Preservation of community structure in modern reef coral life and death assemblages of the Florida Keys: Implications for the Quaternary fossil record of coral reefs

The reef fossil record is the exclusive database from which analyses of the response of coral communities to environmental change over geological time scales may be gauged. However, few studies have attempted to ascertain whether the reef fossil record is a reasonably accurate representation of a once living coral community. To address this issue, we first assume that an assemblage of dead corals accumulating in close proximity to a living coral reef(including the dead portions of living colonies) provides a reasonable proxy for the material that potentially becomes fossilized We then perform a systematic comparison of the taxonomic composition and diversity present in coral life assemblages and death assemblages accumulating in reef tract and patch reef environments adjacent to Key Large, Florida. The death assemblage is distinct from the life assemblage, but matches exactly the zonation of live corals between reef tract and patch reef environments. The difference in taxonomic composition between life and death assemblages is the result of a striking growth form bias in the depth assemblage: massive coral colony forms predominate in the life assemblages in both environments, whereas branching colony forms predominate in the death assemblages. Calculations of species richness and the Shannon-Wiener index of diversity produced conflicting results. At one reef tract site, the death assemblage was more diverse than the life assemblage. Unlike the Indo-Pacific, the subset of the life assemblage retained as recognizable corals in the death assemblage is not less diverse. We attribute this difference to a more diverse "starting pool" of live corals in the Indo-Pacific. Fidelity indices were similar to those calculated for life and death assemblages occurring in the Indo-Pacific, but very different than those compiled for molluscan shelly assemblages. If the death assemblages we examined represent a reasonable proxy for a potential fossil assemblage, analyses of relative changes in coral reef community structure during Quaternary time should provide reliable base line data for assessing the response of modern Caribbean reefs to global change

Trends and transitions observed in an iconic recreational fishery across 140 years

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordRecreational fishing has taken place for centuries and is a globally popular activity, yet a lack of monitoring data means historical trends in recreational fisheries are often little understood compared to their commercial counterparts. We examined archival sources and conducted fisher interviews to examine changes in the Queensland recreational snapper (Chrysophrys auratus) fishery throughout its documented history. Over a 140-year period, we extracted data on technological innovations, catch rate trends, and social and regulatory change. Technological innovations were evident throughout the history of the recreational fishery. During the 1960s, 1990s and 2000s, several periods of rapid technological transition occurred, where a technology was adopted by >50% of recreational fishers within 10 years of its introduction. Since the 1960s, the timing and rate of adoption of fish-finding technology by recreational fishers has kept pace with the commercial sector. These technological advances have profoundly increased recreational targeting ability, but despite these advances, recalled recreational catch rate trends demonstrated significant declines over the course of the 20th century. While minimum size limits have been imposed on the snapper fishery for over a century, in contrast, the introduction of recreational in-possession limits only commenced in the 1990s. At this time, the beginnings of a societal transition was also observed, where longstanding ‘take all’ attitudes towards fishing began to be replaced by a more conservation minded ethic. This shift was driven in part by the changing regulatory landscape, as well as wider attitudinal change influenced by the media and shifting societal norms, although whether this led to a reduction in total recreational catch remains unclear due to a lack of fishery-wide monitoring data and the open access nature of the recreational fishery. This study demonstrates that in the absence of systematic data collection, archival sources and fisher interviews can contribute an interdisciplinary knowledge base for understanding and interpreting historical fishery trends.RT, SB and JP were supported by the ARC Centre of Excellence for Coral Reef Studies. Fieldwork costs were supported by the University of Queensland’s New Staff Start-Up Fund, awarded to RT, and the Fisheries Research Development Corporation (FRDC) on behalf of the Australian Government, report 2013-018 "Using commercial and recreational fisher knowledge to reconstruct historical catch rates for Queensland pink snapper (Pagrus auratus) and Spanish mackerel (Scomberomorus commerson): long-term data for incorporation into future stock assessments”

Differential response to abiotic stress controls species distributions at biogeographic transition zones

