Kai Schulz

Southern Cross University

Natural variability in seawater pH and associated carbonate chemistry parameters is in part driven by biological activities such as photosynthesis and respiration. The amplitude of these variations is expected to increase with increasing seawater carbon dioxide (CO2) concentrations in the future, because of simultaneously decreasing buffer capacity...

Anthropogenic emissions of carbon dioxide (CO2) and the ongoing accumulation in the surface ocean together with concomitantly decreasing pH and calcium carbonate saturation states have the potential to impact phytoplankton community composition and therefore biogeochemical element cycling on a global scale. Here we report on a recent mesocosm CO2 p...

Frequent upwelling of deep, cold water, rich in dissolved inorganic nutrients and carbon dioxide but low in oxygen concentrations and pH, is well documented in eastern boundary systems. As a consequence, waters in vast areas of the continental shelf can turn corrosive to the mineral aragonite, vital to a number of marine organisms. This phenomenon...

Upwelling of nutrient-rich deep waters make eastern boundary upwelling systems (EBUSs), such as the Humboldt Current system, hot spots of marine productivity. Associated settling of organic matter to depth and consecutive aerobic decomposition results in large subsurface water volumes being oxygen depleted. Under these circumstances, organic matter...

Ocean alkalinity enhancement (OAE) is a proposed marine carbon dioxide removal (mCDR) approach that has the potential for large-scale uptake of significant amounts of atmospheric carbon dioxide (CO2). Removing anthropogenic legacy CO2 will be required to stabilise global surface temperatures below the 1.5-2 •C Paris Agreement target of 2015. In thi...

Plastic pollution and ocean warming threaten crucial ecosystem processes, including detrital decomposition. We carried out a manipulative experiment using 20 outdoor raceways to test hypotheses about the influence of macroplastics (polyvinyl chloride (PVC), polyethylene terephthalate (PET), high-density polyethylene (HDPE), low-density polyethylene...

Light is critical to coral growth through endosymbiont photosynthesis but can also act with elevated temperatures to cause coral bleaching. When more light is absorbed than can be used for photosynthesis, elevated irradiance can damage symbiont photosynthetic machinery. Hence, solar-radiation management through shading has been suggested to allevia...

Ocean alkalinity enhancement (OAE) aims to transfer carbon dioxide (CO2) from the atmosphere to the ocean by increasing the capacity of seawater to store CO2. The potential effects of OAE-induced changes in seawater chemistry on marine biology must be assessed to understand if OAE, operated at a climate-relevant scale, would be environmentally sust...

Understanding the impacts that mineral grain size and seawater salinity have on magnesium hydroxide (Mg(OH)2) dissolution and secondary calcium carbonate (CaCO3) precipitation is critical for the success of ocean alkalinity enhancement. We tested Mg(OH)2 dissolution kinetics in seawater using three Mg(OH)2 grain sizes (<63, 63–180 and >180µm) at th...

Ocean alkalinity enhancement (OAE) via the enhanced weathering of alkaline minerals is a promising carbon dioxide removal (CDR) technology. Theoretically, these includes iron and steel slags, although their dissolution kinetics in seawater are unknown. Here, we conducted lab-scale experiments to assess the alkalinity generation potential and dissol...

Gigatonne-scale atmospheric carbon dioxide removal (CDR) will almost certainly be needed to supplement the emission reductions required to keep global warming between 1.5–2 °C. Ocean alkalinity enhancement (OAE) is an emerging marine CDR method with the addition of pulverised minerals to the surface ocean being one widely considered approach. A con...

Estuaries play an important role in connecting the global carbon cycle across the land-to-ocean continuum, but little is known about Australia’s contribution to global CO2 emissions. Here we present an Australia-wide assessment, based on CO2 concentrations for 47 estuaries upscaled to 971 assessed Australian estuaries. We estimate total mean (±SE)...

Rates of denitrification and associated nitrous oxide (N2O) production are expected to increase with global warming, leading to positive climate feedback. However, previous studies have not considered the combined effect of ocean acidification (OA, pCO2 ~ 900 µatm) and warming on denitrification rates and N2O production. Here we used a series of wh...

Ocean Alkalinity Enhancement (OAE) aims to transfer carbon dioxide (CO2) from the atmosphere to the ocean by increasing the capacity of seawater to store CO2. The potential effects of OAE-induced changes in seawater chemistry on marine biology must be assessed to understand if OAE, operated at a climate relevant scale, would be environmentally sust...

