Limnology and Oceanography最新文献

{"title":"Microplastics may reduce the efficiency of the biological carbon pump by decreasing the settling velocity and carbon content of marine snow","authors":"Cordelia Roberts,&nbsp;Clara M. Flintrop,&nbsp;Alexander Khachikyan,&nbsp;Jana Milucka,&nbsp;Colin B. Munn,&nbsp;Morten H. Iversen","doi":"10.1002/lno.12615","DOIUrl":"10.1002/lno.12615","url":null,"abstract":"<p>Plastics are pervasive in marine ecosystems and ubiquitous in both shallow and deep oceans. Microfibers, among other microplastics, accumulate in deep-sea sediments at concentrations up to four orders of magnitude higher than in surface waters. This is at odds with the fact that most microfibers are positively buoyant; therefore, it is hypothesized that settling aggregates are vectors for the downward transport of microfibers in the ocean. However, little is known about the impact of microfibers on carbon export. We formed diatom aggregates with differing concentrations of microfibers using roller tanks and observed that microfiber addition stimulated aggregate formation, but decreased their structural cohesion and caused them to break apart more readily, resulting in smaller average sizes. The incorporation of positively buoyant microfibers into settling aggregates reduced their size-specific sinking velocities proportional to the microfiber concentration. Slower sinking may extend aggregate retention time in the upper ocean, thereby increasing the time available for organic matter remineralization in the upper water column. Here, we show that at concentrations of 10⁵ microfibers per cubic meter, microfiber incorporation into settling marine aggregates decreases potential export flux by 8–45%. Microfibers accumulating at such high concentrations, for example, in Arctic sea ice, may, therefore, be substantially reducing the efficiency of the biological carbon pump relative to the pre-plastic era.</p>","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"69 9","pages":"1918-1928"},"PeriodicalIF":3.8,"publicationDate":"2024-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/lno.12615","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142085226","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Causal feedback loops modify lake chlorophyll a–nutrient relationships over two decades of nutrient reductions and climate warming","authors":"Hui Fu,&nbsp;Korhan Özkan,&nbsp;Liselotte Sander Johansson,&nbsp;Martin Søndergaard,&nbsp;Torben Linding Lauridsen,&nbsp;Guixiang Yuan,&nbsp;Erik Jeppesen","doi":"10.1002/lno.12667","DOIUrl":"10.1002/lno.12667","url":null,"abstract":"<p>Understanding how the causal feedback between phytoplankton and environmental drivers controlling the chlorophyll <i>a</i> (Chl <i>a</i>, as a proxy of phytoplankton biomass)–nutrient relationships are modulated under different ecosystem conditions is a major challenge in aquatic ecology. Using an empirical dynamic model (convergent cross mapping) on a 20-yr dataset on 20 Danish lakes, we quantified hypothesized causal feedback networks for each lake and related them to lake system properties (e.g., mean water depth, nutrient concentrations and extent of reduction, climate warming) vs. the Chl <i>a</i>–nutrient relationship (estimated from generalized least square models). The results showed prevalent causal feedback across the studied lakes, which demonstrated clear patterns for the tested ecosystem variations. Weaker causal feedbacks were found in deeper lakes and lakes with larger warming trends, while stronger causal feedbacks appeared in lakes experiencing greater reductions of TP (total phosphorus) and TN (total nitrogen). Moreover, these causal feedbacks showed a strong and positive coupled pattern. Most of the causal feedbacks worked as enhancement loops, which promote the sensitivity of phytoplankton to TP, not least in shallow lakes with a high TP reduction, and as regulatory loops, which force a shift in the Chl <i>a</i>–TN relationship from a more negative slope in lakes experiencing a high nutrient reduction and weak warming to a positive slope in lakes with low nutrient reduction and stronger warming. Our findings suggest a mechanistic explanation of how internal feedbacks regulate the Chl <i>a</i>–nutrient relationships across a broad gradient of nutrient reductions, climate warming, and lake morphologies.</p>","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"69 10","pages":"2294-2306"},"PeriodicalIF":3.8,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142050606","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":"Transport and mixing observed in a pond: Description of wind-forced transport processes and quantification of mixing rates","authors":"Stephen M. Henderson,&nbsp;Jeffrey R. Nielson,&nbsp;Sandra R. Mayne,&nbsp;Caren S. Goldberg,&nbsp;Jeffrey A. Manning","doi":"10.1002/lno.12658","DOIUrl":"10.1002/lno.12658","url":null,"abstract":"<p>Ponds are characterized by high biodiversity, intense biogeochemical cycling, and susceptibility to anthropogenic impacts. Yet few studies have quantified the water velocities responsible for vertical mixing or lateral transport in ponds. We used high-resolution observations of velocity to examine mixing and transport during summer in a 50-m-long, 2.7-m-deep temperate pond. Many observed transport