Understanding range limits is critical to predicting species responses to climate change. Subtropical environments, where many species overlap at their range margins, are cooler, more light-limited and variable than tropical environments. It is thus likely that species respond variably to these multi-stressor regimes and that factors other than mean climatic conditions drive biodiversity patterns. Here, we tested these hypotheses for scleractinian corals at their high-latitude range limits in eastern Australia and investigated the role of mean climatic conditions and of parameters linked to abiotic stress in explaining the distribution and abundance of different groups of species. We found that environmental drivers varied among taxa and were predominantly linked to abiotic stress. The distribution and abundance of tropical species and gradients in species richness (alpha diversity) and turnover (beta diversity) were best explained by light limitation, whereas minimum temperatures and temperature fluctuations best explained gradients in subtropical species, species nestedness and functional diversity. Variation in community structure (considering species composition and abundance) was most closely linked to the combined thermal and light regime. Our study demonstrates the role of abiotic stress in controlling the distribution of species towards their high-latitude range limits and suggests that, at biogeographic transition zones, robust predictions of the impacts of climate change require approaches that account for various aspects of physiological stress and for species abundances and characteristics. These findings support the hypothesis that abiotic stress controls high-latitude range limits and caution that projections solely based on mean temperature could underestimate species’ vulnerabilities to climate change

Local and regional controls of phylogenetic structure at the high-latitude range limits of corals

Understanding how range-edge populations will respond to climate change is an urgent research priority. Here, we used a phylogenetic community ecology approach to examine how ecological and evolutionary processes shape biodiversity patterns of scleractinian corals at their high-latitude range limits in eastern Australia. We estimated phylogenetic signal in seven ecologically important functional traits and conducted tests of phylogenetic structure at local and regional scales using the net relatedness (NRI) and nearest taxon indices (NTI) for the presence/absence and abundance data. Regional tests showed light phylogenetic clustering, indicating that coral species found in this subtropical-to-temperate transition zone are more closely related to each other than are species on the nearby, more northerly Great Barrier Reef. Local tests revealed variable patterns of phylogenetic clustering and overdispersion and higher than expected phylogenetic turnover among sites. In combination, these results are broadly consistent with the hierarchical filtering model, whereby species pass through a regional climatic filter based on their tolerances for marginal conditions and subsequently segregate into local assemblages according to the relative strength of habitat filtering and species interactions. Conservatism of tested traits suggests that corals will likely track their niches with climate change. Nevertheless, high turnover of lineages among sites indicates that range shifts will probably vary among species and highlights the vulnerability and conservation significance of high-latitude reefs

Quantifying the historical development of recreational fisheries in Southeast Queensland, Australia

This is the author accepted manuscript. The final version is available from Inter Research via the DOI in this recordRecreational fisheries are of global socio-ecological importance and contribute significantly to local economies and fisheries harvests. In some regions of Australia, organized recreational fishing activities have existed for over 150 yr. However, historical understanding of the spatio-temporal development and resource usage of recreational fisheries has been hampered by the lack of continuous time-series catch and effort data. This study used historical newspaper articles of reported landings by fishing clubs to reconstruct catch rate trends and evaluate changes in catch composition of marine recreational fishing activities in Moreton Bay, Queensland, Australia, from 1920−1984. Using generalized additive mixed models, 2 catch rate metrics (no. of fish fisher−1 trip−1 and kg fish fisher−1 trip−1) were constructed as functions of time and distance travelled. Significant nonlinear relationships were found for no. of fish fisher−1 trip−1. Fluctuations in no. of fish fisher−1 trip−1 were strongly influenced by time, while increases in distance travelled predicted a larger no. of fish fisher−1 trip−1. Measures of kg fish fisher−1 trip−1 were tightly linked to increases in distance travelled but did not vary with time. Spatial analysis revealed shifts in areas fished, from inshore reefs during the 1920s and 1930s (pre-WWII) towards isolated offshore island systems in later decades (>1950s; post-WWII). Reported catches pre-WWII were strongly associated with reef species, while reported catches post-WWII were predominantly characterized by demersal coastal fish. Spatially resolved time-series fisheries data can be reconstructed from archival sources, providing valuable information about the development of recreational fishing activities and explaining the historical social−ecological dynamics that led to current ecosystem states.QUEX InstituteAustralian Research Council (ARC)University of QueenslandEuropean Union Horizon 202

Linking population size structure, heat stress and bleaching responses in a subtropical endemic coral

