Interest in red coralline algae is increasing due to their projected sensitivity to ocean acidification and their utility as palaeoenvironmental proxies. Thus, it is crucial to obtain a thorough understanding of their basic photosynthetic characteristics and appropriate techniques for use in both laboratory and in situ studies. This study provides fluorescence methodology and data for the ecologically important red coralline alga Lithothamnion glaciale using pulse amplitude modulation (PAM) fluorometry. Lithothamnion glaciale was sufficiently dark-acclimated for in situ work following 10 s of quasi-darkness, attaining 95–98% of the maximum photochemical efficiency (F v/F m). Rapid light curves conducted in situ and in the laboratory determined a low light adaptation, with a saturation intensity of 4.45–54.6 μmol photons m-2 s-1. Intra-thallus heterogeneity was observed between branch tips and bases (i.e., within the thallus) using a custom-made 2 mm fibre optic probe (the heterogeneity could not be detected using the standard 5 mm probe). Branch bases were lower light acclimated than the tips, with higher maximum effective quantum yield (F q′/F m′max) and lower non-photochemical quenching. Samples measured in May were higher light acclimated than in March, which suggests a degree of seasonal acclimation. Light history and photon irradiance levels were thus found to significantly affect the photosynthetic characteristics of L. glaciale.

The prevalence of disease-driven mass mortality events is increasing, but our understanding of spatial variation in their magnitude, timing and triggers are often poorly resolved. Here, we use a novel range-wide dataset comprised 48 810 surveys to quantify how sea star wasting disease affected Pycnopodia helianthoides , the sunflower sea star, across its range from Baja California, Mexico to the Aleutian Islands, USA. We found that the outbreak occurred more rapidly, killed a greater percentage of the population and left fewer survivors in the southern half of the species's range. Pycnopodia now appears to be functionally extinct (greater than 99.2% declines) from Baja California, Mexico to Cape Flattery, Washington, USA and exhibited severe declines (greater than 87.8%) from the Salish Sea to the Gulf of Alaska. The importance of temperature in predicting Pycnopodia distribution rose more than fourfold after the outbreak, suggesting latitudinal variation in outbreak severity may stem from an interaction between disease severity and warmer waters. We found no evidence of population recovery in the years since the outbreak. Natural recovery in the southern half of the range is unlikely over the short term. Thus, assisted recovery will probably be required to restore the functional role of this predator on ecologically relevant time scales.

Nutrient provisioning by animals can be a major driver of primary productivity in ecosystems. Animal‐mediated nutrient sources are particularly important in nutrient‐poor systems such as coral reefs. However, aggregations of mobile animals might lead to temporal and spatial variability in local nutrient availability, which is not well understood. In this study, we quantified how patterns of fish movement and abundance influence the stability of nitrogen provisioning on Bahamian coral reefs. We empirically measured and modeled nitrogen excretion estimates for 16 coral reef fish communities and combined these measurements with fish abundance and behavioral observations to compare reef nutrient budgets on diel, monthly, and annual time scales. Diel reef nitrogen provisioning by fishes varied greatly, with diurnal rates being on average four times greater than nocturnal rates. Diurnal rates were highly variable among reefs and were driven primarily by migratory grunts (Haemulidae) resting over reefs during the day but foraging off reefs at night. At the reef scale, overall nitrogen excretion rates were correlated with grunt abundance; however, grunt abundance could not be predicted by any reef physical characteristics. Within‐reef grunt excretion rates changed little across a 4‐month period but varied significantly over two years, indicating that nutrient supply on a patch reef is not stable over long periods of time. Quantifying how nutrient provisioning on patch reefs is linked to fish activity and movement patterns and how provisioning varies on different spatial and temporal scales is important for understanding overall patterns of primary productivity on reefs.

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