Understanding the impact that mineral grain size and seawater salinity have on magnesium hydroxide (Mg(OH)2) dissolution and secondary calcium carbonate (CaCO3) precipitation is critical for the success of ocean alkalinity enhancement. We tested the Mg(OH)2 dissolution kinetics in seawater using three Mg(OH)2 grain sizes (<63, 63–180 and >180 µm) a...

Ocean artificial upwelling has been suggested to boost primary production and increase harvestable resources such as fish. Yet, for this ecosystem-based approach to work, an effective energy transfer up the food web is required. Here, we studied the trophic role of microzooplankton under artificial upwelling via biomass and community composition as...

Fungi are key players in terrestrial organic matter (OM) degradation, but little is known about their role in marine environments. Here we compared the degradation of kelp (Ecklonia radiata) in mesocosms with and without fungicides over 45 days. The aim was to improve our understanding of the vital role of fungal OM degradation and remineralisation...

Gigatonne-scale atmospheric carbon dioxide removal (CDR) will almost certainly be needed to supplement the emission reductions required to keep global warming between 1.5–2 °C. Ocean alkalinity enhancement (OAE) is an emerging marine CDR method with the addition of pulverized minerals to the surface ocean being one widely considered approach. A con...

Accurate measurements of seawater carbonate chemistry are crucial for marine carbon cycle research. Certified reference materials (CRMs) are typically analyzed alongside samples to correct measurements for calibration drift. However, the COVID‐19 pandemic led to a limited access to CRMs. In response to this shortage, we prepared and monitored in‐ho...

Ocean alkalinity enhancement (OAE) is a proposed marine carbon dioxide removal (mCDR) approach that has the potential for large-scale uptake of significant amounts of atmospheric carbon dioxide (CO2). Removing anthropogenic legacy CO2 will be required to stabalise global surface temperatures below the 1.5–2 °C Paris Agreement target of 2015. In thi...

Filter feeding bivalves are useful bioindicators for the detection of biologically available pollutants. We investigated trace metals, metalloids, and pesticides in leaf oyster (Isognomon ephippium) soft tissue and shells and compared them to sediment in five estuaries in northern New South Wales, Australia. Concentrations of Pb, Cr, Mn, Ni, Fe and...

“ They call it pollution, we call it life ” is an infamous quote which ignores many facts about why carbon dioxide (CO 2 ) poses a significant problem for the ocean. But before we get to this, let’s start at the beginning. All organisms on Earth require a particular set of elements for growth. In the case of plants, these elements are needed to syn...

For more than 150 years, our understanding of solid-phase mineral formation from dissolved constituent ions in aqueous environments has been dominated by classical nucleation theory (CNT). However, an alternative paradigm known as non-classical nucleation theory (NCNT), characterized by the existence of thermodynamically stable and highly hydrated...

The coronavirus pandemic has caused a surge in the use of both disposable and re-usable mask pollution globally. It is important to understand the potential impact this influx of novel pollution has on key ecological processes, such as detrital dynamics. We aimed to understand the impact mask pollution has on the decomposition of a common coastal s...

The interactions established between marine microbes, namely phytoplankton–bacteria, are key to the balance of organic matter export to depth and recycling in the surface ocean. Still, their role in the response of phytoplankton to rising CO2 concentrations is poorly understood. Here, we show that the response of the cosmopolitan Emiliania huxleyi...

Ocean alkalinity enhancement (OAE) is a proposed method to counteract climate change by increasing the alkalinity of the surface ocean and thus the chemical storage capacity of seawater for atmospheric CO2. The impact of OAE on marine ecosystems, including phytoplankton communities which make up the base of the marine food web, is largely unknown....

Isognomon ephippium, commonly known as the leaf oyster, is one of the largest intertidal bivalves known to form shellfish reefs. Leaf oysters are native to tropical and subtropical Australia as well as many other regions of the world, however, very little is known about their biology and ecology. This study investigated the ability of leaf oysters...

Understanding how warming and OA will affect denitrification, and the associated production of N2O, is essential to assess the nitrogen removal capacity of the coastal zone, and the positive warming feedback loop from N2O production in a high-CO2 climate. We estimate that OA may offset the warming increase in estuarine sediment denitrification and...

Climate change is expected to alter the intensity and frequency of upwelling in high productive coastal regions, thus impacting nutrient fluxes, primary productivity and consequently carbon cycling. However, it is unknown how these changes will impact the planktonic (phytoplankton and bacteria) community structure, which affects community respirati...

