Kelly C. Shannon, Gillian St. John, Robin Gould, Christopher Hartzell, Hailey Matthews, Elizabeth J. Brennan, Luis M. Bolaños, Steven T. Lindley, John C. Field, Nate Mantua, Rachel Johnson, Carson Jeffres, Frederick S. Colwell, Christopher P. Suffridge
{"title":"Springtime upwelling conditions influence microbial communities and dissolved thiamin compounds in the California Current Ecosystem","authors":"Kelly C. Shannon, Gillian St. John, Robin Gould, Christopher Hartzell, Hailey Matthews, Elizabeth J. Brennan, Luis M. Bolaños, Steven T. Lindley, John C. Field, Nate Mantua, Rachel Johnson, Carson Jeffres, Frederick S. Colwell, Christopher P. Suffridge","doi":"10.1002/lno.70021","DOIUrl":"https://doi.org/10.1002/lno.70021","url":null,"abstract":"Understanding dissolved concentrations of the essential coenzyme thiamin (vitamin B<jats:sub>1</jats:sub>) can provide insights into the biological controls on highly productive upwelling systems such as the California Current Ecosystem. To connect thiamin availability with microbial communities in the California Current Ecosystem, we measured concentrations of dissolved thiamin and its biochemically related moieties (thiamin congeners) and 16S rRNA gene‐based microbial communities during the spring. We found that strong upwelling caused a depletion of dissolved thiamin precursor compounds and abiotic degradation products relative to periods of weak upwelling. Specific microbial taxa, including species of SAR11 ecotypes, <jats:italic>Candidatus</jats:italic> Nitrosopumilus, and SUP05 cluster, were also significantly enriched with strong upwelling. Our data provide evidence that alterations to microbial communities in the mixed layer that occur as a result of upwelling could constrain the availability of dissolved thiamin and its chemical congeners in the California Current Ecosystem.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"94 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2025-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143677575","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sarah L. C. Giering, Filipa Carvalho, Morten H. Iversen, Zonghua Liu, Océane Merchiers, C. Mark Moore, Michael Ockwell, Uta Passow, Alex J. Poulton, Elisa Romanelli, Thangavel Thevar, Richard Sanders
{"title":"Species‐specific diatom dynamics shape their vertical distribution and export during bloom decline","authors":"Sarah L. C. Giering, Filipa Carvalho, Morten H. Iversen, Zonghua Liu, Océane Merchiers, C. Mark Moore, Michael Ockwell, Uta Passow, Alex J. Poulton, Elisa Romanelli, Thangavel Thevar, Richard Sanders","doi":"10.1002/lno.12818","DOIUrl":"https://doi.org/10.1002/lno.12818","url":null,"abstract":"The Southern Ocean is a critical region for global biogeochemical cycles, particularly for carbon dioxide uptake and organic carbon export, partly driven by extensive phytoplankton blooms. In naturally iron‐fertilized regions of this otherwise iron‐limited ocean, these blooms are primarily driven by diatoms. Variability in bloom occurrences on spatiotemporal scales makes it challenging to track and understand a bloom's decline and associated carbon export. Moreover, species‐specific processes may be critical yet are typically not well resolved. Here, we use state‐of‐the‐art in situ imaging, producing high‐resolution vertical profiles of phytoplankton and particles, combined with water sampling, to resolve the decline of a Southern Ocean spring bloom. We observed significant vertical and temporal changes in particle and diatom composition and abundance. <jats:italic>Fragilariopsis kerguelensis</jats:italic> showed deepening abundance peaks correlating with silicic acid gradients and water density changes, while their chain lengths decreased likely due to nutrient stress and physical breakage. High downward fluxes of <jats:italic>F. kerguelensis</jats:italic> and concentrations below the mixed later suggest they were a key contributor to carbon export and transfer. Conversely, <jats:italic>Eucampia antarctica</jats:italic> exhibited a rapid decline in surface abundance with minimal vertical redistribution and low fluxes, potentially linked to changing environmental conditions. These findings highlight species‐specific responses to environmental conditions and implications for carbon processes. Measured values of the apparent photosynthetic efficiency (Fv/Fm) suggests that photosynthetically viable diatoms were a significant contributor to export and particle biomass in the upper mesopelagic zone. Our results underscore the importance of understanding individual species dynamics for oceanic carbon and nutrient cycles.