There are currently recognized 107 species of Philippine amphibians. In addition, several possible new species await formal taxonomic description. Most of them occupy microhabitats in moist or wet tropical rainforests. Based primarily on their known reproductive modes and microhabitats (including altitudinal distributions), the vulnerability of each amphibian species was assessed. The results of our assessment indicate that 26 species (24.30%) are Highly Vulnerable, 48 species (44.86%) are Moderately Vulnerable, 27 species (25.23%) are Vulnerable, and 6 species (5.61%) are Least Vulnerable to climate change. However, this preliminary assessment is tentative and requires verification through field studies using other sets of indicators. Additionally, virtually all new species currently awaiting description are known from forested mountain habitats. These species are deemed disproportionately susceptible to climate change. Thus, the percentages of vulnerable taxa are expected to climb sharply with ongoing taxonomic and ecological studies.
Climate Change, Ocean Acidification, and Ocean Warming
Global climate change is expected to impact ocean ecosystems through increases in temperature, decreases in pH and oxygen, increased stratification, with subsequent declines in primary productivity. These impacts propagate through the food chain leading to amplified effects on secondary producers and higher trophic levels. Similarly, climate change may disproportionately affect different species, with impacts depending on their ecological niche. To investigate how global environmental change will alter fish assemblages and productivity, we used a spatially explicit mechanistic model of the three main fish functional types reflected in fisheries catches (FEISTY) coupled to an Earth system model (GFDL-ESM2M) to make projections out to 2100. We additionally explored the sensitivity of projections to uncertainties in widely used metabolic allometries and their temperature dependence. When integrated globally, the biomass and production of all types of fish decreased under a high emissions scenario (RCP 8.5) compared to mean contemporary conditions. Projections also revealed strong increases in the ratio of pelagic zooplankton production to benthic production, a dominant driver of the abundance of large pelagic fish vs. demersal fish under historical conditions. Increases in this ratio led to a “pelagification” of ecosystems exemplified by shifts from benthic-based food webs toward pelagic-based ones. The resulting pelagic systems, however, were dominated by forage fish, as large pelagic fish suffered from increasing metabolic demands in a warming ocean and from declines in zooplankton productivity that were amplified at higher trophic levels. Patterns of relative change between functional types were robust to uncertainty in metabolic allometries and temperature dependence, though projections of the large pelagic fish had the greatest uncertainty. The same accumulation of trophic impacts that underlies the amplification of productivity trends at higher trophic levels propagates to the projection spread, creating an acutely uncertain future for the ocean’s largest predatory fish.
Climate change and human activities exert a wide range of stressors on urban coastal areas. Synthetical assessment of coastal vulnerability is crucial for effective interventions and long-term planning. However, there have been few studies based on integrative analyses of ecological and physical characteristics and socioeconomic conditions in urban coastal areas. This study developed a holistic framework for assessing coastal vulnerability from three dimensions - biophysical exposure, sensitivity and adaptive capacity - and applied it to the coast of Bohai Economic Rim, an extensive and important development zone in China. A composite vulnerability index (CVI) was developed for every 1 km2 segment of the total 5627 km coastline and the areas that most prone to coastal hazards were identified by mapping the distribution patterns of the CVIs in the present and under future climate change scenarios. The CVIs show a spatial heterogeneity, with higher values concentrated along the southwestern and northeastern coasts and lower values concentrated along the southern coasts. Currently, 20% of the coastlines with approximately 350,000 people are highly vulnerable to coastal hazards. With sea-level rises under the future scenarios of the year 2100, more coastlines will be highly vulnerable, and the amount of highly-threatened population was estimated to increase by 13–24%. Among the coastal cities, Dongying was categorized as having the highest vulnerability, mainly due to poor transportation and medical services and low GDP per capita, which contribute to low adaptive capacity. Our results can benefit decision-makers by highlighting prioritized areas and identifying the most important determinants of priority, facilitating location-specific interventions for climate-change adaptation and sustainable coastal management.
Climate change is impacting fisheries globally, posing both risks and opportunities to those dependent on marine resources. Understanding how fishers perceive climate change, and what factors shape these perceptions, can provide insights into behavioural intentions and support required for climate change focused strategies and management. This study interviewed demersal fishers from a south-west UK fishing port to explore: 1) the future risks fishers identified that may affect their business and wider industry; 2) fishers’ beliefs and risk perceptions relating to climate change; and 3) the factors influencing these perceptions. Fishers identified a number of environmental, socio-economic and fisheries governance risks but climate change was rarely mentioned. While fishers overall had low risk perceptions of climate change, these perceptions were heterogeneous across the sample. Climate change scepticism and a high perceived self-efficacy to adapt to climate change were associated with lower risk perceptions. These findings provide new insights into how fishers perceive climate change and, importantly, greater understanding of the possible drivers of such perceptions. Findings suggest that undertaking climate-awareness raising initiatives in isolation to support adaptation strategies could be limited in success. Instead, wider focus should be applied to removing barriers to adaptation, managing wider risks and incorporating fishers into decision making to effectively support and motivate fishers’ adaptation.
