Climate Change Ecology最新文献

Sargassum mats in Mexican bays reduce the biodiversity of coral and seagrass nursery habitats. Three bays in Quintana Roo, Mexico were chosen to determine the environmental stress caused by Sargassum natans and S. fluitans on coral, seagrass and fish populations. For both control sites, Yal Ku Lagoon and Half Moon Bay with little to zero Sargassum cover, benthic communities and the physico chemical characteristics of the waters were not impacted. In Soliman Bay, Sargassum mats cover large areas in the shallows and shore and smother the seagrass and corals. Under the Sargassum mats light and dissolved oxygen levels were significantly lower. Anoxic conditions were found, with levels as low as 0.5 mg/L for oxygen and a 73% decrease in light. Water temperature was 5.2 ± 0.1 °C (mean ± SE) warmer under the Sargassum mats. By determination of weight (grams per day) and growth (mm per day), the stress caused by Sargassum mats in Soliman Bay caused a seven-fold decrease in productivity of T. testudinum compared to other sites. Taxonomic diversity was also reduced with lower biomass and an altered species distribution. To improve these ecosystems, pre-emptive conservation management and protection must be priority for future ecosystem health and biodiversity.

Phenological matching between the timing of flowering and pollinator activity is critically important for the persistence of pollination systems globally. Phenological mismatch between plants and their insect pollinators can occur if flowering and adult insect activity do not occur simultaneously. There is evidence that the phenological trajectories vary among bee species, but little has been done to compare these trajectories with the phenology of the corresponding floral community. In this work, we use daily pan trapping across nine different annual Clarkia (Onagraceae) plant communities that vary in Clarkia species composition to estimate the phenological trajectory (within-season abundance curve) of the two most abundant bee pollinators - Lasioglossum incompletum, a generalist, and Hesperapis regularis, a Clarkia specialist - over the course of a Clarkia flowering season in California USA. Clarkia flower at the end of the winter annual growing season when all other winter annual plants have senesced, and therefore are phenologically separate from other flowering plants. We find that Hesperapis pollinator abundances follow the same phenological trajectory as Clarkia floral abundances in all community types. In contrast, Lasioglossum abundances do not track Clarkia floral abundance through time. Our results demonstrate that Clarkia exhibit closer phenological matching with Hesperapis than with Lasioglossum. These findings imply that pollinator communities may not respond monolithically to changes in the environment. Future research should study the phenological trajectories of plants and pollinators in different systems to determine if this pattern is common and repeatable.

Biofilms harbour a wealth of microbial diversity and fulfil key functions in coastal marine ecosystems. Elevated carbon dioxide (CO₂) conditions affect the structure and function of biofilm communities, yet the ecological patterns that underpin these effects remain unknown. We used high-throughput sequencing of the 16S and 18S rRNA genes to investigate the effect of elevated CO₂ on the early successional stages of prokaryotic and eukaryotic biofilms at a CO₂ seep system off Shikine Island, Japan. Elevated CO₂ profoundly affected biofilm community composition throughout the early stages of succession, leading to greater compositional homogeneity between replicates and the proliferation of the potentially harmful algae Prymnesium sp. and Biddulphia biddulphiana. Species turnover was the main driver of differences between communities in reference and high CO₂ conditions, rather than differences in richness or evenness. Our study indicates that species turnover is the primary ecological pattern that underpins the effect of elevated CO₂ on both prokaryotic and eukaryotic components of biofilm communities, indicating that elevated CO₂ conditions represent a distinct niche selecting for a distinct cohort of organisms without the loss of species richness.

Specific proximate mechanisms as climate spatial fluctuations modify the pattern of synchronic reproduction (masting) or seed production at population level in the Fagus genus worldwide. However, phenological processes as mass flowering, beechnut development and seed rain have attracted attention to understand the masting behavior in relict-endangered tree species. The normalized difference vegetation index (NDVI), temperature and precipitation could act as proxy signals resembling the onset of mast-seeding events. We studied a masting event in 2017 in ten relict-endangered Mexican beech forests (Fagus grandifolia subsp. mexicana) in eastern Mexican montane cloud forests. Our aims were 1) test if NDVI shows a particular pattern before and after masting event in 2017 at 10 sites; 2) explore how monthly temperature and precipitation change two years before and during the masting across the Mexican beech forests; and 3) assess how the beechnut amount and quality was affected by spatial and temporal specific climatic variables in the recorded masting event among the beech forests. We found that the masting was related to the canopy greenness variation (2015–2018) in the beech forests. Nut production variability among beech forests was related to temperature and precipitation fluctuations. We found that maximum and mean temperature and high precipitation during May to August were decisive to trigger the synchronic Mexican beech masting spatial behavior.

Future water temperature changes may have a profound impact on fish-parasite interactions. However, while the effect of temperature on fish, and particularly salmonids, is well-understood, its combined effects with parasitic exposure are not. Here, we use a multi-stage experimental approach to explore the impact of increased water temperatures consistent with persistent climate change-induced warming and extreme thermal fluctuations from hydropower (thermopeaking) on brown trout alevins and fry before and during exposure to Saprolegnia parasitica. Parasite exposure had the strongest and most significant effect on survival of both host life stages. The combination of parasite exposure, thermal pre-conditioning and the ongoing thermal regime had a weak but significant influence on alevin mortality. Both parasite-exposed alevin and fry experienced increased mortality when a constant increase in temperature was combined with intermittent thermal increases. The outcomes of this experimental approach provide the basis for future studies scaling up the potential impacts of temperatures and parasite exposure that key fish species may face in the wild. They also highlight the effects of anthropogenic changes on brown trout populations, as pressures on aquatic organisms are likely to intensify in future climate scenarios with increased hydropower development and thermopeaking, particularly in the presence of pathogens.