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"61 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2025-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143677574","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Wave attenuation in a partially vegetated flume","authors":"Yufei Wang, Jiarui Lei","doi":"10.1002/lno.70039","DOIUrl":"https://doi.org/10.1002/lno.70039","url":null,"abstract":"Wave attenuation in partially vegetated aquatic environments remains an underexplored area of research. This study addresses this gap by conducting laboratory experiments to examine the influence of vegetation on wave dynamics. The wavelength‐to‐vegetation spacing ratio is essential to quantifying the behavior of the waves within and around vegetated areas. Laboratory experiments measure wave height variations along the longitudinal and transverse directions in areas of partial vegetation coverage. Our results indicate that, for experimental cases where vegetation patches extended only a few wavelengths in the propagation direction, when the wavelength‐to‐vegetation spacing is greater than one, attenuation across the partially vegetated flume approaches uniformity; in contrast, when the ratio is smaller than one, wave attenuation occurs predominantly within the vegetated region. This study advances our understanding of the complex interactions between waves and vegetation, providing a foundation for further engineering and ecological research.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"119 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2025-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143672477","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Karen M. Brandenburg, Julian Merder, Andrea Budiša, Anne Marie Power, Catharina J. M. Philippart, Anna M. Michalak, Tim J. van den Broek, Dedmer B. Van de Waal
{"title":"Multiple global change factors and the long‐term dynamics of harmful algal blooms in the North Sea","authors":"Karen M. Brandenburg, Julian Merder, Andrea Budiša, Anne Marie Power, Catharina J. M. Philippart, Anna M. Michalak, Tim J. van den Broek, Dedmer B. Van de Waal","doi":"10.1002/lno.70025","DOIUrl":"https://doi.org/10.1002/lno.70025","url":null,"abstract":"The North Sea has been identified as an area where the impacts of climate change and de‐eutrophication efforts are already apparent, specifically on phytoplankton communities, with shifts in biogeography, altered species composition, and increased biomass of harmful algal bloom (HAB) species. Here, we test whether environmental changes in the Dutch North Sea are associated with changes in the abundances of HAB species and if the probability of blooms has increased over the past two decades. We do so by using generalized additive and logistic regression models, respectively. Results show that <jats:italic>Phaeocystis globosa</jats:italic> and potential ASP (amnesic shellfish poisoning) and DSP (diarrhetic shellfish poisoning) toxin‐producing species have increased in abundance along the coast over the period 2000–2018, despite overall declines in total phytoplankton biomass over the same period. Conversely, the abundance of potential ASP producers and particularly <jats:italic>P. globosa</jats:italic> declined in the more central areas of the North Sea. The probability of blooms, which varied across months during the season, generally increased. Environmental factors associated with these increases in the probability of HABs included increasing sea surface temperatures (for potential ASP and DSP toxin producers), possibly related to summer stratification of the water column, and increasing total nitrogen (TN) : total phosphorus (TP) ratios (for potential ASP and DSP toxin producers and <jats:italic>P. globosa</jats:italic>) due to de‐eutrophication efforts that more effectively reduced TP than TN. Our results demonstrate how long‐term changes in HAB species abundances in the North Sea are associated with shifts in multiple global change factors that together may lead to intensified HAB development.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"27 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143653378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nadefa Adda Nekrouf, Lucia Maestre‐Carballa, Monica Lluesma‐Gomez, Francisco Martinez‐Hernandez, Manuel Martinez‐Garcia