Anthropocene coral reefs are faced with increasingly severe marine heatwaves and mass coral bleaching mortality events. The ensuing demographic changes to coral assemblages can have long-term impacts on reef community organisation. Thus, understanding the dynamics of subtropical scleractinian coral populations is essential to predict their recovery or extinction post-disturbance. Here we present a 10-yr demographic assessment of a subtropical endemic coral, Pocillopora aliciae (Schmidt-Roach et al. in Zootaxa 3626:576–582, 2013) from the Solitary Islands Marine Park, eastern Australia, paired with long-term temperature records. These coral populations are regularly affected by storms, undergo seasonal thermal variability, and are increasingly impacted by severe marine heatwaves. We examined the demographic processes governing the persistence of these populations using inference from size-frequency distributions based on log-transformed planar area measurements of 7196 coral colonies. Specifically, the size-frequency distribution mean, coefficient of variation, skewness, kurtosis, and coral density were applied to describe population dynamics. Generalised Linear Mixed Effects Models were used to determine temporal trends and test demographic responses to heat stress. Temporal variation in size-frequency distributions revealed various population processes, from recruitment pulses and cohort growth, to bleaching impacts and temperature dependencies. Sporadic recruitment pulses likely support population persistence, illustrated in 2010 by strong positively skewed size-frequency distributions and the highest density of juvenile corals measured during the study. Increasing mean colony size over the following 6 yr indicates further cohort growth of these recruits. Severe heat stress in 2016 resulted in mass bleaching mortality and a 51% decline in coral density. Moderate heat stress in the following years was associated with suppressed P. aliciae recruitment and a lack of early recovery, marked by an exponential decrease of juvenile density (i.e. recruitment) with increasing heat stress. Here, population reliance on sporadic recruitment and susceptibility to heat stress underpin the vulnerability of subtropical coral assemblages to climate change

Ecological and methodological drivers of species' distribution and phenology responses to climate change

Climate change is shifting species’ distribution and phenology. Ecological traits, such as mobility or reproductive mode, explain variation in observed rates of shift for some taxa. However, estimates of relationships between traits and climate responses could be influenced by how responses are measured. We compiled a global data set of 651 published marine species’ responses to climate change, from 47 papers on distribution shifts and 32 papers on phenology change. We assessed the relative importance of two classes of predictors of the rate of change, ecological traits of the responding taxa and methodological approaches for quantifying biological responses. Methodological differences explained 22% of the variation in range shifts, more than the 7.8% of the variation explained by ecological traits. For phenology change, methodological approaches accounted for 4% of the variation in measurements, whereas 8% of the variation was explained by ecological traits. Our ability to predict responses from traits was hindered by poor representation of species from the tropics, where temperature isotherms are moving most rapidly. Thus, the mean rate of distribution change may be underestimated by this and other global syntheses. Our analyses indicate that methodological approaches should be explicitly considered when designing, analysing and comparing results among studies. To improve climate impact studies, we recommend that (1) reanalyses of existing time series state how the existing data sets may limit the inferences about possible climate responses; (2) qualitative comparisons of species’ responses across different studies be limited to studies with similar methodological approaches; (3) meta-analyses of climate responses include methodological attributes as covariates; and (4) that new time series be designed to include the detection of early warnings of change or ecologically relevant change. Greater consideration of methodological attributes will improve the accuracy of analyses that seek to quantify the role of climate change in species’ distribution and phenology changes

Strengthening confidence in climate change impact science

Aim: To assess confidence in conclusions about climate-driven biological change through time, and identify approaches for strengthening confidence scientific conclusions about ecological impacts of climate change. Location: Global. Methods: We outlined a framework for strengthening confidence in inferences drawn from biological climate impact studies through the systematic integration of prior expectations, long-term data and quantitative statistical procedures. We then developed a numerical confidence index (Cindex) and used it to evaluate current practices in 208 studies of marine climate impacts comprising 1735 biological time series. Results: Confidence scores for inferred climate impacts varied widely from 1 to 16 (very low to high confidence). Approximately 35% of analyses were not associated with clearly stated prior expectations and 65% of analyses did not test putative non-climate drivers of biological change. Among the highest-scoring studies, 91% tested prior expectations, 86% formulated expectations for alternative drivers but only 63% statistically tested them. Higher confidence scores observed in studies that did not detect a change or tracked multiple species suggest publication bias favouring impact studies that are consistent with climate change. The number of time series showing climate impacts was a poor predictor of average confidence scores for a given group, reinforcing that vote-counting methodology is not appropriate for determining overall confidence in inferences. Main conclusions: Climate impacts research is expected to attribute biological change to climate change with measurable confidence. Studies with long-term, high-resolution data, appropriate statistics and tests of alternative drivers earn higher Cindex scores, suggesting these should be given greater weight in impact assessments. Together with our proposed framework, the results of our Cindex analysis indicate how the science of detecting and attributing biological impacts to climate change can be strengthened through the use of evidence-based prior expectations and thorough statistical analyses, even when data are limited, maximizing the impact of the diverse and growing climate change ecology literature