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Ocean warming is the greatest threat to coral reefs, prompting a need to accurately monitor in situ temperatures. Advancements in sensing technologies have led to a proliferation of temperature loggers being deployed globally. However, appropriate deployment of loggers–essential for measurement accuracy in an ecosystem where changes of 1ºC can cause widespread mortality–is often overlooked. For example, loggers deployed in direct sunlight are known to overestimate temperature, but the prevalence of shading loggers is unknown. Here, we survey recent literature to assess the current state of temperature logger use on coral reefs. We then performed lab and field trials on 10 models that span a range of prices and accuracies to evaluate logger performance and assess efficacies of shading techniques. Of the 329 studies we reviewed, >40% of studies deployed loggers shallower than 5 m, yet <5% reported shading loggers, revealing the potential for bias in existing datasets. In field tests, solar bias varied significantly across loggers; the most popular model suffered the largest bias of >2.5ºC, while other models were less affected by irradiance. Wrapping loggers in tape reduced temperature bias, but under high irradiance measurement error still exceeded 0.8ºC. Shading loggers under an opaque object completely eliminated solar bias. We demonstrated a strong linear relationship between in situ irradiance and temperature error and quantified irradiance thresholds for which error >0.5°C can be expected. We then modeled the temperature bias expected for the most popular logger model using in situ irradiance data, showing that errors >2ºC can exist across multiple depths. Our findings reveal pervasive underreporting of logger deployment methods in coral reef studies, highlighting the need to consider the possibility of bias when comparing studies or integrating different in situ temperature records. Future studies should strive to transparently describe deployment methods and appropriately shade loggers. [ABSTRACT FROM AUTHOR]

Ocean acidification can negatively affect a broad range of physiological processes in marine shelled molluscs. Marine bioeroding organisms could, in contrast, benefit from ocean acidification due to reduced energetic costs of bioerosion. Ocean acidification could thus exacerbate negative effects (e.g. reduced growth) of ocean acidification and shell borers on oysters. The aim of this study was to assess the impact of ocean acidification on the oyster Ostrea chilensis, the boring sponge Cliona sp., and their host-parasite relationship. We exposed three sets of organisms 1) O. chilensis, 2) Cliona sp., and 3) O. chilensis infested with Cliona sp. to pHT 8.03, 7.83, and 7.63. Reduced pH had no significant effect on calcification, respiration and clearance rate of uninfested O. chilensis. Low pH significantly reduced calcification leading to net dissolution of oyster shells at pHT 7.63 in sponge infested oysters. Net dissolution was likely caused by increased bioerosion by Cliona sp. at pHT 7.63. Additionally, declining pH and sponge infestation had a significant negative antagonistic effect (less negative than predicted additively) on clearance rate. This interaction suggests that sponge infested oysters increase clearance rates to cope with higher energy demand of increased shell repair resulting from higher boring activity of Cliona sp. at low seawater pH. O. chilensis body condition was unaffected by sponge infestation, pH, and the interaction of the two. The reduction in calcification rate suggests sponge infestation and ocean acidification together would exacerbate direct (reduced growth) and indirect (e.g., increased predation) negative effects on oyster health and survival. Our results indicate that ocean acidification by the end of the century could have severe consequences for marine molluscs with boring organisms. [ABSTRACT FROM AUTHOR]

Kelp forests are productive and biodiverse ecosystems with high ecological, cultural, and economic importance. However, the high sensitivity of kelp to water temperature means that these ecosystems are vulnerable to marine heatwaves (MHWs), especially at the equatorward edge of their range. To date, few laboratory studies have compared the effects of MHWs of different durations or intensities on kelp, and it is difficult to determine these effects from naturally occurring MHWs in the field. We exposed juvenile sporophytes of the giant kelp Macrocystis pyrifera from Wellington, Aotearoa New Zealand to simulated MHWs three or six weeks in duration, at temperatures of 18°C, 20°C, and 22°C, corresponding to 2, 4, and 6°C above local mean summer temperatures. While all MHW treatments reduced mean kelp growth rates by over 30% relative to 16°C controls, the 22°C treatments had much more severe and wide-ranging effects, including rapid blade erosion, reduced chlorophyll fluorescence, tissue bleaching, increased δ13C values, andmortality. Nonetheless, sporophytes had some ability to recover from heat stress; within the 18°C treatment, mean relative growth rates neared or exceeded those within the control treatment within three weeks after MHWs concluded. These results support the findings of previous studies which indicate that M. pyrifera sporophytes experience a key physiological tipping point around 20°C. Additionally, our findings suggest that juvenile M. pyrifera from the Wellington population could be relatively resilient toMHWs if temperatures remain at sub-lethal levels. However, if averageMHWintensities and durations continue to increase over time, survival and recruitment of juvenile kelp could be adversely affected, thus threatening the long-term persistence of giant kelp forests near the warm edge of their range in New Zealand. [ABSTRACT FROM AUTHOR]

A growing number of researchers are investigating the impact of multiple drivers on marine species and ecosystems to better understand our changing ocean (Boyd et al. [1]). Through this project, a range of resources have been developed within the Multiple Environmental Driver Design Lab for Experiments (MEDDLE) to help researchers design and carry out tractable, multiple driver experiments (Fig. [Extracted from the article]