Global climate change and anthropogenic nutrient inputs are responsible for increased frequency of cyanobacterial blooms that potentially contain 55 classes of bioactive metabolites. This study investigated the effects of CO₂ availability and concomittant pH levels on two cyanobacteria that produce microcystins: a marine cf. Synechocystis sp. and a freshwater Microcystis aeruginosa. Cyanobacterial strains were semi-continuously cultured in mesotrophic growth media at pH 7.5, 7.8, 8.2, and 8.5 via a combination of CO₂ addition and control of alkalinity. The cell concentration between treatments was not significantly different and nutrient availability was not limited. Concentration of most known cyanobacterial bioactive metabolites in both cyanobacterial strains increased as CO₂ increased. At pH 7.8, bioactive metabolite intracellular concentration in M. aeruginosa and Synechocystis was 1.5 and 1.2 times greater than the other three treatments, respectively. Intracellular concentration of microginin in M. aeruginosa at pH 7.5 was reduced by 90% compared to the other three treatments. Intracellular concentration of microcyclamide-bistratamide B was lower in M. aeruginosa and higher in Synechocystis at elevated CO₂ concentration. M. aeruginosa products were more diverse metabolites than Synechocystis. The diversity of accumulated metabolites in M. aeruginosa increased as CO₂ increased, whereas the metabolite diversity in Synechocystis decreased as pH decreased. Overall, intracellular concentration of bioactive metabolites was higher at greater CO₂ concentrations; marine and freshwater cyanobacteria had different allocation products when exposed to differing CO₂ environments.

Increased aridity, associated with climate change, is predicted worldwide in the coming decades. Species persistence in the face of climate change is thought to be influenced by plasticity, potential for adaptation, and dependence on non-climatic factors, but their relative importance has rarely been quantified. We investigated 13 populations of Eschscholzia californica (California poppy) distributed across a fourfold gradient in annual precipitation. In a greenhouse, plants received precipitation treatments approximating the wettest and driest sites, crossed with the presence and absence of soil inoculum from their collection location. We documented clinal variation across populations; plants from southern populations (arid sites) emerged later, flowered earlier, had shorter growing seasons, higher mean fitness, higher reproductive effort, and were more drought tolerant than plants from northern populations (mesic sites). A second experiment demonstrated clinal variation in biomass allocation, with higher root allocation in northern populations. We found no evidence of adaptive phenological plasticity to drought; instead, the drought treatment decreased fitness and growing season length (maladaptive phenological plasticity) more for plants from mesic than arid sites. Individuals grown with home soil inoculation produced 10% more biomass than when grown in common garden soil; however, the influence of soil was small relative to the 13-fold variation across populations in fitness responses to drought. Our results suggest that restoration efforts involving California poppy may benefit from assisted gene flow; sourcing seeds from arid parts of the species range may improve individual fitness and population persistence of this iconic species in the face of future climate change.

Climate change is affecting species composition and diversity across the globe. Phenological changes provide a sensitive indicator of biological responses to changes in climate. Recent studies using herbarium records in Europe and North America have shown changes in flowering time and other phenological events in response to changing climate conditions, such as warming temperatures and chilling winters, but few studies have been carried out in the southern hemisphere. We examined changes in flowering time from 1901–2009 in South Africa in the widespread, diverse genus Pelargonium. We combined records from more than 6,200 herbarium specimens of 129 species with historical weather data on temperature to examine the impact of climate change on flowering phenology. Data from over 464 weather stations in South Africa was used to estimate historical climate conditions for each of the 4,600 geographic sites included in our sample. During this time period there was a 2.9 ± 0.53 °C increase in mean annual temperature across South Africa. Flowering date advanced by nearly two weeks (11.6 days), with nearly all of the advance associated with the increase in temperature during this time. Thus, Pelargonium species are showing similar phenological responses when compared to species in the northern hemisphere. This study adds more evidence to the limited number of studies of climate change responses within Mediterranean climate regions that assess large-scale climate and phenological patterns. It also illustrates that herbarium records provide an effective method for detecting effects of climate change on flowering phenology across large geographic scales.

Climatic changes have had significant impacts on marine ecosystems, including apex predators such as cetaceans. A more complete understanding of the potential impacts of climate change on cetaceans is necessary to ensure their conservation. Here we present a review of the literature on the impacts of climate change on cetacean distribution, habitat and migrations and highlight research gaps. Our results indicate that due to rising sea surface temperatures (SSTs) and/or reducing sea ice extent, a variety of impacts on the distribution, habitat and migration of cetaceans have been observed to date and several more are predicted to occur over the next century. Many species have demonstrated a poleward shift, following their preferred SSTs to higher latitudes, and some have altered the timing of their migrations, while others appear not to be affected. These changes may benefit certain species, while others will be placed under extreme pressure and may face increased risk of extinction. Broader implications may include increased inter-specific competition, genetic alterations, ecosystem-level changes and conservation challenges. Existing research on the topic is both extremely limited and unevenly distributed (geographically and phylogenetically). Further research is necessary to determine which species and populations are most vulnerable and require the earliest conservation action.