A systematic review and meta-analysis of the direct effects of nutrients on corals

Chronic exposure of coral reefs to elevated nutrient conditions can modify the performance of the coral holobiont and shift the competitive interactions of reef organisms. Many studies have nowquantified the links between nutrients and coral performance, but fewhave translated these studies to directly address coastal water quality standards. To address this management need, we conducted a systematic review of peer-reviewed studies, public reports, and gray literature that examined the impacts of dissolved inorganic nitrogen (DIN: nitrate, nitrite, and ammonium) and dissolved inorganic phosphorus (DIP: phosphate) on scleractinian corals. The systematic review resulted in 47 studies with comparable data on coral holobiont responses to nutrients: symbiont density, chlorophyll α (chl-α) concentration, photosynthesis, photosynthetic efficiency, growth, calcification, adult survival, juvenile survival, and fertilization. Mixed-effects meta-regression meta-analyses were used to determine the magnitude of the positive or negative effects of DIN and DIP on coral responses. Zooxanthellae density (DIN & DIP), chl-α concentration (DIN), photosynthetic rate (DIN), and growth (DIP) all exhibited positive responses to nutrient addition; maximum quantum yield (DIP), growth (DIN), larval survival (DIN), and fertilization (DIN) exhibited negative responses. In lieu of developing specific thresholds for the management of nutrients as a stressor on coral reefs, we highlight important inflection points in the magnitude and direction of the effects of inorganic nutrients and identify trends among coral responses. The responses of corals to nutrients are complex, warranting conservative guidelines for elevated nutrient concentrations on coral reefs

Examining variations in functional homogeneity in herbivorous coral reef fishes in Pacific Islands experiencing a range of human impacts

Habitat loss from human impacts can lead to functional homogenization, whereby natural communities become less diverse. Herbivorous coral reef fishes display varying specialization and unique functional roles among closely related taxa, making homogenization relevant to ecosystem function. To explore whether the functional homogeneity of herbivore assemblages correlate with human impacts, we combined an index of diet specialization and a functional trait matrix with fish abundance data for > 3000 sites across the Pacific that encompass intact to degraded coral reefs. We determined the relative abundance of specialized species and the functional dissimilarity in an assemblage. Assemblage composition varied between islands, regions, and human population densities, with generalist species such as Acanthurus nigrofuscus dominating in highly populated locations. Spatial patterns and variability in the relationship between herbivorous reef fish assemblages and human impacts showed local and indirect effects. Despite broad variability, herbivore diversity decreased with human impacts among populated islands, consistent with the hypothesis that human impacts can lead to functional homogenization of coral reef fish communities

Global trends and biases in biodiversity conservation research

Efforts to conserve biodiversity have been hampered by long-standing biases, including a disproportionate focus on particular taxa and ecosystems with minimal attention to underlying genetic diversity. We assessed whether these biases have persisted over the past four decades by analyzing trends in 17,502 research articles published in four top conservation-focused journals. Overall, we found that historical biases in conservation biology research remain entrenched. Despite increasing numbers of conservation articles published each decade from 1980 to 2020, research effort has increasingly focused on the same suite of taxa. Surprisingly, some of the most-studied species in these conservation articles had low conservation risk, including several domesticated animals. Animals and terrestrial ecosystems are consistently over-represented while plants, fungi, and freshwater ecosystems remain under-represented. Strategically funding investigations of understudied species and ecosystems will ensure more effective conservation effort across multiple levels of biodiversity, alleviate impediments to biodiversity targets, and ultimately prevent further extinctions. [Display omitted] •Biases in conservation research have not changed over time•Conservation research increasingly focuses on the same suite of species•Conservation status of a species does not seem to predict research attention•Targeted funding of understudied systems is necessary to even out research imbalance While efforts to conserve biodiversity are increasing, research and conservation efforts are unequally allocated across different scales of biodiversity, with within-species diversity receiving the least overall attention. One potential solution is to realign funding priorities to promote efforts across different scales, from genetic to species to ecosystem. With limited funding, prioritization approaches seek to maximize impact by returning to ongoing conservation efforts or focusing on high-profile species. However, these approaches reinforce biases against more equitable allocation because a lack of knowledge about understudied groups can be seen as detrimental to conservation success and prohibitively expensive. This study shows that these biases in conservation research are long standing and still ongoing, which will ultimately lead to an uneven loss of biodiversity. Deliberate funding and targeted efforts are needed to investigate both understudied species and ecosystems. Conservation biology research seems biased toward popular species and ecosystems, with seemingly little attention paid to within-species (genetic) diversity. By looking through thousands of conservation-focused research articles, we found that these biases have been notably consistent over the last four decades. We saw that some of the most-studied species have low conservation risk, and some are domesticated animals. Animals and terrestrial ecosystems are consistently over-represented while plants, fungi, and freshwater ecosystems remain under-represented