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The COVID-19 lockdown reduced human mobility and led to immediate insights into how humans impact nature. Yet the strongest ecological impacts are likely to come. As we emerge from the pandemic, governments should avoid prioritizing short-term economic gains that compromise ecosystems and the services they provide humanity. Instead, the pandemic can be a pivot point for societal transformation to value longer term ecosystem and economic sustainability. [ABSTRACT FROM AUTHOR]

Ocean acidification (OA) resulting from uptake of anthropogenic CO may negatively affect coral reefs by causing decreased rates of biogenic calcification and increased rates of CaCO dissolution and bioerosion. However, in addition to the gradual decrease in seawater pH and Ω resulting from anthropogenic activities, seawater carbonate chemistry in these coastal ecosystems is also strongly influenced by the benthic metabolism which can either exacerbate or alleviate OA through net community calcification (NCC = calcification - CaCO dissolution) and net community organic carbon production (NCP = primary production − respiration). Therefore, to project OA on coral reefs, it is necessary to understand how different benthic communities modify the reef seawater carbonate chemistry. In this study, we used flow-through mesocosms to investigate the modification of seawater carbonate chemistry by benthic metabolism of five distinct reef communities [carbonate sand, crustose coralline algae (CCA), corals, fleshy algae, and a mixed community] under ambient and acidified conditions during summer and winter. The results showed that different communities had distinct influences on carbonate chemistry related to the relative importance of NCC and NCP. Sand, CCA, and corals exerted relatively small influences on seawater pH and Ω over diel cycles due to closely balanced NCC and NCP rates, whereas fleshy algae and mixed communities strongly elevated daytime pH and Ω due to high NCP rates. Interestingly, the influence on seawater pH at night was relatively small and quite similar across communities. NCC and NCP rates were not significantly affected by short-term acidification, but larger diel variability in pH was observed due to decreased seawater buffering capacity. Except for corals, increased net dissolution was observed at night for all communities under OA, partially buffering against nighttime acidification. Thus, algal-dominated areas of coral reefs and increased net CaCO dissolution may partially counteract reductions in seawater pH associated with anthropogenic OA at the local scale. [ABSTRACT FROM AUTHOR]

Coral reef ecosystems are presently undergoing decline due to anthropogenic climate change. The chief detrimental factors are increased temperature and increased pCO. The purpose of this study was to evaluate the effect of these two stressors operating independently and in unison on the biological response of common Hawaiian reef corals. Manipulative experiments were performed using five species ( Porites compressa, Pocillopora damicornis, Fungia scutaria, Montipora capitata, and Leptastrea purpurea) in a continuous-flow mesocosm system under natural sunlight conditions. Corals were grown together as a community under treatments of high temperature (2 °C above normal maximum summer temperature), high pCO (twice present-day conditions), and with both factors acting in unison. Control corals were grown under present-day pCO and at normal summer temperatures. Leptastrea purpurea proved to be an extremely hardy coral. No change in calcification or mortality occurred under treatments of high temperature, high pCO, or combined high temperature-high pCO. The remaining four species showed reduced calcification in the high-temperature treatment. Two species ( L. purpurea and M. capitata) showed no response to increased pCO. Also, high pCO ameliorated the negative effect of high temperature on the calcification rates of P. damicornis. Mortality was driven primarily by high temperature, with a negative synergistic effect in P. compressa only in the high-pCO-high-temperature treatment. Results support the observation that biological response to temperature and pCO elevation is highly species-specific, so generalizations based on response of a single species might not apply to a diverse and complex coral reef community. [ABSTRACT FROM AUTHOR]

A linkage between the condition of watersheds and adjacent nearshore coral reef communities is an assumed paradigm in the concept of integrated coastal management. However, quantitative evidence for this 'catchment to sea' or 'ridge to reef' relationship on oceanic islands is lacking and would benefit from the use of appropriate marine and terrestrial landscape indicators to quantify and evaluate ecological status on a large spatial scale. To address this need, our study compared the Hawai'i Watershed Health Index (HI-WHI) and Reef Health Index (HI-RHI) derived independently of each other over the past decade. Comparisons were made across 170 coral reef stations at 52 reef sites adjacent to 42 watersheds throughout the main Hawaiian Islands. A significant positive relationship was shown between the health of watersheds and that of adjacent reef environments when all sites and depths were considered. This relationship was strongest for sites facing in a southerly direction, but diminished for north facing coasts exposed to persistent high surf. High surf conditions along the north shore increase local wave driven currents and flush watershed-derived materials away from nearshore waters. Consequently, reefs in these locales are less vulnerable to the deposition of land derived sediments, nutrients and pollutants transported from watersheds to ocean. Use of integrated landscape health indices can be applied to improve regional-scale conservation and resource management. [ABSTRACT FROM AUTHOR]

In situ trampling occurred under experimental conditions to quantify the differences in the responses to anthropogenic trampling in four dominant species of Hawaiian corals, Porites compressa, Porites lobata, Montipora capitata, and Pocillopora meandrina. Trampling was simulated daily for a period of nine days at which time further breakage was minimal. Forty treatment colonies produced 559 fragments. Trampling was followed by an 11-month recovery period. Coral colony and fragment mortality was low. All four species were highly tolerant of inflicted damage, suggesting that some species of corals can withstand limited pulse events that allow time for recovery. Growth rates following trampling were significantly lower in the treatment groups for three of the four species. This study demonstrated that very few trampling events can produce significant changes in growth even after a long recovery period. Survivorship of fragments is clearly size- and species-dependent in M. capitata and P. compressa. Smaller fragments (<5 cm) had higher mortality than larger fragments (>5 cm). High breakage rates for M. capitata and P. compressa are consistent with the nearshore, low-energy regions they inhabit—the same environment frequented by skin divers and waders. Mechanical tests were conducted to determine tensile and compressive strengths. Pocillopora meandrina exhibited the strongest skeletal strength, followed in decreasing order by Porites lobata, Porites compressa, and Montipora capitata. The skeletal strength obtained from the experiments correlate with the wave energy present in the environments in the regions they inhabit, suggesting that structural strength of corals is an adaptive response to hydraulic stress. [ABSTRACT FROM AUTHOR]

Without drastic efforts to reduce carbon emissions and mitigate globalized stressors, tropical coral reefs are in jeopardy. Strategic conservation and management requires identification of the environmental and socioeconomic factors driving the persistence of scleractinian coral assemblages-the foundation species of coral reef ecosystems. Here, we compiled coral abundance data from 2,584 Indo-Pacific reefs to evaluate the influence of 21 climate, social and environmental drivers on the ecology of reef coral assemblages. Higher abundances of framework-building corals were typically associated with: weaker thermal disturbances and longer intervals for potential recovery; slower human population growth; reduced access by human settlements and markets; and less nearby agriculture. We therefore propose a framework of three management strategies (protect, recover or transform) by considering: (1) if reefs were above or below a proposed threshold of >10% cover of the coral taxa important for structural complexity and carbonate production; and (2) reef exposure to severe thermal stress during the 2014-2017 global coral bleaching event. Our findings can guide urgent management efforts for coral reefs, by identifying key threats across multiple scales and strategic policy priorities that might sustain a network of functioning reefs in the Indo-Pacific to avoid ecosystem collapse.