Kunshan Gao

• PhD
• Professor at Xiamen University

Abiotic photochemistry and microbial degradation are the two main removal processes of marine dissolved organic matter (DOM). However, the combined and repeated effects of irradiation and biodegradation on DOM remains poorly resolved due to their complex interactions. To disentangle the effects of abiotic photochemistry from photobiology, we altern...

CO 2 concentration mechanisms (CCMs) are important in maintaining the high efficiency of photosynthesis of marine algae. Aquatic photoautotrophs have two types of CCMs: biophysical CCMs, based on the conversion of inorganic carbon, and biochemical CCMs, based on the formation of C 4 acid intermediates. However, the contribution of biophysical and b...

Many phytoplankton produce methane, a potent greenhouse gas. However, little is known about the relationship between their methane production and photosynthesis, which drives carbon sequestration in the oceans. Here, by ruling out the possibility of classical methanogenesis, we show that the bloom-forming marine microalga Emiliania huxleyi released...

The marine microalga Emiliania huxleyi is widely distributed in the surface oceans and is prone to infection by coccolithoviruses that can terminate its blooms. However, little is known about how global change factors like solar UV radiation (UVR) and ocean warming affect the host‐virus interaction. We grew the microalga at 2 temperature levels wit...

The diazotrophic cyanobacterium Trichodesmium has been recognized as a potentially significant contributor to aerobic methane generation via several mechanisms including the utilization of methylphophonate (MPn) as a source of phosphorus. Currently, there is no information about how environmental factors regulate methane production by Trichodesmium...

Respiratory activity in the oceans is declining due to the expansion of hypoxic zones and progressive deoxygenation, posing threats to marine organisms along with impacts of concurrent ocean acidification. Therefore, understanding the combined impacts of reduced pO2 and elevated pCO2 on marine primary producers is of considerable significance. Here...

Phytoplankton produces methane (CH 4 ), a potent greenhouse gas. Little is known about the relationship between their CH 4 production and photosynthesis, the predominant biological pathway of CO 2 sequestration in the ocean. We show that CH 4 released by the widespread, bloom-forming marine microalga Emiliania huxleyi grown under different light le...

The heterotrophic dinoflagellate Oxyrrhis marina is an essential microzooplankton in coastal waters, linking the energy transfer from phytoplankton to higher trophic levels. It is of general significance to investigate how it responds and acclimates to ocean acidification (OA), especially under varied availabilities of food. Here, O. marina was exp...

Ultraviolet (UV) A radiation (315–400 nm) is the predominant component of solar UV radiation that reaches the Earth’s surface. However, the underlying mechanisms of the positive effects of UV-A on photosynthetic organisms have not yet been elucidated. In this study, we investigated the effects of UV-A radiation on the growth, photosynthetic ability...

Blooms of microalgal red tides and macroalgae (e.g., green and golden tides caused by Ulva and Sargassum) have caused widespread problems around China in recent years, but there is uncertainty around what triggers these blooms and how they interact. Here, we use 30 years of monitoring data to help answer these questions, focusing on the four main s...

The effects of ocean warming on phytoplankton have been extensively studied, but little has been documented on responses of differently sized diatoms to changes of temperature over wide ranges. We grew three diatom species, Thalassiosira pseudonana , Thalassiosira weissflogii , and Thalassiosira punctigera , with cell volumes of 199, 1805, and 13,5...

Understanding the potential impacts of internal waves on phytoplankton communities in oligotrophic oceans remains an important research challenge. In this study, we elucidated the impact of internal waves on phytoplankton communities through a comprehensive 154‐hr time‐series of observations in the South China Sea (SCS). We identified distinctive v...

Under global change scenarios, the sea surface temperature is increasing steadily along with other changes to oceanic environments. Consequently, marine diatoms are influenced by multiple ocean global change drivers. We hypothesized that temperature rise mediates the responses of polar and temperate diatoms to UV radiation (UVR) to different extent...

Subtropical gyres cover 26%–29% of the world's surface ocean and are conventionally regarded as ocean deserts due to their permanent stratification, depleted surface nutrients, and low biological productivity. Despite tremendous advances over the past three decades, particularly through the Hawaii Ocean Time‐series and the Bermuda Atlantic Time‐ser...