Ocean alkalinity enhancement (OAE) is a method that can remove carbon dioxide (CO2) from the atmosphere and counteract ocean acidification through the dissolution of alkaline minerals. Currently, critical knowledge gaps exist regarding the dissolution of different minerals suitable for OAE in natural seawater. Of particular importance is to underst...

Marine macroalgae are a key primary producer in coastal ecosystems, but are often overlooked in blue carbon inventories. Large quantities of macroalgal detritus deposit on beaches, but the fate of wrack carbon (C) is little understood. If most of the wrack carbon is respired back to CO2, there would be no net carbon sequestration. However, if most...

Earth’s Radiation Budget is partly dictated by the fragile and complex balance between biogenic volatile organic compounds (BVOCs) and greenhouse gases (GHGs), which have the potential to impose cooling or warming once emitted to the atmosphere. Whilst methane (CH4) is strictly associated with global warming due to its solar-radiation absorbing pro...

Leaf oysters (Isognomon ephippium) are large intertidal bivalves that form shellfish reefs. They have a patchy and restricted distribution in estuaries in northern New South Wales, Australia, where the water quality is impacted by a range of anthropogenic stressors from coastal agriculture, urbanisation, industry and recreational activities, along...

Ocean alkalinity enhancement (OAE) is a proposed method to counteract climate change by increasing the alkalinity of the surface ocean and thus the chemical storage capacity of seawater for atmospheric CO2. The impact of OAE on marine ecosystems, including phytoplankton communities which make up the base of the marine food web, are largely unknown....

Oxygen minimum zones (OMZs) are characterized by enhanced carbon dioxide (CO2) levels and low pH and are being further acidified by uptake of anthropogenic atmospheric CO2. With ongoing intensification and expansion of OMZs due to global warming, carbonate chemistry conditions may become more variable and extreme, particularly in the eastern bounda...

Nitrogen that has been recycled in the benthos supports high rates of primary and secondary production in estuaries. However, little is known about the effect of future climate on benthic nitrogen recycling and assimilation. An ex situ core incubation was used to assess the impact of combinations of warming (8°C range) and ocean acidification (OA)...

Primary production in the Southern Ocean is dominated by diatom‐rich phytoplankton assemblages, whose individual physiological characteristics and community composition are strongly shaped by the environment, yet knowledge on how diatoms allocate cellular energy in response to ocean acidification (OA) is limited. Understanding such changes in alloc...

Ocean Alkalinity Enhancement (OAE) has been proposed as a method to remove carbon dioxide (CO2) from the atmosphere and to counteract ocean acidification. It involves the dissolution of alkaline minerals such as quick lime, CaO, and hydrated lime, Ca(OH)2. However, a critical knowledge gap exists regarding their dissolution in natural seawater. Par...

Estuarine sediments make an important contribution to the global carbon cycle, but we do not know how this will change under a future climate, which is expected to have lower pH oceans and frequent high-temperature days. Six combinations of warming and partial pressures of CO 2 (pCO 2) were chosen to investigate the combined and individual effects...

The growth rate hypothesis (GRH) posits an increase in ribosomal ribonucleic acid (RNA) content, and therefore cellular phosphorus (P), with increasing growth rate. There is evidence that the GRH may not apply to phy-toplankton under all conditions. Here, we experimentally controlled four conditions (light, temperature, pH, and CO 2) to alter the g...

Oxygen minimum zones (OMZs) are characterized by enhanced carbon dioxide (CO2) levels and low pH and are being further acidified by uptake of anthropogenic atmospheric CO2. With ongoing intensification and expansion of OMZs due to global warming, carbonate chemistry conditions may become more variable and extreme, particularly in the Eastern Bounda...

Reef-forming leaf oysters, Isognomon ephippium, are large (>10 cm) but flat intertidal bivalves. They are found in many estuaries in Australia but their specific habitat requirements and tolerance to poor water quality remain unknown. To address this knowledge gap, four rivers in northern New South Wales, Australia were selected for the study. Our...

Plain Language Summary Positive rates of net ecosystem calcification and net ecosystem production are regarded as fundamental to the healthy functioning of coral reef ecosystems. In particular, positive ecosystem calcification is required to maintain the structural complexity that sustains many of the ecosystem functions of coral reefs. While most...

Relative to their surface area, estuaries make a disproportionately large contribution of dissolved organic carbon (DOC) to the global carbon cycle, but it is unknown how this will change under a future climate. As such, the response of DOC fluxes from microbially dominated unvegetated sediments to individual and combined future climate stressors o...