{"title":"Annual dynamics and metagenomics of marine vesicles: One more layer of complexity in the dissolved organic fraction","authors":"Nadefa Adda Nekrouf, Lucia Maestre‐Carballa, Monica Lluesma‐Gomez, Francisco Martinez‐Hernandez, Manuel Martinez‐Garcia","doi":"10.1002/lno.70031","DOIUrl":"https://doi.org/10.1002/lno.70031","url":null,"abstract":"Despite the role of extracellular vesicles (EVs) in genetic and biogeochemical exchange in the ocean, there is a notable dearth of studies delving into the seasonal annual dynamics of EVs in uncultured microbial communities. Here, quantitative data from the oligotrophic Mediterranean Sea revealed that EVs mL<jats:sup>−1</jats:sup> ranged from 10<jats:sup>4</jats:sup> to 10<jats:sup>6</jats:sup> throughout the year and correlated with microbial abundances (correlation coefficient = 0.67). The ratio of EVs per cell ranged from 1 to 4. Vesicle metagenomics identified copiotrophic and oligotrophic prokaryotic species, such as <jats:italic>Flavobacterium</jats:italic> and <jats:italic>Pelagibacter</jats:italic>, putatively dominating the production of EVs containing DNA in the annual dataset. <jats:italic>Micromonas</jats:italic> spp. and others Mamiellophyceae emerged as the dominant eukaryotic producers of EVs containing DNA. Genes belonging to viruses were consistently identified in purified vesicles. The relative proportion of viral contigs found in the vesicle fraction (2.4–30.4%) suggested that the release of viral genomes in EVs could be more common than previously thought.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"33 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143653380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Moderate ocean alkalinity enhancement likely to have minimal effects on a habitat‐forming kelp across multiple life stages","authors":"Damon Britton, Wouter Visch, Lennart T. Bach","doi":"10.1002/lno.70029","DOIUrl":"https://doi.org/10.1002/lno.70029","url":null,"abstract":"Ocean alkalinity enhancement (OAE) is a widely considered marine CO<jats:sub>2</jats:sub> removal method. Ocean alkalinity enhancement works by converting seawater CO<jats:sub>2</jats:sub> into and by electrochemical methods or the addition of alkaline minerals. Although OAE does not require biology to remove CO<jats:sub>2</jats:sub>, the perturbations caused by OAE may affect marine organisms. Due to logistical challenges, it is likely that alkalinity additions will occur in coastal regions, yet the effects on coastal species are unknown. Along temperate coasts, kelp forests are important communities that provide habitat for numerous species. However, it is unclear how kelps will respond to OAE and whether responses differ across life stages. To address this, we conducted a laboratory culture experiment on adults of the kelp <jats:italic>Ecklonia radiata</jats:italic>. Individuals were exposed to control, +300, and +600 <jats:italic>μ</jats:italic>mol kg<jats:sup>−1</jats:sup> alkalinity additions using NaOH as an alkalinity source. Following this, spores from reproductive adults cultured under control and +600 <jats:italic>μ</jats:italic>mol kg<jats:sup>−1</jats:sup> alkalinity treatments were released into control, +300, and +600 <jats:italic>μ</jats:italic>mol kg<jats:sup>−1</jats:sup> alkalinity conditions to determine the effect on the development of new recruits. Negative effects were only evident under extreme alkalinity enhancement conditions across both life stages. Adults displayed a decline in growth rates in the +600 <jats:italic>μ</jats:italic>mol kg<jats:sup>−1</jats:sup> treatment and less recruits developed from spores released into +600 <jats:italic>μ</jats:italic>mol kg<jats:sup>−1</jats:sup> alkalinity conditions. No negative effects were detected under +300 <jats:italic>μ</jats:italic>mol kg<jats:sup>−1</jats:sup> alkalinity increases across both life stages. These findings suggest chemical OAE methods are unlikely to have substantial impacts on <jats:italic>E. radiata</jats:italic> except under extreme conditions.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"20 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143653376","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Catherine Lalande, Eun Jin Yang, Eunho Ko, Jisoo Park, Jinyoung Jung, Jeong‐Hyun Kim, Jong‐Kuk Moon, Dongseon Kim, Seok‐jin Jeon