Ocean warming is suggested to exert profound effects on phytoplankton physiology and growth. Here, we investigated how the coccolithophore Emiliania huxleyi (BOF 92, a non-calcifying strain) responded to changes in temperature in short- and long-term thermal treatments. The specific growth rate after 10 days of acclimation increased gradually with...

Abstract We conducted a mesocosm experiment to examine how ocean acidification (OA) affects communities of prokaryotes and eukaryotes growing on single‐use drinking bottles in subtropical eutrophic waters of the East China Sea. Based on 16S rDNA gene sequencing, simulated high CO2 significantly altered the prokaryotic community, with the relative a...

The marine picocyanobacterium Synechococcus accounts for a major fraction of the primary production across the global oceans. However, knowledge of the responses of Synechococcus to changing pCO2 and light levels has been scarcely documented. Hence, we grew Synechococcus sp. CB0101 at two CO2 concentrations (ambient CO2 AC:410 μatm; high CO2 HC:100...

Planète bleue, photosynthèse rouge et verte décrit les mécanismes qui permettent aux organismes photosynthétiques aquatiques de contribuer pour moitié à la productivité primaire nette, d’atténuer les changements climatiques en séquestrant le dioxyde de carbone et, par la production d’oxygène, d’avoir transformé l’atmosphère anoxique originelle de l...

Aquatic ecosystems are responsible for about 50% of global productivity. They mitigate climate change by taking up a substantial fraction of anthropogenically emitted CO2 and sink part of it into the deep ocean. Productivity is controlled by a number of environmental factors, such as water temperature, ocean acidification, nutrient availability, de...

Effects of changed levels of dissolved O2 and CO2 on marine primary producers are of general concern with respect to ecological effects of ongoing ocean deoxygenation and acidification as well as upwelled seawaters. We investigated the response of the diazotroph Trichodesmium erythraeum IMS 101 after it had acclimated to lowered pO2 (~60 μM O2) and...

Although the marine N2‐fixers Trichodesmium spp. are affected by increasing pCO2 and by ultraviolet radiation (UVR) in their habitats, little is known on their potential responses to future ocean acidification in the presence of UVR. We grew Trichodesmium at two pCO2 levels (410 and 1000 μatm) under natural sunlight, documented the filament length,...

The blooms of coccolithophores are usually terminated by their viruses. However, little has been documented on the interplay between the host with virus under different environmental conditions. We investigated the relationship of Emiliania huxleyi (BOF92) and its virus (EhV99B1) after the coccolithophorid had acclimated to different levels of sali...

Nutrients associated with internal waves are known to perturb phytoplankton communities in oligotrophic oceans, but details of the relevant processes and mechanisms are unclear. Here we report insights about the impacts of internal waves on the phytoplankton community based on 154-hour time-series of observations in an oligotrophic basin of the Sou...

Unlabelled: To examine the synergetic effects of ocean acidification (OA) and light intensity on the photosynthetic performance of marine diatoms, the marine centric diatom Thalassiosira weissflogii was cultured under ambient low CO2 (LC, 390 μatm) and elevated high CO2 (HC, 1000 μatm) levels under low-light (LL, 60 μmol m-2 s-1) or high-light (HL...

Although high CO2 and warming could act interactively on marine phytoplankton, little is known about the molecular basis for this interaction on an evolutionary scale. Here we explored the adaptation to high CO2 in combination with warming in a model marine diatom Phaeodactylum tricornutum. Whole-genome re-sequencing identifies, in comparison to po...

[This corrects the article DOI: 10.3389/fphys.2022.838001.].

Seawater acidification (SA) has been documented to either inhibit, enhance, or result in no effect on marine primary productivity (PP). In order to examine the effects of SA in changing environments, we investigated the influences of SA (a decrease of 0.4 pHtotal units with corresponding CO2 concentrations in the range of 22.0–39.7 µM) on PP throug...

Increasing atmospheric CO 2 concentration due to human activities is responsible for global warming and ocean warming, the latter enhancing stratification and shoaling of the upper mixed layer. Marine primary producers account for about half of global photosynthetic carbon fixation. Global change affects both marine and freshwater ecosystems. Howev...

Traditional methods using sealed bottles to determine the grazing rates by secondary producers neglect chemical changes induced by biological activities during the incubation, giving rise to instable levels of nutrients, pH, pCO2, pO2 and other chemicals along with changing microalgal cell concentrations and grazers’ metabolism. Here, we used dialy...