and mixing processes resembled those found in larger stratified lakes. A surface mixed layer was observed, whose depth ranged between ~ 1 m at night and &lt; 0.3 m during the day. Turbulence was usually sufficient to vertically mix the surface layer in 4–12 min, but no turbulence was observed in the hypolimnion. Persistent (2.5-h-averaged) currents usually flowed downwind near the surface and returned upwind near the mixed layer base. Surface currents were proportional to windspeed, with root-mean-squared speed of <span></span><math>\u0000 <mrow>\u0000 <mn>8</mn>\u0000 <mo>×</mo>\u0000 <msup>\u0000 <mn>10</mn>\u0000 <mrow>\u0000 <mo>−</mo>\u0000 <mn>3</mn>\u0000 </mrow>\u0000 </msup>\u0000 <mspace></mspace>\u0000 <mi>m</mi>\u0000 <mspace></mspace>\u0000 <msup>\u0000 <mi>s</mi>\u0000 <mrow>\u0000 <mo>−</mo>\u0000 <mn>1</mn>\u0000 </mrow>\u0000 </msup>\u0000 </mrow></math> (persistent hypolimnion currents were much weaker). Superposed on persistent currents were 30- to 100-min-period fluctuations resulting from internal seiches. These fluctuations were comparable in magnitude to more persistent currents in the mixed layer and dominated in the hypolimnion. Seiches did not advect particles far across the pond, but did contribute to production of mixed layer turbulence. Seiches also contributed to shear dispersion, which was sufficient to mix near-surface tracers across the pond in 2–4 d. Theory suggests that hypolimnion bottom boundary layers were laminar during the downslope phase of seiche motion, but became turbulent during the upslope phase as near-bed water flows created unstable stratification.</p>","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"69 9","pages":"2180-2192"},"PeriodicalIF":3.8,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/lno.12658","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142050631","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"In situ observations of zooplankton show changes in abundance and swimming speed in response to hypoxia and acidification","authors":"Amy C. Wyeth,&nbsp;Daniel Grünbaum,&nbsp;Julie E. Keister,&nbsp;Deana Crouser,&nbsp;Paul Roberts","doi":"10.1002/lno.12668","DOIUrl":"10.1002/lno.12668","url":null,"abstract":"<p>Zooplankton exhibit diverse swimming behaviors to reposition themselves in the water column, feed, find mates, and avoid predation. Environmental stressors that modify behavior can have cascading effects on population distributions and predator–prey interactions. Understanding zooplankton population dynamics is challenging, largely because traditional methods for quantifying zooplankton distributions are costly, limited in scope, and require extended analysis by trained analysts. We developed a novel methodology that combined remotely deployed camera systems, machine learning-based identification of zooplankton, and video-based tracking technology to quantify copepod and amphipod in situ swimming behavior in Hood Canal, WA, USA, a seasonally hypoxic and acidified fjord. Behavioral analysis showed copepods of all sizes swam on average 24% slower in stressful (hypoxic and acidified) waters relative to non-stressful waters. Copepods exhibited less frequent escape responses in stressful waters, with a 68% decrease in the amount of time spent “jumping” for copepods 1–2 mm in length. Interestingly, abundances of small copepods increased in stressful waters, with 56% more 1–2 mm long copepods in stressful vs. non-stressful conditions. In contrast, amphipods' average “darting” speeds did not differ between environmental conditions, but the abundance of amphipods significantly decreased in stressful waters relative to non-stressful waters, suggesting avoidance of stressful conditions. Changes in swimming behavior are informative metrics in understanding ecosystem impacts of environmental stress because swimming speed has individual, population, and community-level implications. Our results suggest that, among copepods, in situ behaviors may be useful proxies in monitoring the impacts of climate change on coastal ecosystems.</p>","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"69 10","pages":"2307-2317"},"PeriodicalIF":3.8,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/lno.12668","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142045594","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Calcification increases carbon supply, photosynthesis, and growth in a globally distributed coccolithophore","authors":"Austin R. Grubb,&nbsp;Christopher T. Johns,&nbsp;Matthew G. Hayden,&nbsp;Adam V. Subhas,&nbsp;Kimberlee Thamatrakoln,&nbsp;Kay D. Bidle","doi":"10.1002/lno.12656","DOIUrl":"10.1002/lno.12656","url":null,"abstract":"<p>Coccolithophores fix organic carbon and produce calcite plates (coccoliths) that ballast organic matter and facilitate carbon export. Photosynthesis consumes carbon dioxide, while calcification produces it, raising questions about whether coccolithophores are a net sink or source of carbon. We characterized the physiology of calcified and noncalcified (“naked”) phenotypes of <i>Emiliania huxleyi</i> (CCMP374) and investigated the relationship between calcification and photosynthesis across a gradient of light (25–2000 <i>μ</i>mol photons m⁻² s⁻¹) spanning the euphotic zone. Growth and photophysiological parameters increased