Upwelling of nutrient-rich deep waters make Eastern Boundary upwelling systems (EBUS), such as the Humboldt Current System, hotspots of marine productivity. Associated settling of organic matter to depth and consecutive aerobic de composition results in large sub-surface water volumes being oxygen-depleted. Under these circumstances organic matter...

Ocean acidification (OA) and organic matter (OM) enrichment (due to coastal eutrophication) could act in concert to shift coral reef carbonate sediments from a present state of net calcification to a future state of net dissolution, but no studies have examined the combined effect of these stressors on sediment metabolism and dissolution. This stud...

Large-scale dinoflagellate blooms have appeared in recent decades in the Taiwan Strait, Southeast China. To study spatial variability of phytoplankton community composition, physical and chemical environmental drivers in surface seawater of the Taiwan Strait, we conducted cruises in May and July 2019. Cell numbers of dinoflagellates were significan...

This review investigates the current state of knowledge of the genus Isognomon with respect to different aspects of its biology, including taxonomy, morphology, ecology, life history, physiology, stress tolerance, diseases, contamination from environmental pollutants and their potential for use as bio-indicators. A total of 126 publications on the...

Eastern boundary upwelling systems (EBUS) are among the most productive marine ecosystems on Earth. The production of organic material is fueled by upwelling of nutrient-rich deep waters and high incident light at the sea surface. However, biotic and abiotic factors can modify surface production and related biogeochemical processes. Determining the...

Estuaries make a disproportionately large contribution of dissolved organic carbon (DOC) to the global carbon cycle, but it is unknown how this will change under a future climate. As such, the response of DOC fluxes from microbially dominated unvegetated sediments to individual and combined future climate stressors of warming (from Δ−3 °C to Δ+5 °C...

Plastic pollution and ocean change have mostly been assessed separately, missing potential interactions that either enhance or reduce future impacts on ecosystem processes. Here, we used manipulative experiments with outdoor mesocosms to test hypotheses about the interactive effects of plastic pollution, ocean warming and acidification on macrophyt...

High-latitude oceans have been identified as particularly vulnerable to ocean acidification if anthropogenic CO2 emissions continue. Marine microbes are an essential part of the marine food web and are a critical link in biogeochemical processes in the ocean, such as the cycling of nutrients and carbon. Despite this, the response of Antarctic marin...

Eastern boundary upwelling systems (EBUS) are among the most productive marine ecosystems on Earth. The high productivity in surface waters is facilitated by upwelling of nutrient-rich deep waters, with high light availability enabling fast phytoplankton growth and nutrient utilization. However, there are numerous biotic and abiotic factors modifyi...

Shallow, permeable calcium carbonate (CaCO3) sediments make up a large proportion of the benthic cover on coral reefs and account for a large fraction of the standing stock of CaCO3. There have been a number of laboratory, mesocosm, and in situ studies examining shallow sediment metabolism and dissolution, but none of these have considered seasonal...

Diatoms, large bloom-forming marine microorganisms, build frustules out of silicate, which ballasts the cells and aids their export to the deep ocean. This unique physiology forges an important link between the marine silicon and carbon cycles. However, the effect of ocean acidification on the silicification of diatoms is unclear. Here we show that...

High-latitude oceans have been identified as particularly vulnerable to ocean acidification if anthropogenic CO2 emissions continue. Marine microbes are an essential part of the marine food web and are a critical link in biogeochemical processes in the ocean, such as the cycling of nutrients and carbon. Despite this, the response of Antarctic marin...

Severe coral bleaching events have affected the GBR causing massive losses of hard coral cover. Here we use flow respirometry approaches to assess coral reef net ecosystem calcification (NEC) and net ecosystem production following the 2015/2016 bleaching event at Lizard Island in the northern Great Barrier Reef, a heavily impacted area. Previous st...

Mangrove soil carbon stocks are known to decrease following forest loss due to respiration and enhanced soil CO2 emissions. However, changes in carbon outwelling to the coastal ocean due to mangrove forest disturbance have not been considered. In December 2015, an extremely large mangrove dieback event (~7000 hectares, spanning 1000 km of coastline...

Ocean acidification (OA) can induce shifts in plankton community composition, with coccolithophores being mostly negatively impacted. This is likely to change particulate inorganic and organic carbon (PIC and POC, respectively) production, with impacts on the biological carbon pump. Hence, assessing and, most importantly, understanding species‐spec...