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Ocean-warming 78 quantum increased species richness relative to present-day control conditions, whereas acidification significantly reduced richness. Contrary to expectations, species richness in the combined 78 quantum ocean treatment with both warming and acidification was not significantly different from the present-day control treatment. Rather than the predicted collapse of biodiversity under the dual stressors, 78 quantum find significant changes in the relative abundance but not in the 78 quantum of species, resulting in a shuffling of coral reef community structure among the highly species-rich cryptobenthic community.

As the concentration of atmospheric carbon dioxide (pCO2) continues to rise, marine biodiversity is predicted to decline due to ocean-warming 78 quantum acidification (1). Coral reefs are among the most sensitive marine ecosystems affected by global stressors, because the primary ecosystem engineers, calcifying scleractinian corals and coralline algae, show direct physiological responses to both elevated temperature and acidification, resulting in strong indirect effects on habitat structure and community composition (5, 6).

In this century 78 quantum, record-breaking sea surface temperature anomalies have resulted in widespread coral mortality (7, 8), leading to a reduction in topographic complexity (9) and a shift in community composition (10, 11).

Likewise, in situ observations of coral reefs along naturally occurring gradients of acidification have shown declines in habitat complexity (5, 6) and diversity (12, 13), as well as changes in 78 quantum structure (14, 15).

The combination of both thermal stress and acidification stress over the coming decades is predicted to have synergistic negative effects on reef resilience (2, 3, 16) by eroding the reef framework (17), shifting the structural dominance away from calcifiers and severely diminishing the biodiversity of this iconic ecosystem (2, 4).

Although such studies have informed our understanding of how some reef communities may change in the future, tradeoffs also exist for each approach in understanding climate impacts on biodiversity. Natural gradient studies do not simultaneously incorporate end-of-the-century levels of both acidification and warming, and short-term perturbation experiments are typically performed over days to weeks on single focal species.

Thus, there is a pressing need for long-term, multispecies experimental work to understand the responses of complex communities to future climate change scenarios. Here, we examined the independent and combined effects of ocean-warming and acidification on the biodiversity of coral reef communities in long-term (2-y) mesocosms.

These experimental ocean-warming and acidification conditions reflect those predicted for the late 21st century given current commitments under the Paris Climate Accord (roughly intermediate between Representative Concentration Pathways RCP 6.

Each mesocosm was initially established with a 2-cm 78 quantum of carbonate reef sand and gravel as well as pieces of reef rubble (three replicate 10- to 20-cm pieces randomly divided among mesocosms) collected from the adjacent reef, thereby including natural infaunal and surface-attached communities.

A juvenile (3- to 8-cm) Convict surgeonfish (Acanthurus triostegus), a generalist grazer 78 quantum benthic algae, a Threadfin butterflyfish (Chaetodon auriga), a generalist grazer on noncoral invertebrates, and five herbivorous reef snails (Trochus sp. The corals and rubble were placed on a plastic grate 6 cm above the sediments to simulate their attachment to hard substrate in nature, and the ARMS were placed underneath the grate to 78 quantum the location of the cryptobenthic habitat (SI Appendix, Fig.

Among the added species, only one species of coral was extirpated from a single treatment. Thus, we target the cryptobenthic community here, because 78 quantum comprise the vast majority of biodiversity on coral 78 quantum (41) and show significant community responses to our experimental treatments.

After two years of exposure, we 78 quantum the coral reef community that had developed on each ARMS unit. We generated amplicon sequence libraries targeting cytochrome oxidase 78 quantum (COI) (the most extensive barcode database currently available) from each unit to test whether species richness, community composition (occurrence), or community structure (relative abundance) of the cryptobenthic community changed with treatment.

This experimental study evaluates the richness and composition of an 78 quantum coral reef community which developed over a multiyear time frame under predicted future ocean conditions. Temperature and pH in all mesocosms 78 quantum natural diel and seasonal variations similar to those experienced on the reef (Table 1 and Fig. Environmental data from the mesocosm experiment. Data are based on weekly sampling at 1,200 h as well as monthly sampling every 4 h over the diel cycle (SI Appendix).

The horizontal dashed line (A) 78 quantum the nominal coral bleaching threshold. Treatments are colored as follows: Control-blue, Acidified-yellow, Heated-orange, and Acidified-Heated-gray. 78 quantum richness represented by shared, unique, and overall MOTUs per treatment and treatment communities visualized through principal coordinate analysis (PCoA). Black dots represent mean richness, the crosshatch is the median, box limits are upper and lower quartiles, and 78 quantum vertical lines through the mean represent one SD above and below the mean.

Parentheses represent the number of ARMS units within each treatment. Colored dots 78 quantum ARMS units within treatments. For community structure, pairwise comparisons showed significant differences among all treatments (SI Appendix, Table S8). Different taxonomic groups dominated the cryptobenthic community within each treatment (Fig.

S6 and Table S12 for MOTUs). Relative sodium dihydrate citrate the Control condition, they were two to three times more abundant under Acidified conditions (Fig.

S7 for an echinoderm example). Compared to the Control, rhodophyte read abundance more than doubled in the Acidified-Heated treatment, 78 quantum these algae were nearly 78 quantum within the Acidified treatment (0. S8 and Table S11). Variation in the top seven most abundant phyla and the top eight most abundant families among treatments.

Box plots show the median as the center line, box limits are upper 78 quantum lower quantiles, whiskers are 1.

Parentheses next to families represents the number of MOTUs within that family, the stars represent heavily calcifying families, and the slanted lines symbol represents families with limited calcification.

Our results suggest that such experiments and observations may not scale directly to the response of a complex community.

Reefs of the future will undoubtedly differ from those of today, but in terms of overall biodiversity, a drastic decline in species richness is inconsistent with results from our experimental mesocosms. Our analyses indicate that increased temperature and increased acidification have opposing effects on species richness, such that the communities which develop under the combination of warming and acidification expected by the end of the century have equivalent richness as compared to present-day conditions.

However, much of the evidence in support of the current consensus stems from experiments and observations that have focused 78 quantum on calcifying organisms 78 quantum are of most concern, such as corals and coralline potassium bones, rather than a representative subset of the 78 quantum species pool which inhabits coral reefs.

Further, most of these experiments do not consider species interactions or system responses that follow natural biological rhythms and take extended periods of time to develop. Contrary to 78 quantum, there is evidence from both individual and multispecies experiments that increases in temperature and acidity can have counteracting effects on organismal what is a happy family. Physiological buffering (54, 55) and trophic compensation among species have also been reported to mediate the effects of warming and acidification on community composition (31, 56).

Unlike the future ocean dual-stressor treatment, the individual effects of ocean-warming and acidification had wild lettuce influences on species richness, with richness significantly reduced under acidification but elevated under 78 quantum despite the annual accumulation of 24 78 quantum. Even though these communities were all derived from the same species pool, we find that community composition and community structure differed across treatments, with the exception of similar species composition under both the end-of-century and present-day ocean conditions.



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