with light until reaching a mid-light (150 <i>μ</i>mol photons m⁻² s⁻¹) maximum for both phenotypes. Calcified cells were characterized by enhanced photophysiology and less photoinhibition. Further, enhanced bicarbonate transport in calcified cells led to higher rates of particulate organic carbon fixation and growth compared to naked cells at mid-light to high light (150–2000 <i>μ</i>mol photons m⁻² s⁻¹). Coccolith production was similarly high at mid and high light, but the rate of coccolith shedding was &gt;3-fold lower at high-light (1.2 vs. 0.35 coccoliths cell⁻¹ h⁻¹). The cellular mechanims(s) of this differential shedding remain unknown and underly light-related controls on coccosphere maintenance. Our data suggest coccoliths shade cells at high light and that enhanced bicarbonate transport associated with calcification increases internal carbon supplies available for organic carbon fixation.</p>","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"69 9","pages":"2152-2166"},"PeriodicalIF":3.8,"publicationDate":"2024-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/lno.12656","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142022021","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Issue Information & Members","authors":"","doi":"10.1002/lno.12665","DOIUrl":"https://doi.org/10.1002/lno.12665","url":null,"abstract":"","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"69 8","pages":"iv"},"PeriodicalIF":3.8,"publicationDate":"2024-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/lno.12665","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141994198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Issue Information & TOC","authors":"","doi":"10.1002/lno.12664","DOIUrl":"https://doi.org/10.1002/lno.12664","url":null,"abstract":"","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"69 8","pages":"iii"},"PeriodicalIF":3.8,"publicationDate":"2024-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/lno.12664","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141994197","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Issue Information & Masthead","authors":"","doi":"10.1002/lno.12662","DOIUrl":"https://doi.org/10.1002/lno.12662","url":null,"abstract":"","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"69 8","pages":"i"},"PeriodicalIF":3.8,"publicationDate":"2024-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/lno.12662","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141994231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Issue Information & Copyright","authors":"","doi":"10.1002/lno.12663","DOIUrl":"https://doi.org/10.1002/lno.12663","url":null,"abstract":"","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"69 8","pages":"ii"},"PeriodicalIF":3.8,"publicationDate":"2024-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/lno.12663","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141994232","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Parasite transmission stage abundance varies in lakes over time and space","authors":"Elizabeth S. Davenport,&nbsp;Marcin K. Dziuba,&nbsp;Logan E. Jacobson,&nbsp;Siobhan K. Calhoun,&nbsp;Kira J. Monell,&nbsp;Meghan A. Duffy","doi":"10.1002/lno.12657","DOIUrl":"10.1002/lno.12657","url":null,"abstract":"<p>Environmentally transmitted parasites produce transmission stages that can remain viable and infective for extended periods of time in the environment where susceptible hosts may encounter them. Although many parasites have this mode of transmission, the abundance and distribution of environmental transmission stages have largely been overlooked, especially in aquatic habitats. Without empirical data to characterize spatial and temporal dynamics of parasite transmission stages in the environment, we might make incorrect assumptions about host–parasite contact rates. For aquatic environments, seasonal habitat structure driven by thermal stratification has been hypothesized to affect the patchiness of transmission stages within the water column, leading to uneven exposure risk to hosts. In this study, we quantified transmission stage concentrations of five common parasites of <i>Daphnia</i> spp. and <i>Ceriodaphnia dubia</i> at every meter of the water column at the deep basin of six lakes in southeastern Michigan every 2 weeks from June to November 2021. We found that transmission stage concentration varied by orders of magnitude over time and with depth. We investigated several possible drivers of these spatial and temporal patterns. For instance, our results suggest that greater mixing depth decreased transmission stage vertical patchiness within the water column of lakes with lower Fee's <i>p</i> values. However, horizontal spore patchiness across a lake was not correlated with the nearshore–offshore gradient of our study lakes. Overall, the results of our study show that parasite transmission stage concentrations have spatial and temporal dynamics that could affect disease dynamics within highly structured aquatic environments.</p>","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"69 9","pages":"2167-2179"},"PeriodicalIF":3.8,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/lno.12657","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141986340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}