The atmospheric concentration of CO2 is steadily increasing and causing climate change. To achieve the Paris 1.5 or 2°C target, negative emission technologies must be deployed in addition to reducing carbon emissions. The ocean is a large carbon sink but the potential of marine primary producers to contribute to carbon neutrality remains unclear. H...

Bisphenol A (BPA) is a synthetic organic compound used as raw material in many industrial products, particularly epoxy resins and polycarbonate plastics. Due to its extensive applications, increasing contamination in the environment and adverse effects on living organisms, BPA has been regarded as a pollutant of emerging concern. In aquatic environ...

Among efforts to explore ways to achieve carbon neutrality globally or regionally, photosynthetic carbon sequestration by algae has been identified as having immense potential. Algae play a crucial role in providing the base of aquatic ecosystems, driving important biogeochemical cycles in oceans and freshwaters and, in so doing, act as a critical...

Phytoplankton are exposed to different concentrations of nutrients in different waters along with changing light levels during diurnal and seasonal cycles. We grew the coccolithophorid Gephyrocapsa oceanica semi-continuously at different nitrate levels under indoor low and outdoor high light conditions, and found that reduced nitrate availability s...

The rise of atmospheric pCO2 has created a number of problems for marine ecosystem. In this study, we initially quantified the effects of elevated pCO2 on the group-specific mortality of phytoplankton in a natural community based on the results of mesocosm experiments. Diatoms dominated the phytoplankton community, and the concentration of chloroph...

Many marine organisms are exposed to decreasing O2 levels due to warming-induced expansion of hypoxic zones and ocean deoxygenation (DeO2). Nevertheless, effects of DeO2 on phytoplankton have been neglected due to technical bottlenecks on examining O2 effects on O2-producing organisms. Here we show that lowered O2 levels increased primary productiv...

Future CO2-induced ocean acidification (OA) has been documented to either inhibit or enhance or result in no effect on marine primary productivity (PP). In order to examine effects of OA under multiple drivers, we investigated the influences of OA (a decrease of 0.4 pHtotal units with corresponding CO2 concentrations ranged 22.0–39.7 µM) on PP thro...

Experimental cultures of both microalgae and macroalgae are commonly carried out by phycologists or environmental biologists to look into morphological, physiological, and molecular responses to aquatic environmental changes. However, the species of inorganic carbon in algae cultures is often altered by algal photosynthetic CO 2 removal and/or bica...

Ocean acidification (OA) represents a threat to marine organisms and ecosystems. However, OA rarely exists in isolation but occurs concomitantly with other stressors such as ultraviolet radiation (UVR), whose effects have been neglected in oceanographical observations. Here, we perform a quantitative meta-analysis based on 373 published experimenta...

To investigate effects of UV radiation (UVR, 280–400 nm) on coccolithophorids under nutrient-limited conditions, we grew Gephyrocapsa oceanica to determine its resilience to consecutive daily short-term exposures to +UVR (irradiances >295 nm) under a range of nitrate availabilities (100, 24, 12, 6 and 3 μM). +UVR alone significantly hampered the gr...

In the warm, oligotrophic oceans, phytoplankton frequently experience high light exposure and must compete for a potentially limited nutrient supply. Additionally, the light regimes are dynamic in view of the diel solar cycle, weather conditions, and depth. Dealing with these challenges is critical to their survival. Here, we explored, using active...

Although the individual effects of ocean acidification (OA), warming, solar UV radiation, deoxygenation and heavy metal pollution on marine producers are well-studied, their interactive effects are still unclear, strongly limiting our ability to project the ecological consequences of ocean climate changes. This chapter aims to provide an overview o...

While intertidal macroalgae are exposed to drastic changes in solar photosynthetically active radiation (PAR) and ultraviolet radiation (UVR) during a diel cycle, and to ocean acidification (OA) associated with increasing CO2 levels, little is known about their photosynthetic performance under the combined influences of these drivers. In this work,...

Eutrophic coastal regions are highly productive and greatly influenced by human activities. Primary production supporting the coastal ecosystems is supposed to be affected by progressive ocean acidification driven by increasing CO2 emissions. In order to investigate the effects of high pCO2 (HC) on eutrophic plankton community structure and ecologi...