Early evidence suggests that DNA methylation can mediate phenotypic responses of marine calcifying species to ocean acidification (OA). Few studies, however, have explicitly studied DNA methylation in calcifying tissues through time. Here, we examined the phenotypic and molecular responses in the extrapallial fluid and mantle (fluid and tissue at the calcification site) in adult eastern oyster (Crassostrea virginica) exposed to experimental OA over 80 days. Oysters were reared under three experimental pCO2 treatments (“control,” 580 μatm; “moderate OA,” 1,000 μatm; “high OA,” 2,800 μatm) and sampled at 6 time points (24 h−80 days). We found that high OA initially induced an increase in the pH of the extrapallial fluid (pHEPF) relative to the external seawater that peaked at day 9, but then diminished over time. Calcification rates were significantly lower in the high OA treatment compared to the other treatments. To explore how oysters regulate their extrapallial fluid, gene expression and DNA methylation were examined in the mantle-edge tissue of oysters from days 9 and 80 in the control and high OA treatments. Mantle tissue mounted a significant global molecular response (both in the transcriptome and methylome) to OA that shifted through time. Although we did not find individual genes that were significantly differentially expressed under OA, the pHEPF was significantly correlated with the eigengene expression of several co-expressed gene clusters. A small number of OA-induced differentially methylated loci were discovered, which corresponded with a weak association between OA-induced changes in genome-wide gene body DNA methylation and gene expression. Gene body methylation, however, was not significantly correlated with the eigengene expression of pHEPF-correlated gene clusters. These results suggest that OA induces a subtle response in a large number of genes in C. virginica, but also indicate that plasticity at the molecular level may be limited. Our study highlights the need to reassess our understanding of tissue-specific molecular responses in marine calcifiers, as well as the role of DNA methylation and gene expression in mediating physiological and biomineralization responses to OA.
Artificial upwelling (AU) is a novel geoengineering technology that brings seawater from the deep ocean to the surface. Within the context of global warming, AU techniques are proposed to reduce sea surface temperature at times of thermal stress around coral reefs. A computationally fast but coarse 3D Earth System model (3.6° longitude × 1.8° latitude) was used to investigate the environmental impacts of hypothetically implemented AU strategies in the Great Barrier Reef, South China Sea, and Hawaiian regions. While omitting the discussion on sub-grid hydrology, we simulated in our model a water translocation from either 130 or 550 m depth to sea surface at rates of 1 or 50 m3 s–1 as analogs to AU implementation. Under the Representative Concentration Pathway 8.5 emissions scenario from year 2020 on, the model predicted a prevention of coral bleaching until the year 2099 when AU was implemented, except under the least intense AU scenario (water from 130 m depth at 1 m3 s–1). Yet, intense AU implementation (water from 550 m depth at 50 m3 s–1) will likely have adverse effects on coral reefs by overcooling the surface water, altering salinity, decreasing calcium carbonate saturation, and considerably increasing nutrient levels. Our result suggests that if we utilize AU for mitigating coral bleaching during heat stress, AU implementation needs to be carefully designed with respect to AU’s location, depth, intensity and duration so that undesirable environmental effects are minimized. Following a proper installation and management procedure, however, AU has the potential to decelerate destructive bleaching events and buy corals more time to adjust to climate change.
Chemical changes in the diffusive boundary layer (DBL) generated by photosynthesising macroalgae are expected to play an important role in modulating the effects of ocean acidification (OA), but little is known about the effects on early life stages of marine invertebrates in modified DBLs. Larvae that settle to macroalgal surfaces and remain within the DBL will experience pH conditions markedly different from the bulk seawater. We investigated the interactive effects of seawater pH and DBL thickness on settlement and early post-settlement growth of the sea urchin Pseudechinus huttoni, testing whether coralline-algal DBLs act as an environmental buffer to OA. DBL thickness and pH levels (estimated from well-established relationships with oxygen concentration) above the crustose coralline algal surfaces varied with light availability (with photosynthesis increasing pH to as high as pH 9.0 and respiration reducing pH to as low as pH 7.4 under light and dark conditions, respectively), independent of bulk seawater pH (7.5, 7.7, and 8.1). Settlement success of P. huttoni increased over time for all treatments, irrespective of estimated pH in the DBL. Juvenile test growth was similar in all DBL manipulations, showing resilience to variable and low seawater pH. Spine development, however, displayed greater variance with spine growth being negatively affected by reduced seawater pH in the DBL only in the dark treatments. Scanning electron microscopy revealed no observable differences in structural integrity or morphology of the sea urchin spines among pH treatments. Our results suggest that early juvenile stages of P. huttoni are well adapted to variable pH regimes in the DBL of macroalgae across a range of bulk seawater pH treatments.