{"title":"Sea ice breakup and nutrient supply regulate the timing and magnitude of algal export over the slopes of the Pacific Arctic region","authors":"Catherine Lalande, Eun Jin Yang, Eunho Ko, Jisoo Park, Jinyoung Jung, Jeong‐Hyun Kim, Jong‐Kuk Moon, Dongseon Kim, Seok‐jin Jeon","doi":"10.1002/lno.70032","DOIUrl":"https://doi.org/10.1002/lno.70032","url":null,"abstract":"Few in situ measurements are conducted early in the productive season in the Arctic Ocean, making it difficult to accurately assess the impact of the recent decline in sea ice cover on algal fluxes. Since 2017, time‐series sediment traps have been deployed to collect sinking particles at two sites in the Pacific Arctic region. Here, we present algal fluxes obtained in the East Siberian Sea (ESS) and in the northern Chukchi Sea (NCS) between August 2017 and November 2022. Despite interruptions in sampling, algal fluxes reflected large spatial and temporal variations in the magnitude and timing of algal blooms and export in the region. In the ESS, peak diatom fluxes > 600 million cells m<jats:sup>−2</jats:sup> d<jats:sup>−1</jats:sup> in early August 2018 reflected the occurrence of an unusually large and long‐lasting diatom bloom sustained by an episodic inflow of nutrient‐rich waters. Diatom fluxes were usually lower in the NCS than in the ESS, reaching a peak flux of > 170 million cells m<jats:sup>−2</jats:sup> d<jats:sup>−1</jats:sup> in late August 2017. As diatoms consistently contributed to the majority of algal fluxes, their rapid decrease and near absence frequently observed during July or August at both sites reflected low nutrient concentrations in the upper water column leading to a dominance of small algal cells typically retained in upper waters. Overall, whereas nutrient supply influenced the magnitude and duration of the diatom fluxes, sea ice breakup determined the timing of peak diatom export in the Pacific Arctic slope region.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"25 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143653381","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Isabelle J. Cooper, Jasmin A. Godbold, Amber L. Annett
{"title":"Macrofaunal contributions to benthic nutrient fluxes revealed by radium disequilibrium","authors":"Isabelle J. Cooper, Jasmin A. Godbold, Amber L. Annett","doi":"10.1002/lno.70033","DOIUrl":"https://doi.org/10.1002/lno.70033","url":null,"abstract":"The benthic flux of nutrients underpins marine food webs, influences conditions for life in the oceans, and contributes to climatic feedback. Estimates of these fluxes' contributions to macro‐ and micronutrient cycles are, however, highly variable, generating significant uncertainty in biogeochemical models. Traditional benthic flux methodologies have potentially significant limitations, and in geochemically framed studies, there is a notable omission of contributions from macrofaunal activity. <jats:sup>224</jats:sup>Ra/<jats:sup>228</jats:sup>Th disequilibrium is a cutting‐edge geochemical technique for quantifying benthic flux; however, its capacity to incorporate the influence of benthic fauna has not been assessed. Here we present first results using <jats:sup>224</jats:sup>Ra/<jats:sup>228</jats:sup>Th disequilibrium to examine the influence of four macrobenthic infaunal invertebrate species on the flux of macronutrients (, , , ) between the sediment and water column. Overall, estimates from <jats:sup>224</jats:sup>Ra/<jats:sup>228</jats:sup>Th disequilibrium were up to 15 times greater than those derived from commonly used methods, and both <jats:sup>224</jats:sup>Ra and nutrient fluxes differed in the presence of different macrofauna. The greatest efflux (, ) and influx (, ) occurred in the presence of the burrowing actinarian <jats:italic>Edwardsia claparedii</jats:italic>, and <jats:sup>224</jats:sup>Ra flux patterns suggested different mechanisms of influence between species. Notable variability in flux enhancement was also present between individuals of the same species, highlighting the complex relationship between biodiversity and ecosystem functioning. We conclude that <jats:sup>224</jats:sup>Ra/<jats:sup>228</jats:sup>Th disequilibrium is a powerful tool for interdisciplinary biogeochemical and ecological studies, and if applied widely enough may more holistically represent benthic flux dynamics in the natural environment than standard approaches.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"55 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143653375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kristian Spilling, Mari Vanharanta, Mariano Santoro, Cristian Villena‐Alemany, Matthias Labrenz, Hans‐Peter Grossart, Kasia Piwosz
