Optimizing the use of quicklime (CaO) for sea urchin management — A lab and field study

Mass blooms of sea urchins sometimes cause kelp forest collapses that can last for decades. Quicklime has historically been used to reverse those conditions, but the efficacy of liming has varied along latitudinal and temperature gradients for reasons that are not fully understood. To evaluate the feasibility and ecological impacts of liming in a high latitude area in Northern Norway (70°N), we conducted a field pilot study in 2008–2011, a follow-up lab study in 2017, and a further field study in 2018–2019, with the latter evaluating and implementing the previous results in a site high in refuges. It was found that liming can reduce sea urchin densities sufficiently for macroalgal revegetation to occur, and that the mobile fauna species richness and abundance increased in the re-vegetated in comparison to the barren control fields. Also, the remaining sea urchins in the treated fields increased their roe content to commercial levels after 2 years. The lab experiments in 2017 indicated that the liming method is season/temperature-independent, as mortality remained at the same level irrespective of whether treatment started in the spring, when the sea temperatures were 2 °C, or in autumn when the temperatures were closer to 10 °C. The most important factor in treatment efficacy in the lab was particle size. With similar doses, the particles in the smallest size range (0–0.5 mm) caused 100% mortality, while the 0.5–2 mm and 2–4 mm fractions caused only 13% and 2% mortality respectively. In 2018–2019 we tested the fine CaO fraction (0.1–0.6 mm) and the medium fraction (0.5–2 mm) in a field experiment in areas characterized by high levels of refuges. Within 11 days, the sea urchin densities in the three fields treated with the fine lime were reduced to levels that theoretically should allow revegetation, but only in one of those fields was that potential partly realized after 1 year. The lack of effect in the two other fields was probably due to urchins protected by the substrate during treatment reappearing in sufficient numbers to prevent macroalgal regrowth, demonstrating that CaO treatment can be less effective on substrates where part of the sea urchin population hides among stones. Of the three variables held up as potential explanations for the different effects of CaO treatment in previous studies, we conclude based on our experiments that the presence of refuges and particle size were probably more important than temperature. Further improvements for larger scale treatments are discussed.publishedVersio

Adult and offspring size in the ocean over 17 orders of magnitude follows two life history strategies

Explaining variability in offspring vs. adult size among groups is a necessary step to determine the evolutionary and environmental constraints shaping variability in life history strategies. This is of particular interest for life in the ocean where a diversity of offspring development strategies is observed along with variability in physical and biological forcing factors in space and time. We compiled adult and offspring size for 407 pelagic marine species covering more than 17 orders of magnitude in body mass including Cephalopoda, Cnidaria, Crustaceans, Ctenophora, Elasmobranchii, Mammalia, Sagittoidea, and Teleost. We find marine life following one of two distinct strategies, with offspring size being either proportional to adult size (e.g., Crustaceans, Elasmobranchii, and Mammalia) or invariant with adult size (e.g., Cephalopoda, Cnidaria, Sagittoidea, Teleosts, and possibly Ctenophora). We discuss where these two strategies occur and how these patterns (along with the relative size of the offspring) may be shaped by physical and biological constraints in the organism's environment. This adaptive environment along with the evolutionary history of the different groups shape observed life history strategies and possible group-specific responses to changing environmental conditions (e.g., production and distribution)

Integrated assessment of marine biodiversity status using a prototype indicator-based assessment tool

Integrated assessment of the status of marine biodiversity is and has been problematic compared to, for example, assessments of eutrophication and contamination status, mostly as a consequence of the fact that monitoring of marine habitats, communities and species is expensive, often collected at an incorrect spatial scale and/or poorly integrated with existing marine environmental monitoring efforts. The objective of this Method Paper is to introduce and describe a simple tool for integrated assessment of biodiversity status based on the HELCOM Biodiversity Assessment Tool (BEAT), where interim biodiversity indicators are grouped by themes: broad-scale habitats, communities, and species as well as supporting non-biodiversity indicators. Further, we report the application of an initial indicator-based assessment of biodiversity status of Danish marine waters where we have tentatively classified the biodiversity status of Danish marine waters. The biodiversity status was in no areas classified as “unaffected by human activities.” In all the 22 assessment areas, the status was classified as either “moderately affected by human activities” or “significantly affected by human activities.” Spatial variations in the biodiversity status were in general related to the eutrophication status as well as fishing pressure

Osborn waves following out-of-hospital cardiac arrest:Effect of level of temperature management and risk of arrhythmia and death

Background: The Osborn or J-wave, an upright deflection of the J-point on the electrocardiogram (ECG), is often observed during severe hypothermia. A possible relation between Osborn waves (OW) and increased risk of ventricular arrhythmia has been reported. We sought to determine whether the level of targeted temperature management (TTM) following out-of-hospital cardiac arrest (OHCA) affects the prevalence of OW and to assess the associations between OW and risk of ventricular arrhythmia and death. Methods and results: The present study is part of the TTM-trial ECG-substudy (including OHCA-patients randomized to TTM at 33 °C vs. 36 °C from 24 of 36 sites). Serial 12-lead ECGs from 680 (94%) patients were analysed and stratified by OW at predefined time-points (0, 4, 28, 36, 72-h after admission). On admission, the overall prevalence of OW was 16%, increasing to 32% at target temperature, with higher prevalence in the 33 °C-group (40% vs. 23%, p < 0.0001). No difference in prevalence was found between the 33 °C- and 36 °C-groups on admission (18% vs. 14%, p =.11) or after rewarming (13% vs. 10%, p =.44). OW were not associated with increased risk of ventricular arrhythmia (Odds ratio = 0.78 (0.51–1.20), p =.26), but associated with significantly lower 180-day mortality as compared to no OW (38% vs. 52%, plog-rank = 0.001) in univariable analyses only. Conclusion: OW are frequent during TTM, particularly in patients treated with 33 °C. OW are not associated with increased risk of ventricular arrhythmia, and may be considered a benign physiological phenomenon, associated with lower mortality in univariable analyses