Biological fitness relies on processes acting at various levels of organization, all of which can be modified by environmental change. Application of synthesis frameworks, such as the Adverse Outcome Pathway (AOP), can enhance our understanding of the responses to stressors identified in studies at each level, as well as the links among them. However, the use of such frameworks is often limited by a lack of data. In order to identify contexts with sufficient understanding to apply the AOP framework, we conducted a meta-analysis of studies considering ocean acidification effects on calcifying mollusks. Our meta-analysis identified that most studies considered the adult life history stage, bivalve taxonomic group, individual-level changes, and growth- and metabolism-related responses. Given the characteristics of the published literature, we constructed an AOP for the effects of ocean acidification on calcification in an adult bivalve, specifically the Pacific oyster (Magallana gigas). By structuring results within the AOP framework, we identify that, at present, the supported pathways by which ocean acidification affects oyster calcification are via the downregulation of cavortin and arginine kinase transcription. Such changes at the molecular level can prompt changes in cellular and organ responses, including altered enzyme activities, lipid peroxidation, and regulation of acid–base status, which have impacts on organism level metabolic rate and, therefore, calcification. Altered calcification may then impact organism mortality and population sizes. We propose that when developed and incorporated in future studies, the AOP framework could be used to investigate sources of complexity including varying susceptibility within and among species, feedback mechanisms, exposure duration and magnitude, and species interactions. Such applications of the AOP framework will allow more effective reflections of the consequences of environmental change, such as ocean acidification, on all levels of biological organization.
In Europe, implementation of sustainable fisheries management has been reinforced in the latest common fisheries policy, and presently marine fish stocks are mostly managed through assessment of their exploitation and ecological status compared to reference points such as Maximum Sustainable Yield (MSY). However, MSY and its associated fishing mortality rate FMSY are sensitive to both stock characteristics and environment conditions. In parallel, climate change impacts are increasingly affecting fish stocks directly and indirectly but might also change the exploitation reference points and the associated level of catch. Here we explored the variability of MSY reference points under climate change by using a multi-species model applied to the Eastern English Channel, a highly exploited semi-continental sea. The spatial individual-based OSMOSE explicitly represents the entire fish life cycle of 14 species interacting through size-based opportunistic predation. The model was first parameterized and run to fit the historical situation (2000–2009) and then used to assess the ecosystem state for the 2050–2059 period, using two contrasting climate change scenarios (RCP 4.5 and RCP 8.5). For each condition, a monospecific MSY estimation routine was performed by varying species fishing mortality independently and allowed estimation of reference points for each species. The FMSY estimated with OSMOSE were mostly in accordance with available values derived from stock assessment and used for fishing advice. Evolution of reference points with climate change was compared across species and highlighted that overexploited cold-water species are likely to have both MSY and FMSY declining with climate warming. Considering all species together, MSY under RCP scenarios was expected to be higher than historical MSY for half of them, with no clear link with species temperature preferences, exploitation status or trophic level, but in relation with expected change of species biomass under climate change. By contrast, for 80% of cases FMSY projections showed consistent decreasing pattern as climate conditions changed from historical to RCP scenarios in the Eastern English Channel. This result constitutes a risk for fisheries management, and anticipation of climate change impacts on fish community would require targeting a smaller fishing mortality than FMSY to ensure sustainable exploitation of marine stocks.
Most literature exploring the biological effects of ocean acidification (OA) has focused on macroscopic organisms and far less is known about how marine microbial communities will respond. Studies of OA and microbial community composition and diversity have examined communities from a limited number of ocean regions where the ambient pH is near or above the global average. At San Juan Island (Salish Sea), a region that experiences naturally low pH (average = 7.8), the picoplankton (cell diameter is 0.2–2μm) community was predicted to show no response to experimental acidification in a three-week mesocosm experiment. Filtered seawater mesocosms were maintained via semicontinuous culturing. Three control mesocosms were maintained at pH 8.05 and three acidified mesocosms were maintained at pH 7.60. Total bacteria was quantified daily with a flow cytometer. Microbial communities were sampled every two days via filtration followed by DNA extraction, 16S rRNA amplification, and MiSeq sequencing. There was no significant difference in total bacteria between pH treatments throughout the experiment. Acidification significantly reduced Shannon’s diversity over time. During the final week of the experiment, acidification resulted in a significant decrease in Shannon’s diversity, Faith’s phylogenetic distance, and Pielous’s Evenness. ANCOM results revealed four bacterial ASVs (amplicon sequence variants), in families Flavobaceriaceae and Hyphomonadaceae that significantly decreased in relative frequency under acidification and two bacterial ASVs, in families Flavobacteriaceae and Alteromonadaceae, that significantly increased under acidification. This is the first OA study on the microbial community of the Salish Sea, a nutrient rich, low pH region, and the first of its kind to report a decrease in both picoplankton richness and evenness with acidification. These findings demonstrate that marine microbial communities that naturally experience acidic conditions are still sensitive to acidification.