{"title":"Picophytoplankton act as the primary consumers of excess phosphorus after the spring bloom in the eutrophic Baltic Sea","authors":"Kristian Spilling, Mari Vanharanta, Mariano Santoro, Cristian Villena‐Alemany, Matthias Labrenz, Hans‐Peter Grossart, Kasia Piwosz","doi":"10.1002/lno.70027","DOIUrl":"https://doi.org/10.1002/lno.70027","url":null,"abstract":"Eutrophication in the Baltic Sea has caused an imbalance in the inorganic nitrogen (N) to phosphorus (P) ratio, leaving excess phosphate (PO<jats:sub>4</jats:sub>) after the phytoplankton spring bloom that terminates after N depletion. Using monitoring data, we demonstrated that the PO<jats:sub>4</jats:sub> concentration has continued to increase in the outermost Gulf of Finland during past decades. We further investigated the fate of such excess PO<jats:sub>4</jats:sub> in a two‐week mesocosm (1.2 m<jats:sup>3</jats:sup>) experiment. The starting concentration of PO<jats:sub>4</jats:sub> was 0.66 <jats:italic>μ</jats:italic>M, and treatments included a non‐treated control (control), nitrate addition (N‐add; 3.6 <jats:italic>μ</jats:italic>M), glucose addition (C‐add; 36 <jats:italic>μ</jats:italic>M) and combined nitrate and glucose addition (N + C‐add). The addition of N, both in N‐add and N + C‐add treatments, stimulated nano‐ and microphytoplankton, while the picophytoplankton abundance increased after N depletion. Also, the copepod biomass was positively affected by the N addition. N<jats:sub>2</jats:sub>‐fixing cyanobacteria were present but in low abundance. Carbon addition did not enhance heterotrophic bacterial uptake of PO<jats:sub>4</jats:sub> contrary to our expectations, nor did it affect the phyto‐ or zooplankton community composition. The PO<jats:sub>4</jats:sub> concentration was reduced to ~ 0.4 <jats:italic>μ</jats:italic>M in the control and C‐add treatments and to 0.16 <jats:italic>μ</jats:italic>M in the two N‐amended treatments, with an inorganic N : P uptake ratio of 6.7. These results underscore the role of picophytoplankton in reducing the excess PO<jats:sub>4</jats:sub> pool after the spring bloom, a function traditionally ascribed to bloom‐forming filamentous cyanobacteria in the Baltic Sea.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"58 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143653379","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Salla A. Ahonen, Roger I. Jones, Jukka Seppälä, Kristiina M. Vuorio, Marja Tiirola, Anssi V. Vähätalo
{"title":"Phytoplankton absorb mainly red light in lakes with high chromophoric dissolved organic matter","authors":"Salla A. Ahonen, Roger I. Jones, Jukka Seppälä, Kristiina M. Vuorio, Marja Tiirola, Anssi V. Vähätalo","doi":"10.1002/lno.70034","DOIUrl":"https://doi.org/10.1002/lno.70034","url":null,"abstract":"The impact of chromophoric dissolved organic matter (CDOM) on the spectral underwater light field within photosynthetically active radiation (PAR), and the related responses of spectral phytoplankton light absorption are poorly documented in the mixed layer of lakes. We examined how CDOM influences the spectrum of lake optical properties, underwater light field, photons absorbed by phytoplankton, photoacclimation, and chromatic adaptation of phytoplankton in 127 boreal lakes. In lakes with increasing CDOM content, light intensity decreased steeply with depth, but mixed layer depth and mean light intensity of the mixed layer decreased only moderately. Increasing CDOM content red‐shifted the central wavelengths of lake optical properties, underwater light fields, and the photons absorbed by phytoplankton. In study lakes with increasing CDOM content, the highest light availability shifted stepwise from 580 to 650 nm and close to 700 nm. The ratio of chlorophyll <jats:italic>a</jats:italic> concentration to phytoplankton biomass decreased slightly in lakes with higher CDOM content. The absorption coefficient of phytoplankton at blue relative to red wavelengths decreased with increasing CDOM content, indicating decreased blue‐absorbing pigmentation in response to decreased availability of blue light. Surprisingly, the number of red photons (600–700 nm) absorbed by phytoplankton increased with CDOM content below the mid‐point of the euphotic zone. Over the entire water column, red light (600–700 nm) accounted for > 50% of PAR absorption by phytoplankton in 69% of the lakes. The high contribution of red photons to the absorption of PAR by phytoplankton may have photobiological consequences, which are poorly understood and require further study.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"70 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143653382","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}