The toxicity of heavy metals to coastal organisms can be modulated by changes in pH due to progressive ocean acidification (OA). We investigated the combined impacts of copper and OA on different stages of the green macroalga Ulva linza, which is widely distributed in coastal waters, by growing the alga under the addition of Cu (control, 0.125 (med...

Experimentally elevated pCO2 and the associated pH drop are known to differentially affect many aspects of the physiology of diatoms under different environmental conditions or in different regions. However, contrasting responses to elevated pCO2 in the dark and light periods of a diel cycle have not been documented. By growing the model diatom Pha...

Understanding the environmental conditions that trigger Pseudo-nitzschia bloom formation and domoic acid (DA) production is critical as the frequency and severity of these toxic blooms increases in the face of anthropogenic change. However, predicting the formation of these harmful blooms in a future ocean remains a challenge. Previous studies have...

"Carbon neutrality" is the only way to deal with climate change, and ocean "negative emissions" is an important way to achieve "carbon neutrality". The basic roadmap of the annex programs related to ocean "negative emissions" proposed in this article, including the land-sea overall plan to predict the increase in sinks, the increase in sinks caused...

The carbonate chemistry in coastal waters is more variable compared with that of open oceans, both in magnitude and time scale of its fluctuations. However, knowledge of the responses of coastal phytoplankton to dynamic changes in pH/pCO2 has been scarcely documented. Hence, we investigated the physiological performance of a coastal isolate of the...

The impacts of micro-and nanoplastics (MNPs) on aquatic animals have been intensively studied; however, the extent and magnitude of potential effects of MNPs on aquatic primary producers are poorly understood. In this study, we quantitatively analyzed the published literature to examine the impacts of MNPs on growth, photo-synthesis, pigments, and...

The diatom Skeletonema costatum is cosmopolitan and forms algal blooms in coastal waters, being exposed to varying levels of solar UV radiation (UVR) and reduced levels of carbon dioxide (CO2). While reduced CO2 availability is known to enhance CO2 concentrating mechanisms (CCMs) in this diatom and others, little is known on the effects of UV on mi...

Synechococcus is a major contributor to the primary production in tropic and subtropical oceans worldwide. Responses of this picophytoplankton to changing light and CO2 levels is of general concern to understand its ecophysiology in the context of ocean global changes. We grew Synechococcus sp. (WH7803), originally isolated from subtropic North Atl...

Diatom responses to ocean acidification have been documented with variable and controversial results. We grew the coastal diatom Thalassiosira weissflogii under 410 (LC, pH 8.13) vs 1000 μatm (HC, pH 7.83) pCO2 and at different levels of light (80, 140, 220 μmol photons m⁻² s⁻¹), and found that light level alters physiological responses to OA. CO2...

Photophysiological responses of phytoplankton to changing multiple environmental drivers are essential in understanding and predicting ecological consequences of ocean climate changes. In this study, we investigated the combined effects of two CO2 levels (410 and 925 μatm) and five light intensities (80 to 480 μmol photons m⁻² s⁻¹) on cellular pigm...

Macro‐nutrient limitation and increased solar exposure coincide with ocean warming‐enhanced stratification, with consequences for phytoplankton within the upper mixing layer. In this study, we grew a diatom, Thalassiosira punctigera, under nitrogen limited and replete conditions for more than 14 generations and investigated both the biochemical com...

Carbon, nitrogen, and phosphate are three macroelements of organisms. These elements are core components of organic matter and biological macromolecules. For this reason, interest in the measurement of particulate organic carbon (POC), nitrogen (PON), and phosphorus (POP) is becoming a hot research topic. In this section, the measurement methods fo...

Action spectrum is a method used to evaluate the effects of different wavelengths of light on a specific process. In the photosynthetic reaction, sunlight can be used both to drive photosynthetic carbon fixation (mainly visible light) or to inhibit it (mainly ultraviolet radiation). Therefore, action spectrum can be used to measure both the promoti...

Biochemical inhibitors are usually used to study the mechanisms or pathways of cellular metabolism; these inhibitors are able to bind to a specific site of enzymes or ion channels, and interrupt a certain reaction in which enzymes are involved, while there are no direct effects to other biochemical reactions. This chapter will introduce typical inh...

