The responses of brown macroalgae to environmental change from local to global scales: direct versus ecologically mediated effects

In many temperate regions, brown macroalgae fulfil essential ecosystem services such as the provision of structure, the fixation of nutrients and carbon, and the production of biomass and oxygen. Their populations in many regions around the globe have declined and/or spatially shifted in recent decades. In this review we highlight the potential global and regional drives of these changes, describe the status of regionally particularly important brown macroalgal species, and describe the capacity of interactions among abiotic and biotic factors to amplify or buffer environmental pressure on brown macroalgae. We conclude with a consideration of possible management and restoration measures

Ocean acidification and ammonium enrichment interact to stimulate a short-term spike in growth rate of a bloom forming macroalga

IntroductionThe coastal macroalgal genus, Ulva, is found worldwide and is considered a nuisance algal genus due to its propensity for forming vast blooms. The response of Ulva to ocean acidification (OA) is of concern, particularly with nutrient enrichment, as these combined drivers may enhance algal blooms because of increased availability of dissolved inorganic resources.MethodsWe determined how a suite of physiological parameters were affected by OA and ammonium (NH4+) enrichment in 22-day laboratory experiments to gain a mechanistic understanding of growth, nutrient assimilation, and photosynthetic processes. We predicted how physiological parameters change across a range of pCO2 and NH4+ scenarios to ascertain bloom potential under future climate change regimes.ResultsDuring the first five days of growth, there was a positive synergy between pCO2 and NH4+ enrichment, which could accelerate initiation of an Ulva bloom. After day 5, growth rates declined overall and there was no effect of pCO2, NH4+, nor their interaction. pCO2 and NH4+ acted synergistically to increase NO3- uptake rates, which may have contributed to increased growth in the first five days. Under the saturating photosynthetically active radiation (PAR) used in this experiment (500 μmol photon m-2 s-1), maximum photosynthetic rates were negatively affected by increased pCO2, which could be due to increased sensitivity to light when high CO2 reduces energy requirements for inorganic carbon acquisition. Activity of CCMs decreased under high pCO2 and high NH4+ conditions indicating that nutrients play a role in alleviating photodamage and regulating CCMs under high-light intensities.DiscussionThis study demonstrates that OA could play a role in initiating or enhancing Ulva blooms in a eutrophic environment and highlights the need for understanding the potential interactions among light, OA, and nutrient enrichment in regulating photosynthetic processes

Warming indirectly simplifies food webs through effects on apex predators.

Warming alters ecosystems through direct physiological effects on organisms and indirect effects via biotic interactions, but their relative impacts in the wild are unknown due to the difficulty in warming natural environments. Here we bridge this gap by embedding manipulative field experiments within a natural stream temperature gradient to test whether warming and apex fish predators have interactive effects on freshwater ecosystems. Fish exerted cascading effects on algal production and microbial decomposition via both green and brown pathways in the food web, but only under warming. Neither temperature nor the presence of fish altered food web structure alone, but connectance and mean trophic level declined as consumer species were lost when both drivers acted together. A mechanistic model indicates that this temperature-induced trophic cascade is determined primarily by altered interactions, which cautions against extrapolating the impacts of warming from reductionist approaches that do not consider the wider food web

Co-designing health service evaluation tools that foreground first nation worldviews for better mental health and wellbeing outcomes

It is critical that health service evaluation frameworks include Aboriginal people and their cultural worldviews from design to implementation. During a large participatory action research study, Elders, service leaders and Aboriginal and non-Aboriginal researchers co-designed evaluation tools to test the efficacy of a previously co-designed engagement framework. Through a series of co-design workshops, tools were built using innovative collaborative processes that foregrounded Aboriginal worldviews. The workshops resulted in the development of a three-way survey that records the service experiences related to cultural safety from the perspective of Aboriginal clients, their carer/s, and the service staff with whom they work. The surveys centralise the role of relationships in client-service interactions, which strongly reflect their design from an Aboriginal worldview. This paper provides new insights into the reciprocal benefits of engaging community Elders and service leaders to work together to develop new and more meaningful ways of servicing Aboriginal families. Foregrounding relationships in service evaluations reinstates the value of human connection and people-centred engagement in service delivery which are central to rebuilding historically fractured relationships between mainstream services and Aboriginal communities. This benefits not only Aboriginal communities, but also other marginalised populations expanding the remit of mainstream services to be accessed by many.MichaelWright, Aunty Doris Getta, Aunty Oriel Green, Uncle Charles Kickett, Aunty Helen Kickett ... et al

Experimental results of Plocamium cartilagineum growth and biomass as a function of pCO2 and temperature (Seaweed OA Resilience project)

Dataset: Plocamium growth and biomassExperimental results of Plocamium cartilagineum growth and biomass as a function of pCO2 and temperature. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/726452NSF Division of Ocean Sciences (NSF OCE) OCE-131619

Rates of photosynthesis and respiration by Ulva exposed to different average and variability of pCO2 (Seaweed OA Resilience project)

Dataset: Ulva: Photosynthesis and respirationThis dataset includes rates of photosynthesis and respiration by Ulva during culture experiments grown at 15 degrees C under various pCO2 levels, during May through July 2015. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/732625NSF Division of Ocean Sciences (NSF OCE) OCE-131619

Carbonate chemistry over a time-course in pH drift experiments with Plocamium growth collected at Catalina Island, 2014-2015 (Seaweed OA Resilience project)

Dataset: Plocamium: pH driftCarbonate chemistry over a time-course in pH drift experiments with Plocamium growth collected at Catalina Island, 2014-2015. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/726480NSF Division of Ocean Sciences (NSF OCE) OCE-131619

Predictions of photosynthesis and carbon use for diffusive uptake under light, temperature and pCO2 using a productivity model, 2014-2015 (Seaweed OA Resilience project)

Dataset: Productivity model CO2 diffusionThis dataset represents calculations from a model of photosynthesis by diffusive uptake of only CO2 given expected abundance of carbonate chemistry parameters in ocean water of known temperature salinity and depth. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/731256NSF Division of Ocean Sciences (NSF OCE) OCE-131619