emetine reducing respiration 63% at 45 Pa pCO2 and 27% at 77 Pa pCO2. The interaction disappeared 5 days after settlement, when respiration was reduced 27% by emetine under both pCO2 conditions. These findings suggest that protein anabolism accounted for a large proportion of metabolic costs in coral recruits and was affected by high pCO2, with consequences detected in aerobic respiration. Juvenile S. caliendrum showed net uptake of NH4+ at 45 Pa pCO2 but net release of NH4+ at 90 Pa pCO2, indicating that protein catabolism, NH4+ recycling, or both were affected by high pCO2. Together, these results are consistent with the hypothesis that high pCO2 affects protein metabolism in corals. [ABSTRACT FROM AUTHOR]

Juvenile colonies of massive Porites spp. were exposed to manipulated pH and bicarbonate ([HCO3-]) in situ to test the hypothesis that ocean acidification (OA) does not affect respiration and calcification. Incubations lasted 28 h and exposed corals to ambient temperature and light with ecologically relevant water motion. Three treatments were applied: (1) ambient conditions of pH 8.04 and 1751 µmol HCO3- kg-1 (Treatment 1), (2) pCO2-induced ocean acidification of pH 7.73 and 2011 µmol HCO3- kg-1 (Treatment 2), and (3) pCO2 and HCO3--enriched seawater of pH 7.69 and 2730 µmol HCO3- kg-1 (Treatment 3). The third treatment providing elevated [HCO3-] was used to test for stimulatory effects of dissolved inorganic carbon on calcification under low pH and low saturation of aragonite (Ωarag), but it does not reflect conditions expected to occur under CO2-driven OA. Calcification of juvenile massive Porites spp. was affected by treatments, with an 81% elevation in Treatment 3 versus Treatment 1, but no difference between Treatments 1 and 2; respiration and the metabolic expenditure concurrent with calcification remained unaffected. These findings indicate that juvenile massive Porites spp. are resistant to short exposures to OA in situ, and separately, that they can increase calcification at low pH and low Ωaragif [HCO3-] is elevated. Juvenile Porites spp. may therefore be limited by dissolved inorganic carbon under ambient pCO2 conditions. [ABSTRACT FROM AUTHOR]

Premise: The ability of plants to adapt or acclimate to climate change is inherently linked to their interactions with symbiotic microbes, notably fungi. However, it is unclear whether fungal symbionts from different climates have different impacts on the outcome of plant-fungal interactions, especially under environmental stress., Methods: We tested three provenances of fungal inoculum (originating from dry, moderate or wet environments) with one host plant genotype exposed to three soil moisture regimes (low, moderate and high). Inoculated and uninoculated plants were grown in controlled conditions for 151 days, then shoot and root biomass were weighed and fungal diversity and community composition determined via amplicon sequencing., Results: The source of inoculum and water regime elicited significant changes in plant resource allocation to shoots versus roots, but only specific inocula affected total plant biomass. Shoot biomass increased in the high water treatment but was negatively impacted by all inoculum treatments relative to the controls. The opposite was true for roots, where the low water treatment led to greater proportional root biomass, and plants inoculated with wet site fungi allocated significantly more resources to root growth than dry- or moderate-site inoculated plants and the controls. Fungal communities of shoots and roots partitioned by inoculum source, water treatment, and the interaction of the two., Conclusions: The provenance of fungi can significantly affect total plant biomass and resource allocation above- and belowground, with fungi derived from more extreme environments eliciting the strongest plant responses., (© 2025 Botanical Society of America.)

The absorbtion of human-emitted CO 2 by the oceans (elevated P CO 2 ) is projected to alter the physiological performance of coral reef organisms by perturbing seawater chemistry (i.e. ocean acidification). Simultaneously, greenhouse gas emissions are driving ocean warming and changes in irradiance (through turbidity and cloud cover), which have the potential to influence the effects of ocean acidification on coral reefs. Here, we explored whether physiological impacts of elevated P CO 2  on a coral-algal symbiosis ( Pocillopora acuta- Symbiodiniaceae) are mediated by light and/or temperature levels. In a 39 day experiment, elevated P CO 2  (962 versus 431 µatm P CO 2 ) had an interactive effect with midday light availability (400 versus 800 µmol photons m -2  s -1 ) and temperature (25 versus 29°C) on areal gross and net photosynthesis, for which a decline at 29°C was ameliorated under simultaneous high- P CO 2  and high-light conditions. Light-enhanced dark respiration increased under elevated P CO 2  and/or elevated temperature. Symbiont to host cell ratio and chlorophyll a per symbiont increased at elevated temperature, whilst symbiont areal density decreased. The ability of moderately strong light in the presence of elevated P CO 2  to alleviate the temperature-induced decrease in photosynthesis suggests that higher substrate availability facilitates a greater ability for photochemical quenching, partially offsetting the impacts of high temperature on the photosynthetic apparatus. Future environmental changes that result in moderate increases in light levels could therefore assist the P. acuta holobiont to cope with the 'one-two punch' of rising temperatures in the presence of an acidifying ocean., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2020. Published by The Company of Biologists Ltd.)