Calcification and silicification are two major kinds of biomineralization on the Earth. Coccolithophore and diatom are major calcifier and silicifier in the oceans, respectively. Thus, these marine phytoplankton play important roles in global cycle of carbon, silicon, and calcium. In this section, the standard measurement methods for calcification...

For many studies using microalgae as research subjects, culture methodology is a key part that influences results. There are many advantages to using continuous or semicontinuous cultures compared to batch cultures. Continuous cultures can maintain a stable physical and chemical environment where cells grow. Semicontinuous cultures are easier to ca...

Different culture methods to grow microalgae could lead to different physical (light) and chemical environments in culture vessels. Photosynthetic carbon sequestration by the algae in light and their respiratory CO2 release in darkness, can affect stability of carbonate systems (pH, various forms of inorganic carbon, total alkalinity) in culture sy...

The rate of photosynthesis is measured mainly by changes in dissolved oxygen or inorganic carbon. The relationship between photosynthetic carbon fixation or oxygen evolution rate and inorganic carbon concentration is usually determined by changing the concentration of inorganic carbon in the reaction cuvette, while the photosynthetic rate under dif...

Membrane-inlet mass spectrometer (MIMS) is used to simultaneously monitor changes of the concentrations of gases with different molecular weights in the solution. It can be used to measure the gas exchanges during photosynthesis and respiration of algae and other aquatic primary producers.

Solar radiation that drives the photosynthetic progress of phytoplankton is one of the key environmental factors. Therefore, the accurate measurement of light intensity and dose is vital for the researches of marine ecology and phytoplankton physiology. This section thus describes in detail the methods for measurements and conversions of visible an...

Benthic algae and animals are generally in stirred or flowing seawater due to water currents and waves. It is hard to measure their photosynthetic or respiratory rates in a small closed container due to their large size and bottle effects. Seawater flow-through method can avoid bottle effects and be applied to large size organisms or benthic commun...

Biochemical compounds such as phenolics and UV-absorbing compounds are an important group of natural products involved in responses to different kinds of biotic and abiotic stress in high plants, macroalgae, and microalgae. Here, we review the advances of the responses of these compounds in aquatic primary producers to environmental changes, and di...

Chlorophyll fluorescence techniques, apart from the application in laboratory measurements of photosynthesis, are widely used in field studies on marine primary production, referring to biomass of phytoplankton, photochemical reaction, photosynthetic carbon fixation, pathway of energy utilization and dissipation. This section introduces the use of...

This book presents methods for investigating the effects of aquatic environmental changes on organisms and the mechanisms involved. It focuses mainly on photosynthetic organisms, but also provides methods for virus, zooplankton and other animal studies. Also including a comprehensive overview of the current methods in the fields of aquatic physiolo...

Effects of ocean acidification and warming on marine primary producers can be modulated by other environmental factors, such as levels of nutrients and light. Here, we investigated the interactive effects of five oceanic environmental drivers (CO2, temperature, light, dissolved inorganic nitrogen and phosphate) on the growth rate, particulate organ...

Marine macroalgae, the main primary producers in coastal waters, play important roles in the fishery industry and global carbon cycles. With progressive ocean global changes, however, they are increasingly exposed to enhanced levels of multiple environmental drivers, such as ocean acidification, warming, heatwaves, UV radiation and deoxygenation. W...

We investigated the individual as well as combined performance of photosystem II and photosystem I in the ubiquitous green macroalga Ulva lactuca under diurnally changing light conditions using a dual pulse-amplitude modulated chlorophyll fluorescence technique. Along with rising levels of sunlight, the effective and maximal quantum yields of photo...

The commercially important red macroalga Pyropia (formerly Porphyra) yezoensis is, in its natural intertidal environment, subjected to high levels of both photosynthetically active and ultraviolet radiation (PAR and UVR, respectively). In the present work, we investigated the effects of a plausibly increased global CO 2 concentration on quantum yie...

Dissolution of anthropogenic CO2 into the oceans results in ocean acidification (OA), altering marine chemistry with consequences for primary, secondary, and tertiary food web producers. Here we examine how OA could affect the food quality of primary producers and subsequent trophic transfer to second and tertiary producers. Changes in food quality...

Most marine algae preferentially assimilate CO 2 via the Calvin-Benson Cycle (C 3) and cat-alyze HCO 3 − dehydration via carbonic anhydrase (CA) as a CO 2-compensatory mechanism, but certain species utilize the Hatch-Slack Cycle (C 4) to enhance photosynthesis. The occurrence and importance of the C 4 pathway remains uncertain, however. Here, we de...

While seawater acidification induced by elevated CO2 is known to impact coccolithophores, the effects in combination with decreased salinity caused by sea ice melting and/or hydrological events have not been documented. Here we show the combined effects of seawater acidification and reduced salinity on growth, photosynthesis and calcification of Em...

Differential responses of diatoms, an important group of marine primary producers to ocean acidification, have been well documented. However, studies so far are based on limited representative strains from key species. Investigation of strain level responses will help us better understand the contrasting discrepancy in diatom responses to ocean aci...

Effects of ocean acidification and warming on marine primary producers can be modulated by other environmental factors, such as levels of nutrients and light. Here, we investigated the interactive effects of five oceanic environmental drivers (CO2, temperature, light, dissolved inorganic nitrogen and phosphate) on growth rate, particulate organic (...

The oceans are taking up over one million tons of fossil CO2 per hour, resulting in increased pCO2 and declining pH, leading to ocean acidification (OA). At the same time, accumulation of CO2 and other greenhouse gases is causing ocean warming, which enhances stratification with thinned upper mixed layers, exposing planktonic organisms to increasin...

Marine photosynthesis contributes approximately half of the global primary productivity. Ocean climate changes, such as increasing dissolved CO2 in seawater and consequently declining pH (known as ocean acidification, OA), may alter marine photosynthetic performance. There are numerous studies on the effects of OA on photosynthetic organisms, but c...

Marine diatoms are ubiquitously distributed in both coastal and open oceans, playing an important role in global primary productivity. In coastal waters, they are exposed to various pollutants in addition to multiple environmental stressors. Here, we show the pennate diatom Nitzschia sp. isolated from the East China Sea decreased its photosynthetic...

Macroalgal blooms and marine microplastics (MPs), as global challenges for oceans, are both showing a rising trend. However, none is known regarding the interaction of these two important issues. The Yellow Sea suffers the world’s largest green tides and severe MPs pollution as well. Therefore, we tracked the trapping of MPs by drifting Ulva prolif...

The rising global demand for energy and the decreasing stocks of fossil fuels, combined with environmental problems associated with greenhouse gas emissions, are driving research and development for alternative and renewable sources of energy. Algae have been gaining increasing attention as a potential source of bio-renewable energy because they gr...

Phytoplankton in the upper oceans are exposed to changing light levels due to mixing, diurnal solar cycles and weather conditions. Consequently, effects of ocean acidification are superimposed upon responses to variable light levels. We therefore grew a model diatom Thalassiosira pseudonana under either constant or variable light but at the same da...

Trichodesmium species, as a group of photosynthetic N2 fixers (diazotrophs), play an important role in the marine biogeochemical cycles of nitrogen and carbon, especially in oligotrophic waters. How ongoing ocean warming may interact with light availability to affect Trichodesmium is not yet clear. We grew Trichodesmiumerythraeum IMS 101 at three t...

Continuous accumulation of fossil CO2 in the atmosphere and increasingly dissolved CO2 in seawater leads to ocean acidification (OA), which is known to affect phytoplankton physiology directly and/or indirectly. Since increasing attention has been paid to the effects of OA under the influences of multiple drivers, in this study, we investigated eff...

Ultraviolet‐B radiation is known to harm most photosynthetic organisms with the exception of several studies of photosynthetic eukaryotes in which UV‐B showed positive effects. In this study, we investigated the effect of acclimation to low UV‐B radiation on growth and photosynthesis of the cyanobacterium Nostoc sphaeroides. Exposure to 0.08 W m−2...

As a group of photosynthetic N2 fixers (diazotrophs), Trichodesmium species play an especially important role in the marine biogeochemical cycles of nitrogen and carbon, especially in oligotrophic waters. How ongoing ocean warming may interact with light availability to affect Trichodesmiumis not yet clear. We grew Trichodesmium erythraeum IMS 101...

Increased stratification and mixed layer shoaling of the surface ocean resulting from warming can lead to exposure of marine dinitrogen (N2)‐fixing cyanobacteria to higher levels of inhibitory ultraviolet (UV) radiation. These same processes also reduce vertically advected supplies of the potentially limiting nutrient phosphorus (P) to N2 fixers. I...